In the news for many years but primarily the province of theoreticians and researchers until recently, nanotechnologies are beginning to cross the threshold into commercialization. Several forms of nanostructures may play significant roles in the composites industry.
Nanotech can be defined as technology at less than 100 nanometers. A nanometer (nm) is one billionth of a meter, or 80,000 times smaller than the thickness of a human hair. Nanoparticles are simply particles with diameters in the 1 nm to 100 nm range. Nanofibers are electro-spun whiskers with diameters in the 10 nm to 100 nm range and length-to-diameter ratios of 1,000:1 or more. Carbon nanotubes, the most well-known nanotubes, are made up of carbon atoms arranged in a hexagonal pattern and resemble thin cylinders of chicken wire. They can be single-walled or multi-walled. Fullerenes are closed molecular cages made of carbon atoms. For example, the C60 fullerene (a/k/a "buckyballâ€) is composed of 60 carbon atoms in a soccer ball shape. The extremely small size of such nanostructures, coupled with their extremely high surface-to-volume ratios (as much as 1:5), can lead to unusual characteristics that can have profound effects on performance.
A few nanoscale technologies already have been commercialized for use as additives in the resin matrices of composite laminates. There is little doubt that applications for these products in advanced composites will eventually include improved catalysts for resin systems; nanoporous particles, which will increase adhesive bond strength; and several types of nanoparticles which can be used as additives to increase mechanical properties, such as wear resistance, conductivity, flame retardance, stiffness, and strength.
One promising development, the work of performance materials developer Nanocomp Technologies Inc. (Concord, N.H.), is a reportedly ready-to-use textile material made from long carbon nanotubes. Available in both nonwoven sheet and yarn forms, the material could provide the practical utility that nanocomposites have promised but have not yet delivered. Real and potential applications range from body armor to structural composites as well as commercial energy storage and electronics thermal management. The nonwoven textile sheet measures about 2 ft2/0.19m2 square, weighs about 0.04 oz/1g, and ranges from 10 to 15 microns thick. After post-treatment with different chemistries, the fabric can be folded and bent repeatedly without breakage. The company hopes by the end of 2008, to upgrade to continuous, nonbatch production machinery, creating a pricing structure ("hundreds of dollars per kilogramâ€) that would put the material in the same ballpark as aerospace-grade carbon fiber.