Effect of surface coating on the rheological properties of a highly opaque nano-TiO2/HIPS composite

The focus of this study is to investigate the influence of the interface bonding on the rheological behavior of the nano-sized titanium dioxide (nano-TiO2)/high impact polystyrene (HIPS) composite. The surfaces of nano-TiO2 used as the reinforced phase were first coated with polystyrene by in-situ emulsion polymerization. Thereafter, the nano-TiO2/HIPS composite was prepared by melt compounding. The results from the measurements of field emission-scanning electron microscope (FE-SEM) and ultraviolet-visible (UV–Vis) spectrophotometer confirmed high opaqueness and greatly improved interface adhesion between fillers and the matrix. The introduction of surface-coated particles remarkably increases the shear viscosity of the composite melts in the low shear rate region due to the strong interfacial interaction. For instance, at the shear rate of 0.02 s− 1, 25 wt.% nano-TiO2 increases the shear viscosity by 111.4% related to pure HIPS melts. Furthermore, compared with the uncoated nano-TiO2/HIPS composite, the composite containing surface-coated nano-TiO2 exhibits a measurable shear-thinning property.