A robust, stable, and scalable multifunctional composite foam utilizing full components of lignin and cellulose from lychee pruning waste.

Foam materials hold great promise in construction and packaging applications. However, the non-biodegradability and poor thermal stability of petroleum-based foams present serious environmental and safety concerns. It is crucial to develop sustainable, eco-friendly foam fabrication methods that balance environmental responsibility with high performance. In this study, a novel high-strength, heat-resistant, and water-stable composite foam (FPLs) made from Lignin-based waterborne polyurethanes (LWPUs) and Cellulose fibers, derived from full-component utilization of lychee pruning waste, is introduced. A eco-friendly and simple method utilizing LWPUs crosslinking to fabricate composite foams has been developed, bypassing the need for special drying and ensuring scalability. The FPLs exhibits a high compressive modulus of 455.8 kPa and a yield strength of 191.2 kPa due to the interaction between the LWPUs adhesive and the cellulose fibers. In addition, it demonstrates natural water resistance (maximum contact angle of 122°), exceptional photothermal conversion performance (reaching a peak temperature of 199.7 °C under infrared laser irradiation), superior thermal stability (no deformation up to 250 °C), and insulation performance (thermal conductivity of 0.038 W/mK), while maintaining excellent degradability and recyclability. These materials hold promise as sustainable alternatives to conventional plastic-based foams, providing a viable solution to mitigate the pervasive issue of "white pollution."