Optimized recycling of e-waste and tire rubber into sustainable polyurethane composites with enhanced compressive performance

Research on reusing industrial and electronic waste in functional composite systems has been spurred by the growing need for sustainable engineering materials. This study used methylene diphenyl diisocyanate (MDI) as a binder to reinforce three recycled fillers: waste rigid polyurethane foam (WRPU), rubber tire waste (RTW), and waste printed circuit boards (WPCB). Response Surface Methodology (RSM) optimization revealed that the optimal composition was 6 wt% WRPU, 3 wt% RTW, and 7.58 wt% WPCB. With a maximum compressive strength of 38.987 MPa, this optimized formulation showed significant improvement over the unreinforced matrix (14.128 MPa). The mechanical performance was highly precisely validated by numerical simulation using ANSYS Workbench, with a deviation from the experimental results of only 0.75%. FTIR and thermogravimetric analysis (TGA) indicated enhanced interfacial interactions, improved compatibility and thermal stability up to 550 °C, while high-resolution scanning electron microscopy (HR-SEM) verified uniform filler distribution. By enhancing interfacial bonding and stress transfer efficiency, the synergistic interaction of WRPU, RTW, and WPCB clarified the structure–property relationship controlling composite performance. These results support a sustainable circular economy by showcasing the potential of recycled polyurethane composites for lightweight, compressive load-bearing applications in automotive non-structural components.