Material Properties of Recycled Polypropylene/Polyethylene Terephthalate for Rooftop Applications

Plastic waste management remains a major challenge, particularly for multi-material plastics such as polypropylene/polyethylene terephthalate (PP/PET) composites commonly used in packaging. This study applies a circular economy approach by recycling a PP/PET blend (95% PP, 5% PET) with maleic anhydride compatibilizer contents of 3%, 7%, 10%, and 13%. Recycled samples were produced via extrusion, granulation, and injection molding, then evaluated for density, tensile properties (7 mm and 2 mm thicknesses), hardness (Shore D), and Izod impact strength. The results were compared with two commercial PVC roofing products. The 13% compatibilizer sample showed the highest density and impact resistance, while the 3% sample exhibited the best tensile strength at 7 mm thickness and the highest hardness. Overall, increasing compatibilizer content did not lead to significant property improvements. The 3% compatibilizer formulation was identified as the most effective for rooftop applications, offering competitive performance with minimal additive use. Compared to PVC roofing, recycled PP/PET achieved comparable density, tensile strength, and impact resistance, although PVC remained stiffer.