engleski

Comparison of the effects of sillica and wollastonite fillers in binary polypropylene composites

Incorporation of fillers in polymer matrix is a rather simple way to produce new polymer material with tailored properties. The effects of sillica and wollastonite fillers on the morphology, orientation and mechanical properties of binary polypropylene (PP) composites were studied with optical and electron microscopy (SEM), and tensile and impact strength measurements. Optical microscopy and SEM revealed the formation of well homogenized binary composites with wollastonite and sillica homogeneously dispersed in PP matrix. Small amounts of both of fillers incorporated in the PP matrix decreased the spherulite size by nucleation effect. Higher disturbance of spherulitic morphology with increasing amounts of acicular wollastonite than spherical sillica particles indicated the additional steric hindrance effect of particles. Moreover, PP matrix with hydrophobic silica particles exhibited better spherulitization than this one with hydrophilic silica particles. Incorporated needle-like wollastonite particles were orientated plane-parallel to the sample surface, while microsilica particles with nearly spherical shapes reasonable did not exhibit orientation effect. Mechanical properties of the PP composites were significantly influenced by incorporation of silica and wollastonite fillers. Whereas Young's modulus increased, elongation at yield and break, tensile strength at yield and impact strength decreased in both composite systems. Significant difference in mechanical behavior of these two composite systems was observed in tensile strength at break, where break value decreased with incorporation of wollastonite, while it increased with incorporation of silica. There was a slight difference in tensile strength at break between composites with hydrophylic and hydrophobic silica particles. It seems that the difference beetween different surface treatment has more profound effect on morphology and mechanical properties of silica composites. It could be concluded that changes in supermolecular structure of binary PP/sillica and PP/wollastonite composites had strong influence on mechanical properties of those composites.

polypropilene; silica; wollastonite; polymer composites

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