JP7597708B2 - Fastener sealing materials and methods - Google Patents

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application is a continuation-in-part of U.S. Provisional Patent Application No. 62/437,967, entitled "Fastener Sealing Material and Method," filed Dec. 18, 2017, which claims the benefit of and priority to U.S. Provisional Patent Application No. 62/437,967, entitled "Fastener Sealing Material and Method," filed Dec. 22, 2016, the disclosures of which are incorporated herein in their entireties.

The present disclosure relates to materials for sealing fasteners in place to prevent, for example, the ingress of water, moisture and debris into the assembly in which the fastener is used, and methods for applying such sealing materials.

Fasteners are used, for example, to secure components together. In one example, fasteners are used to secure components within electronic devices, such as smartphones, tablets, pads, etc. As devices get smaller, the components also get smaller. The fasteners to secure the components get smaller. And while the devices get smaller, the need to keep the components free of water, moisture, and debris remains. In fact, many such smaller devices require an even higher level of assurance that the components are well isolated from their surroundings in order to function properly.

There are known sealing materials. However, these materials are provided in powder form, such as nylon 11 powder. These materials require that the fastener be heated before or after application of the material so that the material melts and flows around the underside of the fastener's head. These materials and methods of sealing material application work better for larger fasteners. However, for small and ultra-small fasteners - fasteners having head diameters of 2.0 mm (M2.0) to 3.0 mm (M3.0) and 0.8 mm (M0.8) to 1.4 mm (M1.4), respectively, with shank diameters approximately 1/2 the head diameter, these materials and methods can cause problems. Due to over-application problems, rejection rates can be as high as 10 to 20 percent. This rejection rate is significantly higher than acceptable, especially in that the fastener can only be modified once, e.g., the material can only be removed once, and the sealing material can only be reapplied once.

In other applications, for example using larger fasteners, powder application of sealant to the fastener works well but has drawbacks. For example, in some applications the sealant may be exposed to high temperatures and may not meet certain requirements when exposed to these high temperatures. In the automotive industry, fastener sealants may be required to meet certain specifications, such as maintaining a confined environment of at least 85°C (185°F), maintaining high adhesion to the fastener, exhibiting minimal compression set, maintaining the ability to withstand repeated installation and removal (tightening and loosening), maintaining physical integrity (e.g., no cracks) while maintaining a desirable physical appearance.

Known sealants include, for example, polymeric coatings and preformed elastomeric washers, such as silicones, etc. Often such preformed washers cannot withstand temperature conditions while maintaining physical integrity, repeated installation and removal, and minimal or no compression set.

Thus, there is a need for a material that can be used to seal fasteners in an assembly and provide an acceptable seal against environmental conditions, such as water, moisture, dirt, etc. Desirably, such a material can be applied to the fastener in a liquid form and can easily flow around the underside (seating surface) of the fastener head without overspraying to completely cover the underside of the head, if necessary. Even more desirably, such a material cures quickly, and the method of application is a manufacturing process with no or minimal heat. Even more desirably, such a material allows for the reuse of the fastener; that is, the fastener can be applied, removed, and reapplied while the sealing material maintains its sealing properties.

Various embodiments of the present disclosure provide fastener sealing materials for application to miniature and micro-miniature fasteners. The sealing materials are formulated from liquid applied acrylate materials such as acrylated urethanes and acrylated polyesters. The liquid applied materials are cured using a UV or LED light source and without the use of heat.

In embodiments, the viscosity of the material is less than about 1500 centipoise. The viscosity of the material may be about 500-2000 centipoise. Such a viscosity allows the sealant to wick somewhat into the fastener shank, if desired. This configuration may be required in certain applications. In other applications, wicking is unnecessary or undesirable.

A superhydrophobic material may be included as an additive. Other additives may include suitable photoinitiators and may include pigments, flow improvers and heat resistant additives present in amounts that do not interfere with the curing of the material.

In embodiments, the material cures on the fastener in about 2-20 seconds, preferably about 2-10 seconds, more preferably about 2-5 seconds or less, when exposed to UV or LED light at temperatures of about 66° C. (about 151° F.) or less, preferably about room temperature 25° C. (about 77° F.). Fasteners to which the sealing material is applied retain their sealing properties after multiple installations and removals. For example, fasteners to which the sealing material is applied retain their sealing properties after at least three installations and removals.

