Facile Synthesis of Bio‐Based Methyl Oleate‐Modified Amine as a Flexible Curing Agent for Toughened and Strengthened Epoxy Thermosets

To enhance the flexibility and strength of epoxy thermosets, methyl oleate modified amine (MOMA) was synthesized as a bio‐based curing agent via a one‐pot reaction of inexpensive and readily available methyl oleate (MO) and diethylenetriamine (DETA). The tensile and impact strengths of the cured thermosets first increased and then decreased as the MOMA/DGEBA ratio rose from 40/100 to 55/100. At the optimal ratio of 50/100, they peaked at 82.7 MPa and 37.5 kJ·m −2 , representing improvements of 39.5% and 91.3% over the conventional DETA/DGEBA system, respectively. DMA showed MOMA reduced the thermosets' Tg (178.9°C–106.0°C) and storage modulus (3117–2594 MPa). This indicates its flexible fatty chain effectively enhances chain mobility and reduces stiffness, thus toughening the material. SEM revealed that MOMA's flexible fatty chain enhanced crack blunting, thereby improving toughness. TGA showed comparable thermal stability between MOMA‐ and DETA‐cured thermosets from 40°C to 350°C, with a slight decrease at 350°C–700°C. In summary, this work offers a high‐performance bio‐based flexible curing agent synthesized via a facile, mild‐condition route.