A comparative study on the influence of nanoclay and nanosilica on the mechanical properties of NR/SBR/NBR ternary rubber nanocomposites

Abstract

The unfilled rubber blends composed of natural rubber (NR), styrene-butadiene rubber (SBR), and acrylonitrile-butadiene rubber (NBR) exhibited inferior properties due to the lack of a reinforcing agent. However, the incorporation of nanofillers significantly improved the strength of the compound. Two nanofillers, nanoclay (NC) and nanosilica (NS), were added to the NR/SBR/NBR blends, which were prepared using an open milling process with nanofiller contents varying from 0 to 10 phr. The use of fine particle-sized fillers required consideration of potential outcomes related to rubber-filler and filler-filler interactions, as well as the varying polarity and composition of the rubber components, which influenced these interactions. To enhance the compatibility between the non-polar and polar rubber phases, 3 phr of Ultrablend 4000 was used. The rubber compound was cured using conventional sulfur vulcanization. Cure characteristic results showed that NC had minimal effect on curing time. The mechanical properties and swelling resistance of the blends compatibilized with Ultrablend 4000 were evaluated using tensile tests, hardness, rebound resilience, abrasion resistance, and mole percent uptake measurements. NS proved to be more effective than NC in enhancing tensile strength, with optimal stress at 100% elongation and tensile strength occurring at 6 phr of NS. Beyond this point, tensile strength decreased due to NS particle agglomeration, which weakened the nanocomposites. Increasing nanofiller content in the NR/SBR/NBR vulcanizates led to improvements in tear strength, hardness, and abrasion resistance, attributed to better filler dispersion and stronger filler-rubber interactions. Notably, NS had a more significant impact on the mechanical properties and swelling resistance of the nanocomposites compared to NC. The percentage increase in tensile strength, stress at 100% elongation, and tear strength of the NR/SBR/NBR nanocomposites shows increases of 154%, 48%, and 155%, respectively, compared to the base vulcanizates.