The present invention relates to an intumescent material, and, in particular, to a intumescent material that can be applied as a caulking, coating or film, which includes a liquid carrier with a corrosion inhibitor, expandable particulate graphite, and a filler, if desired, and the method of making such an intumescent material.
Intumescent materials, which are commonly used as fire stopping barriers, typically include a liquid coating, caulking or film forming carrier, expandable graphite, and a filler. These materials, applied as caulking, coatings, films, etc., form passive fire protection systems which remain inactive until subjected to heat and temperatures such as those encountered from the flames of a fire. When these passive fire protection systems are subjected to heat and temperatures, such as those encountered in a fire, these intumescent materials react, grow and expand forming a char (many times the original thickness of the caulking, coating or film applied) to insulate the surface to which the material is applied, e.g. the surface of structural steel in a building, from the damaging effects of the heat generated by the fire.
Typically, the expandable graphite, used in these materials, is prepared from particulate, naturally occurring crystalline flake graphite or crystalline lump graphite, that has been acid treated to make the graphite intumescent. It is believed that the treatment of the crystalline flake graphite or crystalline lump graphite with concentrated sulfuric acid in the presence of an oxidizing agent, such as nitric acid, forms the compound graphite sulfate which exfoliates and expands upon heating.
While these materials can be quite effective as fire barriers, the acidic properties of the expandable graphite in these materials causes these materials to be corrosive to steel, stainless steel, copper, aluminum, galvanized steel and other metals or metal alloys, such as those commonly used in the construction industry. Thus, in applications, where these intumescent materials come in contact with metal components, e.g. girders and other structural members of buildings and the like, the use of these intumescent materials can cause corrosion problems or require the application of primers or other protective coatings to the metal components prior to the application of the intumescent material thereby increasing both labor and material costs.