Effective Conductivity of Aging Polyurethane Foam

Abstract

An experimental technique was developed to measure the permeability of the cell walls to air components. Cell walls obtained from large bubbles were used as samples. The large bubbles are found on the surface of free rise foam. Once cell wall permeability and cell geometry are known, the foam effective diffusion coefficient can be computed from a model developed earlier. An experimental technique was also developed to measure the effective permeability of the foam. Data were taken with N/sub 2/, O/sub 2/ and CO/sub 2/ at different temperatures. The permeability of the three gases vary in the ratio 1:4:25, respectively. To determine if steady state gas partial pressure is reached in a sample, graphs similar to Heisler Charts were developed. To accelerate the data taking process special charts utilizing the analytical solution of the transient transfer process were made. These graphs enable data to be taken before the steady state profile is completely developed. Two simple laboratory tests were developed to measure the effectiveness of the diffusion barriers. A test cell was designed to measure the leakage rate through the open paths at the foam-foil interface. To be able to detect the open paths a simple dye technique was developed.more » It was found that most of the tested samples with foil on both sides have open paths at only one interface. On the other interface an open shear layer 1 to 2 mm below the interface was detected. « less

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