Лако-красочные материалы — производство

A great deal of contention surrounds how best to accelerate the testing of products that will be exposed to daylight, and particularly to strong sunlight. Prior to the development of suitable equipment, samples were placed on a North-facing (so that they were not in direct sunlight) windowsill for however long was available for testing. However, quite variable results are obtained, depending on geographical location and season. Although such tests are often still conducted as a back-up, the availability of UV cabinets, such as the Hereaus Novasol Test®, has helped to standardize testing. The Xenon arc lamp subjects the samples to UV light in the 300-800 nm wavelength range and can run with a 400 or 1000 W burner fitted. Exposure of 6 h to the 1000 W lamp is usually sufficient to see any changes that are likely to occur in about 3 months of daylight testing. There are, however, considerable disadvantages to this method, including the fact that, despite the presence of a cooling fan, the temperature inside the cabinet can become quite hot, and thus two variables, rather than one, are being tested at once. Also, UV light is not a true reflection of normal daylight and it is possible for some discoloration reactions to occur in the first few hours and then bleach out again before the 6 h is complete. Thus, some companies now invest in new light stress chambers, which can be fully temperature controlled (between +10 and +50 °С) and can be run with simulated daylight bulbs (for real-time testing), UVA or UVB tubes or fluorescent light (to simulate in-store conditions).