Preparation of biodegradable composite films based on carboxymethylated holocellulose from wheat straw

Holocellulose was extracted from wheat straw and catalytically transformed into carboxymethylated holocellulose (CMHCS) to prepare a biodegradable composite film. By changing the type and amount of catalyst, the carboxymethylation of the holocellulose was optimized with respect to the degree of substitution (DS). A high DS of 2.46 was achieved in the presence of a cocatalyst composed of polyethylene glycol and cetyltrimethylammonium bromide. The effect of DS on the properties of CMHCS-derived biodegradable composite films was further investigated. Compared to pristine holocellulose, the mechanical properties of the composite film were significantly improved and increased with increasing DS. The tensile strength , elongation at break, and Young's modulus increased from 6.58 MPa, 51.4 %, and 26.13 MPa for the unmodified holocellulose-based composite film to 14.81 MPa, 89.36 %, and 81.73 MPa for the film derived from the CMHCS with a DS of 2.46. The biodegradability of the composite film was assessed under soil burial biodisintegration conditions and reached 71.5 % degradation after 45 d. Additionally, a possible degradation process for the composite film was proposed. The results indicated that the CMHCS-derived composite film has good comprehensive performance, and CMHCS is expected to be applied in the field of biodegradable composite materials.