All-Biomass-Derived Cellulose Phosphate-Based Heat-Sealable Films and Thermally Stable Antifizzing Cups with Improved Recyclability

Agricultural biomass such as rice straws represents a significant volume of waste generated worldwide; disposal of which through landfilling and burning is a major global challenge. In the present study, strategic functionalization of rice straws through delignification-cum-phosphorylation using low-cost agrochemicals followed by scalable processing into films and beverage cups is developed. The phosphorylated films with high charge content (1488–2199 mmol kg–1) show improved mechanical strength under both dry and wet conditions with high thermal stability and flame retardancy. A detailed mechanistic study using FTIR and XPS spectroscopy confirmed the covalently bonded phosphate groups on the cellulose backbone along with the formation of silicon phosphate cross-linkages upon heating. Interestingly, the all-cellulose films could be heat-sealed, improving the shelf life of highly perishable stored fruits and vegetables. Molded cups demonstrate high solvothermal stability with antifizzing and improved washability (for 3 times) post consumption. The proposed valorization of rice straws into packaging films and beverage cups with lower ecological impacts and commercial feasibility provides a sustainable alternative for a plastic-free world.