Morphology and mechanical performance of pregenerated and “in‐situ” PP/vectra B composites

Polypropylene/Vectra B blends were obtained at different LCP contents and barrel temperatures by an extrusion‐injection process. The wide barrel injection temperature range chosen, from 200 to 300°C, gave rise to blends in which the pregenerated extruded morphology was preserved, partially preserved, or lost. The blends processed at 260 and 300°C showed the usual morphology and properties of “in‐situ” composites. The blends injected at 240°C showed the worst properties because of their partially melted and agglomerated morphology. A barrel temperature of 200°C (80°C below the melt temperature of Vectra B) was needed to maintain the pregenerated fibers. These pregenerated composites, without post‐extrusion drawing, showed smaller modulus of elasticity and tensile strength than those of the “in‐situ” composites, but an increased notched impact strength as a consequence of their less perfectly oriented but more homogeneous morphology.