Physical properties of isotactic poly(propylene)/silver nanocomposites: Dynamic crystallization behavior and resultant morphology

The presence of silver nanoparticles (0.01-5 wt.-%) increased the crystallization temperature of isotactic poly(propylene) (iPP) (e.g., a 5 wt.-% content increases the temperature by ca. 7°C) and produced a sharper crystalline peak. It had little effect on the melt rheology of the nanocomposites. The shear-induced crystallization behavior of iPP was accelerated with increasing Ag content and imposed frequency. In addition, the promoting effect of Ag nanoparticles on the overall crystallization behavior was more notable at 140°C than at 130°C. The wide-angle X-ray diffraction scans of iPP nanocomposites with 5 wt.-% Ag crystallized at 130°C clearly presented another peak at a 2θ value of 15.8°, which corresponded to a β-form crystal. The nanocomposites with 5 wt-% Ag crystallized at 130°C gave double melting peaks at 154 and 166°C. On the other hand, the samples crystallized at 140°C produced two melting peaks at 166 and 172°C. The introduction of as much as 0.1 wt-% of Ag nanoparticles increased both the tensile strength and elongation at break, but subsequent further addition caused a decrease. In addition, iPP nanocomposites with more than 1 wt-% Ag exhibited a higher modulus than pure iPP.