The tensile strength observed in the initial period increases with increasing the elapsed time. From the results, it is noted that the initial elapsed time may lead to more intercrosslinking structure for the rigid structure of the epoxy/amine system. About after 4 weeks, the tensile strength decreases with the elapsed time. It is clearly considered that the tendency is shown by the chemical structure degradation derived from the abscission of polymer chains, the variation of crystallinity and the reduction in molecular weight. The similar observation is shown in initial decomposition temperature and activation energy for degradation, as measured by TGA.