Ashish M. Sukhadia, Wes Long
Papers # 2018 Las-Vegas
Polyethylene (PE) pipe is a frequent choice for transporting slurry solutions. It has proven to have superior wear resistance than other pipe materials. For example, when carrying fine grain slurries, polyethylene pipe has been shown in laboratory tests to be three to five times more wear resistant than steel pipes. Abrasion resistance of plastics is dependent on numerous factors – the nature of the plastic, surface roughness, lubricating agents, load, material hardness, and others. Contrary to intuitive belief, abrasion resistance of plastics does not correlate directly with hardness. Test data will be presented to show that unimodal medium-density PE (MDPE) pipe provides at least 30 % greater abrasion wear resistance compared to other high-density PE (HDPE) pipes tested, translating to longer service life in these application areas. We will attempt to explain these results based on the polymer structure-property fundamentals governing the abrasion response of polymers.
Three different polyethylene (PE) pipe grade resins were compared for abrasion wear resistance performance. The three PE grades were - (1) a unimodal medium density PE, (2) a unimodal high-density PE and (3) a bimodal high-density PE. Testing was performed to measure the resistance to wear due to slurry abrasion at both ambient temperature (73 °F) and at elevated temperature (140 °F). The testing was done per ASTM G75-15, “Standard Test Method for Determination of Slurry Abrasivity (Miller Number) and Slurry Abrasion Response of Materials (SAR Number)”. Contrary to intuitive expectations, the results showed that the unimodal MDPE pipe provided at least 30 % greater abrasion wear resistance compared to two other HDPE pipes tested. The data also supported similar slurry abrasion wear resistance performance at the elevated temperature. These abrasion wear results were investigated further from the polymer fundamentals standpoint. It was shown that these results were due to the particular polymer structureproperty interactions relating to the “effective number of physical cross-links per macromolecular chain”, a concept originally proposed in the literature by T. A. Tervoort et al. (Macromolecules., 35, 8467-8471, 2002). Based on the results of this investigation, it is shown that the unimodal MDPE pipe is expected to perform very well in slurry flow applications and is indicated to be a better choice than other higher density polyethylene pipe materials due to its better resistance to abrasion.