In some embodiments, the fastener sealing material, when applied to the fastener, wicks into a portion of the shank of the fastener. In other embodiments, the sealing material does not wick into a portion of the fastener shank. The fastener sealing material, when applied to the fastener, may also form a locking material for the fastener. A method of making a fastener having a sealing material applied thereto is also desired.

Other aspects, objects and advantages will become more apparent from the following detailed description taken in conjunction with the drawings.

1 is a photograph of a fastener having a known prior art sealing material applied thereto. 1 is a photograph of a fastener having a known prior art sealing material applied thereto. 1 is a photograph of a fastener having a known prior art sealing material applied thereto. 1 is a photograph of a fastener having a known prior art sealing material applied thereto. 1 is a photograph of a fastener having a known prior art sealing material applied thereto. 1 is a photograph of a fastener having a known prior art sealing material applied thereto. 1 is a photograph of a fastener having a known prior art sealing material applied thereto. 1 is a photograph of a fastener having a known prior art sealing material applied thereto. 1 is a photograph of an M1.4 fastener seat coated with an embodiment of the fastener sealing material of the present invention, showing flow coating on the underside of the fastener head. 1 is a photograph of the underside or underhead (seat) surface of an M1.4 fastener prior to application of the fastener sealing material of the present invention. 1 is a photograph of the underside or underhead (seat) surface of an M1.4 fastener after application of fastener sealing material. 1 is a photograph of the top surface of an M1.0 fastener prior to application of the sealing material of the present invention. 1 is a photograph of the top surface of an M1.0 fastener after application of the sealing material of the present invention. 1 is a photograph of the underside of the head and a portion of the shank of a size 4-40 fastener after application of the fastener sealing material of the present invention. 1 is a photograph of a submerged test structure. 1 is a photograph of the test chamber. 1 is a photograph of the test chamber. 1 is a photograph showing the ability of the material to wick into the shank of a fastener; 1 is a photograph showing the ability of a material to wick into the shank of a fastener, the photograph showing a fastener with a sealing material applied thereto and showing that the material has wicked into a portion of the shank of the fastener; Photograph of the fastener with the original sealant material and blue patch (locking mechanism/material). 4 is a graphical representation of the results of seal tests conducted at various temperatures on a control group of fasteners and a group of fasteners provided with a sealant of the present invention. 4 is a graphical representation of the results of crack tests conducted at various temperatures on a control group of fasteners and a group of fasteners provided with a sealant of the present invention.

These and other features and advantages of the present disclosure will become apparent from the following detailed description taken in conjunction with the appended claims.

The present disclosure is susceptible of embodiment in various forms. However, presently preferred embodiments are described with the understanding that the disclosure is to be considered as illustrative and is not intended to limit the disclosure to the specific embodiments described.

In one aspect, the need to provide a seal between a fastener and the component being fastened is paramount, and especially important in today's electronic devices. This need is exacerbated by the ever-decreasing size of components in these devices. Known materials are not sufficient for ultra-miniature fasteners, which are fasteners having a head diameter of 0.8 mm (M0.8) to 1.4 mm (M1.4) and a shank diameter that is approximately 1/2 the head diameter. The materials may also not be sufficient for miniature fasteners, which are fasteners having a head diameter of approximately 2.0 mm (M2.0) to 3.0 mm (M3.0). It is also anticipated that ultra-miniature fasteners may become even smaller in the future.

Thus, embodiments of the sealing material of the present invention include, as a primary material, acrylates, e.g., acrylated materials, e.g., acrylated polyesters, aliphatic and aromatic acrylated urethanes, e.g., acrylated urethanes, e.g., those available from Dymax Corporation under the product names MULTI-CURE® 6-621 and 6-630 and those available from Advanced Adhesive Systems, Inc. of Newington, Conn. under product numbers AAS 81082A and 81091B. Superhydrophobic material additives can be added to acrylate materials, e.g., acrylated urethanes, to increase resistance to water and moisture.

In one embodiment, a formulation of about 75-99 weight percent acrylated urethane and about 1-24 weight percent superhydrophobic material has been found to form a formulation suitable for application to small and micro fasteners. In an embodiment, additional additives, such as pigments, e.g., black pigments, flow improvers, and anti-counterfeiting agents, may be added to the formulation in relatively small amounts. A curing agent, such as a photoinitiator suitable for curing the material by exposing the material applied to the fastener to UV or LED light, is present in the material. A flow improver may or may not be necessary if the viscosity of the sealing material is such that the sealing material flows appropriately and desirably, depending on the size of the fastener, the material coating thickness, and the desired wicking characteristics, etc. A heat resistant additive may also be included in the formulation to prevent further chemical and/or physical changes to the material after curing. It will be understood that any additives used should not be of a type that will interfere with the UV or LED curing step.

