Modelling the effect of morphology on thermal aging of low-density closed-cell PU foams

Abstract

Low-density closed-cell polyurethane (PU) foams are widely used in thermal insulation in diverse applications, therefore predicting their thermal aging has a distinct practical importance. Several approaches have been developed allowing forecasting the long-term changes of gas composition in foams, which manifest as the thermal aging. The accelerated aging test methods of foams need to be applied to each foam morphology of interest, while diffusion modelling-based methods, employing characterisation of the gas transport properties of PU polymer or monitoring the evolution of gas composition in foam cells, are relatively complicated. In this study, the experimentally determined evolution of PU foam conductivity is used for estimating the effective diffusivities of gases, based on which permeability of the PU polymer is subsequently evaluated by a structural model assuming Kelvin cell geometry of foam cells. The proposed approach enables prediction of aging dynamics of foams developed from the same PU polymer but possessing a markedly different morphology.