Carbohydrate Polymers

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1 Crohydrte Polymers 94 (213) Contents lists ville t SciVerse ScienceDirect Crohydrte Polymers jo u rn l hom ep ge: Improving wet nd dry strength properties of recycled old corrugted crton (OCC) pulp using vrious polymers Yhy Hmzeh, Snz Sghi, Alirez Ashori,, Ali Adulkhni, Frshid Soltni Deprtment of Wood nd Pper Science nd Technology, Fculty of Nturl Resources, University of Tehrn, Krj, Irn Deprtment of Chemicl Technologies, Irnin Reserch Orgniztion for Science nd Technology (IROST), P.O. Box 8-338, Tehrn, Irn r t i c l e i n f o Article history: Received 2 Octoer 212 Received in revised form 2 Jnury 213 Accepted 13 Jnury 213 Aville online 4 Ferury 213 Keywords: Chitosn Ctionic strch Wet-strength Old corrugted crton Poly (vinyl lcohol) s t r c t In this study, the ppliction of different dosges of low nd high moleculr weights (MW) of chitosn (Ch), ctionic strch () nd poly vinyl lcohol () were systemticlly investigted using old corrugted crton (OCC) furnishes. Vrious sequences of ove-mentioned polymeric dditives were lso exmined to find out the optiml comintion for improving oth wet nd dry tensile strength. For ech tretment, 4 hndsheets, ech hving sis weight of 1 g/m 2, were mde. In generl, the tensile strength of hndsheets ws significntly ffected y the ddition of polymeric gents. The enhncing effect of dditives on dry tensile property ws much higher thn wet condition. The results lso showed tht the tensile strength of the smples mde from OCC furnishes were improved upon the ddition of high moleculr weight chitosn () compred to the untreted ones (control). The low MW chitosn did not chnge the properties of hndsheets drmticlly. Appliction of polymeric gents modertely decresed the stretch to rupture, however with incresing dosge the stretch ws improved. Sequentil ddition of used polymers showed tht triple ppliction of polymers ws eneficil to oth dry nd wet tensile strength, lthough the effect ws lrger for dry. The est results in wet nd dry tensile strengths were chieved using sequentil of --. Sequentil ddition of oppositely chrged polymers forms mcromoleculr lyered structure of polyelectrolytes. 213 Elsevier Ltd. All rights reserved. 1. Introduction In recent yers, the vilility of wood-sed pulps hs een of gret concern. Extensive reserch hs focused on exploring suitle sustitute for conventionl forest sed mterils used in ppermking mnufctures (Ftehi, Tutus, & Xio, 29). Among the possile lterntives, the development of pulp nd pper using recycled pper is currently t the center of ttention (Ghsemin, Ghffri, & Ashori, 212). Tody, the ppliction of wste pper is stedily incresing in the world, due to the environmentl concerns, popultion growth nd the shortge of wood supply. Old corrugted crton (OCC) pper is the most significnt ctegory of wste ppers for recycling, sed on the percentge of recovery rte nd y tonnge (Ashori & Nourkhsh, 28). However, y incresing the numer of cycles in the fier recycling, the strength of ppers is grdully reduced, which is minly due to the decrese in the fier onding strength through the hornifiction phenomenon (Hmzeh, Njfi, Hue, Slehi, & Firouzdi, 212). It hs een climed tht the strength of such recycled fiers is not sufficient to meet the industry s demnd; thus, the strength should e improved. Corresponding uthor. Tel.: ; fx: E-mil ddress: shori@irost.org (A. Ashori). One pproch to improve the strength of recycled fiers is to use dry strength dditives. They re usully wter solule, hydrophilic, nturl or synthetic polymers. The most common chemicls used commercilly re ctionic strch () nd polyvinyl lcohol (). Dry-strength polymers cn interct with fiers in numer of wys. In order of incresing ond strength, these interctions re generlly termed s vn der Wls forces, hydrogen onding, ionic ttrctions nd covlent ond formtion. The mjority of pper strength dditives function on the first two of these energy levels, relying primrily on multiple hydrogen ond formtion for their retention nd effectiveness. Strch, for exmple, which hs sufficient moleculr size to spn inter-fier distnces nd lso hs proclivity for forming hydrogen onds with cellulosic mterils, clerly functions y incresing the numer of low energy onds etween fiers. In order to gin good retention nd improve the efficiency of strch utiliztion on ppermking fiers, ctionic strch ws developed (Mlton, Kuys, Prker, & Vnderhoek, 1997), which promotes strong dsorption onto fiers, fines nd fillers through electrosttic ttrction to the nionic groups on the surfce of the fiers nd prticles. led penetrtion, high inding strength, nd reduced effluent lods re importnt enefits tht re often derived from the use of ctionic strch (Glittenerg & Becker, 1998). Poly (vinyl lcohol) (), which is one of the most dominnt polymers, hs severl pplictions in ppermking processes /$ see front mtter 213 Elsevier Ltd. All rights reserved.

