Structure and Properties of Ultrasonically Extruded NR/BR Blends and Their Compounds Filled with Silica

NR/BR blends with a blending ratio of 50/50 have been prepared using an ultrasonic single-screw extruder. The untreated blend and blends treated at ultrasonic amplitudes of 3.5, 5 and 7.5 µm were obtained. During ultrasonic extrusion, the ultrasonic power consumption increased and the die pressure decreased with an increase of the ultrasonic amplitude. Cole-Cole plots show that branched structure has been generated during ultrasonic treatment at amplitudes of 3.5, 5 and 7.5 µm. The prepared blends were mixed with 60 phr of silica. The bound rubber content of the silica-filled compound treated at 5 µm increased, indicating a better rubber-filler interaction. The storage modulus at small strain amplitudes of silica-filled compounds treated at 3.5, 5 and 7.5 µm reduced, indicating a weaker filler-filler interaction. This is a result of reduced flocculation upon heating, as confirmed by annealing experiments at 160^oC. The reduced flocculation is believed to be related to the branched structure created during ultrasonic treatment. Swelling test results on vulcanizates showed an increase of the crosslink density for the silica-filled blend treated at 5 µm. DMA results predict increased snow and wet tractions for all treated vulcanizates and a reduction of rolling resistance for vulcanizate treated at 5 µm. Values of M100, tensile strength and elongation at break of silica-filled vulcanizates treated at 5 µm increased compared to the untreated one.