Weathering, artificial

An appraisal of artificial weathering methods was given in a report by Hoey and Hipwood who described the effectiveness of various weatherometer tests such as are described in BS 3900 Part F3 and ASTM 42 1964 (now ASTM G23 1989). Although these tests simulate atmospheric exposure it is not possible to obtain a direct correlation owing to variation in outdoor exposure conditions from place to place, but they serve a very useful purpose in providing a preliminary sorting of paints that can then be tested in the field. 

Specification for electroplated coatings of 65/35 tin/nickel alloy Method for the evaluation of results of accelerated corrosion tests on metallic coatings Methods of test for paints Cross-cut test Pull-off test for adhesion Resistance to artificial weathering (enclosed carbon arc) and Addendum No. 1 Resistance to continuous salt spray Notes for guidance on the conduct of natural weathering test... 

The specimen may be any shape. Artificial weathering has been defined by ASTM as The exposure of plastics to cyclic laboratory conditions involving changes in temperature, relative humidity, and ultraviolet (UV) radiant energy, with or without direct water spray, in an attempt to produce changes in the material similar to those observed after long-term continuous outdoor exposure. ... 

Three types of light sources for artificial weathering are in common use (1) enclosed UV carbon arc [7.5 UV energy output, approx. (x sunlight)], (2) open-flame sunshine carbon, and (3) water-cooled xenon arc. Selection of the light source involves many conditions and circumstances, such as the type of material being tested, product service conditions, previous testing experience, or the type of information desired. 

In calculating exposure times, adjustment needs to be made for light/dark cycles in artificial weathering apparatus. 

For trials involving exposure to heat, liquid chemical, environmental stress cracking and artificial weathering, attention is drawn to ISO 11403 [3], Acquisition and presentation of comparable multipoint data - Environmental influences on properties. 

Comparing accelerated results carried out in different laboratories with different apparatus (particularly for artificial weathering) is not dissimilar because of the large differences which are often found because of poor reproducibility. It is always advantageous to include a known reference material if one is available. Differences are generally much reduced if the ranking of material is considered rather than absolute values. 

Figure 12.3 Examples of the weathering performance of (a) a stabilised HDPE nonwoven and (b) a polyamide/polyester nonwoven deliberately unstabilised against ultraviolet radiation. Both were exposed to artificial weathering using three different types of apparatus and to natural weathering in two locations. All results are plotted against radiant exposure (total ultraviolet light energy...

Ayadi, N., Lejeune, F., Charrier, F., Charrier, B. and Merlin, A. (2003). Color stability of heat-treated wood during artificial weathering. Holz als Roh- und Werkstojf, 61(3), 221-226. 

Artificial Weathering Tests. Progress in this area has been achieved as chemists increased their understanding of the degradation mechanisms of polymeric systems. 

Artificial weathering tests in climatic chambers in accordance with the following specifications ... 

Furthermore, artificial weathering of coal under carefully controlled conditions in the laboratory reveals a rapid loss of thermally extractable mobile... 

Weathering in a simulated environment is termed artificial weathering. 

Warren, C. J. Dudas, M. J. 1986. Mobilization and Attenuation of Trace Elements in Artificially Weathered Fly Ash. Electric Power Research Institute Report, EA-4747, Palo Alto, CA. 

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