Advantageously, such formulations have been found to provide a low viscosity liquid material that better lends itself to high speed application with fewer rejects. Such materials have low viscosities, for example, of about 500-2000 centipoise, allowing for high speed application onto small threads. The viscosity of such materials is only slightly more viscous than water.

Moreover, such materials can be cured in a relatively short time without the use of heat. Indeed, the materials can be cured using an ultraviolet light source (at the appropriate wavelength of ultraviolet light) or an LED light source, as needed and based on the type of photoinitiator used. It has been found that the materials can be cured on small and micro-small fasteners in about 2-20 seconds, preferably about 2-10 seconds, and even more preferably about 2-5 seconds, without the use of heat. Unlike known sealing materials that require application to a heated fastener or heating after application to the fastener, the materials of the present invention cure in about 2-20 seconds, 2-10 seconds, or 2-5 seconds at temperatures below about 66° C. (about 151° F.), preferably at about room temperature of 25° C. (about 77° F.). Thus, curing can be performed without the need for induction or other types of heating.

It has been observed that fasteners having sealing materials such as nylon applied using heat methods that can require temperatures as high as 375°F to 450+°F to melt the nylon can exhibit bubbles in the decorative finish on the threads.

Furthermore, unlike known sealing materials that are applied as a powder, the sealing material of the present invention is applied as a liquid. Thus, due to the low viscosity, when the material is applied to a fastener, such as the underside (e.g., seat) of the fastener's head, the material can be formulated to flow easily around the entire underside of the head, thus providing a completely wetted surface ready for curing. It will be appreciated that the material can be formulated, for example, with flow additives to make it slightly less flowable and not wick to the seat. Such a formulation can be advantageous during application, such as when the fastener's threads extend completely to the underside of the head or seat. Additionally, the material is free of solvents, halogens, polyvinyl chloride (PVC), REACH environmentally hazardous substances (REACH SVHC), phthalates, bisphenol A (BPA), and is RoHS (Restriction of Hazardous Substances) compliant.

It has been found that miniature and micro-miniature fasteners with the sealing material of the present invention have better waterproofing performance and that the cured material has very good adhesion to metal. It has also been found that fasteners with the sealing material of the present invention exhibit good adhesion to steel and better durability for multiple installations, i.e., the fasteners can be installed and removed multiple times and the material remains in place with a high degree of integrity such that the sealing properties of the fastener to which the material is applied are maintained. It has also been observed that the sealing material of the present invention exhibits good water resistance and high temperature resistance, for example, up to about 300°F (about 150°C).

The adhesive performance of the sealant to the fastener can be further enhanced so that the fastener and sealant retain their properties after multiple installations. It has been found that performance after the first test is improved if the fastener undergoes a plasma treatment process prior to application of the sealant to the fastener. These pre-plasma treated fasteners have significantly reduced sealant failure after multiple installations and removals. Adhesion performance can also be enhanced using internal (chemical solution) additives and treatments. Suitable treatments include treatment with adhesion promoters.

Tests were conducted using the sealing material of the present invention on M1.0 fasteners to determine the effectiveness of the sealing material of the present invention. A test device was constructed that included a submerged test structure or tank (Figure 5) and a submerged test chamber (Figures 6A and 6B). In the test device, a clear plastic plate was secured to a steel chamber by ten M1.0 fasteners that had the sealing material applied to them. In each test, the sealed chamber was submerged in a column of water to a depth of one meter for a period of time in minutes. Four types of tests were conducted:

In the first test, the fasteners were installed. The chamber was submerged for 30 minutes. After the chamber had been submerged for 30 minutes, it was removed from the tank and examined from the bottom through the plastic cover to ensure there were no leaks. After the submersion test, the chamber was placed in an oven at about 195°F (90°C) for 10 minutes until the surface reached about 122°F (50°C). The chamber was then removed from the oven. A small amount of water was dripped onto the plastic cover. After 45 seconds, the water was wiped off the plastic cover to ensure there were no signs of water vapor or droplets in the chamber.

