Recycling of crosslinked high density polyethylene through compression molding

Abstract

Crosslinkable high density polyethylene (XHDPE) is used to manufacture large and rigid products such as fuel tanks using a rotomolding process. Currently, defective and post-consumer parts are not recycled and sent to landfills. Hence, recycling of this material through compression molding is the objective of this study. Thermal analysis revealed that the extent of crosslinking varied across the thickness of the rotomolded part due to the role played by air. Due to limited crosslinking, the recycled XHDPE (RXHDPE) could be remelted with higher viscosity than the virgin XHDPE (VXHDPE). Consolidation studies using rheometer indicated that both RXHDPE and VXHDPE could be compression molded to a density of 0.952 g/cm3. However, higher consolidation stress is required for RXHDPE when compared to VXHDPE to realize the same density. RXHDPE, compression molded at 1.6 MPa and 230°C, had properties similar to those of VXHDPE molded at 0.321 MPa, demonstrating the recyclability.