Effect Of Electrolyte On The Stability Of Butyl Acrylate Emulsion Polymerization

Emulsion polymerization is a traditional polymerization method which possessing an very important position in the production of polymer. Emulsion polymerization possesses the advantages of low viscosity, easy heat transferring and simple equipments. The commonly used monomer are styrene, acrylonitrile, acrylate, methyl acrylate etc. The acrylate-based polymer have the advantage of shallow colour and lustre, excellent outdoor weatherability and good mechanical properties and was studied and used as coating, adhesive, thickener, textile treatment agent at home and abroad. The acrylate-based polymer possessed broad prospects in industry, hence, it is critical to develop latex with excellent properties and good stability. The recipe of conventional emulsion polymerization normally includes monomer, water, surfactant and initiator. Sometimes, electrolyte is added into emulsion polymerization system deliberately to adjust the p H of the aqueous phase, reduce the latex viscosity, lower the freezing point of the aqueous phase and improve the stability of latex.The control of particle size and distribution of latex is the same target of academe and industry. The semi-continuous emulsion polymerization is the widely accepted method, the size of seed particle and the addition speed of monomer are used to control the nucleation and growth of particle. In this manuscript, Poly?butyl acrylate??PBA? latices with controllable particle size?90–350 nm? were synthesized via one-step batch emulsion polymerization in the presence of different species of electrolyte. The evolution of particle size and number as a function of monomer conversion were tracked in order to investigate the effect of electrolyte species on the particle stabilityIn the first part, we investigate the effect of different electrolyte concentration on the particle size, number and particle size distribution of latex and the kinetics of polymerization. Experiment results indicate that the time that the particle coagulation occurs dominates the the final particle size distribution; the initial polymerization rate increases with the increasing electrolyte concentration, but the polymeriation rate of stage ?decreases with the electrolyte concentration.In the second part, we study the effect of electrolyte with different anion and cation on the particle stability. For electrolyte with different anions, the particle size of final latices decreased with increasing p H of the aqueous phase and the sequence was Na₂CO₃ < NaHCO₃ < Na₂C₂O₄ < Na Cl, latices with Na₂SO₄ showed some particular performance and possessed of a particle size up to 347.4 nm; for electrolyte with different valences of counter ion, while achieving the similar particle size?Ca. 120nm?, an obvious variance in ionic strength was found(0.03, 0.016 and 0.0035 mol kg^-1 for Na⁺, Mg²⁺ and Al³⁺). The difference is due to the synergetic and constrained interaction between potential energy and the adsorption of surfactants. In the experiment with different radius of cation, the final particle size was 122.5, 126.2 and 129.5 nm respectively which increases with the increasing radius of cation. The cation with small radius possesses a large electron cloud density and a strong hydration ability which impires the electrostatic interaction between alkali metal cations and ions on the particle surface. The compressed capability of cation decreased and the coagulation degree is impaired.In last part, we investigate the influence of comonomer acrylate on particle stability. All the experiment with the addition of acrylate shows the occurance of particle coagulation and the particle size increases with the acrylate content. The p H still an important factor in the determination of particle size, but the purticularity of is Na₂SO₄ impaired due to the addition of acrylate.