Synthesis and characterization of nadimidized 1‐[(dialkoxyphosphinyl)methyl1]‐2,4‐ and ‐2,6‐ diaminobenzenes and their polymerization to fire‐resistant laminating resins

A series of nadimidized 1‐[(dialkoxyphosphinyl1)methyl]‐2,4‐ and ‐2,6‐diaminobenzenes was prepared and polymerized thermally to yield highly crosslinked fire‐resistant laminating resins. Bisnadimides were characterized by elemental analysis and Fourier‐transform‐infrared (FT–IR) and proton nuclear magnetic resonance (1H‐NMR) spectroscopy. Curing behavior of the polymer precursors was studied by differential scanning calorimetry (DSC). Char yield of polymers at 700°C was 64–69% and 30–60% in nitrogen and air atmospheres, respectively. The pyrolysis behavior of some bisnadimides was investigated by gas chromatography–mass spectroscopy (GC–MS). Cyclopentadiene was evolved by retrograde Diels–Alder reaction during processing, but most was captured by copolymerization. The fire‐resistance of some polymers was evaluated by determining their limiting oxygen index and smoke evolution.