Effect of ultrasonically aided extrusion of NR/BR blends on structure and properties of silica‐filled compounds and vulcanizates

Abstract

Ultrasonic extrusion of NR/BR blends at amplitudes up to 7.5 μm was carried out. Silica or silica/silane at loading of 60 phr was incorporated into blends to prepare compounds and vulcanizates. Effect of ultrasound on molecular structure of rubber blends, rubber–filler interaction of compounds and crosslinking structure of vulcanizates was studied. No gel was generated in NR/BR blends upon ultrasonic treatment, while earlier studies on treatment of BR alone have shown generation of gel. This finding provides means to significantly improve filler dispersion and minimize deterioration of vulcanizate properties. Processing‐structure‐properties relationship was established. Die pressure and ultrasonic power consumption were recorded. Imposition of ultrasound reduced die pressure providing potentials to increase extrusion output. No polymer degradation observed during treatment at amplitudes of 3.5 and 5 μm. A slight degradation was found at 7.5 μm leading to a decrease of storage and loss moduli of the blend, and an increase of loss tangent. Treated blends compounded with silica showed more bound rubber content, better rubber–filler interaction, reduced filler–filler interaction and less flocculation. M100 and tensile strength of NR/BR/Silica 5 μm vulcanizate was increased. In contrast, ultrasonic treatment showed little effect on NR/BR/Silica/Silane blends. The predictions related to tire performance was discussed. POLYM. ENG. SCI., 59:E261–E270, 2019. © 2018 Society of Plastics Engineers