Sustainable valorization of waste polystyrene and PVC blends for high-performance applications

Disposal of solid plastic waste is one of the major challenges facing most countries, especially developing countries. In this study, waste polystyrene foam (WPS) and polyethylene terephthalate (PET) from waste plastic bottles were recycled. The waste PET was chemically recycled using a glycolysis technique to obtain the glycolyzed product (GPET) and subsequently unsaturated polyester. WPS was also mechanically recycled using a hot blending technique. Polyvinyl chloride, GPET, and the prepared polyester were added as multifunctional additives and their effects were compared with conventional additives such as dioctyl phthalate (DOP). The effect of these additives on the rheological, mechanical, and electrical properties was studied. Thermal stability, fire retardancy and morphology of the WPS/PVC blends were also evaluated. Results showed that polyester significantly improved melt flow rate (up to 0.975 g/10 min), flame retardancy (burning rate reduced to ~ 0.5 mm/s), and decreased combustion energy (~ 404 cal). GPET enhanced tensile strength (21.96 MPa) and elongation at break (37%). Additives increased permittivity and conductivity, while polyester exhibited the strongest dielectric response due to enhanced interfacial polarization. SEM analysis confirmed better dispersion and compatibility in GPET and polyester blends. Based on the results, the developed blend shows strong potential for use in applications requiring enhanced mechanical, thermal stability, and flame retardancy as electrical insulation, construction materials, and automotive components.