In a second test, the fasteners were installed and removed four times to demonstrate durability over multiple installations. A water submersion test was then performed. After the final installation, the chamber was submerged for 30 minutes to a depth of approximately one meter. After submersion, the chamber was removed from the tank and examined from the bottom through the plastic cover to ensure there were no leaks. The chamber was then placed in an oven at approximately 195°F (90°C) for 10 minutes until the test fixture reached approximately 122°F (50°C). The test device was then removed from the oven. A small amount of water was dripped onto the plastic cover. After 45 seconds, the water was wiped off the plastic cover to ensure there were no signs of water vapor or droplets in the chamber.

In the third test, the fasteners were tightened to the plate. The chamber was conditioned. For example, the chamber was placed in a mechanical oven at a temperature of about 175°F (80°C) for 24 hours. After conditioning, the chamber was allowed to return to room temperature before conducting the submersion test. The chamber was then submerged for about 30 minutes to a depth of about 1 meter. After submersion, the chamber was removed from the tank and examined from the bottom through the plastic cover to ensure there were no leaks. The chamber was then placed in an oven at about 195°F (90°C) for 10 minutes until the surface reached about 122°F (50°C). The chamber was then removed from the oven. A small amount of water was dripped onto the plastic cover. After 45 seconds, the water was wiped off the plastic cover to ensure there were no signs of water vapor or droplets in the chamber.

In another test, the fasteners were tightened to the plate. The chamber was conditioned. For example, the chamber was placed in a mechanical oven at a temperature of about 250°F (120°C) for three hours. After conditioning, the chamber was allowed to return to room temperature before conducting the submersion test. The chamber was then submerged for about 30 minutes to a depth of about one meter. After submersion, the chamber was removed from the tank and examined from the bottom through the plastic cover to ensure there were no leaks. The chamber was then placed in an oven at about 195°F (90°C) for 10 minutes until the surface reached about 122°F (50°C). The chamber was then removed from the oven. A small amount of water was dripped onto the plastic cover. After 45 seconds, the water was wiped off the plastic cover to ensure there were no signs of water vapor or droplets in the chamber.

In yet another test of fasteners where the fasteners were plasma treated and material from Advanced Adhesive Systems, Inc. was used, after application and curing of the material, the fasteners were installed and removed three times at room temperature. The fasteners and plates were then tested at 8 psi and 16 psi for 60 seconds and checked for leakage. No leakage was observed. The samples were then heated in an oven at 120°C for 3 hours and then retested at 8 psi and 16 psi for 60 seconds and checked for leakage. No leakage was observed. The adhesion of the sealant material to the fasteners was also checked. The material could not be removed from the seat of the fastener. A similar test was performed following the same protocol, except the fasteners were heated in an oven at 80°C for 12 hours instead of 120°C for 3 hours.

The results of each test showed that no condensation or leakage was observed. Therefore, it was determined that there was no moisture inside the chamber and that no water had entered the chamber.

It is also envisioned that sealing materials may be formulated for use with larger fasteners. For example, formulations for larger fasteners may use as the primary material an acrylate or acrylated urethane, such as those available under the product designations DUAL-CURE 9481-E and 9482 from Dymax Corporation or the materials described above by Advanced Adhesive Systems. These acrylated urethanes have been found to exhibit extremely good adhesion to metals while retaining the advantageous characteristics of excellent waterproofing performance, as well as high water, chemical and heat resistance. In addition, the use of these materials provides sealing materials that exhibit excellent adhesion to steel and excellent durability for multiple installations with a high degree of integrity such that the sealing properties of the fastener to which the material is applied are maintained.

As mentioned above, one advantageous feature of an embodiment of the sealing material of the present invention is its ability to wick into a portion of the fastener shank. Figures 7A and 7B are photographs illustrating the ability of an embodiment of the material to wick into the shank of a fastener. Figure 7A shows a fastener before application of the sealing material of the present invention. Figure 7B shows a fastener with that embodiment of the sealing material applied to the fastener and shows that the material has wicked into a portion of the shank of the fastener to form a cone-like shape between the shank or threads near the head of the fastener and the fastener head. Such wicking may be desirable or required in certain applications.

In another aspect, the sealing material includes as a base material an acrylate, e.g., an acrylated material, e.g., acrylated polyesters, aliphatic and aromatic acrylated urethanes, e.g., acrylated urethanes, e.g., urethane acrylated resins commercially available under product number AAS82059B from Advanced Adhesive Systems of Newington, CT.

Additives, such as nanostructured chemicals, such as polyhedral oligomeric silsesquioxanes (POSS), can be added to the urethane material to enhance the physical properties of the sealant. One such POSS material is commercially available from Hybrid Plastics Inc. of Hattiesburg, MS, product grade MA0735.

