Effects of the content 4,4′-diaminodiphenyl methane on thermomechanical properties of shape-memory epoxy polymers

A series of thermosetting shape memory epoxy polymers (SMEPs) were prepared using the epoxy resin diglycidyl ether bisphenol A E-51 with varying content of curing agent 4,4′-diaminodiphenyl methane (DDM). The chemical, thermal and mechanical properties of the SMEPs were systematically investigated via Fourier transform infrared spectroscopy, differential scanning calorimetry, dynamic and static mechanical analysis, and thermogravimetric analysis. The results indicate that the shape-memory temperature (Tg) of the SMEPs varies within the range of 33.9 °C to 140.0 °C with DDM content increasing from 12% to 25%, and the Tg values exhibit a good linear correlation, with a correlation coefficient of more than 0.999. This indicates that SMEPs with tunable shape-memory temperatures can be realized by controlling the content of the curing agent. When the DDM content is 17–19%, the shape fixity and shape recovery ratio of the SMEPs reaches approximately 100%. In addition, the shape recovery time decreases as temperature increases. This work also highlights the effect of DDM curing agent content on the thermal, mechanical and shape-memory properties of SMEPs, and it is in favor of extending their further applications.