Assessment of Mechanical Properties of Recycled HDPE and LDPE Plastic Wastes

Abstract

Most plastic materials can be recycled, and turning them into some useful products can be one of the options in reducing environmental pollutions. In this project, High Density Polyethylene (HDPE) and Low Density Polyethylene (LDPE) were used, shredded into smaller pieces and were hot-pressed to become flat plates. Both materials were then mixed with industrial waste sawdust with an aim to investigate their material properties and their suitability to be used in domestic applications such as bricks, pavement and roof tiles. Three destructive and one non-destructive methods have been conducted: tensile, impact, water absorption and ultrasonic testing. It was found that the tensile properties and impact resistance of the recycled HDPE are better than the recycled LDPE, but 10% lower than their virgin polymers. Higher stiffness and lower impact resistance were observed from specimens with additional sawdust filler in comparison to their original polymers. From the ultrasonic measurement, higher wave velocity and lower attenuation in HDPE specimens were observed, compared to the LDPE specimens, attributed by a higher modulus and density of the HDPE specimens. The ultrasonic velocity, which reflects the elastic modulus, and the attenuation that reflect the microstructure inhomogeneity are respectively decreased and increased when more fillers were added to the original specimens. This study reveals that the mechanical properties of the recycled HDPE and LDPE are closer to their virgin materials, and they have huge potential for plastic recycling.