New chalk-based fabric offers superior cooling for outdoor activities

Researchers have created a new cooling fabric with a chalk-based coating to beat the summer heat.

The University of Massachusetts Amherst researchers state that this innovative fabric can cool the air beneath it by up to 8 degrees Fahrenheit.

“If you walk out into the sunlight, you will get increasingly hot because your body and clothing are absorbing ultraviolet (UV) and near-infrared (near-IR) light from the Sun,” said Trisha L. Andrew, a chemist and materials scientist.

“And as long as you’re alive, your body is generating heat, which can be thought of as light, too.”

Mineral-polymer coating.

For the past few years, scientists have been creating textiles that can simultaneously block sunlight and release body heat, a process referred to as radiative cooling.

Certain materials feature embedded light-refracting synthetic particles, including titanium dioxide or aluminum oxide, within woven fibers. Others use organic polymers in their manufacturing processes to generate light-reflective fabrics.

Despite the potential benefits, expanding the manufacturing of these materials for commercial use is not considered sustainable. Therefore, the researchers decided to create a textile coating that achieves the same result using natural or environmentally friendly materials.

The team developed a sustainable mineral-polymer coating. It is a combination of calcium carbonate and barium sulfate, which are natural minerals commonly found in chalk.

Moreover, the calcium carbonate particles effectively reflect visible and near-infrared light, while barium sulfate particles are adept at reflecting ultraviolet light.

The researchers developed a simple and environmentally friendly process to apply the coating to various types of fabric. For this, small fabric squares were coated with a polymer layer before being repeatedly dipped in solutions containing calcium or barium ions, as well as carbonate or sulfate ions. This procedure created a chalky, matte finish on the fabric.

Shows promise in testing

To evaluate the cooling effectiveness of the treated and untreated fabrics, the researchers conducted tests outdoors on a sunny day when temperatures exceeded 90 degrees Fahrenheit (32 degrees Celsius).

Interestingly, the treated fabric exhibited a cooling effect of 8 degrees Fahrenheit compared to the ambient temperature during the mid-afternoon. “The difference was even greater, a maximum of 15 F, between treated and untreated fabric, which heated the air underneath the sample,” the press release noted.

“What is underneath the sample feels colder than standing in the shade,” said Evan D. Patamia, a graduate student at the university.

In terms of other performance, the coating was found to be durable and withstands the rigors of washing and drying.

Andrew mentioned that their research has been hampered by the size of their laboratory equipment. However, they are exploring the possibility of working with a startup to bring their innovations to pilot-scale production.

“What makes our technique unique is that we can do this on nearly any commercially available fabric and turn it into something that can keep people cool. Without any power input, we’re able to reduce how hot a person feels, which could be a valuable resource where people are struggling to stay cool in extremely hot environments,” concluded Patamia.

If commercialized, this innovative fabric has the potential to make outdoor activities more comfortable and enjoyable for people of all ages.

The findings will be presented at the fall meeting of the American Chemical Society (ACS).