IBN AL- HAITHAM J. FO R PURE & APPL. SC I. VOL. 23 (1 ) 2010 Chitosan and Keratin Hydrolysate Treatment of Archived Newsprint K. A. AL- Karagholy Departme nt of Chemistry, College of Education Ibn Al-Haitham Unive rsity of Baghdad Abstract The st udy is focused on the modification of the st andardized newsp aper with natural p olymers chitosan and keratin hy drolysate app lied on the p aper surface from p olymer solution. This modification is based p articularly on the formation of the comp lexes between acidic surface group s on cellulose fibers and the natural p olymers which imp roved the mechanical p rop erties of the p aper and the p ositive results which were observed p articularly in folding endurance of the newsp aper. Key words: newsp rint; chitosan; keratin; mech anical p rop erties Introduction The main p roblem in st oring old papers, books and documents, is their degradation which due to the fact that some of the residual chemicals remaining in the p aper from the p aper manufacturing p rocess react with moist ure p resent either in the air or in the p aper to form reaction p roducts. These reaction p roducts, generally sulp huric acid, degrade the cellulose causing p aper britt leness, cracking and y ellowing. Therefore, numerous p rocesses were p rop osed for treating p aper in order to stop or retard degradation. M ost ly these processes are based on deacidification of p aper, for examp le the gaseous treatment with diethy lzink [1], magnesium ethanolate and titanium ethanolate used in the Batelle p rocess, or the Bookkeep er p rocess with magnesium oxide microparticles [2]. Usualy these processes use inorganic comp ounds and only few references are found on use of environmentally friendly comp ounds as natural p olymers, e.g. chitosan and Keratin . Chitosan is a weak cationic p olysaccharide comp osed essentially of ß (l → 4) linked glucosamine units t ogether with some N-acety lglucosamine units. It is p roduced by extensive deacety lation of chitin, p olysaccharide common in nature. Chitosan is biocompatible, biodegradable, and nontoxic natural p olymer with excellent film-forming ability . Chitosan was shown as an excellent dry st rength additive either in acidic or neutral condition, but it was less effective under alkaline conditions [3]. It means, chitosan has a p otential to be used as a dry st rength additive in neutral, acidic or alkaline conditions depending on the p rocess requirements. The st udies on p aper modification follow effects of different p olymer solutions, e.g. chitosan and p olyvinyl alcohol (PVA), on mechanical p rop erties of p aper sheets. It was shown that the imp rovement of the mechanical p rop erties of the treated p aper sheets by chitosan solutions is higher in comp arison with the other p olymer solutions. The same was st ated for heat resistance of treated p aper sheet by chitosan [4]. As a result of its cationic character, chitosan is able to react with p olyanions forming p olyelectrolyte comp lexes (PECs) [5]. Therefore, chitosan has the affinity of adsorbtion on cellulose fibres during wet modification of p aper sheet. It is known, that the p erformance of materials with certain bulk p rop erties can be changed or op timized by thin p olymer lay ers adsorbed on their surfaces. The scop e of that working area is to create and op timize p olyelectrolyte (PEL) based surface modification concepts. For that charged surface group s are used, which are already p resent on the material or are generated by various p retreatments like plasma or chemical modification techniques[6]. IBN AL- HAITHAM J . FO R PURE & APPL. SC I VO L. 23 (1) 2010 Keratins are a family of fibrous st ructural proteins; tough and insoluble, they form the hard but nonmineralized st ructures found in reptiles,birds, amp hibians and mammals, and they are the main constituent of st ructures t hat grow from the skin: -the α-keratins in hair, horns, nails, claws and hooves of mammals. -the harder β–keratins found in nails and in the scales and claws of reptiles,their shells, and in the feathers, beaks,and claws of birds(these keratins are formed p rimarily in beta sheets.However beta sheets are also found in α-keratins )[7]. PECs did not change their 3D-structure up on dry ing. It was found that the swollen 3D st ructure of the comp lexes is achieved by incorp orating large amount of water into the