INVISTA EM CONHECIMENTO - Revista O Papel

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Technical Article / Peer-reviewed ArticleO PAPEL vol. 73, num. 6, pp. 57 - 65 JUN 2012RESULTS AND DISCUSSIONin figure 3, it is observed that fibers mixtures with oCCpresent the highest results of sheet density and, consequently,the lowest in bulk. the mixtures with more newsprint fiberscontent, richer in mechanical pulp, present the lowest densityresults (and highest bulk), as is shown in figure 4. results ofGroup 1 and 2, as seen in figures 3 and 4, show that kraft pulprefining increases significantly the apparent paper density.when the oCC fibers are refined, the increasing in density (orthe decreasing in bulk) is not significant.for the paper mechanical properties, such as tensile index,burst and tear index, see figures 5 - 7. as expected for thereinforcement fibers, more kraft pulp fibers impact positively.also, more kraft pulp refining results in better paper mechanicalproperties. the refining of the oCC fibers does not impacts onmechanical properties, or decrease them in some cases suchas in Group 2 of figure 5. obviously, the low quality of thenewsprint secondary fibers is cause for the poor paper quality.it may be observed that the results for elasticity module do notshow significant difference among different fibers (see Group 1in figure 8), and that oCC fibers do not contribute to increasethis property. interesting to observe that do not occur a positivesynergistic effect on elasticity module property, it has even beennegative in mixtures with higher content of newsprint fibers(mechanical pulp).several authors present estimation for the tear index, asillustrated in Table 6. here, it is applied an equation similarto suttiGer (1979), but using tear index and tensile index, asshown in Figure 15.figure 15 shows again that more kraft pulp produces betterresistance, but even oCC fibers reduce this potential. newsprintfiber gives the poorest paper quality in resistance potential inboth figure 15 and figure 9. the energy absorption, such asstiffness index, tensile energy and work are presented in figures10-12. stiffness for mixture was worst when increasing kraftpulp and oCC fiber content in figure 10. in general, propertiesincrease when kraft pulp is applied as reinforcement fiber, asshown in figures 11-12.as expected, pore volume and air permeance show highervalues when the paper presents higher content of newsprintfiber. refining of kraft pulp and oCC fibers decreases thesevalues. results show that the synergy between kraft pulp andoCC fibers is better than other mixtures, including newsprintsecondary fibers.Table 6. Estimation of the potential for resistance.AuthorsSeehofer and coll. (1983)Weidhaas (1979)Suttiger (1979)[(CAR*, N) * (RR, mJ/m)]/1000(RT, N) + 0,1* (RR, mJ/m)10*(RT) + 0,1* (RR)where: CAR: breaking length; RR: tear resistance; RT: tensile resistance.PR(Group 1) = 270,118*Pinus+185,341*OCC+200,426*Newsprint-39,935*Pinus*OCC-177,119*Pinus*Newsprint-75,043*OCC*Newsprint (R 2 = 92,4)PR(Group 2) = 345,471*Pinus+232,09*OCC+193,399*Newsprint-492,833*Pinus*OCC-11,535*Pinus*Newsprint-13,338*OCC*Newsprint (R 2 = 83,2)Figure 15. Estimated responce-surface for resistance potential64 Revista O Papel - junho/June 2012resistance potential, PR = 10*(tensile index, kNm/kg)+0,1*(tear index, mN.m 2 /g)
Technical Article / Peer-reviewed ArticleO PAPEL vol. 73, num. 6, pp. 57 - 65 JUN 2012Y4 = Tear index, mN.m 2 /gY5 = Burst index, kPa.m 2 /gABY7 = Elongation, %Y6 = Work, J/100Y8 = Air permeance (300 mL), dm 3 /kgY1 = Density, 10 -3 kg/m 3Apparent spec. volume, dm 3 /kgY3 = Tensile index, N.m/gCDFigure 16. Impact of refining degree on OCC fiber propertiesFigure 16 shows the refining degree impact on oCC fibersproperties. more refining implies loss of bulk, increased elongationindex and increased mechanical properties. also, more refining iscause of loss in air permeance.CONCLUSIONthe potential of gains in mechanical properties of paper frommixture of fibers when the individual fibers are separately refinedis presented in this paper. the loss in properties due to newsprintfibers is clearly compensated by the inclusion of reinforcementkraft pulps fibers.this work presents a clear direction for industrial applicationwhen the feedstock includes significant amounts of oCC fibersand newsprint fibers, exposing how this condition impactsnegatively in mechanical properties and positively in bulk. thisstudy also presents how the amounts of reinforcement fibersand the refining levels can compensate these impacts. as hereclearly shown, it is not worthy to refine the fibers after themixture, because it negatively impacts on the newsprint fibersand is not significant for the oCC fibers. the main conclusion,therefore, is that kraft pulp refining prior to the mixture results ina more economical procedure.•REFERENCES1. BARROS NETO, B. DE; SCARMINIO, I. S.; BRUNS, R.E. - Planejamento e otimização de experimentos. Campinas: Editora UNICAMP, 1995.2. LEVLIN, J. - Characterization of Papermaking Pulps. Tappi, v. 58, n0 1, January, 1975. p.71 – 74.3. LUMIANEN, J. - Fibras recicladas precisam de refinação? O Papel LV ( 2): 36-39 (1994).4. SEEHOFER, J. CORNELL, H. STRITTMATTER, G. WEIDHAAS. A.G. - An forderung an die Holzstoffe. V. 37 (10A) : V-110 – 114 (1983).5. WEIDHAAS. A.G. - Umrustung einer RMP- auf eine TMP – Anlage; Wochenblat fur Papierfabrication 107 (23/24) : 923 – 932 (1979).6. SUTTIGER, R. - Die Technologie des Hozschleifprozesses . Voith Forschung und Konstruktion, Heft 26, dec. 1979. 78 pag. Alemanha. P. 23.junho/June 2012 - Revista O Papel65
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