Document Type

Article

Publication Date

4-17-2024

Abstract

Plastic pollution is a rapidly growing global problem. Current methods of plastics disposal cause even greater environmental impacts. For example, landfills are at capacity, incinerators are increasing greenhouse gases, and microplastics are polluting woodlands and water ways. Thermoplastics recycling of high-density polyethylene (HDPE) has become a focal point in the plastics industry. In this study, we demonstrated the effects that different processing levels have on HDPE physical properties. We processed and analyzed six different plastics: “virgin HPDE”, “internal regrind”, “internal regrind pelletized”, “repro”, “repro with additive”, and “flake”. We first processed the material that was donated to us by Rehrig Pacific into test bars using twin-screw extrusion compounding and injection molding. We then tested mechanical properties such as tensile strength, flexural strength, and impact strength, as well as thermal properties via differential scanning calorimetry, thermogravimetric analysis, and melt flow analysis. Thermal analysis showed no substantial difference between the materials analyzed. All materials had similar mechanical properties with the exception of “repro”, which had higher flexural strength, and lower tensile strength and elongation. Melt flow analysis indicated that “internal regrind pelletized” had slightly lower melt viscosity compared to other materials, suggesting that extrusion may have reduced the material’s molecular weight. Additionally, inclusion of an additive to “repro” improved all material properties we studied. We have demonstrated that differences in post-industrial and post-consumer treatment had an effect on physical properties of plastics, and we can process recycled plastics into plastic parts while gaining a better understanding of processing effects on material properties.

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