Browsing by Author "Greesh, Nagi Giuma"
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- ItemPreparation of polymer-clay nanocomposites using emulsion polymerization : influence of clay modifiers on the final nanocomposites morphology(Stellenbosch : Stellenbosch University, 2006-12) Greesh, Nagi Giuma; Sanderson, R. D.; Hartmann, P. C.; Stellenbosch University. Faculty of Science. Dept. of Chemistry and Polymer Science.ENGLISH ABSTRACT: Modification of clay surfaces is an essential requirement for the formation of polymerclay nanocomposites. The clay surface can usually be modified by the replacement of inorganic cations on the clay surface by cationic surfactants. Further, clay has the ability to adsorb some organic compounds that have specific functional groups, such as sulphate and amides, by the formation of hydrogen bonds between these functional groups and hydroxyl groups of the clay. Therefore a clay surface can be treated using non-cationic organic compounds. The marn objective of this study was to modify a clay surface usmg 2-acrylamido-2-methyl-l-propanesulphonic acid (AMPS), and investigate the interaction occurring between AMPS and clay. The adsorption behaviour of AMPS was compared to organic molecules having similar groups namely: Sodium l-allyloxy-2-hydroxypropyl (Cops), N-isopropylacrylamide (NIPA) and Methacryloyloxy (MET). An understanding of the type of interaction between clay and organic modifier is useful in terms of understanding the mechanism of clay exfoliation in emulsion polymerization. The properties and structure of nanocomposites were characterized using SAXS, TEM, DMA, and TGA. The strncture of the nanocomposite was affected by the type of clay modifiers. Nanocomposites prepared using AMPS show an exfoliated structure, while other nanocomposites, i.e. those prepared using Cops, NTPA, and MET showed structures between intercalated and partially exfoliated. The mechanical and thermal properties of nanocomposites were found to be strongly dependent on the degree of clay distribution through the polymer matrix. The nanocomposites with exfoliated structures were found to have higher Tg values, improved mechanical prope1ties, and also better thermal stability than nanocomposites with intercalated structures.