LIFETIME PREDICTION FOR POLYMERS VIA THE TEMPERATURE OF INITIAL DECOMPOSITION

The temperature of initial decomposition T-id was determined from TG a nd DTG curves of mass loss during thermooxidative polymer decompositio n in an environmental air atmosphere. The values of T-id were applied for comparison of the thermal stabilities of several polymers, e.g. PC -A, PET, PET, PPO and PVC. Both the activation energies of initial dec omposition E-id and the preexponential terms A(id) of the Arrhenius eq uation were calculated by using the Kissinger approach. The initial ma ss loss is proposed as a criterion for calculation of the time to fail ure t(f) from the known values of E-id and A(id), and hence for a pred iction of the lifetime of polymer materials. The following thermal sta bility sequence was found for the investigated polymer materials: PC-A (st) > PC-A (nst) > PBT > PET > PPO > PVC (e) > PVC (c). The activati on energy of initial decomposition had a mean value of E-id=83 kJ mol( -1) for PC-A, PBT, PET and PPO, and E-id=73 kJ mol(-1) for the PVC sam ples. The calculated time to failure, t(f), for PC-A, PET and PVC unde r specified conditions was in reasonable agreement with published expe rimental data. The proposed parameters of thermal decomposition T-id, E-id and t(f), can be applied for the characterization and comparison of various polymer materials, and for a prediction of their lifetime.