Polymer blend and compositions and methods for using the same

Abstract

A polymer blend having at least one polysulfide component and at least one polythioether component is disclosed. The polymer blend offers numerous advantages, including the ability to compatibilize formulations based on either polysulfide chemistry or polythioether chemistry alone. Compositions comprising the polymer blend, particularly sealant formulations for use in aerospace applications, are also disclosed, as are multilayer sealant assemblies and methods for repairing the same.

1 . A polymer blend comprising: 
 a) at least one polysulfide component; and    b) at least one polythioether component.    
     
     
         2 . The polymer blend of  claim 1 , wherein the ratio of a:b is 10:90 to 90:10.  
     
     
         3 . The polymer blend of  claim 2 , wherein the ratio of a:b is 50:50.  
     
     
         4 . The polymer blend of  claim 1 , wherein the polysulfide component comprises more than one polysulfide polymer.  
     
     
         5 . The polymer blend of  claim 4 , wherein one polysulfide polymer in the polysulfide component has a molecular weight of 1000 and one polysulfide polymer in the polysulfide component has a molecular weight of 4000.  
     
     
         6 . The polymer blend of  claim 1 , wherein the polysulfide component has a number average molecular weight of 1000 to 4000.  
     
     
         7 . The polymer blend of  claim 1 , wherein the polythioether component has a number average molecular weight of 3000 to 4000.  
     
     
         8 . The polymer blend of  claim 7 , wherein the polythioether component has an average functionality from 2.1 to 2.6.  
     
     
         9 . The polymer blend of  claim 1 , having a Tg of −70° C., or less.  
     
     
         10 . A non-crystallizing composition comprising the polymer blend of  claim 1 .  
     
     
         11 . The non-crystallizing composition of  claim 10 , wherein the number average molecular weight of the polysulfide component is less than 1500.  
     
     
         12 . A composition comprising the polymer blend of  claim 1 .  
     
     
         13 . The composition of  claim 12 , having a viscosity of 100 to 400 poise.  
     
     
         14 . The composition of  claim 12 , having a viscosity of 6000 to 18000 poise.  
     
     
         15 . The composition of  claim 13 , having a viscosity of 1000 to 4000 poise.  
     
     
         16 . A sealant composition comprising: 
 a) a polymer blend comprising: 
 i) at least one polysulfide component and  
 ii) at least one polythioether component; and  
   b) a curing agent.    
     
     
         17 . The sealant of  claim 16 , wherein the curing agent comprises an oxidizing agent.  
     
     
         18 . The sealant of  claim 17 , wherein the curing agent comprises manganese dioxide.  
     
     
         19 . The sealant of  claim 16 , further comprising at least one additive selected from fillers, adhesion promoters, plasticizers, pigments, thixotropes, retardants, catalysts, and masking agents.  
     
     
         20 . The sealant of  claim 19  comprising a filler.  
     
     
         21 . A method for repairing a first sealant, comprising: 
 a) applying the composition of  claim 12  to the first sealant layer; and    b) applying a second sealant layer thereon;    wherein either the first or second sealant layer is based on polysulfide chemistry, and the other sealant layer is based on polythioether chemistry.    
     
     
         22 . A multilayer sealant composition comprising: 
 a) a first sealant;    b) a second sealant; and    c) a sealant comprising a polymer blend comprising at least one polysulfide component and at least one polythioether component, wherein the sealant layer comprising the polymer blend is between the first sealant and the second sealant, and wherein either the first or second sealant is based on polysulfide chemistry and the other of the first or second sealant is based on polythioether chemistry.    
     
     
         23 . A mixture comprising: 
 a) the polymer blend of  claim 1;  and    b) a polymer having a cure time of greater than eight hours.