Baboo Fiber Crysrallinity Using X Ray Diffraction

 

Preparation and Crystalline Analysis of High-Grade Bamboo Dissolving Pulp for Cellulose Acetate  Jianxin He,1,2 Shizhong Cui,2 Shan-y Shan-yuan uan Wang1 1

College of Textiles, Dong Hua University, Shanghai 201620, People’s Republic of China

2

College of Textiles, Zhongyuan University of Technology, Zhengzhou 450007, People’s Republic of China Received 12 October 2006; accepted 6 February 2007 DOI 10.1002/app.27061 Published online 1 October 2007 in Wiley InterScience (www.interscience.wiley.com). bamboo boo dissol dissolving ving pulp for ce cellABSTRACT:   High grade bam lulose lulose acetat acetatee (na (named med as acetat acetatee bam bamboo boo pulp) pulp) was pre pre-affinnis) by oxypared from bamboo Cizhu (Dendrocalamus (Dendrocalamus affinnis) gen-al gen -alkali kali pul pulpin ping, g, xylanas xylanasee and DMD (an int interm ermedi ediate ate product of the reaction of oxone with acetone) delignificatio tion n treatm treatment ents, s, and H2O2   bleachin bleaching. g. Its prope properties rties and structures were investigated by different analytical techniques, and compared with those of high grade hardwood dissol dissolvin ving g pul pulp p for cellul cellulose ose acetat acetatee (na (named med as ace acetat tatee wood pulp), viscose bamboo pulp, and bamboo fiber for textile. Most of its properties are comparable with those of 

Inc. J Appl Polym Sci 107: 1029–1038, 2008

ac aceeta tate te woo ood d pulp puextractive lp exc xceeptthatas ash h con co nte ten ntshigh. an and dCrystalDCM (dichloromethane) are slightly linities and crystalline allomorphs of acetate bamboo pulp

Key wor words: ds:   bambo bamboo o dissol dissolvin ving g pul pulp; p; cellul cellulose ose acetat acetate; e; crystalline structure;   13C NMR; FTIR

INTRODUCTION

Among natural fiber plants, bamboo is a kind of  rapidly rapi dly grow grown n and early early harv harveste ested d vegetabl vegetablee with high hig h adapta adaptabil bility ity,, whi which ch is not lik likee tre treee to su suffe fferr insect infestation. After grown 3 years, bamboo can  be felled every year within several decades to 100 years. year s. Unfortuna Unfortunately, tely, bamboo is only employed employed in conven con ventio tional nal app applic licati ations ons suc such h as furnit furnitur ure, e, conconstru structi ction on,, pa pape perr indu indust stry ry th thro roug ugho hout ut th thee As Asia ian n region in spite of its superior properties like biode-

Cellulose acetate, being important in textile and cigarette industries, is prepared from high quality celluloses loses such such as cotton cotton lin linter terss and hig high-g h-grad radee wood wood pulp pulpss wi with th al alph phaa cell cellul ulos osee co cont nten entt of more more th than an 1 95%. Cotton linters, the ideal material for cellulose acetate production, are limited to planting area and climat climate. e. Hig High-g h-grad radee wood wood pu pulps lps come come fro from m high high quality hardwoods and softwoods of more than 20 years, which are restricted to fell, owing to environment protection policy. Bamboo is a woody herbaceous plant, which consists of many vascular bundles and xylem.2 A vascular bundle includes four sheaths of fibers, two vessels, sels, and some some sie sieve ve tubes. tubes. Xy Xylem lem su surro rround undss eac each h vascular bundle. The sheath consists of many single fiber fiberss whos whosee di diam amet eter er is 10 10–2 –200 nm each each in av aver er-age.3,4 The There re are are 1250 1250 specie speciess of bam bamboo booss within within 75 genera in the world, among which Asia accounts fo forr ab abou outt 1000 1000 spec specie ies, s, co cove veri ring ng an ar area ea of ov over er 180,000 km2.5 Correspondence to: J. to:  J. He ([email protected]). Contrac Con tract grant tnan spo sponso r: ince Key Scienc ence ect and Techn Tecnu hnolo ology gy: Pr Prog ogra ram m tofgran He Hena n nsor: Pr Prov ovin ce;; Sci cont contra ract gra grant nt numb mber er: 052SYG26140.  Journal of Applied  Journal Applied Polym Polymer er Scien Science, ce, Vol Vol.. 107, 1029–1038 1029–1038 (2008) (2008) C 2007 Wiley Period V Periodicals, icals, Inc.

and the three samples were determined by FTIR spectroscopy, X-ray diffraction and solid state   13C NMR spectroscopy, and the results obtained by the three methods were coi coinci nciden dent. t. Bamb Bamboo oo cellul cellulose ose crys crystal tallin linee allomo allomorph rphss are classified classi fied as   I b-domin -dominant ant type, and a highe higherr later lateral al order index and a larger crystallite size for acetate bamboo pulp weree fou wer found nd in spite spite of its crys crystal tallin linity ity sim simila ilarr to acetat acetatee wood pulp. Differ Different ent inte intermolec rmolecular ular hydroge hydrogen n bond patterns are likely be responsible for the predominant crystalline fibrils in acetate bamboo pulp.      2007 Wiley Periodicals,

grad gradabili ability, ty,6 There low cost, regener regeneration, ation, wide widespre spread ad utilization. are limited reportsand in the scientific literature concerning the use of bamboo pulp fiber, and a few researches focus on that bamboo pulp is used used as rein reinfo forc rcin ing g ma mate teri rial al of co comp mpos osit itee or employ emp loyed ed in paper paper mak making ing..3–7 Rece Recently, ntly, bamboo bamboo pulp has been utilized in preparing viscose fiber in somee Asia som Asia cou countr ntrie ies, s, but there is no repor reportt about about  bamboo material used in preparing cellulose acetate due to the highe higherr req requir uireme ements nts for the quali quality ty of  pulp. The aim of this study was to prepare high grade  bamboo dissolving pulp for cellulose acetate from  bamboo Cizhu. Cellulose I has two crystallization modifications   I a   and   I b, assigned to the triclinic and 8 m, res monoclini mono clinic c syste system, pectively vely, which on cellulose origin. Therespecti contents of, the twodepend crystalline allomorphs in various origins have been investigated  by many methods.9 Ho Howe weve ver, r, th ther eree is no re repo port rt about the amount of two crystalline modifications in

