As with wool and paper, while the UV-wavelengths cause yellowing of PVC the visible radiation >400 nm tend to cause photobleaching. Several possible photobleaching mechanisms are reported in the literature but the process is little understood. A second polymer used in building applications, mainly as glazing, is polycarbonate. Lots of pure plastics fail to absorb UV radiation, risking your project and its components. How to Avoid UV Degradation. You, avoid UV degradation in plastics by using blockers, stabilizers, or absorbers. Benzophenones and other organic compounds can also absorb UV light and emit it as heat.

The visible spectrum. Colours shown are of the light beam at the wavelengths on the scale so the colour the eye perceives of a reflectant object in ‘white’ light is that due to wavelengths that are not absorbed. Thus, the ‘green oxidase’ (cytochrome d) looks green but absorbs light in the blue and red regions of the spectrum.

The UV light is not good for skin (burns the skin) and therefore human skin exposed to sun produces pigments to absorb the light to protect the skin from burning. The produced pigments result in a colour change. Plastics: Plastics are one of the most drastically effected materials from sunlight. They may not only change colour but also lose Plastic degradation, as a result of UV light absorption, leads to discoloration, cracks, and loss of mechanical and physical properties [1,2]. Photooxidation resembles autooxidation due to long-term heat aging, except that the driving force is UV light and not heat . Therefore, during plastic manufacturing, measures should be taken to ensure When UV light is shone on a fluorescent material, the electrons in the atoms jump up at least two energy levels. Instead of falling straight back down to its original energy level and emitting a . 39 214 7 18 181 332 145 56 109

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