Study On Change Of Aggregation State Of Cellulose As A Mechanism And Its Suppression Methods Of Secondary Plant Fibers

With the demand of protecting forest resources and developing low-carbon economy, therecycle of secondary fiber has caused the attentions all over the world. Compared with theoriginal fiber, decay phenomenon has happened to the secondary fiber. Co-crystallization as amechanism for quality decay of secondary fibers studied in formal research has made someprogress. Researchers think that the aggregation of elementary fibril leads toCo-crystallization, which effect physical properties of secondary fiber. But there is still not asatisfactory explanation about the original cause of aggregation of elementary fibril. In thisresearch, the formation and relative content of irreversible hydrogen bond were studied inorder to investigate the change of aggregation state structure, which effected elementary fibrilstructure that caused the hornification of secondary fiber. In the meaning time, the resolutionof hornification was discussed, from which mechanisms and reasons of it were observed.The results showed that the physical properties of secondary fiber decreased during therecycling process. Crystallinity calculated by FTIR, XRD, NMR increased with the increaseof recycling times. And the change trend of crystallinity was the same as the hornificationdegree. Relative content of Intermolecular hydrogen bond O(6)H…..O(3′) increased with theincrease of recycling times which lead average fibril aggregate size (17.9-22.2nm) toincrease.With the rise of the drying temperature and the increase of squeezing the time, thecontent of Intermolecular hydrogen bond O(6)H…..O(3′), microcrystalline size and tensilestrength of paper increase first and then reduce, which shows the same change rule.Tensile strength reached the maximum at the drying temperature of100℃and insqueezing time of15min. The results suggested that the change of relative content hydrogenbond lead to the increase of the cross sectional area of microcrystallinity, which resulted inthe aggregation of elementary fibril.It may be an explanation of mechanism for secondaryfibers.Based on the studies above, the resolution of hornification was discussed further. Theresults show that: the swelling ability of the pulp increased after carboxymethylation, Butwater retention value and carboxyl content didn’t increased with growing substitution degree of carboxymethylation. After washing, the strength performance improved obviouslycompared to the virgin pulp, which was because of the ionization state of carboxyl group.Tensile index, break index,and tearing index of low substitution degree sheets increased by28.82%，124.07%，55.03%, respectively, showing that the processing of carboxymethylationcan effectively relieve fiber hornificationThe best experimental conditions for biological treatment method: laccase dosage20U/g,the processing time1.5h, room temperature, pH7, pulp consistency3%，Oxygen atmosphere.The biological treatment method of laccase/histidine can effectively improve the dry and wettensile strength of eucalyptus pulp, especially improving the wet tensile strength significantly.Carboxyl content of eucalyptus pulp after laccase/histidine treatment increased21%, whichincreases fiber swelling ability and results in the increase of paper strength performance.