Curable perfluoroelastomer composition

1. A curable composition comprising

A. a perfluoroelastomer comprising copolymerized units of (1) tetrafluoroethylene, (2) a perfluoro(vinyl ether), and (3) a cure site monomer selected from the group consisting of nitrile-containing fluorinated olefins and nitrile-containing fluorinated vinyl ethers;

B. 1–25 parts by weight per hundred parts by weight perfluoroelastomer of a hydrophobic silica; and

C. a curative selected from the group consisting of i) a bis(aminophenol) and ii) a compound that decomposes at temperatures between 40° and 330° C. to produce ammonia.

2. A curable composition of claim 1 further comprising a filler selected from the group consisting of hydrophobic titanium dioxide and hydrophobic alumina.

3. A curable composition of claim 1 wherein said perfluoroelastomer comprises copolymerized units of 38.5 to 74.7 mole percent tetrafluoroethylene, 25 to 60 mole percent perfluoro(methyl vinyl ether) and 0.3 to 1.5 mole percent perfluoro(8-cyano-5-methyl-3,6-dioxa-1-octene).

4. A curable composition of claim 1 wherein said hydrophobic silica is present in an amount between 5 and 15 parts by weight per hundred parts by weight perfluoroelastomer.

5. A curable composition of claim 1 wherein said hydrophobic silica has on its surface hydrophobic functional groups selected from the group consisting of (—O—) 2 —Si(CH 3 ) 2 , —O—Si—(CH 3 ) 3 , and (—O—) 3 —Si—C 8 H 17 .

6. A curable composition of claim 1 wherein said bis(aminophenol) is 2,2-bis[3-amino-4-hydroxyphenyl]hexafluoropropane.

7. A curable composition of claim 1 wherein said compound that decomposes to produce ammonia is selected from the group consisting of acetaldehyde ammonia; hexamethylenetetramine; t-butyl carbamate; benzyl carbamate; HCF 2 CF 2 CH(CH 3 )OCONH 2 ; urea; urea hydrochloride; thiourea; phthalamide; metal ammine complexes; oxamic acid; biuret; formamidine; formamidine hydrochloride; and formamidine acetate.