Compression Molded Thermoplastic Composites Entirely Made of Recycled Materials

Recycled post-consumer high-density polyethylene pipe plastic was agglomerated into composite samples with wood, glass fiber, mineral wool, gypsum, and soapstone as recycled particulate fillers. The tensile strength, tensile modulus, impact strength, and hardness were the mechanical properties evaluated. Scanning electron microscopy was performed on the broken surfaces of tensile strength samples to study the interfacial interactions between the composite matrix and the filler materials. Heat build-up, water absorption, and thickness swelling were the physical properties measured from the composites. The addition of particulate fillers demonstrated the weakening of the tensile and impact strength but significantly improved the rigidity of the post-consumer plastic. The composites filled with minerals had mechanical properties comparable to compression molded wood plastic composites but higher resistance to moisture. A lack of hot-melt mixing affected the mechanical properties adversely.