Assessing the Effects of Accelerated Weathering Stresses Used to Predict Service Life

Taking service-life prediction to the next level demands a better understanding of how the effects of accelerated weathering compare with results obtained under natural weathering conditions. Useful service-life estimates require that degradation pathways stemming from the two methods be the same. Potential deviation from this requirement is particularly an issue when accelerated testing is conducted at high levels of stress. Using vinyl and poly(ethylene terephthalate) films as model materials, the impact of irradiance, temperature, and humidity on degradation has been evaluated in a series of accelerated laboratory exposures. Results reveal multiple failure modes, each of which displays a unique dependence on the applied stresses. Comparison to degradation observed from natural outdoor exposures enables assessment of the limitations, determination of the constraints, and interpretation of the data relating to accelerated weathering, all of which must be considered for service-life prediction.