Development of sustainable polymer composites using recycled polypropylene and organic fillers

Polypropylene [PP] is an extremely versatile material and can be used for a wide range of applications. PP is also one of the most popular plastic packaging materials in the world, and only around 1% is recycled, which means most PP is headed for the landfill. This decomposes slowly over 20-30 years. Recycling is the third component of the reduce, recycle, and reuse waste hierarchy and is an important part of modern waste reduction. In this study, recycled PP sourced from car battery casings were compounded with organic fillers such as coconut shell (CCS) powder, wood filler (WF) powder, rice husk (RH) powder, banana fibre BF (BAF) powder, and bamboo fibre (BF) powder, and hybrid combinations of wood filler with coconut shell powder, rice husk, banana fibre powder, and 5wt/wt% of PP-g-MA compatibilizer in a ratio of 75/20/5 were used to enhance the compatibility between the fillers and the PP matrix. The various ingredients were melt-mixed using a twin screw extruder and the test specimens were moulded using an automatic injection moulding machine. The main objective of this work was to study the changes in the mechanical properties of the prepared composites with respect to that of virgin polypropylene. Testing for physical and mechanical properties was carried out as per the ASTM standards. From the test results, it was inferred that banana- and bamboo-reinforced rPP had the highest tensile strength at yield and flexural strength. The hardness values of all composites were close to recycled PP. Among the hybrid composites, rPP/WPF/RH and rPP/WPF/BF show the highest resistance to abrasion. Finally, composites containing banana fibre, bamboo fibre, and rPP/WF/BF showed good mechanical properties, as did other combinations.