Reflective paint can keep buildings cool in the sun

A new polymer coating that reflects sunlight to control heat can supplement or replace air conditioning systems, thus saving electricity.

A new polymer-based paint reflects almost all the sunshine, so that buildings, cars, airplanes and sun-exposed buildings are generally cool.

This paint can be applied to many different surfaces.

This polime paint, introduced online September 27 in Science, can be applied to a variety of surfaces, including plastic, metal and wood. It can also be made into recyclable tarpaulins to cover houses, cars or other enclosed spaces.

Yuan Yang, a materials scientist from Columbia University and colleagues, created this heat-resistant paint using water, acetone and a polymer called poly (vinylidene fluoride-co-hexafluoropropene) . When dry paint, acetone and evaporated water leave a layer of polymer film screened with air bags.

These tiny holes, diameter from a few hundred nanometers to a few micrometres, reflect more than 96 percent of the sun. Other coolant white paints can only refract about 85% of the sun.

The coatings of this new polymer paint have nanoscale or micro holes, refracting more than 96% of the sun shining down - (Photos from J. Mandal et al / Science 2018).

Study co-author Nanfang Yu, an applied physicist at Columbia, said the multi-hole structure of the membrane also allows the heat that the absorbent material escapes into the air more easily than a plate. hard polymer. In field tests, a layer of this polymer coating under the clear blue sky of Phoenix maintains a temperature of about 6 degrees Celsius lower than the ambient air.

Using this type of paint to create thermal shields that can limit the use of energy-intensive air conditioning systems often requires coolants that pollute the air, as well as providing protection from heat waves for people who don't have electricity from the beginning.