Durability of Repetitive Polypropylene Recycling: Challenge on Securing The Mechanical Properties

Most of the products used in our daily lives involve plastic. However, plastic pollution can cause an incalculable environmental crisis. Hence, an extensive effort has been made towards recycling plastic since the last decade. The challenge on plastic recycling is to secure the mechanical performance of the products. In this study, the durability of repetitive polypropylene processing from ten to fourteen cycles is investigated. Optimum parameters such as moulding temperature, injection pressure, holding pressure, holding speed, holding time, and cooling time were used to successfully manufacture extensive recycled polypropylene by injection molding process. The tensile and bending strength of polypropylene were managed to maintain above 30 MPa even at fourteenth cycles. The bending modulus was secured at least 1.0 GPa for the polypropylene after recycled for fourteen times. Besides, the recycled polypropylene could sustain more loading in bending mode rather than longitudinal tension tight. The percentage of shrinkage was less than 3%. This little shrinkage gave an assurance to the dimensional stability even though the reprocessing was at high level until fourteenth cycle. Scanning electron microscopy (SEM) images evident the homogeneous mixing and brittle manner of polypropylene during extensive recycling.