Ultrasonic devulcanization of carbon black-filled ethylene propylene diene monomer rubber

The recycling of carbon black (CB)-filled ethylene propylene diene monomer (EPDM) rubber was carried out by using a newly built continuous ultrasonic grooved-barrel reactor. Using this reactor, it was possible to increase by two times the output of devulcanized rubber in comparison with the coaxial reactor built earlier. The dynamic viscoelastic properties of virgin vulcanizates, devulcanized, and revulcanized EPDM rubbers were measured. The cure behavior of virgin and devulcanized rubbers was measured. The gel fraction and crosslink density of virgin vulcanizate and devulcanized EPDM rubbers, and the mechanical properties of virgin vulcanizates and revulcanized rubbers were determined. Similar to our previous findings using the coaxial reactor, the revulcanizates of unfilled EPDM rubbers of the present study showed higher mechanical properties than those of the virgin unfilled vulcanizates. However, a progressive decrease in the mechanical properties of CB-filled EPDM revulcanizates with an increase of filler concentration, attributed to partial deactivation of filler, was observed. An improvement of mechanical properties of vulcanizates was achieved upon blending the devulcanized and virgin filled rubbers. (C) 2003 Wiley Periodicals, Inc.