Effects Of Pulping Process On The Hormification Of Fibers

This paper studied the influence of pulping process on hornification of fibers. Using the four different pulping processes, which are kraft, soda, bisulphite and alkaline sulphite, to produce pulps with a wide range of yield (50-85%) and recycle the virgin pulps once to evaluate the influence of pulping conditions on fiber properties. We also studied the influence of extraction by dichloromethane on the surface chemical property of four chemical pulps and correlated the chemical changes with the mechanical characteristics of handsheet and the influence of freezing on water retention value, fiber characteristics and pulp property. The results indicate that the drying-rewetting cycle caused changes in the chemical and physical characteristics of fibers many of which were process dependent. Albeit, most of the fiber properties were related to pulp yield or lignin content but the degrees of fiber hornification were also process related. The extraction by organic solvent increased the O/C atomic ratio of fiber surface, however, it decreased the carboxylate content, tensile index, burst index, folding endurance, tensile energy absorption and density of hansheets, it also decreased the water retention value of pulp. This indicates that extraction by organic solvent caused fiber hornification. The result also indicates that recycled extracted fiber caused fiber more horrification. The water retention value of kraft, bisulphite and soda pulp decreased and the fireeness increased after freezing treatment. For the fully bleached commercial kraft pulps of hardwood and softwood (dry laps), Freezing treatment decreased density, tensile index, burst index, and folding endurance of handsheet, but increased the light scattering coefficient. The length of fiber is no changed, mean curl and mean kink of fiber have some increased, this result indicate that freezing caused fiber hornification which causes the loss of mechanical strength of handsheet. This is the first time to systematically research the influence of pulping process on O/C atomic ratio. The results indicate that O/C atomic ratio is associated with the pulping conditions, pulp yield and correlates well with the carboxylate content of fiber, beating and recycling. This is the first time to systematically research the influence of extraction by organicsolvent on the surface chemical properties (carboxylate content of fiber and O/C atomic ratio) of three kind of chemical pulps (kraft, bisulphate and soda pulp). We found that extraction by organic solvent caused fiber homification which lead to the loss of pulp properties and water retention value and correlates the chemical changes with the mechanical characteristics of handsheet. This is the first time to systematically research the influence of freezing on fiber hornifiation and present the mechanism of fiber hornification caused by freezing.