Influence of high spressures on CH4, CO2 and H2S solubility in polyethylene: Experimental and molecular simulation approaches for pure gas and gas mixtures. Modelling of the sorption isotherms

International audienceThe sorption of methane, carbon dioxide and hydrogen sulphide in polyethylene (PE) was investigated. Data were obtained in a large range of pressures from both experiments and molecular simulation. Monte Carlo (MC) simulations in the osmotic ensemble were used to predict gas concentrations in the amorphous polymer phase. An ad hoc constraint in the osmotic simulations was used to mimic the effect of the crystalline phase. The results obtained from MC simulation compared favourably to experimental results and data from literature. Different sorption mechanisms were evidenced in the low to middle gas pressure range as a function of the gas nature. However, the decrease of gas solubility was evidenced at high pressure. It was assigned to a hydrostatic effect and the bulk modulus of the PE amorphous phase was determined. A simple model allowing the accurate description of gas solubility from low to high gas pressure range was proposed. It was shown to accurately describe the different sorption isotherm shapes obtained for PE and the characteristic parameters of the model were determined for each gas