Lifetime prediction for polymers via the temperature of initial decomposition

The temperature of initial decomposition T-id was determined from TG and DTG curves of mass loss during thermooxidative polymer decomposition 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 decomposition E-id and the preexponential terms A(id) of the Arrhenius equation were calculated by using the Kissinger approach. The initial mass loss is proposed as a criterion for calculation of the time to failure t(f) from the known values of E-id and A(id), and hence for a prediction of the lifetime of polymer materials. The following thermal stability sequence was found for the investigated polymer materials: PC-A (st) > PC-A (nst) > PBT > PET > PPO > PVC (e) > PVC (c). The activation 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 samples. The calculated time to failure, t(f), for PC-A, PET and PVC under specified conditions was in reasonable agreement with published experimental 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.