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How to Test Plastic Properties
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; 2) open flame sunshine carbon arc; and 3) water cooled xenon arc.
Because weather varies from day to day, year to year, and place to place, no precise correlation exists between artificial laboratory weathering and natural outdoor weathering. However, standard laboratory test conditions produce results with acceptable reproducibility and which are in general agreement with data obtained from outdoor exposures. Fairly rapid indications of weatherability are therefore obtainable on samples of known plastics which through testing experience over a period of time, have general correlations established. There is no artificial substitute for predicting outdoor weatherability on plastics with no previous outdoor history. ASTM E-42.