Synthesis of high solid content polyacrylate/nanosilica latexes via miniemulsion polymerization

High solid content nanocomposites based on poly(methyl methacrylate-co- butyl acrylate)/nanosilica was synthesized via miniemulsion polymerization in a semi-continuous operation. Oleic acid was used to act as a coupling agent between silica surfaces and polymer. Latexes with solid content of 42% were obtained, containing 5% by weight nano-SiO2 with respect to polymer. FTIR Results show the modified structure of silica with oleic acid and confirm the presence and bonding of modified silica on the polymer structure. Morphological investigations were performed using TEM analysis. The results of microscopic images confirm the nanocomposite structure where the nanoparticles of silica are coated with the polymer nanolayers. Thermal analysis including DSC and TG/DTA was used to investigate Tg, thermal stability and thermal decomposition of the sAmples. The nanocomposite latex is compared with the neat latex of the same monomer structure. The results of DTA analysis show an increase of about 8°C in the degradation temperature. DSC Analysis shows that the glass transition temperature of the nanocomposite is higher than that of pure acrylic latex. Moreover, the samples with improved hardness are compared with blank latex sample. All analyses demonstrate the well located silica nanoparticles inside the latex polymeric structure.