Waxing Hot and Cold
Phase-change materials keep astronauts warm in the black void of space and cool in the solar glare. Microencapsulation is the bane of scent-sensitive magazine readers. Now two companies-Outlast Technologies, based in Boulder, Colo., and Frisby Technologies, based in Freeport, N.Y.-have married these technologies to create new kinds of clothing that regulate the wearer’s body heat.
Phase-change materials store or release heat as they oscillate between solid and liquid form. As a phase-change material changes to a solid state, it gives off heat; as it returns to a liquid state, it absorbs it-like a melting ice cube drawing the heat from a glass of water. In fact, water can be defined as a phase-change material with a trigger temperature of 32 degrees Fahrenheit. Such materials are common; one NASA study identified more than 100.
Adapting technology initially developed for the U.S. space program, the two companies are using microencapsulation-tiny capsules like those enclosing drops of fragrance in glossy magazine perfume ads-to capture the insulating properties of phase-change materials.
“Every other insulation out there depends on one thing: trapped air,” says Matt Maguire, director of technical development at Frisby. “We actually harness your body’s heat. We can trap it and use it when your body needs it.”
Not only do the microcapsules absorb more heat than traditional insulations, but they also release it gradually within a specific temperature range. Rick Wolf, president of Outlast’s apparel and textile division, likens the technology to the dimmer on a light switch. “What we provide is not just insulation but temperature regulation,” he says.
A snowboard glove made with one kind of microencapsulated phase-change material, for example, has a trigger temperature of 83 degrees Fahrenheit. When a snowboarder first puts on the glove, her body heat charges the phase-change material, changing it from a solid state to a liquid. As she rides up the chair lift, the material acts as a thermal barrier, releasing heat as the microcapsules change state.
“The cold will have to turn them to solid before it can penetrate to the hands,” Maguire says.
As the snowboarder rides downhill, she generates body heat that recharges the microcapsules and begins the cycle over again.
Although the companies have licensed the same basic technology, they are commercializing it in different ways. Outlast has developed a proprietary process by which it embeds the microcapsules in strands of acrylic fibers or bonds a layer of them to a fabric. Frisby suspends the capsules in liquids and a variety of foams. It calls the foam it uses in apparel products ComforTemp.
Wolf declines to identify the materials in Outlast products, but Maguire says Frisby uses paraffinic materials that can be formulated with trigger temperatures that range from -30 degrees to 270 degrees Fahrenheit. The materials are housed in capsules that are typically 25 microns in diameter, Maguire says, and they “can withstand repeated melts and freezes at the same temperature almost forever.”
Unlike perfume ads, whose capsules are designed to release fragrance by rupturing, Outlast and Frisby use capsules that can stand up to hard use and repeated laundering. They are not affected by dampness, nor do they lose their effectiveness, as lofted insulations do, when the material is compressed.
Consumers are already reaping the benefits of this new technology. Eddie Bauer, the retail chain and apparel maker, uses Outlast in its EBTek line of outdoor gear. Nordica will use Outlast in the liners of its top-of-the-line ski boots. Glove maker Wells Lamont uses ComforTemp foam in its Hotfingers line of ski and snowboard gloves, while competitors Grandoe and Manzella incorporate Outlast fibers and fabrics in their products. The new materials also are appearing in mountaineering boots, fishing waders, and thermal underwear. And the U.S. military is investigating ways to use them to keep soldiers and divers comfortable in severe weather.
The two companies are now exploring more specialized applications for the new materials, from firefighters’ suits and race car drivers’ boots to cooling systems for computers and delivery containers that keep takeout food warm or blood vials cool. Frisby is even trying to create a heat-resistant coating for the underbelly of a vertical-takeoff aircraft, which could significantly reduce the vehicle’s cost.
“The limits are almost boundless in terms of markets for these products,” Maguire says.