Acrylic emulsifier-free emulsion polymerization containing hydrophilic hydroxyl monomer in the presence or absence of nano-SiO2

The acrylic emulsifier-free emulsion polymerization containing hydrophilic hydroxyl monomer (23 wt.%) in the presence or absence of nano-SiO2 particles was studied. The effects of reaction temperature, level of nano-SiO2, variation of core monomer composite on the coagulum, particle size and monomer conversion were investigated. Transmission electron microscopy (TEM) was used to observe the particle morphology in the presence of nano-SiO2 particles. It showed that the systems produced larger size of particles than that with emulsifier, and the addition of nano-SiO2 particles increased the particle size but decreased the coagulum. When polymerization temperature rose from 65 °C to 80 °C, the coagulum produced decreased greatly irrelative of the existence of nano-SiO2, and the particle size decreased with nano-SiO2 but increased without nano-SiO2. The increase of level of acrylic acid (AA) and 2-hydroxyethyl methacrylate (HEMA) in core monomer composite all decreased particle sizes; furthermore, the level of AA had more efficiency than the level of HEMA irrespective of the existence of nano-SiO2 particle.