When scientists at Purdue University developed what the school calls “the world’s whitest paint,” the building and construction sector sat up and took note. What sparked their interest was the paint’s unique temperature-control properties—the ultra-white coating is able to cool outdoor surfaces more than 4.5°C (40 degrees F) below ambient temperature, according to Purdue. Practically speaking, that means if you cover your roof in that paint, you could essentially cool your home with much less air conditioning.
But when customers began clamoring for a version suitable for use on cars, trains, and airplanes, the researchers had to go back to the drawing board. The problem: The original formulation required a layer of paint at least 400 microns thick. That’s fine if you’re painting a stationary structure like a building, but it’s too heavy for moving vehicles, where weight can be a drag on efficiency.
Last month the Purdue scientists succeeded in their quest to produce a lighter, thinner paint, after replacing the original pigment—nanoparticles of barium sulfate that reflected 98.1% of sunlight—with hexagonal boron nitride, an ingredient that reflects nearly as much light (97.9%) with just a 150-micron layer of paint.
“This light weight opens the doors to all kinds of applications,” George Chiu, a Purdue professor of mechanical engineering, said in a release. “Now this paint has the potential to cool the exteriors of airplanes, cars, or trains. An airplane sitting on the [runway] on a hot summer day won’t have to run its air conditioning as hard to cool the inside, saving large amounts of energy. Spacecraft also have to be as light as possible, and this paint can be a part of that.”
