By applying different NMR methods, the penetration of polymers (FPM, EPDM, HNBR) by partly fluorinated hydrocarbons (HFC) has been investigated and characterized. NMR proved to be capable in delivering qualitative as well as quantitative information about the fluid in the polymer sample. The concentration, as well as the diffusion coefficient of the HFC in the polymer, has been determined. Localized methods furthermore allow a characterization of the swelling of the polymer on the macroscopic scale. The penetration and swelling kinetics can be determined. Probe molecules help to obtain information on the microscopic scale.