Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B64—AIRCRAFT; AVIATION; COSMONAUTICS
  • B64D—EQUIPMENT FOR FITTING IN OR TO AIRCRAFT; FLIGHT SUITS; PARACHUTES; ARRANGEMENT OR MOUNTING OF POWER PLANTS OR PROPULSION TRANSMISSIONS IN AIRCRAFT
  • B64D37/00—Arrangements in connection with fuel supply for power plant
  • B64D37/02—Tanks
  • B64D37/06—Constructional adaptations thereof
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B64—AIRCRAFT; AVIATION; COSMONAUTICS
  • B64D—EQUIPMENT FOR FITTING IN OR TO AIRCRAFT; FLIGHT SUITS; PARACHUTES; ARRANGEMENT OR MOUNTING OF POWER PLANTS OR PROPULSION TRANSMISSIONS IN AIRCRAFT
  • B64D37/00—Arrangements in connection with fuel supply for power plant
  • B64D37/02—Tanks
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B64—AIRCRAFT; AVIATION; COSMONAUTICS
  • B64D—EQUIPMENT FOR FITTING IN OR TO AIRCRAFT; FLIGHT SUITS; PARACHUTES; ARRANGEMENT OR MOUNTING OF POWER PLANTS OR PROPULSION TRANSMISSIONS IN AIRCRAFT
  • B64D45/00—Aircraft indicators or protectors not otherwise provided for
  • B64D45/02—Lightning protectors; Static dischargers
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16B—DEVICES FOR FASTENING OR SECURING CONSTRUCTIONAL ELEMENTS OR MACHINE PARTS TOGETHER, e.g. NAILS, BOLTS, CIRCLIPS, CLAMPS, CLIPS OR WEDGES; JOINTS OR JOINTING
  • F16B33/00—Features common to bolt and nut
  • F16B33/004—Sealing; Insulation
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16B—DEVICES FOR FASTENING OR SECURING CONSTRUCTIONAL ELEMENTS OR MACHINE PARTS TOGETHER, e.g. NAILS, BOLTS, CIRCLIPS, CLAMPS, CLIPS OR WEDGES; JOINTS OR JOINTING
  • F16B37/00—Nuts or like thread-engaging members
  • F16B37/14—Cap nuts; Nut caps or bolt caps
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16B—DEVICES FOR FASTENING OR SECURING CONSTRUCTIONAL ELEMENTS OR MACHINE PARTS TOGETHER, e.g. NAILS, BOLTS, CIRCLIPS, CLAMPS, CLIPS OR WEDGES; JOINTS OR JOINTING
  • F16B33/00—Features common to bolt and nut

Definitions

• This disclosure relates to methods and articles useful in sealing fasteners, including seal caps and in particular translucent or transparent seals or seal caps.
• the present disclosure provides a method of protecting a fastener comprising the steps of: a) providing a fastener; b) providing a seal cap which defines an interior, wherein the seal cap is optically translucent; c) applying 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.
• the method may additionally comprising the step of: e) curing the sealant by application of actinic radiation to the sealant through the seal cap.
• the fastener protrudes from a first surface of a substrate article and, following steps c), d) and e), every portion of the fastener which protrudes from the first surface of the substrate article is covered by cured sealant or seal cap or both.
• the present disclosure provides a method of protecting a fastener comprising the steps of: f) providing a fastener; g) providing a seal cap which defines an interior, wherein the seal cap is optically translucent, and wherein the interior of the seal cap contains a quantity of an uncured sealant; and h) positioning the seal cap over the fastener such that at least a portion of the fastener resides in the interior of the seal cap.
• the seal cap and uncured sealant recited in step g) are at a temperature of less than 5°C, and wherein the method additionally comprises the step of: i) warming the seal cap and uncured sealant to a temperature of at least 20°C.
• the method additionally comprising the step of: j) curing the sealant by application of actinic radiation to the sealant through the seal cap.
• the fastener protrudes from a first surface of a substrate article and, following step j), every portion of the fastener which protrudes from the first surface of the substrate article is covered by cured sealant or seal cap or both.
• the present disclosure provides a method of protecting a fastener comprising the steps of: k) providing a fastener; 1) providing a seal cap mold which defines an interior; m) applying an uncured sealant to the interior of the seal cap mold or to the fastener or to both, wherein the uncured sealant is translucent; n) positioning the seal cap mold over the fastener such that at least a portion of the fastener resides in the interior of the seal cap mold; and o) curing the sealant by application of actinic radiation to the sealant through the seal cap mold.