 

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TABLE I Bleaching Conditions Stages

Pulp consistency (%)

X  P

   

10 10

D E

   

10 10

Chemical charge

Temperature (8C)

Time (min)

0.5% DTPA, 0.04% xylanase 5% H2O2, 2% NaOH 0.5% EDTA, 0.5% MgSO4 oxone 8 g/L, acetone 6 g/L 2% NaOH

70 70

90 120

6.5

60 60

100 60

7.0–7.5

 bamboo cellulose. Thus relative   I a   and   I b   content and crysta crystalli lline ne struct structur uree in acetat acetatee bamboo bamboo pu pulp lp weree also investigated wer investigated by FTIR spectros spectroscopy, copy, X-ray diffractio diffr action, n, and solid state   13C NMR spectros spectroscopy, copy, and compared with those of acetate wood pulp and other two bamboo celluloses: bamboo fiber and viscose bamboo pulp. EXPERIMENTAL

pH

40 min, and the liquor to bamboo ratio was 7 : 1. HPA can increase the selectivity of oxygen delignification and decrease the degradation of carbohydrate for its syner synergic gic act action ion wit with h oxyge oxygen n to enabl enablee aroaromatic rings in lignin to be opened and decomposed into organics and carbon dioxide.10 The black liquor was separated from the pulp by pressing in a nylon washing bag. The pulp in this bag was then thoroughly washed using a water shower. The total yield was determined as 37%.

Materials

The bamboo bamboo materi material al cho chosen sen was Cizhu Cizhu (Dendrocalamus lam us affinnis affinnis) fr from om Zhej Zhejia iang ng prov provin ince ce of Chin China. a. Xylana Xyl anase se us used ed in exper experime iment nt was xy xylan lanase ase PulpPulpzymee HC pr zym provi ovided ded by Novozy Novozyme me,, Den Denmar mark, k, wit with h optim optimum um activi activity ty at 708C an and d pH 6.5. 6.5. Ox Oxon onee was was from Dupont. Acetate wood pulp prepared by prehydrol hyd rolyze yzed d kraft kraft pu pulpi lping ng fro from m Rayoni Rayonier er,, vi visco scose se  bamboo pulp prepared by prehydrolyzed prehydrolyzed kraft pulping from from Shangh Shanghai ai pu pulp lp fac factor tory, y, and bambo bamboo o fiber fiber for textile from Zhejiang bamboo fiber research center were used in experiments to investigate crystalline line stru struct ctur uree of acet acetat atee ba bamb mboo oo pulp pulp.. All All ot othe herr chemicals used were purchased from local company as analytical reagents and used without further purification. Cooking

Bamboo chips from the internodes of 2   3   1 cm2 size were soaked in water about 8 h, and then were prehydrolyzed and cooked in autoclaves. In the prehydrolysis step bamboo chips and water with a ratio of  1 : 10 were charged, then 5% H2SO4   based on the dry weight of bamboo chips were added in, and the autoclave was heated to 1008C under a heating rate of 38C/min and kept at 1008C for 200 min. The autoclave was then cooled to about 50 8C and emptied, an and d the the chip chipss we were re wash washed ed wi with th ho hott wate water. r. The The yield was 79.8%. Cooking step H, was0.05% then about 180), min wit with h 13% NaOH, NaO 0.0 5% performed anthra anthraqu quino inone ne (AQ), (AQ 1% Heteropol Hete ropoly y Acid (HPA), 1% MgCl2   at 0.8 MPa O 2pressure, and the maximum cooking temperature of  1608C. The time at maximum temperature was about  Journal of Applied Polymer Science Science DOI  DOI 10.1002/app

Bleaching

The pulp was bleached in polyethylene bag in water  bath, using the XPDEP sequence, and here X, P, D, E indicated indic ated xylanase xylanase treatmen treatmentt stage, stage, H2O2   bleaching stage, DMD treatment stage, and alkaline extraction stage,, res stage respecti pectively vely.. The conditions conditions of bleaching bleaching are liste isted d in Ta Tab ble I. The pulp was was im imm mersed in NaH2PO4/Na2HPO4   buff buffer er solu soluti tion on of pH 6. 6.55 fo forr 60 mi min n before before treated treated by xyl xylana anase se in X stage stage,, and DTPA DT PA as me metal tal ion chelat chelator or can dec decre rease ase use useles lesss degradation of H2O2   in latter P stage. DMD, a reage gent nt of delign delignific ificati ation, on, is a interm intermedi ediate ate pro produc ductt of the reaction of oxone (2KHSO 5      KHSO4      K2SO4) with acetone, and the reaction equation is shown in Figure 1.11,12 DMD having stronger electrophilic oxidation dat ion su susce scepti ptibil bility ity can react react with with C¼ ¼C, a domi domi-nate chromophoric group, in aliphatic and aromatic configurations in lignin by transferring active oxygen at atom omss (F (Fig ig.. 2), 2), th thus us impr improv ovee th thee brig bright htne ness ss of  11–13 pulp. The final yield of pulp after washed and dried was 13%.

Figure 1   Formation o off DMD.

 

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X ccrr  ¼

Reaction ion of DM DMD D with C C¼ Figure 2   React ¼ C in lignin.