2 78 Y. Hmzeh et l. / Crohydrte Polymers 94 (213) is widely recognized s one of the strongest inders ville in the pper industry, nd depending on its moleculr weight, cn e 3 4 times stronger thn strch (Ftehi et l., 29). Due to the presence of hydroxyl groups in every repeting unit of, it ppers to e one of the est polymers to reinforce cellulose fiers (Pelton, 24). In ddition, it hs excellent film forming potentil (Lertsutthiwong, Nzhd, Chndrkrchng, & Stevens, 24). cn tie down the fines nd help ind filler prticles to the fier, oth of which re dvntgeous in printing ppers. In ppermking, is used for surfce sizing to form films with very high tensile strength nd high degree of trnsprency, flexiility nd oil resistnce (Briscoe & Luckhm, 2). cn lso e mixed with strch nd pplied t size press (Zkrjšek, 28). In ppermking, chitosn hs een found to e effective s dry nd wet strength gent (Lleg & Pikulik Ivn, 1991; Lertsutthiwong, Chndrkrchng, Nzhd, & Stevens, 22; Ashori, Jlluddin, Wn, Zin, & Mohd Nor, 26) s well s in coting (Kjellgren, Gällstedt, Engström, & Järnström, 26), sizing (Lleg & Pikulik Ivn, 1992; Lertsutthiwong et l., 24; Ashori, Rverty, Vnderhoek, & Wrd, 28), nd retention (Li, Du, & Xu, 24). Chitosn, iodegrdle, nontoxic, nticteril, s well s renewle resource, is the second most widespred nturl polyscchride (Li, Du, Xu, Zhn, & Kennedy, 24). It is the cid-solule decetylted derivtive of chitin, prepred y recting chitin with n queous hydroxide solution (Fig. 1 nd ). Chitin nd chitosn elong to very interesting fmily of -(1 4) linked polyscchrides. This kind of glycosidic linkge leds to reltively extended nd rigid structures in the solid stge, prticulrly in the dry stte (Kumr & Mjet, 2). The primry structure of chitosn is similr to cellulose except tht the C-2-hydroxyl group of cellulose is replced y n mino group (Lleg & Pikulik Ivn, 1993). Chitosn is insolule in wter under lkline conditions, ut ecuse of its primry mino groups it is solule in cidified wter (Fig. 1c). The first nd importnt gol of the pper production is to mke product with the customer demnded qulity specifictions s economiclly s possile. This requires good runility of pper mchine tht is often evluted y the numer of we reks in proportion to production speed. Most frequently, the pper we reks occur fter couch roll when wek wet we is trnsferred unsupported etween two mchine prts in so-clled open drw. Wet we strength cn e developed y incresing the fine nd long fier proportion in furnish, pulp refining, nd solid content of sheet (Ferreir & Guimrães, 23). Despite the significnt effect of wet-we strength of runility of pper mchine, in the pst very few ttempts hve een mde to increses the wet-we strength (WWS) of pper y chemicl dditives (Lleg & Pikulik Ivn, 1991, 1992). The improvement of wet pper we strength, nd consequently enhncing pper mchine runility through the vrious chemicl dditives, hs received gret ttention in recent yers oth from cdemics nd ppermkers (Tejdo, Miro, & vn de Ven, 211; Ktj-ho, Hvisto, Asikinen, Hyvärinen, & Vuoti, 211). In this work, different dosges of chitosn,, nd ctionic strch were individully dded to the OCC furnish nd the hndsheet properties in terms of dry nd wet tensile nd stretch properties were investigted. In ddition, vrious sequences of comintion of polymeric dditives were exmined to find the optiml comintion for improving oth wet nd dry strength. 2. Mterils nd methods 2.1. Mterils The lignocellulosic mteril used for this study ws OCC recycled pper which ws otined from locl recycling pper mill. The OCC pper ws clened nd dispersed in the disintegrtor, fter which it ws fluffed nd refrigerted until use. Fig. 1. Chemicl formuls of chitin (), chitosn (), nd chitosn cette form (c). Four dditives used in this study were: chitosn (Ch) with two different (low nd high) moleculr weights, ctionic strch () nd. The chrcteristics of used polymers re presented in Tle 1. All stock solutions were freshly prepred to void ny possile degrdtion Appliction of polymers In this work, the chitosn solution ws prepred y dissolving chitosn in queous 1% (w/w) cetic cid t room temperture y stirring for 8 h, wheres the ws prepred y dissolving powder in distilled wter nd heting on hot plte with mgnetic stirrer t 7 7 C for 2 min. The ctionic strch ws prepred y suspending strch powder in distilled wter nd heting to 9 C on wter th with periodic stirring, nd then holding the suspension t this temperture for 3 min fter the onset of geltiniztion. The solutions were then diluted with distilled wter, nd refrigerted prior to use.

