Natural rubber/styrene butadiene rubber blends prepared by ultrasonically aided extrusion

Abstract

Ultrasonically aided extrusion of natural rubber (NR), styrene butadiene rubber (SBR), and NR/SBR blends with ratio of 70/30, 50/50, and 30/70 were carried out at various ultrasonic amplitudes up to 10 mm. A die pressure of NR and NR/SBR blends continuously decreased with increase of ultrasonic amplitude, while that of SBR showed a slight increase with increase in amplitude from 5.0 to 7.5 mm due to a dominant effect of SBR gel formation. Complex dynamic viscosity, minimum and maximum torque of curing curves of NR, SBR, and NR/SBR blends, and cross-link density and gel fraction of their vulcanizates were decreased by the ultrasonic treatment at an amplitude of 10 mm, due to the molecular chain scission. The latter also led to a decrease in the hardness, modulus at a strain of 100%, and abrasion resistance of NR and NR/SBR blends. However, the modulus and abrasion resistance of SBR showed an improvement at amplitude of 7.5 mm, due to a dominant effect of gel formation. Both the tensile strength and elongation at break of ultrasonically treated NR/SBR blends showed a maximum at amplitude of 5.0 mm, with the modulus at a strain of 100% not being affected. Morphological studies using the phasecontrast optical microscope and atomic force microscopy showed a reduction in the size of rubber phases and a better homogeneity of NR/SBR blend by the ultrasonic treatment at amplitude of 5.0 mm. Accordingly, the increase in both the tensile strength and elongation at break of ultrasonically treated NR/SBR blends at an amplitude of 5.0 mm is mainly ascribed to the lower size of rubber phases and improved uniformity of blend caused by the ultrasonic treatment.

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

“…Ultrasonic power consumption as a function of the ultrasonic amplitude during ultrasonic extrusion of star and linear SBR (Data for linear SBR are from Ref. ). For clarity, some data points are shifted along abscissa.…”

“…It has 23.5% bound styrene, a number‐averaged molecular weight of 86 000, a weight‐averaged molecular weight of 330 000, and a polydispersity index of 3.8 . This SBR was used to prepare filled and unfilled compounds and vulcanizates. Carbon black N330 was supplied by Sid Richardson Carbon Corp. (Fort Worth, TX), which has a specific surface area of 78 m 2 /g.…”

“…The testing methods of all unfilled and filled star SBR compounds and vulcanizates are described in the following. The testing methods for all filled and unfilled linear SBR compounds and vulcanizates were described in earlier literature …”

“…The processing procedures for the filled and unfilled linear SBR compounds and vulcanizates are described earlier . The star SBR was masticated using a 1.2 litter Farrel Banbury mixer (Farrel Connecticut Division, Ansonia, CT), at a filling factor of ~70%.…”

“…Since the topology between linear and star SBR is different, it would be very interesting to find if the long‐chain branching, gel formation, and degradation caused by ultrasonic treatment of linear SBR would also occur in treated star SBR. In addition, it is of interest to find similarities and differences between ultrasonically treated linear SBR and star SBR.…”