In embodiments, a formulation of about 90-97 weight percent acrylated urethane and about 3-10 weight percent nanostructured additive has been found to form a suitable formulation for application to a fastener. In embodiments, the urethane may be present at about 95 weight percent and the nanostructured additive may be present at about 5 weight percent of the sealant. In embodiments, additional additives such as pigments, e.g., black pigments, flow improvers and anti-counterfeiting agents may be added to the formulation in relatively small amounts. A curing agent is present in the material, such as a photoinitiator suitable for curing the material by exposing the material applied to the fastener to UV or LED light. A flow improver may or may not be necessary if the viscosity of the sealing material is such that the sealing material flows appropriately and as desired, depending on the size of the fastener, the material coating thickness, and the desired wicking characteristics. It will be understood that any additives used should not be of a type that will interfere with the UV or LED curing step.

As in the formulations disclosed above, it has been found that such formulations advantageously provide a low viscosity liquid material that better lends itself to high speed application with fewer rejects. Such materials have low viscosities, for example, from about 500 to about 2000 centipoise (cP), and as low as about 1300 cP, allowing for high speed application to fasteners. The viscosity of such materials is only slightly more viscous than water.

Also, such materials can be cured in a relatively short time without the use of heat. Indeed, the materials can be cured using an ultraviolet light source (at the appropriate wavelength of ultraviolet light) or an LED light source, as desired and based on the type of photoinitiator used. It has been found that the materials can be cured on the fastener in about 2-20 seconds, preferably about 2-10 seconds, and even more preferably about 2-5 seconds, without the use of heat. Unlike known sealing materials that require application to a heated fastener or heating after application to the fastener, the materials of the present invention cure in about 2-20 seconds, 2-10 seconds, or 2-5 seconds at temperatures below about 66° C. (about 151° F.), preferably at about room temperature of 25° C. (about 77° F.). Thus, curing can be performed without the need for induction or other types of heating.

The liquid applied sealing material of the present invention, due to its low viscosity, when applied to a fastener, such as the underside (e.g., seat) of the head of the fastener, can be formulated to flow easily around the entire underside of the head and wick along the portion of the thread or shank adjacent to the head to form a cone-like shape, thus providing a completely wetted surface ready for curing. It will be appreciated that the material can be formulated, for example with a flow additive, to make it slightly less flowable and not wick to the seat. Such a formulation can be advantageous during application, such as when the fastener thread extends completely to the underside of the head or seat. It can be seen that the sealant has been applied and the fastener after five installations and removals shows no cracking or delamination of the sealant.

Additionally, the material is free of solvents, halogens, polyvinyl chloride (PVC), REACH SVHCs, phthalates, bisphenol A (BPA) and is RoHS compliant. In addition, the sealant is free of sulfur-containing compounds, plasticizers and outgassing materials.

It has been found that fasteners having the sealing material of the present invention have excellent waterproofing performance and that the cured material has very good adhesion to metal. It has also been found that fasteners having the sealing material of the present invention exhibit excellent adhesion to steel and better durability to multiple installations, i.e., the fasteners can be installed and removed multiple times and the material remains in place with a high degree of integrity such that the sealing properties of the fastener to which the material is applied are maintained. It has also been observed that the sealing material of the present invention exhibits good water resistance and high temperature resistance, e.g., heat resistance up to at least about 85°C (185°F).

Tests were conducted to determine the effectiveness of a sealant having a nanostructured chemical, such as a polyhedral oligomeric silsesquioxane (POSS) additive. The sealant was formulated with about 95 percent by weight of acrylated urethane and about 5 percent by weight of the nanostructured additive.

In the first set of tests, referring to Figures 9 and 10 , two sets of 30 samples were tested. The first set of samples had only a polyurethane coating (baseline or control). The second set of samples had polyurethane (95 wt%) and a nanostructured chemical (PU/POSS) (5 wt%) sealant applied thereto. At 185°F (85°C), all of the samples passed the seal test. None of the samples showed cracks.

At 203°F (95°C), 25 of the reference samples passed the seal test (5 failed). All of the PU/POSS samples passed the seal test. 9 of the reference samples showed cracks. None of the PU/POSS samples showed cracks. At 221°F (105°C), 16 of the reference samples passed the seal test (14 failed). 20 of the PU/POSS samples passed the seal test (10 failed). 16 of the reference samples showed cracks. 8 of the PU/POSS samples showed cracks.

