Solubilities and diffusion coefficients of carbon dioxide and nitrogen in poly(methyl methacrylate) at high temperatures and pressures

Abstract

The solubilities and diffusion coefficients of carbon dioxide (CO2) and nitrogen (N2) in poly(methyl methacrylate) (PMMA) were studied at temperatures of 373 K–473 K and pressures of up to 20 MPa. The solubilities and diffusivities were measured by the gravimetric method using a magnetic suspension balance. The dissolution of CO2 and N2 in PMMA obeyed Henry’s law, with the solubilities of the two gases exhibiting different temperature dependences. Further, the solubility data could be fitted using the Sanchez–Lacombe equation of state. The Henry’s constants for the dissolution of the gases in PMMA indicated that their temperature dependences were similar to those of the gases in polystyrene. Finally, the diffusion coefficients of CO2 and N2 with model analysis suggested that, for both gases, the solubility has a determining effect on the diffusivity. The diffusion coefficients of both gases could be described using the free volume theory.