Determination of Effective Diffusion Coefficients in Rigid Polyurethane Foam

The change in cell gas pressures over time in foam slabs and cylindrical foam samples was determined, and the effective diffusion coefficients of the gases were calculated. Seven different rigid polyurethane foams, blown with pentane or cyclopentane, were used. No systematic difference between the effective diffusion coefficients obtained from slabs and cylinders could be seen. The results were of the same order of magnitude as the values found in the literature. A discussion on time and sampling restrictions when measuring effective diffusion coefficients is presented along with recommendations on sample geometries and dimensions when evaluating diffusion of different gases. The thermal conductivity of the foams, calculated from the obtained effective diffusion coefficients, agreed well with the measured values of the thermal conductivity.