Fasteners with the control sealant and PU/POSS sealant were also tested for surface delamination by threading the fastener into a mating opening after 30 minutes of exposure to 185°F (85°C). Twenty of each of the control and PU/POSS sealant applied fasteners were tested. Of the 20 control fasteners tested, 13 showed partial removal or delamination at the seating surface, while none of the PU/POSS coated fasteners showed partial removal or delamination.

It is envisioned that the sealant of the present invention is used in a fastener to seal the assembly . The fastener with the sealant was tested in an environment to simulate the fastening of parts of a tail light assembly (to fasten two parts of the tail light assembly together in a two-piece system). The fastener was coated with the above-mentioned sealant and cured using a UV light for 25 seconds. The UV light used was relatively low intensity. It is envisioned that a higher intensity UV light source will be used in production.

In another set of tests similar to the submersion tests described above, a test device was constructed that included a submerged test structure or tank and a submerged test chamber . In the test device, a steel plate was secured to a steel chamber (two-article system) by five M3.0 fasteners coated with a sealing material. Tests were performed in accordance with General Motors Worldwide procedure GMW14906 4.5.4.3, Pressure Seal Test. In each test, the sealed chamber was submerged in water to a depth of 1 inch (2.5 cm) in a submersion test tank. The interior of the chamber was pressurized to a pressure of 1 psig (7 kPa) for 5 minutes. Fifty samples of fasteners with POSS formulated sealant were tested. All passed with no leaks. The pressure was increased to 10 psig (68.9 kPa). All samples passed with no leaks. The pressure of 10 psig was 10 times the pressure required.

In the same test device, 50 samples were tested under vacuum. Testing was performed in accordance with General Motors Worldwide Procedure GMW14906 4.5.4.1, Vacuum Seal Test. A vacuum was drawn on the chamber while it was submerged in water for 15 seconds. A vacuum of 3 psi (-21.0 kPa) was drawn on the chamber. All of the samples passed the vacuum test. The vacuum was increased to 5 psi (-33.9 kPa). All of the samples also passed the increased vacuum.

Another set of tests under pressure and vacuum were performed after the samples were thermally cycled. This was called the Storage Test and was performed in accordance with General Motors Worldwide Procedure GMW 14906 4.9.2.12, Storage Test. Under this test regime, the samples were tested both before and after the thermal cycle. The samples were first heated to a temperature of 176°F (80°C) +/- 5.4°F (+/- 3°C) for 48 hours, then returned to an ambient temperature of 73°F (23°C) +/- 9°F (+/- 5°C) over a period of more than 15 minutes, and then cooled to a temperature of -40°F (-40°C) +/- 5.4°F (+/- 3°C) for 24 hours. The samples were then returned to an ambient temperature of 73°F (23°C) +/- 9°F (+/- 5°C) over a period of more than 15 minutes. Pressure and vacuum tests were performed. All samples passed the pressure and vacuum tests.

Subsequent testing was performed to test for rejects under pressure in accordance with General Motors Worldwide Procedure GMW 14906 4.0.2.8.8.3. On the same test device, the pressure in the device was increased to 0.25 psig (1.75 kPa) for one minute. The pressure in the device was then increased in increments of .25 psig (1.72 kPa) below 1.52 psig (10.5 kPa) and .5 psi (3.5 kPa) above 1.52 psig (10.5 kPa), with each increment held for one minute until a reject occurred. The pressure was increased to 10 psig (68.9 kPa). The test was then terminated due to safety concerns. The 10 psig pressure was 10 times the required pressure. No samples failed prior to the end of the test.

Pressure and vacuum testing was also performed after the rapid temperature transition in accordance with GMW 14906 4.8.2.1.9.2, Rapid Temperature Transition. The samples were thermal cycled five times from 185°F (85°C) to -76°F (-60°C) for a period of approximately 6 hours and 30 minutes . The samples were then tested. All of the samples passed the pressure and vacuum test.

In another set of tests, the samples were submersion tested according to Fiat Chrysler Automobiles (FCA) procedure FCA PF. 90078 5.2.1, Sealing Condition Submersion Test. In these tests, a sealed chamber was immersed in water in a submersion test tank. The interior of the chamber was pressurized to a pressure of .75 psig (5.2 kPa) for 60 seconds at room temperature. All of the samples passed with no leaks.

