Ultrasonic devulcanization of waste rubbers: Experimentation and modeling |
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Authors: | Dr Avraam I Isayev Sergei P Yushanov Seok-Ho Kim Victor Yu Levin |
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Institution: | (1) Institute of Polymer Engineering, The University of Akron, 44325-0301 Akron, Ohio, USA |
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Abstract: | Continuous ultrasonic devulcanization of ground tire rubber (GRT) and styrene-butadiene rubber (SBR) is considered. Experiments are performed under various processing conditions. Two recipes of SBR with different amounts of polysulfidic linkages are utilized. Gel fraction and crosslink density of devulcanized rubbers are measured and a unique relationship between them is established. Die characteristics with and without imposition of ultrasonic waves are determined. Devulcanized samples are revulcanized and mechanical properties are measured. In some cases, properties of revulcanized SBR samples exceeded those of virgin vulcanizates. This is explained based on the presence of a double network in the revulcanized rubber. A modification of acoustic cavitation and flow modeling of ultrasonic devulcanization of SBR and GRT is proposed using a concept of effective viscosity characterizing the flow of vulcanized particles before devulcanization combined with a shear rate, temperature and gel fraction-dependent viscosity of devulcanized rubber. Velocity, shear rate, pressure, and temperature field along with gel fraction, crosslink density and number of bonds broken are simulated. Predicted data on gel fraction, crosslink density, and pressure using the present modification of the model are found to be closer to experimental data then previously reported.Dedicated to the memory of Professor Tasos C. Papanastasiou |
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Keywords: | Rubber devulcanization revulcanization ultrasound cavitation viscosity model experiment mechanical properties gel fraction crosslink density pressure drop converging flow |
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