Development of validation method for use of Miner's rule in predicting oxidative resistance of polyolefins

Abstract

With the implementation of NSF Protocol P171 in 1999, and subsequent adoption of ASTM F 2023 in 2000, Miner's rule has been used extensively in developing estimations of crosslinked polyethylene (PEX) pipe lifetimes when exposed to varying system conditions in the presence of chlorinated water. Previous work in this area demonstrated that Miner's rule can be effectively used and validated for some polyolefins under standard hydrostatic test conditions, but that significant deviations can also occur depending on the material. The present paper presents the results of similar work towards a validation method for Miner's rule, specifically focused on flowing systems with an aggressive water matrix to accelerate oxidation of the polymer. The use of Miner's rule proved to be a reasonable approximation for some materials, but as with the earlier work, overly optimistic for other materials. The present paper also discusses the proposed method to be incorporated into the applicable ASTM products standards for PEX and polypropylene (PP) piping and minimum criteria established.

Keywords:

• MINER'S RULE
• CHLORINE
• OXIDATION
• POLYOLEFIN
• PEX
• DAMAGE