Flexible polyurethane foam: materials, synthesis, recycling, and applications in energy harvesting – a review

Abstract

The increasing demand for sustainable and clean energy, driven by the finite supply of fossil fuels, has motivated researchers to explore alternative energy sources. Triboelectric nanogenerators (TENGs) are innovative devices that convert mechanical energy into electrical energy without the use of an external power source. The efficiency of TENG devices relies heavily on the materials employed. Polymeric materials with porous structures have proved particularly effective for TENG applications. Among these, polyurethanes (PUs) stand out as a versatile class of materials with significant potential across various applications, owing to their unique structure–property relationships. Flexible polyurethanes (FPUs) exhibit high elasticity, a three-dimensional pore network, and diverse densities that make them a promising material for energy harvesting applications. This review explores the materials, chemistry, recycling, and limitations of FPUs with a focus on their application in TENG devices. Furthermore, it compares the efficiency of FPUs in TENG devices with compact and other porous materials. The review concludes that FPU is a promising material for TENG devices across a wide range of applications, outperforming compact materials. This is mainly due to several advantages, such as high porosity, high elasticity, lightweight nature, versatility, durability, and cost-effectiveness. In addition, this review presents the future scope for the use of FPU in TENG applications.