Ultraviolet light stabilization interactions

Difluoramino radicals combine with a variety of other radicals, with the product stability apparently directly related to the stability of the substrate radical. For instance, nitric oxide and NF2 form a compound, difluoronitrosamine, only at low temperatures (3) at room temperature and atmospheric pressure the two radicals do not interact. Chlorine and N2F4 react under the influence of ultraviolet light to produce chlorodifluoramine, CINF2 (13). The equilibrium reaction is favored by high concentrations of chlorine and by high temperature (80° C). Because of this unfavorable equilibrium, the reaction of difluoramine and boron trichloride provides a more satisfactory route to chlorodifluoramine (11). 

H. Takenaka, S. Mizokawa, and Y. Ohkatsu, Interaction of hindered amine light stabilizers and ultraviolet absorbers, J. Jpn. Petrol. Inst. 2007, 50, 8-15. 

Persistence is the net result of many interacting factors, but chemical properties of the pesticide can play a dominant role. Volatility, solubility, stability to ultraviolet irradiation, tendency to adsorb onto or dissolve into tissue surfaces, ease of hydrolysis, sensitivity to humidity, potentiality to polymerize with or without ultraviolet irradiation, possible isomerization or other molecular rearrangement are all important chemical properties which play a significant role in persistence. Weather conditions such as wind, rain, amount and intensity of light, air temperature, and humidity play important roles. Rainfall is usually con-... 

Color instability can be caused by many factors, such as the degradation of color additives or of another formula component through chemical interaction with formula components, with trace contaminants of components, or by ultraviolet radiation. This section is concerned with the latter problem involving stabilization of the system to light radiation. 

One common form of deterioration results from exposure to light [in particular, ultraviolet (UV) radiation]. Ultraviolet radiation interacts with and causes a severance of some of the covalent bonds along the molecular chains, which may also result in some crosslinking. There are two primary approaches to UV stabilization. The first is to add a UV-absorbent material, often as a thin layer at the surface. This essentially acts as a sunscreen and blocks out the UV radiation before it can penetrate into and damage the polymer. The second approach is to add materials that react with the bonds broken by UV radiation before they can participate in other reactions that lead to additional polymer damage. 

Polymers also require protection against the effect of light, heat, and oxygen in the air. In view of this, polymers are mixed with antioxidants and stabilizers in low concentrations (normally less than 1%). If the material does not have these compounds, a polymer molecule M of chain length n interacts with light (particularly the ultraviolet portion of the light) to produce polymer radicals... 

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