The change of thermal-mechanical properties and chemical structure of ambient cured DGEBA/TEPA under accelerated thermo-oxidative aging

The thermal-mechanical properties and chemical structure of ambient cured DGEBA/TEPA during thermo-oxidative aging were investigated in this paper. Results from Differential Scanning Calorimetry (DSC) experiments revealed that it was difficult for this ambient cured DGEBA/TEPA system to cure completely even after a long period. Dynamic Mechanical Thermal Analysis (DMTA) curves demonstrated a post-cure reaction occurred in the early period of aging and then an additional transition peak emerged at a lower temperature, whose intensity increased with the aging time. FTIR Spectroscopy showed that the O-H and CH2 groups were oxidized to carbonyl groups and the main chains were degraded to the lower molecular weight compounds during thermo-oxidative aging process. The additional peak in DMTA curves are related to these lower molecule weight compounds. X-ray Photoelectron Spectroscopy (XPS) results further manifested that the formation of the additional peak derived from the degradation of main chains near the surface in the sample and the effect of oxidation increased with decreasing depth.