ACCELERATED WEATHERING TESTS

Specimen:

Any shape, size up to 5” x 7” x 2”

Procedure:

Artificial weathering as defined by ASTM is:

The exposure of plastic to cyclic laboratory conditions involving changes in temperature, RH and 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. A variety of light sources are used to simulate the natural sunlight. The artificial light sources include carbon arc lamps, xenon arc lamps, fluorescent sun lamps, and mercury lamps. These light sources, except the fluorescent, are capable of generating a much higher intensity light than natural sunlight. In the same wavelength band, xenon arc lamps can be operated over a wide range from below peak sunlight to twice the sunlight levels. Quite often, a condensation apparatus is used to simulate the deterioration caused by sunlight and water as rain or dew. Modern instruments have direct specimen spray on the front and/or back side of the specimen.

Significance:

Most data on the aging of plastics are acquired through accelerated tests and actual outdoor exposure. The latter is a time-consuming method; accelerated tests are often used to expedite screening the samples with various combinations of additive levels and ratios. Though there is no precise correlation between artificial laboratory weathering and natural outdoor weathering the standard laboratory test conditions produce results which are in general agreement with data obtained from outdoor exposures. Moreover the conditions can be easily reproduced.