CONTINUOUS ULTRASONIC DEVULCANIZATION:COMPARISON OF CARBON BLACK FILLED SYNTHETIC ISOPRENE AND NATURAL RUBBERS

摘要

The continuous ultrasonic devulcanization of CB filled IR was carried out. Similar to the unfilled IR, the power consumption during the devulcanization of the filled IR increased with the increase of ultrasonic amplitude indicating the increase of the extent of devulcanization. This is in contrast with observations in CB filled NR where power consumption showed a maximum at an intermediate amplitude suggesting a decrease in the extent of devulcanization at higher amplitudes. The different behaviors between the two rubbers probably resulted from a slight difference in the amount of stereoregular structures. The network structures of the virgin vulcanizates, devulcanizates and revulcanizates were characterized. Kinetics of revulcanization, rheological properties of the devulcanizates and mechanical properties of revulcanizates were compared with those of virgin uncured IR and their vulcanizates. The effect of processing oil on the IR vulcanization, devulcanization and revulcanization was examined. Processing oil slightly delayed the vulcanization and lowered torque but did not affect the degree of reversion. It also increased power consumption during devulcanization and decreased gel fraction and crosslink density suggesting that the addition of the oil causes more devulcanization. The revulcanization of the filled IR occurred without the induction period regardless of the presence of CB and processing oil. The retarder introduced in the recipe was effective in improving the scorch safety and minimizing the reversion in revulcanization. The experimental data on normalized gel fraction versus crosslink density of filled IR and NR at low CB concentrations was found to fall into the master curve, which is probably determined by the main chain structure of both rubbers consisting of cis-l, 4 isoprene. At high CB concentrations some differences were observed. The simulation results predicted such a behavior.