(591h) A Review of Elastomers in CO2 and H2 Environments

Frontier areas like Carbon capture, utilization and storage (CCUS), Hydrogen transportation and storage, present a set of unique challenges to materials technology, especially when it comes to picking the right elastomers for respective applications. Carbon dioxide (CO₂) and Hydrogen (H₂) can affect elastomers physically and chemically, through interactions between gas molecules and polymer chains. This work provides an overview of elastomers behavior’ for applications at relevant conditions.

Information presented in this paper is a review of published peer-reviewed publications in testing of polymeric materials in CO₂ and H₂ environment at different physical conditions. Data is categorized by the concentration of gases and the type of tested material, including fluoroelastomers (FKM, FEPM, FFKM), nitrile elastomers (NBR, HNBR), and EPDM. Elastomers are compared in their resistance to CO₂ and H₂ environments through assessment of their tensile properties (strength, modulus, elongation), compressive set, and resistance to rapid gas decompression. Testing results are summarized and interpreted through the lens of elastomer chemistry and molecular interactions between polymer chains and gas molecules.

Effects of CO₂ on elastomers can be chemical or physical in nature. Physical effects include swelling, change in hardness, and damage during rapid gas decompression (RGD). The magnitude of the effects is connected to chemical structure of the polymer, crosslinking density and compound composition. Chemical degradation of the polymer chains on the other hand is responsible for diminishing mechanical properties of the elastomers, it can also exacerbate negative impact of RGD.

Due to absence of polar groups EPDM showed the least amount of swelling in CO₂. Impact of CO₂ on nitrile elastomers (NBR, HNBR) was more pronounced and correlated with acrylonitrile (ACN) fraction in elastomer chain. Fluoroelastomers exhibited even higher swelling in CO₂, than nitrile elastomers but demonstrated stronger chemical resistance to CO₂. Fluoroelastomers better preserved their tensile properties after exposure to CO₂ compared to nitrile elastomers.

Effects of H₂ on elastomers have shown to be primarily physical in nature, with little to no chemical effects on the elastomer chain. Uniquely small size of H₂ molecule leads to high diffusivity of the molecule in elastomer matrix. However, H₂ still has shown to be causing RGD damage to fluoroelastomers and nitrile elastomers at certain conditions.

This paper provides a novel perspective on chemical and physical effects of environments typical to frontier applications on polymeric materials. Overview of the current state of the art in elastomers provided in this presentation will help guide future developments in the area.