• the fastener protrudes from a first surface of a substrate article and, following steps m), n) and o), every portion of the fastener which protrudes from the first surface of the substrate article is covered by sealant.
• the present disclosure provides a protected fastener construction comprising: q) a fastener; r) a seal cap which defines an interior; and s) a cured sealant;
• the seal cap is optically translucent, wherein 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 wherein the interior of the seal cap additionally contains the cured sealant which binds the seal cap to the fastener.
• the fastener protrudes from a first surface of a substrate article and wherein every portion of the fastener which protrudes from the first surface of the substrate article is covered by cured sealant or seal cap or both.
• the first surface is an interior surface of a fuel container of an aircraft.
• the present disclosure provides a protected fastener construction comprising: t) a fastener; and u) a shaped cured sealant; wherein the cured sealant is shaped to form a seal cap; wherein the shaped cured sealant is optically translucent,
• the shaped cured sealant is positioned over and encloses at least a portion of the fastener, wherein the shaped cured sealant is bound to the fastener.
• the fastener protrudes from a first surface of a substrate article and wherein every portion of the fastener which protrudes from the first surface of the substrate article is covered by cured sealant or seal cap or both.
• the first surface is an interior surface of a fuel container of an aircraft.
• the present disclosure provides an application-ready seal cap comprising: v) a seal cap which defines an interior; and w) a quantity of an uncured sealant; wherein the seal cap is optically translucent, and wherein the interior of the seal cap contains the quantity of uncured sealant.
• the seal cap is optically translucent. In some embodiments of the methods or articles of the present disclosure, the seal cap is visibly transparent. In some embodiments of the methods or articles of the present disclosure, the seal cap comprises a polyurethane polymer. In some embodiments of the methods or articles of the present disclosure, the seal cap comprises a polythioether polymer. In some embodiments of the methods or articles of the present disclosure, the seal cap comprises a THV polymer. In some embodiments of the methods or articles of the present disclosure, the seal cap comprises a mixture of a polymer and a nanoparticulate curative.
• the sealant is optically translucent. In some embodiments of the methods or articles of the present disclosure, the sealant is visibly transparent. In some embodiments of the methods or articles of the present disclosure, the sealant comprises a polyurethane polymer. In some embodiments of the methods or articles of the present disclosure, the sealant comprises a polythioether polymer. In some embodiments of the methods or articles of the present disclosure, the sealant comprises a polysulfide polymer. In some embodiments of the methods or articles of the present disclosure, the sealant comprises a mixture of a polymer and a nanoparticulate curative. In some
• the sealant cures to form a material that is optically translucent. In some embodiments of the methods or articles of the present disclosure, the sealant cures to form a material that is visibly transparent.
• the seal cap and sealant comprise different materials.
• Figs, la- Id are photographs taken during a lightning strike test as described in the present Examples, at Example 18, test number 2. The photographs are modified by the addition of a white circle to mark the outside edge of the seal cap.
• Figs. 2a-2d are photographs taken during a lightning strike test as described in the present
• Fig. 3 is an embodiment of a seal cap according to the present invention.
• Figs. 4a-4c are schematic representations of certain embodiments of seal caps according to the present invention.
• Fig. 5a is a schematic representation of an embodiment of a step in a process for making a sealed fastener according to the present invention.
• Fig. 5b is a schematic representation of one embodiment of a sealed fastener according to the present invention. Detailed Description
• the present disclosure provides seal caps, methods of their use, and constructions comprising seal caps.
• a sealant may also function as a barrier to the passage of fluids, particularly where the fastener protrudes into a fluid containment tank, particularly where that fluid is fuel, and most particularly where that tank is on board an aircraft.
• the fastener may also function to prevent or reduce passage of electrical discharge, such as from a lightning strike, into the interior of a fuel tank.
• the seal caps according to the present disclosure may be useful in sealing fasteners in many such applications.
• Figs. 3 and 4a each represent an embodiment of a seal cap 10 according to the present invention.
• the seal caps according to the present invention are translucent.
• the term "translucent” means able to transmit some portion of visible light, typically greater than 20% of light in the 360-750 nm wavelength range, in some embodiments greater than 30%, in some embodiments greater than 40%, and in some embodiments greater than 50%.
• the seal caps according to the present invention are optically transparent, meaning transparent to the extent that the article does not prevent a viewer from resolving an image, e.g., reading text.
• seal caps according to the present invention permit visual inspection for flaws in construction or installation or both.
