Oxidation Resistance of Polypropylene Random Copolymer Pipe to Chlorinated Water
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.
KeywordsPolypropylene Piping Oxidation Regression analysis Environmental failures Accelerated testing Plastics
The author gratefully acknowledges the financial support of Lubrizol Advanced Materials Inc. in this work.
- 4.S.W. Choi, Surface Embrittlement of Polyethylene, Ph.D. Thesis, Department of Metallurgical & Materials Engineering, Illinois Institute of Technology, Chicago, IL, May 1992Google Scholar
- 5.A.J. Bowman, Paper 21 presented at the Plastics Pipes VII International Conference, University of Bath, England, 19–22 September 1988Google Scholar
- 6.ASTM F2023, in Standard Test Method for Evaluating the Oxidative Resistance of Crosslinked Polyethylene (PEX) Tubing and Systems to Hot Chlorinated Water. Annual Book of ASTM Standards, Volume 08.04 (ASTM International, West Conshohocken)Google Scholar
- 7.NSF P171, Protocol for Chlorine Resistance of Plastic Piping Materials (Sept. 10) (NSF International, Ann Arbor, 1999)Google Scholar
- 8.N.B. Colthup, L.H. Daly, S.E. Wiberley, Introduction to Infrared and Raman Spectroscopy, Chapter 9, 2nd edn. (Academic Press, New York, 1975)Google Scholar
- 9.M. Ezrin, Plastics Failure Guide: Cause & Prevention (Hanser/Gardner, Cincinnati, 1996), p. 110Google Scholar
- 10.J. Scheirs, Compositional and Failure Analysis of Polymers: A Practical Approach (Figure 14.3) (Wiley, West Sussex, 2000)Google Scholar
- 11.ASTM F2023-10, Standard Test Method for Evaluating the Oxidative Resistance of Crosslinked Polyethylene (PEX) Tubing and Systems to Hot Chlorinated Water, Section 13.1, 2012 Annual Book of ASTM Standards, Volume 08.04 (ASTM International, West Conshohocken, 2002)Google Scholar
- 12.D.C. Montgomery, E.A. Peck, Introduction to Linear Regression Analysis (Chapter 4), 2nd edn. (Wiley-Interscience, New York, NY, 1992), pp. 135–138Google Scholar
- 13.D.C. Montgomery, E.A. Peck, Introduction to Linear Regression Analysis, 2nd edn, (Wiley-Interscience, New York, NY, 1992), pp. 85–89Google Scholar
- 14.ASTM F2389-10, Standard Specification for Pressure-rated Polypropylene (PP) Piping Systems, 2012 Annual Book of ASTM Standards, Volume 08.04 (ASTM International, West Conshohocken, 2012)Google Scholar
- 15.International Standard ISO 13760, Plastic Pipe for the Conveyance of Fluids Under Pressure—Miner’s Rule—Calculation Method for Cumulative Damage (International Organization for Standardization, Geneva, Switzerland)Google Scholar