Nanocomposites Based on NR/SBR: Effects of Nanoclay and Short Nylon Fibers on the Cure Characteristics and Thermal Properties

Natural rubber and styrene butadiene rubber (NR / SBR) reinforced with both short nylon fibers and nanoclay (Cloisite 15A) nanocomposites were prepared in an internal and a two roll-mill mixer by a three-step mixing process. The effects of fiber loading and different loading of nanoclay (1wt%, 3wt%, 5wt%) were studied on the Cure Characteristics and Thermal Properties of the nanocomposites. The adhesion between the fiber and the rubber was enhanced by the addition of a dry bonding system consisting of resorcinol, hexamethylene tetramine and hydrated silica (HRH). This nanoclay was used in place of hydrated silica in a HRH bonding system for SBR/NR-short nylon fiber composite. Nanoclay was also used as a reinforcing filler in the matrix-short fiber hybrid composite. The curing characteristics of the composites have been studied by using cure rheometer. Samples were vulcanized at 150 degrees C using a hot press after determination of the curing characteristics. The cure and scorch time of the composites decreased while minimum, maximum torque, and cure rate increased when short fiber and nanoclay content were increased. The values of storage modulus above the glass transition temperature of NR/SBR/organoclay nanocomposites increased remarkably with increasing the content of organoclay and fiber loading. The height of the tan (max) has decreased and glass transition temperature (T-g) has increased with increasing nanoclay and loading fiber. These results were consistent with the dynamic mechanical thermal analysis (DMTA) data as well as macroscale mechanical properties tested on the samples. The thermogravimetry analysis (TGA) shows that a small amount of organoclay greatly improved the thermal stability, which was attributed to the good barrier properties of the dispersed organoclay layers.