Electret article having heteroatoms and low fluorosaturation ratio

Abstract

An electret article that includes a polymeric material that has electric charge imparted thereto, that has one or more heteroatoms, that has a fluorosaturation ratio of less than 200, and that has an atomic percent fluorine of greater than about 40%. The inventive electret article is resistant to charge degradation upon exposure to high temperatures for prolonged time periods.

1 . A method of making a fluorinated electret article, which method comprises: 
 (a) fluorinating a nonconductive polymeric article in a plasma generated in a controlled atmosphere that contains a fluorine-containing species and a nitrogen-containing species, the fluorination occurring at a pressure less than atmospheric; and    (b) imparting a persistent electric charge to the polymeric article.    
   
   
       2 . The method of  claim 1 , wherein the fluorination step is carried out at least in part at a reduced pressure.  
   
   
       3 . The method of  claim 2 , wherein the pressure is less than 140 Pascals.  
   
   
       4 . The method of  claim 1 , wherein the fluorine-containing species includes fluorine atoms, elemental fluorine, fluorocarbons, organic fluorides, fluorinated nitrogen, PF 3 , BF 3 , SiF 4 , hexafluoropropylene oxide, octafluorotetrahydrofuran, and combinations thereof.  
   
   
       5 . The method of  claim 1 , wherein a persistent electric charge is imparted to the polymeric article by a step(s) that include hydrocharging.  
   
   
       6 . The method of  claim 1 , wherein the fluorination step is carried out using an AC power discharge.  
   
   
       7 . The method of  claim 1 , wherein the fluorination occurs in a controlled atmosphere.  
   
   
       8 . The method of  claim 1 , wherein the fluorination occurs in an atmosphere that contains less than 1% oxygen.  
   
   
       9 . The method of  claim 1 , wherein the fluorination occurs in an atmosphere that contains less than 0.01% oxygen by volume.