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PMMA and PC undergo photochemical aging leading to a gradual loss of material transparency and appearance during service life, which is desired to reach 50 years or more. Available artificial weathering test methods are unable to distinguish materials in terms of the speed of aging in outdoor use as roof materials. In order to design an appropriate accelerated or time-compressed test method, the 'worst case' scenario of the respective climatic conditions must be found. Therefore, samples of PMMA and PC were exposed to artificial weathering tests using different climatic conditions in terms of relative humidity and surface wetness. In the case of PMMA, it was found that water accelerates the photo degradation enormously. The fastest aging occurred when liquid water and UV radiation acted simultaneously on the sample surface and the PMMA reached its highest water content during weathering. In the case of PC, it was found that both vapour and liquid water speed up the photoaging, similarly to PMMA. But differently from PMMA, the worst case scenario for PC proved to be weathering conditions with high relative humidity. A test method has to be able to run artificial weathering under the different moisture conditions which can occur in the field.
While artificial weathering is a long-established tool to investigate long-term behaviour of polymers at outdoor conditions, the use of chemiluminescence as a highly sensitive and broadly applicable sensor for the effected change is a recent addition. This combination of artificial weathering with chemiluminescence could already be successfully applied to differentiate and evaluate long-term stability of various real use polymeric building materials relatively to each other and promises to be a useful tool for a variety of other polymeric materials as well.