The authors present a 3D gaseous transfer model and a simplified mechanical model. Thermal ageing and average volume change of ozone depletion potential foams with different facings are addressed. A formula has been suggested to correlate the elastic modulus and the reduced density of rigid foams over the whole foam density range.
Fan, Y., & Kokko, E. (1997). Three-dimensional gaseous transfer within cellular plastic insulation and its consequences. Building Research and Information, 25(1), 25-35. https://doi.org/10.1080/096132197370589