Morphology and mechanical performance of pregenerated and "in-situ" PP/Vectra B composites

Polypropylene/Vectra B blends were obtained at different LCP contents and b arrel temperatures by an extrusion-injection process. The wide barrel injec tion temperature range chosen, from 200 to 300 degrees C, gave rise to blen ds in which the pregenerated extruded morphology was preserved, partially p reserved, or lost. The blends processed at 260 and 300 degrees C showed the usual morphology and properties of "in-situ" composites. The blends inject ed at 240 degrees C showed the worst properties because of their partially melted and agglomerated morphology. A barrel temperature of 200 degrees C ( 80 degrees C below the melt temperature of Vectra B) was needed to maintain the pregenerated fibers. These pregenerated composites, without post-extru sion drawing, showed smaller modulus of elasticity and tensile strength tha n those of the "in-situ" composites, but an increased notched impact streng th as a consequence of their less perfectly oriented but more homogeneous m orphology.