Effects of ultrasound on the morphology and properties of propylene-based plastomer/nanosilica composites

Abstract

Propylene-based plastomer/nanosilica composites, with a filler content of 1–4 wt%, were prepared by a specially designed ultrasound-assisted extrusion system that was developed in our laboratory. The effects of ultrasound on the morphology, as well as the rheological and mechanical properties of the composites, were studied in this paper. In spite of slight ultrasound-induced degradation of the polymeric matrix, the results showed that the strength and elongation of the composites at break, in most cases, still improve in the presence of ultrasound because of ultrasound-induced homogeneous dispersion of nanoparticles in the polymeric matrix (as confirmed by scanning electron microscope, transmission electron microscope and differential scanning calorimetry studies). Dynamic rheological measurements also indicate that ultrasound-induced compatibilization has a more predominant role than does degradation. From dynamic mechanical measurements, it was found that ultrasound-induced degradation results in a drop in the dynamic storage modulus and glass transition temperature for composites with 4 wt% filler content, whereas ultrasound-induced compatibilization enhances their loss factor values. By the presence of 100 W ultrasound during extrusion, SiO2 nanoparticles become smaller and their aggregations disappear, indicating that more homogeneous dispersion of SiO2 nanoparticles into propylene-based copolymer matrix is achieved.