Effect of the type of nano-filler on the crystallization and mechanical properties of syndiotactic polystyrene based nanocomposites

In this research, syndiotactic polystyrene based nanocomposites containing 3 wt% of nanofiller were prepared using the melt-mixing technique. Nano-fillers used included multi-wall carbon nanotubes, silver nanoparticles, nanodiamonds and copper-nanofibers. The latter were prepared especially for this use. Prior to melt mixing, polymer and nanoparticles were ball-milled to form a physical mixture. TEM and SEM micrographs verified a fine dispersion of the nanoparticles in the polymeric matrix. Formation of nano-filler aggregates was very limited. Tensile testing showed slight improvement of the mechanical properties of the nanocomposites compared to the neat sPS. From the WAXD patterns, existence of mixture of crystals mainly of α and β crystal types of sPS was evidenced. In general, crystals of α-type dominated, except in case of the sPS/MWCNT nanocomposite in which mainly β-type crystals appeared. Isothermal and non-isothermal crystallization studies showed that the presence of nano-filler caused enhancement of crystallization rates and that the most effective nucleation was achieved using MWCNT. These results were further reinforced by estimating the effective activation energy of non-isothermal crystallization using the isoconversional method of Friedman as well as the nucleation activity of the filler.