Unveiling the Pressure-Induced Dynamics on the Glass Transition Temperature of Hydrogenated Nitrile Rubber

The changes in the glass transition (Tg) of elastomers due to high-pressure gases can have important consequences for their mechanical, physical, and thermal properties. In this work, the behavior of Tg of un-cross-linked and cross-linked hydrogenated nitrile rubbers (HNBR) under pressure was investigated. The cross-link density, chemical structure of the rubber, and filler loading were varied. It was observed that the Tg of the un-cross-linked HNBR (without any filler) decreased with the increasing pressure of nitrogen gas and was accompanied by increasing solubility of N2 gas in the elastomer. However, increased cross-link density, filler content, and acrylonitrile (ACN) content in the HNBR significantly increased the Tg value under pressure. A theoretical thermodynamic model that relates the pressure dependence of the volumetric properties of an elastomer, based on the principles of corresponding states, was used to model the experimental data. The work will help in the design of elastomeric products used in high-pressure environments.