Tertiary-amine-free, non-planar, fluorine-containing tetrafunctional epoxy and its application as high performance matrix

Abstract N,N,N′,N′-tetraglycidyl-4,4′-diamino-diphenylmethane (TGDDM) is the most widely used epoxy matrix in aerospace/aircraft industries, however its cured product suffers from cyclization side reactions, inadequate toughness and water resistance, and relatively high dielectric constant, which are rooted in its amine-derived nature. In order to address those issues, a tertiary-amine-free, non-planar, fluorine-containing tetrafunctional epoxy (FCTE) was synthesized with high yield. When FCTE is mixed with DGEBA and cured with 4,4′-diaminodiphenylsulfone (DDS), the cured epoxy shows excellent balanced properties. At 20 wt% FCTE loading, the cured mixed epoxy shows a tensile strength and impact strength of 82.5 MPa and 30.5 kJ/m 2 , respectively, which are higher than those of TGDDM (76.5 MPa and 11.6 kJ/m 2 ). Molecular simulation, PALS measurement, and TMA characterization suggest that the improved mechanical properties could be related to the marginal side reactions and larger free volume. The introduced fluorine-containing units also lead to better water resistance and lower dielectric constant compared with TGDDM. Despite a marginal drop in T g , thermal degradation temperature is greatly improved. In addition, when FCTE is used as the matrix for a polyimide fiber reinforced composite, the interlaminar shear strength is also higher, making it a better candidate for preparing high temperature, light weight, and low-k composites.