The Significance of Mixing Parameters in Preparation of EVA Nanocomposites by Melt Blending
Mangala Tillekeratne, Margaret Jollands, Ferenc Cser, Sati N. Bhattacharya
Rheology and Materials Processing Center,RMIT university
Australia

Keywords: EVA nanocomposite, melt blending, exfoliation

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In recent years considerable research has been directed towards the preparation and the property enhancement of polymeric nanocomposites formed from smectic silicates. The primary aim of the studies was to prepare nanocomposites with exfoliated nanofillers. Formation of fully exfoliated nanocomposite depends on factors such as polarity of the polymer, the organic modification and the processing conditions. Melt blending process is widely used in preparation of nanocomposites. In this process molten polymer is mixed with organic modified clay either in a twin-screw extruder or internal mixer such as a Hakke Record mixer. Even when the polarity of the polymer and the organic modification are right the processing conditions may play a vital role in successfully delaminating the clay platelets. The formation of nanocomposites takes place in two stages. Firstly, agglomerates consisting of approximately 3000 platelets breakdown into smaller tactoids. This needs high shear and is a relatively fast process. In the second stage polymer chains diffuse into the gallery interlayer spacing of the clay platelets, which may be followed by delamination. In this study ethylene vinyl acetate (EVA) with 9% acetate content and various organo-modified clay types were used to investigate the influence of mixing parameters on the above two processes. EVA and treated clay were mixed in an internal mixer, and barrel temperature, mixing time (residence time) and shear force (rpm) were varied. Mechanical properties and the extent of exfoliation were determined using tensile modulus and strength measurements and X-ray diffraction techniques respectively.