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From Wikipedia, the free encyclopedia
For other uses, see Plastic (disambiguation).
"Age of Plastics" redirects here. For the album by The Buggles, see The Age of

Household items made of various types of plastic
IUPAC definition
Generic term used in the case of polymeric material that may contain other
to improve performance and/or reduce costs.
Note 1: The use of this term instead of polymer is a source of confusion and thus
not recommended.
Note 2: This term is used in polymer engineering for materials often compounded
can be processed by flow.[1]
Plastic is a material consisting of any of a wide range of synthetic or semisynthetic organics that are malleable and can bemolded into solid objects of
diverse shapes. Plastics are typically organic polymers of high molecular mass,
but they often contain other substances. They are usually synthetic, most
commonly derived from petrochemicals, but many are partially natural.
Plasticity is the general property of all materials that are able to irreversibly
deform without breaking, but this occurs to such a degree with this class of
moldable polymers that their name is an emphasis on this ability.
Due to their relatively low cost, ease of manufacture, versatility, and
imperviousness to water, plastics are used in an enormous and expanding range
of products, from paper clips to spaceships. They have already displaced many
traditional materials, such
as wood, stone, horn and bone, leather, paper, metal, glass, and ceramic, in
most of their former uses. In developed countries, about a third of plastic is used
in packaging and another third in buildings such as piping used

inplumbing or vinyl siding.[3] Other uses include automobiles (up to 20%
plastic[3]), furniture, and toys.[3] In the developing world, the ratios may be
different - for example, reportedly 42% of India's consumption is used in
packaging.[3] Plastics have many uses in the medical field as well, to include
polymer implants, however the field of plastic surgery is not named for use of
plastic material, but rather the more generic meaning of the word plasticity in
regards to the reshaping of flesh.
The world's first fully synthetic plastic was bakelite, invented in New York in 1907
by Leo Baekeland[4] who coined the term 'plastics'.[5] Many chemists contributed
to the materials scienceof plastics, including Nobel laureate Hermann
Staudinger who has been called "the father ofpolymer chemistry" and Herman
Mark, known as "the father of polymer physics".[6] The success and dominance of
plastics starting in the early 20th century led to environmental concerns
regarding its slow decomposition rate after being discarded as trash due to its
composition of very large molecules. Toward the end of the century, one
approach to this problem was met with wide efforts toward recycling.

1 Etymology

2 Common plastics and uses

3 Special purpose plastics

4 History

5 Composition


5.1 Fillers


5.2 Plasticizers


5.3 Colorants

6 Classification

6.1 Thermoplastics and thermosetting polymers


6.2 Other classifications
6.2.1 Biodegradability

6.2.2 Natural vs synthetic

6.2.3 Crystalline vs amorphous

7 Ebonite

7.1 Bakelite

8 Representative polymers

8.1 Polystyrene


8.2 Polyvinyl chloride


8.3 Nylon


8.4 Rubber


8.5 Synthetic rubber

9 Properties of plastics

9.1 UL Standards


9.2 ISO

10 Toxicity

10.1 Bisphenol A

11 Environmental effects

11.1 Climate change


11.2 Production of plastics


11.3 Incineration of plastics


11.4 Pyrolytic disposal


11.5 Recycling

12 See also

13 References

14 External links

The word plastic is derived from the Greek πλαστικός (plastikos) meaning
"capable of being shaped or molded", from πλαστός (plastos) meaning "molded".
It refers to their malleability, or plasticity during manufacture, that allows
them to be cast, pressed, or extruded into a variety of shapes—such
as films, fibers, plates, tubes, bottles, boxes, and much more.
The common word plastic should not be confused with the technical
adjective plastic, which is applied to any material which undergoes a permanent
change of shape (plastic deformation) when strained beyond a certain
point. Aluminum which is stamped or forged, for instance, exhibits plasticity in
this sense, but is not plastic in the common sense; in contrast, in their finished
forms, some plastics will break before deforming and therefore are not plastic in
the technical sense.
Common plastics and uses

A chair made with a polypropylene seat

Polyester (PES) – Fibers, textiles.

Polyethylene terephthalate (PET) – Carbonated drinks bottles, peanut
butter jars, plastic film, microwavable packaging.

Polyethylene (PE) – Wide range of inexpensive uses including supermarket
bags, plastic bottles.

High-density polyethylene (HDPE) – Detergent bottles, milk jugs, and
molded plastic cases.

Polyvinyl chloride (PVC) – Plumbing pipes and guttering, shower curtains,
window frames, flooring.

Polyvinylidene chloride (PVDC) (Saran) – Food packaging.

Low-density polyethylene (LDPE) – Outdoor furniture, siding, floor tiles,
shower curtains, clamshell packaging.

Polypropylene (PP) – Bottle caps, drinking straws, yogurt containers,
appliances, car fenders (bumpers), plastic pressure pipe systems.

Polystyrene (PS) – Packaging foam/"peanuts", food containers, plastic
tableware, disposable cups, plates, cutlery, CD and cassette boxes.

High impact polystyrene (HIPS) -: Refrigerator liners, food packaging,
vending cups.

Polyamides (PA) (Nylons) – Fibers, toothbrush bristles, tubing, fishing line,
low strength machine parts: under-the-hood car engine parts or gun

Acrylonitrile butadiene styrene (ABS) – Electronic equipment cases (e.g.,
computer monitors, printers, keyboards), drainage pipe.

Polyethylene/Acrylonitrile Butadiene Styrene (PE/ABS) – A slippery blend of
PE and ABS used in low-duty dry bearings.

Polycarbonate (PC) – Compact discs, eyeglasses, riot shields, security
windows, traffic lights, lenses.

Polycarbonate/Acrylonitrile Butadiene Styrene (PC/ABS) – A blend of PC
and ABS that creates a stronger plastic. Used in car interior and exterior
parts, and mobile phonebodies.

Polyurethanes (PU) – Cushioning foams, thermal insulation foams, surface
coatings, printing rollers (Currently 6th or 7th most commonly used plastic
material, for instance the most commonly used plastic in cars).

Special purpose plastics
See also: High performance plastics

Maleimide/Bismaleimide Used in high temperature composite materials.

Melamine formaldehyde (MF) – One of the aminoplasts, and used as a
multi-colorable alternative to phenolics, for instance in moldings (e.g.,
break-resistance alternatives to ceramic cups, plates and bowls for
children) and the decorated top surface layer of the paper laminates (e.g.,

Plastarch material – Biodegradable and heat resistant, thermoplastic
composed of modified corn starch.

Phenolics (PF) or (phenol formaldehydes) – High modulus, relatively heat
resistant, and excellent fire resistant polymer. Used for insulating parts in
electrical fixtures, paper laminated products (e.g., Formica), thermally
insulation foams. It is a thermosetting plastic, with the familiar trade name
Bakelite, that can be molded by heat and pressure when mixed with a
filler-like wood flour or can be cast in its unfilled liquid form or cast as
foam (e.g., Oasis). Problems include the probability of moldings naturally
being dark colors (red, green, brown), and as thermoset it is difficult
to recycle.

Polyepoxide (Epoxy) Used as an adhesive, potting agent for electrical
components, and matrix for composite materials with hardeners
including amine, amide, and Boron Trifluoride.

Polyetheretherketone (PEEK) – Strong, chemical- and heat-resistant
thermoplastic, biocompatibility allows for use in medical
implant applications, aerospace moldings. One of the most expensive
commercial polymers.

Polyetherimide (PEI) (Ultem) – A high temperature, chemically stable
polymer that does not crystallize.

Polyimide—A High temperature plastic used in materials such
as Kapton tape.

Polylactic acid (PLA) – A biodegradable, thermoplastic found converted into
a variety of aliphatic polyesters derived from lactic acid which in turn can
be made by fermentation of various agricultural products such as corn
starch, once made from dairy products.

Polymethyl methacrylate (PMMA) (Acrylic) – Contact lenses (of the original
"hard" variety), glazing (best known in this form by its various trade
names around the world; e.g., Perspex, Oroglas, Plexiglas), aglets,
fluorescent light diffusers, rear light covers for vehicles. It forms the basis
of artistic and commercial acrylic paints when suspended in water with the
use of other agents.

Polytetrafluoroethylene (PTFE) – Heat-resistant, low-friction coatings, used
in things like non-stick surfaces for frying pans, plumber's tape and water
slides. It is more commonly known as Teflon.

Urea-formaldehyde (UF) – One of the aminoplasts and used as a multicolorable alternative to phenolics. Used as a wood adhesive (for plywood,
chipboard, hardboard) and electrical switch housings.

Furan—Resin based on Furfuryl Alcohol used in foundry sands and
biologically derived composites.

Silicone—Heat resistant resin used mainly as a sealant but also used for
high temperature cooking utensils and as a base resin for industrial paints.

Polysulfone—High temperature melt processable resin used in
membranes, filtration media, water heater dip tubes and other high
temperature applications.


Plastic (LDPE) bowl, by GEECO, Made in England, c1950.
The development of plastics has evolved from the use of natural plastic materials
(e.g., chewing gum, shellac) to the use of chemically modified, natural materials
(e.g., rubber, nitrocellulose, collagen, galalite) and finally to completely synthetic
molecules (e.g., bakelite,epoxy, Polyvinyl chloride). Early plastics were bioderived materials such as egg and blood proteins, which are organic polymers. In
1600 BC, Mesoamericans used natural rubber for balls, bands, and figurines.
Treated cattle horns were used as windows for lanterns in theMiddle Ages.
Materials that mimicked the properties of horns were developed by treating milkproteins (casein) with lye.
In the 1800s, as industrial chemistry developed during the Industrial Revolution,
many materials were reported. The development of plastics also accelerated
with Charles Goodyear's discovery of vulcanization to thermoset materials
derived from natural rubber.
Parkesine is considered the first man-made plastic. The plastic material was
patented by Alexander Parkes, In Birmingham, UK in 1856.[9]It was unveiled

at the 1862 Great International Exhibition in London.[10] Parkesine won a bronze
medal at the 1862 World's fair in London. Parkesine was made from cellulose (the
major component of plant cell walls) treated with nitric acid as a solvent. The
output of the process (commonly known as cellulose nitrate or pyroxilin) could be
dissolved in alcohol and hardened into a transparent and elastic material that
could be molded when heated.[11] By incorporating pigments into the product, it
could be made to resemble ivory.
In the early 1900s, Bakelite, the first fully synthetic thermoset, was reported by
Belgian chemist Leo Baekeland.
After World War I, improvements in chemical technology led to an explosion in
new forms of plastics, with mass production beginning in the 1940s and 1950s
(around World War II).[12] Among the earliest examples in the wave of new
polymers were polystyrene (PS), first produced by BASF in the 1930s,
and polyvinyl chloride (PVC), first created in 1872 but commercially produced
in the late 1920s.[3] In 1923, Durite Plastics Inc. was the first manufacturer of
phenol-furfural resins.[13] In 1933, polyethylene was discovered byImperial
Chemical Industries (ICI) researchers Reginald Gibson and Eric Fawcett. [3]
In 1954, Polypropylene was found by Giulio Natta and began to be manufactured
in 1957.[3]
In 1954, expanded polystyrene (used for building insulation, packaging, and
cups) was invented by Dow Chemical.[3]
Polyethylene terephthalate (PET)'s discovery is credited to employees of
the Calico Printers' Association in the UK in 1941; it was licensed to DuPont for
the USA and ICI otherwise, and as one of the few plastics appropriate as a
replacement for glass in many circumstances, resulting in widespread use for
bottles in Europe.[3]
Most plastics contain organic polymers. The vast majority of these polymers are
based on chains of carbon atoms alone or with oxygen, sulfur, or nitrogen as
well. The backbone is that part of the chain on the main "path" linking a large
number of repeat units together. To customize the properties of a plastic,
different molecular groups "hang" from the backbone (usually they are "hung" as
part of the monomers before the monomers are linked together to form the
polymer chain). The structure of these "side chains" influence the properties of
the polymer. This fine tuning of the repeating unit's molecular structure
influences the properties of the polymer.
Most plastics contain other organic or inorganic compounds blended in. The
amount of additives ranges from zero percentage (for example in polymers used
to wrap foods) to more than 50% for certain electronic applications. The average
content of additives is 20% by weight of the polymer [citation needed].
Many of the controversies associated with plastics are associated with the
additives.[14] Organotin compounds are particularly toxic.[15]

Fillers improve performance and/or reduce production costs. Stabilizing
additives include fire retardants to lower the flammability of the material. Many
plastics contain fillers, relatively inert and inexpensive materials that make the
product cheaper by weight.
Typically fillers are mineral in origin, e.g., chalk. Some fillers are more chemically
active and are called reinforcing agents. Other fillers include zinc oxide, wood
flour, ivory dust, cellulose and starch.[16]
Since many organic polymers are too rigid for particular applications, they are
blended with plasticizers (the largest group of additives[15]), oily compounds that
confer improvedrheology.
Colorants are common additives, although their weight contribution is small.
Plastics are usually classified by their chemical structure of the polymer's
backbone and side chains. Some important groups in these classifications are
the acrylics, polyesters,silicones, polyurethanes, and halogenated plastics.
Plastics can also be classified by the chemical process used in their synthesis,
such as condensation, polyaddition, and cross-linking.[17]
Thermoplastics and thermosetting polymers
There are two types of plastics: thermoplastics and thermosetting polymers.
Thermoplastics are the plastics that do not undergo chemical change in their
composition when heated and can be molded again and again. Examples
include polyethylene, polypropylene, polystyrene and polyvinyl chloride.
Common thermoplastics range from 20,000 to 500,000 amu, while thermosets
are assumed to have infinite molecular weight. These chains are made up of
many repeating molecular units, known as repeat units, derived from monomers;
each polymer chain will have several thousand repeating units.
Thermosets can melt and take shape once; after they have solidified, they stay
solid. In the thermosetting process, a chemical reaction occurs that is
irreversible. The vulcanization of rubber is a thermosetting process. Before
heating with sulfur, the polyisoprene is a tacky, slightly runny material, but after
vulcanization the product is rigid and non-tacky.
Other classifications
Other classifications are based on qualities that are relevant for manufacturing
or product design. Examples of such classes are the thermoplastic and
thermoset, elastomer,structural, biodegradable, and electrically conductive.
Plastics can also be classified by various physical properties, such
as density, tensile strength, glass transition temperature, and resistance to
various chemical products.
Main article: Biodegradable plastic

Biodegradable plastics break down (degrade) upon exposure to sunlight
(e.g., ultra-violet radiation), water or dampness, bacteria, enzymes, wind
abrasion, and in some instances, rodent, pest, or insect attack are also included
as forms of biodegradation or environmental degradation. Some modes of
degradation require that the plastic be exposed at the surface, whereas other
modes will only be effective if certain conditions exist in landfill or composting
systems. Starch powder has been mixed with plastic as a filler to allow it to
degrade more easily, but it still does not lead to complete breakdown of the
plastic. Some researchers have actually genetically engineered bacteria that
synthesize a completely biodegradable plastic, but this material, such as Biopol,
is expensive at present.[19] Companies have made biodegradable additives to
enhance the biodegradation of plastics.
Natural vs synthetic
Main article: Bioplastic
Most plastics are produced from petrochemicals. Motivated by the finiteness of
petrochemical reserves and threat of global warming, bioplastics are being
developed. Bioplastics are made substantially from renewable plant materials
such as cellulose and starch.[20]
In comparison to the global consumption of all flexible packaging, estimated at
12.3 million tonnes/year, estimates put global production capacity at 327,000
tonnes/year for related bio-derived materials.[21][22]
Crystalline vs amorphous
Some plastics are partially crystalline and
partially amorphous in molecular structure, giving them both a melting point (the
temperature at which the attractive intermolecular forces are overcome) and one
or more glass transitions (temperatures above which the extent of localized
molecular flexibility is substantially increased). The so-called semicrystalline plastics include polyethylene, polypropylene, poly (vinyl chloride),
polyamides (nylons), polyesters and some polyurethanes. Many plastics are
completely amorphous, such as polystyrene and its copolymers, poly (methyl
methacrylate), and all thermosets.

