Materials

World's whitest paint is now thin enough to coat cars and planes

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Creators of the world's whitest paint hope to soon apply it to planes and cars
Creators of the world's whitest paint hope to soon apply it to planes and cars
The new version of the world's whitest paint seen on the right, compared to the thicker, previous iteration on the left
Purdue University photo/Andrea Felicelli
Study author Xiulin Ruan with his lab’s sample of the whitest paint on record
Purdue University/Jared Pike
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Last year, engineers at Purdue University used their expertise in materials science to produce the world’s whitest paint, with an ability to reflect around 98% of incoming sunlight and therefore holds great potential when it comes to energy efficiency for buildings. The team has now made some tweaks to the recipe and produced a version that is thinner and lighter, which they say is ideal for use on cars, trains and planes.

The original version of the ultra-white paint owed its supreme ability to reflect sunlight to the inclusion of barium sulfate, a chemical compound used in photographic paper and cosmetics. This was added to the mix in the form of particles of different sizes with varying ability to scatter light, enabling the paint to bounce away more of the spectrum of incoming sunlight.

With a reflectivity of 98.1%, the material far exceeded the reflectivity of commercially available heat-reflecting paints that boast 80 to 90% reflectivity. In tests on outdoor surfaces, the team found the paint could significantly lower their temperature compared to the ambient surrounds and could potentially produce cooling effects that are on par with common air conditioners. But the paint did have its shortcomings.

“To achieve this level of radiative cooling below the ambient temperature, we had to apply a layer of paint at least 400 microns thick,” said Xiulin Ruan, who developed the paint. “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.”

So Ruan and his team came up with a new recipe. The new material features boron nitride in hexagonal nanoplatelet form and offers a solar reflectance of 97.9%, so a touch below the original, but does so in layers of just 150 microns thick. This new paint is not only thinner, but is also lower density and therefore weighs around 80% less.

The new version of the world's whitest paint seen on the right, compared to the thicker, previous iteration on the left
Purdue University photo/Andrea Felicelli

“This light weight opens the doors to all kinds of applications,” said George Chiu, a Purdue professor of mechanical engineering. “Now this paint has the potential to cool the exteriors of airplanes, cars or trains. 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 energy. Spacecraft also have to be as light as possible, and this paint can be a part of that.”

The scientists say they are currently in discussions to commercialize their paint and, having filed patents for the technology, are enthusiastic about the possibilities.

“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. It’s pretty amazing that a paint can do all that.”

The research was published in the journal Cell Reports Physical Science

Source: Purdue University

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10 comments
Artificial Gravity
Barium Sulphate (Barite or Barytes) was a cheap additive to paint and has been around for a very long time. It is found in base metal mines in large quantities and is found associated with Lead (Galena) and Zinc (Sphalerite). The Force Crag mine in the Lake District of the UK supplied a paint manufacturer with very clean Barite in the early 80s.When I was working there.
SteveMc
Excellent news! Just what I have been waiting for to adapt into a teeth whitener. You can now have the coolest smile on the planet, literally :)
Excalibur
What excellent timing. This could possibly now feasibly be applied to a huge sail placed in space to reflect sunlight and reduce global warming. With a small booster at each corner for altitude adjustments it should stay up there for as long as we need it and be extended as required from time to time.
3Bravo7
I’ll take 3 gallons please
DavidB
I’d sure like to have read more about the claim that “this paint radiates all the heat into deep space.”

Using what method did the developers test and prove their claim? Specifically:

•By what mechanism is reflected heat able to make it all the way to “deep space”?

• Using what equipment did they trace reflected heat all the way to “deep space”?

• At what distance from Earth do they consider “deep space” to begin?
TechGazer
Replacing my brown asphalt shingle roof with white-painted metal made a huge difference in my cabin's temperature in summer. White roofs should probably be mandatory in areas that require cooling. I think mandatory R-values for new homes is common--and accepted--now, so roof reflectivity requirements should be possible too. It doesn't need to be this super-white paint, but even light colours increase heat absorption quite a bit.
ljaques
Kudos on both formulations, George. But as DavidB asked, how does it radiate all heat into deep space? Does it get past all the water vapor and CO2 and clouds? If so, how so?
I'm interested in the price, too, and when it will be available on painted metal roofing.
Brian Beban
All very well when the paint is pristine but what about when it gets dirty- coated in dust or smog particles?
Dexter
There is a small sliver of radiation wavelengths that can actually pass through the earth's atmosphere and into space. I'm guessing this paint is really good at radiating light at those specific wavelengths.
Captain Danger
I imagine that any paint that reflects that much light would make any object coated in it blinding in sunlight.