Self-sealing fastener

Abstract

An apparatus for making and using a fastener suitable for use in airplane manufacture or repair that is coated with a pre-mixed moisture cure sealant. The sealant layer is coated with a frangible moisture barrier that will break apart when the fastener is installed, thus exposing the sealant to a moisture source. Once exposed to moisture, the sealant will begin to cure. Preferred embodiments also provide a premature cure indicator that provides a visual indication that the outer moisture resistant layer has been damaged.

1 - 9 . (canceled) 
     
     
         10 . A method of attaching two workpieces together using self-sealing metal fasteners, the method comprising:
 providing a plurality of fasteners covered with a self-sealing coating, said self-sealing coating comprising:
 a layer of a one-part moisture-curable sealant; and 
 a layer of a frangible moisture barrier coating covering said one or more layers of uncured one-part moisture-curable sealant, such that when the fastener is installed into a pre-drilled hole in a workpiece the frangible moisture barrier will break apart and at least a portion of said moisture barrier coating will be extruded rather than mixing with the portion of the sealant forming the seal between the fastener and the workpiece; 
   installing the fasteners through pre-drilled holes to attach the workpieces together, the installation applying sufficient force to the frangible moisture barrier coating to break the coating apart and cause the coating to extrude from the hole; and   allowing moisture from a moisture source to reach the layer of uncured sealant on the installed fasteners so that the sealant will cure and form a seal between the fasteners and at least one of the workpieces.   
     
     
         11 . The fastener of  claim 10  in which the moisture source is atmospheric moisture. 
     
     
         12 . The method of  claim 10  in which providing a plurality of fasteners comprises providing a plurality of fasteners, each including a coating of a premature cure indicator, said premature cure indicator changing color when exposed to thiol reactive groups. 
     
     
         13 . The method of  claim 12  further comprising:
 before installing the fasteners, inspecting the premature cure indicator coating to determine whether there has been a color change; and 
 discarding the fasteners showing a color change. 
 
     
     
         14 . A method of producing a self-sealing fastener, the fastener having a head and shank, and the method comprising:
 applying a layer of a one-part moisture curing sealant to the fastener;   overcoating the layer of sealant with a coating of a moisture barrier size coat, and curing the size coat using actinic radiation to form a frangible moisture barrier coating over the layer of sealant.   
     
     
         15 . The method of  claim 14  in which curing the size coat includes curing the size coat without curing the sealant. 
     
     
         16 . The method of  claim 14  further comprising, after applying the moisture curing sealant to the fastener, applying a coating of a premature cure indicator that changes color when exposed to thiol reactive groups. 
     
     
         17 . The method of  claim 14  in which said moisture curing sealant is a one-part sealant. 
     
     
         18 . The method of  claim 14  in which the curable sealant comprises a polysulfide sealant. 
     
     
         19 . The method of  claim 14  in which the curable sealant comprises a polythioether sealant. 
     
     
         20 . The method of  claim 14  in which applying a moisture curing sealant to the fastener comprises applying a sufficient volume of sealant uniformly around the shank of the fastener so that when the fastener is installed into a workpiece a small amount of sealant visibly extrudes completely around the fastener head. 
     
     
         21 . The method of  claim 14  in which the size coat is cured by actinic radiation. 
     
     
         22 . The method of  claim 14  in which the sealant, the moisture barrier, and the premature cure indicator coatings are applied one coating at a time with metered fluid dispensers to fasteners rotated during application. 
     
     
         23 - 31 . (canceled) 
     
     
         32 . A method of attaching two workpieces together using self-sealing metal fasteners, the method comprising:
 providing a plurality of fasteners, wherein the fasteners include:   (i.) a layer of a one-part moisture curable sealant that has been cure-blocked to prevent curing until exposed to moisture,   (ii). one or more layers of a frangible moisture barrier coating covering the layer of one-part curable sealant such that when the fastener is installed the frangible moisture barrier will break apart allowing moisture from a moisture source to reach the sealant so that the sealant will cure, and   (iii). a cure indicator for indicating with a color change whether the sealant has cured or has begun to cure;   inspecting the cure indicator to determine whether there has been a color change;   discarding the fasteners showing a color change;   installing the fasteners not showing a color change through predrilled holes to attach the workpieces together, whereby the step of installing includes applying sufficient force to said frangible moisture barrier coating to break the coating apart; and   allowing moisture from a moisture source to reach the layer of cure-blocked sealant on the installed fasteners so that the sealant will cure and form a seal between the fasteners and at least one of the workpieces.   
     
     
         33 . The method of  claim 10  in which the one-part moisture-curable sealant comprises a thiol-terminated polymer, pre-polymer, or oligomer capped with an organic and/or an organosilane protecting group where the protecting group is cleaved by moisture. 
     
     
         34 . The method of  claim 10  in which the one-part moisture-curable sealant comprises a thiol-terminated polymer, pre-polymer, or oligomer capped with an inorganic protecting group where the protecting group is cleaved by moisture. 
     
     
         35 . The method of  claim 10  in which the one-part moisture-curable sealant comprises a thiol-terminated polymer, pre-polymer, or oligomer capped with an inorganic salt protecting group where the protecting group is cleaved by moisture. 
     
     
         36 . The method of  claim 32  in which the one-part moisture curable sealant comprises a thiol-terminated polymer, pre-polymer, or oligomer capped with an organic and/or an organosilane protecting group where the protecting group is cleaved by moisture. 
     
     
         37 . The method of  claim 32  in which the one-part moisture curable sealant comprises a thiol-terminated polymer, pre-polymer, or oligomer capped with an inorganic protecting group where the protecting group is cleaved by moisture. 
     
     
         38 . The method of  claim 32  in which the one-part moisture curable sealant comprises a thiol-terminated polymer, pre-polymer, or oligomer capped with an inorganic salt protecting group where the protecting group is cleaved by moisture.