Preparation, dielectric and thermomechanical properties of a novel epoxy resin system cured at room temperature

A new kind of bisphenol A-type epoxy resin (E51) system cured at room temperature was prepared using ether bond- and fluorine-containing aromatic diamine, including 4,4′-(Hexafluoroisopropylidene)bis(p-phenyleneoxy)dianiline (HFBAPP) and 2,2-Bis[4-(4-aminophenoxy)phenyl]propane (BAPP), and acrylic acid (HAA) as hardeners. The curing behavior of epoxy resin was investigated by differential scanning calorimetry (DSC) and Fourier transform infrared (FTIR) Spectroscopy. The thermal properties, dynamic thermomechanical properties, tensile properties, and dielectric properties of the cured epoxy resin at room temperature were evaluated with thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA), universal tensile testing machine, and vector network analyzer, respectively. The surface morphology of the tensile fracture specimen was observed by scanning electron microscope (SEM). The results showed that the curing reaction for this kind of epoxy resin system can be conducted at room temperature without external heating. Compared to BAPP and 4,4′-Diaminodiphenyl methane (DDM), the cured E51/HFBAPP + HAA system demonstrated the best comprehensive properties, such as high thermal stability, high glass transition temperature and storage modulus, high tensile strength and modulus, and low dielectric constant and dielectric loss values at 2–18.3 GHz, which are mainly attributed to the introduction of flexible ether bonds and CF₃ groups into crosslinked epoxy network. SEM testing confirmed that E51/HFBAPP + HAA and E51/BAPP + HAA systems displayed good toughness.