Curing Mechanism and Mechanical Properties of Al2O3/Cyanate Ester–Epoxy Composites

Bisphenol A epoxy resin (E51) and biscyanatophenylpropane (BCE) as polymer matrix and aluminum oxide (Al2O3, self-made by sol–gel method) as modification agent have been used to prepare two-phase Al2O3/E51–BCE composites for application in various fields. The curing process and kinetics of the system were determined by nonisothermal differential scanning calorimetry. The average apparent activation energy of the system calculated by the Kissinger and Ozawa methods was 67.8 kJ/mol. Scanning electron microscopy revealed that the interface between the Al2O3 phase and E51–BCE matrix phase was blurred and displayed mutual penetration. The fracture morphology of the Al2O3/E51–BCE composites exhibited ductile fracture. Al2O3 phase was uniformly dispersed in the matrix resin. The bending strength, bending modulus, and impact strength of the Al2O3/E51–BCE composites showed peak values of 172.3 MPa, 2.5 GPa, and 24.2 kJ/m2, being 24.4%, 19.1%, and 53.2% higher compared with the matrix resin, respectively, when the Al2O3 content was 3 wt.%.