Thermomechanical properties of zirconium tungstate/hydrogenated nitrile butadiene rubber (HNBR) composites for low-temperature applications

TL;DR

This study explores how zirconium tungstate filler influences the thermomechanical properties of HNBR composites, aiming to improve low-temperature sealing applications by reducing thermal expansion and maintaining mechanical integrity.

Contribution

It introduces zirconium tungstate as a filler in HNBR to control thermal expansion and evaluates its effects on mechanical properties and thermal behavior.

Findings

ZrW2O8 reduces HNBR's CTE by up to 50% at high filler content.

Filler effects are more pronounced below the glass transition temperature.

Experimental results align with theoretical FEA predictions.

Abstract

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.