FABRICATION AND CHARACTERIZATION OF HIGH PERFORMANCE THERMOSET POLYIMIDE FOAMS

摘要

Polymer foams offer numerous advantages compared to solid polymers. There are multiple methods of fabricating foams from polymers. Solid state foaming is an innovative technique of foaming microcellular thermoplastics which bypasses melt processing. This study aims at fabricating foams from new formulations of thermoset polyimides which find applications in the aerospace industry. RTM 370, a thermoset polyimide supplied by NASA Glenn Research Center, was used in this study. The samples were injection molded; saturated with pressurized carbon dioxide and subsequently foamed using a hot plate technique. The injection molded samples were brittle in nature because of processing at temperatures below the curing temperature. An alternate technique of sample preparation has been adopted wherein the polyimide is partially cross linked in a furnace to eliminate brittleness before saturating and foaming the samples. The micro structure of the foam was analyzed using scanning electron microscopy (SEM). It is found that microcellular porous structure could be obtained using the partially cross-linked samples. However, maintaining the porous structure in the curing process remained a challenge.