Effect of ultrasonic extrusion of star styrene-butadiene rubber on properties of carbon black- and silica-filled compounds and vulcanizates

摘要

Extrusion of star styrene-butadiene rubber (SBR) without and with ultrasonic treatment at amplitudes 3.5, 5, 7.5, and 10 mu m was carried out. The molecular structure of untreated and treated star SBR was determined. Significant reduction of die pressure was observed during ultrasonic treatment due to the thixotropic and degradation effects. Ultrasonic treatment of star SBR at 3.5 mu m created molecules of higher molecular weight via long-chain branching without gel formation. Ultrasonic treatment of star SBR at 5 mu m created a small amount of gel. At high ultrasonic amplitudes more gel was generated hindering mixing of star SBR with silica. Extruded star SBR was compounded with carbon black and precipitated silica, with and without silane. It was found that the long-chain branching induced by ultrasonic treatment improved the rubber-filler interaction in precipitated silica without silane, as confirmed by the increase of bound rubber content. The filler-filler interaction was reduced in silica compounds without silane, as indicated by study of Payne effect. The significantly improved rubber-filler interaction and reduced filler-filler interaction led to an increase of the modulus at 100% elongation and tensile strength of SBR/silica vulcanizates. Extensive comparisons were made with earlier study on ultrasonic treatment of linear SBR. (c) 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47451.