Fillers dispersion, definition

It should be noted that this is quite an unusual law, since in other known cases durability of solids is expressed by stronger laws, namely, exponential or power laws. Thus, in the given example we cannot give a unified definition of yield stress. The work cited is the only published observation of the durability of a filler s structure in dispersion systems. Therefore at present it is difficult to say how much such phenomena are typical for filled polymers, but we cannot exclude them. 

Abstract Nanostructured organic-inorganic composites have been the source of much attention in both academic and industrial research in recent years. Composite materials, by definition, result from the combination of two distinctly dissimilar materials, the overall behavior determined not only by properties of the individual components, but by the degree of dispersion and interfacial properties. It is termed a nanocomposite when at least one of the phases within the composite has a size-scale of order of nanometers. Nanocomposites have shown improved performance (compared to matrices containing more conventional, micron-sized fillers) due to their high sirnface area and significant aspect ratios - the properties being achieved at much lower additive concentrations compared to conventional systems. 

While there is no precise definition, nano-fillers can be considered as particles which, when dispersed in polymers, are very small in at least one dimension. This concept is pushed quite far in some of the literature, with particles of up to at least a hundred nanometers being described as nano-particles. A reasonable working definition would seem to be that at least one dimension of the effective particle, when dispersed in a polymer matrix, should be no more than 20 nm, or 200 A. As a result, the specific surface area, which plays a significant role in the effects observed, will be at least 150 m /g. The term effective particle is used to eliminate fillers, such as carbon blacks, where the primary particle could be in the specified range, but are strongly aggregated into larger structures, that become the effective particles. 

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