Journal
INTERNATIONAL COMMUNICATIONS IN HEAT AND MASS TRANSFER
Volume 139, Issue -, Pages -Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.icheatmasstransfer.2022.106432
Keywords
Foams; Polyurethane; Thermal aging; Effective diffusivity; Kelvin cell
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Funding
- Latvian Council of Science of the project Elimination of Rigid PU Foam Thermal Insulation Shortcomings by Determining and Adjusting the Factors Influencing Gas Permeability of Polymer Matrix (PURGE) [lzp-2019/1-0354]
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This study proposes a method to estimate the diffusivity of gases by experimentally determined evolution of PU foam conductivity, and evaluates the permeability of PU polymer further. This method has the ability to predict the aging dynamics of PU foams with different morphologies.
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.
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