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.