Structure and properties of amorphous polyamide/liquid crystalline polyester blends

Amorphous polyamide (AP) /liquid crystalline polyester (VA) blends were obtained by extrusion-injection molding (EI) throughout the whole composition range. The phase behavior, chemical nature and morphology,of the blends were studied, and the mechanical properties discussed and compared with those of the 10 and 30% VA blends obtained by direct injection molding (DI). The blends showed two almost pure slightly reacted amorphous phases. The apparently higher reaction level of the EI blends, although small, led to a more homogeneous, fine and fibrillated morphology, attributed to a lower interfacial tension. Significant synergisms in the modulus of elasticity (up to 25%) and in the tensile strength (up to 40%) were seen in El blends. The similar values of both specific volume and orientation in the blends and in the pure components suggest that the contribution to the modulus of the dispersed VA rigid particles is greater than that due to the proportion of VA in the blend. The 10% VA DI blend showed a similar behavior in these two properties, indicating that the DI procedure is preferred, provided that only stress-related properties are sought. At 30% VA content, the moduli of elasticity were similar by the two molding processes, but the clearly lower tensile strength and lower ductility of the easier DI procedure, means that the more complex, but more effective, El procedure is the one of choice for high performance materials.