Studies in the field of mechanochemistry — VI. A study of the disintegration of polystyrene in solutions under the influence of ultrasonic vibrations

Abstract

A SUBSTANTIAL number of studies on the disintegration of polymers by ultrasonic vibrations are reported in the literature. Nonetheless it is extremely difficult to infer any general conclusions as to the mechanism and kinetics underlying the mechanochemistry associated with the changes which come about in high molecular compounds under the influence of ultrasonic vibrations, because the majority of the workers make no allowance for the power of ultrasonic vibrations under water and fail to pay sufficient attention to such important factors as the extent to which the energy of the vibrations is used up, the frequency of the vibrations, the concentration of the solution, the presence of acceptor radicals, etc. Furthermore, until recently the character of the processes that come into play when high intensity ultrasonic vibrations act on solutions had not been studied. At the same time a s tudy of disintegrating-combining processes occurring on exposure of polymer solutions over a wide range of ultrasonic vibration intensities would make it possible: (1) te deduce general characterizing criteria for the kinetics of ultrasonic disintegration, (2) to determine the mechanism of these processes, and (3) to evolve more rational methods of using ultrasonic vibrations for mechanochemical block-graft copolymerization. Although the at tempts of a number of authors [1-3] to approach the ultrasonic disintegration of polymers in terms of formal kinetics led to a specific mathematical interpretation, they threw no light on the mechanism underlying the process. The diversity of the factors that operate in the ultrasonic vibration disintegration of polymers in solution prompts the need to find a method of characterizing the process using constants of a more general nature which are not governed by the particular conditions under which the process is conducted. One of the key factors of the mechanochemical process is the energy yield (~), indicating the number of tools of product formed per unit of energy supplied.