Electrical apparatus encapsulant

Abstract

An encapsulant composition has a silica containing inorganic-organic nano-hybrid matrix, particles of refractory ceramics suspended in the inorganic-organic nano-hybrid matrix, and, optionally, glass or ceramic fibres. The encapsulant may also contain ceramic coated metallic particles, and in some embodiments, a solvent or binder. The formulations can include a solvent, which may be removed during a curing process, or may be solvent-less

1 . A electrical encapsulant composition comprising a silica containing inorganic-organic nano-hybrid matrix, and particles of refractory ceramics suspended in the inorganic-organic nano-hybrid matrix 
     
     
         2 . A composition according to  claim 1 , wherein the inorganic-organic nano-hybrid matrix comprises one or more of a linear, branched and cross linked inorganic-organic nano-hybrid comprising an organic moiety comprising Si—R, where Si represents a silicon atom and R represents an organic radical. 
     
     
         3 . A composition according to  claim 2 , wherein the organic radical R contains between 1 and 18 carbon atoms. 
     
     
         4 . A composition according to  claim 3 , wherein the organic radical R also contains one or more of oxygen, nitrogen and halogen atoms. 
     
     
         5 . A composition according to  claim 1 , wherein the inorganic-organic nano-hybrid has the general formula: 
       
         
           
           
               
               
           
         
       
       where O represents an oxygen atom, H represents a hydrogen atom, Si represents a silicon atom, R′ is an alkyl radical containing 1 to 2 carbon atoms, and n is an integer. 
     
     
         6 . A composition according to  claim 2 , wherein the inorganic-organic nano-hybrid has the general form: 
       
         
           
           
               
               
           
         
       
       where O represents an oxygen atom, H represents a hydrogen atom, Si represents a silicon atom, R′ is an alkyl radical containing 1 to 2 carbon atoms, and n is an integer and m represents an integer. 
     
     
         7 . A composition according to  claim 2 , wherein the inorganic-organic nano-hybrid has the general form: 
       
         
           
           
               
               
           
         
       
       where O represents an oxygen atom, H represents a hydrogen atom, Si represents a silicon atom, R′ represents an alkyl radical containing 1 to 2 carbon atoms. 
     
     
         8 . A composition according to  claim 1 , wherein inorganic-organic nano-hybrid matrix is produced by a sol-gel process from an organosilane starting material. 
     
     
         9 . A composition according to  claim 8 , wherein the inorganic-organic nano-hybrid matrix is produced by hydrolising the organosilane starting material, and condensing the hydrolised organosilane starting material to form one or more of a linear, branched and cross linked inorganic-organic nano-hybrid. 
     
     
         10 . A composition according to  claim 1 , wherein the refractory ceramics particles comprise a metal oxide ceramic. 
     
     
         11 . A composition according to  claim 1 , wherein the refractory ceramics particles have a diameter of less than 100 μm. 
     
     
         12 . A composition according to  claim 1 , wherein the composition comprises metallic particles such as any of aluminium, copper, iron and nickel suspended in the matrix. 
     
     
         13 . A composition according to  claim 12 , wherein each of the metallic particles comprises an electrical insulator material coating. 
     
     
         14 . A composition according to  claim 1  further comprising fibres suspended in the matrix. 
     
     
         15 . A composition according to  claim 14 , wherein the fibres comprise one of short fibres and continuous yarns. 
     
     
         16 . A composition according to  claim 14 , wherein the composition comprises 2 to 20% by mass fibres. 
     
     
         17 . A composition according to any  claim 1 , wherein the mass ratio of nano-hybrid matrix to particulate ceramics is in the range of between 20/80 and 70/30. 
     
     
         18 . A composition according to  claim 16 , wherein the mass ratio of nano-hybrid matrix to particulate ceramics is in the range of between 25/75 and 60/40. 
     
     
         19 . A composition according to  claim 1 , wherein the composition further comprises a solvent. 
     
     
         20 . An electrical machine comprising an electrically conductive winding encapsulated in an encapsulation composition according to  claim 1 .