Experimental Study and Process Optimisation for Fabrication of Circular Sheet Made from Waste PP/HDPE via Extrusion and Hydraulic Press

Plastic waste is a well-known hazard to the ecosystem due to which many countries are exploring ways to mitigate this polymer from the environment. Various plastic wastes are generated after end use in the form of plastic bottles, plastic bags, bottle caps, straw, plastic cups, etc. These are generally made up of HDPE, LPDE, PP, PET, PS, etc. Therefore, this study focusses to utilise this wastage to make some value-added products. In this context, waste plastic bottles and containers made up of polypropylene and high-density polyethylene were targeted and shredded into small pieces ranging from 1.4 to 2 mm and mixed with additives in the extruder and hydraulic press to make circular sheets that can be used for electrical purposes. During the study, the effect of various process parameters on fabricated circular sheet properties such as tensile strength, melt flow index (MFI), and thermal conductivity were investigated. The developed non-linear theoretical models were found to be in good agreement with the experimental data. The gradient descent method is applied in BBD for estimating the optimum condition for fabricating a circular sheet. Under optimum conditions, the tensile strength and thermal conductivity were found to be 1535 MPa and 0.0312 W/mK, respectively, for the HDPE circular sheet using extrusion. The tensile strength, MFI, and thermal conductivity were determined using a Universal testing machine, melt flow tester (ASTM D1238), and Thermal constant analyser based on ASTM D1350.