MECHANICAL AND MORPHOLOGICAL PHASE-BEHAVIOR IN MISCIBLE POLYETHERSULFONE AND POLYIMIDE BLENDS

Phase behavior in the blends of polyimide (PI; Matrimid 5218) which is a condensation product of 3,3',4,4'-benzophenonetetracarboxylic dianhydride and 5(6)-amino-1-(4-aminophenyl)-1,3,3'-trimethylidone and polyethersulfone [PES; poly(sulfone bis(p-phenyl)oxide)] has been investigated by differential scanning calorimetry (DSC), tensile test, scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). Miscibility was obtained from an optically transparent film and a composition dependent single glass transition temperature (T(g)) using DSC. Thermally induced phase diagram indicated LCST (lower critical solution temperature) type behavior. TGA measurement showed an increment in thermal stability and in weight retention in miscible blends. In mechanical measurement, the homogeneous 50/50 wt% blend showed the highest strain at break, yield stress and modulus, however these values were dramatically reduced after phase separation. Phase morphology was also observed by comparison to the domain growth in thermally induced phase separation using SEM and thereby this is a good agreement with the DSC and mechanical behavior.