In situ Phase-Separated Epoxy Network with High Tg and Fracture Toughness

초록

This study investigated an in situ phase-separated epoxy network exhibiting high glass transition temperature (Tg) and enhanced fracture toughness for aerospace composite applications. A disulfide-containing curing agent, 4,4′-dithiodianiline (4,4′-DTDA), was introduced into a tetraglycidyl-4,4′-diaminodiphenylmethane (TGDDM)/diaminodiphenyl sulfone (DDS) epoxy system. During curing, DTDA spontaneously aggregated to form a second phase, resulting in a phase-separated morphology. The optimal formulation-TGDDM with 3,3′-DDS and 4,4′-DTDA in a 7:3 ratio-achieved a fracture toughness of 2.0 MPa·m1/2 and a Tg of 237 °C, surpassing many conventional aerospace-grade epoxies. In contrast, the TGDDM/3,3′-DDS system without DTDA exhibited a higher Tg of 246 °C but significantly lower fracture toughness of 0.91 MPa·m1/2, indicating a 120% improvement in toughness with only a modest reduction in Tg. These findings highlight the potential of utilizing in situ phase separation via mixed curing agents to enhance both mechanical and thermal properties without external toughening agents.

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