Chemical analysis

The degree of polymerizations (DP) of cellulose samples were determin determined ed from the intrinsic intrinsic viscosities viscosities [h], which which wer weree measu measured red using using a Cannon Cannon-Fe -Fensk nskee Routin Rou tinee Vis Viscom comete eterr in a cupricupri-eth ethyle ylene ne-di -diami amine ne (CED) solution at 25 8C according to TAPPI (Technical Association of the Pulp & Paper Industry, America) ica) T206, T206, by the formu formula la of DP0.905 5   0.75[h]/mL g21. The contents of carbohydrate components such as cellulose cellulose,, lignin, lignin, and pen pentose, tose, solubility solubility expe expeririments me nts,, and ash conten contents ts were were deter determin mined ed for raw material or cellulose samples using TAPPI standard methods. Brightness was measured according to ISO 3688/2470.

  Acr 3  100%  Acr þ Aam

integrat rated ed areas areas of the where   Acr   and   Aam   are the integ crystalline and amorphous phases, respectively. In the second deconvolu deconvolution tion method, the diffracdiffraction profile was fitted by Lorentzian function, ranging from 2y  5 8  to 408, to find the contribution of each indivi ind ividua duall pe peak ak relati relative ve to the 101, 10-1, 10-1, 002 002,, 040 crysta cry stallo llogra graph phic ic plane planess and the amorph amorphous ous backbackgr grou ound nd.. The The maxi maximu mum m of am amor orph phou ouss pe peak ak wa wass measured from the minimum of the diffraction profile between the 10-1 and 002 peaks. The crystallinity X d  was calculated by:





  Sa X d  ¼   1   3  100% Sa þ Scr

where   Sa   is the amorphous integrated area, and   Scr is the sum of the integrated areas of the 101, 10-1, 002, 040 peaks. The third approach was the empirical method pro14

posed by Segal et al. for native cellulose: Scanning electron microscopy

The samples were coated with gold film or embedded with epoxy resin in order to observe the surface morphology and the microstructure. The instrument was a JEOL JSM-5600LV JSM-5600LV elec electron tron microsc microscopic opic with an accelerating voltage of 15 kV. FTIR spectroscopy

A mixt mixtur uree of 5.05.0-mg mg drie dried d cell cellul ulos osee po powd wder erss ob obta tain ined ed fr from om samp sample less an and d 20 2000 mg KBr KBr were were pressed into a disk for FTIR measurement in a Nicolet Nexus670 FTIR spectrometer. A total of 100 scans were we re take taken n fo forr each each sa samp mple le with with reso resolu luti tion on of  21 2 cm . X-ray diffractometry

X-ray diffraction was recorded at room temperature from 58  to 508   at a scanning speed of 0.028/s with a Rigaku-D Riga ku-D/Max /Max-2550 -2550PC PC diffractom diffractometer eter using Ni-filNi-filtered Cu Ka  radiation of wavelength 0.1542 nm. The op oper erat atin ing g volt voltag agee an and d cu curr rren entt were were 40 kV and and 30 mA, respectively. Crystallinities of celluloses in samples were calculated from diffraction intensity data using three different fere nt methods. methods.8,14 The The first first on onee as assu sume mess a two two phasee structur phas stru cture e (crystalli (crystalline-a ne-amorp morphous hous)) an and a line  between the intensity minima to obtain arbitrary  background to diffraction trace, thus separating an ar arbi bitr trar ary y crys crysta tall llin inee phas phasee fr from om an amor amorph phou ouss phase, the crystallinity   X ccrr  was calculated by:

CrI ¼

I 002 002  I Amorph Amorph 3  100% I 002 002

where CrI is the crystallinity index,   I 0002 02   is the maximum mu m inten intensit sity y of the (002) (002) lattic latticee dif diffra fracti ction on and 8 y I Amorph  is the diffraction intensity at 18  2  degrees. Amorph The average size of crystallite was calculated from the Scherrer equation with the method based on the width of the diffraction patterns obtained in the Xray reflect reflected ed crysta crystalli lline ne regio region. n. In this this study, study, the crysta cry stalli llite te siz sizes es wer weree deter determin mined ed by using using the dif dif-fra fractio ction n patter pattern n obtain obtained ed from from the 002 (hk (hkl) l) lattic latticee planes of cellulose samples15: DðhklÞ  ¼

  kk BðhklÞ cos u

where (hkl) is the lattice plane,   D(hkl) is the size of  crystallite,   k   is the Scherrer constant (0.84),   k   is the X-ray X-ra y wave wavelengt length h (0.154 (0.154 nm),   B(hkl) is the FWHM (f (ful ulll widt width h half half ma maxi ximu mum) m) of th thee meas measur ured ed hk hkll reflec reflectio tion n and 2y   is the correspo corresponding nding Bragg angl anglee (reflection angle). 13

C-CP/MAS NMR

All the   13C-CP/MAS NMR measurements were perfor formed med wit with h a Bru Bruker ker AV400 AV400 NMR spe spectr ctrom omete eterr opera operatin ting g at 75. 75.55Hz, MHz for carbon carbons. The spinn inning ing speed was 5000 acquisition times. 20 ms,sp contact time time 1 ms an and d dela delay y be betw twee een n pu puls lses es 3 s. Al Alll th thee cellul cellulose ose sampl samples es were were mea measu sured red in nev never er-dr -drie ied d (50 wt %).  Journal of Applied Polymer Science Science DOI  DOI 10.1002/app

 

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TABLE II Chemical Composition of Bamboo Cizhu Composition

Percentage based on dry material (%)

Cellulose Lignin Pentose Ethanol-benzene extractive 1% NaOH extractive Hot-water extractive Cold-water extractive Ash

