Weathering of polymer blends

The sunshine carbon arc is also being progressively phased out of international test specifications but is still widely used in industry for company specifications. It s output is closer to that of sunhght than the enclosed version, but it still has significant differences, in particular being more intense in the 350-450 nm region and less intense below 350 nm. 

These sources are much cheaper to operate than a xenon arc and do not produce any unwanted heat. The tubes are available with different spectral outputs, the most common being UV and UV bulbs. The UV spectrum has a peak intensity around 313 nm, with a high intensity at wavelengths below the solar cut off (i.e., 270-290 nm). The consequence of this is that they provide strong acceleration, but they are also likely to induce unnatural chemical reactions. UV bulbs 

The correlation of these artificial test results with natural weathering is often poor particularly for colored materials due to differences in the visible region, although it is generally differences in the UV region which are most likely to cause deviation. 

There are a number of exposure sites around the world each with a different chmates, which can be used for the purpose of predicting the exterior durability of materials. The site chosen should be the one, which is most representative of the general environment of interest, however, it is more common to choose sites of extreme chmates. In this way natural exposure is achieved, even though the UV, temperature and humidity levels may be vastly different from those met in service. 

Southern Florida with its high levels of UV radiation, humidity and temperature provides 

---