The Rate of Degradation by Ultrasonation of Polystyrene in Solution

Abstract

Abstract The rate of degradation by ultrasonation of polystyrene in tetrahydrofuran solutions has been measured at various concentrations, temperatures, and irradiation intensities. As reported earlier, the course of the changes in molecular weight distributions is independent of the molecular weight (MW) of the initial polymer and of the degradation conditions. Therefore, the time dependence of the extent of the degradation can be meaningfully compared for various reaction conditions and for polymers with different original MWs. The extent of the scission process was expressed in terms of the degradation index (DI), the ratio of the number of chain bonds broken to those initially present. The problem of the existence of a minimum MW required for sonic scission is considered and arguments are advanced in favor of the assumption of a minimum degradable chain length for the purpose of evaluation of degradation data. This minimum MW was found to be about 30,000. DI values were corrected for the “unbreakable”...