Enzymatic Modification Of Poplar APMP And CTMP Fiber

APMP and CTMP have the advantages of high yield, low pollution and low energy consumption, especially suitable for the current situation of China. Currently, the main problem of APMP and CTMP pulping is that the strength of the pulp is not high, which is attributed to the short fiber length and the weak strength of fiber itself. It is still difficult to improve the strength of pulp even by increasing the dosage of chemicals.In this study, the effects of cellulase and xylanase treatments on the tensile strength, tear strength and burst strength were studied. The reaction parameters were optimized. The treated pulp fibers were analyzed by X-ray photoelectron spectroscopy (XPS), environmental scanning electron microscope (ESEM), fiber quality analyzer (FQA), atomic force microscope (AFM) and X-ray diffractometer. The improvement mechanism of pulp strength was proposed.The results from enzymatic modification of APMP showed that cellulase or xylanase treatment could improve the strength of pulp in different degree. The optimal reaction conditions were the cellulase dosage of 0.12 ECU/g and the time of 90 min at 50℃. Compared the control sample, the tensile index, burst index and tear index of poplar APMP increased by 8.30%, 7.10%, 22.32% respectively. The optimal reaction conditions were the xylanase dosage of 0.6 AXU/g and the time of 90 min at 50℃. Compared to the control sample, the tensile index, burst index and tear index of poplar APMP increased by 11.05%, 12.90%, 23.37% respectively.The results from enzymatic modification of CTMP showed that cellulase or xylanase treatment could improve the strength of pulp in different degree. The optimal reaction conditions were the cellulase dosage of 0.2 ECU/g and the time of 60 min at 50℃. Compared the control sample, the tensile index, burst index and tear index of poplar CTMP increased by 12.9%, 12.1%, 11.7% respectively. The optimal reaction conditions were the xylanase dosage of 1.0 AXU/g and the time of 60 min at 50℃. The tensile index, burst index and tear index of poplar CTMP increased by 13.5%, 14.1%, 13.8% respectively compared to the control sample, t.The fiber properties, fiber morphology, surface morphology, chemical structure and crystallinity of the APMP and CTMP after cellulase or xylanase treatment were determined. The results showed that the carboxyl cantent and the water retention value of the treated fibers by cellulase or xylanase were significantly increased compared with that of the control samples. The oxygen carbon ratio of fiber surface increased and the surface lignin content decreased. The C2 component related to the cellulose hydroxyl increased. The fiber surface became rough as result of the rupture of cell wall and the fiber surface porosity increased after treatment. The coverage of granular lignins on the fiber surface decreased and the size reduced, which resulted in the appearance of more microfibers on fiber surface. The curl index of the treated fiber increased slightly. The fiber fines content and kink index significantly decreased. The fiber length and coarseness slightly increased. The crystallization index of the pulp increased slightly after cellulase or xylanase treatment. Thus, the decrease of fiber fines led to the increase of long-fibers proportion. The removement of resulted in the appearance of more fresh cellulose hydroxyl. The increase of the fiber flexibility contributed to the enhancement of interlacing. The above factors helped to improve the paper strength.