Fj. Vallejo et al., Morphology and mechanical performance of pregenerated and "in-situ" PP/Vectra B composites, POLYM ENG S, 39(9), 1999, pp. 1726-1735
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.