Comparative Analysis of Wear Behaviour of Commercial Polymeric Pipe Materials under Different Sliding Environments

Abstract

The current study was conducted to compare the wear behaviour and frictional nature of three commonly used commercial polymers namely, uPVC (Unplasticized polyvinyl chloride), High Density Polyethylene (HDPE) and Acrylic. The aim was to find out the effect of various loads at various sliding distances on wear characteristics and frictional nature of the materials. A vertical pin-on-disk method was used throughout the experiment. All experiments were carried out in normal ambient conditions of relatively high summer temperatures (approximately 30⁰C) and high relative humidity (80%). The sliding velocity was kept at 0.6397 m/s and the sliding distance was varied from 192.423 m to 4618.152 m. The loads were 0.025 kg, 0.5 kg, 1.0 kg, and 2.0 kg respectively. The experiments were done in three different surface mating conditions, dry, wet and claywater. It was verified that the weight loss increased with increase in sliding distance and load. Density and hardness of the different polymers were also measured. Also it was studied to see whether the wear behaviour and frictional resistance had any correlation to each other and it was found that there was no noticeable relationship between wear rate and friction coefficient (µ). However both the frictional coefficient and wear rate varied with load. Different surface mating conditions (dry, wet and clay-water) showed effect on the friction coefficient (µ) and wear rate as well. It was found that in general friction coefficient (µ) of HDPE was least of the three in all experimental conditions, while acrylic had the highest, and uPVC fell in between. The wear behaviour also showed a similar trend in that HDPE had the least wear for a given load at a particular sliding distance and at a specified surface mating condition while Acrylic showed the most wear with uPVC falling in between. The reason behind the excellent wear and frictional behaviour of HDPE is due to the difference in the crystallinity of the three polymers. HDPE is almost fully crystalline in nature while Acrylic is almost fully amorphous and uPVC has higher portions of crystalline region compared to acrylic. Generally the higher the crystallinity the better the frictional and wear characteristics of any material. Optical microscopic analysis of the specimen, dust and disk was also made. EDX and ESM observations were also made which showed that uPVC was most affected by oxidation followed by HDPE and then Acrylic.