• 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 5.0 kV/mm, in some embodiments greater than 10.0 kV/mm, in some embodiments greater than 15.0 kV/mm, in some embodiments greater than 30.0 kV/mm, in some embodiments greater than 40.0 kV/mm, and in some embodiments greater than 50.0 kV/mm.
• the use of a material having a higher dielectric breakdown strength permits the manufacture of a lighter seal cap.
• the seal caps according to the present invention are thin-walled.
• the seal caps have an average wall thickness of less than 1.5 mm, in some embodiments less than 1.2 mm, in some embodiments less than 1.0 mm, in some embodiments less than 0.5 mm, in some embodiments less than 0.2 mm, in some embodiments less than 0.1 mm, and in some embodiments less than 0.08 mm.
• the seal caps may be made of any suitable material.
• the material is jet fuel resistant.
• the material has a TB (brittle temperature) below -20°C.
• the seal cap comprises a polyurethane polymer.
• the seal cap comprises a polythioether polymer.
• the seal cap comprises a polysulfide polymer.
• the seal cap comprises a fluorinated thermoplastic polymer.
• the seal cap comprises a THV polymer.
• the seal cap comprises a fluorinated thermoset polymer.
• the seal cap comprises a engineering thermoplastic.
• the seal cap comprises a PEEK polymer.
• the seal cap comprises a mixture of a polymer and a
• the seal cap comprises a mixture of a polymer and a nanoparticulate curative. In some embodiments, the seal cap comprises no fillers or other particulates having an average particle size greater than 10 nm, in some embodiments not greater than 5 nm, and in some embodiments not greater than 1 nm.
• the seal cap and sealant comprise different materials. In some embodiments, the seal cap and sealant do not comprise different materials.
• the seal cap is at least partially filled with sealant.
• seal cap 10 may be filled with sealant 20.
• the seal cap is at least partially filled with sealant shortly before use.
• the seal cap is at least partially filled with sealant and stored in ready-to-use form.
• a filled or partially filled cap is stored at low temperature.
• the filled or partially filled cap must be thawed before use.
• the seal cap is at least partially filled with sealant prior to application to a fastener.
• the seal cap is at least partially filled with sealant after application to a fastener, e.g., by syringe, by a sealant port, or the like. In some embodiments, the seal cap is applied to a fastener after application of sealant to the fastener. In some embodiments, the fastener penetrates a substrate article. In some embodiments, the fastener protrudes from a surface of a substrate article. In some embodiments the substrate article is a composite material. In some embodiments, the substrate article is a epoxy matrix and glass or carbon fiber composite material. In some embodiments, every portion of the fastener which protrudes from the substrate article is covered by cured sealant or seal cap or both. In some embodiments, every portion of the fastener which protrudes from the substrate article is covered by cured sealant.
• seal cap 10 filled with sealant 20 covers fastener 30 which protrudes from substrate article 40. Some excess amount of sealant 22 may be pressed out of seal cap 10 during application.
• the sealant may be any suitable material.
• the material is jet fuel resistant.
• the material has a TB (brittle temperature) below -20°C.
• the sealant comprises a polyurethane polymer.
• the sealant comprises a polythioether polymer.
• the sealant comprises a polysulfide polymer.
• the sealant comprises a mixture of a polymer and a
• the sealant comprises a mixture of a polymer and a nanoparticulate curative.
• the seal cap comprises no fillers or other particulates having an average particle size greater than 10 nm, in some embodiments not greater than 5 nm, and in some embodiments not greater than 1 nm.
• the seal cap material and sealant material may be chosen such that strong bonds are formed between the sealant and the seal cap.
• the sealant material may be chosen such that strong bonds are formed between the sealant and the substrate.
• the sealant material may be chosen such that strong bonds are formed between the sealant and the fastener.
• the sealant is typically cured.
• the sealant is a radiation cured sealant.
• the sealant is cured by application of actinic radiation to the sealant.
• the sealant is cured by application of green light to the sealant.
• the sealant is cured by application of blue light to the sealant.
• the sealant is cured by application of violet light to the sealant.
• the sealant is cured by application of UV light to the sealant.
• the sealant is cured by application of radiation to the sealant through a translucent seal cap.
• the sealant is substantially fully cured in less than 60 seconds, in some embodiments less than 30 seconds, and in some embodiments less than 10 seconds.
• cure is accomplished by addition of a curing agent shortly prior to use.
• cure is accomplished by heat cure at ambient conditions.
