Formation of bubbles during ultrasonic treatment of cured poly(dimethyl siloxane)

A static ultrasonic treatment device was used to investigate the effect of ultrasound on degradation of unfilled poly(dimethyl siloxane) (PDMS) vulcanizate in the absence of shearing effect. The effects of pressure, ultrasound intensity and thickness of the disks upon ultrasonic treatment were investigated. The power consumption was measured as a function of sample thickness, ultrasonic amplitude, and applied pressure. The dynamics of bubble (nucleation, growth and coalescence) was also studied with respect to applied pressure and amplitude. An increase in thickness of the sample was observed during ultrasonic treatment. The unique correlation between gel fraction and crosslink density obtained in the present static experiments was compared with those of continuous devulcanization studied earlier. (C) 2002 Elsevier Science Ltd. All rights reserved.