51.09 22.40 21.60 1.64 22.26 6.78 2.42 1.53

RESULTS AND DISCUSSION Chemical composition and physical properties of pulp

Chemical composition of Cizhu is shown in Table II. The result of chemical analysis shows that the cellulose lose con conten tentt of Cizhu Cizhu is simila similarr to or higher higher than than that of hardwood (42–51%), and higher than that of  16,17

softwood (39–43%). The lignin content of Cizhu is comparable with that of hardwood but lower than thatt of sof tha softwo twood od (27–33 (27–33%). %).16,17 It is re reve veal aled ed th that at pe pento ntose se,, 1% NaOH NaOH extra extracti ction, on, hot and cold cold wat water er extractions and ash content of Cizhu are higher than those tho se of two kinds of woods, woods, but the ethanolethanol-ben ben-zene extraction of Cizhu is lower than that of wood (2–3%).16,17 Overall the chemical analysis data shows that Cizhu is suitable for preparing high dissolving pu pulp, lp, mainly mainly be becau cause se of its relati relative vely ly low lig lignin nin,, high cellulose and hemicelluloses content. Table III summarizes composition, DP, and brightness of acetate bamboo pulp prepared as well as two pulp samples. It is shown that alpha cellulose content of acetate bamboo pulp is higher than that of  viscose visc ose bamboo pulp, ande, comparab comp arable le with that of  acet acetate ate wood pulp sample, sampl arriving at the demand for acetate acetate dissolving dissolving pulp pulp available available commerci commercially ally 1 (>95%), mea meanwh nwhile ile,, its DP is gr great eater er tha than n that that of  vis viscos cosee bamboo bamboo pu pulp, lp, approa approachi ching ng that that of acetat acetatee wood pulp (1000–1200 (1000–1200). ). The visible visible insoluble insoluble substance stance in CED soluti solution on and the slo slower wer dissol dissoluti ution on velocity velo city were identified identified in the DP measurem measurement ent of  viscose bamboo pulp, while there was no the insolu ble in acetate bamboo pulp. Mannose and xylose are representative neutral monosaccharides contained as hemicellulose in wood pulp, and derived from gluco coma mann nnan an an and d xyla xylan, n, re resp spec ecti tive vely ly.. It was was of ofte ten n reported for acetone solution of cellulose acetate that glucomannan acetate was a main cause of false viscosity poor xylan was a mai main nand cau cause se offilterability, haze, haze, po poor orwhile filter filterabi abilit lity, y,acetate and colorcol oring.18–21 Acetate dissolving pulps available commercially contain mannose in a range between 0.3 and 1.5%, while 0.9 and 2.8% in xylose content.1 As can  Journal of Applied Polymer Science Science DOI  DOI 10.1002/app

 be seen in Table III, the lower xylose content in acetat tatee bamboo bamboo pu pulp lp compar compared ed with with vi visco scose se bamboo bamboo pulp can be identified, and the content is in the controllable range in spite of the higher value compared with wit h acetat acetatee wood wood pulp, pulp, consid consideri ering ng the there re was no gluc glucom oman anna nan n in acet acetat atee ba bamb mboo oo pu pulp lp pr prep epar ared ed  because bamboo belongs herbaceous plants including no glu glucom comann annan. an. An obviou obviouss improv improveme ement nt of  IS ISO O brig bright htne ness ss fo forr ac acet etat atee ba bamb mboo oo pu pulp lp ca can n be found compared with viscose bamboo pulp and only 4.3% 4.3% dif differ ferenc encee be betwe tween en it and ace acetat tatee wood wood pu pulp lp indicates that the brightness of acetate bamboo pulp prepared prep ared has approache approached d that of acetate acetate dissolvin dissolving g 1 pulp available commercially (90–96%). The ash contentt and DCM extrac ten extractiv tivee in acetat acetatee bamboo bamboo pulp, pulp,  being higher greatly than that of acetate wood pulp, have not gone beyond the range of acetate dissolving pulp (ash     0.12, DCM extractive     0.08).1 Morphological analysis

Bamboo pulp fiber is long cylindr Bamboo cylindrical ical and unifo uniform rm in size with distinct nodes [Figs. 3(a) and 4(a)], being different from wood pulp fiber which is flat without dist distin inct ct node nodess [F [Fig ig.. 3( 3(c) c)]. ]. Figu Figure re 3( 3(b, b,d) d) show show th thee SEM SEM imag images es of acet acetat atee ba bamb mboo oo fib fiber er an and d ac acet etat atee wood fiber at magnification of 5000. It can be seen that there are full of grooves, splits, apertures, filament me ntss an and d fib fibri rils ls in tw two o fib fiber er surf surface aces, s, ho howe weve verr  bamboo fiber is straight with a smooth, sleek surface [Fig. [Fig. 3(f)], 3(f)], showin showing g no sig sign n of for format mation ion of fib fibril rils, s, and only a small quantity of cracks and fibrils in the surface of viscose bamboo pulp fiber [Fig. 3(e)]. This indicates that the same as acetate wood pulp, lignin, an and d hemi hemice cell llul ulos osee in ac acet etat atee ba bamb mboo oo pu pulp lp we were re removed rem oved using using the pulping pulping including including xylanase and DMD DM D tre treatm atment ent more more fully fully tha than n bamboo bamboo fibe fiberr and viscose bamboo pulp. This entirely removing of lignin and hemicellulose can also be seen from lengthwise section of acetate bamboo pulp in Figure 4(b), wheree distribut wher distributing ing large large numbers numbers of aper aperture turess and cracks with uneven sizes besides inherent conduit. TABLE III Comparison of Chemical Composition and Physical Properties of Acetate Bamboo Pulp with Acetate Wood Pulp and Viscose Bamboo Pulp Parameters Alpha cellulose (%) DP DCM extractive (%) Xylose (%) Mannose (%) Brightness (%) Ash (%) Moisture (%)

Acetate Acetate Viscose  bamboo pulp wood pulp  bamboo pulp 96.24 1021 0.08

98.20 1134 0.013

85.43 512 0.22

3.9 0 88.4 0.10 6.70

1.3 0.3 92.7 0.020 6.81

6.8 0 75.5 0.22 6.96

 

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photograp graphs hs of (a) pulp fiber surf surface acess of (b) aceta acetate te bamboo pulp, pulp, (c, (c,d) d) acetat acetatee wood wood pulp, pulp, (e) vis viscos cosee Figure 3   SEM photo  bamboo pulp, and (f) bamboo fiber.

