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Role of calcium stearate as a dispersion promoter for new generation carbon black-organoclay based rubber nanocomposites for tyre application



A novel carbon black (CB) and nanoclay (NC) dual phase-filled system in SBR matrix has been developed to be employed as a tyre tread compound with optimized performance properties. The nanocomposite has shown improved dynamic properties i.e. rolling resistance (tan δ at 60°C) and wet skid resistance (tan δ at 0°C), for relatively lower loading of NC (3 phr). However, the mechanical properties and wear resistance combined with above mentioned dynamic properties have been further improved by direct substitution of stearic acid with calcium stearate. This has been argued to be due to enhanced filler-rubber interaction by the strong ionic interactions between the calcium ion (Ca++) and layered silicates (NC) having anionic surface. Transmission electron microscopy and low angle X-ray diffraction studies have revealed the role of calcium stearate as a dispersion promoter for organoclay. Fourier transform infra-red spectroscopy study has shown a shift in the Si[BOND]O[BOND]Si bond towards lower wave number indicating better polymer-clay interaction. A detailed investigation on the dynamic rheological behavior of SBR-CB-NC nanocomposites has been carried out using rubber process analyzer to invoke an insight into the processing behavior of these composites. POLYM. COMPOS., 2013. © 2013 Society of Plastics Engineers