3 Y. Hmzeh et l. / Crohydrte Polymers 94 (213) Tle 1 Chrcteristics of the used polymeric mterils. Prmeter Ch I Ch II Source Shrimp shell Shrimp shell Potto ph Viscosity, cp Soluility, % Ash content, % Moisture content, % Moleculr weight, D Degree of decetyltion, % >7 7 8 Supplier Sigm Aldrich Sigm Aldrich Lyckey Amylex Sigm Aldrich Chitosn ws pplied in dosges of.%, %,.7% nd %, while ctionic strch ws used in dosge of %, 1%, % nd 2% sed on oven dried weight of the pulp. In ddition, three concentrtions (1%, 2% nd 3% sed on oven dried weight of the pulp) of PVC were pplied long with vrious mixtures of dry strength dditives to compre the results. In the cse of mixture, 6 different orders of polymers with dosges of % chitosn, % ctionic strch nd 1% were used. Different dosge solutions of dditives were dded to 1 ml of stock t 3% consistency of uneten OCC pulp. The mixture ws gitted for 2 min t room temperture ( C). In the cse of mixture of dditives, fter ddition of ech gent the suspension ws mixed for 3 min nd other dditives were then dded. Susequently, the suspension ws diluted with distilled wter to % consistency Sheet formtion nd pper testing After mixing the pulp suspension, hndsheets with trget weight of 1 g/m 2 were mde in British hndsheet former s per TAPPI Stndrd T 2 sp-2. For determintion of dry strength properties, the smples were conditioned t ± 2% reltive humidity nd 23 ± 1 C temperture ccording to TAPPI T 42 sp-98 for t lest 4 h nd then, the dry tensile nd stretch properties of hndsheets were tested ccording to ISO Five replictions were tested for ech tretment. For wet strength, the tensile nd stretch properties of preformed (treted) hndsheets were determined ccording to ISO , just fter they were removed from the sheet mold. At this point the sheet contins out 3 6% solid content. More thn twenty replictions were tested for ech tretment nd dry solid content of ll smples ws determined y weighting the smples in wet nd dry sttes. It is lso worth mentioning tht n exponentil function ws fitted to dt from strength responses otined from employing the comined polymers nd strength response normlized to constnt dry solid content for nlysis. In order to simplify the experiments no other dditions, such s lum nd AKD, were dded to the slurry. 3. Results nd discussion 3.1. Effect of polymers on pper properties Dt on wet tensile nd stretch properties of sheets treted y four distinct polymeric dditives re presented in Figs. 2 nd 3, wheres Fig. 4 shows the sme properties in dry condition. In generl, the ddition of dditives in ny concentrtions considerly enhnced tensile strength of the hndsheets in wet nd dry conditions, compred with the untreted ones (control). The results demonstrte tht the ddition of oth types of chitosn cn increse oth wet nd dry tensile strength remrkly. In ddition, chitosn ppliction hs unique effect on the strength property compred with ctionic strch nd treted ppers; for instnce, t 1% dosge of chitosn II, the increse in tensile strength ws out 4% more thn the control smple. A similr trend ws oserved for chitosn I treted smples (Fig. 2). However, the increse eyond.7% ws less. Incresing the concentrtion of chitosn from.7% resulted in % gin in strength, ut dding more chitosn (i.e..7 %) gve only out 1% increse in strength properties compring to.7% chitosn ddition (Fig. 2). This indictes tht chitosn should e used sed on end-product qulity requirements nd the cost effectiveness of the process. These results re in good greement with previous findings using chitosn (Lertsutthiwong et l., 24; Ashori et l., 26). The differences in the performnce of employed chitosns is presumly due to the differences in the polymer moleculr weight, while longer chitosn (Ch I) produces further contcts etween fiers thn shorter chin chitosn (Ch II). Dry tensile properties incresed when the ove-mentioned dditives were dded to the pulp furnish. Similr to wet condition, the effect of chitosn with low concentrtions (. 