Abstract
A liquid crystalline polyimide (poly[1, 3-bis[4-(4-aminophenoxy)-α, α-dimethylbenzyl]benzene pyromellitimide]: PI-LC) was blended with two kinds of thermoplastic polyimide: poly[3, 3′-(4, 4′-dioxybiphenyl)diphenylene pyromellitimide] (N-TPI) which is a semicrystalline polyimide having a melting point of 388 °C and poly[2, 2′-bis(3, 4-dicarboxyphenoxy)phenylpropane-2-phenylene bisimide] (PEI) which is an amorphous poly(etherimide) having a glass transition temperature at 220 °C. The miscibility of N-TPI and PI-LC was evaluated by DSC using enthalpy relaxation, and the phase diagram of their blend was drawn above the melting point of N-TPI. The result indicated that the PI-LC-rich blend was miscible in a wide range of compositions. However, the extruded samples of their blend, which had been prepared under a flow of high shear, showed 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 blend fibre showed higher tensile properties than the original PEI fibre.
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