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Advances in polymer nanocomposite technology   Publication : [S.l.] Nova Science Pub Inc 2010 . 445 p. , Polymer nanocomposites have revolutionised the research effort in the field of composites as they lead to the achievement of synergistic effects from the organic and inorganic components of the system and have led to the expansion of the spectrum of application of the commodity polymers to more advanced high end applications. Although a number of successful systems could be achieved, the inorganic filler still could not be optimally dispersed on nanometer scale in non polar polymers. Also, the thermal degradation of the surface modification of the inorganic component disturbs the organic inorganic phase compatibility and hence the resulting composite properties. In recent years, many new techniques have been employed to overcome these problems which include more advanced modification protocols of the inorganic filler, development of more thermally stable surface modification and altogether new synthesis technologies for polyolefin nanocomposites. There has also been a constant need to compare the composite properties with the property models and hence to be able to predict the properties of the similar systems in advance. However, until now, the conventional models developed for conventional micro composites were used, which in no way maps the nanocomposite systems. The recently developed statistical as well as finite element methods focusing the real nanocomposite morphologies have been more helpful for this purpose. Though a tremendous research focus lies on these polymer systems, there is also a need to give some attention to more environmentally friendly nanocomposite systems and to develop methods to achieve proper recycling. 26 cm. Date : 2010 Disponibilité : Exemplaires disponibles: La bibliothèque des sciences de l'ingénieur (2),

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Polymer nanocomposites : advances in filler surface modification techniques   Publication : [S.l.] Nova Science Pub Inc 2009 . 216 p. , Polymer nanocomposites revolutionised the research in this field owing to the tremendous improvement in the composite properties at very low filler volume fraction. The surface modification of the filler, generally layered silicate montmorillonite clay, is required to compatibilise the organic and inorganic phases. The inorganic clay was modified conventionally with alkyl ammonium ions and the exfoliated nanocomposites with polar polymers could be formed where the clay could be dispersed at nanometer scale. During the initial phase of nanocomposite developments, only ammonium ions of fixed chain length were exchanged on the clay surface. However, this technology suffered when polyolefins and other non-polar polymers were used owing to the difficulties in dispersion of polar clay in the hydrophobic matrices. At best, only partially exfoliated composites could be formed by using these ammonium modified clays. To circumvent these limitations, two possible routes have been followed. By polarising the polymer matrix (e.g. by addition of compatibilisers or surfactants), one can achieve compatibilisation between the organic-inorganic phases. However, this technology leads to deterioration of nanocomposite properties even though better delamination is achieved. On the other hand, one can also focus on the more efficient modification of the filler surface so that the residual polarity after modification of the surface with conventional ammonium ions is also eliminated. A number of new clay surface modification techniques have been developed in the recent years which help in the generation of more exfoliated polymer nanocomposites. These techniques do not rely on the ion exchange of fixed chain length ammonium ions, but lead to generation/exchange of long and polydisperse polymer chains. These techniques include grafting of polymers to the clay surface, grafting of polymers from the clay surface, controlled living polymerisation from the clay surface, in situ generation of polyolefins from the clay surface and clay surface reactions etc. and form very robust technologies for the complete organophilisation of the clay surface. The generation of thick brushes around the clay surface owing to the better surface modification leads to better coverage of the electrostatic forces binding the clay platelets together and also leads to higher basal plane spacing between them. As a result, the modified platelets are more susceptible to exfoliation when compounded with the polymer matrices. 26 cm. Date : 2009 Disponibilité : Exemplaires disponibles: La bibliothèque des sciences de l'ingénieur (1),

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