Structure-property relationships of cis-resveratrol cyanate ester blends

Abstract

cis-ResCy is a relatively low melting cyanate ester monomer (<80 °C) derived from the renewable phenol, resveratrol. Thermal cross-linking of this material generates a high Tg polycyanurate network with a char yield >73% in air (600 °C). However, the monomer still presents processing challenges because it is a solid at room temperature and readily recrystallizes upon cooling below the melting point. In this study, cis-ResCy was blended with commercial cyanate ester resins (Primaset LeCy, PT15, and PT30) at loadings between 0 and 80% (by mass) to improve the processability of cis-ResCy and evaluate the structure-property relationships of the blends and corresponding networks. Blends with LeCy were low melting solids, while the PT15 and PT30 blends remained liquid after mixing. The cure chemistry of the blends was evaluated and the thermomechanical properties, thermal stability, moisture uptake, and hot/wet properties of the corresponding networks were studied. In general, the char yields of the blended networks increased with higher cis-ResCy loading. This result was most pronounced for the LeCy networks, which yielded much higher char yields (>70% in air) at ≥ 40% cis-ResCy loading compared to pure LeCy (<40% in air). The Tgs of the networks increased with increasing cis-ResCy content and reached temperatures as high as 391 °C after in-situ cure. Overall, the combination of cis-ResCy with various commercial cyanate esters allowed for the development of processable resins with higher Tgs, improved thermal stability, and lower moisture uptake than the monomer components.