• cure is accomplished by heat cure by application of heat from a heat source.
• a combination seal and seal cap is molded in place over a fastener using a seal cap mold.
• the seal cap mold is translucent or transparent to allow inspection and radiation cure of the form-in place seal and seal cap.
• Fig. 5a depicts one embodiment of such a process, wherein seal cap mold 50 containing sealant 60 is located over fastener 30 which protrudes from substrate article 40.
• sealant 60 is cured by application of radiation 70.
• Fig. 5b depicts the completed seal 62 after removal of seal cap mold 50.
• UV ultraviolet
• A-200 A hydrophilic fumed silica, obtained under the trade designation "AEROSIL 200” from Evonik Industries AG, Essen, Germany.
• AC-240 A gray two-part polysulfide-based sealant, having a cured specific gravity of 1.61 , obtained under the trade designation "AEROSPACE SEALANT AC-240 CLASS
• AC-360 A brown two-part polysulfide-based sealant, having a cured specific gravity of
• AC-380 A gray two-part polysulfide-based sealant, having a cured specific gravity of 1.10, obtained under the trade designation "AEROSPACE SEALANT AC-380 CLASS B" from 3M Company.
• APTIV A 2-mil (50.8 m) unfilled semi-crystalline polyetheretherketone (PEEK) film, obtained under the trade designation "APTIV 1000-050G” from Victrex USA, Inc., West Conshohocken, Pennsylvania.
• DABCO-33LV A solution of 33% triethylenediamine and 67% dipropylene glycol, obtained under the trade designation "DABCO-33LV” from Air Products & Chemicals, Inc., Allentown, Pennsylvania.
• DEN-431 A semi-solid reaction product of epichlorohydrin and phenol-formaldehyde
• novolac obtained under the trade designation "D.E.N. 431" from Dow Chemical Company, Midland, Michigan.
• DMDO l,8-Dimercapto-3,6-dioxaoctane, obtained from Arkena, Inc., King of Prussia,
• DSW An aluminosilicate clay, obtained under the trade designation "DRAGONITE
• DVE-2 Diethyleneglycol divinylether, obtained from BASF Corp., Florham Park, New
• DVE-3 Triethyleneglycol divinylether, obtained under the trade designation "RAPI-
• E-8240 A very low viscosity epoxy phenol novolac resin, obtained under the trade
• MEK Methyl ethyl ketone.
• NCC Nanoparticle (70 - 100 nm) calcium carbonate, obtained under the trade
• PR- 1776 A brown two-part polysulfide-based sealant, having a cured specific gravity of
• TAC Triallylcyanurate, obtained from Sartomer, Inc., Exton, Pennsylvania.
• THV-200 A colorless transparent fluoroelastomer, obtained under the trade designation
• THV-200W White pigmented THV 200, meeting the specifications for Federal Standard 595B,
• THV-500 A colorless fluoroelastomer, obtained under the trade designation "THV 500" from 3M Company.
• VAZO-67 2,2'-azobis(2-methylbutyronitrile), obtained under the trade designation "VAZO- 67" from E.I. du Dupont de Nemours and Company, Wilmington, Delaware.
• DVE-3 313.13 g (1.55 moles) DVE-3 was then added drop-wise to the flask over 45 minutes, keeping the temperature between 68 - 80°C.
• Vazo 67 is added in approximately 0.15 g units over approximately 6 hours for a total of 0.4 - 0.6 g. The temperature is raised to 100°C and the material degassed for approximately 10 minutes.
• the resultant polythioether is approximately 3200 MW with 2.2 functionality.
• a liquid polythioether polymer was prepared as follows: Into a 1 -liter round bottom flask equipped with an air driven stirrer, thermometer, and a dropping funnel, was added 407.4 grams (2.24 moles) DMDO, 12.63 grams (0.05 moles) TAC and 0.1 grams of VAZO-67. This mixture was stirred at 60°C for approximately 45 minutes. To this mixture, 380 grams (1.88 moles) DVE-3 was added drop wise over 45 minutes. Additional 0.3 grams VAZO-67 was added in small increments and the mixture heated at 70 - 80°C for about 6 hours, followed by 10 minutes of vacuum degassing at 100°C. The resulting liquid polythioether polymer had a T g of less than - 40°C, a viscosity of 100 Poise (10 Pa.s) and a thiol equivalent weight of 1,291 grams/equivalent.
• the panels were drilled such that there was an overlap of 1 inch (2.54 cm) with the fasteners uniformly spaced along the center of the overlap joint.
