The fast pace of research in polymer-clay nanocomposites has already developed products that are being used commercially for certain applications such as automotive with nylon nanocomposites (the most utilized system) in timing belt cover for automobiles, and in packaging film. This book describes the development of rubber clay nanocomposite with improved mechanical & gas barrier properties. Styrene-butadiene (SBR)/clay nanocomposites were synthesized with clay (montmorillonite) functionalized with 4 different surfactants (commercially available & developed in lab). The surfactant chain length & functional groups affected the dispersion of clay nanolayers in the matrix & the nanocomposite's properties. The research developed a partially-exfoliated nanocomposite with elastic modulus at 25°C that was 14 times higher than SBR, and oxygen permeability that was reduced by 60% with 15 wt.% silicate. This best performance was attributed to the presence of the vinyl-benzyl group in the surfactant, providing higher compatibility with SBR and greater dispersion of the organoclay, increasing the tortuous path for gas diffusion through the rubber