Study On Controllable Nucleation Of Emulsion Polymerization Of Methyl Methacrylat

This paper focused on the emulsion polymerization system consisting essentially of sodium dodecyl sulfate(SDS),methyl methacrylate(MMA)and potassium persulfate solution(KPS),systematically studied when the emulsifier concentration near CMC and below,the evolution of the characteristics and laws of the MMA latex particles in the nucleation stage and the chain growth reaction stages,respectively from three main aspects including of the emulsifier concentration,monomer concentration and monomer feed rate and emulsifier coverage.By measuring the conversion of MMA,particle dispersion index(PdI),particle size(PS),the particle size distribution(PSD),the number of latex particle per unit volume of(Np),the concentration of polymer(Cp),solid content and viscosity properties variation with reaction time,we established the quantitative relationship between these properties and the nucleation mechanism as well as chain growth process of MMA latex particles,we also established the relationships between the parameters and the reaction process.Based on these ralationships,the method to control the preparation of monodisperse MMA polymer emulsion was established.The main results of this paper are as follows:1.The particle nucleation modes between the system of SDS and MMA emulsion and SDS and St emulsion are essentially different.Which,SDS and MMA emulsion system mainly contains of flocculation nuleation and micellar nuleation,whereas SDS and St emulsion system contains of precipitation nuleation and micellar nuleation.2.The emulsifier concentration is the primary factor to control particle nucleation modes.The proportion of MMA’s flocculation and micellar nucleation in the total nuleation can be effectively adjusted by changing emulsifier concentration.3.The effect of monomer concentration on MMA latex particle nucleation mode is mainly related to the solubility of MMA monomer in water,and monomer feed rate has little effect on the chain growth reaction process of MMA latex particles.But high monomer concentration or feed rate may easily lead to the formation of new nuclei during the reaction,resulting into stability reduction of the system4.When emulsifier coverage above a certain value,the nucleation and chain growth reactions can be carried out smoothly,and the higher the emulsifier coverage,more stable the polymer latex.But it will lead to Np increase,latex particle size decrease and PSD widen when the emulsifier coverage is too high,that is not conducive to the preparation of monodisperse emulsion.The results of this paper can be a important theoretical guide to controllably initiate secondary nucleation by one-step emulsion polymerization,thereby prepare high solid content polymer emulsion with low viscosity.