Francis Reny Costa, Anh Tuan Tran, Jeroen Oderkerk, Thomas Hjertberg, Christophe Salles, Ulf W. Gedde, Benjamin Rabaud, Flavia Zraick
Papers # 2016 Berlin
The premature failure of polyethylene pipes in contact with high chlorine and chlorine dioxide, used as residual disinfectants in drinking water distribution, remains an area of concern for water companies particularly in regions where temperatures are regularly or seasonally high. Multiple factors can amplify the adverse effects of these disinfectants on the performance of polyolefin pipes. The formulation of the polyethylene resin and its inherent chemical stability against such oxidants is one key factor and an important starting point to extend the lifespan of distribution infrastructure with improved pipe performance. In many cases, selecting a suitable resin may be the only solution an operator can act upon since other factors are often dictated by distribution requirements (disinfectant concentration, pressure, water temperature). In the design of the resin, it is the additive package that has the biggest influence on the recipe optimization against disinfectants followed by the improved SCG performance to resist initial cracks. A robust additive package should, on the one hand, possess a high chemical stability against the oxidative disinfectants and, on the other, ensure sufficient stabilization of the polymer resin itself over a long period of time. A major challenge in the development of new disinfectant resistant resins is linked to the long timeframe (up to 18 months) currently required by a pilot scale pipe testing method to evaluate the performance of different formulations. In this study, we propose a complementary accelerated test method that can be used to benchmark the stability of the additive package against chlorine dioxide treated water. Results from this accelerated test method and pilot scale pipe testing are compared to demonstrate the effectiveness of the test strategy in differentiating among various polyethylene resins and identifying the best performing solution.