An adenine-containing curing agent, 9,10-bis(4-aminophenyl) adenine (p-APA) was designed to decrease the volatility of curing agent. The exact structure of p-APA was confirmed by proton nuclear magnetic resonance (1H NMR), infrared spectroscopy (IR) and elementary analyzer (EA). Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) were measured to compare volatility of p-APA with that of a traditional curing agent, 1,3-bis(4-aminophenoxy) benzene (4-APB), which indicated p-APA has better thermal stability and lower volatility. The thermal tests of different curing process of phthalonitriles showed good thermal and thermo-oxidative stabilities. The thermal property was improved along with increasing curing temperature and time and the glass-transition temperature (Tg) was not observed on DSC before 400 °C. The Fourier transform infrared spectroscopy (FTIR) showed that triazine and phthalocyazine rings were the dominant reaction products of the cured phthalonitriles. The dynamic mechanical analysis (DMA) of post-cured phthalonitriles showed a storage modulus of 1.3 GPa at 40 °C and Tg about 500 °C.

Keywords: thermosetting resins; thermal stability; adenine; aromatic curing agents; phthalonitrile composites