Cure Characteristics and Mechanical Properties of NR/ SBR Blends Filled with Nano-sized CaCO3

Abstract

Four kinds of nano-sized calcium carbonate (CaCO3) surface-modified with stearic acid, aluminate, titanate and aluminate-titanate complex coupling agents, were used to reinforce natural rubber (NR)/styrene-butadiene rubber (SBR) blends. The effects of surface modification and CaCO3 content on the cure characteristics, swelling behaviour, and mechanical properties of NR/SBR blends were studied. The surface modification of CaCO3 improved the processing and mechanical properties, and the stearic acid coated CaCO3 (SA-CaCO3) had finer dispersion and produced a better reinforcement effect than the other modified CaCO3. Furthermore, a commercial high abrasion furnace carbon black (HAF) was used for comparison. The results showed that both CaCO3 and HAF increased the cure rate, reduced the optimum cure time and improved the mechanical properties of NR/SBR blends at appropriate filler contents. The tensile strength of filled NR/SBR composites reached its maximum value when the SA-CaCO3 content was 50 phr or the HAF content was 30 phr. The modulus at 200%, tear strength, and Shore A hardness of filled NR/SBR composites all increased with increasing filler content. The CaCO3 reinforced the NR/SBR blends to some extent, though it was still not as effective as HAF.