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.