A new durable, environmentally-benign (we all hope) blue pigment has also been found to have unusual characteristics in reflecting heat - it's much better at it than most blue pigments in use. The compound just received patent approval and was discovered by Oregon State University scientists who were instead studying some materials for their electrical properties.
Some manganese compounds came out of a 2,000 degree Fahrenheit oven transformed into a blue color, which researchers later determined was due to an unusual "trigonal bipyramidal coordination" of their molecules that changed when exposed to extreme heat. It also turned out to have infrared heat reflectivity of about 40 percent, which is significantly higher than most blue pigments now being used. Its potential use to help reduce heat absorption on the roofs and walls of buildings – an area of considerable interest in warm regions where cooling is a major expense.
"Cool roofing," in which paints are used to reflect the sun's heat and thereby reduce cooling costs, is a new trend in energy efficiency and "green" construction,. Such reflective coatings, it is said, also have less thermal degradation, reduce the "heat island" effect in cities, lower peak energy demand, and reduce air pollution due to lower energy use and power plant emissions.
In general, any darker color of the type often used for roofs, houses, automobiles or other applications will tend to absorb more heat. But some compounds, like this one discovered at OSU, have dark tones but also the ability to reflect heat in the infrared spectrum, which is responsible for most of the heat energy absorbed from sunlight.
"The more we discover about the pigment, the more interesting it gets," said Mas Subramanian, an OSU professor of chemistry who discovered the compound."We already knew it had advantages of being more durable, safe and fairly easy to produce. Now it also appears to be a new candidate for energy efficiency."
They say their material is probably the best blue pigment humans have produced since ancient times – going back to efforts by the Egyptians, the Han dynasty in China and Mayan cultures. Blue pigments have been sought through history but often had serious drawbacks, such as decaying quickly, being toxic, costly or carcinogenic.
The research was funded by the National Science Foundation, but since the OSU group got a patent for it, you'll have to pay if you want to get it into the commercial sector.
Cool Blue Manganese Compound Has 40 Percent Heat Reflectivity