Mechanical and thermal properties of nano-composites of poly(vinyl chloride) and co-poly(vinyl chloride-vinyl alcohol-vinyl acetate) with montmorillonite

Nano-composites of poly(vinyl chloride) and co-poly(vinyl chloride-vinyl alcohol-vinyl acetate) with clay were prepared by the solution intercalation method. Montmorillonite, a three-layered clay mineral consisting of silicate sheets, was employed as reinforcing phase. Compatibilisation between the two phases was achieved by intercalation of montmorillonite with dodecylamine to increase the organophilicity of the clay. Thin films of pure polymers and their composite materials containing various proportions of clay were obtained by evaporation of the solvent. After further drying under vacuum, these films were characterised for their mechanical and thermal properties. The results have shown that the modulus and the tensile strength of the composite films increased initially compared to the pure polymers and then decreased upon further addition of the clay. The glass transition temperature of the films, measured from the maxima of the tan delta curves using dynamic mechanical thermal analysis, showed a greater shift towards higher temperatures in copolymer-clay than in PVC-clay films. This is indicative of a higher degree of interaction between the two phases of copolymer-clay composites than PVC-clay composites. The microhardness values and the decomposition temperatures also increased in both systems with the addition of an appropriate amount of the clay.