Changes in Crystallinity and Re-swelling Capability of Pulp Fibers by Recycling Treatment

Abstract

An integrated technique was purposed for clarifying changes in amounts of amorphous and crystalline regions of fibers as well as for estimating possibility of their irreversible conversion due to recycling treatment. The crystallinity of fibers in handsheets was moderately changed by the recycling treatment as observed by X-ray diffractometry. Because major part of fibers consisting of the stable crystalline region which was hardly affected by the recycling treatment, the change in crystallinity possibly stemmed from a slight increase in crystallinity of amorphous region of fibers during recycling. The decrease in the amount of the amorphous region by the recycling treatment, which affects the water adsorbability of fibers, was indirectly detected by differential scanning calorimetry. Because of the lack of re-opening of recycled fiber lumens in a wet state, the amount of bound water adsorbed to fiber wall substantially influenced the re-swelling capability of recycled fibers. The loss in re-swelling capability of wet recycled fibers was consistent with sub-morphological changes of fiber wall possibly due to the decrease in the amount of the amorphous region. In this study, FT-Raman spectroscopy could not detect the effect of recycling treatment on changes in amounts of amorphous and crystalline regions of fibers.