FTIR analysis

fiber has a faint band at 1739 cm21 attributed to the vibration of carboxyl group in hemicellulose.22

It can be seen from Figure 5ee that FTIR tat tate e bamboo bam boo pulp and thr three sample sam plessspectra sho show w of as acethe character char acteristi isticc spe spectra ctra of cellulose cellulose,, and there there are no vi vibr brat atio ion n ba band ndss of al alde dehy hyde de,, ke keto toni nic, c, ca carb rbox oxyl yl groups grou ps from lignin and hemicellulose hemicellulose,, but bamboo

thepu second FTIR of Figure acetat acetatee6 shows bamboo bamboo pulp lp andderivative three three sample sam pless spectra in the range of OH group stretching. The band profiles in intramole amolecular cular th thee 34 3400 00–3 –360 6000 cm21 range23,24 of intr hydrog hyd rogen en bonds bonds for three three pu pulps lps are fai fairly rly simila similar, r,  Journal of Applied Polymer Science Science DOI  DOI 10.1002/app

 

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HE, CUI, AND WANG

photographs aphs of (a) cross section and (b) lengthwise lengthwise section of acetate bamboo bamboo pulp. Figure 4   SEM photogr

and have have a highe higherr res resolu olutio tion, n, being being dif differ ferent ent fro from m  bamboo fiber which has a lowest resolution in this range. The three bands around 3623, 3584, and resolved in the spectra of three three 3570 cm21 are clearly resolved

fibrils fibri ls and biggish crystall crystallite ite size sizess in bamb bamboo oo fiber fiber and acetate bamboo pulp revealed by X-ray and   13C NMR spectroscopy (see later) are probably related to the different intermolecular hydrogen bond pattern.

pulps, while they are not distinguishable in the spectrum of bamboo fiber. Hence the lower crystallinities (see later) for two bamboo pulp compared with bam boo fiber most likely arise from the difference in the patterns patterns of intramole intramolecular cular hydrogen hydrogen bond. bond. The higher resolutions for acetate bamboo pulp and bam boo fiber in the band profiles in the 3200–3400 cm21 range23,24 of inter intermol molecu ecular lar hyd hydrog rogen en bonds bonds are observed compared with acetate wood pulp and viscosee bam cos bamboo boo pu pulp. lp. Thus Thus pr predo edomin minant ant cry crysta stalli lline ne

The second second deriva derivativ tivee FTIR FTIR spectr spectraa of four four sam sam-ples in the 900–500 cm21 fingerprint region show the simi simila larr pr profi ofile le wi with th a very very ev evid iden entt ba band nd arou around nd 21 712 cm and a inconspicuous band around 750 cm21 phase and   I a   phase,25 assign ass igned ed to crysta crystalli lline ne   I b   phase respectively (Fig. 7). Thus the crystalline allomorphs of three bamboo celluloses, the same as that of hardwood, were found as   I b-dominant type (monoclinic unit cell), which was not affected by extraction and pulping.

Figure 5   FTIR spectra of (a) aceta acetate te bamboo pulp pulp,, (b) acetate wood pulp, (c) viscose bamboo pulp, and (d) bamboo fiber.

Fi Figu gure re 6   Se Seco cond nd de deri rivat vativ ivee FTI FTIR R spec spectr traa (3 (370 700– 0–310 31000 cm21) of (a) acetate bamboo pulp, (b) acetate wood pulp, (c) viscose bamboo pulp, and (d) bamboo fiber.

 Journal of Applied Polymer Science Science DOI  DOI 10.1002/app

 

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ray diffractograms of semi-crystalline cellulose I allomorph, and it is obvious that for bamboo fiber the diffractogram is well resolved and the crystallinity is up upper permos most, t, wherea whereass for vis viscos cosee bam bamboo boo pu pulp lp it is lowest (Table V). Being different from the results calculate cul ated d by FTIR FTIR (Table (Table IV), for acetate acetate wood wood pu pulp lp the crysta crystalli llinit nity y calcul calculate ated d by the thr three ee dif differ feren entt

21

Figure 7   Secon Second d derivative FTIR spectra (800–45 (800–450 cmvis-) of (a) acetate bamboo pulp, (b) acetate wood pulp,0(c) cose bamboo pulp, and (d) bamboo fiber.

The ratio of the peak areas at 1370 and 670 cm 21 (A1371/A6 (A13 71/A665) 65) proposed proposed by Richter Richter et al. was used used to determin determinee relative relative crys crystalli tallinity nity index index (CrI). (CrI).26 It was also used to study the conversion of cellulose I into cellulose cellulose II.8,22,25,27 The lateral order index (LOI) of cell cellulose ulose was evaluate evaluated d using using the intensity ratio of the bands at 1430 and 898 cm 21, which is related to the proportion of cellulose I.8,22,28 The two results ar aree show shown n in Tabl Tablee IV. IV. The The high highes estt CrI CrI valu valuee in  bamboo fiber and the lowest CrI value in viscose  bamboo pulp were found, and the CrI value of ace-

