Oxidation Resistance of Polypropylene Random Copolymer Pipe to Chlorinated Water

Abstract

Polyolefin pipe is known to be susceptible to oxidative degradation when used in potable water applications. Flowing water inside of such pipe will extract antioxidants from the inside surface of the pipe, causing diffusion-driven migration of more antioxidant from the pipe mid-wall to that surface. Disinfectants in potable water (e.g., hypochlorites, chlorine dioxide, chloramines, etc.) react with antioxidants in the pipe material, decreasing the amount of effective antioxidant until none remains and the polymer is unprotected against oxidation. Also, the response of polyolefin materials to oxidative degradation and the effect of such degradation on pipe performance varies with the different polyolefin polymers. This study presents the results of testing of the resistance of random copolymer polypropylene pipe to chlorinated water and the failure mechanisms observed in the tests.