A Poly(vinyl acetate)/Colloidal SiO2 Nanocomposite Synthesized by Emulsion Polymerization and Study of Its Mechanical, Thermal and Rheological Properties

Effect of colloidal nanosilica (SiO2) on the mechanical, thermal and rheological properties of poly(vinyl acetate) synthesized by in situ emulsion polymerization method was investigated. For this purpose, a poly(vinyl acetate) latex containing 1.5 wt% colloidal silica nanoparticles was produced and the results were compared with of a blank sample. The effect of nanoparticles on the shear strength of a blank and modified poly(vinyl acetate) was characterized by tensile test. The effect of nanoparticles on glass transition temperature (Tg), thermal stability and char yield of pristine poly(vinyl acetate) and its nanocomposite was evaluated by differential scanning calorimetric (DSC) and thermogravimetric analysis (TGA), respectively. The rheological behavior of the products was studied by rheometric mechanical spectrometry (RMS). Eventually, field emission scanning electron microscopy (FE-SEM) coupled with elemental mapping of X-ray spectroscopy (EDX) was used to study the morphology and elemental analysis of the nanocomposite. The results showed that the shear strength was improved by 11% with increasing 1.5 wt% colloidal silica nanoparticles into poly(vinyl acetate). Besides, with the addition of silica nanoparticles, Tg increased approximately 1°C due to creating more free volume between the polymer chains. The TGA results showed that the nanocomposite char yield increased by 3.8% at 800°C in comparison with the blank polymer char yield, suggesting a thermal stability improvement in the presence of colloidal silica nanoparticles as a result of molecular interactions. The results of RMS revealed the shear thinning behavior of the latexes. The FE-SEM-EDX results showed a uniform dispersion of nanoparticles throughout the poly(vinyl acetate) matrix