A new class of material is now being developed for cryogenic thermal insulation systems for the next-generation reusable launch vehicles, commercial and defense marine ships, commercial aircraft, and numerous industrial applications. Recent advancements in high-temperature polymeric materials at the NASA Langley Research Center have led to the development of new polyimide foam systems with attractive properties for applications in thermal and acoustic insulation. To understand the performance parameters of these new foam systems at low temperatures and pressures, experimental studies are being conducted at the Cryogenics Test Laboratory. Liquid nitrogen cryostats developed by the Cryogenics Test Laboratory are being used to perform detailed thermal characterizations of these novel materials under full-range cryogenic vacuum conditions. Although common polymeric foams such as polyurethane have outstanding properties, they have been limited in their applications by temperature, poor fire resistance, and their susceptibility to thermal cycling and ultraviolet light exposure. These new high-performance foam systems of cyclic imide polymers have excellent structural integrity, fire resistance, thermal aging resistance, and thermal cycling properties.

In general, thermal conductivity of foamed systems is the lowest of any solid materials and is determined by the gaseous conduction within the pores, conduction via the solid structure of the foam, convection through the cells, and radiative heat transfer. This research allows for all of these parameters to be studied, including density, surface area, and open- or closed-cell content effects. In closed-cell foams, the heat transfer coefficient in the cell will change as the blowing agent is replaced by air with time. In open-cell foams, the overall thermal conductivity of the system will increase because of the open transfer of air into the cells through convection. This pioneering work involves never-before-investigated parameters for these foam systems and has led to important technology development for the NASA Space Launch Initiative/2nd Generation Launch Vehicles Program. The research and development are now being extended for the future utilization of novel polyimide composite materials in both aerospace launch systems and a number of industrial cryogenic equipment applications.