High-Performance Multifunctional rPA6/rCFRP/rGraphite Hybrid Composites from Recycled Industrial Waste

Environmental concerns and the global shift toward a more sustainable and circular economy have increased the demand for economically viable materials derived from industrial waste. In this study, high-value engineering materials discarded from different industries were repurposed to develop new multifunctional hybrid composites. The selected postindustrial waste included polyamide 6 (rPA6) from automotive plastic washers, recycled graphite (rGra), and recycled carbon fiber reinforced polymer (rCFRP) epoxy-based composites originating from the aerospace sector. These materials were separately ground using a knife mill and subsequently compounded via extrusion. The fillers (rGra and rCFRP) were incorporated individually and as hybrids (rCFRP:rGra, 1:1 wt %) at total loadings of 5, 10, and 20 wt % in the rPA6 matrix. The composites were characterized in terms of morphology, rheology, mechanical performance (tensile test), thermal behavior (differential scanning calorimetryDSC), electrical conductivity, and electromagnetic properties. The mechanical results revealed a notably high ultimate tensile strength of 126 MPa and an elastic modulus of 4.8 GPa for the rPA6/rCFRP (20 wt %) composition, suggesting strong interfacial adhesion promoted by secondary interactions between the epoxy resin coating on the rCFRP and the rPA6 matrix. Electrical conductivity measurements on composite films showed values from 10^-5 to 10^-1 S.cm^-1 for the hybrid and rCFRP-filled compositions, indicating their potential for antistatic (anti-ESD) applications. Although rGra exhibited lower mechanical and electrical performance than rCFRP at the evaluated contents, it was less detrimental to processability, making the hybrid formulations more balanced candidates for real-world applications. Overall, this study demonstrates a promising strategy for upcycling industrial waste into high-value, multifunctional composites, thereby contributing to resource efficiency and waste minimization across various industrial sectors.