Comparative statistical studies of aging models for polypropylene films

Accelerated aging experiments are conducted to investigate the effects of continuous thermal aging on the DC electrical lifetimes of capacitor grade biaxially-oriented isotactic polypropylene film. Statistical analysis of the lifetime data includes assessment of possible underlying parametric distributions such as the 2-parameter Weibull (weakest link time-to-failure) and the lognormal (cumulative damage time-to-failure) distributions via graphical, analytical and residual analysis. Parametric and nonparametric methods are used. The mean life is fitted into semi-empirical (quasi-theoretical) models available in the literature to describe the behavior of the film within the stress range tested. Multiple-linear regression is used to compute parameters of the life-stress models. A thorough regression analysis including goodness of fit measures such as (χ² and R²) is carried out using the SAS package