According to foreign media reports, in many parts of the world, especially in developing countries, air conditioning is neither practical nor affordable for people there. For this reason, they often paint the roof of a building to reflect sunlight. Keep the building cool. This is a method called passive daytime radiant cooling. Now, a new paint-like polymer can make this method more effective.
The problem with traditional white paints is that they usually contain UV-absorbing pigments that are not good at reflecting longer wavelengths of the sun. A team from Columbia University has developed a material that does not contain this pigment, and this The porous material also utilizes a very small air bag.
These are produced by a process consisting of a clear solution of polymer, solvent and water, which is then applied to a surface – this surface can be the roof, the exterior of the building, the water tank or any other that needs to be kept cool. Things. As the solvent evaporates, water forms small droplets of water in the polymer. Once the water evaporates, it leaves behind tiny pores (as shown below) that give the polymer a bright white color.
Because of their different refractive indices from the surrounding polymer, all wavelengths of sunlight are effectively scattered and reflected by these voids. In field tests, the polymer coating can reflect more than 96% of incident sunlight, thereby minimizing solar heating. In addition, this material also exhibits a high thermal emissivity, which emits about 97% of the heat to the sky.
In the Arizona desert climate test, this coating can reduce the temperature by 6 degrees Celsius and 3 degrees Celsius in the tropical climate of Bangladesh.
If the user does not want to paint everything in white, then a color dye can be added to the polymer, and the polymer still retains its reflective properties to a large extent. Although scientists have used polyvinylidene fluoride-six Fluoropropylene copolymer (P(VdF-HFP)HP) polymer, but in fact many other polymers can also make this coating, which allows manufacturers to maximize eco-friendliness and bio-phase Capacitance and other factors.
Yuan Yang, the chief scientist of the study, said that now is a critical moment to develop promising solutions for sustainable human development, and they are very happy with the progress that has been found so far.
Related research reports have been published in Science.
