Recycling of tire‐curing bladder by ultrasonic devulcanization

Abstract

Abstract The recycling of butyl rubber‐based tire‐curing bladder was carried out by means of a grooved barrel ultrasonic extruder. Die pressure and ultrasonic power consumption were measured as a function of flow rate and ultrasonic amplitude. Gel fraction and crosslink density of the ultrasonically devulcanized rubber were substantially reduced. In turn, this led to some reduction in gel fraction and crosslink density in the revulcanized rubber. These findings were correlated with dynamic properties and the cure behavior of the devulcanized rubber. The mechanical properties of the revulcanized rubber, dependent on processing conditions during devulcanization, were compared with that of the virgin vulcanizate. Good mechanical properties of revulcanized rubber was achieved with 86 and 71% retention of the tensile strength and the elongation at break respectively, and with modulus increased by 44%. The devulcanized rubber was found to contain tiny gel particles of a wide size distribution with a predominant size of <4 μm. POLYM. ENG. SCI., 46:8–18, 2006. © 2005 Society of Plastics Engineers