From Waste to High-Performance Materials: Advancing the Circular Economy with Short Glass Fiber-Reinforced Recycled Heterophasic Ethylene−Polypropylene Copolymer Composites

Abstract Heterophasic ethylene−propylene copolymer (HEPC) is a type of polypropylene-based material consisting of a semi-crystalline polypropylene (PP) matrix and dispersed elastomeric phase formed through copolymerization with ethylene. This biphasic structure combines the rigidity and chemical resistance of PP with the flexibility and impact toughness imparted by the elastomeric phase. The increasing use and disposal of HEPC raise environmental concerns since its heterogeneous structure complicates recycling compared with conventional PP. Efficient recycling routes are essential for sustainable polymer management. This study investigated the effects of reprocessing and short glass fiber (SGF) incorporation on HEPC-based composites. Virgin (HEPC-V) and recycled (HEPC-R) HEPC, as well as composites containing 10, 20, and 30 wt % SGF, were characterized regarding crystalline structure and thermal, rheological, morphological, and mechanical behavior. Reprocessing preserved the crystalline structure of HEPC, with only minor reductions in melting, crystallization temperatures, and crystallinity. SGF addition increased viscosity, elastic modulus, and Shore D hardness, indicating that the fibers significantly enhanced the stiffness and strength of the composites. Overall, the results demonstrate that HEPC-R retains performance comparable to HEPC-V and that SGF incorporation is an efficient strategy to recover or improve mechanical properties, making the HEPC-R/SGF composite a viable and sustainable alternative for industrial applications.