Molded plastic food replicas on display outside a restaurant in Japan
In 1851, Nelson Goodyear added fillers to natural rubber materials to
form ebonite.[16]

Main article: Bakelite
The first plastic based on a synthetic polymer was made
from phenol and formaldehyde, with the first viable and cheap synthesis
methods invented in 1907, by Leo Hendrik Baekeland, a Belgian-born
American living in New York state. Baekeland was looking for an insulating
shellac to coat wires in electric motors and generators. He found that combining
phenol (C6H5OH) and formaldehyde (HCOH) formed a sticky mass and later found
that the material could be mixed with wood flour, asbestos, or slate dust to
create strong and fire resistant "composite" materials. The new material tended
to foam during synthesis, requiring that Baekeland build pressure vessels to
force out the bubbles and provide a smooth, uniform product, as he announced
in 1909, in a meeting of the American Chemical Society. [23] Bakelite was originally
used for electrical and mechanical parts, coming into widespread use in
consumer goods and jewelry in the 1920s. Bakelite was a purely synthetic
material, not derived from living matter. It was also an early thermosetting
Representative polymers
Main articles: Polystyrene and PVC

Plastic piping and firestops being installed in Ontario. Certain plastic pipes can be
used in some non-combustible buildings, provided they are firestopped properly
and that the flame spread ratings comply with the local building code.

Unplasticised polystyrene is a rigid, brittle, inexpensive plastic that has been
used to make plastic model kits and similar knick-knacks. It also is the basis for
some of the most popular "foamed" plastics, under the name styrene
foam or Styrofoam. Like most other foam plastics, foamed polystyrene can be
manufactured in an "open cell" form, in which the foam bubbles are
interconnected, as in an absorbent sponge, and "closed cell", in which all the
bubbles are distinct, like tiny balloons, as in gas-filled foam insulation and
flotation devices. In the late 1950s, high impact styrene was introduced, which
was not brittle. It finds much current use as the substance of toy figurines and

Styrene polymerization
Polyvinyl chloride
Polyvinyl chloride (PVC, commonly called "vinyl")[24] incorporates chlorine atoms.
The C-Cl bonds in the backbone are hydrophobic and resist oxidation (and
burning). PVC is stiff, strong, heat and weather resistant, properties that
recommend its use in devices for plumbing, gutters, house siding, enclosures for
computers and other electronics gear. PVC can also be softened with chemical
processing, and in this form it is now used for shrink-wrap, food packaging, and
rain gear.

Vinylchloride polymerization
All PVC polymers are degraded by heat and light. When this happens, hydrogen
chloride is released into the atmosphere and oxidation of the compound occurs.
Because hydrogen chloride readily combines with water vapor in the air to
form hydrochloric acid,[26] polyvinyl chloride is not recommended for long-term
archival storage of silver, photographic film or paper (mylar is preferable).[27]
Main article: Nylon
The plastics industry was revolutionized in the 1930s with the announcement
of polyamide (PA), far better known by its trade name nylon. Nylon was the first
purely synthetic fiber, introduced by DuPont Corporation at the 1939 World's
Fair in New York City.
In 1927, DuPont had begun a secret development project designated Fiber66,
under the direction of Harvard chemist Wallace Carothersand chemistry
department director Elmer Keiser Bolton. Carothers had been hired to perform
pure research, and he worked to understand the new materials' molecular

structure and physical properties. He took some of the first steps in the
molecular design of the materials.
His work led to the discovery of synthetic nylon fiber, which was very strong but
also very flexible. The first application was for bristles for toothbrushes.
However, Du Pont's real target was silk, particularly silk stockings. Carothers and
his team synthesized a number of different polyamides including polyamide 6.6
and 4.6, as well as polyesters. [28]

General condensation polymerization reaction for nylon
It took DuPont twelve years and US$27 million to refine nylon, and to synthesize
and develop the industrial processes for bulk manufacture. With such a
, it was no surprise that Du Pont spared little expense
to promote nylon after its introduction, creating a public sensation, or "nylon
Nylon mania came to an abrupt stop at the end of 1941 when the USA
entered World War II. The production capacity that had been built up to
produce nylon stockings, or justnylons, for American women was taken over to
manufacture vast numbers of parachutes for fliers and paratroopers. After the
war ended, DuPont went back to selling nylon to the public, engaging in another
promotional campaign in 1946 that resulted in an even bigger craze, triggering
the so-called nylon riots.
Subsequently polyamides 6, 10, 11, and 12 have been developed based on
monomers which are ring compounds; e.g. caprolactam. Nylon 66 is a material
manufactured bycondensation polymerization.
Nylons still remain important plastics, and not just for use in fabrics. In its bulk
form it is very wear resistant, particularly if oil-impregnated, and so is used to
build gears, plain bearings, valve seats, seals and because of good heatresistance, increasingly for under-the-hood applications in cars, and other
mechanical parts.
Natural rubber is an elastomer (an elastic hydrocarbon polymer) that originally
was derived from latex, a milky colloidal suspension found in specialised vessels
in some plants. It is useful directly in this form (indeed, the first appearance of
rubber in Europe was cloth waterproofed with unvulcanized latex from Brazil).
However, in 1839, Charles Goodyearinvented vulcanized rubber; a form of
natural rubber heated with sulfur (and a few other chemicals), forming crosslinks between polymer chains (vulcanization), improving elasticity and durability.
Synthetic rubber
Main article: Synthetic rubber

The first fully synthetic rubber was synthesized by Sergei Lebedev in 1910. In
World War II, supply blockades of natural rubber from South East Asia caused a
boom in development of synthetic rubber, notably styrene-butadiene rubber. In
1941, annual production of synthetic rubber in the U.S. was only 231 tonnes
which increased to 840,000 tonnes in 1945. In the space race and nuclear arms
race, Caltech researchers experimented with using synthetic rubbers for solid
fuel for rockets. Ultimately, all large military rockets and missiles would use
synthetic rubber based solid fuels, and they would also play a significant part in
the civilian space effort.
Properties of plastics
The properties of plastics are defined chiefly by the organic chemistry of the
polymer such as hardness, density, and resistance to heat, organic
solvents, oxidation, and ionizing radiation. In particular, most plastics will melt
upon heating to a few hundred degrees celsius.[29] While plastics can be made
electrically conductive, with the conductivity of up to 80 kS/cm in stretchoriented polyacetylene,[30] they are still no match for most metals
like copper which have conductivities of several hundreds kS/cm.
UL Standards
Many properties of plastics are determined by tests as specified by Underwriters
Laboratories, such as:

Flammability - UL94

High voltage arc tracking rate - UL746A

Comparative Tracking Index

Many properties of plastics are determined by standards as specified by ISO,
such as:

ISO 306 - Thermoplastics

Pure plastics have low toxicity due to their insolubility in water and because they
are biochemically inert, due to a large molecular weight. Plastic products contain
a variety of additives, some of which can be toxic. For
example, plasticizers like adipates and phthalates are often added to brittle
plastics like polyvinyl chloride to make them pliable enough for use in food
packaging, toys, and many other items. Traces of these compounds can leach
out of the product. Owing to concerns over the effects of such leachates,
theEuropean Union has restricted the use of DEHP (di-2-ethylhexyl phthalate)
and other phthalates in some applications, and the United States has limited the
use of DEHP, DPB,BBP, DINP, DIDP, and DnOP in children's toys and child care
articles with the Consumer Product Safety Improvement Act. Some compounds
leaching from polystyrene food containers have been proposed to interfere with
hormone functions and are suspected human carcinogens. [31] Other chemicals of
potential concern include alkylphenols.[15]

Whereas the finished plastic may be non-toxic, the monomers used in the
manufacture of the parent polymers may be toxic. In some cases, small amounts
of those chemicals can remain trapped in the product unless suitable processing
is employed. For example, the World Health Organization's International Agency
for Research on Cancer (IARC) has recognized vinyl chloride, the precursor to
PVC, as a human carcinogen.[31]
Bisphenol A
Some polymers may also decompose into the monomers or other toxic
substances when heated. In 2011, it was reported that "almost all plastic
products" sampled released chemicals with estrogenic activity, although the
researchers identified plastics which did not leach chemicals with estrogenic
The primary building block of polycarbonates, bisphenol A (BPA), is an estrogenlike endocrine disruptor that may leach into food.[31] Research in Environmental
Health Perspectives finds that BPA leached from the lining of tin cans, dental
sealants and polycarbonate bottles can increase body weight of lab animals'
offspring.[33] A more recent animal study suggests that even low-level exposure
to BPA results in insulin resistance, which can lead to inflammation and heart
As of January 2010, the LA Times newspaper reports that the United States FDA
is spending $30 million to investigate indications of BPA being linked to cancer. [35]
Bis(2-ethylhexyl) adipate, present in plastic wrap based on PVC, is also of
concern, as are the volatile organic compounds present in new car smell.
The European Union has a permanent ban on the use of phthalates in toys. In
2009, the United States government banned certain types of phthalates
commonly used in plastic.[36]
Environmental effects
See also: Plastic pollution, Marine debris and Great Pacific Garbage Patch
Most plastics are durable and degrade very slowly; the very chemical bonds that
make them so durable tend to make them resistant to most natural processes of
degradation. However, microbial species and communities capable of degrading
plastics are discovered from time to time, and some show promise as being
useful for bioremediating certain classes of plastic waste.

In 1975 a team of Japanese scientists studying ponds containing waste
water from a nylon factory, discovered a strain of Flavobacterium that
digested certain byproducts ofnylon 6 manufacture, such as the linear
dimer of 6-aminohexanoate.[37] Nylon 4 or polybutyrolactam can be
degraded by the (ND-10 and ND-11) strands of Pseudomonas sp. found in
sludge. This produced γ-aminobutyric acid (GABA) as a byproduct. [38]

Several species of soil fungi can consume polyurethane.[39] This includes
two species of the Ecuadorian fungus Pestalotiopsis that can consume
polyurethane aerobically and also in anaerobic conditions such as those at
the bottom of landfills.[40]

Methanogenic consortia degrade styrene, using it as a carbon source.
Pseudomonas putida can convert styrene oil into
various biodegradablepolyhydroxyalkanoates.[42][43][44]

Microbial communities isolated from soil samples mixed with starch have
been shown to capable of degrading polypropylene.[45]

The fungus Aspergillus fumigatus effectively degrades plasticized PVC.
Phanerochaete chrysosporium was grown on PVC in a mineral salt agar.
Phanerochaete chrysosporium, Lentinus tigrinus, Aspergillus niger,
and Aspergillus sydowii can also effectively degrade PVC.
Phanerochaete chrysosporium was grown on PVC in a mineral salt agar.

Acinetobacter has been found to partially degrade low molecular
weight polyethylene oligomers.[49] When used in
combination, Pseudomonas fluorescens and Sphingomonascan degrade
over 40% of the weight of plastic bags in less than three months. [50][51] The
thermophilic bacterium Brevibacillus borstelensis (strain 707) was isolated
from a soil sample and found capable of using low-density polyethylene as
a sole carbon source when incubated at 50 degrees Celsius. Pre-exposure
of the plastic to ultraviolet radiation broke chemical bonds and aided
biodegradation; the longer the period of UV exposure, the greater the
promotion of the degradation.[52]

Less desirably, hazardous molds have been found aboard space stations,
molds that degrade rubber into a digestible form. [53]

Several species of yeasts, bacteria, algae and lichens have been found
growing on synthetic polymer artifacts in museums and at archaeological

In the plastic-polluted waters of the Sargasso sea, bacteria have been
found that consume various types of plastic; however it is unknown to
what extent these bacteria effectively clean up poisons rather than simply
releasing them into the marine microbial ecosystem.

