Researchers at Zhengzhou University and the University of Adelaide have developed a new purple cooling fabric that stays up to 6.2°C cooler than conventional purple cotton under direct sunlight, offering a potential alternative to traditional white passive cooling textiles according to findings published in the journal Small.
How the High-Tech Purple Cooling Fabric Works
Most passive cooling fabrics rely on white colors to reflect sunlight away from the human body. Darker shades naturally absorb more solar energy, making them difficult to cool effectively. Purple presents a specific engineering challenge because the color stems from absorbing green light, which forms one of the strongest segments of the solar spectrum.
To overcome this, the research team engineered a material that reflects an average of 87.6% of solar radiation. At the same time, the textile emits 96.4% of mid-infrared radiation, allowing body heat to pass through the atmosphere toward outer space.
“We have traditionally had to make a choice between cooling performance and appearance,” said University of Adelaide Professor Jun Ma, a materials engineer from the School of Chemical Engineering and a co-author of the study. “Our research shows that we can have both. We can make a fabric that looks purple, but at the same time reflects most of the sun’s energy and releases heat very efficiently.”
Outdoor Testing and Performance Comparison
Outdoor field testing under direct sunlight demonstrated significant temperature reductions compared to standard commercial textiles. According to the study data, the newly developed purple fabric registered 2°C cooler than commercial white cotton and 2°C cooler than commercially dyed purple cotton.
Furthermore, simulated skin covered with the high-tech purple fabric stayed up to 8°C cooler than uncovered simulated skin during daytime testing. For comparison, white cotton provided a maximum reduction of 4.6°C, while conventional purple cotton achieved just 2.8°C.
Pro Tip: When evaluating passive cooling textiles for outdoor use, look at both solar reflectance and mid-infrared emission metrics to understand how effectively a material dumps heat into the atmosphere rather than trapping it against the skin.
Durability and Potential Applications for Outdoor Workers
Beyond thermal performance, the experimental fabric is lightweight and flexible. It withstands significant mechanical stretching and allows water vapor, including sweat, to pass through freely. Laboratory evaluations also showed the material is highly water-repellent and maintains its cooling capabilities after 50 washing cycles.
The textile also provides strong ultraviolet resistance, retaining its optical performance after high-intensity UV aging tests equivalent to roughly 108 days outdoors.
“For outdoor workers, athletes and anyone exposed to hot weather, staying cool is not just about comfort,” said Yangzhe Hou, a PhD candidate in the School of Chemical Engineering at the University of Adelaide and co-author on the paper. “We are interested in developing fabrics that can help manage body temperature without consuming additional energy.”
The research team suggests the underlying technology can be adapted to other colors by utilizing different metal-organic frameworks with distinct optical properties. This approach could eventually expand the color palette available for high-performance cooling apparel.
Did you know? Purple is one of the hardest colors to engineer for passive cooling because its distinct hue absorbs green light, which carries some of the highest energy levels found in the solar spectrum.
Frequently Asked Questions
Why are most passive cooling fabrics white?
White fabrics naturally reflect most incoming sunlight away from the body, preventing solar absorption and keeping the wearer cooler.
How much cooler is the new purple fabric compared to standard white cotton?
In direct sunlight testing, the new purple fabric stayed up to 2°C cooler than conventional white cotton and was shown to stay up to 6.2°C cooler than conventional purple cotton.
Does the fabric lose its cooling performance after washing?
No, testing showed the textile retains its cooling performance and water-repellent properties after 50 washing cycles.
What underlying materials give the fabric its color and cooling properties?
The fabric utilizes specific metal-organic frameworks that provide optical properties capable of reflecting solar radiation while emitting mid-infrared heat.
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