Biodegradable foam from wastepaper with enhanced hydrophobicity for thermal insulation applications

This study presents the development of a novel bio-based foam utilizing wastepaper pulp as the primary raw material in response to the growing demand for sustainable and biodegradable alternatives to synthetic foams. Foams have shown great potential for multifunctional applications like packaging, insulation, and agricultural purposes. In this work, a simple oven-drying approach was developed to prepare biodegradable foams from waste newspaper (WNP), poly (vinyl alcohol) (PVA), and varying concentrations of chitosan. The resulting foam exhibited promising characteristics like high porosity (>94.71 %) and low density (0.032 g/cm³ to 0.129 g/cm³). The foam exhibited a water absorption capacity ranging from 0.2 to 0.6 g/g, with a maximum water contact angle of 114°, signifying an exceptionally hydrophobic surface and enhanced water resistance. The porous structure and interfacial contact regions contributed to the formation of a robust matrix with a smooth surface, resulting in exceptional thermal insulation (thermal conductivity of 0.04–0.06 W/(m·K)), higher biodegradability, and better mechanical properties (compressive strength in the range of 87 kPa to 154 kPa at 60 % strain). The incorporation of waste-derived cellulose not only repurposes paper waste but also contributes to a circular bioeconomy. The increase in chitosan content improved the water resistance and mechanical strength. Moreover, this biofoam has been demonstrated to be recyclable with a substantially reduced environmental impact.