Natural Rubber Nanocomposites: Performance of Nanoclays in Latex and Dry Mixing Systems

Polymer nanocomposites reinforced by relatively small amounts of ultra-fine, nano-particles (most often clay platelets) proved exceptionally promising engineering materials with unexpectedly high stiffness/toughness ratio, gas barrier properties, flame retardence, etc. The real interest in nanotechnology is to create revolutionary properties and functions by tailoring materials and designing devices on the nanometer scale. Natural rubber nanocomposites are proven materials for their high air impermeability, excellent solvent resistance, high modulus etc. The form of rubber viz. latex or dry rubber, mainly decides the nature of the clay to be selected for composite preparation. For dry rubber compounding, the clay should be organophilic whereas a hydrophilic layered silicate is preferred for latex addition. In the first category, the nature of the modifiers of the nanoclay, the layer distance and the polarity of the polymer, play a crucial role in clay exfoliation and hence the composite properties. As nanoclays are silicates modified with alkyl substituted quaternary ammonium compounds, these substituents may interfere with the amine accelerated sulphur cure system and further the clay intercalation process. Due to this, most often it is difficult to achieve the expected level of properties. In the case of latex, the hydration efficiency of the silicate, aspect ratio of the clay platelets and the polarity of the polymer decide the composite properties. In certain cases the intercalation process can be accelerated by the addition of polar polymers.
The factors to be considered in the selection of clay for natural rubber compounding,  the effect of modifiers in the vulcanization reaction, characterization of the NR nanocomposites by TEM, XRD, FTIR and TGA will be discussed in the proposed talk. NR latex, latex blend and clay treatment for efficient intercalation will be summarized.