Enhanced dielectric and mechanical properties of epoxy-cyanate ester resin by Al₂O₃ and OMMT

In order to achieve the purpose of simultaneously improving the mechanical properties and dielectric properties of biscyanatophenylpropane (BCE), a copolymer of bisphenol A epoxy resin (E51) and (BCE) was used as the matrix resin (E51-BCE), and Al₂O₃ with sol–gel method and the organically montmorillonite (OMMT) were used as the reinforcements to prepare the Al₂O₃/OMMT/E51-BCE composites. The structure of Al₂O₃ was identified to be γ-Al₂O₃ by X-ray diffraction (XRD) and transmission electron microscope (TEM), and MMT was organically modified by intercalation agent octadecyl trimethyl ammonium chloride (OTAC) to obtain OMMT and characterized by Fourier-transform infrared spectrometer (FT-IR), thermogravimetric analysis (TGA) and scanning electron microscope (SEM). The results showed that the interlayer spacing of OMMT (2.14 nm) was bigger than that of MMT (1.44 nm), with an increase of about 48.6%. The results indicated that both Al₂O₃ and OMMT can improve the dielectric properties and mechanical properties of the composite materials. The Al₂O₃/OMMT/E51-BCE composites are found to have the best performance; the bending strength, bending modulus and impact strength were 187.34 MPa, 3.59 GPa and 35.12 kJ m⁻², respectively, when the content of Al₂O₃ and OMMT are all 2 wt%. And the dielectric constant, dielectric loss tangent, breakdown strength and volume resistivity of the composites reached peak values of 3.4, 0.005, 19.53 kV mm⁻¹ and 8.9 × 10¹⁴ Ω m, respectively. The overall performance of the composite fulfilled the basic requirements of electrical and insulating materials and could expand application of BCE material in many areas.