Introduction to the Third International Workshop on Long-Term Thermal Performance of Cellular Plastic Insulation

Methodology for the evaluation of long-term thermal performance of cellular plastics is being developed under a collaboration of North American foam industry with the National Research Council of Canada. The mechanism of this col laboration includes a joint research project between the Society of Plastics Industry and the NRC Canada. To evaluate long-term thermal performance (LTTP) of cellular plastics the aging process must be accelerated. This can be done either by means of elevated tempera ture or by the use of thin layers of the foam. The first approach changes the permeability and solubility coefficients of different gases to such a degree that pre dicting the foam performance under field conditions is difficult. Only the thin layer approach is used in the SPI/NRC project, though the relation between aging of thin layers and that of full board is treated differently, depending on the foam uniformity. When unfaced foam is homogenous enough to permit a sim ple arithmetic operation, known as the scaling technique, this relation can be used to calculate foam aging for layers with different thicknesses. When, however, the cel lular structures of skin and core layers differ significantly, or the foam is provided with impermeable facers, then the scaling technique is not appropriate and the aging models (models of heat and mass transfer) must be used There is, however, a number of material characteristics needed as the input to these models, and the manner in which these material characteristics are generated decides upon the scope of application of this methodology. Therefore, much of this research relates to the methods of material characterization. This presentation outlines the main elements of methodology developed under the SPI/NRC project and highlights future research needs.