Thermally protective materials

Abstract

A mixture comprising an expandable graphite and a polymer resin is described wherein the polymer resin-expandable graphite mixture has a volume increase and structural integrity after exposure to heat. Methods are described for increasing the thermal protective performance (TPP) of textiles and laminates while optionally maintaining comfort, flexibility, and liquid protective properties.

1 . A polymer resin-expandable graphite mixture comprising about 2 wt % to about 30 wt % of an expandable graphite and about 30 wt % to about 98 wt % of a polymer resin with a modulus between 10 3  and 10 6  dynes/cm 2  at 200° C. and Tan Delta of between 0.1 and 10 at 200° C., wherein the polymer resin-expandable graphite mixture has a minimum volume increase of at least 200% after exposure to 300° C. for 90 seconds. 
   
   
       2 . The material of  claim 1  wherein after exposure to 300° C. for 90 seconds the expanded mixture maintains integrity upon thickness testing. 
   
   
       3 . The material of  claim 1  wherein after exposure to 300° C. for 90 seconds the mixture comprises a plurality of tendrils comprising expanded graphite having an aspect ratio of at least 5 to 1. 
   
   
       4 . A method for increasing the thermal protective performance (TPP) of a flame resistant, thermally stable textile by at least 2 cal/cm 2  comprising the steps of
 providing a flame resistant, thermally stable textile, and   forming an active insulation on the flame resistant, thermally stable textile, by applying a polymer resin-expandable graphite mixture to a surface of the flame resistant textile in an amount of less than about 140 gsm, to form a thermally protective material.   
   
   
       5 . The method of  claim 4  comprising forming the active insulation on a side of the flame resistant, thermally stable textile that is opposite a side exposed to heat when tested for TPP. 
   
   
       6 . The method of  claim 4  comprising applying less than 140 gsm of polymer resin-expandable graphite mixture and increasing the TPP by at least 1 cal/cm2 per approximately each 35 gsm of polymer resin-expandable graphite mixture applied. 
   
   
       7 . The method of  claim 4  wherein the flame resistant, thermally stable textile comprises meta-aramid, para-aramid, or blends thereof. 
   
   
       8 . The method of  claim 4  wherein the flame resistant, thermally stable textile comprises PBI, PBO, modacrylic, FR cotton, FR rayon and blends thereof. 
   
   
       9 . The method of  claim 4  wherein the polymer resin of the polymer resin-expandable graphite mixture is elastomeric. 
   
   
       10 . The method of  claim 4  wherein the polymer resin of the polymer resin-expandable graphite mixture comprises polyurethane. 
   
   
       11 . The method of  claim 4  wherein the polymer resin-expandable graphite mixture is applied to the flame resistant thermally stable textile discontinuously. 
   
   
       12 . The method of  claim 4  comprising applying the polymer resin-expandable graphite mixture discontinuously forming discrete dots on the surface of the flame resistant thermally stable textile. 
   
   
       13 . The method of  claim 4  comprising applying the polymer resin-expandable graphite mixture to less than 50% of the surface area of the flame resistant thermally stable textile. 
   
   
       14 . The method of  claim 4  comprising applying the polymer resin-expandable graphite mixture as dots to less than about 35% of the surface area of the flame resistant textile and providing approximately 2000 microns or greater spacing between dots. 
   
   
       15 . The method of  claim 4  further comprising expanding the active insulation by at least 500 μm upon exposure of the flame resistant thermally stable textile to 300° C. for about 90 seconds. 
   
   
       16 . The method of  claim 4  comprising the step of forming the polymer resin-expandable graphite mixture by melting or dissolving a polymer resin and mixing an expandable graphite in the melted or dissolved polymer resin before applying the polymer resin-expandable graphite mixture to the flame resistant, thermally stable textile. 
   
   
       17 . A method for increasing the TPP of a laminate of a flame resistant, thermally stable textile and a convective barrier, comprising
 disposing an active insulation comprising a polymer resin-expandable graphite mixture between the flame resistant, thermally stable textile and the convective barrier, and joining the textile and convective barrier, forming a thermally protective laminate having a TPP increase of at least 3 cal/cm 2 .   
   
   
       18 . The method of  claim 17  wherein convective barrier comprises PTFE. 
   
   
       19 . The method of  claim 17  wherein the convective barrier and the flame resistant textile are bonded together by the polymer resin-expandable graphite mixture. 
   
   
       20 . The method of  claim 17  comprising applying the polymer resin-expandable graphite mixture to convective barrier. 
   
   
       21 . A thermally protective material comprising
 a flame resistant, thermally stable substrate, and   an active insulation comprising a polymer resin-expandable graphite mixture disposed on one side of the flame resistant, thermally stable substrate, wherein the active insulation expands by at least 250% after 90-seconds in a convective oven heated to 300° C.   
   
   
       22 . A method for increasing the TPP of an ensemble comprising providing an outer shell fabric comprising a flame resistant, thermally stable textile;
 providing a moisture barrier adjacent the outer shell fabric; and   providing an inner textile comprising an aramid material adjacent the moisture barrier opposite the outer shell fabric to form a textile ensemble; and   increasing the contact TPP of the assembly by at least 10 cal/cm2 by applying a polymer resin-expandable graphite mixture to a surface of the outer shell textile adjacent the moisture barrier.   
   
   
       23 . The method of  claim 22  comprising increasing the contact TPP of the assembly by at least about 12 cal/cm2. 
   
   
       24 . The method of  claim 22  comprising increasing the contact TPP of the assembly by at least about 15 cal/cm2.