Intumescent compositions producing and relying upon low density carbon foams
An intumescent composition based upon modifications to tannic acid (TA), including certain additives, is contemplated. Such compositions may be incorporated in epoxy and other resin-based coatings. The resulting composition produces a novel, lightweight, and extremely effective intumescent char having a density of 1.5 to 4.0 mg/cm 3 .
1 . An intumescent coating composition comprising:
a curable binder comprising an epoxy resin and an amine curing agent;
a blowing agent provided at between 12 to 22 wt. % of the composition;
an acid source provided at between 12 to 22 wt. % of the composition; and
tannic acid provided at between 10 to 50 wt. % of the composition;
wherein the epoxy resin is provided at between 10 to 30 wt. % of the composition;
wherein the amine curing agent is provided at between 5 to 22 wt. % of the composition; and
wherein the composition, when burned with a flame after cure, produces a char having a density of between 1.5 and 4.0 mg/cm 3 .
2 . The composition according to claim 1 wherein the char has an atomic composition of carbon greater than 50%.
3 . The composition according to claim 1 wherein the char has a BET surface area of greater than 40 m 2 /g.
4 . The composition according to claim 1 wherein the blowing agent is melamine or a carbonate.
5 . The composition according to claim 4 wherein the blowing agent is melamine.
6 . The composition according to claim 5 wherein the acid source is ammonium polyphosphate.
7 . The composition according to claim 1 wherein the acid source is ammonium polyphosphate.
8 . The composition according to claim 1 wherein the acid source and the blowing agent are provided in equal amounts.
9 . The composition according to claim 1 wherein the tannic acid is provided at between 20 to 25 wt. % of the composition.
10 . The composition according to claim 1 wherein the density is 2.13 mg/cm 3 , +/−0.42 mg/cm 3 .
11 . The composition according to claim 1 which is free from boric acid and pentaerythritol.
12 . A wooden or cardboard substrate coated with the composition according to claim 1 wherein a coated surface of the wooden or cardboard substrate is exposed to a flame after cure until failure and a temperature of the coated surface at failure is less than 145° C.
13 . A wooden or cardboard substrate coated with the composition according to claim 1 wherein a coated surface of the wooden or cardboard substrate is exposed to a flame after cure and a heating slope until 60° C. is less than 0.40° C./second.