Achieved 'the world's whitest paint' with a light reflectance of about 98% with a thickness of less than half of the past, reaching a level that can be used for painting airplanes and automobiles

The ``world's whitest paint'' with a light reflectance of 98.1%, developed by the research team of Professor Shulin Luang of Purdue University's Department of Mechanical Engineering, has almost the same reflectance, but is more than half as thin as before. announced that it has developed a new paint that can

Thin layer lightweight and ultrawhite hexagonal boron nitride nanoporous paints for daytime radiative cooling - ScienceDirect
https://doi.org/10.1016/j.xcrp.2022.101058

World's whitest paint now thinner than ever, ideal for vehicles - Purdue University News
https://www.purdue.edu/newsroom/releases/2022/Q4/worlds-whitest-paint-now-thinner-than-ever,-ideal-for-vehicles.html

You can understand what the world's whitest paint developed by Professor Luang's research team is by reading the following article.

The ``whitest paint'' that reflects more than 98% of the light is developed, and the object that is too white cools - GIGAZINE

'White' means 'reflects most of the wavelengths of visible light that strikes it.' In other words, the higher the light reflectance, the whiter the material. And if the light reflectance is high, the light absorption rate will be low, so it will not be warmed by light. For example, painting the roof of a building white absorbs much less light than painting it black, so the interior of the building will be less likely to be heated, which can be expected to lead to savings in air conditioning.

The paint developed by Professor Luang's research team uses barium sulfate nanoparticles and is said to reflect 98.1% of sunlight. However, in order to apply this paint to the roof and keep the temperature 4.5 ° C or more lower than the ambient temperature, it is necessary to apply at least 400 μm (1/25,000 m) of paint to the entire roof. There is no problem when painting on immovable objects such as buildings, but it seems that it is necessary to make it thinner and lighter when painting on spacecraft, airplanes, automobiles, etc.

Professor Luang said, 'I've been contacted by all kinds of people, from spacecraft manufacturers to architects to clothing manufacturers. Everyone asked me two questions: 'Where can I buy it?' 'Can I paint it thinner?' I'm going to ask questions,' he said.

Therefore, Professor Luang's research team has improved the paint and developed a new paint using hexagonal boron nitride as a pigment. This new paint achieved a solar reflectance of 97.9% with a film thickness of only 150μm.

Another major feature of this new paint is that it has gaps created by air, making it porous when viewed at the nanoscale. Therefore, despite achieving almost the same reflectance as paint using barium sulfate, the weight per volume is said to be 80% lighter.

George Chu, a professor of mechanical engineering at Purdue University, said, 'The lightness of the new paint allows it to be used in all sorts of ways. The paint has the potential to cool the exterior of airplanes, cars and trains, for example in the summer. Airplanes running on the runway on a hot day need to have powerful air conditioning to cool the interior, but using this paint can greatly reduce the energy consumed by air conditioning. It can also be applied to spacecraft that require light weight.'

According to Professor Luang, discussions are already underway at the time of writing the article regarding the commercialization of this newly developed paint.