This reflective paint could keep sunbaked buildings cool

A new polymer-based paint that reflects nearly all incoming sunlight could help keep buildings, cars, airplanes and other sunbaked structures cool.

This polymer paint, described online September 27 in Science, can be applied to various surfaces, including plastics, metals and wood. It also could be fashioned into recyclable tarpaulins for covering homes, cars or other enclosed spaces.

Materials scientist Yuan Yang of Columbia University and colleagues made the heat-resistant paint using water, acetone and a polymer called poly(vinylidene fluoride-co-hexafluoropropene). When the paint dries, the evaporated acetone and water leave behind a polymer film riddled with air pockets. These tiny cavities, ranging from hundreds of nanometers to several micrometers across, reflect more than 96 percent of incoming sunlight. Other cool-roof white paints have been able to deflect only about 85 percent of sunshine.

The film’s porous structure also allows any heat the material does absorb to escape into the air more easily than it could from a solid polymer sheet, says study coauthor Nanfang Yu, an applied physicist at Columbia. In field tests, a coating of this polymer paint under a clear sky in Phoenix stayed about 6 degrees Celsius cooler than surrounding air.

Using the paint to create heat shields could curb the use of energy-intensive air conditioning systems that often require air-polluting coolants, as well as offer protection from heat waves to people who don’t have electricity in the first place (SN: 4/14/18, p. 18).