Effect of ultrasound on free‐radical polymerization in a continuous stirred tank reactor

Abstract

Abstract Methyl methacrylate has been continuously polymerized in toluene solution with AIBN as an initiator at 60°C in a jacketed steel vessel of 890 ml volume with holding times of several hours. Provision was made for good mixing and introduction of a steady stream of monomer, solvent, and initiator. The effluent stream was analyzed for polymer content and molecular weight distribution by gel‐permeation chromatography. After the reactor had been operating for three holding times, an ultrasonic probe in the reactor was turned on, and the effect of the ultrasound on the steady‐state operation of the reactor was observed. The ultrasound caused a rapid increase in the conversion level. A small, concomitant increase in the degree of polymerization was also noted. It is proposed that the ultrasound breaks polymer chains, giving polymeric free radicals which increase in size while increasing the rate of polymerization. Simulation of the polymerization in the stirred tank reactor has been achieved by using a digital computer, and a quantitative treatment of the effect of ultrasound has been developed.