methods can be seen to be higher slightly than for acetate bamboo pulp. The cause for the difference is thatt the IR crysta tha crystalli llinit nity y ind index ex is cor corre relat lated ed to the extent of the transition from cellulose I to cellulose II,27 and a hig highe herr con conten tentt of cel cellul lulose ose I in ace acetat tatee  bamboo pulp is likely to give rise to a higher CrI value. However compared with acetate wood pulp, acetat ace tatee bamboo bamboo pu pulp lp po posse ssesse ssess a larger larger cry crysta stalli llite te size (Table V). Z-disc -discrimi riminate nate function function developed developed by Wada and coworkers cowor kers was used to separate separate cellulose cellulose   I a   and   I b of native cellulose using   d-spaces obtained from Xray data.9,25 The function used to discriminate is represented as:   Z   5  1693d1-902d2-549, where Z   >  0 indicates the algal-bacterial (I a-rich) type and Z   <  0 indicates the cotton-ramie (I b-dominant) type. As can be seen seen in Tab Table le V, the cry crysta stalli lline ne allomo allomorp rphs hs deterdetermined by  Z -discriminate function for all bamboo cellul lulose osess and har hardwo dwood od cel cellul lulose ose we were re found found as   I bdomina dom inant nt type type withou withoutt excep exceptio tion n and the result result is consistent with that of FTIR analysis.

13

C-CP/MAS NMR analysis

The   13C-C C-CP/M P/MAS AS NMR spect spectra ra of ace acetat tatee bamboo bamboo pulp and three samples are presented in Figure 9. It

ta tate te ba bamb mboo oo valu valuee was was simi simila larr to th that at of ac acet etat atee wood pulp, but the maximum LOI value in acetate  bamboo pulp was also observed. X-ray diffraction analysis

The X-r X-ray ay dif diffra fracto ctogra grams ms of acetat acetatee bamboo bamboo pu pulp lp and three samples shown in Figure 8 are typical XTABLE IV Crystallinity Indexes (CrI) and Lateral Order Indexes (LOI) in IR Spectra of Acetate Bamboo Pulp and Three Samples CrI

LOI

Samples

A1371 371/A /A66 6655

H1430 430/A /A89 8988

Acetate bamboo pulp Acetate wood pulp Viscose bamboo pulp Bamboo fiber

6.417 6.243 5.771 7.077

1.994 1.403 1.168 1.892

Figure 8   X-ray diffrac diffractograms tograms of (a) acetat acetatee bamboo pulp, (b) acetate wood pulp, (c) viscose bamboo pulp, and (d)  bamboo fiber.

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HE, CUI, AND WANG

TABLE V Crystallinity, Crystallite Size, and Crystalline Allomorph of Acetate Bamboo Pulp and Three Samples d-spaces (nm)

Crystallinity (%) Samples

X ccrr

Acetate bamboo pulp Acetate wood pulp Viscose bamboo pulp

64.41 65.72 61.98

Bamboo fiber

79.47

 

X d

D(002)  (nm)  

d1

75.79 78.61 73.61

54.92 58.27 52.08

6.07 5.98 5.33

0.59824 0.59806 0.59832

0.54309 0.54067 0.54816

     

226.05 224.17 230.48

     

I b I b I b

88.95

68.50

7.07

0.60636

0.54495

 

213.98

 

I b

CrI

 

 

d2

Z

 

Allomorph

was found that in contrast with acetate wood pulp and viscose bamboo pulp, acetate bamboo pulp and  bamboo fiber showed two better resolved spectra, the expression of predominant crystalline fibrils, and it ca can n be kn know own n that that th this is diff differ eren ence ce mo most st like likely ly arises aris es from the differenc differencee of intermole intermolecular cular hydroge gen n bond bond pa patte ttern rn in four four sampl samples es associ associati ating ng with with the result of FTIR spectra analysis (Fig. 6). Table VI showss the   13C peak assignment show assignmentss of different different cellulose allomorphs. The C1 resonance region at about 105 ppm in re-

analysis. As is shown in Figure 10 and Table VI, the C4 signals of acetate bamboo pulp and three samples show the upfield wing associated with a less evident downfield downfi eld shoulder, shoulder, confi confirmin rming g the existenc existencee of   I a phase. As is sh show own n in Figu Figure re 9, th thee tw two o reso resona nanc ncee regions associated with C6 and C4 include sharper resonanc reso nances, es, assigned assigned to the order order regi region on in crystal crystal lattice, overlapping broader upfield wings, assigned to less order region that includes two categories of  environment.32 The first first includ includes es all cha chains ins loc locate ated d

soluti sol ution enh anceme ement nt spe shown sho wn in 10 Figur Fig ure 10 spli splits ts on to enhanc four four si sign gnal als, s, spectr th theectra inne inaner r tw two o at 105. 5.2 2 ean and d 104.9 ppm being being represen representativ tativee of cellulose cellulose   I a   and para paracr crys ysta tall llin inee prop propos osed ed by wi wick ckho holm lm et al., al.,29 respe respecti ctive vely; ly; the outer outer two at 105.6 105.6 and 104.1 104.1 ppm ppm assigned to cellulose   I b. The integration of obtained contents (61–68%) (61–68%) for signals sign als indicates indicates the high   I b   contents  bamboo and hardwood, while the high  I a  content for softwood documented by Newman.30,31 This is coincident with the results obtained by FTIR and X-ray

at the surfaces of cellulose microfibrils, which can be regarded as region of limited two-dimensional order. The second second cat catego egory ry of enviro environme nment nt is the regio region n within which the incoherence of order is not limited to two dimensions, and the chains are free to adopt a wider range of conformations than the ordering in a cry crysta stall lattic latticee or the their ir bou bounda ndarie ries. s. Cry Crysta stalli llinit nity y index ind ex (CrI) (CrI) was calcul calculate ated d from from the pe perce rcenta ntage ge of  the integra integrals ls of the C4 sig signal nalss cen center tered ed at 89 and 84 pp ppm m pr prese esenti nting ng the crysta crystalli lline ne and amorp amorphou houss phas phase, e, show shown n in Tabl Tablee VII. VII. On Only ly 5% diff differ eren ence ce  between acetate bamboo pulp and acetate wood pulp was found, but the fairly high LOI and crystallite lite siz sizee of ace acetat tatee bamboo bamboo pu pulp lp result resulted ed in good good defin definit itio ion n in th thee C2, C2, 3, 5 re reso sona nanc ncee re regi gion on.. The The sequence valuesspectra for fouriscellulose samples culated byof  13CrI C NMR the same as thatcalof  the values calculated by FTIR analysis. As compared wi with th th thee cr crys ystal talli lini nity ty valu values es ca calc lcul ulat ated ed by th thre reee methods of X-ray analysis, the crystallinity index calculated by   13C NMR spectra shows the lowest relative values for all samples, more similar to the value uess apply applying ing the deconv deconvolu olutio tion n metho method d of X-ray X-ray analysis. The reason is that only material within the TABLE VI Peak Assignment (ppm) of Cellulose Allomorphs in 13 C-CP/MAS NMR Spectra Chemical shift Allomorphs

