engleski

Influence of filler properties on polypropylene/silica composites behavior

The influence of different silica grades on the properties of binary polypropylene (PP)/silica composites were investigated by optical and SEM microscopy, wide-angle X-ray diffraction (WAXD) and by measurements of tensile properties. The polypropylene (PP)/silica composites of 92/8 volume content ratio were prepared from melt by compression moulding. The effects of different silica grades, particle size (nanosilica vs. microsilica) and surface treatment (untreated surface or hydrophilic vs. treated surface or hydrophobic silica), on phase morphology and mechanical properties of the PP/silica composites were compared. The results revealed the formation of well-homogenized PP composites without substantial agglomeration of filler even in the PP composites with nanosilica particles. Polarization micrographs revealed uniform morphology of PP matrix showing grains, irregular or well-developed spherulites. Whereas the impact strength and yield characteristics of all samples were similar, tensile properties at break exhibited differences between the composites with hydrophilic and hydrophobic silica. Hydrophobic micro- and nanosilicas enabled better spherulitization of PP matrix enhancing thus elongation and decreasing the strength at break. It seems that these differences arose from the influence of various silica grades on the crystallization of the PP matrix.

composite; polypropylene; silica

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