Fluorine-containing main-chain type active esters as curing agents for epoxy resins to achieve superior dielectric and thermal performances

Abstract

Epoxy resins cured with active ester exhibited excellent dielectric properties but had deficiencies in thermal performance. To address this issue, this study synthesized three fluorine-containing main-chain type active ester curing agents (AE-1, AE-2, and AE-3) with bisphenol AF, isophthaloyl chloride and benzoyl chloride as raw materials. The effects of these active ester curing agents with different polymerization degree on the properties of dicyclopentadiene (DCPD) epoxy resins were investigated. Compared to the DCPD epoxy cured with AE-1，the DCPD epoxy cured with AE-3 which had high polymerization degree exhibited superior thermomechanical properties, thermal stability, and mechanical properties. Specifically, its glass transition temperature (T_g) measured by DMA (T_g -DMA) increased from 177 °C to 188 °C, T_g measured by TMA (T_g -TMA) increased from 130 °C to 149 °C, its 5 % mass loss temperature (T_d5%) rose from 336 °C to 359 °C, and the tensile strength improved from 38.5 MPa to 84.4 MPa. At 10 GHz, DCPD/AE-3 maintained excellent dielectric properties, with dielectric constant (D_k) and dissipation factor (D_f) values of 2.76 and 7.36 ‰, respectively. Epoxy resins cured with fluorine-containing main-chain type active ester exhibited excellent thermomechanical properties, mechanical properties, and hydrophobic properties while maintaining superior dielectric properties, broadening its application in packaging materials.