A Phosphorus-Containing Diamine for Flame-Retardant, High-Functionality Epoxy Resins. I. Synthesis, Reactivity, and Thermal Degradation Properties

A phosphorus-containing amine, bis(4-aminophenoxy)phenyl phosphine oxide (BAPP), suitable for curing epoxy resins with improved fire performance was synthesized and characterized with Fourier transform infrared spectroscopy and nuclear magnetic resonance. The reactivity of the amino group was evaluated by differential scanning calorimetry of the epoxy-amine mixture and by proton nuclear magnetic resonance of the amino unit. With BAPP as a curing agent, a range of high-functionality, aerospace epoxy resins were cured, and the dynamic kinetic parameters calculated from Kissinger's and Ozawa's models were compared with those from the more widely used amines. The thermal degradation properties of the phosphorus-containing epoxy resins were studied by thermogravimetric analysis, the degradation activation energy was calculated, and a multistep thermal degradation process was observed.