• the two panels halves were joined together using the above mentioned shank and collar assembly, Part No. "HL94W6", also from Peerless Aerospace Fastener Co.
• the joint was wetted with AC-240 placed between the two panels and into the holes before tightening the fasteners.
• the final test panel had 10 fasteners centrally located in the overlap joint spaced uniformly across its 10 inch (25.4 cm) width.
• Optical transmission was used to measure the opacity of the cured seal caps.
• a bench top colorimeter, model "COLOR I” obtained from X-Rite, Inc., Grand Rapids, Michigan, with a measuring range of 750-360 nm in 10 nm increments, used the full frequency sweep and averaged to give a single value for percent transmission.
• An appropriate aperture was selected in the machine to give the maximum area for transmission while being able to hold the cap in the aperture.
• the equipment was calibrated using standard methods.
• the output from the test is a transmission value for each frequency from 360 nm to 750 nm. Table 2 shows the data as an average of the 360-750 nm frequency range.
• Translucent polyurethane seal caps were prepared as follows: A Shore 80 polyurethane casting compound, obtained under the trade designation "SMOOTH-ON CRYSTAL CLEAR 200" from McMaster-Carr Supply Company, Elmhurst, Illinois, was then poured into the female tool of a 6 by 8 inch (15.24 by 20.32 cm) 4-cavity stainless-steel seal cap mold, the cavities were designed to give a frusto-conical shaped cap with a base diameter of 27mm a height of 23mm and a wall thickness of 2.5mm. The male tool closed the mold and the casting compound cured at 70°F (21.1 °C) for 24 hours. The resulting translucent seal cap was then removed from the tool.
• Example 2 A Shore 80 polyurethane casting compound, obtained under the trade designation "SMOOTH-ON CRYSTAL CLEAR 200" from McMaster-Carr Supply Company, Elmhurst, Illinois, was then poured into the female tool of a 6 by 8 inch (15.24 by 20.32 cm) 4-cavity stainless-ste
• Translucent polythioether seal caps were prepared as follows: 100 grams PTE- 1 was
• Translucent polythioether seal caps were prepared as follows: 100 grams PTE-2 was
• Example 3 The process generally described in Example 3 was repeated, wherein the polymer mixture was allowed to pre-react for 2 hours before closing the mold and curing. The resulting translucent seal cap was then removed from the tool.
• a 40 ml. amber glass vial was charged with 7.055 grams DMDO, 5.252 grams DVE-2 and 0.914 grams T AC at 2 rC. To this was added 0.132 grams 1-819. The vial was then sealed and placed on a laboratory roller mill for 10 minutes until the 1-819 had dissolved.
• the curable composition was injected into the female tool of the 8 by 8 inch (20.32 by 20.32 cm) 9-cavity aluminum seal cap mold, and a clear epoxy male tool was used to close the mold.
• the mixture was then cured by exposure, through the male tool, to a 455 nm LED light source, model "CF 2000" from Clearstone Technologies, Inc., Minneapolis, Minnesota, for 1 minute at a distance of 0.2 inches (0.51 cm). The resulting translucent seal cap was then removed from the tool.
• a 50:50 by weight mixture of THV-200 and MEK was brushed onto a single impression male tool dimensioned to give a frusto-conical shaped cap with a base diameter of 10mm and a height of
• a curable polythioether composition was prepared as follows. A 40 ml. amber glass vial was charged with 7.000 grams DMDO, 4.349 grams DVE-2 and 1.812 grams TAC at 21°C. To this was added 0.132 grams 1-819. The vial was then sealed and placed on a laboratory roller mill for 10 minutes until the 1-819 had dissolved.
• a UV curable seal cap was made as follows. The curable composition was injected into the female tool of the 8 by 8 inch (20.32 by 20.32 cm) 9- cavity aluminum seal cap mold. A clear epoxy male tool was then used to close the mold and the composition cured by exposure, through the male tool, to the 455 nm LED for 1 minute at a distance of 0.2 inches (0.51 cm). The resulting translucent seal cap was then removed from the tool.
• a curable polythioether composition was prepared as generally described in Example 7, wherein after the resin and initiator were dissolved, 1.329 grams A-200 was homogeneously dispersed in the composition by means of a high speed mixer for 1 minute.
• a UV curable seal cap was made as follows. The curable composition was injected into the female tool of the 8 by 8 inch (20.32 by 20.32 cm) 9-cavity aluminum seal cap mold. A clear epoxy male tool was then used to close the mold and the composition cured by exposure, through the male tool, to the 455 nm LED for 1 minute at a distance of 0.2 inches (0.51 cm). The resulting translucent seal cap was then removed from the tool.
