Thermal and mechanical properties of epoxy blends with a dicyanate ester containing a quinoline moiety

Abstract

Dicyanate esters (CE) with a quinoline moiety were synthesized by treating bisphenols with cyanogen bromide in the presence of triethylamine and the structures were confirmed by FT-IR, and NMR spectral studies. The curing of the dicyanate esters was carried out by a conventional heating method and the curing mechanism has been investigated using FT-IR. The maximum curing temperatures of these cyanate esters are found to be in the range of 190–223 °C. Cyanate ester/epoxy blends were prepared. The thermal and mechanical properties of the blends were systemically investigated in detail through mechanical measurement [dynamic mechanical analysis (DMA)], scanning electron microscopy (SEM), and thermo-gravimetric analysis (TGA). TGA showed that the 10% weight loss temperature of all of the cured cyanate esters is above 284 °C. The char yield was found to be in the range of 52.67 to 61.14% and the flame retardancy of the cured cyanate esters was evaluated using the limiting oxygen index value, which is in the range of 38.57 to 41.95 at 700 °C. The cross-link density and glass transition temperature of the cyanate/epoxy ester blends were studied using dynamic mechanical analysis and the T_g was found to decrease with increasing cyanate ester content.