A novel repair agent for resin-injection repair of advanced high temperature composites was developed and characterized. The repair agent was based on bisphenol E cyanate ester (BECy) and reinforced with alumina nanoparticles. To ensure good dispersion and compatibility with the BECy matrix in nanocomposites, the alumina nanoparticles were functionalized with silanes. The BECy nanocomposites, containing bare and functionalized alumina nanoparticles, were prepared and evaluated for their thermal, mechanical, rheological, and viscoelastic properties.

The monomer of BECy has an extremely low viscosity at ambient temperature, which is good for processability. The cured BECy polymer is a highly cross-linked network with excellent thermal mechanical properties, with a high glass transition temperature (Tg) of 270 yC and decomposition temperature above 350 yC. The incorporation of alumina nanoparticles enhances the mechanical and rheological properties of the BECy

nanocomposites. Additionally, the alumina nanoparticles are shown to catalyze the cure of BECy.

Characterization of the nanocomposites included dynamic mechanical analysis, differential scanning calorimetry, thermogravimetric analysis, rheological and rheokinetic

evaluation, and transmission electron microscopy. The experimental results show that the BECy nanocomposite is a good candidate as repair agent for resin-injection repair

applications.