• a curable polythioether composition was prepared as generally described in Example 7, wherein after the resin and initiator were dissolved, 1.329 grams DSW was homogeneously dispersed in the composition by means of a high speed mixer for 1 minute.
• a UV curable seal cap was made as follows. The curable composition was injected into the female tool of the 8 by 8 inch (20.32 by 20.32 cm) 9-cavity aluminum seal cap mold. A clear epoxy male tool was then used to close the mold and the composition cured by exposure, through the male tool, to the 455 nm LED for 1 minute at a distance of 0.2 inches (0.51 cm). The finished cap was removed from the tool providing a translucent seal cap.
• a curable polythioether composition was prepared as generally described in Example 9, wherein the amount of DSW was increased to 2.659 grams.
• a UV curable seal cap was made as follows. The curable composition was injected into the female tool of the 8 by 8 inch (20.32 by 20.32 cm) 9-cavity aluminum seal cap mold. A clear epoxy male tool was then used to close the mold and the composition cured by exposure, through the male tool, to the 455 nm LED for 1 minute at a distance of 0.2 inches (0.51 cm). The resulting translucent seal cap was then removed from the tool.
• a curable polythioether composition was prepared as generally described in Example 9, wherein the amount of DSW was increased to 3.988 grams.
• a UV curable seal cap was made as follows. The curable composition was injected into the female tool of the 8 by 8 inch (20.32 by 20.32 cm) 9-cavity aluminum seal cap mold. A clear epoxy male tool was then used to close the mold and the composition cured by exposure, through the male tool, to the 455 nm LED for 1 minute at a distance of 0.2 inches (0.51 cm). The resulting translucent seal cap was then removed from the tool.
• a curable polythioether composition was prepared as follows. A 40 ml. amber glass vial was charged with 7.000 grams DMDO, 5.212 grams DVE-2 and 0.289 grams ODY at 21°C. To this was added 0.125 grams 1-819. The vial was then sealed and placed on a laboratory roller mill for 10 minutes until the 1-819 had dissolved. The curable composition was injected into the female tool of the 8 by 8 inch (20.32 by 20.32 cm) 9-cavity aluminum seal cap mold. A clear epoxy male tool was then used to close the mold and the composition cured by exposure, through the male tool, to the 455 nm LED for 1 minute at a distance of 0.2 inches (0.51 cm). The resulting translucent seal cap was then removed from the tool.
• a curable polythioether composition was prepared as generally described in Example 7, wherein after the resin and initiator were dissolved, 1.329 grams NCC was homogeneously dispersed in the composition by means of a high speed mixer for 1 minute.
• a UV curable seal cap was made as follows. The curable composition was injected into the female tool of the 8 by 8 inch (20.32 by 20.32 cm) 9-cavity aluminum seal cap mold. A clear epoxy male tool was then used to close the mold and the composition cured by exposure, through the male tool, to the 455 nm LED for 1 minute at a distance of 0.2 inches (0.51 cm). The resulting translucent seal cap was then removed from the tool.
• AC-380 sealant mixture was prepared in a 10: 1 base: accelerator weight ratio at 70°F (21.1°C) and injected into the female tooling of the 8 by 8 inch (20.32 by 20.32 cm) 9-cavity aluminum seal cap mold.
• the male tooling closed the mold and the sealant cured for approximately 12 hours at 75°F (23.9°C), followed by 1 hour at 130°F (54.4°C), after which the mold was cooled to room temperature before opening and removing the opaque seal caps.
• a white fluorinated polymer film was prepared by feeding a uniform mixture of pellets having 97 weight percent THV-500 and 3 weight percent THV-200W into a 1.9 cm Haake extruder. The extruder was run to give a uniform 43 m film supported by a 127 um polyethylene backing film. The caps were made using a vacuum forming table. The unsupported THV film was positioned and clamped over the single impression male tool, on the vacuum table. The film was then heated to 400°F (204.4°C) using radiant heat. After the film started to sag the tool was driven up into the film and a vacuum applied to pull the film over the tool. The opaque film was allowed to cool to 21°C, removed from the male tool and trimmed, resulting in an opaque seal cap. Filled Translucent Seal Caps Examples.
