Rheological properties of partially dissolved cellulose composites: the effect of cellulose content and temperature

Dissolution of cellulose is a promising approach to control the rheology and processability of cellulose. However, dissolution of cellulose is extremely difficult because of the strong hydrogen bonding network, the hydrophobic interactions, and high crystallinity. In this study, partially dissolved cellulose composites (denoted as PDCC) with high cellulose content are prepared by inserting 1-butyl-3-methylimidazolium chloride (BmimCl) into cellulose fibrils through the repeated rolling method, and rheological properties of obtained PDCC with different cellulose content are fully characterized on the high-pressure capillary rheometer under different temperature. The viscosity of PDCC is 4 orders of magnitude higher than that of cellulose solutions prepared by full dissolution, and PDCC has obvious shear thinning behavior, similar to that of polymer melt (e.g., low-density polyethylene, denoted as LDPE). The rheological properties of PDCC are attributed to its peculiar morphological structure where non-dissolved cellulose in the core areas is glued by dissolved cellulose in the surface areas, according to scanning electronic microscope images and X-ray diffraction. The viscosities of PDCC could be significantly decreased by lowering cellulose content and increasing temperature. Moreover, the correlation coefficients analysis of processing parameters and flow behavior of PDCC, indicates that the cellulose content dominates the flow behavior of PDCC. Using the hot press as a model manufacturing method, PDCC was fabricated as boards with dimensions of 50 × 50 × 2 mm. This work paves a potential avenue for processing cellulose with high content.