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Internal Fibrillation in Never-dried and Once-dried Chemical Pulps

2002; Volume: 56; Issue: 6 Linguagem: Inglês

1038-6807

Xinshu Wang, Thaddeus Maloney, Hannu Paulapuro,

Lignin and Wood Chemistry

This study investigates the internal fibrillation of chemical pulps, with a focus on how the pores in once dried chemical pulps are reopened in beating. A novel thermoporosimetry technique was used to measure the change in pore size distribution (PSD) and pore volume during drying and beating. This technique is based on the melting temperature depression of cyclohexane in a porous structure. The cyclohexane was introduced into the fiber cell wall thorough a solvent exchange procedure. Solute exclusion was used to measure the fiber saturation point (FSP). It was shown that the thermoporosimetry technique is able to detect the change in PSD and pore volume during drying and beating. The pore volume measured using thermoporosimetry correlates with the FSP, and it reflects the fiber swelling, though it is lower than the FSP due to the contraction of fibers in cyclohexane. It was also seen that even though the pore volume of previously dried pulps can be recovered by beating (i.e., the pulp can be reswollen), some pores are closed which are not reopened by normal levels of beating. In other words, beating does not completely reverse hornification.