Polymer nanocomposites: current understanding and issues

Polymer nanocomposites, or more appropriately polymer nanostructured materials, represent a radical alternative to the conventional filled polymers and polymer blends, in which discrete constituents on the order of a few nanometres are incorporated in the polymer matrix. In the last decade, the utility of inorganic nanoparticles as additives to enhance polymer performance has been established and now provides numerous commercial opportunities, ranging from advanced aerospace systems to commodity plastics. The incorporation of low volume additions (1-5 wt-%) of highly anisotropic nanoparticles, such as layered silicates or carbon nanotubes, have resulted in property enhancements with respect to the neat polymer that are comparable with that achieved by conventional loadings (15-40 wt-%) of traditional fillers. The lower loadings facilitate processing and reduce component weight. In addition, unique value added properties not normally possible with traditional fillers were also observed, such as high stiffness, reduced permeability, optical clarity and electrical conductivity have been achieved. However, the development of chemical and processing procedures to disrupt the low-dimensional crystallites (tactoids and ropes) to achieve uniform distribution of the nanoelement (layered silicate and single wall carbon nanotube respectively) continues to be a challenge. Even less developed are approaches to provide spatial and orientational control of the hierarchical morphology. There exists an immense potential for polymer nanocomposites, in particular, polypropyelene-clay nanocomposites paving the way for future technologies for the materials community at large.