A Model for Rubber Degradation under Ultrasonic Treatment: Part II. Rupture of Rubber Network and Comparison with Experiments

Abstract A simple theoretical model of network degradation around ultrasonically pulsating cavities is considered. The model is based on the concept of overstressed chains and provides a simple tool to estimate a number of chains which should be involved in mechanochemical degradation at a given amplitude of ultrasonic pulsation. High amplitude cavitation with no collapse-like effects is demonstrated to result in significant reduction of the rubber crosslink density. This model also predicts considerable effects of rubber degradation on elastic properties of rubber around a pulsating cavity including certain irreversible effects and residual deformations. The Dobson—Gordon theory of rubber network statistics is employed in order to interpret the experimental data on the dependence of gel fraction in devulcanized rubbers on crosslink density in the gel. Application of the approach to devulcanized styrene—butadiene rubber (SBR) and silicone rubber demonstrates that the assumption on spatial—temporal randomness of rubber degradation allows us to achieve a fairly good agreement between experimental and theoretical data.