Three-dimensional thermal aging and dimensional stability of cellular plastic insulation

The requirement of producing environmental-friendly plastic foam results in the replacement of the traditional blowing agents, CFCs (chlorofluorocarbons), with zero ozone depletion potential (ODP) alternatives. The tool which is able to evaluate the quality of the new generation of plastic foams becomes practically important. A 3-dimensional (3-D) heat and mass (gases) transfer model with respect to rigid closed-cell cellular plastics has been carefully deduced and furnished based on our previous understanding of such problems. To solve the 3-D parabolic partial differential equations subject to the third type of boundary conditions, a modified alternative direction implicit (ADI) finite difference method was developed by using the natural laws. To predict the long-term dimensional stability of a plastic foam insulation in air, a simplified mechanical model has been presented. In addition, to closure the prediction of foam dimensional stability, we have deduced a general relationship between the elastic modulus (Young's modulus) of a rigid closed-cell cellular plastic, Ef and its density, fp. In comparison to the published measurements and other two well-known Ef - fp models, it is found that our Ef - fp relationship gives better prediction and is valid over the entire rigid plastic foam density range. Thermal aging and average volume change of zero ODP foams with different facing will be addressed. In addition, the application of the model shows the effects of foam dimension and facing on its thermal aging and deformation.