A SHORT METHOD OF ESTIMATING LIFETIME OF POLYPROPYLENE FILM USING STEP-STRESS TESTS

Polypropylene films were tested for lifetimes under high electric fields, using both constant and step-stress methods. Various time intervals for the step-stress test, and voltages for the constant stress test were selected. The inverse power law was used in the analysis of the experimental data, with the value of power exponent determined form the step-stress test. This exponent was found similar to that obtained from the constant stress test. The lifetimes of polypropylene were then estimated from the step-stress test, and were found to show good agreement with the experimental results of constant stress test. The Weibull distribution was employed in the analysis of the experimental data.