Sorption measurements are executed to study the sorption behavior of propylene in a semicrystalline polymer. Decreasing values for the Flory-Huggins interaction parameter with increasing temperature are obtained. Large deviations are found, especially at higher temperatures, compared to data from the literature. Propylene is polymerized in liquid and gaseous propylenes with Me2Si[Ind](2)ZrCl2/MAO/SiO2 as the metallocene catalyst. Lower relative reaction rates are found in the gas phase compared to the experiments in the liquid phase. The activation energies from the experiments in both phases are on the same order of magnitude. However, the literature versus experimental sorption data has a large effect on the determined kinetic parameters.