Sorption thermodynamics and mutual diffusivity of carbon dioxide in molten polycaprolactone

Solution thermodynamics and mutual diffusivity of the system carbon dioxide-molten poly(epsilon-caprolactone) (PCL) have been investigated experimentally in the temperature range 70-85 degreesC and at pressures up to 6.5 MPa. Sorption data have been interpreted on the basis of Sanchez-Lacombe lattice theory. Sanchez-Lacombe parameters for pure PCL have been evaluated by fitting experimental pressure-volume-temperature data obtained by using a high-pressure dilatometer, while parameters for carbon dioxide have been taken from the literature. Information on the free volume of the mixture, as gathered from the solution thermodynamics analysis, has been used in the classical free-volume theory proposed by Duda and Vrentas to fit mutual diffusivity data, obtained from sorption kinetics experiments.