The world’s whitest paint is now more diverse

The first copy of the painting is inscribed in Guinness Book of Records Since 2021. It keeps surfaces so cool that in the future it could reduce the need for air conditioning in many man-made buildings.

Researchers Xiulin Ruan (left) and Joseph Peoples use an infrared camera to compare the cooling performance of white paint samples on a surface during tests with the first version of the paint.

Photo: Purdue University/Jared Pike

This first version, made of barium sulfate nanoparticles, reflects 98.1% of sunlight, making it possible to cool exterior surfaces more than 4.5°C below ambient temperature.

Its creators had hoped it could one day be applied to rooftops to reduce air conditioning-related energy costs, but it wasn’t just builders interested in it.

I was approached by spaceship manufacturers, architects, and even clothing and shoe manufacturers who wanted to know more about the product.In a press release, paint designer Xiulin Ruan, professor of mechanical engineering at Purdue University in the US said.

All of these organizations wanted to know where to buy the paint, but especially if it could be made thinner because the composition of the original paint did not allow it to be applied to a variety of surfaces.

big downside

To achieve a level of radiative cooling below room temperature, we had to apply a layer of paint at least 400 μm thick.Professor explains.

” This is great if you are painting a sturdy stationary structure, such as the roof of a building, but has been impossible on surfaces with special size and weight requirements, such as a car or airplane. »

To meet the requirements of such constructions, the coating must be thinner and lighter.

improved formula

So the Purdue researchers conducted experiments with other materials that would allow them to create a coating that could evenly scatter sunlight while requiring a thin layer of the material.

Its most recent formulation is a nanocoating that includes hexagonal boron nitride as a pigment, a substance used primarily in lubricants.

The first version of the coating (left) requires a layer of 0.4 millimeters thick to achieve cooling. The new formula achieves similar cooling with a layer thickness of only 0.15mm.

Photo: Associated Press/Purdue University/Andrea Felicili

This new innovation achieves approximately the same level of sun reflectance (97.9%), but requires a single 150-micron thick layer of coating.

It is allowed to maintain, under direct sunlight, an average temperature of 5°C to 6°C lower than the ambient temperaturenotes the study published in Cell Reports Physical Sciences (A new window) (in English).

The coating also includes air voids, which makes it very porous at the nanoscale and reduces its density. So it is less heavy than the first version.

Another important advantage is that the new formula weighs 80% less than the barium sulfate primer coating, while showing only a minimal reduction in solar reflectance.

New thinner, lighter paint can now cool the exterior of planes, cars or trains.

A plane waiting on the tarmac on a hot summer day won’t have to run the air conditioner so intensely to cool the interior, saving huge amounts of energynotes engineer George Chiu, who is also an expert in inkjet printing at Purdue University.

” Our coating not only saves money, but also reduces energy consumption and greenhouse gas emissions. »

towards marketing

Professor Xiulin Ruan’s team has submitted patent applications to protect their creation. It has also entered into discussions with partners with a view to marketing it.