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

• Published in: Polymer testing 2018-10, Vol.71, p.38-48
• Main Authors: Xing, An, Bao, Fei, Fu, Jianwei, Miao, Xuepei, Liu, Tuan, Zhai, Hongyi, Cao, Xingzhong, Meng, Yan, Li, Xiaoyu
• Format: Article
• Language: English
• Subjects: Aerospace industry; Diaminodiphenylsulfone; Dielectric constant; Dielectric properties; Epoxy resins; Fiber composites; Fluorine; Fluorine-containing; Impact strength; Interfacial shear strength; Mechanical properties; Mechanical property; Permittivity; Tetrafunctional epoxy; Thermal degradation; Thermal stability; Water resistance; Weight reduction
• ISSN: 0142-9418; 1873-2348
• DOI: 10.1016/j.polymertesting.2018.08.022

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/m2, respectively, which are higher than those of TGDDM (76.5 MPa and 11.6 kJ/m2). 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 Tg, 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. •Tertiary-amine-free, non-planar, fluorine-containing tetrafunctional epoxy was synthesized through a scalable procedure.•The tensile strength and impact strength of cured epoxy blends outperform TGDDM-the dominant matrix in aerospace/aircraft industry.•The water absorption and dielectric constant of cured epoxy are lower than TGDDM.•Cured epoxy blends show much higher thermal degradation temperature than TGDDM.•In a polyimide fiber reinforced composite, the interlaminar shear strength of epoxy is also higher than TGDDM.