Ultra-high-strength composite films prepared from NMMO solutions of bamboo-derived dissolving pulp and chitosan

Regenerated cellulose (RC) films have numerous separation and purification applications. However, the mechanical properties of RC films are poor. Because of their very similar chemical structures and excellent compatibility, chitosan (CS) particles were chosen to reinforce bamboo-derived dissolving pulp (BP)-based films. BP/CS blend solutions were obtained by mixing BP and CS particles at different weight percentages into N-methyl-morpholine-N-oxide (NMMO) solvent. The BP/CS composite films prepared by the traditional phase transformation method formed a physically cross-linked network with high packing density for the water evaporation after air-drying. Due to the strong hydrogen bonding between CS and BP revealed by rheological properties and Fourier transform infrared (FTIR) data, the CS particles dispersed uniformly in the matrix, and the compatibility of the reinforcement with the matrix was excellent, which was further confirmed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and UV–vis transmittance data. As the weight percentage of CS increased from 9.09 wt% to 14.24 wt%, the crystallinity of cellulose II increased from 32.20%–38.59%, and the tensile strength of the BP/CS composite films increased from 662.20 MPa to 865.53 MPa, respectively. These results indicate that the tensile strength of the BP/CS composite films was increased by nearly 250.83 %–358.56 % compared with that of the regenerated BP film (188.75 MPa). Moreover, the elongation at break was increased by 51.16 %-41.63 %. These findings provide a new way to prepare ultra-high-strength RC composite films.