Elastomeric Compounds Degradation in Drinking Water Distribution Systems

Due to the increasing health concerns and USEPA regulations over the last decade, chloramines have preferentially been used in place of chlorine as disinfectant. After this change, some utilities have reported high elastomeric compound failure rates in their water systems. To predict the long-term performance of elastomers within the water systems, accelerated degradation experiments were conducted at the combinations of three temperatures (23oC, 45oC and 70oC) and three chloramine concentrations (1-, 30-, and 60 mg/L concentrations) for natural rubber, neoprene rubber, ethylene propylene diene monomer (peroxide-cured), ethylene propylene diene monomer (sulfur-cured), styrene butadiene rubber, and nitrile rubber. Elastomer degradation was characterized by mass change, volume change, breaking stress, breaking strain and hardness. Using a time-temperature superposition (TTS) principle the accelerated test results were doubly-shifted (temperature and chloramine concentration) to service conditions to generate long-term performance curves. TTS technique was not suitable for swelling data, hence, performance curves for swelling were developed using diffusion theory. Also, the possible leaching of organic compounds due to this elastomer degradation into drinking waters has been investigated using Solid Phase Micro Extraction and Gas Chromatography/ Mass Spectrometry.