  Rubber compounds for pressure sealing application typically have inferior
dimensional stability with temperature fluctuations compared with their steel
counterparts. This effect may result in seal leakage failures when subjected to
decreases in temperature. Composites of hydrogenated nitrile butadiene rubber
(HNBR) and zirconium tungstate as a negative thermal expansion filler were
prepared in order to control the thermal expansivity of the material. The
amount of zirconium tungstate (ZrW2O8) was varied in the range of 0 to about 40
vol%. The coefficient of thermal expansion (CTE), bulk modulus, uniaxial
extension and compression set properties were measured. The CTE of the
ZrW2O8-filled HNBR decreases with the filler content and it is reduced by a
factor of 2 at the highest filler concentration used. The filler effect on CTE
is found to be stronger when HNBR is below the glass transition temperature.
The experimental thermal expansion data of the composites are compared with the
theoretical estimates and predictions given by FEA. The effect of ZrW2O8 on the
mechanical characteristics and compression set of these materials is also
discussed.