The samples were then tested according to FCA PF.90078 5.15, Shipping/Storage Temperature Test. The samples were thermally cycled and then tested with the water immersion test described above. The samples were cooled to -40°F (-40°C) for approximately 24 hours, brought to approximately room temperature 68°F (20°C) for two hours, then heated to a temperature of 185°F (85°C) for 24 hours, then returned to room temperature 68°F (20°C). Following cycling, the samples were subjected to a water immersion test . All of the samples passed with no leaks.

Samples were tested according to FCA PF. 90078 5.22, Sealant Pressure Test to Failure. The chamber was initially heated to a pressure of .75 psig (5.2 kPa) with pressure increases of .25 psig (1.72 kPa) and held for 15 seconds before failure. The test was terminated at 10 psig (68.9 kPa). No samples failed. The 10 psig pressure was 10 times the required pressure.

Other advantages of the POSS formulated acrylated urethane sealant of the present invention have also been identified. For example, the sealant is harder than known sealant materials, having a hardness of about 55-60 Shore D compared to known sealants having a hardness of about 30-70 Shore A. For reference purposes, a hardness of 55-60 Shore D is approximately equal to a hardness of 100 Shore A. The increased hardness provides improved toughness and tear resistance.

Additionally, the sealant showed no signs of cracking or delamination after the GMW and FCA tests described above. Additionally, fasteners with sealant were exposed to a variety of chemicals commonly found in the vehicle and automotive industries, including 50% methanol in water, antifreeze and coolants, wheel cleaners, automatic transmission fluids, car wash shampoos, automotive glass cleaners, paint cleaners, oil cleaners, bug and tar removers, diesel fuel, ice spray wax and lubricants. The fasteners with sealant were exposed to these chemicals for 24 hours. They were then visually inspected and showed no signs of deterioration, delamination or cracking.

As mentioned above, when a sealant is applied to a fastener, it tends to wick under the head of the fastener, along the shank or top threads of the fastener, forming a cone-like shape. Thus, when tightened against a mating part/surface, a seal occurs along a circumferential line rather than across the entire mating part. This concentrates the force exerted by the mating threads. This is in contrast to flat elastomeric washers (e.g., those that act as gaskets), which compress along the entire part. As a result, more force or a softer material is required to compress the material and form a seal.

Other benefits of the POSS formulated sealants of the present invention include repeated installation and removal (5 times) without degradation or damage to the sealing material or the seal formed, or delamination of the sealing material or the seal formed. Fasteners do not need to be refastened after the article in which they are installed is annealed. For example, some tail light assemblies require annealing (at about 80°F or 27°C) to reduce stresses in the plastic after assembly. Known sealants that include polymer (EPDM) washers tend to loosen after tightening and annealing. On the other hand, the POSS formulated sealants of the present invention do not loosen after tightening and annealing. The sealants of the present invention also exhibited limited or no compression set after installation.

The material of the present invention is less prone to tearing, provides a better sealing geometry (e.g., sealing against a cone rather than against the flats of a cylinder), and has a shorter leak path compared to flat washers in that the sealant of the present invention adheres to the fastener and wicks into the shank and threads near the underside of the fastener head, whereas flat washers have a leak path indicated by L due to their loose fit on the fastener.

The use of the material of the present invention does not result in outgassing because no peroxides or sulfur containing materials are used. Additionally, there are no phthalates or other chemicals that can leach out of the sealant. Thus, the sealant of the present invention will not cause the plastic to crack or crack to which it is clamped. Also, the material of the present invention is easy to handle and use because it is applied as a solution.

Furthermore, because of its high adhesion to steel fasteners and hardness comparable to Nylon 11 (here used as a mechanical locking mechanism/material for the fastener, see e.g., FIG. 8), the sealing material of the present invention serves multiple functions. Thus, in addition to use as a sealing material, it can also function to lock a fastener in place without the need for secondary processing, for example, to apply a locking patch (e.g., a Nylon 11 patch), thereby providing additional productivity gains and reducing the complexity and steps required in manufacturing. In such applications, the sealant can be applied to threads to function as a thread locking material, with or without use as an underhead sealant.

A method of making a fastener having a sealing material applied thereto includes applying a liquid applied acrylate material to the fastener and curing the liquid applied acrylate material using a UV or LED light source and without the use of heat. The method may include pre-treating the fastener with a plasma treatment. The liquid applied acrylate material may be any of the materials described above, including suitable photoinitiators, nanostructured materials, such as polyhedral oligomeric silsesquioxanes (POSS), other additives such as pigments present in amounts that do not interfere with the curing of the material, flow improvers, and heat resistant additives. A superhydrophobic material may also be included as an additive.

