“Where can I buy it, and can you make it thinner?” These are the two questions being asked by everybody from spacecraft and automotive manufacturers to architects and designers about a new innovation developed by researchers from Purdue University, USA.
First created by Purdue University researchers in April 2021, the paint now has a new formulation that not only pushes the limits on how white it can be but is also thinner and lighter, making it ideal for radiating heat away from cars, trains, airplanes and even spacecraft.
The original formulation of the world’s whitest paint used nanoparticles of barium sulphate to reflect 98.1% of sunlight, cooling outdoor surfaces more than 4.5°C below ambient temperature. Roofs coated with this paint could cool the buildings with much less air conditioning. However, there was a problem.
“To achieve this level of radiative cooling below the ambient temperature, we had to apply a layer of paint at least 400 microns thick,” Xiulin Ruan, a Purdue professor of mechanical engineering and developer of the paint said. “That’s fine if you’re painting a robust stationary structure, like the roof of a building. But in applications that have precise size and weight requirements, the paint needs to be thinner and lighter.”
Further experimenting with other materials, Ruan’s team developed their latest formulation, with the new paint made with hexagonal boron nitride achieving nearly the same benchmark of solar reflectance (97.9%) with just a single 150-micron layer of paint.
The newer paint weighs 80% less than the barium sulphate paint, yet achieves nearly identical solar reflectance.
According to George Chiu, a Purdue professor of mechanical engineering and an expert in inkjet printing, the lightweight characteristics of the new paint opens the doors to all kinds of applications including cooling the exteriors of airplanes, cars or trains. For instance, an airplane sitting on the tarmac on a hot summer day won’t have to run its air conditioning as hard to cool the inside, saving large amounts of fuel. Similarly, the paint can be an important specification in spacecraft manufacturing with its lightweight properties.
“Using this paint will help cool surfaces and greatly reduce the need for air conditioning,” Ruan said. “This not only saves money, but it reduces energy usage, which in turn reduces greenhouse gas emissions. And unlike other cooling methods, this paint radiates all the heat into deep space, which also directly cools down our planet.”
The Purdue University team is currently in discussions to commercialise the paint.
This research has been published in Cell Reports Physical Science.
Image source: https://stories.purdue.edu/the-whitest-paint-is-here-and-its-the-coolest-literally/
