4.1 Materials made from photodegradable plastics are intended to deteriorate rapidly when exposed to solar radiation, oxygen, heat, moisture and other degrading elements of the weather. This practice is used for evaluating the photodegradability of plastics when exposed in an apparatus that produces simulated daylight (1,2)⁶ and controlled temperature and moisture. The exposure used in this practice is not intended to simulate the deterioration caused by localized weather phenomena such as atmospheric pollution, biological attack, and salt water exposure. There can be no positive correlation of exposure results between this and other laboratory weathering devices.

4.2 Variations in results can be expected when operating conditions are varied within the accepted limits of this practice. Therefore, all test results using this practice must be accompanied by the specific operating conditions required in Section 9. Refer to Practice G151 for detailed information on the caveats applicable to use of results obtained in accordance with this practice.

4.3 The results of laboratory exposure cannot be directly extrapolated to estimate absolute rate of deterioration by the environment because the acceleration factor is material dependent and can be significantly different for each material and for different formulations of the same material. However, exposure of a similar material of known outdoor performance, a control, at the same time as the test specimens allows comparison of the durability relative to that of the control under the test conditions. Evaluation in terms of relative durabilities also greatly improves the agreement in test results among different laboratories (3).

4.4 Test results will depend on the care that is taken to operate the equipment in accordance with Practice G155. Significant factors include regulation of line voltage, freedom from salt or other deposits from water, temperature and humidity control and condition and age of the burners and filters.

Note 2-Additional information on sources of variability and on strategies for addressing variability in the design, execution and data analysis of laboratory accelerated exposure tests is found in Guide G141.

4.5 Before proceeding with this practice, it is common practice to reference the specifications of the material being tested. Any test specimen preparation, conditioning, dimensions, or testing parameters, or combination thereof, covered in the material specification shall take precedence over those mentioned in this practice. If there are no material specifications, then the default conditions apply.