world's whitest paint is now thinner than ever, ideal for radiating heat away from vehicles

Purdue University makes world’s whitest paint thinner than ever

In 2021, a team of engineers from Purdue University in Indiana, the US, developed the world’s whitest paint that could curb climate change by cooling cool down buildings and therefore reducing the need for air conditioning. Now, the researchers have made some changes to the formula, producing a thinner and lighter version that is ideal for casting heat away from cars, trains, and airplanes.

image by Arkin Si on Unsplash | head image by Jeremy Bezanger on Unsplash

optimized solar reflectivity with lighter weight 

The 2021 iteration of the ultra-white paint used nanoparticles of barium sulfate, which reflect 98.1% of sunlight and cool exterior surfaces by more than 4.5 °C below ambient temperature. ‘To achieve this level of radiative cooling below the ambient temperature, we had to apply a layer of paint at least 400 microns thick,’ shares Xiulin Ruan, professor of mechanical engineering at Purdue University (find more here) and developer of 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.’

As a result, Ruan’s team started experimenting with different materials to test the limitations of each one’s capacity to disperse sunlight. Their most recent creation is a nanoporous paint with pigment made of hexagonal boron nitride, which is largely used in lubricants. With just one 150-micron layer, this new paint produces approximately the same reflectivity (97.9%). The paint also has air gaps, which at the nanoscale make it exceedingly porous. Together with its thinness, this decreased density has another significant benefit: lighter weight. The newer paint provides approximately equal solar reflectivity while weighing 80% less than barium sulfate paint.

the world’s whitest paint is now thinner and lighter than ever | image courtesy of Purdue University/Andrea Felicelli

whitest paint ever coming to the market

‘This light weight opens the doors to all kinds of applications,’ mentions George Chiu, a professor of mechanical engineering at Purdue and an expert in inkjet printing. ‘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.’

‘Using this paint will help cool surfaces and greatly reduce the need for air conditioning,’ shares Xiulin Ruan. ‘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.’ As for the frequently asked question – where can I buy the paint? – the professor explains. ‘We are in discussions right now to commercialize it. There are still a few issues that need to be addressed, but progress is being made.’

the team at Purdue has created the whitest paint on record | image courtesy of Purdue University/John Underwood