Figure 9   13C-CP/MAS NMR spectra of (a) acetate bam boo pulp, (b) acetate wood pulp, (c) viscose bamboo pulp, and (d) bamboo fiber.

 Journal of Applied Polymer Science Science DOI  DOI 10.1002/app

Cellulose II Cellulose I  Cellulose  I b Cellulose I  Cellulose  I a Paracrystalline

   

C-1

C-4

C-6

107.1 105.6, 104.1 105.2 104.9

87.7 88.5 89.5 88.8

62.7, 61.2 64.9 nd 65.4

 

HIGH-GRADE BAMBOO DISSOLVING PULP FOR CELLULOSE ACETATE

1037

resolution on enhancement enhancement   13C NMR spectra of (a) acetate bamboo pulp, (b) acetate Figure 10   The C1 and C4 regions in resoluti wood pulp, (c) viscose bamboo pulp, and (d) bamboo fiber.   13

crysta cry stalli lline neectra dom domain ain app appear s stalli asllinit crysta cry lline ne ated ind by C NMR sp spect ra,, and the ears crysta cry nity ystalli cal calcul culate 30 NMR depends on crystallite size. Assuming that microfibrils contain only celluloses and the surface surface effect influences influences only the thickness thickness of one chain, the lateral microfibril size can be determined from the signal intensities of the C-4 region of the spectrum, once a suitable model for the form of the mic microfi rofibri brill crosscross-sec sectio tion n is giv given. en. A simple simple model consists of a microfibril with a square crosssection with (n   1  2) chains per side and an infinite longit lon gitudi udinal nal siz size. e. The crysta crystalli lline ne ind index ex evalu evaluate ated d fr from om soli solid d stat statee NMR NMR meas measur urem emen ents ts,, whic which h is equivalent to the typical ratio of the chain number in crystalline core (n2) to the total amount of cellulose,

of microfi mic rofibr bril il determined siz sizee val values ues by for  13ace acetat tatee bamboo bam boo was and three samples C NMR spectra the same as that of the crystallite sizes calculated by X-ray X-r ay analys analysis, is, bu butt the value valuess calcul calculate ated d by NMR are smaller than those obtained by X-ray diffraction except that of bamboo fiber. The difference observed  between two methods can be a consequence of the hypothes hypo theses es used in the calculation. calculation. The lateral lateral size depends on crystallinity. Indeed, the higher the crystallinity of sample is, the larger the microfibrils lateral eral size size is. is. In th thee hy hypo poth thes eses es us used ed,, amor amorph phou ouss regions were assumed to be limited to the surface of  microfibr micr ofibrils, ils, which is prob probably ably true for the sample having high crystallinity such as bamboo fiber, but not for poorly crystalline samples such as those pulp

was calculated by the following formula. 2   n CrI ¼ nþ2

samples,probably in whichalternate some amorphous and crystalline regions along the microfibril. Secondly, the purity of microfibril is crucial for the size evaluati eval uation. on. The microfibr microfibril il size correlates correlates with the hemic hemicell ellul ulose ose conten content, t, that that is, a larger larger micro microfibr fibril il 33 size correlates with a lower hemicellulose content. Thus the actual microfibril size would be underestimated mate d for sample with low alpha cellu cellulose lose content su such ch as vis viscos cosee bamboo bamboo pu pulp. lp. Mor Moreov eover, er, a sq squar uaree crosssect cros ssection ion was used in the calculation calculations, s, whereas whereas the facts facts are com compli plicat cated ed and var variou iouss sha shape pess for cr cros osss ssec ecti tion on of ac actu tual al micr microfi ofibr bril il are are poss possib ibly ly adopted. In contrast with X-ray analysis,   13C NMR is more sensitive to short-range order.

33

 

The lateral microfibril size was calculated according to the formula   D   5   0.58 (n   1   2), shown in Ta ble VII, where the value 0.58 nm corresponds to the interchain distance.34 It is revealed that the sequence

TABLE VII Crystallinity Indexes (CrI), Contents of Crystalline Allomorphs, and Microfibril Sizes (D) in   13C NMR Spectra of Acetate Bamboo Pulp and Three Samples Samples Acetate bamboo pulp Acetate wood pulp Viscose bamboo pulp Bamboo fiber

CrI (%)   I a  (%)   I b  (%)   D  (nm) 53.8 49.7 43.3 73.6

13.0 15.0 17.5 14.3

60.8 60.7 67.3 68.3

4.35 3.93 3.39 7.86

CONCLUSIONS

In this study, acetate bamboo pulp was prepared by oxyge oxygen-a n-alka lkali li pu pulp lping ing,, xylan xylanase ase and DMD tre treatatments, and H2O2   bleaching. Its properties and struc Journal of Applied Polymer Science Science DOI  DOI 10.1002/app

 

