Study of the acoustic and thermal performance of composites made from recycled polyurethane foam with polypropylene fibers and micro-particles

As urbanization and building densities increase, the need for effective sound and thermal insulation in building design becomes increasingly important. This study investigates the impact of polypropylene fibers and microparticles on the sound and thermal insulation properties of recycled polyurethane foam. Microparticles with mesh sizes of 500, 750, and 1000 microns, along with polypropylene fibers under 1000 microns, were added to the recycled foam. Results indicate that thermal conductivity ranged from 0.07 to 0.15 W/(m²·K). The lowest thermal conductivity value (0.07 W/(m²·K)) was obtained in the sample containing recycled polyurethane foam with 5% by weight of polypropylene fibers, which provided the best thermal performance. Also, the Noise Reduction Coefficient (NRC)—as a standardized index for acoustic performance—was obtained in the range of 0.15–0.7. The highest NRC value was achieved by pure polypropylene fibers (0.70), followed by the sample containing recycled polyurethane foam reinforced with 3 wt% polypropylene microparticles sized 750–1000 µm (0.55). The results revealed that increasing the particle size generally improved NRC values, and increasing the polypropylene content up to 3 wt% enhanced the acoustic absorption performance, with further addition leading to diminishing returns. The addition of microparticles significantly improved sound absorption, with optimal particle sizes of 750–1000 microns yielding the best acoustic results, while the reinforced polypropylene fibers demonstrated the most effective thermal performance. Overall, these materials can provide effective solutions for enhancing building quality against sound and heat.