Ultrasonic degradation of sol rubber in solution

Abstract

Sol rubber dissolved in three solvents-cyclohexane, petroleum ether (40-60°C. fraction), and toluene-was degraded by ultrasonic waves, the degradation kinetics being followed by measuring spectrophotometrically the consumption of the free radical scavenger α ,α'-diphenyl-β-picryl hydrazyl. The kinetic data have been examined by the rate equations developed from two different approaches: one by Jellinek and the other by Ovenall. It has been observed that the number of bonds broken as a function of time can be fitted equally well by both equations in the initial stage, but as the time of degradation increases, especially when the number-average degree of polymerization attains a value less than 3Pe/2, the rate can be described better by Jellinek's equation than that of Ovenall. The rate constants K and the final degree of polymerization for rubber are found to depend on the nature of the solvent.