The Study Of Silica Modified By CPAM/Polyacrylate Hybrid Emulsion

Water-based paint attracts more and more attention with growing demand of environmental protection and human health. Because of excellent performance of SiO2/Polyacrylate hybrid emulsion, water-based coatings prepared by it would be expected to replace kinds of solvent coatings. However, during the preparation of SiO2/polyacrylate hybrid emulsion, the nano-silica particles always commit bad effect with getting together and retarding radical polymerization by silicon-hydroxy.In order to solve the above problems, firstly, cationic polyacrylamide(CPAM) was used to modify alkaline silica sol in our research. Results show that CPAM molecular chains, which have positive charges and hydrophilic groups, were adsorbed to the surface of silica particles by the electrostatic force and hydrogen bonding. The adsorption of cationic polyacrylamide resulted in more positive charges on silica surface and high Zeta potential of silica. Well modified silica sol with smallest silica particles size and highest Zeta potential could be made by using 0.25% cationic polyacrylamide water solution at 75 ℃ for 4 h.The SiO2/polyacrylate hybrid emulsion was prepared by emulsion polymerization with the modified silica sol and other stocks. Hybrid latex particles was formed in the way of electrostatic adsorption between silica particles and polymer, which had a polymer core and nano inorganic particles shell. When the silica content was more than 25% in the hybrid emulsion, the performance of film was level 0 of adhesion, flexibility to 3 mm, and hardness performing 5 H. Two kinds of functional monomers, A and B, were also used to improve adhesion and flexibility of the film.