A STUDY OF CRYSTALLINE TRANSITIONS IN A THERMOPLASTIC POLYIMIDE

A new polyimide derived from 4,4'-isophthaloyldiphthalic anhydride (IDPA) and 1,3-bis(4-aminophenoxy-4'-benzoyl) benzene (1,3-BABB) having semicrystalline behavior was prepared at NASA Langley Research Center in 1987. The crystalline transitions of this thermoplastic polyimide have been studied. The differential scanning calorimetry (DSC) pattern of partially imidized film exhibited two distinct crystalline melt endotherms. For this study each crystalline phase was isolated and enhanced by controlled thermal treatment. A film containing approximately 50% of both phases and an amorphous film were also prepared. Evaluations of these films were performed by DSC, wide-angle x-ray scattering (WAXS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Three distinct crystalline morphologies; ellipsoid, cubic, and needlelike embedded in an amorphous matrix were observed as a function of various cure conditions by SEM.