Biodegradable Wastepaper-Based Foam with Ultrahigh Energy-Absorbing, Excellent Thermal Insulation, and Outstanding Cushioning Properties

A new biodegradable foam with low density (0.065–0.081 g/cm3), high porosity (>92%), low thermal conductivity (0.044 W/mK), excellent mechanical properties, and outstanding cushioning properties was prepared by a simple green method using wastepaper without any chemical pretreatment as the raw material. The porous structure and the reinforced cell skeleton formed by the wastepaper fibers coupled with PVA and gelatin, respectively ("bridge-linking" and "membrane-linking" structure), give the foam excellent coordination between thermal insulation and energy absorption properties, which are typically considered incompatible with each other in conventional cushioning foam materials. Furthermore, by impregnating a shear thickening fluid (STF) into wastepaper-based foam, a biodegradable cushioning packaging material with ultrahigh energy absorption for product delivery in extreme environments, such as parachute-free airdrops, was successfully prepared. The findings demonstrate that when the external impact velocity surpasses the critical shear rate of STF, the increased mass fraction and content of STF can enhance the energy absorption properties of the wastepaper-based foam, significantly enhancing its dynamic cushioning performance (STF can decrease the maximum impact acceleration by up to 85%).