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Keeping cool

Interest builds for thermal control in wearable technology.

Features | May 13, 2024 | By: Marie O’Mahony, Ph.D.

Aersulate nonwovens from Outlast, is the company’s latest development in thermoregulating textiles. Photo: Marie O’Mahony

Thermal control is one of the basic functions of textiles for apparel. The key association is that it affords comfort, so it can be tempting not to properly prioritize it, given its other performance factors. Now, from sportswear to workwear, new and hybrid fiber and fabric technologies are offering advances for a range of markets.

PCM success

Outlast’s Phase Change Material (PCM) was “developed for outer space, tried and tested on earth,” the company boasts, and they are correct. The thermo-technology was originally developed by NASA for use in spacesuits to help protect astronauts from extreme temperature fluctuations in space. It was one of the success stories of NASA’s Spinoff program, offering technologies to SMEs for terrestrial benefits. 

The microencapsulation of the PCM offered a unique approach to thermal regulation, with another point of difference that the fabric immediately felt different—actually cool to the touch. This, not surprisingly, quickly created the expectation of progress, and the company today has over 100 patents, with applications that go beyond clothing to include bedding and other products. 

Aerogel advancements

More than two decades since it was launched the company continues to look at new developments directed at thermal regulation, including looking to space once again. Outlast has now launched Aersulate using aerogel, a product made from silica, which is the basic material of sand.  Notoriously difficult to handle as a material, it has been referred to as “liquid smoke.” But with its very porous structure and an air content of around 98 percent, it is highly insulating, making it the lightest solid material on earth. 

Outlast has developed a technique that allows the company to permanently bond the aerogel to a textile substrate in a very high level of concentration. They are doing this without negatively impacting the original properties of the fabric or any subsequent treatments, such as flame retardancy, that may be needed.

Researchers at ITA Institut für Textiltechnik, RWTH Aachen, are also working with aerogel, developing fibers that are made with 100 percent aerogel in a way that is scalable for manufacture and cost effective. The cellulose aerogel textiles are offered as sustainable, as well as more flexible and with better drape qualities than more conventional aerogel products, which can suffer from brittleness. The quality of these new fibers makes it possible to process them using conventional textile machinery. The ITA Group International Centre for Sustainable Textiles is an internationally oriented research and training provider with the Institut für Textiltechnik as its core.

Unconventional wicking

Thirtysevenfive is taking a different approach. Created by Cocona Labs headquartered in Boulder, Colo., 37.5® Technology is a sustainable thermo-regulation material science company. They are using ultra-porous volcanic minerals, as well as an activated carbon derived from coconuts to create fibers that can then be used in fabric, insulation foams, as well as laminate materials. The active particles in the 37.5 fiber are energized by human infrared energy, enhancing the speed of moisture evaporation from the body, which removes humidity next to the skin. 

The sheer number of micropores in the active particles serves to increase the surface area of the fibers and other materials, so that the moisture is removed at vapor stage before it becomes sweat. This approach differs from conventional wicking, where moisture is spread on the fabric before evaporation, with technology that focuses on reducing the humidity that is next to the skin to maximize the evaporative cooling.

In support of its belief that “the most sustainable solution is to use less and reuse more,” Freudenberg Performance Materials has launched Comfortemp HO 80xR as a circular thermal insulation wadding. The materials are made using 70 percent recycled polyamide taken from end-of-life fishing nets, carpet flooring and industrial plastics that would otherwise end up in landfill sites. The remaining 30 percent uses virgin fibers. As it has a comfortable, soft handle, the fabric can be used for apparel. Produced as roll goods, the tendency of wadding to clump is avoided giving garments a longer use life before further recycling is needed. 

More new technologies in passive thermal management are also being explored, often as part of a multi-functional approach in advanced wearable technologies, and as e-textile improvements are discovered, these too will bring the promise of greater success for safer, and more comfortable garments.

Dr. Marie O’Mahony is an industry consultant, author and academic, and a frequent contributor to Textile Technology Source. She is based in London. 

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