The paint material developed by the research team at Purdue University can reflect approximately 98% of incoming light, helping to save energy for buildings, airplanes, cars, and trains.
Last year, engineers at Purdue University utilized their expertise in materials science to create the whitest paint in the world with the ability to reflect about 98% of incoming light, thus presenting a significant potential for energy savings in buildings. Now, the research team has made some adjustments to the formula, resulting in a lighter version that is ideal for use on cars, trains, and airplanes. They published their research findings on October 3 in the journal Cell Reports Physical Science.
Researcher Xiulin Ruan and a sample of white paint. (Photo: Jared Pike)
The original super-white paint’s ability to reflect sunlight comes from barium sulfate, a chemical compound used in photographic paper and cosmetics. This compound is added to the mixture in various particle sizes with diverse light-dispersing capabilities, allowing the paint layer to reflect a wider spectrum of incoming light.
With a reflectivity of 98.1%, this material far exceeds the reflectivity of commercially available heat-resistant paints, which have reflectivity rates of 80% to 90%. In tests conducted on outdoor surfaces, the research team observed that the paint layer could significantly reduce temperatures compared to the surrounding environment, creating a cooling effect comparable to that of popular air conditioning units. However, the paint does have some limitations.
“To achieve cooling through radiation below the surrounding temperature, we need to apply a paint layer that is at least 400 microns thick,” said Xiulin Ruan, the developer of the paint. “This is fine if you are painting a solid structure like a rooftop. But in applications that require precise dimensions and weight, the paint needs to be thinner and lighter.”
Therefore, Ruan and his colleagues devised a new formula. The improved material includes boron nitride in the form of hexagonal nano-sheets, providing a solar reflectivity of 97.9%, slightly lower than the original but with a thickness of only 150 microns. The new paint layer is not only thinner but also has a lower density, making it approximately 80% lighter.
“The lightweight nature opens the door for all kinds of applications,” said George Chiu, a mechanical engineering professor at Purdue University. “Currently, the paint has the potential to cool the exterior of airplanes, cars, or trains. Airplanes parked on runways during hot summer days will not need to run air conditioning to cool the interior, saving a significant amount of energy. Spacecraft also need to be as light as possible, so this paint can be applied.”
The scientists indicated that they are discussing the commercialization of the paint and seeking patents for the technology. According to Ruan, in addition to saving money and energy, their paint also helps reduce greenhouse gases. Unlike many other cooling methods, this paint radiates all heat into deep space, directly cooling the Earth.
