Low flammability foam-like materials based on epoxy, tannic acid, and sodium montmorillonite clay

Aerogels based on sodium montmorillonite clay, epoxy polymer, and tannic acid as a flame retardant additive were fabricated through a simple, environmentally friendly freeze-drying process in which water is used as solvent. A one-step coating method using a coordination complex of natural polyphenols and Fe(III) ions was examined. Both the blended and the coated aerogels exhibit low flammabilities (the parameters measured are the time to ignition, the critical heat flux for ignition, and the heat release rate); the effects of tannic acid upon the aerogel compressive mechanical properties are reported.