Cryo-compressed CO₂ sorption and diffusion in elastomers for the CO₂ transport chain: Examples of FKM, EPDM and HNBR

Carbon capture and storage (CCS) is critical for achieving net-zero CO₂ emissions by 2050, necessitating efficient and reliable CO₂ transport solutions. The present study investigates the suitability of typical various elastomers for sealing applications in CCS infrastructure, focusing on fluoro-elastomers (FKM), nitrile rubbers (HNBR), and hydrocarbon-based rubbers (EPDM). These materials were tested to evaluate CO₂ solubility and diffusivity under temperature and pressure conditions relevant to CO₂ transport. Six different grades of elastomeric materials, characterized by different filler content (carbon black − CB), were inspected by means of a pressure decay method, spanning from room to cryogenic temperatures. The results indicated that of the materials tested in this research, the FKM tested exhibited a relatively large CO₂ uptake, which was attributed to fluorinated structure, while EPDM showed a rather low affinity for CO₂, attributed to its nonpolar nature. The solubility and diffusivity of CO₂ in the materials investigated were analyzed using the Lattice Fluid equation of state and diffusivity models, extending the understanding of CO₂ behavior in elastomers beyond the tested conditions, including both vapor and liquid CO₂. The study highlights the critical role of CO₂-induced swelling of the polymer matrix, and the resulting plasticization, crucial features for the sealing performance of elastomers in CCS applications, providing valuable insights for the development of a robust and safe CO₂ transport infrastructure.