Structural Change of Regenerated Cellulose Fibers Caused by Water

Structural change of regenerated cellulose fibers caused by water was investigated with the small angle X-ray, the specific volume and thermally stimulated depolarized current (TSDC) analyses. From the small angle X-ray measurement of Cupro fiber with various water regain, the sudden change of long period for lateral direction was detected at 40% of water regain at 25°C. And the Tg determined by dilatometry at the same water regain was 25°C. The peak intensity of TSDC γ1 relaxation decreased with increase in water regain when the water regain was under 4_??_5%. TSDC β1 relaxation decreased while TSDC β2 increased with increase in water regain when the water regain was above 4_??_5%. From these findings, it was concluded that the structural formation followed by the local molecular movement may be occurred in hydrophobic domain assigned by TSDC γ1 relaxation at the water regain under 4_??_5%, and then the local molecular rearrangement from TSDC β1 region to TSDC β2 region was also occurred at the water regain above 4_??_5%, and finally the micro-Brownian motion of cellulose main chain assigned by tan δα2 relaxation was released at 30_??_40% of water regain at room temperature which brings the sudden change in long periodicity and the macroscopical swelling of the regenerated cellulose fibers.