comp lexes [8]. In the present work, chitosan and keratin hy drolysate are used as t he modifiers of the newsp aper sheets. Experimental Materials Ne wspaper Newsp aper with t he basic weight 45 g/m 2 , groundwood machine p aper, unsized, pH of the cold extract 4.5 - 5.0. Chitosan The chitosan used in this st udy was a commercial p roduct Sigma-Aldrich, low molecular weight, degree of deacety lation 75 to 85%. Used in the form of 2 wt. % water solution (p H 5.5 - 6.0). Keratin Hydrolysate M ade from ship wool, the alkali solution with p H 10. T he dry matter content 12%. Procedure The solution of chitosan (CH) and keratin (K) or both together were app lied by using the glass roller on the newsp aper. The modified p aper was consolidated 24 hours. Further it was conditioned before measurements under temperature 23°C and humidity 47.8 %. The keratin - chitosan (K-CH) solution was p repared by mixing both biopolymers (1:5 v/v). The sandwich like coating (K+CH) was realized by coating the p aper first with the keratin solution (K) and after drying with the chitosan solution (CH). S canni ng e lectron mi croscopy The morphology of the modified p aper samples was evaluated by using the scanning electron microscopy (Tesla BS 300 SEM microscope with digital microscopy imaging TESCAN). Mechanical propertie s Tensile st rength of the treated newsp aper was measured by the INSTRON 1122 testing instrument (STN ISO 1924-2: Paper and board. Determination of tensile prop erties). The fold endurance was measured by the double bending technique using Schopp er instrument (STN ISO 5626: Paper). Accelerated aging Prop erties of unmodified and modified p apers were st udied also after the dry thermal accelerated aging at 105°C. The samp les were p laced to the air-drying chamber for 12 days. Re sults and Discussion The standardized newsp aper served as a model substrate for the archive documents in this st udy . Lignocellulosic fibres p ossess generally a negative charge that is att ributed to the dissociation of carboxy lic group s of cellulose and hemicellulose comp onents. It is p ost ulated IBN AL- HAITHAM J . FO R PURE & APPL. SC I VO L. 23 (1) 2010 that p ulp st rength p rop erties are related to the acidic group s which are sp ecifically located on the surface of fibres [9]. The surface charge is observed to correlate with tensile strength. The situation is changed by modification with PELs, which form polyelectrolyte complexes (PEC) on fibres surfaces. T he idea was to imp regnate the p aper, and to p enetrate p olymer solutions through the paper structure. The treatment should lower acidity as well as increase mechanical p rop erties of the p aper. The solutions of chitosan, keratin or combination of both, were app lied uniformly on the surface by using the sp ecial technique of the deposition from the glass roller. The gravimetric analysis showed that about 2.80 ± 0.34 g/m 2 of these p olymers were seized in the paper structure. The addition of biopolymers which were used increased the mechanical p rop erties of the p aper. Fig. 1 shows the tensile st rength imp roving of the newsp aper sheet p articularly after the modification with chitosan or keratin, resp ectively. The imp rovement is quantified by the coefficient, which exp resses the relative change of the measured value after modification against the measured value of the st andard. In both cases, tensile st rength is increased about 30%. Tensile st rength is increased also for the p aper modified with amixed solution of keratin and chitosan (K-CH), and p aper is modified first with keratin and after dry ing with chitosan (K+CH). Dramatic changes can be seen following the folding endurance of the modified p apers in Fig. 2. The notable increase is observed esp ecially in double folds for the sheets modified with both chitosan and mixture chitosan-keratin. Whereas keratin increased the double folds threefold, in case of chitosan it was eightfold. It means, p articularly chitosan can be proved as an effective mediator of fiber-water interaction in the p aper structure. The treatment of the paper with the chitosan-keratin solutions connected with comp lexes and bonds formation results in a quite dense film on the surface of cellulose fibres. Comparing the p ictures from SEM in Figure 3, a different surface morphology can be seen after treating the paper with chitosan-kertain