Diffusion coefficients of polyurethane coatings by swelling experiments using dielectric spectroscopy

The present work describes the use of dielectric analysis (DEA) for comparison of swelling kinetics of two polyurethane coating recipes, R1702 and R1703, with varied hardener amount by swelling in ethanol. For this purpose, a rapid swelling test, simulating a cleaning process of coated polymer housings, was created and the diffusion coefficients of different coating compositions were calculated. These diffusion coefficients were compared with diffusion coefficients determined from the classical swelling experiment. Besides this, the internal comparison of swelling kinetics after repeated exposure of coatings to ethanol was made. Subsequently, the coating compositions with the most resistant against swelling were determined. For the fitting of desorption curves, received from DEA measurements, a fit function based on the solution of the second Fick´s law and Doolittle like equation was used. The DEA can be successfully used for comparison of desorption processes in polyurethane coatings and for the calculation of diffusion coefficients.