A new route of emulsifier-free emulsion polymerization based on the homogenous mechanism was investigated to prepare magnetic nanoparticles coated by poly (methyl methacrylate) (PMMA). The experimental results confirm the formation of PMMA thin and unique layers covering magnetite cores. The polymer layer thickness, determined from transmission electron microscopy (TEM) images, increases from 4.3 nm to 6.8 nm with increasing mass ratio of MMA to magnetite from 3:1 to 11:1. The increase of the polymer thickness results in the decrease in magnetization saturation of polymeric coated magnetic particles. However, this reduction, no more than 13 emu g −1 , is much lower compared to that in other studies with the presence of surfactants or emulsifiers. Besides, the dispersion stability of the prepared particles is significantly improved.
Here we report on the modification of fly ash (FA) with vinyltriethoxysilane (VTES) in order to enhance the dispersibility and avoid the agglomeration. FA was treated with nitric acid before the modification with VTES. The structure of fly ash particles before and after the modification was characterized by several sophisticated techniques including Fourier transform infra-red spectrum (FT-IR), thermogravimetric analysis (TGA), field emission scanning electron microscopy (FE-SEM) and size distribution analysis. The obtained results show that the VTES was grafted successfully onto the surface of FA, which significantly changes the surface properties of FA. It was also found that the thermal stability of modified FA (MFA) is much higher than that of the FA treated only with nitric acid. The size of the FA particles can also be controlled from 0.2 to 1.5 µm with increasing the loading of VTES on the surface of FA from 1 to 2 wt.%, revealing highly mono-distribution and low agglomeration. However, the agglomeration of the particles is observed when the content of VTES on the surface of FA exceeds 2 wt.%.
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