Effect of mechanical recycling on crystallization, mechanical, and rheological properties of recycled high-density polyethylene and reinforcement based on virgin high-density polyethylene

This study investigated the effects of mechanical recycling on the crystallization, mechanical, thermal, and rheological properties of recycled high-density polyethylene (rHDPE), as well as vHDPE/rHDPE pellets and films made by different compositions. The results confirmed the presence of contaminants in rHDPEs, and the crystalline diameter of rHDPE is smaller than that of virgin high-density polyethylene (vHDPE), with diameters ranging from 0.60 to 0.72 mu m. The content of 75 wt% vHDPE in rHDPE film could repair the defects of crystalline morphology to approximate that of vHDPE films and significantly improve the elongation at break. The temperature required for the transition from crystalline to amorphous state of rHDPE film was 2 degrees C lower than that of vHDPE, and the crystallization time and crystallinity declined compared to that of vHDPE. For rheological performance, the apparent shear viscosity and melt fluidity of rHDPE were worse than those of vHDPE. The blending of low rHDPE with vHDPE is a feasible option not only to reduce plastic waste but also to maintain acceptable properties of the blend composition. Changes in the crystalline morphology, thermal, mechanical, and rheological properties of rHDPE pellets and films during preparation and processing.image