• a clear resin was made as follows. 100 grams PTE-2 was homogeneously mixed with 6.78 grams GE-30, 4.52 grams E-8220 and 1.00 gram DABCO-33LV at 21°C. Part of this mixture was then poured into a translucent polythioether seal cap made according to Example 3. The filled seal cap assembly was then placed onto a fastener on the composite panel and cured at 21°C for 24 hours. This resulted in a fastener protected by a translucent cured seal cap. Example 19.
• Example 3 The translucent seal cap of Example 3 was filled with opaque resin AC-360. The filled seal cap assembly was then placed onto a fastener on the composite panel and cured at 21°C for 24 hours. This resulted in a fastener protected by a translucent cured cap with an opaque internal sealant.
• a UV curable thiol-yne resin prepared as follows. A 40 ml. amber glass vial was charged with 7.000 grams DMDO, 5.212 grams DVE-2 and 0.2894 grams ODY at 21°C. To this was added 0.125 grams 1-819. The vial was then sealed and placed on a laboratory roller mill for 10 minutes until the 1-819 had dissolved. Part of this mixture was then poured into a translucent seal cap made according to Example 5. The filled seal cap assembly was then placed onto a fastener on the composite panel and cured by exposure to the 455 nm LED for 30 seconds at a distance of approximately 1-inch (2.54 cm) from the composite panel. This resulted in a fastener protected by a translucent cured seal cap.
• a clear thiol-ene resin composition was prepared as follows. A 40 ml. amber glass vial was charged with 7.000 grams DMDO, 4.3494 grams DVE-2 and 1.8124 grams TAC at 21°C. To this was added 0.132 grams 1-819. The vial was then sealed and placed on a laboratory roller mill for 10 minutes until the 1-819 had dissolved. Part of this mixture was then poured into a translucent seal cap made according to Example 6. The filled seal cap assembly was then placed onto a fastener on the composite panel and cured by exposure to the 455 nm LED for 30 seconds at a distance of approximately 1-inch (2.54 cm) from the composite panel. This resulted in a fastener protected by a translucent cured seal cap.
• Example 6 The translucent seal cap of Example 6 was filled with opaque resin AC-240. The filled seal cap assembly was then placed onto a fastener on the composite panel and cured at 21°C for 24 hours. This resulted in a fastener protected by a translucent cured seal cap with an opaque sealant.
• a fastener protected by a translucent cured seal cap was made according to the general procedure described in Example 21 , wherein the translucent seal cap Example 6 was substituted with a translucent seal cap made according to Example 3.
• Example 24 was made according to the general procedure described in Example 21 , wherein the translucent seal cap Example 6 was substituted with a translucent seal cap made according to Example 3.
• a fastener protected by a translucent cured seal cap was prepared as generally described in Example 20, wherein the translucent seal cap made according to Example 5 was substituted with a translucent seal cap made according to Example 12.
• a curable thiol-ene resin composition was prepared as follows. A 40 ml. amber glass vial was charged with 7.000 grams DMDO, 4.439 grams DVE-2 and 1.812 grams TAC at 21°C. To this was added 0.132 grams 1-819. The vial was then sealed and placed on a laboratory roller mill for 10 minutes until the 1-819 had dissolved. The thiol-ene sealant formulation was injected into release coated, 13.5 mm diameter by 12 mm high, frusto-conical quartz glass cap mold. The cap was then placed onto a fastener on the composite panel and cured by exposure to the 455 nm LED for 30 seconds at a distance of approximately 1-inch (2.54 cm) from the composite panel. After curing the quartz glass cap mold was released, resulting in a fastener protected by a translucent cured seal cap.
• a fastener protected by a translucent cured seal cap was prepared as generally described in
• Example 25 wherein the thiol-ene chemistry was substituted by a thiol-yne chemistry as follows.
• Curable polythioether composition was prepared as follows. A 40 ml. amber glass vial was charged with 7.000 grams DMDO, 5.212 grams DVE-2 and 0.2894 grams ODY at 21°C. To this was added 0.125 grams 1-819. The vial was then sealed and placed on a laboratory roller mill for 10 minutes until the 1-819 had dissolved.
• the opaque seal cap of Comparative A was filled with opaque resin AC-380.
• the filled seal cap assembly was then placed onto a fastener on the composite panel and cured at 21°C for 24 hours. This resulted in a fastener protected by an opaque cured seal cap with an opaque sealant.
• a sheet of APTIV brand PEEK film was positioned over the single impression male tool that had been pre-heated to 200°C.
• the film was then softened and deformed over the male tool by means of a hot air gun.
