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topic 17984

UV Test vs. Real Life Exposure


2002

I read you can not relate the results of a salt spray test to the real life. Can we say the same thing for a UV-test (exposure to UV light)?

Jan Robeyns
- Landen, Limburg, Belgium


2002

To answer the question of correlation one should have following facts in mind:

-UV-tests are normally performed in Fluorescent UV Devices using Fluorescent UV lamps.These sources with specific spectral distributions (SPD's) are incorporated into fluorescent UV condensation devices.
-These devices may be used in tests that vary light/dark cycles, temperature,condensing humidity,water sprays, and irradiance control.

Their functional design and use is primarily governed by
ISO 4892-3 [link by ed. to spec at TechStreet], Plastics,-Methods of Exposure to Laboratory Light Sources-Fluorescent UV-Lamps;
ISO 11507 [link by ed. to spec at TechStreet], Paints and Varnishes-Exposure of Coatings to Artificial Weathering-Exposure to Fluorescent UV and Water; and
ASTM G154 [link by ed. to spec at TechStreet], Standard Practice for Operating Fluorescent Light Apparatus for UV Exposure of Nonmetallic Materials.

-There are several different types of Fluorescent UV lamps that have unique spectral characteristics.Fluorescent UV-B lamps (F40 and UVB-313) with a peak around 313 nm, have nearly all of their energy concentrated between 280 and 360 nm. A large percentage is at wavelengths shorter than what is present in natural sunlight.There is very little radiation with wavelengths longer than 360 nm.Reversals in the stability ranking of materials have often been reported between laboratory accelerated and outdoor tests when the accelerated test uses UVB-lamps.This occurs because of the large amount of short wavelength UV and the lack of long wavelength UV and visible radiation;the mechanisms of degradation may be significantly different from those of the "natural" tests.
-Fluorescent black lights, referred to us UVA-lamps, are available with peak emissions of 340 nm-370 nm(e.g.UVA-340 and UVA-351). In the UVA-340 lamp,the short wavelength irradiance simulates that of direct solar radiation below 325 nm.
-because UV-A lamps do not emit radiation below the cut-on of natural sunlight,correlation with outdoor weathering is somewhat improved,but test times are longer than with UV-B lamps.These tests are useful for relative rank comparisons between materials under specific conditions, but the comparison to service lifetime performance or correlation to outdoor exposures may not be valid.
-The best use of the UV lamps is for general screening tests, such as checking for gross formulation errors with an artificially harsh exposure.

Bruno Bentjerodt
ATLAS MTT GmbH - Linsengericht, Altenhaßlau, Germany


February 5, 2010

Dear Sirs

in my research we happen to operate a SUNTEST XXL+ by ATLAS. I am about to commence my first test on polymeric insulators. After reading the ISO 4892-2 [link by ed. to spec at TechStreet] regarding xenon-arc lamps I have a quite simple question : how much time of natural exposure is simulated by i.e cycle 1 of Method A (100 mins dry, 18 mins water spray, 300 nm - 400 nm. 60 W/m^2) or if there is any other equivalence table.

Thank you very much.

Panagiotis Charalampidis
- UK



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