Abstract
The use of some alternative blowing agents from conventional CFC's and the quality of foamy processes can lead to non-homogeneity of foam structure with presence of defects along the panel thickness. These defects appear as holes in cell windows or cavities. Accurate measurements of thermal conductivity were made on test specimens having different thicknesses obtained by cutting away the external faces of the production panels.
This type of characterisation of foams blown with alternative blowing agents allowed us to understand their ageing behaviour (natural and accelerated) and the problems related to the scaling factor. Moreover this study pointed out how the effective diffusion coefficients of gases involved in the ageing process can have different values along the thickness of a sample. All these observations were connected with morphological analyses and radiant conductivity data.
Our studies showed that sampling procedure and design of models are very important for a correct analysis of ageing phenomena. Good fit between experimental and theoretical data was found, allowing us to verify the validity of the method used to characterise non-homogeneous foams.
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