20 января, 2016 
Pokraskin Coatings for exterior applications, such as automotive coatings, are subjected to severe weathering, causing degradation of coating binders. The primary damaging components of weather are light (especially UV radiation) and oxygen, though other factors such as moisture, fluctuations in temperature and acid rain also influence damage to some degree. UV radiation has sufficiently high energy to cause photooxidative degradation of some polymers as well as fading of several pigments. Photooxidative scission of long, tough polymer chains occurs via radical generation, and formation and
decomposition of peroxides transforms them into small fragments. The result of this degradation is chalking, embrittlement, cracking, delamination, flaking, loss of gloss and drift in color.
The resistance of a coating to weathering is mainly driven by type of binder and presence of pigments in the film. Not all pigments are good UV absorbers, nor is every coating pigmented (such as automotive clear coats). Therefore, certain additives known as light stabilizers are often added to exterior coatings to improve performance of the coating in exterior conditions. It is possible to stabilize polymers against photodegradation in two ways:
• Prevention of radical formation by competitive UV absorption (filtration of UV) from added UV absorbers
• Trapping of the generated radicals before they are involved in polymer degradation reactions by using radical scavengers.
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