BRIDGING THE PE LIFETIME UNDER FATIGUE AND CREEP CONDITIONS WITH ITS CRYSTALLIZATION BEHAVIOR

The service lifetime for several linear polyethylene copolymers was st udied by fatigue-type accelerated tests. The material morphology and c rystallization behavior were correlated with the lifetime and the fail ure modes. The correlation is based on the rate constant of material d egradation (RCMD) recently introduced by the authors within a mathemat ical model for crack layer growth kinetics. RCMD is found to depend on the loading conditions (e.g., creep or fatigue) and on material morph ology reflected in crystallization kinetics. The ratio of RCMDs for fa tigue and creep is a scaling factor that allows one to correlate fatig ue and creep lifetimes. The dependence of the RCMD's ratio on the morp hological features associated with the primary and secondary crystalli zation kinetics is also reported in this paper. (C) 1993 John Wiley & Sons, Inc.