writer：Jian-Shu Kang, Cai-li Yu, Fa-Ai Zhang
keywords：soap-free emulsion polymerization;SiO2;silane coupling agent;methyl methacrylate;hydroxyethyl methacrylate
source：期刊
specific source：Iranian Polymer Journal
Issue time：2009年

A commercial SiO2 powder was treated with three different silane coupling agents,
i.e., 3-aminopropyltriethoxysilane (KH-550), 3-glycidoxypropyltrimethoxysilane
(KH-560), and 3-methacryloxypropyltrimethoxysilane (KH-570), respectively.
The soap-free emulsion polymerization of methyl methacrylate (MMA) and
hydroxyethyl methacrylate (HEMA, as stabilizing agent) was carried out in the
presence of unmodified and modified SiO2 particles. The polymerization rate and
monomer conversion of this system were investigated. The structure, particle size and particle size distribution, morphology, surface tension, and ionic conductivity of the emulsion were determined by Fourier transform Infrared spectrometry (FTIR),
dynamic light scattering (DLS), scanning electron microscopy (SEM), transmission
electron microscopy (TEM), automatic interfacial tension and conductivity
measurements, respectively. The results showed that silane modified SiO2 particles increased the final monomer conversion, decreased the particle size, and narrowed the particle size distribution of the poly(MMA-HEMA)/SiO2 composite emulsion, in comparison to unmodified SiO2 particles. Although, the former somewhat depressed the polymerization rate at the early stage. The emulsion with KH-560 modified SiO2 particles achieved the highest monomer conversion, the lowest coagulum, the smallest particle size, the highest surface tension, and the maximum ionic conductively, while the emulsion with KH-550 modified SiO2 particles produced little more coagulum. By completion of polymerization process, the surface tension and ionic conductivity of the emulsion increased significantly and the aggregated SiO2 powder formed the primary particles. SEM morphological study on the emulsion demonstrated that the shapes of the particles are spherical and their sizes are in agreement with those of the dynamic light scattering measurement. TEM images confirmed that the SiO2 particles have been encapsulated inside the composite.