A Dilatometric Method of following the Non-stationary State of Polymerization Reactions

Abstract

IN recent years, several non-stationary state methods^1–5 have been developed for the measurement of kinetic life-times and hence the velocity coefficients for the propagation and termination steps in polymerization reactions. These methods, with the exception of that of Burnett¹, depend upon the system remaining virtually adiabatic for periods of at least 10 sec. following the commencement of irradiation; this is due to the very slow conduction of heat through the walls of the reaction vessels. Burnett's results, which were interpreted on the basis of the system remaining isothermal during the reaction, can alternatively be explained⁶ if non-isothermal conditions prevail during the reaction. This, however, invalidates the method as a means of measuring non-stationary states. The method reported here, like that of Burnett¹, involves the measurement of change of volume immediately following the beginning of irradiation, but differs in that the non-stationary state period is measured from the volume expansion–time curve instead of the contraction–time curve.