Abstract
High density polyethylene (HDPE) is a thermoplastic polymer which is classified as one of the highly consumed types of plastics. One major advantage of thermoplastic materials is their ability of recycling and reprocessing which will bring considerable economicand environmental benefits. The present paper, therefore, endeavours to explore the practical possibility of using recycled HDPE hollow section as a replacement of virgin HDPE made by the extrusion process. The main focus of the study was to evaluate the mechanical performance of the recycled HDPE and compare the results with virgin or non-recycled HDPE. The modulus of elasticity, tensile yield and ultimate strength, compressive yield and ultimate strength, flexural yield and ultimate strength and the coefficient of thermal expansion were the main parameters to be checked against the respective mechanical properties. Thus, pursuant to the rsults, it was found out that the modulus of elasticity and the tensile yield strength are lower in recycled HDPE compared to the non-recycled HDPE. However, there is no significant difference between the recycled and non-recycled HDPE for the tensile ultimate strength, compressive yield strength and compressive ultimate strength. The flexural yield strength and flexural ultimate strength properties of the recycled HDPE proved to be superior to those of the non-recycled HDPE. The coefficient of linear thermal expansion of the recycled HDPE sample was 130 μm/(m.°C) and that for the non-recycled HDPE was 142 μm/(m.°C).
Highlights
Polyethylene (PE) is one of the highly consumed polymers in the world available with different density grades
The greater the proportion of crystalline regions, the higher the density of the material. Crystalline regions are those which are highly ordered and densely packed molecular chains, and it is these crystalline regions that might have been affected during the recycling process which results in a decreased density of the recycled High density polyethylene (HDPE) (Andersson, 2004)
Subject to the modulus results, the recycled HDPE has a lower modulus value against the non-recycled HDPE which prompts a reduction in the material properties after recycling
Summary
Polyethylene (PE) is one of the highly consumed polymers in the world available with different density grades. High density polyethylene (HDPE) is a thermoplastic polymer used to manufacture variety of products including bottles, pipes etc. HDPE structure is described as semicrystalline with a combination of amorphous and thin lamellae crystals (Harper, 2000). The greater the degree of crystallinity, the higher the tendency of the materials brittleness due to the weak interfaces between each crystal structure. The combination of crystalline and amorphous regions secures the HDPE extreme toughness and brittleness at lower temperatures, causing it to become rubbery and more flexible at higher temperatures which, in turn, builds up to the HDPE improved recycling and reprocessing ability (Rudolph, Kiesel, & Chuanchom, 2017)
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