Plastic eating microbes also have been found in landfills. [55]

Nocardia can degrade PET with an esterase enzyme. [56]

The fungi Geotrichum candidum, found in Belize, has been found to
consume the polycarbonate plastic found in CD's.[57][58]

Phenol-formaldehyde, commonly known as bakelite, is degraded by the
white rot fungus Phanerochaete chrysosporium [59]

The futuro house was made of fibreglass-reinforced polyesters, polyesterpolyurethane, and poly(methylmethacrylate.) One such house was found
to be harmfully degraded by Cyanobacteria and Archaea. [60][61]

Since the 1950s, one billion tons of plastic have been discarded and some of that
material might persist for centuries or much longer, as is demonstrated by the
persistence of natural materials such as amber. [62]

Serious environmental threats from plastic have been suggested in the light of
the increasing presence of microplastics in the marine food chain along with
many highly toxic chemical pollutants that accumulate in plastics. They also
accumulate in larger fragmented pieces of plastic called nurdles.[63] In the 1960s
the latter were observed in the guts of seabirds, and since then have been found
in increasing concentration.[64] In 2009, it was estimated that 10% of modern
waste was plastics,[12] although estimates vary according to region.[64] Meanwhile,
50-80% of debris in marine areas is plastic.[64]
Before the ban on the use of CFCs in extrusion of polystyrene (and in general
use, except in life-critical fire suppression systems; see Montreal Protocol), the
production of polystyrene contributed to the depletion of the ozone layer, but
current extrusion processes use non-CFCs.
Climate change
The effect of plastics on global warming is mixed. Plastics are generally made
from petroleum. If the plastic is incinerated, it increases carbon emissions; if it is
placed in a landfill, it becomes a carbon sink [65] although biodegradable plastics
have caused methane emissions.[66] Due to the lightness of plastic versus glass
or metal, plastic may reduce energy consumption. For example, packaging
beverages in PET plastic rather than glass or metal is estimated to save 52% in
transportation energy.[3]
Production of plastics
Production of plastics from crude oil requires 62 to 108 MJ of energy per kilogram
(taking into account the average efficiency of US utility stations of 35%).
Producing silicon and semiconductors for modern electronic equipment is even
more energy consuming: 230 to 235 MJ per 1 kilogram of silicon, and about
3,000 MJ per kilogram of semiconductors. [67] This is much higher, compared to
many other materials, e.g. production of iron from iron ore requires 20-25 MJ of
energy, glass (from sand, etc.) - 18-35 MJ, steel (from iron) - 20-50 MJ, paper
(from timber) - 25-50 MJ per kilogram.[68]
Incineration of plastics
Controlled high-temperature incineration, above 850C for two seconds,
performed with selective additional heating, breaks down toxic dioxins and
furans from burning plastic, and is widely used in municipal solid waste
incineration.[69] Municipal solid waste incinerators also normally include flue gas
treatments to reduce pollutants further. [69] This is needed because uncontrolled
incineration of plastic produces polychlorinated dibenzo-p-dioxins, a carcinogen
(cancer causing chemical). The problem occurs as the heat content of the waste
stream varies.[70] Open-air burning of plastic occurs at lower temperatures, and
normally releases such toxic fumes.
Pyrolytic disposal
Plastics can be pyrolyzed into hydrocarbon fuels, since plastics have hydrogen
and carbon. One kilogram of waste plastic produces roughly a liter of

Thermoplastics can be remelted and reused, and thermoset plastics can be
ground up and used as filler, although the purity of the material tends to degrade
with each reuse cycle. There are methods by which plastics can be broken back
down to a feedstock state.
The greatest challenge to the recycling of plastics is the difficulty of automating
the sorting of plastic wastes, making it labor-intensive. Typically, workers sort the
plastic by looking at the resin identification code, although common containers
like soda bottles can be sorted from memory. Typically, the caps for PETE bottles
are made from a different kind of plastic which is not recyclable, which presents
additional problems to the automated sorting process. Other recyclable materials
such as metals are easier to process mechanically. However, new processes of
mechanical sorting are being developed to increase capacity and efficiency of
plastic recycling.
While containers are usually made from a single type and color of plastic, making
them relatively easy to be sorted, a consumer product like a cellular phone may
have many small parts consisting of over a dozen different types and colors of
plastics. In such cases, the resources it would take to separate the plastics far
exceed their value and the item is discarded. However, developments are taking
place in the field of active disassembly, which may result in more consumer
product components being re-used or recycled. Recycling certain types of
plastics can be unprofitable, as well. For example, polystyrene is rarely recycled
because it is usually not cost effective. These unrecycled wastes are typically
disposed of in landfills, incinerated or used to produce electricity at waste-toenergy plants.
A first success in recycling of plastics is Vinyloop, a recycling process and an
approach of the industry to separate PVC from other materials through a process
of dissolution, filtration and separation of contaminations. A solvent is used in a
closed loop to elute PVC from the waste. This makes it possible to recycle
composite structure PVC waste which normally is being incinerated or put in a
landfill. Vinyloop-based recycled PVC's primary energy demand is 46 percent
lower than conventional produced PVC. The global warming potential is 39
percent lower. This is why the use of recycled material leads to a significant
better ecological footprint.[72] This process was used after the Olympic Games in
London 2012. Parts of temporary Buildings like the Water Polo Arena or the Royal
Artillery Barracks were recycled. This way, the PVC Policy could be fulfilled which
says that no PVC waste should be left after the games. [73]
In 1988, to assist recycling of disposable items, the Plastic Bottle Institute of
the Society of the Plastics Industry devised a now-familiar scheme to mark
plastic bottles by plastic type. A plastic container using this scheme is marked
with a triangle of three "chasing arrows", which encloses a number giving the
plastic type:

Plastics type marks: the resin identification code[74]
1. PET (PETE), polyethylene terephthalate

2. HDPE, high-density polyethylene
3. PVC, polyvinyl chloride
4. LDPE, low-density polyethylene,
5. PP, polypropylene
6. PS, polystyrene
7. Other types of plastics (see list, below)
See also

Conductive polymer

Corn construction

Molding (process)

Flexible mold

Injection molding


Light activated resin


Organic light emitting diode

Plastics engineering

Plastics extrusion

Plastic film

Plastic recycling


Progressive bag alliance

Roll-to-roll processing

Self-healing plastic


Timeline of materials technology


Harmful Chemicals in our Environment
Over the past century humans have introduced a large number of
chemical substances into the environment. Some are the waste from
industrial and agricultural processes. Some have been designed as structural
materials and others have been designed to perform various functions such as

healing the sick or killing pests and weeds. Obviously some chemicals are useful
but many are toxic and their harm to the environment and our health far
outweighs their benefit to society. We need to manage the risks better by only
using chemicals, which are safe.
Chemicals enter air as emissions and water as
effluent. Industrial and motor vehicle emissions of
nitrogen and sulphur oxides cause acid rain, which
poisons fish and other aquatic organisms in rivers and
lakes and affects the ability of soil to support plants.
Carbon dioxide causes the greenhouse effect and
climate change. Chlorofluorocarbons (CFCs) cause the
destruction of ozone in the stratosphere and create
the possibility of serious environmental damage from
ultraviolet radiation. Chemical fertilisers and nutrients
run-off from farms and gardens cause the build up of
toxic algae in rivers, making them uninhabitable to
aquatic organisms and unpleasant for humans. Some
toxic chemicals find their way from landfill waste sites
into our groundwater, rivers and oceans and induce genetic changes that
compromise the ability of life to reproduce and survive.
The impact of human activities on the environment is complex and affects a
chain of interconnecting ecosystems. The extinction of species all along the
chain may mean the loss of useful genetic material or life saving cancer drugs or
safer alternatives to the dangerous chemicals in use at the moment.
Organochlorine compounds such as polychlorinated biphenyls or PCBs were
developed originally for use in electric equipment as cooling agents and are very
dangerous chemicals. During the manufacture and disposal of products
containing PCBs, and as a result of accidents, millions of gallons of PCB oil have
leaked out. Although their manufacture in the UnitedStates was halted in the
1970s and they are being phased out, they are difficult to detect, are nearly
indestructible and large quantities remain in existence and they will remain in
the environment for a long time. They accumulate in the food chain and
significant levels of them have been found in marine species, particularly
mammals and sea birds, decades after their production was discontinued. They
are carcinogenic and capable of damaging the liver, nervous system and the
reproductive system in adults. When PCBs are burned, even more toxic dioxins
are formed.
Dioxins, are a class of super-toxic chemicals formed as a by-product of the
manufacture, moulding, or burning of organic chemicals and plastics that contain
chlorine. They are the most toxic man-made organic chemicals known. They
cause serious health effects even at levels as low as a few parts per trillion. Only
radioactive waste is more toxic. They are virtually indestructible and are excreted
by the body extremely slowly. Dioxins became known when Vietnam War
veterans and Vietnamese civilians, exposed to dioxin-contaminated Agent
Orange, became ill.

Dioxins enter the body in food and accumulate in body fat. They bind to cell
receptors and disrupt hormone functions in the body and they also affect gene
functions. Our bodies have no defence against dioxins which may cause a wide
range of problems, from cancer to reduced immunity to nervous system
disorders to miscarriages and birth deformity. The effects can be very obvious or
subtle. Because they change gene functions, they can cause genetic diseases to
appear and they can interfere with child development. Attention Deficit
Disorder, diabetes, endometriosis, chronic fatigue syndrome, rare nervous and
blood disorders have been linked to exposure to dioxins and PCBs.
Over the past 40 years there has been a dramatic increase in the manufacture
and use of chlorinated organic chemicals in plastics, insecticides and herbicides.
Dioxins have been found in high concentrations near to the sites where these
chemicals have been produced and where insecticides and herbicides have been
heavily used, such as on farms, orchards, or along electric and railway lines.
They have also been a found downstream from paper mills where chlorine
chemicals have been used to bleach wood pulp.
In the last few years we have begun to discard our unfashionable household
plastic products, together with industrial and medical waste by burning them in
incinerators. Dioxins formed during the combustion process have been carried
for hundreds of miles on tiny specks of ash and contaminated the countryside.
They settle on pastures and crops and get eaten by cows, pigs and chickens.
They get into lakes, streams, and ocean and are taken up by fish. They go
through the food chain and appear in meat and milk and accumulate in the fat
cells of our bodies.
Cadmium occurs naturally in the earth's crust combined with other elements. It
is usually formed as a mineral such as cadmium oxide, cadmium chloride, or
cadmium sulphate and although these compounds are highly toxic they are less
harmful when bound to rocks. They are present in coal and in the soil.
Cadmium is useful because it doesn't corrode easily. It is used in batteries,
plastics, pigments and metal coatings. Cadmium gets into the environment
through landfills, poor waste disposal methods and leaks at hazardous
waste sites. It is produced by mining and other industrial activities. Cadmium
particles enter our air when we burn coal for energy and incinerate household
waste. The particles can travel far before falling to the ground or water. Each
year many tonnes of cadmium are discharged into our seas and oceans. Animals
and plants take up cadmium when it is in the environment. If we consume food
contaminated with cadmium it can irritate our digestive system and cause
vomiting and diarrhoea. If inhaled it can damage our lungs. Even when levels of
exposure are low, over time, cadmium accumulates in the body and it can be
difficult to get rid of. Accumulated cadmium can cause kidneys and bone disease.
We take cadmium into our body by:

Inhaling it when working in factories that make batteries or do welding,
brazing or soldering

Inhaling it when near power stations or factories burning of fossil fuels

Eating foods in which it accumulates such as shellfish, liver and kidney

Drinking water that is contaminated

Smoking cigarettes

Potentially dangerous chemicals such as these are being introduced into the
environment all the time. As in the case of PCBs their effect on living things may
not be known until many years after their release. Hundreds of thousands of
different chemicals are marketed worldwide. Of these 5000 are produced in
quantities over 10 tonnes a year and 1500 are produced in quantities over 1000
tonnes year.
We do not have enough information about the environmental effects of these
industrial chemicals and their effects on humans. The balance between human
activity and ecological sustainability is wrong.
What you can do
Use biodegradable products. Make your own cleaning agent using safe materials.
Dispose of chemical waste carefully. Do not put them down the sink. Be wise
with home maintenance and in the garden. Do not burn plastics.
Avoid all organic chemicals that have "chloro" as part of their names including
wood preservatives, herbicides and insecticides. Avoid chlorine bleach (sodium
hypochlorite) and products containing it. Use oxygen bleach instead. Use
unbleached paper products.Avoid "Permethrin" flea sprays for pets. Avoid
products made of or packaged in polyvinyl chloride (PVC). Avoid cling flim plastic
wraps unless they are clearly identified as non-chlorinated plastic.
To minimise your risk of dioxins accumulating in your body avoid all full-fat dairy
products and fatty meats such as beef or pork. Wash all fruits and vegetables to
remove chlorophenol pesticide residue. Avoid grapes and raisins unless they are
clearly labelled as organically grown. Avoid soaps, toothpaste and deodorants
containing "triclosan," a chlorophenol.
We can reduce the dioxins if we stop producing PVCs and other chlorinated
chemicals. If your local government sends its waste to an incinerator, request
that they stop burning plastics and introduce a comprehensive recycling service.
Write to companies and ask them to use safe substitutes to chlorinated plastics.
Ask your supermarket to sell Totally Chlorine Free (TCF) products. Join or form a
local environmental group campaigning against hazardous chemicals.
People who work with cadmium should take care not to inhale cadmiumcontaining dust and should avoid carrying it home from work on their clothes,
skin or hair. Eat from a wide range of foods to prevent the risk of ingesting toxic
levels of cadmium.
Link to Green Sowers solutions for this problem
Retrieve green groups directly addressing Chemical Pollution from the database
Bioplastics and biodegradable plastics

by Chris Woodford. Last updated: May 27, 2014.
From cars to food wrap and from planes to pens, you can make anything and
everything from plastics—unquestionably the world's most versatile materials.
But there's a snag. Plastics are synthetic (artificially created) chemicals that
don't belong in our world and don't mix well with nature. Discarded plastics are a
big cause ofpollution, cluttering rivers, seas, and beaches, killing fish, choking
birds, and making our environment a much less attractive place. Public pressure
to clean up has produced plastics that seem to be more environmentally friendly.
But are they all they're cracked up to be?
Photo: A typical eco-friendly bag made using EPI chemical additives. Added to
normal plastics in small quantities (about 2–3 percent), they cause the plastic to
break down after exposure to sunlight, heat, or after repeated stresses and
strains through regular use.
The global plastics problem

Plastics are carbon-based polymers (long-chain molecules that repeat their
structures over and over) and we make them mostly from petroleum. They're
incredibly versatile—by definition: the word plastic, which means flexible, says it
all. The trouble is that plastic is just too good. We use it for mostly disposable,
low-value items such as food-wrap and product packaging, but there's nothing
particularly disposable about most plastics. On average, we use plastic bags for
12 minutes before getting rid of them, yet they can take fully 500 years to break
down in the environment (quite how anyone knows this is a mystery, since
plastics have been around only about a century).
Getting rid of plastics is extremely difficult. Burning them can give off toxic
chemicals such as dioxins, while collecting andrecycling them responsibly is also
difficult, because there are many different kinds and each has to be recycled by
a different process. If we used only tiny amounts of plastics that wouldn't be so
bad, but we use them in astounding quantities. In Britain alone (one small island
in a very big world), people use 8 billion disposable plastic bags each year. If
you've ever taken part in a beach clean, you'll know that about 80 percent of the
waste that washes up on the shore is plastic, including bottles, bottle tops, and
tiny odd fragments known as "mermaids' tears."
We're literally drowning in plastic we cannot get rid of. And we're making most of
it from oil—a non-renewable resource that's becoming increasingly expensive.
It's been estimated that 200,000 barrels of oil are used each day to make plastic
packaging for the United States alone.
Photo: A biodegradable fruit and vegetable bag produced by d 2w® for the UK's
Co-op chain of grocery stores.
Making better plastics
Ironically, plastics are engineered to last. You may have noticed that some
plastics do, gradually, start to go cloudy or yellow after long exposure to daylight
(more specifically, in the ultraviolet light that sunlight contains). To stop this
happening, plastics manufacturers generally introduce extra stabilizing
chemicals to give their products longer life. With society's ever-increasing focus
on protecting the environment, there's a new emphasis on designing plastics
that will disappear much more quickly.
Broadly speaking, so-called "environmentally friendly" plastics fall into three

Bioplastics made from natural materials such as corn starch

Biodegradable plastics made from traditional petrochemicals, which are
engineered to break down more quickly

Eco/recycled plastics, which are simply plastics made from recycled
plastic materials rather than raw petrochemicals.

