Clay and Crab Shells Could Replace Toxic Flame Retardants

By Paula Melton

Alternating layers of clay and chitosan (a polymer derived from crustacean shells) have shown promise as a possible flame retardant in lab tests at Texas A&M University. When applied to foam and exposed to a direct flame for ten seconds, the coating formed a protective thermal barrier that kept the foam from igniting or melting—giving lead researcher Jaime Grunlan, Ph.D., hope that coatings made from renewable materials could eventually replace brominated flame retardants (BFRs).

Unlike BFRs, which chemically disrupt a fire that has already begun, this coating is designed to prevent ignition, Grunlan explained. Chitosan between the clay layers does flame up briefly, but the clay quickly “collapses,” he said. “The polymer gets eaten out by heat and fire initially, and what’s left behind is a layer of clay-rich coating which acts as a heat barrier.”

The coating requires use of nano-scale clay particles, which could raise toxicity concerns, but Grunlan said the clay nanoparticles are created and bound within water and should not be breathable during manufacture or after application. His team is also testing other thinly layered polymers as a flame-retardant coating for fabric.