HNBR elastomer composite with zero thermal contraction over a range of temperatures

Elastomers such as hydrogenated nitrile butadiene rubber (HNBR) are known to have inferior dimensional stability upon temperature changes compared to metallic materials. This can result in thermal contraction mismatches between metal and elastomer sealing components during cooling, possibly leading to seal leakage. It has also been reported that MnCoGe alloys have been developed that undergo a phase change which results in a volumetric expansion during cooling through the phase change temperature region. This article reports the effect of adding MnCoGe-alloy particles into a HNBR elastomer with the purpose using the thermal expansion of the alloy particles to counteract the thermal contraction of this elastomer during cooling. The composite material is produced using a combination of solvent casting and traditional shear mixing in a two-roll mill followed by compression moulding. With the MnCoGe volume fraction of 17%, a considerable suppression of the thermal expansion coefficient of the base elastomer was achieved, going from to nearly zero in the range of temperatures from -5 to +15C . The positive effect of the filler on the thermal expansivity was apparent in wider temperature range of -20 to +40C .