We'll look at each of these in turn.

Photo: Some bioplastics can be harmlessly composted. Others leave toxic
residues or plastic fragments behind, making them unsuitable for composting if
your compost is being used to grow food.
The theory behind bioplastics is simple: if we could make plastics from kinder
chemicals to start with, they'd break down more quickly and easily when we got
rid of them. The most familiar bioplastics are made from natural materials such
ascorn starch and sold under such names as EverCorn™and NatureWorks—with
a distinct emphasis on environmental credentials. Some bioplastics look virtually
indistinguishable from traditional petrochemical plastics. Polylactide acid
(PLA)looks and behaves like polyethylene and polypropylene and is now widely
used for food containers. According to NatureWorks, making PLA saves two thirds
the energy you need to make traditional plastics. Unlike traditional plastics and
biodegradable plastics, bioplastics generally do not produce a net increase in
carbon dioxide gas when they break down (because the plants that were used to
make them absorbed the same amount of carbon dioxide to begin with). PLA, for
example, produces almost 70 percent less greenhouse gases when it degrades in
Another good thing about bioplastics is that they're compostable: they decay into
natural materials that blend harmlessly with soil. Some bioplastics can break
down in a matter of weeks. The cornstarch molecules they contain slowly absorb
water and swell up, causing them to break apart into small fragments that
bacteria can digest more readily.
A recipe for PLA bioplastics
1. Take some corn kernels (lots of them).
2. Process and mill them to extract the dextrose (a type of sugar) from their
3. Use fermenting vats to turn the dextrose into lactic acid.
4. In a chemical plant, convert the lactic acid into lactide.
5. Polymerize the lactide to make long-chain molecules of polylactide acid
Biodegradable plastics

If you're in the habit of reading what supermarkets print on their plastic bags,
you may have noticed a lot of environmentally friendly statements appearing
over the last few years. Some stores now use what are described
as photodegradable, oxydegradable, or just biodegradable bags (in practice,
whatever they're called, it often means the same thing). As the name suggests,
these biodegradable plastics contain additives that cause them to decay more
rapidly in the presence of light and oxygen (moisture and heat help too). Unlike
bioplastics, biodegradable plastics are made of normal (petrochemical) plastics
and don't always break down into harmless substances: sometimes they leave
behind a toxic residue and that makes them generally (but not always)
unsuitable for composting.

Photo: A typical message on a biodegradable bag. This one, made from Eco
Film™, is compostable too.
Recycled plastics
One neat solution to the problem of plastic disposal is to recycle old plastic
materials (like used milk bottles) into new ones (such as items of clothing). A
product called ecoplastic is sold as a replacement for wood for use in outdoor
garden furniture and fence posts. Made from high-molecular polyethylene, the
manufacturers boast that it's long-lasting, attractive, relatively cheap, and nice
to look at.

Photo: This "wooden" public bench looks much like any other until you look at
the grain really closely. Then you can see the wood is actually recycled plastic.
The surface texture is convincing, but the giveaway is the ends of the "planks,"
which don't look anything like the grain of wood.
But there are two problems with recycled plastics. First, plastic that's recycled is
generally not used to make the same items the next time around: old recycled
plastic bottles don't go to make new plastic bottles, but lower-grade items such
as plastic benches and fence posts. Second, you can't automatically assume
recycled plastics are better for the environment unless you know they've been
made with a net saving of energy and water, a net reduction in greenhouse gas
emissions, or some other overall benefit to the environment. Keeping waste out
of a landfill and turning it into new things is great, but what if it takes a huge
amount of energy to collect and recycle the plastic—more even than making
brand new plastic products?
Are bioplastics good or bad?
Anything that helps humankind solve the plastics problem has to be a good
thing, right? Unfortunately, environmental issues are never quite so simple.
Actions that seem to help the planet in obvious ways sometimes have major
drawbacks and can do damage in other ways. It's important to see things in the
round to understand whether "environmentally friendly" things are really doing
more harm than good.
Bioplastics and biodegradable plastics have long been controversial.
Manufacturers like to portray them as a magic-bullet solution to the problem of
plastics that won't go away. Bioplastics, for example, are touted as saving 30–80
percent of the greenhouse gas emissions you'd get from normal plastics and they
can give food longer shelf-life in stores. But here are some of the drawbacks:

When some biodegradable plastics decompose in landfills, they produce
methane gas. This is a very powerful greenhouse gas that adds to the
problem of global warming.

Biodegradable plastics and bioplastics don't always readily decompose.
Some need relatively high temperatures and, in some conditions, can still
take many years to break down. Even then, they may leave behind toxic

Bioplastics are made from plants such as corn and maize, so land that
could be used to grow food for the world is being used to "grow plastic"
instead. By 2014, almost a quarter of US grain production is expected to
be turned over to biofuels and bioplastics production, potentially causing a
significant rise in food prices that will hit the poorest people hardest.

Some bioplastics, such as PLA, are made from genetically modified corn.
Most environmentalists consider GM (genetically modified) crops to be
inherently harmful to the environment.

Bioplastics and biodegradable plastics cannot be easily recycled. To most
people, PLA looks very similar to PET (polyethylene terephthalate) but, if
the two are mixed up in a recycling bin, the whole collection becomes

impossible to recycle. There are fears that increasing use of PLA may
undermine existing efforts to recycle plastics.
How to cut down on plastics

Why is life never simple? If you're keen on helping the planet, complications like
this sound completely exasperating. But don't let that put you off. As many
environmental campaigners point out, there are some very simple solutions to
the plastics problem that everyone can bear in mind to make a real difference.
Instead of simply sending your plastics waste for recycling, remember the saying
"Reduce, repair, reuse, recycle". Recycling, though valuable, is only slightly
better than throwing something away: you still have to use energy and water to
recycle things and you probably create toxic waste products as well. It's far
better to reduce our need for plastics in the first place than to have to dispose of
them afterwards.
Photo: Recycling, though sensible, is not always the best option. Generally it's
better to reduce, reuse, and repair if you can and recycle only if you can't do
these things.
You can make a positive difference by actively cutting down on the plastics you
use. For example:

Get a reusable cotton bag and take that with you ever time you go

Buy your fruit and vegetables loose, avoiding the extra plastic on prepackaged items.

Use long-lasting items (such as razors and refillable pens) rather than
disposable ones. It can work out far cheaper in the long run.

If you break something, can you repair it simply and carry on using it? Do
you really have to buy a new one?

Can you give unwanted plastic items a new lease of life? Ice cream tubs
make great storage containers; vending machine cups can be turned into
plant pots; and you can use old plastic supermarket bags for holding your

When you do have to buy new things, why not buy ones made from
recycled materials? By helping to create a market for recycled products,
you encourage more manufacturers to recycle.

One day, we may have perfect plastics that break down in a trice. Until then,
let's be smarter about how we use plastics and how we get rid of them when
we've finished with them.

Chemical compound
Written by: The Editors of Encyclopædia Britannica






Alternate titles: dibenzo-p-dioxin; polychlorinated dibenzodioxin; TCDD
Read More:

organohalogen compound



chemical element


tear gas

chemical compound

chloral hydrate

Dioxin, also called polychlorinated dibenzodioxin, any of a group of
aromatichydrocarbon compounds known to be environmental pollutants that are
generated as undesirable by-products in the manufacture
of herbicides, disinfectants, and other agents. In popular terminology, dioxin has
become a synonym for one specific dioxin, 2,3,7,8-tetrachlorodibenzo-paradioxin (2,3,7,8-TCDD).

Chemical characteristics and production
The family of dioxins is characterized chemically by the presence of
two benzenerings connected by a pair of oxygen atoms. Each of the
eight carbon atoms on the rings that are not bonded to oxygen can bind
with hydrogen atoms or atoms of other elements. By convention these positions
are assigned the numbers 1 through 4 and 6 through 9. The more toxic dioxins
carry chlorine atoms at these positions, and the best-known one has chlorine
atoms at the 2,3,7, and 8 positions. This isomer—2,3,7,8-TCDD—is extremely
stable chemically. It is virtually insoluble in water and in most organic
compounds but is soluble in oils. It is this combination of properties that allows
this dioxin in soil to resist dilution with rainwater and causes it to seek and enter
fatty tissue in the body if it is absorbed.
Dioxin serves no useful purpose but is formed as an undesirable by-product
during the synthesis of 2,4,5-trichlorophenol and some other useful compounds.
The chemical 2,4,5-trichlorophenol serves as a raw material for making the
herbicides Silvex (fenoprop) and 2,4,5-T (2,4,5-trichlorophenoxyacetic acid). The
latter is a major active ingredient of Agent Orange, a defoliant formerly used in
Vietnam by the U.S. military and in the United Statesto kill unwanted vegetation.
This 2,4,5-trichlorophenol is used in the production of hexachlorophene, an
antibacterial agent formerly used in deodorants and soaps.
Toxicity in humans
The recognition in the early 1980s that residential sites at Times Beach and
elsewhere inMissouri, U.S., had been contaminated by improper disposal
of chemical wastescontaining 2,3,7,8-TCDD led to intense public scrutiny of its
possible toxic effects. Toxicologists concluded from studies on laboratory animals
that TCDD is a persistent toxin, and they recommended that soil levels in excess
of one part per billion might constitute a health risk to humans. Animal studies
indicated that human exposure to the chemical might be associated with
muscular dysfunction, inflammation, impotence, birth defects, genetic mutations,
and nervous system disorders. Those investigations also suggested a potential
link between exposure to TCDD and the development of variouscancers in
Although the actual physiological effects of TCDD toxicity in humans remain
a matter of debate, in 1997 the International Agency for Research on Cancer
(IARC) upgraded the classification of TCDD from a Group 2B
possible carcinogen (cancer-causing substance) in humans to a Group 1 known
carcinogen in humans. The upgrade came after consideration of extensive

epidemiological studies of TCDD carcinogenicity in humans, in which chronic
exposure to high levels of the chemical was found to be associated with an
increase in overall cancer mortality. The data from those studies did not link
TCDD exposure directly to the development of any specific type of cancer. Typical
exposure to TCDD appears to be less of a carcinogenic risk than similar exposure
to asbestos, radon, or cigarette smoke. Among humans, short-term exposure to
high levels of TCDD can cause chloracne, a serious skin rash.
TCDD’s toxicity is derived from the chemical’s ability to bind to a receptor protein
known as the aryl hydrocarbon receptor, which is present inside certain cells
within the body. The resulting TCDD-receptor complex can enter the
cell’s nucleus and bind with its DNA, thereby disrupting the cell’s machinery for
producing proteins. The wide and rather puzzling array of toxic effects induced in
animals by high levels of TCDD are apparently all receptor-mediated responses to
the chemical. Such animals’ immune systems are those most often affected,
being apparently weakened or compromised by TCDD.
Accumulation in the food chain
Dioxins are of particular concern in regard to environmental and human
health because they are persistent environmental pollutants and therefore
accumulate within the food chain. Because of their lipophilic properties, the
chemicals are readily absorbed into fatty tissue, and thus they have a tendency
to accumulate in animals—for example, in fish, as a result of the chemicals’
presence in aquatic environments, and in cattle and otherlivestock, as a result of
the chemicals’ release into terrestrial environments. Consumption of potentially
contaminated foods, such as beef and dairy products, is the primary route for
dioxin entry into the human body. In fact, more than 90 percent of human dioxin
exposure is attributed to dietary ingestion. Once in the human body, dioxins are
absorbed into fat cells, where they persist for long periods of time; the half-life of
dioxin in humans has been estimated to be between 7 and 11 years.
The incineration of dioxins generated as by-products in manufacturing processes
is an effective method for controlling the release of the chemicals into the

What is Dioxin? How to Avoid Toxin Dioxin

Found everywhere, dioxin is public enemy number one. To give you an idea of
how common dioxin exposure is, consider bleached coffee filters. The EPA says

that 40% to 70% of the dioxins contained in bleached coffee filters get
transferred to your coffee. Therefore, the simple routine of using bleached coffee
filters results in a lifetime of unsafe exposure to dioxin.
According to the World Health Organization, dioxins are highly toxic. They cause
reproductive and developmental problems, damage the immune system, disrupt
hormones and cause cancer.
The Skinny Science:
Dioxin is an organic chemical that consists of a pair of benzene rings. Because of
their chemical stability and their ability to be dissolved by fat tissue, they can
exist in the body for years. Highly potent in small quantities, it is measured in
parts per trillion, not the parts per million we usually hear. Dioxins are
categorized as persistent environmental pollutants. This means two things: they
do not degrade in the environment, and they exist indefinitely once released.
Word to the Wise:
Manufacturing processes are the root cause of our dioxin issues today. This
includes smelting, chlorine bleaching of paper pulp, manufacturing of herbicides
and pesticides, and uncontrolled waste incinerators. Sadly they are found
throughout the world, even in hundred-year-old Greenland Sharks that live in
some of the most pristine waters of the Arctic Ocean.
Green your Routine:
How do you avoid this seemingly omnipresent substance? A major source of
dioxin exposure is eating animal products, because of dioxin's ability to persist in
fats. In addition to changing your diet, here are some other strategies you can

Avoid eating animal products.

Eat organically grown fruits and vegetables. Pesticide and herbicide
residues found on non-organically grown food harbors dioxin.

When gardening, avoid using pesticides and herbicides that contain

When cleaning, avoid chlorine bleach. It forms dioxin after contact with
organic compounds.

In personal care products, avoid triclosan, an antibacterial agent. It
degrades into dioxin.

With coffee supplies, use unbleached coffee filters, metal filters, or a
French press. Dioxin is a by-product of the bleaching process.

Avoid bleached paper products like disposable diapers, napkins, tissue
and paper towels.

Prevention is the Best Cure:
Because of the ubiquitous nature of dioxin, the usual prevention advice is
challenging. Dioxin is present in every aspect of life: water, air, soil and food.
That said, dioxin concentrations vary, so the best advice may be to avoid foods
with the highest concentration of dioxins. Since dioxin accumulates in fat -- in

both our own and the animals we eat — people with diets high in vegetables and
low in animal products have lower dioxin levels.
High dioxin level foods:

dairy products




Low dioxin level foods:



Extra Tidbits:

Alternative names quick list: DLC (dioxin-like compound), TCDD (the most
toxic dioxin), PCDD, PCDF, and some dioxin-like PCBs.

