When it comes to staying cool on hot days, it's not a matter of wearing less clothing, but rather more clothing. Right Clothing. A new cloth covering can help with this and is essentially made of chalk.
In natural, unfiltered sunlight, it is the near-infrared and ultraviolet wavelengths that transmit heat to our bodies.
With this in mind, scientists have previously developed experimental fabrics containing compounds such as titanium dioxide, which reflect these wavelengths away from the wearer's body, providing a cooling effect. right now But the technology required to apply these substances to textile fibers makes scaling up for commercial production difficult.
Other groups have explored the use of light-reflecting organic polymers, such as polyvinylidene difluoride. While these substances are sometimes easier to work with, their production requires the use of PFAS (aka “forever chemicals”), which persist in the environment for long periods of time and have been linked to a number of health problems.
Looking for an easy and environmentally friendly alternative, a team at the University of Massachusetts Amherst was inspired by reflective limestone-based exterior plasters used to keep homes cool in hot climates. Calcium carbonate is the main component of limestone, and chalk is a type of related to Limestone.
Using a technique known as chemical vapor deposition, the scientists first applied a 5-micron-thick layer of poly(2-hydroxyethyl acrylate) adhesive to small squares of various commercially available fabrics.
These squares were then repeatedly dipped in solutions containing calcium or barium ions and in solutions containing carbonate or sulfate ions. This resulted in the formation of uniformly sized calcium carbonate crystals on the fabric, resulting in a reflective matt white surface.
The finished samples were then tested outside in sunlight at air temperatures above 90 ºF (32 ºC). The temperature under the frames was found to be an average of 8 ºF (4 ºC) cooler than the ambient temperature.
Additionally, when temperatures under samples of treated fabrics were compared to temperatures under untreated samples of the same fabrics, the difference jumped to a total of 15 ºF (8 ºC). This is significantly more cooling than could be produced by the shading effect alone.
And more importantly, tests have shown that repeated washings do not cause the coating to come off the underlying materials.
“What makes our technique unique is that we can do this on almost any fabric that’s on the market and turn it into something that can keep people cool,” says graduate student Evan D. Patamia, who led the study with Prof. Trisha L. Andrew and undergraduate student Megan K. Yee. “Without any power input, we can reduce how hot a person feels, which could be a valuable resource in places where people struggle to stay cool in extremely hot environments.”
The technology is currently being commercialized through a spinoff company, Patamia, and the team will present their findings at the fall meeting of the American Chemical Society.
Source: University of Massachusetts Amherst