Many different materials have been used to reinforce composites. The most popular are the fibers. Flake and particulate materials have also been used to reinforce polymer matrices. A fairly new area of composites has emerged in which the reinforcing material has dimensions of less than or equal to one billionth of a meter, or one nanometer. Such a composite is called a nanocomposite. Very few nanocomposites have actually been developed to the point of commercial application, but their potential has produced a frenzy of research.
There are many types of nanocomposites. The defining characteristic is simply that the reinforcing phase has the dimensions mentioned above. Currently, the most heavily researched type of nanocomposite uses layered mineral clays as the reinforcing phase. Particularly useful are the smectite clays, or clays that can be swollen with small molecules. One such smectite clay is called montmorillonite. Click here to explore the structure of montmorillonite and see how it swells.