Polymer nanocomposites as dielectrics and electrical insulation-perspectives for processing technologies, material characterization and future applications

Polymer nanocomposites are defined as polymers in which small amounts of nanometer size fillers are homogeneously dispersed by only several weight percentages. Addition of just a few weight percent of the nanofillers has profound impact on the physical, chemical, mechanical and electrical properties of polymers. Such change is often favorable for engineering purpose. This nanocomposite technology has emerged from the field of engineering plastics, and potentially expanded its application to structural materials, coatings, and packaging to medical/biomedical products, and electronic and photonic devices. Recently these 'hi-tech' materials with excellent properties have begun to attract research people in the field of dielectrics and electrical insulation. Since new properties are brought about from the interactions of nanofillers with polymer matrices, mesoscopic properties are expected to come out, which would be interesting to both scientists and engineers. Improved characteristics are. expected as dielectrics and electrical insulation. Several interesting results to indicate the foreseeable future have been revealed, some of which are described on materials and processing in the paper together with basic concepts and future direction.

I. Introduction

The Development Of Nanocomposites Represents a very attractive route to upgrade and diversify properties of “old” polymers without changing polymer compositions and processing. In contrast to conventional filled polymers, nanocomposites are composed of nanometersized fillers (“nanofillers”) which are homogeneously distributed within the polymer matrix. Due to their very high specific surface areas, a few percent nanofillers can self- assemble to produce skeleton-like superstructures especially when anisotropic fillers with high length/diameter ratio (aspect ratio) are used. In comparison with the conventional micrometer-sized fillers, the same volume fraction of nanofillers contains billion-fold number of nanoparticles. As a result, most of the polymer of nanocomposites is located at the nanofiller/polymer interface. The conversion of bulk polymer into interfacial polymer represents the key to diversified polymer properties. As a function of the nanofiller aspect ratio it is possible to reinforce the polymer matrix and to improve the barrier resistance against gas and liquid permeation. An important aspect of nanocomposite formation relates to processing technology. While many prefabricated nanoparticles are difficult to disperse and require special safety precaution for their handling, modern nanocomposites are formed insitu via shear-induced intercalation and exfoliation as illustrated by the effective diffusion of polymer in between organophilic nanoparticles.