Effect of acetylacetone metal salts on curing mechanism and thermal stability of polybenzoxazine

To overcome high water absorption of inorganic metal salts and their poor compatibility with resin, acetylacetone metal salts (M(acac) (n) ) were selected as the catalysts of benzoxazine resin. Their effects on the catalytic activity, structure, and thermal stability of polybenzoxazine had been estimated by dynamic differential scanning calorimetry, in situ Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and thermal gravimetric analyzer. The results revealed that M(acac) (n) of iron (Fe3+), cobalt (Co3+ and Co2+), and copper (Cu2+) exhibited high catalytic activity and reduced evidently activation energy, especially acetylacetone iron salt. The addition of M(acac) (n) was beneficial to the formation of Ph-N-Ph structure, which was easy to form a denser carbon layer during thermal degradation, prevented heat transfer and further decomposition of the resin, and finally led to the increase of carbon residue at high temperature.