Degradation profiles in aged EPDM water seals using focused ion beam-scanning electron microscopy

The degradation of an ethylene-propylene-diene (EPDM) rubber seal used in a water supply system was investigated using focused ion beam-scanning electron microscopy (FIB-SEM). The EPDM rubber seal was used for 3 years within the temperature range 20-40 °C in a city water system. The accretions present on the surface of the EPDM seal after use were observed by SEM and were found to consist of iron and oxygen atoms based on energy dispersive X-ray spectroscopy (EDS) analysis. A cross-sectional depth image of the EPDM rubber was obtained by FIB-SEM, after slicing the EPDM rubber with a focused Gallium ion beam. Iron and oxygen atoms in the cross-section of the EPDM rubber were detected through EDS. The distribution of iron was comparable to that of oxygen derived from the carbonyl groups generated by the degradation of EPDM, suggesting that iron ions may promote the degradation of natural rubber through catalytic effects.