The UV radiation component of sunlight is very harsh on polymers. Heat caused by the infra red component will degrade and even physically distort a product. Combined with rain and humidity, a chemical change (oxidation) or breakdown can occur. This then leads to lower strength, loss of color (fading), distortion and corrosion.
The effects of sunlight on the atmosphere in conjunction with emissions from man and his industries results in everything from acid corrosion to ozone breakdown of materials and products.
Tests that fall under such exposures include:
QUV & UVCon ASTM G53, G154 SAE 2020
Weatherometer – Xenon C135, ASTM G15, G26 SAE T885
UV @ 264mm – Automotive / Electronics spec
Mil Spec 810 E,F,G Procedures I & II
Indoor Fluorescent exposures