Structure and properties of ultrasonically extruded SBR/BR blends and prepared compounds and vulcanizates with various fillers

The ultrasonic treatment of styrene-butadiene rubber (SBR)/butadiene rubber (BR) 50/50 blend in single screw extruder was carried out at amplitudes up to 10 μm. The untreated and treated SBR/BR blends were mixed with carbon black (CB), silica, and silica/silane to prepare 50/50/60 compounds. It was found that ultrasonic power consumption increased and die pressure reduced with the increase of ultrasonic amplitude, indicating a potential to increase extrusion output rate with the aid of ultrasound. Molecular weight of blends treated at 3.5 μm increased, and high molecular weight tail was observed at 5, 7.5, and 10 μm. Solvent extraction experiments showed the formation of gel in blends treated at 7.5 and 10 μm. No gel was observed in blends untreated and treated at 3.5 and 5 μm. SBR/BR/silica vulcanizates prepared from the blend treated at 5 μm showed the reduced loss tangent at −30°C, 0°C, and 60°C, predicting a lower snow, wet traction, and rolling resistance. Reduced loss tangent after ultrasonic treatment was a result of reduced filler flocculation. The tensile strength and elongation at break of all treated SBR/BR and SBR/BR/CB vulcanizates treated at 3.5 and 5 μm increased. Modulus 100% elongation (M100) of vulcanizates prepared from SBR/BR/silica treated at 5 μm was also increased.