World’s Whitest Paint Can Keep Cars and Planes Cool

A couple of years ago, scientists from Purdue University were able to create a paint so white and thus so reflective that it could keep buildings cool on the sunniest of days. Buildings account for 40% of global greenhouse gases and being able to significantly reduce the use of air-conditioning would be a real game-changer in the fight against climate change.

An earlier iteration of ultra-white paint was based on the same mineral used to make chalk, good ol’ calcium carbonate. It has a reflectance of about 95.5 percent, which means that only about 5 percent of sunlight that falls on it would be absorbed as heat. The scientists tinkered around a bit more and were able to use barium sulfate, another commercially available material, to create an even “whiter” paint that reflects 98.1% of sunlight while absorbing only 1.9%.

While this version was great for buildings, a layer with a minimum thickness of 400 microns was required to achieve this level of absorption and would have been too heavy for certain applications—such as transport vehicles.

So, the scientists tinkered some more and have recently released a version of the paint based on boron nitride that is thinner and lighter. Hexagonal boron nitride has a high refractive index (in layman’s term, ability to scatter sunlight) and a unique morphology called nanoplatelet, which is more effective in bouncing back solar radiation. The paint also incorporates air voids (porous) to keep it light.

The newest version of the paint is slightly less reflective—ie. a reflectance of  97.9%—but can achieve that with a layer that is only 150 microns thick or about twice the thickness of human hair. This means it can be used on cars, planes, trains and even spacecraft without affecting performance noticeably.

Purdue University researchers have created a new formula for the world’s whitest paint, making it thinner and lighter. The previous iteration (left) required a layer 0.4 millimeters thick to achieve sub-ambient radiant cooling. The new formulation can achieve similar cooling with a layer just 0.15 millimeters thick. This is thin and light enough for its radiant cooling effects to be applied to vehicles like cars, trains and airplanes. (Purdue University photo/Andrea Felicelli)

Imagine a car parked outside or airplane waiting on the tarmac on a hot, sunny day…the driver/pilot wouldn’t have to crank the air-conditioning to keep the interior cool. Then, imagine this multiplied by billions—the reduction in power consumption and costs, and impact this could have on reducing greenhouse gases is mind-boggling.

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