Effect of nano‐silica filler on the rheological and morphological properties of polypropylene/liquid‐crystalline polymer blends

Abstract

ABSTRACT:A fumed hydrophilic nano-silica-filled polypropylene (PP) composite was blended with a liquidcrystalline polymer (LCP; Rodrun LC5000). The preblended polymer blend was extruded through a capillary die; this was followed by a series of rheological and morphological characterizations. The viscosity of the PP matrix increased with the addition of the hydrophilic nano-silica. At shear rates between 50 and 200 s Ϫ1 , the composite displays marked shear-thinning characteristics. However, the incorporation of LC5000 in the PP composite eliminated the shear-thinning characteristic, which suggests that LC5000 destroyed the agglomerated nano-silica network in the PP matrix. Although the viscosity ratio of LCP/PP was reduced after the addition of nano-silica fillers, the LCP phases existed as droplets and ellipsoids. The nano-silicas were concentrated in the LC5000 phase, which hindered the formation of LCP fibers when processed at high shear deformation. We carried out surface modification of the hydrophilic nano-silica to investigate the effect of modified nano-silica (M-silica) on the morphology of the PP/LC5000 blend system. Ethanol was successfully grafted onto the nano-silica surface with a controlled grafting ratio. The viscosity was reduced for PP filled with ethanol-M-silica when compared to the system filled with untreated hydrophilic nano-silica. The LC5000 in the (PP/M-silica)/LC5000 blend existed mainly in the form of fibrils. At high shear rates (e.g., 3000 s Ϫ1 ), the LC5000 fibril network was formed at the skin region of the extrudates. The exclusion of nano-silica in the LC5000 phase and the increased viscosity of the matrix were responsible for the morphological changes of the LCP phase.

The influence of surface modification on the structure and properties of a nanosilica filled thermoplastic elastomer

“…Fumed nanosilica has been used as filler for thermoplastics as PP [1,5,23,31,36], LLDPE [37], PET [38], PEN [19], PES [10], and blends of PS/PP [23], PC/LCP [29], PP/LCP [24,26,30,35] and PP/EPDM [39]. Precipitated nanosilica has been mixed with PP [1,40], PBT [41], HDPE [6], propylene-ethylene copolymer [42] and isobutylene-based ionomer [43].…”

“…If dispersed to the scale of 10-50 nm, it can improve the heat distortion temperature, the modulus and the barrier properties of the matrix. Many research efforts have been devoted to the surface modification of silica [1,[3][4][5]14,24,34,35] leading to hydrophobic silica. The aim is to reduce the high surface energy and the particle interactions.…”

Polymer nanocomposite powders and melt spun fibers filled with silica nanoparticles

“…Only minor differences in the viscosities were found between pure PP and PP composites filled with ethanol-treated fumed silica. 25 The crystallization velocity of the iPP composite powders was determined by isothermal crystallization at 1308C after fast quenching of the samples from melt. All data were fitted according to the Avrami theory to determine the crystallization enthalpy and the (primary) crystallization order and kinetics.…”

Rheology of Polymer Blends

“…An exception is a study of the fumed hydrophilic silica effect on flow and morphology of PP blended with 20 wt% LCP using a capillary viscometer at c _ 50 5000 s 1 [370]. After addition of 5 wt% SiO 2 (primary particle size 12 nm) to PP the shear viscosity of the PP at lowc _ increased and became more shear thinning, suggesting formation of nanoparticle 3D aggregates.…”