In this disclosure, the terms "a" or "an" are to be construed as including both the singular and the plural. Conversely, any reference to plural items includes the singular, where appropriate. All percentages are by weight unless otherwise noted.

All patents and published applications referenced herein are incorporated by reference in their entirety, whether or not specifically referenced in the text of this disclosure.

Those skilled in the art will also recognize that relative directional terminology, such as side, above, below, top, bottom, rear, front, etc., is for descriptive purposes only and is not intended to limit the scope of the present disclosure.

From the foregoing, it will be observed that many modifications and variations may be effected without departing from the true spirit and scope of the novel concepts of the present disclosure. It is to be understood that no limitation to the specific embodiments illustrated is intended or should be inferred. The present disclosure is intended to cover, by the appended claims, all such modifications as fall within the scope of the claims.

Claims (16)

1. A system comprising: a first article and a second article joined by a fastener having a sealing material on an underside of a head of the fastener and on a shank or threads adjacent to the underside of the head;
the sealing material is formed into a cone-like shape at the transition from the shank or thread to the underside of the head;
the sealing material comprising an acrylate material present in a concentration of about 90 to about 97 weight percent of the sealing material; and a nanostructured material present in a concentration of about 3 to about 10 weight percent of the sealing material;
the sealing material is cured using UV or LED light prior to joining the first and second articles ;
whereby the fastener joining the first article and the second article is capable of exhibiting no defects when tested in accordance with General Motors Worldwide Procedure GMW 14906 4.5.4.3, Pressure Seal Test, and is capable of exhibiting no defects when the test pressure is increased to 10 psig. The system of claim 1 , wherein the acrylate material is present in a concentration of about 95 percent by weight of the sealing material, and the nanostructured material is present in a concentration of about 5 percent by weight of the sealing material. The system of claim 1 , wherein the sealing material, when cured, has a hardness of about 55-60 Shore D. Further comprising a group of fasteners,
2. The system of claim 1, wherein each fastener in the group of fasteners joining the system is capable of showing no defects when tested in accordance with General Motors Worldwide Procedure GMW 14906 4.5.4.3, Pressure Seal Test, and is capable of showing no defects when the test pressure is increased to 10 psig. The system of claim 1 , wherein the acrylate material is a urethane acrylate. The system of claim 1 , wherein the acrylate material is one or a combination of acrylated urethane and acrylated polyester. The system of claim 1 , wherein the nanostructured material is polyhedral oligomeric silsesquioxane (POSS). 8. The system of claim 7, wherein the POSS is present in a concentration of about 5 percent by weight of the sealing material. 1. A system comprising : a first article and a second article joined by a fastener having a sealing material on an underside of a head of the fastener and on a shank or threads adjacent to the underside of the head;
the sealing material is formed into a cone-like shape at the transition from the shank or thread to the underside of the head;
the sealing material comprising an acrylate material present in a concentration of about 90 to about 97 weight percent of the sealing material; and a nanostructured material present in a concentration of about 3 to about 10 weight percent of the sealing material;
whereby the sealing material is cured using UV or LED light before the fastener joins the first and second articles ;
the fastener joining the first article and the second article is capable of exhibiting no defects when tested in accordance with General Motors Worldwide Procedure GMW 14906 4.5.4.1, Vacuum Seal Test; and the fastener is capable of exhibiting no defects when the vacuum is raised to 5 psi. 10. The system of claim 9, wherein the acrylate material is present in a concentration of about 95 weight percent of the sealing material; and the nanostructured material is present in a concentration of about 5 weight percent of the sealing material. the sealing material is applied to the threads adjacent the underside of the head;
The system of claim 9 , wherein the sealing material provides a thread lock. Further comprising a group of fasteners,
10. The system of claim 9, wherein each fastener in the group of fasteners joining the system is capable of exhibiting no defects when tested in accordance with General Motors Worldwide Procedure GMW 14906 4.5.4.1, Vacuum Seal Test, and is capable of exhibiting no defects when the vacuum is raised to 5 psi. The system of claim 9 , wherein the acrylate material is a urethane acrylate. The system of claim 9 , wherein the acrylate material is one or a combination of acrylated urethane and acrylated polyester. 10. The system of claim 9, wherein the nanostructured material is polyhedral oligomeric silsesquioxane (POSS). 16. The system of claim 15, wherein the POSS is present in a concentration of about 5 percent by weight of the sealing material.

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