• a pre-formed cap was then pressed over the softened film and male tool, after which the assembly was cooled to approximately 21 °C.
• the pre-formed cap was then removed, revealing a light weight, translucent PEEK film cap, which was then removed from the male tool and trimmed.
• a filled translucent seal cap was prepared as generally described in Example 18, wherein the polythioether seal cap was replaced by a PEEK seal cap made according to Example 27.
• Figs. 1-2 are exemplary photographs of Examples 18, Test No. 2 and Comparative E, Test No. 3, respectively, of the lightning strike tests.
• the translucent cap and translucent filler enabled observation of the plasma formation on the fastener inside the cap.
• Fig. 1 demonstrates a lightning strike test on Example 18; test number 2.
• the red circle on each photo shows the outside edge of the seal cap.
• the images progress from top left: the start of the strike, top right: full intensity plasma, discharge was contained within the cap, light outside the cap are reflections on other surfaces. Bottom left the plasma starting to decay and bottom right close to completion of the strike.
• Fig. 2 demonstrates a lightning strike test on Comparative E; test number 3.
• the images progress in the same sequence as Example 18 in Fig. 1. However, because the seal cap is opaque, the plasma discharge and decay cannot be observed.
• the present disclosure includes following numbered list of illustrative embodiments:
• a method of protecting a fastener comprising the steps of:
• seal cap which defines an interior, wherein the seal cap is optically translucent
• step c) is performed before step d).
• step d) is performed before step c).
• step of curing the sealant comprises application of actinic radiation to the sealant through the seal cap.
• step of curing the sealant comprises application of blue, violet or UV light to the sealant through the seal cap.
• a method of protecting a fastener comprising the steps of:
• seal cap which defines an interior, wherein the seal cap is optically translucent, and wherein the interior of the seal cap contains a quantity of an uncured sealant; and h) positioning the seal cap over the fastener such that at least a portion of the fastener resides in the interior of the seal cap.
• step g) the seal cap and uncured sealant recited in step g) are at a temperature of less than 5°C, and wherein the method additionally comprises the step of:
• step j) of curing the sealant comprises application of actinic radiation to the sealant through the seal cap.
• step j) of curing the sealant comprises application of blue, violet or UV light to the sealant through the seal cap.
• seal cap is translucent to the extent that the average light transmission through the cap in the 360-750 nm wavelength range is at least 20%. 18. The method according to any of embodiments 1- 16 wherein the seal cap is translucent to the extent that the average light transmission through the cap in the 360-750 nm wavelength range is at least 30%. 19. The method according to any of embodiments 1- 16 wherein the seal cap is translucent to the extent that the average light transmission through the cap in the 360-750 nm wavelength range is at least 40%.
• seal cap comprises a polysulfide polymer.
• seal cap comprises a fluorinated thermoplastic polymer.
• seal cap comprises a fluorinated thermoset polymer.
• seal cap comprises a engineering thermoplastic.
• seal cap comprises a mixture of a polymer and a nanoparticulate filler. 31. The method according to any of the preceding embodiments wherein the seal cap comprises a mixture of a polymer and a nanoparticulate curative.
• a method of protecting a fastener comprising the steps of:
• step m) is performed before step n).
• step n) is performed before step m).
• sealant comprises a polyurethane polymer.
• sealant comprises a polythioether polymer.
• sealant comprises a mixture of a polymer and a nanoparticulate filler.
• sealant comprises a mixture of a polymer and a nanoparticulate curative.
• a protected fastener construction comprising:
• seal cap is optically translucent
• 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 wherein the interior of the seal cap additionally contains the cured sealant which binds the seal cap to the fastener.
• a protected fastener construction comprising:
• the shaped cured sealant is optically translucent
• An application-ready seal cap comprising:
• seal cap is optically translucent
• the interior of the seal cap contains the quantity of uncured sealant.
• the application-ready seal cap according to embodiment 92 wherein the seal cap is translucent to the extent that the average light transmission through the cap in the 360-750 nm wavelength range is at least 40%.
• the application-ready seal cap according to any of embodiments 92- 122 maintained at a temperature of less than 5°C.

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• Engineering & Computer Science (AREA)
• General Engineering & Computer Science (AREA)
• Aviation & Aerospace Engineering (AREA)
• Mechanical Engineering (AREA)
• Sealing Material Composition (AREA)
• Casting Or Compression Moulding Of Plastics Or The Like (AREA)
• Lining Or Joining Of Plastics Or The Like (AREA)

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• 2014
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