Mathematical Model of the Emulsion Polymerization Stability for Vinyl Acetate, Methyl Methacrylate, Butyl Acrylate and Acrylic Acid Tetra-polymers

Abstract

Based on the growth of latex particles surface area during the emulsion polymerization process and the DLVO (Dergagai-Landan-Vervey-Overbeek) theory of emulsion polymerization, a mathematical model of emulsion stability is established. The main hypothesis, based on the concept that the emulsion polymerization reaction occurs very quickly, is that emulsifier placed in the polymerization system is immediately wrapped on the surface of the latex particles. It is proposed that if the latex particle surface area growth (ΔS) and the latex particle surface area which is stabilized by added emulsifier ($S_t{}^{″}$) satisfy the relationship of $V_0=\frac{4}{3}\pi r_0{}^3$, the polymerization system will be a relatively stable system where N is the number of seed latex particles and ($S_t{}^{″}$/N)_0.3 and ($S_t{}^{″}$/N)_0.7 signify the surface area of each stable latex particle when the coverage rate of emulsifier is 30% and 70%, respectively. Based on this hypothesis, the influences of emulsifier amount, diameter of the seeded latexes and distribution of the emulsifier in initial emulsion and the emulsifier added dropwise during the polymerization on the emulsion polymerization stability is simulated and calculated to realize the minimum aggregation during polymerization. According to the simulation results, two optimized polymerization process parameters were determined and verified through experiments based on the emulsion copolymerization of vinyl acetate, methyl methacrylate, butyl acrylate and acrylic acid.

Keywords:

• Emulsion polymerization
• stability
• mathematical model
• aggregation

Note

Notes

1 Actually tetra-polymerization involving four monomers, but described as copolymerization yielding a co-polymer here after.