Thermal protective composition and method of protecting a substrate from hyperthermal conditions

Abstract

A composite system capable of protecting a substrate from a jet fire including a lower layer of an active fire protective material and an upper layer of a fire protective material. The upper layer forms an open cell matrix when exposed to a jet fire to permit passage of gasses from the lower layer to ambient. The upper layer comprises a fill of refractory material and protects the system during initial exposure to a hyperthermal condition. The upper layer swells on exposure to hyperthermal conditions, but swells less than the lower layer.

1 . A thermally protective composition comprising a polymeric binder, a flexibilizing agent, from 10% to 30% of a blowing agent which changes from solid to gas at a hyperthermal temperature to which the composition may be subjected, and at least 20% by weight of a refractory filler.  
     
     
         2 . The composition of  claim 1  wherein the binder is an epoxy resin modified with the flexibilizing agent, the composition comprising about 35% to about 65% by weight of the modified epoxy resin.  
     
     
         3 . The composition of  claim 2  wherein the flexibilizing agent comprises polysulfide, and wherein the modified epoxy resin is cured with an amine.  
     
     
         4 . The composition of  claim 1  wherein the filler comprises both particles and fibers.  
     
     
         5 . The composition of  claim 1  wherein the filler comprises ceramic particles and glass fibers.  
     
     
         6 . The composition of  claim 1  wherein the filler comprises one or more materials selected from the group consisting of glass, graphite, and ceramic.  
     
     
         7 . The composition of  claim 1  wherein the filler comprises at least 25% by weight of the composition.  
     
     
         8 . The composition of  claim 7  wherein the filler comprises about 25% to 40%, by weight of the composition.  
     
     
         9 . A thermally protective composition comprising a polymeric binder, a blowing agent, and at least 7% by weight of the composition of a refractory filler, the composition responding to hyperthermal conditions by expanding about 10% to about 100% and forming an open cell matrix.  
     
     
         10 . The composition of  claim 9  wherein the refractory filler comprises both particles and fibers.  
     
     
         11 . The composition of  claim 9  wherein the filler comprises ceramic particles and glass fibers.  
     
     
         12 . The composition of  claim 9  wherein the filler comprises one or more materials selected from the group consisting of glass, graphite, and ceramic.  
     
     
         13 . The composition of  claim 9  wherein the filler comprises at least about 15% by weight of the composition.  
     
     
         14 . The composition of  claim 9  wherein the filler comprises about 25% to 30%, by weight of the composition.  
     
     
         15 . The composition of  claim 9  wherein the blowing agent comprises 10% to 30% by weight of the composition.  
     
     
         16 . The composition of  claim 9  comprising a flexibilizing agent.  
     
     
         17 . The composition of  claim 16  wherein the composition comprises about 35% to about 65% modified epoxy resin.  
     
     
         18 . The composition of  claim 17  wherein the epoxy resin is modified with polysulfide and cured with an amine.  
     
     
         19 . A method for protecting a substrate from hyperthermal conditions comprising a first step of applying a layer of a first polymeric active thermal protective composition to the substrate, thereafter a second step of applying to the first layer an upper layer of a second polymeric thermal protective composition which when exposed to a fire or other hyperthermal condition swells to form an open cell matrix to permit passage of gasses from the lower layer to ambient, the second composition comprising a fill of a refractory material comprising at least about seven percent of the second composition by weight, and a step of embedding a mesh or fabric reinforcement in the system.  
     
     
         20 . The method of  claim 19  wherein both the first composition and the second composition comprise a polymeric binder and a gas former, the second composition comprising less gas former by weight than the first composition, the method providing a composite system overlying the substrate.  
     
     
         21 . The method of  claim 20  wherein the upper layer is an epoxy resin modified to increase its flexibility and elasticity.  
     
     
         22 . The method of  claim 20  wherein the reinforcement comprises a graphite fabric.  
     
     
         23 . The method of  claim 20  wherein the reinforcement comprises a metal mesh.  
     
     
         24 . The method of  claim 19  wherein lower layer is applied to a cured thickness of about one to about twenty-five mm.  
     
     
         25 . The method of  claim 24  wherein the lower layer is less than 15 mm thick.  
     
     
         26 . The method of  claim 19  wherein the lower layer responds to hyperthermal conditions by expanding to at least twice its original thickness.  
     
     
         27 . The method of  claim 19  wherein the upper layer is applied to a cured thickness of about one to about fifteen mm.  
     
     
         28 . The method of  claim 27  wherein the upper layer is less than about six mm thick.  
     
     
         29 . The method of  claim 19  wherein the upper layer responds to hyperthermal conditions by expanding to an average thickness no more than twice its original thickness.