Degradation studies solar radiation

A further restriction on possible reactions is imposed by the elementary photochemical principle that light must be absorbed by the polymer if a reaction is to occur. However, most pure polymers do not absorb at wavelengths longer than 300 nm, and hence should not be affected by solar radiation. However, most polymers degrade when subjected to solar radiation, and this has been attributed to the presence of small amounts of internal and/or external impurities which absorb light and initiate oxidative chain reactions within the polymer. A detailed study of such reactions is difficult because of the frequently unknown nature of the trace impurities which initiate the reactions and of the multiplicity of products formed in the photo-oxidative degradation (cf. section 2.21). 

Most natural and accelerated outdoor weathering tests in the United States are carried out in either (or both) south Florida or central Arizona. These have the two most important benchmark environments where materials typically fail fastest because of intensification of the weather elements responsible for degradation. South Florida has a subtropical climate with higher levels of the three critical weathering factors, solar radiation, temperature, and moisture, than are present in most end-use environments. The climate is particularly destructive to materials sensitive to moisture. A number of studies have shown that the south Florida climate has a twofold or higher weathering rate for coatings compared to... 

Because of UV filters are substances designed to absorb solar energy, photolysis and photocatalysis have been tested as a feasible treatment to degrade the recalcitrant compounds. To date, very few studies have examined UV filters response under UV radiation when exposed in aqueous samples [41-44], Results indicate that the extent of degradation is quite variable, from no photodegradation of BP3 to complete mineralization of BP1 after 24 h of UV light irradiation. 

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