Recrystallization behavior of cellulose III from hydrothermal treatment: the dynamic variations of polymorphs and crystallinities

Abstract

The application of cellulose fibers with varieties of allomorphs is of much interest. However, the crystal structural changes of certain allomorphs during the wet chemistry process are often ignored. In this work, the recrystallization behavior of softwood pulp cellulose IIII back to cellulose Iβ with tg conformation by hydrothermal treatment at different temperatures is carefully evaluated and calculated. The treatment contributed to the distortion of crystallites and lower crystallinity including the formation of intermediate amorphous phase at 60 °C. Higher hydrothermal temperature (100 °C) resulted in the reversion to cellulose I (59.7%) as well as retention of 12.5% of cellulose III, suggesting the uncompleted recrystallization during the process. With the loosened fibril structure and more amorphous regions, the thermal stability of recrystallized cellulose I is significantly dropped, far below that of original cellulose I/III materials. This study may provide new thoughts on the industrial processing and application of the polymorphic cellulose materials.