Polymer nanocomposites clay barrier forms

The mechanism of flammability reduction for polymer nanotube and nanofiber nanocomposites (Chapter 10) is similar to that for clays a nanofiUer-rich surface or barrier forms, which slows the rate of mass loss and therefore the rate of heat release. There is little reduction in the total heat release, indicating that the carbon nanoflbers and nanotubes only reduce the flammability of the... 

Intercalated nanocomposites are usually formed by mixing in the melt or in situ polymerisation whereas exfoliation may require more complex processing depending on the properties of the clay (Usuki et al, 1993). However, such layered silicate-based polymer nanocomposites have attracted considerable recent interest after the commercialisation of polypropylene-and nylon-6-based materials (Krishnamoorti and Yurekli, 2001, Kiersnowski and Piglowski, 2004). The major barrier to commercialisation has been developing techniques to ensure a reliable and reproducible product which has now been addressed for clay-based composites some thirty or so years after they were first developed. 

Polymer nanocomposites represent a new and promising area of polymer research. Among the particles used to form nanocomposites, organically modified clays are of particular interest, hi such systems, the combination of high aspect ratio clay mono- or multilayers and their interactions with the matrix polymer can lead to improvements in barrier, thermal, and mechanical properties at far lower loading levels than are typically used in conventional filled polymer composites [1,2,3]. 

Orientation Once the particles are dispersed in the polymer, they must be oriented so that the flat surface of the clay is parallel to the surface of the packaging material to maximize the barrier effect. Several models have been developed in order to describe the mass transfer within the nanocomposites. Most models assume that the platelets have a regular and uniform shape (rectangular, sanidic, or circular) and form a regular array in space. They are either parallel to each other or have a distribution of orientations, with the... 

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