Light weight seal cap

Abstract

The present disclosure provides methods and articles useful in sealing fasteners, including seal caps and methods of their use, and in particular light weight seal caps having higher dielectric breakdown strength, lower weight, and/or lower wall thickness. In some embodiments, the seal caps according to the present invention are made of a material having a dielectric breakdown strength of greater than 1.0 kV/mm, in some embodiments greater than 15.0 kV/mm, and in some embodiments greater than 50.0 kV/mm. In some embodiments, the seal caps according to the present invention are thin-walled, having an average wall thickness of less than 1.5 mm and in some embodiments less than less than 0.5 mm. In some embodiments, the seal cap comprises a polyurethane polymer, a polythioether polymer, a polysulfide polymer, a fluorinated thermoplastic polymer, a THV polymer, a fluorinated thermoset polymer, an engineering thermoplastic, and/or a PEEK polymer.

1 . A method of protecting a fastener from lightning strikes, said method comprising:
 a) providing a fastener;   b) providing a seal cap which defines an interior, wherein the seal cap comprises a polythioether polymer;   c) providing an uncured sealant to the interior of the seal cap or to the fastener or to both; and   d) positioning the seal cap over the fastener such that at least a portion of the fastener resides in the interior of the seal cap.   e) curing the sealant.   
     
     
         2 . The method according to  claim 1  wherein the seal cap is translucent or transparent, and curing the sealant comprises application of actinic radiation to the sealant through the seal cap. 
     
     
         3 . The method according to  claim 1  wherein the fluorinated thermoplastic polymer has a dielectric breakdown strength of greater than 30.0 kV/mm. 
     
     
         4 . The method according to  claim 1  wherein the fluorinated thermoplastic polymer has a dielectric breakdown strength of greater than 50.0 kV/mm. 
     
     
         5 . The method according to  claim 1  wherein the seal cap has an average wall thickness of less than 1.5 mm. 
     
     
         6 . The method according to  claim 1  wherein the interior of the seal cap is provided with a quantity of an uncured sealant. 
     
     
         7 . A lightning strike protected fastener construction comprising:
 a) a fastener;   b) a seal cap defining an interior; and   c) a cured sealant in the interior of the seal cap;   wherein the seal cap comprises a polythioether polymer, the seal cap is positioned over the fastener such that at least a portion of the fastener resides in the interior of the seal cap, and the cured sealant binds the seal cap to the fastener.   
     
     
         8 . The fastener construction according to  claim 7  wherein the seal cap is translucent or transparent, and the sealant comprises an actinic radiation curable composition. 
     
     
         9 . The fastener construction according to  claim 7  wherein the fluorinated thermoplastic polymer has a dielectric breakdown strength of greater than 30.0 kV/mm. 
     
     
         10 . The fastener construction according to  claim 7  wherein the seal cap has an average wall thickness of less than 1.5 mm. 
     
     
         11 . A lightning strike protection application-ready seal cap comprising:
 a) a seal cap which defines an interior; and   b) a quantity of an uncured sealant in the interior of the seal cap,   wherein the seal cap comprises a polythioether polymer.   
     
     
         12 . The application-ready seal cap according to  claim 11  wherein the seal cap is translucent or transparent, and the uncured sealant is curable by the application of actinic radiation. 
     
     
         13 . The application-ready seal cap according to  claim 11  wherein the fluorinated thermoplastic polymer has a dielectric breakdown strength of greater than 30.0 kV/mm. 
     
     
         14 . The application-ready seal cap according to  claim 11  wherein the fluorinated thermoplastic polymer has a dielectric breakdown strength of greater than 50.0 kV/mm. 
     
     
         15 . The application-ready seal cap according to  claim 11  wherein the seal cap has an average wall thickness of less than 1.5 mm. 
     
     
         16 . A seal cap for lightning strike protection of a fastener, with the seal cap comprising a polythioether polymer. 
     
     
         17 . The seal cap according to  claim 16  which is translucent or transparent to actinic radiation. 
     
     
         18 . The seal cap according to  claim 16  wherein the fluorinated thermoplastic polymer has a dielectric breakdown strength of greater than 30.0 kV/mm. 
     
     
         19 . The seal cap according to  claim 16  wherein the fluorinated thermoplastic polymer has a dielectric breakdown strength of greater than 50.0 kV/mm. 
     
     
         20 . The seal cap according to  claim 16  having an average wall thickness of less than 1.5 mm.