HNBR-based composite for seals used in coolant fluids: Swelling related to different silicates at high temperature

The effects of five fillers (two synthetic calcium silicates, one natural calcium silicate, talcum and a low specific surface area carbon black) filled with hydrogenated acrylonitrile butadiene rubber (HNBR) for possible use in seal for coolant fluids were developed by hardness, mechanical properties and hot air aging properties. Fluid blends were used to simulate the degraded OAT coolant. The swelling mechanism of HNBR vulcanizates was investigated by XRD, SEM, EDS, FT-IR and GC-MS. The results indicated that the filler with high specific surface area was easier to combine with HNBR. Hot air aging tests revealed a relatively high heat resistance and can meet the practical requirements. 2-ethylhexanoic acid hydrolyzed by sodium 2-ethylhexanoate as corrosion inhibitor react with silicate fillers in rubber to form 2-ethylhexanoate into the coolant, thus the network structure of rubber destroyed, while 2-ethylhexanoic acid and ethylene glycol diethyl-hexanoate as well as a small amount of ethylene glycol and water immersed into rubber. Higher crystallinity and lower specific surface area made natural CaSiO3 an efficient intrinsic base reserve to scavenge acidic products and effectively reduce the swell of filled HNBR.