This practice determines the effects of actinic radiation, elevated temperature, and moisture on sealants and their constituents under controlled laboratory artificial weather test conditions.
When conducting exposures in devices which use laboratory light sources, it is important to consider (1) how well the artificial test conditions will reproduce property changes and failure modes caused by end-use environments on the sealant being tested and (2) the stability ranking of sealants. Refer to Practice G151 for full cautionary guidance regarding laboratory weathering.
Because of differences in the spectral power distributions of the exposure sources (xenon arc, fluorescent UV lamps, and open flame carbon arc), as well as other conditions used in the three types of laboratory weathering tests, including temperature, type and amount of moisture, and test cycles, these three procedures may not result in the same performance ranking or types of failure modes of sealants. Further, different exposure durations may be required for testing the weathering performance of sealants by the three types of exposures. Comparisons should not be made of the relative stability of sealants exposed in the different types of apparatus.
Variations in results may 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 a report of the specific operating conditions as required in Section 10. Refer to Practice G151 for detailed information on the caveats applicable to use of results obtained according to this practice.
No laboratory exposure test can be specified as a total simulation of actual use conditions in outdoor environments. The relative durability of materials in actual use conditions can vary in different locations because of differences in UV radiation, time of wetness, relative humidity, temperature, pollutants, and other factors. Results obtained from these laboratory accelerated exposures can be considered as representative of actual use exposures only when the degree of rank correlation has been established for the specific materials being tested and when the failure mode is the same. Exposure of a similar material of known outdoor performance, a control, along with the test specimens provides for evaluation in terms of relative durability under the test conditions, which also greatly improves the agreement in test results among different laboratories.
The acceleration factor relating the exposure time in a laboratory accelerated test to exposure time outdoors required to produce equivalent degradation is material dependent and can be significantly different for each material and for different formulations of the same material. Therefore, the acceleration factor determined for one material cannot be assumed to be applicable to other materials.
Results of this procedure will depend on the care that is taken to operate the equipment according to Practices G152, G154, and G155. Significant factors include regulation of the line voltage, freedom from salt or other deposits from water, temperature control, humidity control, where applicable, condition and age of the burners and filters in xenon arc equipment, and age of lamps in fluorescent UV equipment.
Note 18212;Additional information on sources of variability and on strategies f.......
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