Dioxin is categorized as one of the "dirty dozen" chemicals.

Dioxin made headlines when it was used in an assassination attempt to
poison former Ukrainian president, Viktor Yushchenko, leaving him
severely disfigured.

Agent Orange made dioxin infamous in the 1980s.

For more information, check out these sources: United States Department
of Agriculture, Environmental Protection Agency.

As always, stay informed and green your routine to what fits you best.

Dioxins & why you dont want to be burning plastic
02 June, 2008 / by polythenepam / in 04.1 PLASTIC PROBLEMS
The image shows plastic trash being burnt in Khatmandu
So, is it safe to burn plastic?
Well it never burns easily – it melts and bubbles. It will burn eventually but you
have to keep heating it – click here if you want to know why.
And, when you do set fire to plastic it gives off a terrible smell – at least in my
experience, as a child, playing round the back of the derelict garages I hasten to
>But is it bad for you? It could be lethal.
The smell according to the naked scientist could be anything. They say
“There are lots of different plastics, and they will give off lots of different vapours
when they decompose.
It could be just a simple hydrocarbon, or it could contain cyanides, or PCB’s, or
lots of other substances. Without knowing what the plastic was … would be
difficult to know what are the likely volatiles it would create…. volatiles given off
from plastics in house fires are a major cause of death.”
PCBs? – thats a dioxin and dioxins are nasty! Eeek!
So, to conclude, it depends on the plastic then?

Setting fire to plastic filled ditches
Yes it is apparently safe to burn polythene – it can even be reprocessed as
briquettes to make a very efficient fuel (ifenergy).
But it’s a big NO if its a halogenated plastics, i.e one of those made from
chlorine or fluorine
Halogenated plastics include:
Chlorine based plastics:
Chlorinated polyethylene (CPE)
Chlorinated polyvinyl chloride (CPVC)
Chlorosulfonated polyethylene (CSPE)
Polychloroprene (CR or chloroprene rubber, marketed under the brand name of
Fluorine based plastics:
Fluorinated ethylene propylene (FEP)
Burning these plastics can release dioxins. Dioxins are unintentionally, but
unavoidably produced during the manufacture of materials containing chlorine,
including PVC and other chlorinated plastic feedstocks.
Dioxin is a known human carcinogen and the most potent synthetic carcinogen
ever tested in laboratory animals. A characterization by the National Institute of
Standards and Technology of cancer causing potential evaluated dioxin as over
10,000 times more potent than the next highest chemical (diethanol amine), half
a million times more than arsenic and a million or more times greater than all
The World Health Organization said
“Once dioxins have entered the environment or body, they are there to stay due
to their uncanny ability to dissolve in fats and to their rock-solid chemical

That is because dioxins are classed as one of the persistant organic pollutants,
POPs, also known as as PBTs (Persistent, Bioaccumulative and Toxic)
or TOMPs (Toxic Organic Micro Pollutants.)
POPs are a small set of toxic chemicals that remain intact in the environment for
long periods and accumulate in the fatty tissues of animals. They are extremely
toxic and cause all manner of illnesses. You can find out more about POPS here
The Uk Government states on their website
Burning plastic, rubber or painted materials creates poisonous fumes and can
have damaging health effects for people who have asthmatic or heart conditions.
This is covered under the Environmental Protection Act 1990.
Environmental Protection Act 1990
Its best not to be burning plastic on an open fire unless you know exactly what it
is made up of.
While there are some plastics that are supposed to be safe to burn, personally I
won’t be burning plastic on my bonfire.
But is it safe to send off to my local waste disposal plant where they burn
it in an incinerator?
It is claimed that all plastics can be burnt safely in the modern industrial
incinerators – but only those built to high specifications.
Opinions vary wildly as to wether this is the case with environmentalists saying
we are poisoning the very air that we breathe.
Many of these plants generate electricity from the heat produced so in effect the
plastic is recycled.
The resulting ash from incineration plants has to be disposed of and so presnets
yet another waste disposal challenge.
For more information go to
Waste Plastic Blogspot about the technology behind waste incinerators.
Zero Waste America a crtiqua of waste incinerators.
Burning Bins the problems of trash being burnt on open fires
The quality of plasticity is one that had been used to great effect in the crafts of
metallurgy and ceramics. The use of the word plastics as a collective noun,
however, refers not so much to the traditional materials employed in these crafts
as to new substances produced by chemical reactions and molded or pressed to
take a permanent rigid shape. The first such material to be manufactured
was Parkesine, developed by the British inventor Alexander Parkes. Parkesine,
made from a mixture of chloroform and castor oil, was “a substance hard as
horn, but as flexible as leather, capable of being cast or stamped, painted, dyed
or carved.” The words are from a guide to the International Exhibition of 1862 in

London, at which Parkesine won a bronze medal for its inventor. It was soon
followed by other plastics, but—apart from celluloid, a cellulose nitrate
composition using camphor as a solvent and produced in solid form (as imitation
horn for billiard balls) and in sheets (for men’s collars and photographic film)—
these had little commercial success until the 20th century.
The early plastics relied upon the large molecules in cellulose, usually derived
from wood pulp. Leo H. Baekeland, a Belgian American inventor, introduced a
new class of large molecules when he took out his patent for Bakelite in 1909.
Bakelite is made by the reaction between formaldehyde and phenolic materials
at high temperatures; the substance is hard, infusible, and chemically resistant
(the type known as thermosetting plastic). As a nonconductor of electricity, it
proved to be exceptionally useful for all sorts of electrical appliances. The
success of Bakelite gave a great impetus to the plastics industry, to the study
of coal tar derivatives and other hydrocarbon compounds, and to the theoretical
understanding of the structure of complex molecules. This activity led to new
dyestuffs and detergents, but it also led to the successful manipulation of
molecules to produce materials with particular qualities such as hardness or
flexibility. Techniques were devised, often requiring catalysts and elaborate
equipment, to secure these polymers—that is, complex molecules produced by
the aggregation of simpler structures. Linear polymers give strong fibres, filmforming polymers have been useful in paints, and mass polymers have formed
solid plastics.
The possibility of creating artificial fibres was another 19th-century discovery
that did not become commercially significant until the 20th century, when such
fibres were developed alongside the solid plastics to which they are closely
related. The first artificial textiles had been made from rayon, a silklike material
produced by extruding a solution of nitrocellulose in acetic acid into a
coagulating bath of alcohol, and various other cellulosic materials were used in
this way. But later research, exploiting the polymerization techniques being used
in solid plastics, culminated in the production of nylon just before the outbreak of
World War II.Nylon consists of long chains of carbon-based molecules, giving
fibres of unprecedented strength and flexibility. It is formed by melting the
component materials and extruding them; the strength of the fibre is greatly
increased by stretching it when cold. Nylon was developed with the women’s
stocking market in mind, but the conditions of war gave it an opportunity to
demonstrate its versatility and reliability as parachute fabric and towlines. This
and other synthetic fibres became generally available only after the war.
The chemical industry in the 20th century put a wide range of new materials at
the disposal of society. It also succeeded in replacing natural sources of some
materials. An important example of this is the manufacture of artificial rubber to
meet a world demand far in excess of that which could be met by the existing
rubber plantations. This technique was pioneered in Germany during World War I.
In this effort, as in the development of other materials such as high explosives
and dyestuffs, the consistent German investment in scientific and technical
education paid dividends, for advances in all these fields of chemical
manufacturing were prepared by careful research in the laboratory.

Cell wall plastics such as lignin, cutin, and suberin all contain a variety of organic
compounds cross-linked into tight three-dimensional networks that strengthen
cell walls and make them more resistant to fungal and bacterial attack. Lignin is
the general name for a diverse group of polymers of aromatic alcohols.
Deposited mostly in secondary cell walls and providing the rigidity of terrestrial
vascular plants, it accounts for up to 30 percent of a plant’s dry weight. The
diversity of cross-links between the polymers—and the resulting tightness—
makes lignin a formidable barrier to the penetration of most microbes.
Cutin and suberin are complex biopolyesters composed of fatty acids and
aromatic compounds. Cutin is the major component of the cuticle, the waxy,
water-repelling surface layer of cell walls exposed to the environment
aboveground. By reducing the wetability of leaves and stems—and thereby
affecting the ability of fungal spores to germinate—it plays an important part in
the defense strategy of plants. Suberin serves with waxes as a surface barrier of
underground parts. Its synthesis is also stimulated in cells close to wounds,
thereby sealing off the wound surfaces and protecting underlying cells from
Plastic pollution, accumulation in the environment of manmade plastic products to the point where they create problems for wildlife and
their habitats as well as for human populations. In 1907 the invention
of Bakelite brought about a revolution in materials by introducing truly
synthetic plastic resins into world commerce. By the end of the 20th century,
however, plastics were found to be persistent polluters of many environmental
niches, from Mount Everest to the bottom of the sea. Whether being mistaken
for food by animals, flooding low-lying areas by clogging drainage systems, or
simply causing significant aesthetic blight, plastics have attracted increasing
attention as a large-scale pollutant.




The problem of plastics
Plastic is a polymeric material—that is, a material whose molecules are very
large, often resembling long chains made up of a seemingly endless series of
interconnected links. Natural polymers such as rubber and silk exist in
abundance, but nature’s “plastics” have not been implicated in
environmental pollution, because they do not persist in the environment. Today,
however, the average consumer comes into daily contact with all kinds of manmade plastic materials that have been developed specifically to defeat natural
decay processes—materials derived mainly from petroleum that can be molded,
cast, spun, or applied as a coating. Since synthetic plastics are largely
nonbiodegradable, they tend to persist in natural environments. Moreover, many
lightweight, single-use plastic products and packaging materials, which account
for approximately 50 percent of all plastics produced, are not deposited in
containers for subsequent removal to landfills,recycling centres, or incinerators.
Instead, they are improperly disposed of at or near the location where they end
their usefulness to the consumer. Dropped on the ground, thrown out of a car
window, heaped onto an already full rubbish bin, or inadvertently carried off by a
gust of wind, they immediately begin to pollute the environment. Indeed,
landscapes littered by plastic packaging have become common in many parts of
the world. (Illegal dumping of plastic and overflowing of containment structures
also play a role.) Studies from around the world have not shown any particular
country or demographic group to be most responsible, though population centres
generate the most litter. The causes and effects of plastic pollution are truly

According to the trade association PlasticsEurope, world plastic production grew
from some 1.5 million tons in 1950 to an estimated 275 million tons in 2010;
some 4 million to 12 million tons is discarded into the oceans annually by
countries with ocean coastlines. Compared with materials in common use in the
first half of the 20th century, such as glass, paper, iron, and aluminum, plastics
have a low recovery rate. That is, they are relatively inefficient to reuse as
recycled scrap in the manufacturing process, due to significant processing
difficulties such as a low melting point, which prevents contaminants from being
driven off during heating and reprocessing. Most recycled plastics are subsidized
below the cost of raw materials by various deposit schemes, or their recycling is
simply mandated by government regulations. Recycling rates vary dramatically
from country to country, with only northern European countries obtaining rates
greater than 50 percent. In any case, recycling does not really address plastic
pollution, since recycled plastic is “properly” disposed of, whereas plastic
pollution comes from improper disposal.
Plastic, polymeric material that has the capability of being molded or shaped,
usually by the application of heat and pressure. This property of plasticity, often
found in combination with other special properties such as low density, low
electrical conductivity, transparency, and toughness, allows plastics to be made
into a great variety of products. These include tough and lightweight beverage
bottles made of polyethylene terephthalate (PET), flexible garden hoses made
of polyvinyl chloride (PVC), insulating food containers made of
foamed polystyrene, and shatterproof windows made of polymethyl





In this article a brief review of the essential properties of plastics is provided,
followed by a more detailed description of their processing into useful products
and subsequent recycling. For a fuller understanding of the materials from which
plastics are made, see chemistry of industrial polymers.
The composition, structure, and properties of plastics
Many of the chemical names of the polymers employed as plastics have become
familiar to consumers, although some are better known by their abbreviations or
trade names. Thus, polyethylene terephthalate and polyvinyl chloride are
commonly referred to as PET and PVC, while foamed polystyrene and polymethyl
methacrylate are known by their trademarked names, Styrofoam and Plexiglas
(or Perspex).
Industrial fabricators of plastic products tend to think of plastics as either
“commodity” resins or “specialty” resins. (The term resin dates from the early
years of the plastics industry; it originally referred to naturally occurring
amorphous solids such as shellac and rosin.) Commodity resins are plastics that
are produced at high volume and low cost for the most common disposable items
and durable goods. They are represented chiefly by polyethylene, polypropylene,
polyvinyl chloride, and polystyrene. Specialty resins are plastics whose properties
are tailored to specific applications and that are produced at low volume and
higher cost. Among this group are the so-called engineering plastics, or
engineering resins, which are plastics that can compete with die-cast metals
in plumbing, hardware, and automotive applications. Important engineering
plastics, less familiar to consumers than the commodity plastics listed above,
are polyacetal, polyamide (particularly those known by the trade
name nylon), polytetrafluoroethylene (trademark Teflon),polycarbonate,
polyphenylene sulfide, epoxy, and polyetheretherketone. Another member of the
specialty resins is thermoplastic elastomers, polymers that have the elastic
properties of rubber yet can be molded repeatedly upon heating. Thermoplastic
elastomers are described in the article elastomer.
Plastics also can be divided into two distinct categories on the basis of their
chemical composition. One category is plastics that are made up of polymers
having only aliphatic (linear) carbon atoms in their backbone chains. All the
commodity plastics listed above fall into this category. The structure
of polypropylene can serve as an example; here attached to every other carbon
atom is a pendant methyl group (CH3):

The other category of plastics is made up of heterochain polymers. These
compounds contain atoms such as oxygen, nitrogen, or sulfur in their backbone
chains, in addition to carbon. Most of the engineering plastics listed above are

composed of heterochain polymers. An example would be polycarbonate, whose
molecules contain two aromatic (benzene) rings:

