MISCIBILITY, MORPHOLOGY AND TENSILE PROPERTIES OF THE MELT BLENDS OF LIQUID-CRYSTALLINE POLYIMIDE (PI-LC) WITH 2 DIFFERENT THERMOPLASTIC POLYIMIDES - SEMICRYSTALLINE POLYIMIDE (N-TPI) AND AMORPHOUS POLY(ETHER-IMIDE) (PEI)

A liquid crystalline polyimide bis[4-(4-aminophenoxy)-alpha,alpha-dime thylbenzyl] benzene pyromellitimide]: PI-LC) was blended with two kind s of thermoplastic polyimide: poly[3,3'-(4,4'-dioxybiphenyl)diphenylen e pyromellitimide] (N-TPI) which is a semicrystalline polyimide having a melting point of 388 degrees C and bis(3,4-dicarboxyphenoxy)phenylp ropane-2-phenylene bisimide] (PEI) which is an amorphous poly(etherimi de) having a glass transition temperature at 220 degrees C. The miscib ility of N-TPI and PI-LC was evaluated by DSC using enthalpy relaxatio n, and the phase diagram of their blend was drawn above the melting po int of N-TPI. The result indicated that the PI-LC-rich blend was misci ble in a wide range of compositions. However, the extruded samples of their blend, which had been prepared under a flow of high shear, showe d a phase separation structure. In the other combination of PEI and PI -LC, the blend was immiscible, but at low composition of PI-LC their b lend fibre showed higher tensile properties than the original PEI fibr e.