Mechanical and Morphological Properties of Short Nylon Fibre Reinforced NR/SBR Composites: Optimization of Interfacial Bonding Agent

Nylon short fibres were incorporated in NR/SBR rubber matrix with and without abonding system on a two-roll mill mixer. A dry bonding agent consisting ofresorcinol, hexamethylene tetramine and hydrated silica (HRH) was chosen asthe interfacial-bonding agent for this composite system. The effect of bonding agentcontent on the microstructure, mechanical and morphological properties of thecomposites was investigated. Samples were vulcanized at 150°C using a hot pressafter determination of the curing characteristics. The cure and scorch times of thecomposites decreased with increasing bonding agent concentration, while themaximum torque values showed an increasing trend. The bonding agent not onlyprovided a shorter curing time but also enhanced the mechanical properties of thecomposite. The scanning electron microscopy (SEM) of the composite fracturesurfaces implied that the presence of bonding agent has led to the breakage of fibresand less dark holes indicating the pull out of fibres without bonding agent. The resultsof anisotropic swelling studies, carried out to analyze fibre/matrix interactions andalso orientation of the fibres, showed that the restriction to swelling is higher for thecomposites containing bonding agent. Furthermore, the preferential orientation of thefibres was observed to be in the milling direction. For composites prepared with shortfibres and different loading levels of bonding agent, the dependence of the storagemodulus (G') on angular frequency followed a clear non-terminal behaviour.