The distinction between carbon-chain and heterochain polymers is reflected in
the table, in which selected properties and applications of the most important
carbon-chain and heterochain plastics are shown and from which links are
provided directly to entries that describe these materials in greater detail. It is
important to note that for each polymer type listed in the table there can be
many subtypes, since any of a dozen industrial producers of any polymer can
offer 20 or 30 different variations for use in specific applications. For this reason
the properties indicated in the table must be taken as approximations.
Properties and applications of commercially important plastics


degree of



at 1.8 MPa

polyethylene (HDPE)





polyethylene (LDPE)





polypropylene (PP)





polystyrene (PS)








polyvinyl chloride,
unplasticized (PVC)




methacrylate (PMMA)




polymer family and


ne (PTFE)





terephthalate (PET)





polycarbonate (PC)














polyphenylene sulfide





cellulose diacetate





(nylon 6)













phenol formaldehyde




urea and melamine








polymer family and


at break


typical products and




polyethylene (HDPE)




milk bottles, wire and cable
insulation, toys

polyethylene (LDPE)




packaging film, grocery bags,
agricultural mulch

polypropylene (PP)




bottles, food containers, toys

polystyrene (PS)




eating utensils, foamed food





appliance housings, helmets,
pipe fittings

polyvinyl chloride,
unplasticized (PVC)




pipe, conduit, home siding,
window frames

methacrylate (PMMA)




impact-resistant windows,
skylights, canopies

ne (PTFE)




self-lubricated bearings,
nonstick cookware

terephthalate (PET)




transparent bottles, recording

polycarbonate (PC)




compact discs, safety glasses,
sporting goods





bearings, gears, shower
heads, zippers





machine, automotive, and
aerospace parts

polyphenylene sulfide




machine parts, appliances,
electrical equipment

cellulose diacetate




photographic film

(nylon 6)




bearings, pulleys, gears







boat hulls, automobile panels





laminated circuit boards,
flooring, aircraft parts

phenol formaldehyde




electrical connectors,
appliance handles

urea and melamine




countertops, dinnerware





flexible and rigid foams for
upholstery, insulation

*All values shown are for glass-fibre-reinforced samples (except for
For the purposes of this article, plastics are primarily defined not on the basis of
their chemical composition but on the basis of their engineering behaviour. More
specifically, they are defined as either thermoplastic resins or thermosetting
The polymers
Polymers are chemical compounds whose molecules are very large, often
resembling long chains made up of a seemingly endless series of interconnected
links. The size of these molecules, as is explained in chemistry of industrial
polymers, is extraordinary, ranging in the thousands and even millions of atomic
mass units (as opposed to the tens of atomic mass units commonly found in
other chemical compounds). The size of the molecules, together with their
physical state and the structures that they adopt, are the principal causes of the
unique properties associated with plastics—including the ability to be molded
and shaped.
As mentioned above, polymers that are classified as plastics can be divided into
two major categories: thermoplastics and thermosets. Thermoplastics such as
polyethylene and polystyrene are capable of being molded and remolded
repeatedly. Thus, a foamed-polystyrene cup can be heated and reshaped into a
new form—for instance, a dish. The polymer structure associated with
thermoplastics is that of individual molecules that are separate from one another
and flow past one another. The molecules may have low or extremely
high molecular weight, and they may be branched or linear in structure, but the
essential feature is that of separability and consequent mobility.

Thermosets, on the other hand, cannot be reprocessed upon reheating. During
their initial processing, thermosetting resins undergo a chemical reaction that
results in an infusible, insoluble network. Essentially, the entire heated, finished
article becomes one large molecule. For example, the epoxy polymer used in
making a fibre-reinforced laminate for a golf club undergoes a cross-linking
reaction when it is molded at a high temperature. Subsequent application of heat
does not soften the material to the point where it can be reworked and indeed
may serve only to break it down.

figureThe plastic behaviour of polymers is also influenced by their morphology,
or arrangement of molecules on a large scale. Stated simply, polymer
morphologies are either amorphous or crystalline. Amorphous molecules are
arranged randomly and are intertwined, whereas crystalline molecules are
arranged closely and in a discernible order. Most thermosets are amorphous,
while thermoplastics may be amorphous or semicrystalline. Semicrystalline
materials display crystalline regions, called crystallites, within an amorphous





By definition, thermoplastic materials retain their molded shapes up to a certain
temperature, which is set by the glass transition temperature or the melting
temperature of the particular polymer. Below a certain temperature, known as
the glass transition temperature (Tg), the molecules of a polymer material are
frozen in what is known as the glassy state; there is little or no movement of
molecules past one another, and the material is stiff and even brittle.
Above Tg the amorphous parts of the polymer enter the rubbery state, in which
the molecules display increased mobility and the material becomes plastic and
even elastic (that is, able to be stretched). In the case of noncrystalline polymers
such as polystyrene, raising the temperature further leads directly to the liquid
state. On the other hand, for partly crystalline polymers such as low-density
polyethylene or polyethylene terephthalate, the liquid state is not reached until
the melting temperature (Tm) is passed. Beyond this point the crystalline regions
are no longer stable, and the rubbery or liquid polymers can be molded or
extruded. Thermosets, which do not melt upon reheating, can be dimensionally
stable up to a temperature at which chemical degradation begins.
The physical state and morphology of a polymer have a strong influence on its
mechanical properties. A simple measure of the differences produced in
mechanical behaviour is the elongation that occurs when a plastic is loaded
(stressed) in tension. A glassy polymer such as polystyrene is quite stiff, showing
a high ratio of initial stress to initial elongation. On the other hand, polyethylene
and polypropylene, two highly crystalline plastics, are usable as films and
molded objects because at room temperature their amorphous regions are well
above their glass transition temperatures. The leathery toughness of these
polymers above Tg results from the crystalline regions that exist in an
amorphous, rubbery matrix. Elongations of 100 to 1,000 percent are possible
with these plastics. In PET, another semicrystalline plastic, the crystalline
portions exist in a glassy matrix because the Tg of PET is above room
temperature. This gives the material a stiffness and high dimensional stability
under stress that are of great importance in beverage bottles and recording tape.
Almost all plastics exhibit some elongation on being stressed that is not
recovered when the stress is removed. This behaviour, known as “creep,” may
be very small for a plastic that is well below its Tg, but it can be significant for a
partly crystalline plastic that is above Tg.
The most commonly specified mechanical properties of polymers include
stiffness and breaking stress, quantified in the table of properties and
applications as flexural modulus and tensile strength. Another important
property is toughness, which is the energy absorbed by a polymer before failure
—often as the result of a sudden impact. Repeated applications of stress well
below the tensile strength of a plastic may result in fatigue failure.
Most plastics are poor conductors of heat; conductivity can be reduced even
further by incorporating a gas (usually air) into the material. For instance,
foamed polystyrene used in cups for hot beverages has a thermal conductivity
about one-quarter that of the unfoamed polymer. Plastics also are electrical
insulators unless especially designed for conductivity. Besides conductivity,
important electrical properties include dielectric strength (resistance to

breakdown at high voltages) anddielectric loss (a measure of the energy
dissipated as heat when an alternating current is applied).
In many plastic products, the polymer is only one constituent. In order to arrive
at a set of properties appropriate to the product, the polymer is almost always
combined with other ingredients, or additives, which are mixed in during
processing and fabrication. Among these additives are plasticizers, colorants,
reinforcements, and stabilizers. These are described in turn below.
Plasticizers are used to change the Tg of a polymer. Polyvinyl chloride (PVC), for
instance, is often mixed with nonvolatile liquids for this reason. Vinyl siding used
on homes requires an unplasticized, rigid PVC with a Tg of 85 to 90 °C (185 to
195 °F). A PVC garden hose, on the other hand, should remain flexible even at 0
°C (32 °F). A mixture of 30 parts di(2-ethylhexyl) phthalate (also called dioctyl
phthalate, or DOP) with 70 parts PVC will have a Tg of about −10 °C (15 °F),
making it suitable for use as a garden hose.
Although other polymers can be plasticized, PVC is unique in accepting and
retaining plasticizers of widely varying chemical composition and molecular size.
Theplasticizer may also change the flammability, odour, biodegradability, and
cost of the finished product.
For most consumer applications, plastics are coloured. The ease with which
colour is incorporated throughout a molded article is an advantage of plastics
over metals and ceramics, which depend on coatings for colour. Popular
pigments for colouring plastics include titanium dioxide and zinc oxide (white),
carbon (black), and various other inorganic oxides such as iron and chromium.
Organic compounds can be used to add colour either as pigments (insoluble) or
as dyes (soluble).
Reinforcements, as the name suggests, are used to enhance the mechanical
properties of a plastic. Finely divided silica, carbon black, talc, mica, and calcium
carbonate, as well as short fibres of a variety of materials, can be incorporated
as particulate fillers. (The use of long or even continuous fibres as reinforcement,
especially with thermosets, is described below in Fibre reinforcement.)
Incorporating large amounts of particulate filler during the making of plastics
such as polypropylene and polyethylene can increase their stiffness. The effect is
less dramatic when temperature is below the polymer’s Tg.





In order for a plastic to have a long and useful life in any application, the
properties of that plastic should change as little as possible with time. Stabilizers
are added, usually in small quantities, to counter the effects of aging.
Because all carbon-based polymers are subject to oxidation, the most common
stabilizers are antioxidants. Hindered phenols and tertiary amines are used in
plastics in concentrations as low as a few parts per million. For example,
butylated hydroxytoluene (BHT) is used in polyolefin packaging films for foods
and pharmaceuticals. PVC requires the addition of heat stabilizers in order to
reduce dehydrohalogenation (loss of hydrogen chloride [HCl]) at processing
temperatures. Zinc and calcium soaps, organotin mercaptides, and organic
phosphites are among the many additives found to be effective. Other stabilizers
are designed specifically to reduce degradation by sunlight, ozone, and biological
The processing and fabrication of plastics
The processing of raw materials into usable forms is termed fabrication or
conversion. An example from the plastics industry would be the conversion of
plastic pellets into films or the conversion of films into food containers. In this
section the mixing, forming, finishing, and fibre reinforcing of plastics are
described in turn.
The first step in most plastic fabrication procedures is compounding,
the mixingtogether of various raw materials in proportions according to a specific
recipe. Most often the plastic resins are supplied to the fabricator as cylindrical
pellets (several millimetres in diameter and length) or as flakes and powders.
Other forms include viscous liquids, solutions, and suspensions.

Mixing liquids with other ingredients may be done in conventional stirred tanks,
but certain operations demand special machinery. Dry blending refers to the
mixing of dry ingredients prior to further use, as in mixtures of pigments,
stabilizers, or reinforcements. However, polyvinyl chloride (PVC) as a porous
powder can be combined with a liquid plasticizer in an agitated trough called a
ribbon blender or in a tumbling container. This process also is called dry
blending, because the liquid penetrates the pores of the resin, and the final
mixture, containing as much as 50 percent plasticizer, is still a free-flowing
powder that appears to be dry.
The workhorse mixer of the plastics and rubber industries is the internal mixer, in
which heat and pressure are applied simultaneously. The Banbury
mixer resembles a robust dough mixer in that two interrupted spiral rotors move
in opposite directions at 30 to 40 rotations per minute. The shearing action is
intense, and the power input can be as high as 1,200 kilowatts for a 250-kg (550pound) batch of molten resin with finely divided pigment.
In some cases, mixing may be integrated with the extrusion or molding step, as
in twin-screw extruders.
The process of forming plastics into various shapes typically involves the steps of
melting, shaping, and solidifying. As an example, polyethylene pellets can be
heated above Tm, placed in a mold under pressure, and cooled to below Tm in
order to make the final product dimensionally stable. Thermoplastics in general
are solidified by cooling below Tg or Tm. Thermosets are solidified by heating in
order to carry out the chemical reactions necessary for network formation.
In extrusion, a melted polymer is forced through an orifice with a particular cross
section (the die), and a continuous shape is formed with a constant cross section
similar to that of the orifice. Although thermosets can be extruded and crosslinked by heating the extrudate, thermoplastics that are extruded and solidified
by cooling are much more common. Among the products that can be produced
by extrusion arefilm, sheet, tubing, pipes, insulation, and home siding. In each
case the profile is determined by the die geometry, and solidification is by
figureMost plastic grocery bags and similar items are made by the continuous
extrusion of tubing. In blow extrusion, the tube is expanded before being cooled
by being made to flow around a massive air bubble. Air is prevented from
escaping from the bubble by collapsing the film on the other side of the bubble.
For some applications, laminated structures may be made by extruding more
than one material at the same time through the same die or through multiple
dies. Multilayer films are useful since the outer layers may contribute strength
and moisture resistance while an inner layer may control oxygen permeability—
an important factor in food packaging. The layered films may be formed through
blow extrusion, or extrudates from three machines may be pressed together in a
die block to form a three-layer flat sheet that is subsequently cooled by contact
with a chilled roll.

The flow through a die in extrusion always results in some orientation of the
polymer molecules. Orientation may be increased by drawing—that is, pulling on
the extrudate in the direction of polymer flow or in some other direction either
before or after partial solidification. In the blow extrusion process, polymer
molecules are oriented around the circumference of the bag as well as along its
length, resulting in a biaxially oriented structure that often has superior
mechanical properties over the unoriented material.
In the simplest form of compression molding, a molding powder (or pellets, which
are also sometimes called molding powder) is heated and at the same time
compressed into a specific shape. In the case of a thermoset, the melting must
be rapid, since a network starts to form immediately, and it is essential for the
melt to fill the mold completely before solidification progresses to the point
where flow stops. The highly cross-linked molded article can be removed without
cooling the mold. Adding the next charge to the mold is facilitated by
compressing the exact required amount of cold molding powder into a preformed
“biscuit.” Also, the biscuit can be preheated by microwave energy to near the
reaction temperature before it is placed in the mold cavity. A typical heater,
superficially resembling a microwave oven, may apply as much as 10 kilovolts at
a frequency of one megahertz. Commercial molding machines use high pressures
and temperatures to shorten the cycle time for each molding. The molded article
is pushed out of the cavity by the action of ejector pins, which operate
automatically when the mold is opened.





