Applications of polymer-layered clay nanocomposites
Polymer-layered clay nanocomposite has received much attention because of the significant improvement in thermal stability, flame retardancy and mechanical properties of virgin polymer at very low clay loading. The preparation of a nanocomposite may be accomplished either by in-situ polymerization or by blending, with melt blending the industrially preferred process. In order to obtain a well-dispersed nanocomposite by melt blending, two major factors, compatibility and thermal stability, must be considered. The correct design of modified clay is the key factor to ensure the effective penetration of the polymer or oligomer into the clay layers and results in the desired exfoliated or intercalated nanocomposite. In this study, we have prepared polymer-layered clay nanocomposite using different oligomerically modified clays, which include polycaprolactone, polystyrene copolymer or terpolymer and poly (methyl methacrylate) copolymer. These nanocomposites were evaluated by X-ray diffraction, transmission electron microscopy, thermogravimetric analysis, cone calorimetry and mechanical properties. The results show that polycaprolactone-modified clay can give a completely exfoliated nanocomposite when a clay which contains hydroxyl functionality is used while either immisible or intercalated nanocomposite are formed when the starting clay does not contain functional groups on the ammonium cation; the incorporation of phosphate as a component of an oligomeric ammonium salt modified clay nanocomposite gives a large reduction in the peak heat release rate, suggesting this system has potential for the formation of fire retardant polymeric system. Maleic anhydride modified clay improves the compatibility between the clay and polystyrene, while high and low molecular weight oligomerically-modified clay only has an effect on the mechanical properties and there is no effect on the other properties. A methyl methacrylate oligomerically modified clay show mixed intercalated/exfoliated morphology depending on polymer nature, it has good compatibility with poly (methyl methacrylate) and high impact polystyrene, HIPS, but not with acrylonitrile-butadiene-styrene terpolymer, polypropylene, or polyethylene.
"Applications of polymer-layered clay nanocomposites"
(January 1, 2005).
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