1%) on the tensile properties of hndsheets ws etter thn other dditives (Fig. 4 nd ). For instnce, t 1% chitosn ddition, the increse of dry condition in tensile index nd stretch were out 22% nd 7% more, respectively, thn the corresponding increses under wet conditions. This cn e explined y the fct tht chitosn cn enhnce the internl onding strength of pper y creting dditionl onds. As the ionized mino groups of chitosn come into contct with fiers, in the presence of wter they cn form ionic nd imino onds (Fig. ). The mechnicl properties of pper depend on inter-fier onding, nd so it is most prole tht chitosn exerts its eneficil effects on pper y incresing the inter-fier ond strengths. The structurl configurtion of chitosn might explin some of the differences in performnce when compred with nd ctionic strch. The primry chemicl structures of chitosn nd re liner polymer chins, while strch is composed of mylopectin, which is rnched. Strch hs -linkge, which cuses it to tke helicl form, while chitosn hs -linkge, which trnsltes it into stright moleculr chins. These chins re more conformle, which fcilitte ccessiility of their functionl groups for onding to cellulose surfce. Furthermore, oth chitosn nd ctionic strch posses mino or mmonium groups, which give strong ctionic chrcter to chitosn nd ctionic strch, while does not contin this functionlity. is nonionic in chrcter. Amide onds my lso develop during drying. Such interctions would improve the internl ond strength nd resistnce of pper to wter (Lleg & Pikulik Ivn, 1993). Figs. 3 nd 4 show the stretch to rupture of hndsheets produced y following tretment with chitosn, ctionic strch nd in wet nd dry conditions, respectively. In wet cse, the results demonstrte tht the stretch vlues of treted smples t reking point were less thn the control, however with incresing the concentrtion of dditives, stretch ws improved. For instnce t 3% dryness, the stretch vlues were 1% nd % for dosges of % nd 1% chitosn treted smples, respectively. Similr stretch ehvior took plce in the wet condition for ll dditives (Fig. 3),

4 8 Y. Hmzeh et l. / Crohydrte Polymers 94 (213) Mx. tensile strength (N) Ch I (.%) Ch I (%) Ch I (.7%) Ch I (1%) Ch II (.%) Ch II (%) Ch II (.7%) Ch II (1%) Mx. tensile strength (N) c d Mx. tensile strength (N) (1%) (2%) (3%) (%) (1%) (%) (2%) Mx. tensile strength (N) Dryness (%) Dryness (%) Fig. 2. Effect of incresing dditives content nd dryness on wet tensile strength. Ch I (.%) Ch I (%) Ch I (.7%) Ch I (1%) Ch II (.%) Ch II (%) Ch II (.7%) Ch II (1%) c (2%) (3%) (1%) d (%) (1%) (%) (2%) Dryness (%) Dryness (%) Fig. 3. Effect of incresing dditives content nd dryness on wet stretch property.

5 Y. Hmzeh et l. / Crohydrte Polymers 94 (213) c Ch I content (%) d Ch II content (%) content (%) 2 1 content (%) Fig. 4. Effect of incresing dditives content on dry tensile nd stretch properties. In contrst to the wet conditions, ll treted smples showed superior stretch vlues t dry condition compred with control (Fig. 4). In cse of, the increse in stretch ws significntly lower thn ctionic strch nd chitosn treted ppers. Once gin, chitosn treted ppers with the lowest concentrtion hd the highest vlues. As in the cse of ctionic strch, the effect ws higher when the dosge of polymer ws higher Effects of sequentil polymer ddition Fig.. The formtion of ionic nd imino onds etween chitosn nd pulp fiers. ut, chitosn I nd II with the lowest concentrtion could show the highest stretch vlues. As mentioned erlier, the reson for this phenomenon is ttriuted to the differences originting from the chemicl nture. In this work, vrious sequences of polymeric dditives were exmined to find the optiml comintion for improving oth wet nd dry strength. Figs. 6 nd 7 show the tensile nd stretch properties of hndsheets produced t wet nd dry conditions, respectively. In generl, the ddition of polymers in ny sequences considerly incresed tensile strength of the hndsheets compred with the untreted ones (control). This indicted tht the dry strength properties of OCC pulp were significntly improved when the pulp ws treted y ll sequentil chemicl dditions. However, the Mx. tensile strength (N) Dryness (%) Dryness (%) Fig. 6. Influence of sequentil polymer ddition nd dryness on wet tensile nd stretch properties.