In some cases, pushing the resin into the mold before it has liquefied may cause
undue stresses on other parts. For example, metal inserts to be molded into a
plastic electrical connector may be bent out of position. This problem is solved
by transfer molding, in which the resin is liquefied in one chamber and then
transferred to the mold cavity.
In one form of compression molding, a layer of reinforcing material may be laid
down before the resin is introduced. The heat and pressure not only form the
mass into the desired shape but also combine the reinforcement and resin into
an intimately bound form. When flat plates are used as the mold, sheets of
various materials can be molded together to form a laminated sheet.
Ordinary plywood is an example of a thermoset-bound laminate. In plywood,
layers of wood are both adhered to one another and impregnated by a thermoset
such as urea-formaldehyde, which forms a network on heating.
It is usually slow and inefficient to mold thermoplastics using the compression
molding techniques described above. In particular, it is necessary to cool a
thermoplastic part before removing it from the mold, and this requires that the
mass of metal making up the mold also be cooled and then reheated for each
part. Injection molding is a method of overcoming this inefficiency. Injection
molding resembles transfer molding in that the liquefying of the resin and the
regulating of its flow is carried out in a part of the apparatus that remains hot,
while the shaping and cooling is carried out in a part that remains cool. In
a reciprocating screw injection molding machine, material flows under gravity
from the hopper onto a turning screw. The mechanical energy supplied by the
screw, together with auxiliary heaters, converts the resin into a molten state. At
the same time the screw retracts toward the hopper end. When a sufficient
amount of resin is melted, the screw moves forward, acting as a ram and forcing
the polymer melt through a gate into the cooled mold. Once the plastic has
solidified in the mold, the mold is unclamped and opened, and the part is pushed
from the mold by automatic ejector pins. The mold is then closed and clamped,
and the screw turns and retracts again to repeat the cycle of liquefying a new
increment of resin. For small parts, cycles can be as rapid as several injections
per minute.
One type of network-forming thermoset, polyurethane, is molded into parts such
as automobile bumpers and inside panels through a process known as reaction
injection molding, or RIM. The two liquid precursors of a polyurethane are a
multifunctional isocyanate and a prepolymer, a low-molecularweight polyether orpolyester bearing a multiplicity of reactive end-groups such
as hydroxyl, amine, oramide. In the presence of a catalyst such as a tin soap, the
two reactants rapidly form a network joined mainly by urethane groups. The
reaction takes place so rapidly that the two precursors have to be combined in a
special mixing head and immediately introduced into the mold. However, once in

the mold, the product requires very little pressure to fill and conform to the mold
—especially since a small amount of gas is evolved in the injection process,
expanding the polymer volume and reducing resistance to flow. The low molding
pressures allow relatively lightweight and inexpensive molds to be used, even
when large items such as bumper assemblies or refrigerator doors are formed.
The popularity of thermoplastic containers for products previously marketed in
glass is due in no small part to the development of blow molding. In this
technique, a thermoplastic hollow tube, the parison, is formed by injection
molding or extrusion. In heated form, the tube is sealed at one end and then
blown up like a balloon. The expansion is carried out in a split mold with a cold
surface; as the thermoplastic encounters the surface, it cools and becomes
dimensionally stable. The parison itself can be programmed as it is formed with
varying wall thickness along its length, so that, when it is expanded in the mold,
the final wall thickness will be controlled at corners and other critical locations. In
the process of expansion both in diameter and length (stretch blow molding), the
polymer is biaxially oriented, resulting in enhanced strength and, in the case
of polyethylene terephthalate (PET) particularly, enhanced crystallinity.





Blow molding has been employed to produce bottles
of polyethylene,polypropylene, polystyrene, polycarbonate, PVC, and PET for
domestic consumer products. It also has been used to produce fuel tanks for
automobiles. In the case of a high-density-polyethylene tank, the blown article
may be further treated with sulfur trioxide in order to improve the resistance to
swelling or permeation by gasoline.
Not every forming process requires high pressures. If the material to be molded
is already a stable liquid, simply pouring (casting) the liquid into a mold may
suffice. Since the mold need not be massive, even the cyclical heating and
cooling for a thermoplastic is efficiently done.
One example of a cast thermoplastic is a suspension of finely divided, lowporosity PVC particles in a plasticizer such as dioctyl phthalate (DOP). This
suspension forms a free-flowing liquid (a plastisol) that is stable for months.
However, if the suspension (for instance, 60 parts PVC and 40 parts plasticizer) is
heated to 180 °C (356 °F) for five minutes, the PVC and plasticizer will form a
homogeneous gel that will not separate into its components when cooled back to
room temperature. A very realistic insect or fishing worm can be cast from
a plastisol using inexpensive molds and a cycle requiring only minutes. In
addition, when a mold in the shape of a hand is dipped into a plastisol and then
removed, subsequent heating will produce a glove that can be stripped from the
mold after cooling.
Thermoset materials can also be cast. For example, a mixture of polymer and
multifunctional monomers with initiators can be poured into a heated mold.
Whenpolymerization is complete, the article can be removed from the mold. A
transparent lens can be formed in this way using a diallyl diglycol
carbonate monomer and a free-radical initiator.
In order to make a hollow article, a split mold can be partially filled with a
plastisol or a finely divided polymer powder. Rotation of the mold while heating
converts the liquid or fuses the powder into a continuous film on the interior
surface of the mold. When the mold is cooled and opened, the hollow part can be
removed. Among the articles produced in this manner are many toys such as
balls and dolls.
When a sheet of thermoplastic is heated above its Tg or Tm, it may be capable of
forming a free, flexible membrane as long as the molecular weight is high
enough to support the stretching. In this heated state, the sheet can be pulled
by vacuum into contact with the cold surface of a mold, where it cools to
below Tg or Tm and becomes dimensionally stable in the shape of the mold.
Cups for cold drinks are formed in this way from polystyrene or PET.
Vacuum forming is only one variation of sheet thermoforming. The blow molding
of bottles described above differs from thermoforming only in that a tube rather
than a sheet is the starting form.

Even without heating, some thermoplastics can be formed into new shapes by
the application of sufficient pressure. This technique, called cold molding, has
been used to make margarine cups and other refrigerated food containers from
sheets ofacrylonitrile-butadiene-styrene copolymer.
Foams, also called expanded plastics, possess inherent features that make them
suitable for certain applications. For instance, the thermal conductivity of a foam
is lower than that of the solid polymer. Also, a foamed polymer is more rigid than
the solid polymer for any given weight of the material. Finally, compressive
stresses usually cause foams to collapse while absorbing much energy, an
obvious advantage in protective packaging. Properties such as these can be
tailored to fit various applications by the choice of polymer and by the manner of
foam formation or fabrication. The largest markets for foamed plastics are in
home insulation (polystyrene, polyurethane, phenol formaldehyde) and in
packaging, including various disposable food and drink containers.
Polystyrene pellets can be impregnated with isopentane at room temperature
and modest pressure. When the pellets are heated, they can be made to fuse
together at the same time that the isopentane evaporates, foaming the
polystyrene and cooling the assembly at the same time. Usually the pellets are
prefoamed to some extent before being put into a mold to form a cup or some
form of rigid packaging. The isopentane-impregnated pellets may also be heated
under pressure and extruded, in which case a continuous sheet of foamed
polystyrene is obtained that can be shaped into packaging, dishes, or egg
cartons while it is still warm.





Structural foams can also be produced by injecting nitrogen or some other gas
into a molten thermoplastic such as polystyrene or polypropylene under pressure
in an extruder. Foams produced in this manner are more dense than the ones
described above, but they have excellent strength and rigidity, making them
suitable forfurniture and other architectural uses.
One way of making foams of a variety of thermoplastics is to incorporate a
material that will decompose to generate a gas when heated. To be an
effective blowing agent, the material should decompose at about the molding
temperature of the plastic, decompose over a narrow temperature range, evolve
a large volume of gas, and, of course, be safe to use. One commercial agent
is azodicarbonamide, usually compounded with some other ingredients in order
to modify the decomposition temperature and to aid in dispersion of the agent in
the resin. One mole (116 grams) of azodicarbonamide generates about 39,000
cubic cm of nitrogen and other gases at 200 °C. Thus, 1 gram added to 100
grams of polyethylene can result in foam with a volume of more than 800 cubic
cm. Polymers that can be foamed with blowing agents
include polyethylene, polypropylene, polystyrene, polyamides, and
plasticized PVC.
The rapid reaction of isocyanates with hydroxyl-bearing prepolymers to make
polyurethanes is mentioned above in Reaction injection molding. These materials
also can be foamed by incorporating a volatile liquid, which evaporates under
the heat of reaction and foams the reactive mixture to a high degree. The rigidity
of the network depends on the components chosen, especially the prepolymer.
Hydroxyl-terminated polyethers are often used to prepare flexible foams, which
are used in furniture cushioning. Hydroxyl-terminated polyesters, on the other
hand, are popular for making rigid foams such as those used in custom
packaging of appliances. The good adhesion of polyurethanes to metallic
surfaces has brought about some novel uses, such as filling and making rigid
certain aircraft components (rudders and elevators, for example).
Another rigid thermoset that can be foamed in place is based on phenolformaldehyde resins. The final stage of network formation is brought about by
addition of an acid catalyst in the presence of a volatile liquid.

Some plastics can be joined by welding, in the same manner as metals—PVC and
polyethylene tanks and ductwork being prime examples. More commonly,
surfaces are joined by being brought into contact with one another
and heated by conduction or by dielectric heating. Heat sealing of bags made
from tubes of blow-extruded polyolefins such as polyethylene and polypropylene
usually requires contact with a hot sealing bar. PVC has a high enough dielectric
loss that heat can be generated throughout the material by exposure to a highfrequency, high-voltage electric field.
Rigid thermoplastics and thermosets can be machined by conventional processes
such as drilling, sawing, turning on a lathe, sanding, and other operations. Glassreinforced thermosets are machined into gears, pulleys, and other shapes,
especially when the number of parts does not justify construction of a metal
mold. Various forms can be stamped out (die-cut) from sheets of thermoplastics
and thermosets. The cups made by vacuum forming, for instance, are cut out of
the mother sheet using a sharp die. In the case of a thermoplastic such as
polystyrene, the scrap sheet left over can be reground and remolded.
Although colour may be added in the form of a pigment or dye throughout a
plastic article, there are many applications where a surface coating is valuable
for protective or decorative purposes. The automobile bumpers produced by
reaction injection molding can be painted to match the rest of the body. It is
important in applying coatings to plastics that the solvent used does not cause
swelling of the underlying substrate. For this reason, latex dispersion paints have
found favour, although surface treatment is necessary to provide good bonding
with these materials.
Fibre reinforcement
The term polymer-matrix composite is applied to a number of plastic-based
materials in which several phases are present. It is often used to describe
systems in which a continuous phase (the matrix) is polymeric and another
phase (the reinforcement) has at least one long dimension. The major classes of
composites include those made up of discrete layers (sandwich laminates) and
those reinforced by fibrous mats, woven cloth, or long, continuous filaments of
glass or other materials.
Plywood is a form of sandwich construction of natural wood fibres with plastics.
The layers are easily distinguished and are both held together and impregnated
with a thermosetting resin, usually urea formaldehyde. A decorative laminate can
consist of a half-dozen layers of fibrous kraft paper (similar to paper used for
grocery bags) together with a surface layer of paper with a printed design—the
entire assembly being impregnated with a melamine-formaldehyde resin. For
both plywood and the paper laminate, the cross-linking reaction is carried out
with sheets of the material pressed and heated in large laminating presses.

Fibrous reinforcement in popular usage is almost synonymous with fibreglass,
although other fibrous materials (carbon, boron, metals, aramid polymers) are
also used. Glass fibre is supplied as mats of randomly oriented microfibrils, as
woven cloth, and as continuous or discontinuous filaments.
Hand lay-up is a versatile method employed in the construction of large
structures such as tanks, pools, and boat hulls. In hand lay-up mats of glass
fibres are arranged over a mold and sprayed with a matrix-forming resin, such as
a solution of unsaturated polyester (60 parts) in styrene monomer (40 parts)
together with free-radical polymerization initiators. The mat can be supplied
already impregnated with resin. Polymerization and network formation may
require heating, although free-radical “redox” systems can initiate polymerization
at room temperature. The molding may be compacted by covering the mold with
a blanket and applying a vacuum between the blanket and the surface or, when
the volume of production justifies it, by use of a matching metal mold.





Continuous multifilament yarns consist of strands with several hundred
filaments, each of which is 5 to 20 micrometres in diameter. These are
incorporated into a plastic matrix through a process known as filament winding,
in which resin-impregnated strands are wound around a form called a mandrel
and then coated with the matrix resin. When the matrix resin is converted into a
network, the strength in the hoop direction is very great (being essentially that of
the glass fibres). Epoxiesare most often used as matrix resins, because of their
good adhesion to glass fibres, although water resistance may not be as good as
with the unsaturated polyesters.
A method for producing profiles (cross-sectional shapes) with continuous fibre
reinforcement is pultrusion. As the name suggests, pultrusion resembles
extrusion, except that the impregnated fibres are pulled through a die that
defines the profile while being heated to form a dimensionally stable network.
Recycling and resource recovery
In many municipalities, the favoured method of disposing of solid waste is in
sanitary landfills, in which layers of refuse alternate with layers of soil. However,
concerns over the wisdom of such land use has encouraged efforts to dispose of
various materials by recycling them for re-use or to derive some positive
benefits. Paper as well as glass and aluminum containers have been recycled to
some degree for many years, and in more recent years plastic recycling has
become common. There are several technical and economic problems in the
recycling of plastics; they fall into two general categories: (1) identification,
segregation (or sorting), and gathering into central stations and (2) the
economics of recovering value.
Identification, segregation, gathering
Since plastics used in packaging form a highly visible part (approximately 20
percent by volume but less than 10 percent by weight) of the waste stream,
most recycling efforts have focused on containers. Almost all bottles, food trays,
cups, and dishes made of the major commodity plastics now bear an identifying
number enclosed in a triangle together with an abbreviation.
Plastic recycling numbers and uses



plastic name

can be found in

can be recycled


carbonated beverage
bottles, food and
condiment jars, oven-ready
and microwavable meal
trays, textiles, carpet,
straps, films

carpet fibre, polar
fleece, insulating
fibrefill, tote bags,
straps, containers
for food and
beverages, film
and sheet

HDPE (highdensitypolyethyle

milk jugs, bottles for
shampoo and household

bottles for
shampoo and







cleaners, trash bags,
shopping bags, cereal box
liners, pipe and conduit,
wire and cable covering

cleaners, plastic
lumber, floor tiles,
buckets, crates,
film and sheet,
recycling bins

V, or PVC

food trays, shrink-wrap,
cling film, bottles (for
cleaners, shampoo,
cooking oil, etc.), blister
packs, hinged carryout
food containers
(clamshells), pipe, siding,
window frames, fencing,
decking and railing

decking, mudflaps,
flooring, cables,
carpet backing,
traffic cones, film
and sheet

LDPE (lowdensitypolyethyle

squeezable bottles, bags
(for bread, dry cleaning,
shopping, etc.), tote bags,
shrink-wrap, toys, wire and
cable covering

trash bins and
liners, shipping
paneling, plastic
lumber, floor tile,
film and sheet

PP (polypropylene)

margarine tubs,
microwavable meal trays,
yogurt containers, bottle
caps, medicine bottles,
durable consumer and
automobile parts,

automobile signal
lights, battery
cables, battery
cases, ice scrapers,
garden rakes,
storage bins,
pallets, sheeting

PS (polystyrene)

foam food trays and egg
cartons, disposable
tableware (plates, cups,
and cutlery), hinged
carryout food containers
(clamshells), compact-disc
cases, packing material,

switchplates, egg
cartons, foam
packing material,
containers, rulers,
plastic decorative


large water bottles,
bulletproof materials,
sunglasses, DVDs,
computer cases, nylon
products, packaging

plastic lumber,

In addition to such labeling, in many localities consumers are encouraged to
return empty beverage containers to the place of purchase by being required to
pay a deposit on each unit at the time of purchase. This system helps to solve
two of the major problems associated with economical recycling, since the
consumer seeking return of the deposit does the sorting and the stores gather
the plastics into central locations. An added attraction of deposit laws is a
notable decrease in roadside litter. However, while such measures have helped
to raise dramatically the recycling rate of plastic bottles—especially those made
of polyethylene terephthalate (PET) and high-density polyethylene (HDPE)—less
than 5 percent of all plastic products are recycled after first use. (On the other
hand, most plastics are used in long-term applications such as construction,
appliances, and home furnishings, for which efficient recycling is difficult.)
Economic recovery of value
In general, thermoplastic materials can be recycled more readily
than thermosets. Still, there are inherent limitations on the recycling of even
these materials. First, a recyclable plastic may be contaminated by nonplastics or
by different polymers making up the original product. Even within a single
polymer type, there are differences in molecular weight. For instance, a supplier
of polystyrene may produce a material of high molecular weight for sheet-formed
food trays, since that forming process favours a high melt viscosity and elasticity.
At the same time, the supplier may offer a low-molecular-weight polystyrene for
the injection molding of disposable dinnerware, since injection molding works
best with a melt of low viscosity and very little elasticity. If the polymers from
both types of product are mixed in a recycling operation, the mixed material will
not be very suitable for either of the original applications.





