Unveiling the\nPressure-Induced Dynamics on the Glass\nTransition Temperature of Hydrogenated Nitrile Rubber

The changes in the glass transition (<i>T</i><sub><i>g</i></sub>) of elastomers due to high-pressure\ngases can have\nimportant consequences for their mechanical, physical, and thermal\nproperties. In this work, the behavior of <i>T</i><sub><i>g</i></sub> of un-cross-linked and cross-linked hydrogenated\nnitrile rubbers (HNBR) under pressure was investigated. The cross-link\ndensity, chemical structure of the rubber, and filler loading were\nvaried. It was observed that the <i>T</i><sub><i>g</i></sub> of the un-cross-linked HNBR (without any filler) decreased\nwith the increasing pressure of nitrogen gas and was accompanied by\nincreasing solubility of N<sub>2</sub> gas in the elastomer. However,\nincreased cross-link density, filler content, and acrylonitrile (ACN)\ncontent in the HNBR significantly increased the <i>T</i><sub><i>g</i></sub> value under pressure. A theoretical\nthermodynamic model that relates the pressure dependence of the volumetric\nproperties of an elastomer, based on the principles of corresponding\nstates, was used to model the experimental data. The work will help\nin the design of elastomeric products used in high-pressure environments.