UV protecting agents

Aliphatic polyurethanes, with their nonyellowing, also provide sufficient impact resistance so that they can be used in face shields (U.S. Patent 3.866.242). Even with the nonyellowing properties, UV protection agents are often added to materials. 

UV protection agents prevent photo- -c oxidative degradation. . organics, metallic f cdmplexe.s, inorganic pigments ... 

Various materials have been used to avoid damage to packaged commodities and, in some cases, the package by atmospheric oxygen. An obvious example, as mentioned previously, is the use of UV protective agents in the protection of vitamin C containing drinks. 

The chromophores are yellow and act as uv screening agents. The reactions occur at surfaces and uv penetration is avoided. Mechanical properties are thereby protected (47). 

Polypropylene resists hydrolysis well but is naturally sensitive to light and UV. It must be protected by addition of anti-UV and other protective agents or by 2-3% of a suitable carbon black. 

EVAs are naturally resistant to light, UV, ozone and weathering and, even more, they can be protected by addition of specific anti-UV and other protective agents. Under identical... 

PVC resists hydrolysis well but is naturally sensitive to light and UV. It must be protected by addition of anti-UV and other protective agents. In these cases, long warranty periods can be allowed, for example ten years and more. For a white, protected, rigid PVC, after natural weathering for 3 years in Michigan, the retention of impact strength is 68% and the yellowness index increases by 5. 

Polyamide 11 and 12 must be protected by addition of anti-UV and other protective agents. 

The weathering resistance is one of the most interesting features of PMMA, along with its transparency. PMMA is inherently UV resistant and this characteristic can be further improved by addition of protective agents. 

Other compounds such as phlorotannins, sporopollenin, coumarins, tridentatols, polyphenolics, and several as yet unidentified substances (e.g., P380) have also been implicated as UV protectants that can increase UV tolerance.57-63 With the rapidly accelerating rate of research in the area of aquatic UV photobiology, it is highly likely that additional new types of UV-screening compounds will continue to be discovered. Many of these secondary metabolites probably have multiple protective functions. For example, tridentatols serve as allelopathic agents, antioxidants, and sunscreens.57,58,64... 

One section of his thesis gives examples of the use of pigments, UV-absorbers and suspended pigments as photo protective agents. 

Both the acetal and the aldehyde can be used as intermediates for crop protection agents, fragrances, plating additives, ultraviolet (UV) absorbers, optical brighteneres, and other applications. 

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