Flow behaviour and microstructure evolution in novel SiO₂/PP/LCP ternary composites: Effects of filler properties and mixing sequence

When silica (SiO₂) fillers were introduced into the polypropylene (PP) and liquid-crystalline polymer (LCP) blend, it was found that the mixing sequence, the filler size, and the filler surface nature affected the rheology of the composites and the morphology of the LCP phase in the ternary composite. In particular, the compatibility between the filler and the PP matrix was found to exert a strong influence on the droplet-fibril transition. The incorporation of the hydrophobic silica to the LCP/PP blend facilitated the fibrillation of LCP because the hydrophobic filler demonstrated affinity towards the hydrophobic PP matrix. The preferential residence of the hydrophobic silica in the PP phase would minimise the LCP domain disruption leading to the formation of LCP fibrils with high aspect ratios. The use of fine filler and in situ blending, which promoted the filler-LCP interaction, could prevent coalescence, inhibit deformation and hinder fibril development as well.