Exfoliation of Nanolayer Assemblies for Improved Natural Rubber Properties: Methods and Theory

Natural rubber (NR)-based nanocomposites were prepared by conventional processing techniques using various natural and modified nanoclays. For modified montmorillonite (Cloisite (R) 15A), the 300% modulus, tensile, and tear strength exhibited substantial increments of over the gum due to better dispersion. The unmodified montmorillonite clay (Cloisite (R) Na+) failed to improve the above properties significantly. The limitations of Cloisite (R) Na+-based NR nanocomposites prepared by the conventional method were alleviated using latex blending technique. Pre-exfoliated aqueous suspension of Cloisite (R) Na+ was blended with NR latex under special conditions and cured by pre-vulcanization as well as conventional curing. These showed predominantly exfoliated morphology along with substantially improved physical and mechanical properties. A simple theory based on effective surface area factor was proposed to account for the structure-property correlations.