The Effective Diffusivity of Cyclopentane and n-Pentane in PU and PUIR Foams by Thin-Slice Gravimetric Analysis

Abstract

Monitoring thermal conductivity changes in thin-sliced cellular plastics has drastically reduced the time required to evaluate the long-term aging of insulating foams. Monitoring the weight changes of closed-cell thin-slices provides data which can be analyzed to determine the effective diffusivity of atmospheric and blowing agent gas components. The effective diffusivity of atmospheric gases are about two orders of magnitude larger than that of permanent insulating blowing agents. This large difference in effective diffusivity allows each gas to be determined independently. Specimens of polyurethane (PU) and polyurethane modified polyisocyanurate (PUIR) foam were prepared using cyclopentane or n-pentane in the PUIR foams.