Chitosan as an intumescing, thermoformable flame retardant

The composition of 1, wherein the aqueous acid comprises hypophosphorous acid.

A flame retardant composition prepared by dissolution of chitosan or a modified chitosan by an aqueous acid over a period of up to 30 days followed by evaporation of the water, wherein:

• the aqueous acid is selected from the group consisting of hypophosphorous acid, aminophosphonic acid, aminosulfonic acid, phosphonoacetic acid, phenylphosphonic acid, phenylphosphinic acid, p-toluenesulfonic acid, trifluoromethylsulfonic acid, sulfaninilic acid, and combinations thereof;
• and
• at least one additional component is added prior to water evaporation and selected from the group consisting of a polyol, a flame retardant, a nitrogen containing compound, a carbonate containing compound, a crosslinking agent, and combinations thereof, and at least one added component comprises a polyhalogenated compound that is cyanuric chloride or 2,4-dichloro-6-alkyltriazine.