Ultrasonically assisted single screw extrusion of carbon black (CB)-filled styrene–butadiene rubber (SBR) compounds up to 60 phr was carried out and its processing characteristics were measured. The effects of ultrasonic amplitude on rheology, extractable amount, vulcanization behavior, mechanical properties, abrasion, electrical resistivity, and morphology were investigated. Increasing ultrasonic amplitude led to a reduction of extractable content with the effect diminishing with increasing CB loading. Treated compounds showed an increase in viscosity at certain amplitudes. Cure curves revealed reduced induction times with increasing amplitude, except at the highest CB content. The maximum torque of the cure curve, crosslink density, and mechanical properties of vulcanizates all showed an increase at certain ultrasonic amplitudes. An increase in the glass transition temperature (Tg) and a decrease in tan δ at Tg were observed with increasing amplitude. Ultrasonically treated unfilled and CB-filled compounds led to vulcanizates with significant and slight improvements in abrasion, respectively. Ultrasonic treatment caused a significant reduction in the electrical percolation threshold of vulcanizates. Morphological study by atomic force microscope revealed a creation of unique CB agglomerates, suggesting the strong interactions between the SBR and CB aggregates in treated compounds, leading to reinforcing effects in vulcanizates.
Available at: http://works.bepress.com/avraam_isayev/193/