Aging of Polyurethane Foams, the Influence of Gas Diffusion on Thermal Conductivity

摘要

it was shown that gas diffusion in closed-cell foams is driven by partial pressure only and not by temperature gradient. The value of the foam effective thermal conductivity can be predicted rapidly and accurately by the developed ECVA code, when the diffusion coefficients of N sub 2 , O sub 2 , CO sub 2 and fluorocarbon 11 are known. The code can predict the aging rate in different thermal environments. The effective diffusion coefficient can be obtained with sufficient accuracy from the analytical or electrical model, or can be measured directly by the rapid steady state technique. It was found that porous layers exists at the foam/facing interface and inside of the foam panels. By eliminating these layers, the aging performance of the foam can be substantially improved.