New Study Examines the Resistance of PP-R to Chlorinated Water

It is widely known that disinfectants in potable water can lead to oxidative degradation in some plastic piping materials. Oxidative degradation occurs when chlorine, hypochlorites, chloramines and other disinfectants react with antioxidants in the pipe material, reducing the amount of antioxidants until the material is unprotected against oxidation and the pipe degrades.

Piping professionals and contractors should be aware of the chlorine resistance of the materials they choose and the effect of oxidative degradation on pipe performance. Consider the following facts:

Chlorine is the most common water disinfectant in the U.S.

Over time, chlorine causes oxidation in some plastic piping materials.

Oxidation degrades pipe and can lead to cracks, breaks and failures.

Experts have studied the chlorine resistance of certain polyolefin materials, but little research has been done on PP-R until now.

Polymer scientists continue to conduct research on the resistance of piping materials to water disinfectants and the effects of oxidative degradation.A new study led by Don Duvall, Ph.D., focuses on the results of testing the resistance of fiber-reinforced random copolymer polypropylene (PP-R) pipe,commonly green in color, to chlorinated water. Duvall is a polymer scientist with more than 39 years of experience in the plastics industry and has specialized in the engineering, testing and failure analysis of products manufactured from polymer materials.

When speaking about his work, Duvall underscores the importanceof studying all types of plastic piping products and their susceptibility towater disinfectants.

“Each product manufactured from a different polymer must beevaluated on its own to assess its oxidation resistance,” Duvall said.

PP-R is part of the polyolefin family of piping products,and in their raw forms, polyolefin materials cannot stand up to oxidativedegradation. As a result, stabilizing chemicals, including antioxidants, must be added to stave off oxidation.

“Polyolefin pipe is subject to oxidative degradation, a life limiting factor for the pipe, and must be properly stabilized,” Duvall said. “Each material, product and manufacturer has its own unique stabilizer package.”

Much research has been done on other materials in the polyolefin family, but until the study by Duvall and his colleagues, there had been littleresearch conducted on the oxidation resistance of PP-R.

“It is also important to consider that not all polyolefin materialsreact to water disinfectants in the same way,” Duvall said. “Because of thesedifferences, each material should be studied separately.”

Duvall will present his peer-reviewed paper, “Oxidation Resistanceof Polypropylene Random Copolymer Pipe to Chlorinated Water,” at the Society of Plastics Engineers’ (SPE) annual ANTEC conference April 22-24 in Cincinnati, Ohio. SPE seeks to educate industry professionals and consumers on the properties and performance of the plastics used in drinking water systems. ANTEC is the world’s largest plastics technical conference, and each year, it attracts scientists from across the globe to present their research findings on a range of topics. Failure analysis and prevention is a particularly popular topic, typically drawing 50-70 attendees per presentation.

Visit the ANTEC/SPE website to find out more about Duvall’spresentation on the oxidation resistance of PP-R.