Another complication to the recycling of plastics is the mixing together of
pigments or dyes of different colours, and yet another is the problem of quality
control. Almost all plastics change either slightly or greatly as a result of initial
fabrication and use. Some, for instance, undergo changes in molecular weight
due to cross-linking or chain scission (breaking of the chemical bonds that hold a
polymer chain together). Others undergo oxidation, another common reaction
that can also change the properties of a plastic.
For all the foregoing reasons, recycled plastics will almost always have certain
disadvantages in comparison to unrecycled plastics. Most thermoplastics are
therefore recycled into somewhat less-demanding applications. HDPE from thinwalled grocery bags, for example, may be converted into thick-walled
flowerpots;polyvinyl chloride (PVC) recovered from bottles may be used in traffic
cones; and PET recovered from beverage bottles may be washed, dried, and
melt-spun into fibrous filling for pillows and clothing. Waste plastics that cannot
be separated by polymer type can be made into plastic “lumber,” extruded slabs
that are suitable for applications such as industrial flooring and park benches.
Owing to its heterogeneous composition, plastic lumber is inherently weaker
than the original polymers. Other recycling processes that make use of mixed
plastics are pyrolysis, which converts the solids into a petroleum-like substance,
and direct incineration, which can provide energy for power plants or industrial
Despite the difficulties in making the recycling of plastics economically attractive
on a large scale, many successful processes have been developed for more
narrowly defined “niche” applications. Automotive suppliers have found it
feasible to recycle polyurethanes from the insides of panels and dashboards if
proper attention is paid to the design of the original materials.
The polycarbonates widely used in compact discs have been recovered and
effectively reused. The polypropylene casings of automobile batteries can be
recovered economically during lead-recycling operations and then remolded for
the same application. Some manufacturers depolymerize PET by hydrolysis or
methanolysis; the resulting materials can be purified by distillation and then
In most plastic recycling operations, the first step after sorting is to chop and
grind the plastic into chips, which are easier to clean and handle in subsequent
steps. The chips commonly are first washed in order to remove nonplastic items

such as labels, caps, and adhesives. If the material comes from a narrowly
defined source, it may be possible to dry the washed chips and immediately
extrude them into molding pellets or even to extrude them directly into fibres.
For “mixed-waste” polymers, automatic separation processes based on
differences in density or solubility have been used to some extent.
Degradable plastics
None of the commodity plastics degrades rapidly in the environment.
Nevertheless, some scientists and environmentalists have seen biodegradable
and photodegradable plastics as a solution to the problem of litter. Some
“bioplastics” have been developed, but they have not been successful on a large
scale primarily because of high production costs and problems of stability during
their processing and use.
On the other hand, the plastic rings that hold six-packs of soft-drink and beer
cans together represent an application where photodegradation has been used
effectively. A copolymer of ethylene with some carbon monoxide contains ketone
groups that absorb sufficient energy from sunlight to cause extensive scissioning
of the polymer chain. The photodegradable plastic, very similar in appearance
and properties to low-density polyethylene (LDPE), decomposes to a powder
within a few months of exposure in sunny climates.
Plastic pollution in oceans and on land
Since the ocean is downstream from nearly every terrestrial location, it is the
receiving body for much of the plastic waste generated on land. It has been
estimated that 6.4 million tons of debris end up in the world’s oceans every year
and that some 60 to 80 percent of that debris, or 3.8 to 5 million tons, is
improperly discarded plastic litter. The first oceanographic study to examine the
amount of near-surface plastic debris in the world’s oceans was published in
2014. It estimated that at least 5.25 trillion individual plastic particles weighing
roughly 244,000 tonnes (269,000 tons) were floating on or near the surface.
Plastic pollution was first noticed in the ocean by scientists carrying
out plankton studies in the late 1960s and early 1970s, and oceans and beaches
still receive most of the attention of those studying and working to abate plastic
pollution. Floating plastic waste has been shown to accumulate in
five subtropical gyres that cover 40 percent of the world’s oceans. Located at
Earth’s midlatitudes, these gyres include the North and South Pacific Subtropical
Gyres, whose eastern “garbage patches” (zones with high concentrations of
plastic waste circulating near the ocean surface) have garnered the attention of
scientists and the media. The other gyres are the North and South Atlantic
Subtropical Gyres and the Indian Ocean Subtropical Gyre.




In the ocean, plastic pollution can kill marine mammals directly through
entanglement in objects such as fishing gear, but it can also kill through
ingestion, by being mistaken for food. Studies have found that all kinds of
species, including smallzooplankton, large cetaceans, most seabirds, and all
marine turtles, readily ingest plastic bits and trash items such
as cigarette lighters, plastic bags, and bottle
caps.Sunlight and seawater embrittle plastic, and the eventual breakdown of
larger objects makes it available to zooplankton and other small marine animals.
In addition to being nonnutritive and indigestible, plastics have been shown to
concentrate pollutants up to a million times their level in the surrounding
seawater and then deliver them to the species that ingest them. In one study,
levels ofpolychlorinated biphenyl (PCB), a lubricant and insulating material that
is now widely banned, were shown to have increased significantly in the preen
gland oil of streaked shearwaters (Calonectris leucomelas) after these seabirds
had been fed plastic pellets culled from Tokyo Bay for only one week.

There are also terrestrial aspects to plastic pollution. Drainage systems become
clogged with plastic bags, films, and other items, causing flooding. Land birds,
such as the reintroduced California condor, have been found with plastic in their
stomachs, and animals that normally feed in waste dumps—for instance, the
sacredcows of India—have had intestinal blockages from plastic packaging. The
mass of plastic is not greater than that of other major components of waste, but
it takes up a disproportionately large volume. As waste dumps expand in
residential areas, the scavenging poor are often found living near or even on
piles of residual plastics.
Pollution by plastics additives
Plastic also pollutes without being littered—specifically, through the release of
compounds used in its manufacture. Indeed, pollution of the environment by
chemicals leached from plastics into air and water is an emerging area of
concern. As a result, some compounds used in plastics, such
as phthalates, bisphenol A (BPA), and polybrominated diphenyl ether (PBDE),
have come under close scrutiny and regulation. Phthalates are plasticizers—
softeners used to make plastic products less brittle. They are found in medical
devices, food packaging, automobile upholstery, flooring materials, and
computers as well as in pharmaceuticals, perfumes, and cosmetics. BPA, used in
the manufacture of clear, hard polycarbonate plastics and strong epoxy coatings
and adhesives, is present in packaging, bottles, compact discs, medical devices,
and the linings of food cans. PBDE is added to plastics as a flame retardant. All
these compounds have been detected in humans and are known to disrupt
the endocrine system. Phthalates act against male hormones and are therefore
known as anti-androgens; BPA mimics the natural female hormoneestrogen; and
PBDE has been shown to disrupt thyroid hormones in addition to being an antiandrogen. The people most vulnerable to such hormone-disrupting chemicals are
children and women of reproductive age.
These compounds have also been implicated in hormone disruption of animals in
terrestrial, aquatic, and marine habitats. Effects are seen in laboratory animals
atblood levels lower than those found in the average resident of a developed
country.Amphibians, mollusks, worms, insects, crustaceans, and fish show effects
on their reproduction and development, including alterations in the number of
offspring produced, disruption of larval development, and (in insects) delayed
emergence—though studies investigating resulting declines in those populations
have not been reported. Studies are needed to fill this knowledge gap, as are
studies of the effects of exposure to mixtures of those compounds on animals
and humans.
The Danger of Burning Plastic
It is important for your own health and the health of your family to be
environmentaly conscious. Of course we need to reduce, reuse and recycle
however, the answer is not to weigh the rubbish. This only creates a burn it to
save money mentality. The education just isn't in the schools to warn about the
dangers of burning rubbish and meanwhile the cancer rates are on the rise and
burning plastic is one of many reasns why.
Why are cancer rates so high?

Open burning of plastic waste is simply dangerous to your health and the health
of the environment. Plastic such as PVC (polyvinylchloride) is common in such
things as bottles and jugs, plastic packaging and blister packs, etc. When these
are burnt in the house, carbon monoxide, dioxins and furans are released into
your air. Whilst carbon monoxide is a pretty well known poison, dioxins and
furans are not. Studies have linked dioxins and furans to cancer and respiratory
Dioxin is a toxic organic chemical that contains chlorine and is produced when
chlorine and hydrocarbons are heated at high temperatures. To inhale dioxin or
to be exposed to its fumes can cause many deadly results. Toxic components
inhaled through smoke from burning plastic materials may cause hormonal
imbalance and sex behavioural orientation of your newborn baby. As a result, the
child could begin exhibiting behaviour, in total contrast to his or her sex changes from male to female sexual characters or vice versa. Researchers have
established that inhaling burnt plastic materials have altered sexual characters
of birds (from male to female). They have discovered the same defects can easily
occur in human beings. Plastic should never be burned in the open air. There are
recycling options available for many of these products.
Toxic gases emitted by burning plastic materials - dioxins and furans - can also
cause cancer, impotence, asthma and a myriad other allergies to human beings.
Young Danes have reported exceptionally low sperm counts compared to the
previous generations, testicular cancer has increased by 55 per cent between
1979 and 1991 in England and Wales. Fewer boys are being born in Seveso, Italy,
where toxic dioxin was released. Some girls are achieving puberty earlier than
Oil fired or wood stoves simply do not reach high enough temperatures to
destroy many of the dangerous chemicals created when plastic burns. Municipal
solid waste incinerators such as the double chambered incinerators at the Energy
from Waste Plant can reach a temperature of 1800 degrees Fahrenheit (982 C),
providing plenty of oxygen to complete the burning process. Oiled fired and wood
stoves only tend to smoulder and smoke, releasing plumes of toxic fallout into
your backyard and the surrounding community making your street as polluted as
down town Tokyo! The ash is also potentially hazardous and not appropriate to
spread on the soil. Do yourself and the world a favour. STOP BURNING PLASTIC
NOW! If your neighbours burn plastic, report them to your local council.
Remember, good health is about good food, clean water and clean air. This is not
mamby, pamby, hippy rubbish!
Carina is available to lecture for your group or institution on this
Carina Harkin BHSc.Nat.BHSc.Hom.BHSc.Acu. is a practitioner of 11 years,
complementary medicine lecturer of 4 years and mother of six in Galway, Ireland
who practices what she teaches.
For an appointment call Carina directly on 083 34 66 333.
All products are available through Remember, we are here for
a good time not a long time, enjoy your food life!

Carahealth Galway, Acupuncture, Naturopathy, Homeopathy, Herbal
Medicine, Nutrition, Nutritional therapy, Flower essences, Iridology,
Short Courses, Cosmetic Acupuncture
Solving the problem
Given the global scale of plastic pollution, the cost of removing plastics from the
environment would be prohibitive. Most solutions to the problem of plastic
pollution, therefore, focus on preventing improper disposal or even on limiting
the use of certain plastic items in the first place. Fines for littering have proved
difficult to enforce, but various fees or outright bans on foamed food containers
and plastic shopping bags are now common, as are deposits redeemed by taking
beverage bottles to recycling centres. So-called extended producer
responsibility, or EPR, schemes make the manufacturers of some items
responsible for creating an infrastructure to take back and recycle the products
that they produce. Awareness of the serious consequences of plastic pollution is
increasing, and new solutions, including the increasing use of biodegradable
plastics and a “zero waste” philosophy, are being embraced by governments and
the public.
Batteries Which Will Convert Waste Heat to Electricity

Photo Credit : Pixabay
Generate electrical energy from the waste heat of your car engine, how does it
sound. Yes now it is possible, researchers have developed a new ammonia based
battery system to convert low grade waste heat to electricity.
This generation of electricity from waste heat would allow generation
of power without any added consumption of fossil fuel. These thermally
regenerative batteries are a carbon-neutral way to store and convert waste heat
into electrical power and that too with low cost.
In automobile this could be the great method to utilize the waste heat from the
engine. This waste heat from engine with the help of these thermal batteries
could feed various electrical requirements of the automobile without the use of
additional battery.
These battery employs ammonia which get distilled (converted into pure
ammonia liquid by distillation) because of the waste heat it absorbs, this liquid
ammonia is then passed between anode and cathode chamber of the battery
unit and each time the chamber with ammonia becomes anode. Due to this the
copper get re-deposited on the electrode of other chamber. The ammonia liquid

keeps switching back and forth between the two chambers and hence the
amount of copper on the electrodes is maintained.
The electric current is produced because of the formation of copper-ammonia
complex, this is how ammonia liquid stream converts thermal energy into
electrical energy. Note that heat is needed here to form distill ammonia and
without it the battery will not work, there will be no copper-ammonia complex.
Hence these type of battery have to absorb heat in some way to generate
electrical energy.
So far researchers have produced power density of about 60 Watts per square
meter, this is six times higher than the power density produced by other liquidbased thermal batteries. Researchers believe that there is a large room of
optimization in these batteries and hence its power density can be increased.
They will be a perfect substitute for the batteries in cars and other automobiles,
and can make these automobiles highly efficient since no energy will be wasted
#waste heat to electricity

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