Emulsion polymerization of butyl methacrylate initiated by 2,2′‐azoisobutyronitrile, 3. On the applicability of the modified Smith‐Ewart model

Abstract

AbstractThe applicability of the modified Smith‐Ewart model to the butyl methacrylate emulsion polymerization in interval II, initiated by both 2,2′‐azoisobutyronitrile (AIBN) and ammonium persulfate at 60°C, was tested. The equilibrium monomer concentration in the latex particles in interval II was found to be constant and independent of the emulsifier concentration and the initiator type used. The rate of initiation increases with increasing emulsifier concentration for the polymerizations initiated with a water‐soluble initiator. In the systems with the oil‐soluble initiator, the rate of initiation is independent of the emulsifier concentration. The rate of polymerization increase with increasing emulsifier concentration for both initiator systems. In the system with the oil‐soluble initiator lower values of the polymerization rate and higher values of the viscosity‐average molecular masses of the polymer were observed. The number of particles, the radical concentration within polymer particles and the calculated rate of polymerization increase, while the mean particle radius decreases with increasing concentration of the emulsifier for both systems. The average‐number of radicals per particle and the ratio of the rate constants for propagation and termination was found to be independent of the emulsifier concentration and the initiator type. A good agreement was observed between the estimated and observed particle radii for both initiator systems. The Smith‐Ewart model was found to be applicable for the emulsion polymerization of butyl methacrylate initiated by both ammonium persulfate and AIBN.