Molecular Mobility in Ultrasonically Devulcanized Unfilled Butadiene Rubber

Abstract

Abstract We have used NMR relaxation and pulsed-gradient diffusion measurements at 70 °C in unfilled butadiene rubber (BR) before and after crosslinking, and after subsequent devulcanization by intense ultrasound. In an effort to support this method of rubber recycling, characterization has been performed at the molecular level. The transverse relaxation (T2) decay was successfully described using a three-component model. The components are attributed to entangled and crosslinked networks; light sol and dangling network fragments; and partially unreactive oligomers. All component molecular mobilities and the relative contributions of the components to the echo were investigated. Devulcanization decreases the diffusivity of the oligomer remnants and increases mean diffusivity of the light sol. The additional amount of extractable sol produced by devulcanization of BR is more than that of silicone rubber, indicating that the ultrasonic devulcanization of BR is more efficient than that of silicone rubber. The present results are compared with our previous NMR studies of devulcanized rubbers.