Intumescent polydopamine coatings for fire protection

Polydopamine with additional bioderived flame retardants was used as coatings for flexible polyurethane foam and triple-wall corrugated cardboard. Clay was used to prevent the foam from collapsing during combustion. Dopamine can also effectively intercalate clay to produce well-distributed coatings, so it was used in all coatings. Scanning electron microscopy was used to examine the morphology of the coatings. The amount of polydopamine coating applied to clay platelets and the morphology of the aggregates formed were greatly affected by the catalyzing base used. Amine-containing bases produced the largest aggregates and gaseous ammonia was found to be an effective base. The ability to form intumescing coatings was crucial for achieving good flame protection. Microcombustion calorimetry, flame-spread and cone calorimetry experiments revealed that (aminomethyl)phosphonic acid and glycine phytate produce intumescing chars that, in combination with montmorillonite clays, form a protective barrier for both foam and cardboard. The added flame retardants were also important for reducing the smoldering propensity of cardboard after flame extinguishment.