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

Khantayanuwong Somwang, Toshiharu Enomae, Akira Isogai, Fumihiko Onabe
2002 JAPAN TAPPI JOURNAL  
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 recyc ling treatment. The crystallinity of fibers in handsheets was moderately changed by the recycling treatment as observed by X -ray diffractometry. Because most of the fibers consisting of the stable crystalline region which was hardly affected by the recyc ling treatment, the change in
more » ... ange in crystallinity was 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 affected 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. FT-Raman spectroscopy was found not suitable for determining the effect of recycling treatment on changes in amounts of amorphous and crystalline regions of fibers. -1 represent to changes in amounts of amorphous and crystalline regions, respectively, 7) therefore, the FT-Raman spectroscopy was found not suitable for determining the change in the ratio of amorphous and crystalline regions in the fibers affected by the recycling treatment. This is possibly caused by the fact that the ratio was not statistically different between R0-and R4-fibers, as shown in Figs. 2 and 4 , and not caused by changes in chemical aspects of fibers due to the recycling treatment. Moreover, a possible cause for the similarity of the two FT-Raman spectra is that the sample preparation and treatments in the present study were different from those in others' research. Conclusion The crystallinity index of fibers in the handsheets was moderately changed by the recycling treatment. This phenomenon is suggestively caused by some part of amorphous region of fibers in the Khantayanuwong, S., Enomae, T. and Onabe F., "Changes in crystallinity and re-swelling capability of pulp fibers by recycling treatment", Japan Tappi J., 56 (6): 103-106(2002) handsheets was slightly changed to be higher crystallinity during recycling. Because of the lack of re-opening of recycled fiber lumens in the 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 recycled fibers was consistent with the loss in the amount of bound water adsorbed to their cell wall, which was possibly caused by the loss in amorphous region, as is known as sub-morphological changes of fiber wall. Only the DSC and the measurement of the aspect ratio of wet single fibers could sensitively determine the changes in physical features of fibers affected by the recycling treatment. The FT-Raman spectroscopy was found not suitable for determining the effect of recycling treatment on the changes in amounts of amorphous and crystalline regions of fibers.
doi:10.2524/jtappij.56.863 fatcat:2q43uutzejfa5p3d73al7xbhdq