Rheological implications of fiber formation and breakup in a PP/LCP blend

Rheological results correlated with morphological changes of blends of polypropylene (PP) with a thermotropic LCP (Rodrun 5000) are presented. The study of the break up of Rodrun 5000 fibers in the PP matrix allows us to determine the interfacial tension, alpha=10mN/m. An analysis of fiber formation and break up leads us to assume the following morphological evolution, which is confirmed by SEM results: I) LCP fibers on PP matrix are formed at the entrance of the die. II) This morphology is maintained during shear flow inside the die. III) LCP fibers transform into droplets in the melt state, during the slow cooling process at the exit. The rheological repercussions of these results are: a minimum in the viscosity-coin position curves and the output of extrudates with an emulsion-like morphology.