A team of researchers has devised a durable chalk-based fabric coating that cools the air underneath the treated fabric by up to 8° Fahrenheit.
THE RESEARCHERS: The project is the work of Trisha L Andrew, professor of chemistry, chemistry graduate student Evan D Patamia and undergraduate Megan K Yee at the University of Massachusetts Amherst, US.
- The results were presented at the fall meeting of the American Chemical Society (ACS).
THE CONTEXT: If people walk out into the sunlight, one will get increasingly hot because the body and clothing are absorbing ultraviolet (UV) and near-infrared (near-IR) light from the sun. And as long as you’re alive, your body is generating heat, which can be thought of as light, too.
- To make people more comfortable outside, scientists have been developing textiles that simultaneously deflect the sun’s rays and push out natural body heat—a process known as radiative cooling.
- Some of those materials have light-refracting synthetic particles, such as titanium dioxide or aluminium oxide, embedded into spun fibres.
- Others use expensive organic polymers such as polyvinylidene difluoride, which require toxic per- and polyfluoroalkyl substances—PFAS, or “forever chemicals.”
- In each of these cases, production on an industrial scale is simply unsustainable.
THE SOLUTION: So, Andrew posed the question to Patamia and Yee: “Can we develop a textile coating that does the same thing using natural or environmentally benign materials?”
- Inspired by the crushed limestone-based plasters historically used to keep houses cool in extremely sunny places, Patamia and Yee worked on inventing a method to integrate calcium carbonate—the main component in limestone and chalk—as well as bio-compatible barium sulphate onto a polymer coating, into a process that Andrew had previously developed known as called chemical vapour deposition (CVD).
- The researchers tested the cooling abilities of their new fabric outside on a sunny summer day when the temperature soared to more than 90° F. They observed that the air temperatures underneath the treated fabric were 8° F cooler than the ambient temperature in the middle of the afternoon.
- When they compared their new fabric to conventional, untreated cloth, the difference was even greater: their chalk-coated sample was up to 15° cooler than the untreated fabric, which heated the air underneath the sample.
WHAT THEY SAID:
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.
— Evan D Patamia
Chemistry graduate student
University of Massachusetts Amherst