solution and sequential treating first with keratin and after with chitosan. The formation of a dense elastic film on the fibres surface could exp lain an increase in folding endurance, p articularly through a chitosan effect. Keratin, which is in fact keratin hy drolysate with a low molecular weight, itself forms fragile films. This is manifest ed by the lower folding endurance of such modified p apers. Regarding film st ructure and st udy ing a model for archive materials, the conditions (temp erature, humidity ) under which the documents are p reserved in the archive must be taken into consideration.These conditions are favourable for keep ing functionality of comp lexes between chitosan and cellulose. It is well known that the glycosidic links of cellulose are st able in a neutral or weakly alkaline medium. On the other hand, they become rapidly hy drolysed in the p resence of a st rong acid or a st rong base. From that reason, the p rocess of deacidification is a fundamental p rocess for the conservation and the restoration of the archive documents. Therefore, the use of alkalic keratin hy drolysate solution for the modification in the combination with a mild acidic chitosan solution should shift the total p H to neutral or milder alkali region. On the other hand, it was p ossible to p repare the mixture of keratin with chitosan only in the ratio 1:5 because a higher concentration of keratin in the mixture caused the p recipitation of chitosan from solution. From Fig. 4, it is evident that the app lying of chitosan solution slightly moved the acidity of the original p aper to anear neutral region. This is close to the p H value 6.5 measured for the chitosan solution. Keratin alone deacidified the p aper and moved p H to the alkaline region p H = 9.8. Combination of chitosan and keratine (K-CH) can give a p rotective lay er, which keep s neutral environment in paper (pH = 7.1). Conclusion Concluding the results from the modification of anewsp aper with the natural p olymers chitosan and keratin, this modification is based p articularly on the formation of comp lexes between acidic surface group s on cellulose fibres and natural p olymers which can be IBN AL- HAITHAM J . FO R PURE & APPL. SC I VO L. 23 (1) 2010 successfully app lied in treating the archive cellulosic materials. M oreover in searching alternatives for p rofessional conservators in the st ruggle against fungi that eteriorate p aper documents, chitosan can be used due to its antifungal effect. Re ferences 1. Porck,H. (1996)M ass deacidification: An Up date of Possibilities and Limitation, Europ ean. Commission on Preservation and Access. Amst erdam. 2. Bucanan, S. (1994) An Evalu ation of the Bookkep er M ass Deacidification Process: Technical Evaluation team rep ort for the Preservation Directorate, Library of Congress, Washin gton. 3. Lertsutthiwong,P.; Chandrkrachang,S. ; Nazhad,M . M . and Stevens,W.F. (2002) Chitosan as a Dry Strength Agent for Paper, App ita Journal 55(3): 208. 4. Kamel,S.; El-Sakhawy , M .. and Nada, A. M . A. (2004) Thermochim. Acta 421( 1-2): 81- 85. 5. Peniche,C. ; Ar guelles-M onal, W. ;Peniche, H. and Acost a, N. (2003) M acromolecular Bioscience 3(10): 511 -520. 6. Wagberg,L.and Hagglund,R. (2001) Kinetics of p olyelectrolyte adsorption on cellulosi c fibres,Langmuir 17(4): 1096-1103. 7. Krep lak, L. ; Doucet,J. and Briki, F. (2004) New asp ects of alp ha-helix to beta-sheet transition in stretched hard alpha-keratin fibers.Biop hy s J . 87:640-647. 8. Gardlund,L. (2006)Poly electrolyte Comp lexes: Their Characterization and use for M odification of Wood Fibre Surfaces, Publisher: KTH, Fibre and Polymer Technology , Stockholm, http://urn.kb.se/resolve?urn:nbn :kth:diva-4225 9. Amp ulski, R.S.( 1985) in: Tappi Papermakers Conference proceedin gs, Denver , 9-16. ة المجلد 2010) 1( 23مجلة ابن الھیثم للعلوم الصرفة والتطبیقی معاملة ورق الصحف المحفوظة مع الكیتوسان والكیراتین كریمة عبد الرزاق القره غولي جامعة بغداد ،ابن الهیثم -كلیة التربیة ،قسم الكیمیاء ةصالخال احداث تعدیل في نوعیة ورق الصحف القیاسیة عـن طریـق تعـریض سـطح هـذا الـورق ركزت هذه الدراسة على امكانیة .الكیتوسان والكیراتین ، لمحلول البولیمرین الطبیعیین ویعـود هـذا التـأثیر الـى .وقد ظهر التأثیر األیجابي لهذین البولیمرین جلیا وبصـورة خاصـة فـي ازدیـاد تحمـل الـورق للطـي .سطح الیاف السلیلوز للورق وهذین البولیمرین الطبیعیین فيامیع الحامضیة تكوین معقدات بین المج