6 82 Y. Hmzeh et l. / Crohydrte Polymers 94 (213) (N.m/g) Mx. tensile strength (N) () Tensile properties for specimens treted with ll types of dditives were generlly higher thn untreted ones (control). () The ddition of chitosn hd more positive effects on the tensile strength, compred to sheets treted with ctionic strch nd. (c) The ddition of chitosn incresed oth wet nd dry tensile strength remrkly. However, the rte of increse ws higher from to % compred to.7 1% regrdless of the moleculr weight. (d) Convincing results demonstrted tht high moleculr weight chitosn (Ch I) performed more efficiently on wet nd dry strength enhncements of ppers. (e) The stretch vlues of the sized ppers modertely decresed, however it ws improved with incresing the dosge of dditives. (f) These mterils ond well to the fier surfces nd re cple of ridging inter-fier distnces, therey estlishing onds etween fiers nd firils tht would not hve otherwise formed. (g) Dry tensile property ws significntly improved with sequentil polymer ddition. The optiml sequence ws found to e - -. References Fig. 7. Influence of sequentil polymer ddition on dry () nd wet () tensile nd stretch properties. sequence of -- nd followed y -- showed the superior results for oth wet nd dry conditions. As it cn e seen from Fig. 7, the enhncing effect of dditives on dry tensile index is much higher thn wet condition. Becuse of significnt correltion etween wet we rek nd comined wet we strength nd stretch (Uesk & Ferhi, 1999), the potentil of chemicl tretments to enhnce the runility of wet we in pper mchine ws estimted sed on the comined fctor of (tensile strength nd stretch ). In Fig. 7, sequentil tretment of fier y -- nd followed y -- showed clerly etter results, since they hve oth produced higher tensile strength nd cused lower reduction in stretch compred to the control. Ktj-ho et l. (212) reported tht sequentil ddition of oppositely chrged polymers forms mcromoleculr lyered structure of polyelectrolytes; so-clled polyelectrolyte multilyers (PEM). The PEM hve een found to increse the moleculr contct re in the fier fier joints. It hs lso een found tht these multilyers crete lrger numer of fier fier contcts in the sheet. The use of polyelectrolyte multilyers hs een shown to increse dry-pper strength with only minor reduction in density, lightscttering, or the formtion of the sheet. The increse in strength hs een demonstrted to e lrgely dependent on the dsorption of these polymers, which is ffected y severl prmeters, such s electrolyte concentrtion, the type of electrolyte, nd the chrge density (Slminen et l., 211). 4. Conclusions The use of recycled fiers is stedily incresing in vrious pper products nd there is need to improve the strength properties of pper products mde from these fiers. Using dry strength dditive is potentil solution. Hence, in this study some polymeric dditives were used to enhnce tensile strength of OCC recycled pper. Some conclusions of ddition of dry strength gents re s follows: Ashori, A., & Nourkhsh, A. (28). A comprtive study on mechnicl properties nd wter sorption ehvior of fier-reinforced polypropylene composites prepred y OCC fier nd spen fier. Polymer Composites, 29(), Ashori, A., Jlluddin, H., Wn, M. D., Zin, W. Y., & Mohd Nor, M. Y. (26). Enhncing dry-strength properties of kenf (Hiiscus cnninus) pper through chitosn. Polymer-Plstics Technology nd Engineering, 4(1), Ashori, A., Rverty, W. D., Vnderhoek, N., & Wrd, J. V. (28). Surfce topogrphy of kenf (Hiiscus cnninus) sized pper. Bioresource Technology, 99(2), Briscoe, B., & Luckhm, P. (2). The