Mass transfer and phase equilibria phenomena are important both in the formation and utilization of polymeric foams, particularly for insulating materials. The Center's high pressure capabilities have been used to measure the solubility and diffusion of blowing agents in molten polymers at the high pressures characteristic of extruding operations. The Center has also been a leader in examining the release of blowing agents from insulating foams produced from polystyrene, polyurethane, and other polyolefins. A unique experimental technique has been developed to measure the diffusion of blowing agents in glassy polymers such as polystyrene and polyurethane at ambient conditions where the diffusion coefficient is very small. Basic solubility and diffusivity measurements have been coupled to predict migration out of polymer foams and the drift in the experimental insulating properties of these foams.