Abstract
We have investigated the compressive stress-strain properties, and long-term compression set properties of highly crosslinked, rigid, polyurethane foams ranging in density from 100 kg m-3 to 810 kg nr-3. Samples were maintained under a range of compressive strains for periods ranging from three days to one year, and their dimensional recovery followed after release.
The compressive strength and moduli of the samples were found to vary as the square of the foam density. The compression set study revealed that recovery of all samples following release occurs in two stages, with very different rates, which we believe to he associated with the independent recovery of the polymer molecules and the cellular structure of the foam. The results also show that the long-term recovery from compression demonstrated by a particular sample is largely independent of sample density, and only slightly dependent on the time period of constraint, but mainly influenced by the degree of deformation during the confinement period.