(574f) Experimental Characterization of Elastomers for the CO2 transport Applications

Carbon Capture and Storage (CCS) technology has gained significant attention following the Paris Agreement and the Climate Change Panel [1,2]. In this concern, CCS technology utilizes either pipelines or ships depending on their economic feasibility and transportation factors such as distances and emission capacity. These different transportation modes require different temperature and pressure conditions, down to cryogenic or supercritical environments, and they have different effects on the polymeric materials [3]. Even though elastomers comprise only a small portion of the CCS value chain since they are mainly used as sealants and gaskets, they are essential for controlling leakage and failure and protecting their mating metal components from corrosive environments [4]. However, polymers may absorb CO₂ molecules that can interact with the matrix by changing the material performances, leading to a plasticizing effect or Rapid gas decompression (RGD) damage [5].

Therefore, this work focuses on proposing a comprehensive approach towards experimental characterization and modeling, specifically tailored to CO₂ transportation in elastomers, with particular attention to Ethylene Propylene Diene Monomer (EPDM), Butyl Rubber (BR), Natural Rubber (NR), and Viton (FKM). The compatibility of elastomers with high-pressure CO₂ is investigated as a function of additives, coupled with different temperatures and pressures for swelling, plasticization phenomena, and mechanical resistance. In fact, CO₂ might lead to an increased backbone mobility and free volume due to the large penetrant solubility, coupled with significant changes in the material mechanical and thermal properties. To this aim, the elastomers have been characterized by thermal, using TGA and DSC, and mechanical DMTA analysis, before and after being exposed to high-pressure CO₂, to better comprehend the correlation between the intrinsic properties of the materials and the strength and durability of the in carbon transport scenarios. In parallel, EPDM, NR, BR, and FKM have been tested via carbon dioxide transient-sorption and direct permeation tests, before and after beign exposed to chloroform for filler extraction, to obtain and compare solubility, diffusivity, and permeability coefficients in mild operating conditions. Large CO₂ uptake can lead to the plasticization of the matrix and, thus, to the reduction of elastomer stiffness, while a large permeability might allow volume deformation that causes geometrical mismatches and seal extrusion [6,7]. Moreover, the research explores the role of reinforcing fillers incorporated into the polymer matrix, evaluating their influence on mechanical, and CO₂ transport properties.

The results demonstrate the extent of polymer plasticization induced by the solubilization of CO₂, at high frequency, which leads to a significant enhancement of the storage and loss energy modulus. Moreover, the higher content of carbon black and additives increases the stress resistance and the stiffness of the polymer, especially for elastomers containing carbon black, such as EPDM and FKM. For what concern transport phenomena, the higher solubility of NR accelerates polymer swelling, further leading to the dilution of low molecular weight compounds or weak intermolecular interactions. On the other hand, the low diffusivity of CO₂ in BR, probably due to the presence of fillers, plays against the wrapped chains, trying to swell the polymer structure which cannot recover after desorption thus leading to blistering phenomena.

These findings provide valuable insights into understanding the performance of elastomers under gas exposure and the complex interaction between supercritical CO₂ and polymers, relevant for the carbon transport chain, in view of their future use in industrial applications.

REFERENCES

1. Erickson, L.E.; Brase, G. Paris Agreement on Climate Change. Reducing Greenhouse Gas Emissions and Improving Air Quality 2019, 11–22, doi:10.1201/9781351116589-2.
2. The Intergovernmental Panel on Climate Change (IPCC) Why the IPCC Was Created.
3. Davies, O.M.; Arnold, J.C.; Sulley, S. The Mechanical Properties of Elastomers in High-Pressure CO 2. 1998.
4. Nimtz, M.; Klatt, M.; Wiese, B.; Kühn, M.; Joachim Krautz, H. Modelling of the CO2 Process- and Transport Chain in CCS Systems—Examination of Transport and Storage Processes. Geochemistry 2010, 70, 185–192, doi:10.1016/J.CHEMER.2010.05.011.
5. Schrittesser, B.; Pinter, G.; Schwarz, T.; Kadar, Z.; Nagy, T. Rapid Gas Decompression Performance of Elastomers – A Study of Influencing Testing Parameters. Procedia Structural Integrity 2016, 2, 1746–1754, doi:10.1016/J.PROSTR.2016.06.220.
6. Swelling of Elastomers in CO2 Environment: Testing Methodology and Experimental Data. | 10.2118/169277-Ms Available online: https://sci-hub.se/https://doi.org/10.2118/169277-MS (accessed on 26 June 2023).
7. Dubois, J.; Grau, E.; Tassaing, T.; Dumon, M. On the CO2 Sorption and Swelling of Elastomers by Supercritical CO2 as Studied by in Situ High Pressure FTIR Microscopy. J Supercrit Fluids 2018, 131, 150–156, doi:10.1016/J.SUPFLU.2017.09.003.