Aerogels Heat Up

Nanotechnology may be the wave of the future, but not all nanotech qualifies as new. Consider, for example, aerogels, which have been around for more than 70 years. Also called "frozen smoke," these materials take the form of a solid silica lattice with a network of pores whose size averages just ten nanometers. "Think of them as puffed up sand," says Marc Lebel, a chemical engineer and vice president of Aspen Aerogels Inc. (http://rbi.ims.ca/4402-524). With ambient thermal conductivity values of 12 mW/m-K, frozen smoke might seem like a fantastic insulation material. In fact, it's about two to eight times better than fiberglass and plastic foams. But silica aerogels have spent most of their history as a lab curiosity, owing to their extreme brittleness and processing times measured in weeks. Aspen Aerogels, however, has developed a proprietary method for impregnating silica and related aerogels into various non-woven textiles—and do so at production speeds. "Our big breakthrough has been finding ways to make aerogels commercially viable," says Lebel. Together, the aerogel and textile form thin, flexible, lightweight yet highly effective insulation blankets useful in a wide variety of applications.

Natural Resources

From cryogenic systems for shipping liquid natural gas to pipe insulation for offshore drilling, aerogels have started to see use in the equipment that helps find and move natural resources. Among the first commercial applications is pipe-in-pipe insulation for ENI's K2 offshore oil development product in the Gulf of Mexico. According to Lebel, the thinness of aerogel insulation reduces overall diameter of these sub-sea pipes. For instance, a pipe that has an outside diameter of 20-inches using traditional foam insulation can have a 16-inch diameter using aerogel insulation. And smaller pipes help reduce all kinds of cost factors—from the cost of the steel to the that of transporting and laying the pipe.

Vehicles That Fly—and Maybe Ones that Drive

One of the first target markets for the aerogel blankets involves military vehicles. Lebel reports that Aspen aerogel materials are currently being evaluated as a way to provide thermal insulation and reduce the infrared signature of helicopters and other military air-craft. One key consideration in these applications is balancing weight against thermal performance. And on this score, aerogel blankets excel. They have R values ranging from R-10 to -15 per inch versus R-3 per inch for fiberglass and up to R-7.5-inch for common foamed plastics. Yet with upwards of 95 percent of their volume consisting of air, aerogels alone have a density as low as 0.001 g/cc. When combined with the textile, they essentially take on the density of the non-woven, Lebel explains. So far, the military applications have been Aspen's focus, but Lebel notes that commercial aircraft and underhood applications in cars, particularly race cars, might be a good fit too. Aspen has products good for temperatures up to 650C—as well as products for cryogenic temperatures.

Technical Apparel

When it comes to garments, it doesn't get more technical than space suits. And indeed, NASA has shown interest in the aerogels as a possible insulation solution for its new generations of extra-vehicular suits, according to Lebel. But aerogels have found a home here on Earth in garments and footwear used by skiers, snow boarders, and others who brave the cold for fun. Lebel reports, for instance, that snowboard maker Burton has been using Aspen material in outerwear for the past two seasons. And he adds that several other makers of winter gear will follow suit this year. In all these applications, aerogels ability to insulate without loft comes into play. "Most insulation materials rely on loft," Lebel says, explaining that loft means more bulk and keeps many insulation materials out of applications where they see compressive loads. Aerogels, by contrast, still insulate when compressed and can even be used underfoot. Polar Wrap's new Toasty Feet inserts, for example, use the material. Makers of ski and winter boots have also expressed interest, Lebel reports. Aspen's currently commercial aerogels can take compressive loads up to 150 psi. "We intend to increase that," Lebel says. The company has developmental products that can handle up to 4,000 psi.