Nano tungsten trioxide has photochromic effect so that it may be applied for manufacturing heat insulation masterbatch with the characteristics of high thermal insulation, high visible light transmittance, and weather resistance. And therefore, this type of heat insulation material has an ultraviolet shielding rate of 99% and an infrared shielding rate (760-2500nm) of 99%. Speaking of photochromism, what you may have known is the two leap developments in photochromism.
Two leap developments in photochromism: In the sixty to seventy years after 1899, there were few reports on photochromism except that some studies on the reversible changes in the color of several compounds under the influence of light. And the phenomenon of photochromism has not attracted people's attention. The first leap in the development of photochromism began in the 1940s. In order to reveal the mechanism of photochromic reaction, the structure of products and the formation of reactive intermediates, a great deal of research has been conducted on cis-trans isomerization reactions of styrene, azo dyes, and the like. In the 50s and 60s, the development of photochromism saw a second leap due to the discovery of photochromic systems such as spiropyran, fulgatured acid, and anhydride. During this period, research on photochromic materials mainly centered on military and commercial interests, such as photochromic camouflage materials, photochromic printed boards, and printed circuits.
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