Volume 35, Issue 3 (May 2007)
Methodology of Lifetime Prediction
Two approaches for lifetime prediction in polymer aging are compared: the “simulation approach” and the “ideal approach.” The widely used “simulation approach,” based on the hypotheses which were never clearly formulated, consists of finding a set of exposure conditions such that accelerated aging leads to the same structural states as natural aging. Using simple kinetic models it is demonstrated, that in the general case it is impossible to obtain a “good simulation.” Anyhow, in this approach, the problem of the relationship between accelerated aging and natural lifetimes remains unresolved. The “ideal approach” uses nonempirical kinetic models, taking into account structural changes at all the pertinent scales, and also uses polymer physics to establish the link between the polymer structure and the property under consideration. An important characteristic of this approach is that the accelerated aging serves only to determine the model parameters.