Synthesis and characterization of a carborane-containing monofunctional imide monomer as a modifier for imide oligomer

Abstract

A novel carborane-containing imide monomer (CB-PEPA) was synthesized and used as a modifier for phenylethynyl-terminated imide oligomer (PI-mPDA) to study the effect on the performance of the oligomers and thermosetting polyimide materials. The curing behavior of the blends of CB-PEPA and PI-mPDA was investigated by differential scanning calorimetry (DSC). It showed that CB-PEPA had a melting point at 183°C. Nonisothermal DSC showed that imide monomer had higher activation energy than that of bifunctional imide oligomer. Rheometer study showed that the monomer CB-PEPA could be used as a reactive diluent for PI-mPDA to reduce the minimum melt viscosity and broaden the process window of imide system. Thermogravimetric analysis showed that the char yield of resin increased with the addition of CB-PEPA. The resin derived from a 25 wt% CB-PEPA loading in PI-mPDA exhibited a high char yield of 81.0% at 800°C in nitrogen. Due to the steric hindrance and rigid group of carborane, the Tg of composites also increased with the addition of CB-PEPA. Composites derived from a 10 wt% CB-PEPA loading in PI-mPDA exhibited the relatively higher flexural strength and interlaminar shear strength.