Non thermoplastic 3D molding based on coordination crosslinking for on-demand customization carboxymethyl chitosan-based packaging bags

The exhaustion of non-renewable resource and the environment pollution of plastic wastes have become a global crisis. Natural polysaccharide is expected to be sustainable and biodegradable alternative to petroleum-based plastics. However, the thermal processing of polysaccharides especially 3D film formation is challenging due to their lack of thermoplasticity. Herein, a novel reverse mold crosslinking film-forming strategy for the preparation of polysaccharide-based 3D film was proposed, where the role of rapid crosslinking molding is similar to that of cooling molding during injecting processing. Through this non-thermal processing, carboxymethyl chitosan/polyvinyl alcohol/Zn (CMCS/PVA/Zn) 3D films were successfully prepared. The CMCS/PVA/Zn exhibits excellent mechanical performance, water resistance, and transparency, meeting the performance requirement in food packaging bags. Moreover, CMCS/PVA/Zn can be customized on-demand, such as shape, size, color, and function, by adjusting the mold or adding functional additive. Notable, multiple carboxyl polysaccharides and metal ions can be used for the preparation of 3D films by this non-thermal processing method, showing great universality. And this method is more energy-efficient than thermal processing and preservers the bioactivity of polysaccharides and additives. Therefore, this innovative approach to polysaccharide processing offers a promising potential for the creation of polysaccharide-based food packaging bags as a sustainable alternative to non-degradable plastic bags.