Effect of Pressure and Temperature on the Sorption of Gases by Fluoroelastomers

Fluoroelastomers (FKMs) are widely used in high-pressure and high-temperature environments in the oil and gas industry. However, gas sorption at high pressure and high temperature in FKMs still remains unclear. Understanding the gas sorption process in FKMs at high pressure and temperature will help in the prevention of failure due to rapid gas decompression. In this work, we investigated primarily the effect of pressure (up to 15,000 kPa) and temperature (up to 125 degrees C) on CO2 and N2 gas sorption in FKMs. The isothermal solubility of the gases increases linearly with an increase in pressure in accordance with Henry ' s law. The pressure dependence of solubility is much stronger for CO2 compared to N2. The kinetics of sorption for both the gases was modeled and analyzed. CO2 gas sorption showed higher activation energy (9.8 +/- 1.0 kJ/mol) compared to N2 gas sorption (1.1 +/- 0.1 kJ/mol) at 3000 kPa. In addition, the effect of pressure and temperature on the diffusivity and permeability of gases in FKMs has been quantitatively interpreted. The solubility and diffusivity of CO2 gas decreased from 50.3 mggas/gpolymer and 8.4 x 10-7 cm2/s to 35.6 mggas/gpolymer and 7.2 x 10-7 cm2/s with increasing loading of carbon black up to 40 wt % at 50 degrees C, respectively. The results were compared with a practical FKM composition.