A novel dendritic polyaniline/phytate@Cu organic-metal composite flame retardant for improving thermal protection of epoxy coatings

Polyaniline (PANI), a polymer with a high nitrogen content, has been shown to have good flame retardant properties. Here, we significantly improved the self-carbon formation ability of PANI at high temperature by doping with phytic acid (PA). Meanwhile, a new organic-metal ion flame retardant (DPANI/PA@Cu) was obtained by introducing Cu2+ with catalytic carbon formation property into PANI/PA using the complexation between transition metal ions and PA. Surprisingly, the introduction of metal ions was also able to trigger the formation of dendritic structure of PANI (DPANI), which is important for its dispersion in resin matrix and strengthening effect on the coating. The test results demonstrated that the composite coating with 5% content of DPANI/PA@Cu had the lowest back-side temperature (174.9 ℃), the highest expansion height (18.5 mm) and the lowest smoke density class (45.3%). In addition, the DPANI/PA@Cu5%/EP composite coating retained the maximum amount of residual carbon (29.7%), which was mainly related to the synergistic catalytic effect of PA and Cu2+. Ultimately, the retained PANI residual carbon and CuO nanoparticles diffused in the char layer acted as interceptors for the external flame and heat.