Improving the toughness of polycyanate ester by adding epoxy pre-polymer with different molecular weights

The toughness of polycyanate ester is improved by adding epoxy pre-polymer with varying molecular weights. The curing mechanism of epoxy prepolymer (PreEP) and cyanate ester (CE) is discussed based on differential scanning calorimeters and Fourier-transform infrared spectroscopy. The mechanical, phase separated structures and thermal properties of PreEP/CE are also evaluated. It is found that the molecular weight of PreEP can reach 1,800 when it is cured at 90°C for 45 min by using a set amount of polyetheramine. Meanwhile, by increasing the molecular weight of the prepolymer, the mechanical properties of PreEP/CE show increased first, and then decreased. 0.2 PreEP/CE has the highest bending strength and impact strength (105.8 MPa and 18.3 kJ·m −2 ). There are 26.7 and 114.5% higher than those of polycyanate ester, respectively. The tougher PreEP/CE is attributable to the phase-separated structures and the decrease in the cross-linked product (Oxazolidinone) in PreEP and CE. The method showed in this article provides a new way to improve the toughness properties of thermoset resin.