Solar Radiation
Physical changes resulting from exposure to the environment are initiated by chemical bond breaking reactions caused by the absorbed light, either through direct or indirect processes. Chemical bond breaking is a prerequisite to any chemical reaction, and chemical reactions are a prerequisite to observable or measurable physical changes. Other weather factors mainly promote weathering through their influence on the secondary reactions which follow the breaking of bonds. Degradation of most materials exposed to outdoor conditions is caused mainly by UV degradation -- the ultraviolet portion of solar energy, with the shortest wavelengths often having the greatest effect. Therefore, variations in both the quantity and quality of ultraviolet in both the direct solar beam and diffuse sky radiation are important factors in the design and evaluation of weathering tests.
Read more about this topic: Factors Of Polymer Weathering
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