Effect of regeneration solvent on the characteristics of regenerated cellulose from lithium bromide trihydrate molten salt

Abstract

Dissolution and regeneration of cellulose is of vital importance for its end use. In the present work, the effect of different regeneration solvents (i.e. water, ethanol, and N, N-dimethylacetamide (DMAc)) on the characteristics of the regenerated cellulose from lithium bromide trihydrate (LBTH) molten salt was comprehensively investigated. It was found that the regenerated celluloses displayed obvious changes in macro- and micro-morphologies compared with the original microcrystalline cellulose (MCC). Furthermore, after the dissolution and regeneration process, the crystalline structure of cellulose was changed from cellulose I to cellulose II or amorphous structure, and the crystallinity of cellulose clearly decreased due to the deconstruction and rearrangement of cellulose chains. Moreover, the regenerated cellulose with ethanol had a relatively higher degree of crystallinity (70.2%) than that with water (42.3%) and DMAc (33.2%). Both X-ray Diffraction (XRD) and Attenuated Total Reflection Flourier transformed Infrared Spectroscopy (ATR-FTIR) analysis results indicated that ethanol as a regeneration solvent could be more beneficial to rearrange cellulose molecular chains and rebuild a more ordered structure compared to water and DMAc. In addition, thermogravimetric analysis showed that regenerated cellulose from LBTH exhibited a lower decomposition onset temperature and a higher char yield (over 17.8%) compared with the raw MCC (2.8%). The obtained results verified that regeneration solvents could substantially affect the reconstitution of cellulose molecule chains during regeneration as well as the multiscale structures and properties of the regenerated cellulose.