Effect of oxygen on the polymerization of vinyl chloride. I. Kinetic features

Abstract

AbstractThe effect of oxygen on the liquid‐phase polymerization of vinyl chloride at 55°C in the presence of an added initiator, bis(4‐tert‐butylcyclohexyl) peroxydicarbonate (Perkadox 16), has been studied by the technique of tumbled dilatometry. With this method, at constant initiator concentration, the induction period showed a half‐order dependence on the initial oxygen concentration. At a constant initial oxygen concentration, the induction period varied inversely as the square root of the initiator concentration. Under the experimental conditions empolyed, the polyperoxy radicals with chloroalkyl (∼CH2ĊHCl) endgroups were not wholly scavenged by molecular oxygen but could undergo various decomposition reactions. The degree of conversion of the initial oxygen to peroxidic compounds did not exceed 30% by weight and was dependent on the shape of the reaction vessel empolyed. The existence of other oxidation products has been demonstrated. At 55°C, the average velocity constant for decomposition of the peroxide products from vinyl chloride, measured in dichloromethane solution, was found to be 8 × 10−5 sec−1. A kinetic scheme involving a predominant cross‐termination reaction is proposed to explain the experimental results.