Synthesis and thermal behaviour of layered silicate-EVA nanocomposites

Extrusion moulding of both polymer-layered silicate nanocomposites and microcomposites based on the copolymer poly (ethylene-covinylacetate) with either 12 wt.% (EVA 12) or 19 wt.% (EVA 19) vinyl acetate content is described in this paper. The silicates were a synthetic fluorohectorite, rendered organophilic by means of cation exchange of intergallery sodium cations for octadecylammonium or ammoniumdododecanoic acid, and a montmorillonite, rendered organophilic with octadecylammonium. The materials thus obtained were characterised by wide angle X-ray diffraction and transmission electron microscopy. It was established that dispersion of the organic phase depends on both the silicate type and silicate modification. At these vinylacetate contents dispersion was achieved without requiring additional compatibiliser. The thermal behaviour of the composites was examined on a thermobalance in nitrogen and in air. In the nanocomposites acceleration of EVA deacylation and slower thermal degradation were observed, while protection against thermo-oxidation and delayed weight loss were evident in air.