Experimental and Modelling Study on CO2 Solubility, Diffusivity and Tg Depression in Elastomers at Various Temperatures

The accumulation of carbon dioxide (CO2) in the atmosphere, resulting from human activities, has significantly contributed to global warming. Carbon Capture and Storage (CCS) emerges as the most readily available technology aimed at reducing CO2 emissions. Within the CCS framework, CO2 transport is necessary to move the gas from the capture sites to storage locations, using pipelines and ships. Polymers play a crucial role in this process by preventing metal corrosion, acting as seals to avoid leakage, and functioning as gaskets. CO2 is soluble in polymers due to its affinity with polymeric macromolecules. Since its absorption influences the material properties, it is essential to determine which polymers can effectively be used. The goal of this thesis is to study CO2 solubility, diffu- sivity, and how CO2 absorption affects the Glass Transition Temperature (Tg) in polymers, through experimental and modelling approaches. Three elastomers, including one HNBR and two EPDM samples, are analysed using a pressure decay method. The experiments demonstrate that EPDM generally shows lower CO2 solubility compared to HNBR. The types of EPDM analysed have different amounts of carbon black content, which does not contribute to CO2 absorption but influences diffusivity. The Peng-Robinson and the Lat- tice Fluid Equations of State are employed to analyse the experimental data obtained and to extrapolate solubility and diffusivity data at temperatures different from those used in the laboratory, which can be useful for studying CO2 transport by ship. For the analysis of Tg, gravimetric desorption tests and Differential Scanning Calorimetry (DSC) are used to correlate the CO2 content in the polymer with the corresponding Tg value. The ex- periments demonstrate that each measured Tg value corresponds to a specific amount of absorbed CO2. Chow’s model is used to analyse the experimental Tg depression values, and it proved to be valid for accurately describing the analysed materials.