Pressure-Property Relationships in High-Performance Elastomers

High-performance elastomers, hydrogenated nitrile butadiene (HNBR), and fluoroelastomer (FKM), widely used in high pressure gas environments, have attracted significant interest from both fundamental research and industrial development. The changes in the glass transition temperature (Tg) and gas sorption behavior of elastomers due to high-pressure gases can have important consequences on their mechanical, physical, and thermal properties. Therefore, it is crucial to understand the effect of pressure on the structure and properties of the elastomer in terms of Tg and gas transport behavior. In the first approach, the behavior of Tg of the HNBR system under pressure, and its relationship with gas solubility, crosslink density, loading and types of filler, and chemical structure under pressure, were investigated. It was observed that absorbed gas molecules have a significant impact on the change of Tg with pressure. We note that the Tg of the uncrosslinked HNBR decreased with increased pressure of N2 and was accompanied by increased solubility of N2 gas in the elastomer. However, with increased crosslink density, filler content, and acrylonitrile (ACN) content in the HNBR, Tg values increased and N2 gas solubility decreased with increased pressure However, changes in gas transport properties as a function of pressure are poorly understood. Here, we quantitatively investigated how gas sorption changes as a function of pressure and temperature in FKM. In this work, we investigated the effect of pressure and temperature on CO2 and N2 gas sorption. The kinetics of sorption for both gases was modeled and analyzed. In addition, the impact of pressure and temperature on the diffusivity and permeability of gases in FKMs has been quantitatively interpreted. The solubility and diffusivity of gases decrease by increasing carbon black loading up to 40 wt% at 50 °C. Moreover, the correlation between gas molecular properties and transport properties of gases in FKM was quantitatively investigated. Together, this work further expands the scientific knowledge of the pressure effects on polymer Tg and gas sorption of elastomers in gas environments and provides insight into potential solutions for developing high performance elastomers for applications in high pressure gas environments.