Ultrasonic Extrusion of NR Gum and Its Effect on the Structure and Properties of Unfilled and Silica‐Filled NR

Abstract

Natural rubber (NR) has been extruded without and with ultrasonic treatment at various ultrasonic amplitudes. The effect of ultrasonic treatment on structure of NR, its compounds with silica and silica/silane and their vulcanizates have been studied. Processing‐structure‐properties relationship of untreated and treated materials has been established. With the increase of ultrasonic amplitude power consumption is increased and die pressure is reduced. Size exclusion chromatography measurements show that the NR molecular weight is reduced with the ultrasonic treatment. The storage modulus and loss modulus, complex viscosity and loss tangent results also confirmed the degradation of NR chains by imposition of ultrasound, especially after treatment at high amplitude. After mixing with silica and silica/silane, it was found that degradation of NR caused a reduction in the rubber–filler interaction, an increase in the filler–filler interaction and flocculation upon heating. Physical properties of vulcanizates including M100, ultimate elongation, and stress at break are also deteriorated. POLYM. ENG. SCI., 60:925–934, 2020. © 2020 Society of Plastics Engineers