Preparation Of PMMA/SiO₂ Composite Particles Via Emulsion Polymerization And The Scaling Up Of The Polymerization Process

Polymer/inorganic composite is a new material, which combined the properties of polymer and inorganic particle, overcome the shortages of inorganic particles, such as machining difficultly, and of polymer, such as low strength and low stability. This type of composite material can obtain new properties synergistically derived from polymer and inorganic particles. Therefore it has become one focus of researches. In this paper, PMMA/SiO2 composite particles were prepared via emulsion polymerization and characterized by means of FTIR, TGA, TEM and diameter analysis etc. The recipe and polymerization techniques were optimized and the scaling up of the process was investigated primarily.The results of FTIR and TGA show that the molecule of PMMA is grafted onto the surface of silica and the highest percentage of grafting is about 54%. The results of TEM and diameter analysis indicate that after the PMMA molecules were grafted onto the surface of silica, the dispersion of particles became better, exhibiting as the dimension of the dispersion phase is smaller than that of silica. The ratio of MMA/ SiO2, the amount of surfactant, as well as the kind and the amount of initiator have important influence on the polymerization process, the structure and the property of the obtained composite particles. The recipe and polymerization techniques were optimized through investigation of amount of gel, percentage of grafting, efficiency of grafting and the yield of polymerization. The results show that when VCA/(SiO2+VCA) is1~5%, SiO2/(MMA+SiO2) is9-18%, SDS/(SDS+H2O) is 1-3%, KPS/(KPS+MMA) is 1-2%, polymerization temperature is about 80℃, the polymerization process is stable, the amount of gel is low, the percentage of grafting and yield of polymerization are relative high, which can reach 54% and 97% respectively.The type and fixing palace of the impeller were determined in model reactor according to the experimental. The results show that when three-blade backswept impeller was used and Hb/HL is 1/4, the effect of stir is the best, where Hb is height of impeller from the bottom of the reactor and the HL is the height of the liquid. The parameters of three-blade backswept impeller are that D/T is 0.5~0.66, B/D 0.16, upward bending angle a 15?, backswept angle 3 30 , Np/NQd 4.5. The impeller has excellent shear and good blending ability. On the basis of the optimized recipe and techniques, the engineering enlargement of the process was investigated primarily. For the 0.8L, 10L, 40L and 500L reactor, the polymerization kinetics, percentage of grafting and the morphology of the obtained composite particles were investigated by means of weight analysis, TGA and TEM. The results show that the structure and properties of the composite in model reactor can be recurred in enlarged reactor.Through the research of this paper, one method of preparation of polymer/inorganic composite particle via emulsion polymerization is obtained. And the interaction between polymer and inorganic particles is chemical interaction, whose force is strong and can prevent the inorganic particles separating out from polymer. The polymerization process was enlarged successfully in the scale of 500L, which establish firm basis for further industrialization.