1038

HE, CUI, AND WANG

tures were investigated by different analytical techniques ques,, an and d comp compar ared ed wi with th th thos osee of acet acetat atee wood wood pulp, viscose bamboo pulp and bamboo fiber. Chemical analysis showed the properti properties es of acetate acetate bam boo pulp came up to the requirements requirements for cellulose acetate production, and SEM observation confirmed that lignin and hemicellulose in the surface and the inside were entirely removed. The FTIR results indicated cate d that diffe different rent intermole intermolecula cularr hydrogen hydrogen bond patterns patt erns are likely likely be responsi responsible ble for predomin predominant ant crystalline fibrils in acetate bamboo pulp and bam boo fiber.   13C NMR analys analysis is sho showe wed d cellul cellulose ose   I b al allo lomo morp rph h cont conten ents ts of ac acet etat atee bamb bamboo oo pulp pulp an and d three sample accounted for 61–68%, that is, the same as hardwo hardwood, od, bam bamboo boo cellul cellulose ose was   I b-dominant type. This is coinciding with the results obtained by FTIR and X-ray analysis. A simple mode was used to calcu calculate late crystallite crystallite size of acetate acetate bamboo pulp and thr three ee sample sampless in   13C NMR spectr spectrosc oscopy opy,, and the sequence of the crystallite size values was coincidentt with den with that that obtain obtain by X-ray X-ray dif diffra fracti ction on but the va value luess obt obtain ained ed by   13C NM NMR R we were re smal smalle ler. r. This This   13

indicated indica ted tha thatt in con contra trast st with with X-ray X-ray analys analysis, is, C NMR is more more sensi sensitiv tivee to short short range range order order.. The resul results ts obtain obtained ed by thr three ee metho methods ds all showed showed tha thatt the crystallinity of acetate bamboo pulp was comparable rab le with with tha thatt of ace acetat tatee wood wood pu pulp, lp, but acetat acetatee  bamboo pulp had the higher crystallite size and the higher LOI. Th Thee au auth thor orss than thank k Dr. Dr. Xu Pe Peng ng for for hi hiss help help to pa pape perr writing.

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4. Kazuya, O.; Toru, F.; Yuzo, Y. Compos A 2004, 35, 377. 5. Scur Scurlock locka, a, J. M. O.; Daytonb, Daytonb, D. C.; Hamesb, B. Biomass Bioenergy 2000, 19, 229. 6. Ray, A. K.; Das, S. K.; Mondal, S. J Mater Sci 2004, 39, 1055. 7. Okahisa, Y.; Yoshimura, T.; Imamura, Y. J Wood Sci 2005, 51, 542. 8. Focher, B.; Palma, M. T.; Canetti, M.; Torri, G.; Cosentino, C.; Gastaldi, Gasta ldi, G. Ind Crops Prod 2001, 2001, 13, 193. 9. Wada, M.; Okano, T.; Sugiyama, J. J Wood Sci 2001, 47, 124. 10. Evtuguin, D. V.; Neo, C. P. Pulp Paper Sci 1998, 24, 133. 11. Lee, C. L.; Hunt, K.; Murray, R. W. J Pulp Paper Sci 1994, 20, 125. 12. Hunt, K.; Lee, C. L. J Pulp Paper Sci 1995, 21, 263. 13. Hunt, K.; Lee, C. L.; Bourbonnais, R.; Paice, M. G. J Pulp Paper Sci 1998, 24, 55. 14. Segal, L.; Creely, L.; Martin, A. E.; Conrad, C. M. Textile Res J 1959, 29, 786. 15. Ahtee, M.; Hattula, T.; Mangs, J.; Paakkari, T. Paperi Ja Puu 1983, 8, 475. 16. Li, S. H.; Zeng, Q. Y.; Xiao, Y. L.; Fu, S. Y.; Zhou, B. L. Mater Sci Eng C 1995, 3, 125. 17. Timell, T. E. Wood Sci Technol 1967, 1, 45. 18. Neal, J. L. J Appl Polym Sci 1965, 9, 947. 19. Steinmann, H. W.; White, B. B. Tappi 1954, 37, 25. 20. Watson, J. K.; Henderson, D. R. Tappi 1957, 40, 686. 21. Conca, R. J.; Hamilton, J. K.; Kircher, H. W. Tappi 1963, 46, 644. 22. Ouajai, Ouajai, S.; Shanks, R. A. Polym Degrad Stabil Stabil 2005, 89, 327. 23. Fengel, D. Holzforschung 1992, 46, 283. 24. Foche Focher, r, B.; Naggi, Naggi, A.; Tor Torri, ri, G.; Cosani Cosani,, A.; Ter Terboj bojevi evich, ch, M. Carbohydr Polym 1992, 17, 97. 25. Hinterstoisser, B.; Salmen, L. Cellulose 1999, 6, 251. 26. Ritcher, U.; Krause, T.; Schempp, W. Angew Macromol Chem 1991, 1851186, 155. 27. Akerhol Akerholm, m, M.; Hinterstoisse Hinterstoisser, r, B.; Salmen, Salmen, L. Carbohyd Carbohydrr Res 2004, 339, 569. 28. Oh, S. Y.; Yoo, D. I.; Shin, Y.; Kim, H. C. Carbohydr Res 2005, 340, 2376. 29. Wickholm, K.; Larsson, P. T.; Iversen, T. Carbohydr Res 1998, 312, 123. 30. Maunu, Maunu, S.; Liitia, Liitia, T.; Kaulioma Kauliomaki, ki, S.; Sundquist, Sundquist, J. Cellulose Cellulose 2000, 7, 147. 31. Newman, R. H. J Wood Chem Technol 1994, 14, 451. 32. Atalla, R. H.; VanderHart, D. L. Solid State Nucl Magn 1999, 15, 1. 33. Heux, L.; Dinand, E.; Vignon, M. R. Carbohydr Polym 1999, 40, 115. 34. Rondeau-Mouro, C.; Bouchet, B.; Pontoirea, B.; Robert, P. Car bohydr Polym 2003, 53, 241.