All ETDs from UAB

Advisory Committee Chair

Haibin Ning

Advisory Committee Members

Selvum Brian Pillay

Subhayu Sen

Vinoy Thomas

Document Type

Thesis

Date of Award

2023

Degree Name by School

Master of Science in Materials Engineering (MSMtE) School of Engineering

Abstract

High-density polyethylene (HDPE) is a widely used plastic for applications such as packaging for food industry and piping system in nuclear plants because of its beneficial properties, including lightweight, impact resistance, and chemical resistance. The use of HDPE can contribute to environmental problems, such as depletion of natural resources and accumulation of plastic waste in landfills and oceans. There is a growing need to find ways to recycle and reuse HDPE. While the use of recycled HDPE presents certain challenges such as relatively low thermal, mechanical properties, and flame retardancy, the addition of mineral-based additives can enhance these properties. By incorporating perlite, a natural mineral, as an additive in recycled HDPE, its thermal properties, mechanical properties, and flame retardancy can be enhanced. In this work, composites with different ratios of r-HDPE to perlite (neat r-HDPE, 10:1; and 10:2 r-HDPE/Perlite ratio) were produced by using a twin screw extruder (TSE). The composites were pelletized using an extrusion-compression molding (ECM) process. The composites were analyzed by using differential scanning calorimetry (DSC) to evaluate their thermal properties, such as melting point and degree of crystallinity. Mechanical tests, including tensile and flexural tests, were carried out to assess the mechanical properties and failure mechanism of the r- HDPE/perlite composites. To assess the flame retardancy of the composite, a flammability test was conducted. It was found that the degree of crystallinity increased, from 50% for neat r-HDPE to 55% and 62% for 10:1 and 10:2 r-HDPE/perlite ratios, respectively. Additionally, the Young's modulus increased from 0.89 to 1.14 GPa for neat r-HDPE and 10:2 r-HDPE/perlite ratio, while the tensile strength showed a slight increase. The flexural modulus of the composite increased by approximately 37.5% with the addition of perlite. Finally, the flame resistance was found to increase by around 17% with the incorporation of perlite, indicating improved flame retardancy. These findings suggest that perlite is a promising additive for enhancing the thermal and mechanical properties, crystallinity, and flame retardancy of r-HDPE.

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