Manipulation of Competitive Growth for Particle Size Control in Emulsion Polymerization

The utility of the growth mechanism to influence relative particle growth is investigated in a semi-batch reactor. A dynamic competitive growth model is developed and used to simulate the growth of two monodisperse polystyrene particle populations (bidisperse system) at 50 °C. Validation of the model with on-line density and on-line particle diameter measurements demonstrates that radical absorption into particles is more likely to occur by a collision mechanism than either by a propagation or diffusion mechanism. Experimental and simulation results show that relative narrowing of the bidisperse system increases as the weight fraction polymer inside the particles (W p) decreases. It is concluded that the ability to alter W p in a semi-batch reactor makes this mode of operation attractive for particle size distribution control.