Degradation of EPDM seal used for water supplying system

Degradation of ethylene-propylene-diene (EPDM) rubber seal used for supplying water system was investigated through spectroscopic techniques. The EPDM seal was utilized at 20-45 °C for about 3 years. It was characterized by solid state nuclear magnetic resonance spectroscopy equipped with field gradient fast magic angle spinning probe and Fourier transform-infrared spectroscopy. Morphology of the EPDM seal was observed by scanning electron microscopy, focused ion beam scanning electron microscopy and electron probe micro-analysis. The hardness and crosslink density of EPDM seal were reduced by a factor of one-half after using for supplying water system, even though it contains little amount of carbon-carbon double bond. Surface of the EPDM seal was significantly damaged by water. The degradation of EPDM seal was associated with chain scission and oxidation of EPDM.