effects of hydrogen onding upon the viscosity of queous poly(vinyl lcohol) solutions. Polymer, 41(1), Ftehi, P., Tutus, A., & Xio, H. (29). Ctionic-modified s dry strength dditive for rice strw fiers. Bioresource Technology, 1(2), Ferreir, P. J., & Guimrães, N. M. (23). Effect of softwoods on the wet-we strength of. E. gloulus leched krft sed furnishes. In Proceedings of the 28th Eucep Conference Lison, Spin. Ghsemin, A., Ghffri, M., & Ashori, A. (212). Strength-enhncing effect of ctionic strch on mixed recycled nd virgin pulps. Crohydrte Polymers, 87(2), Glittenerg, D., & Becker, A. (1998). Ctionic strches for surfce sizing. Pper Technology, 39(1), Hmzeh, Y., Njfi, S. M. H., Hue, M. A., Slehi, K., & Firouzdi, M. R. D. (212). Recycling potentil of unleched nd leched chemicl pulps from juvenile nd mture wood of Populus deltoids. Holzforschung, 66(2), 161. Ktj-ho, J., Hvisto, S., Asikinen, J., Hyvärinen, S., & Vuoti, S. (211). The influence of ctionized irch xyln on wet nd dry strength of fine pper. Bioresources, 7(2), Ktj-ho, J., Slminen, K., Rntnen, T., Retulinen, E., Lindqvist, H., & Sunderg, A. (212). The effect of sequentil polymer ddition on wet- nd dry-we mechnicl chrcteristics: Lortory, semi-pilot, nd pilot studies. In Proceedings of TAPPI PperCon Conference New Orlens, USA. Kjellgren, H., Gällstedt, M., Engström, G., & Järnström, L. (26). Brrier nd surfce properties of chitosn-coted greseproof pper. Crohydrte Polymers, 6(4), Kumr, R., & Mjet, N. V. (2). A review of chitin nd chitosn ppliction. Rective nd Functionl Polymers, 46(1), Lleg, M., & Pikulik Ivn, I. (1991). Wet-we strength increse y chitosn. Nordic Pulp nd Pper Reserch Journl, 6(3), Lleg, M., & Pikulik Ivn, I. (1992). Strengthening of mechnicl pulp wes y chitosn. Nordic Pulp nd Pper Reserch Journl, 7(4), Lleg, M., & Pikulik Ivn, I. (1993). Unconventionl strength dditives. Nordic Pulp nd Pper Reserch Journl, 8(1), Lertsutthiwong, P., Chndrkrchng, S., Nzhd, M. M., & Stevens, W. F. (22). Chitosn s dry strength gent for pper. Appit Journl, (3), Lertsutthiwong, P., Nzhd, M. M., Chndrkrchng, S., & Stevens, W. F. (24). Chitosn s surfce sizing gent for offset printing pper. Appit Journl, 7(4), Li, H., Du, Y., & Xu, Y. (24). Adsorption nd complextion chitosn wet-end dditives in ppermking systems. Journl of Applied Polymer Science, 91(4), Li, H., Du, Y., Xu, Y., Zhn, H., & Kennedy, J. F. (24). Interctions of ctionized chitosn with components in chemicl pulp suspension. Crohydrte Polymers, 8(2),

7 Y. Hmzeh et l. / Crohydrte Polymers 94 (213) Mlton, S., Kuys, K., Prker, I., & Vnderhoek, N. (1997). The influence of fier properties on the dsorption of ctionic strch y euclypt pulps. In Proceedings of the 1st Appit Annul Generl Conference Melourne, Austrli. Pelton, R. (24). On the design of polymers for incresed pper dry strength A review. Appit Journl, 7(3), Slminen, K., Ktj-ho, J., Lindqvist, H., Retulinen, E., Rntnen, T., & Sunderg, A. (211). The effects of certin polymers on tensile strength nd tension relxtion of wet we. In Proceedings of TAPPI PperCon Conference Cincinnti, OH, USA. Tejdo, A., Miro, A., & vn de Ven, G. M. T. (211). Effect of EDC ADH fire crosslinking on the wet-we strength of BHKP with nd without PCC loding. Journl of Science & Technology for Forest Products nd Processes, 1(1), Uesk, T., & Ferhi, M. (1999). Principl fctors controlling press room reks. In Proceedings of Pper Physics Conference Sn Diego, CA, USA. Zkrjšek, N. (28). Influence of pulp properties on the dsorption of ctionic strch. Tppi Journl, 7(11),