Reactivation of co-cured film layers

Abstract

To provide a method for reactivating a co-cured film layer disposed on a composite structure.SOLUTION: A method includes: applying a reactivation treatment composition comprising at least two solvents and a surface exchange agent comprising a metal alkoxide or chelate thereof to a co-cured film layer (2); and allowing the reactivation treatment composition to form a reactivated co-cured film layer (2). The co-cured film layer (2) is previously cured at a curing temperature higher than about 50°C. The reactivated co-cured film layer (2) and an aircraft part (1) having the reactivated co-cured film layer (2) are also provided.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a method for reactivating a previously co-cured film layer on a composite structure, which allows for the application of a topcoat or additional paint layers to the film layer without the need for an intermediate step such as sanding. The resulting co-cured film layer on the composite structure provides good adhesion to both the composite structure and additional coating layers, as well as protection against exposure to environmental conditions and elements, including UV light, rain erosion, moisture, and / or chemicals such as fuels. The disclosed method for reactivating a previously co-cured film layer on a composite structure is particularly useful in the fabrication of aerospace components, such as aircraft parts. [Background technology]

[0002] For example, vehicle components, aerospace (e.g., aircraft) components, and many other components are made using high strength, lightweight composite materials to reduce the overall weight of the structure, e.g., aircraft, etc. Many such composite materials are reinforced with carbon fibers dispersed in a polymer matrix.

[0003] Commercial aircraft and vehicle manufacturers often desire to mark or inscribe some information or marking (e.g., model number, company name, company logo, or decorative or informational markings including words, numbers, letters, designs, etc.) on the aircraft and vehicles they manufacture. However, it has been found that providing such markings to parts made of composite materials is difficult. Painting or printing on composite structures often increases manufacturing process times, including flow times for painting, thereby increasing the cost and time required to manufacture the parts. Additionally, some parts include shapes that are difficult to print on, such as complex three-dimensional curved surfaces.

[0004] In addition, it is often difficult to maintain desirable flow characteristics on coated or painted aircraft surfaces, such as aircraft wings or tails, and there are standards for acceptable paint edges and paint waviness to avoid affecting desirable boundary layer characteristics during flight. There are also regulations for three-dimensional surface discontinuities that can occur due to the inclusion of debris, dust, dry coating overspray, and the like, and due to the application of multiple paint layers to paint designs or lettering in multiple colors.

[0005] Prior art methods and systems for applying airline design to the exterior surface of an aircraft include, for example, a technique for laminating a coating or paint layer onto a primer layer or base color layer using tape and / or masking. Such prior art methods and systems for applying airline design to the exterior surface of an aircraft have difficulty in meeting and maintaining aerodynamic performance requirements for promoting proper aerodynamic performance, such as the aerodynamic performance requirements required for edge angles and edge apexes in the coating or paint.

[0006] Therefore, a marking process is employed that can provide suitable coloring and design, as well as a smooth aerodynamic surface, while reducing processing time and / or cost. Such a marking process can be, for example, using a co-curable film, as disclosed in U.S. Patent Application Publication No. 2018 / 0345646, which is incorporated herein by reference. However, even with a co-curable film, various types of manufacturing processes remain difficult. For example, adding a coating layer to the surface of a co-cured film layer previously cured on a composite structure usually does not provide adequate adhesion. Therefore, in a conventional process, a process is performed to sand and reactivate the surface of the co-cured film layer in order to add an additional coating layer to the co-cured film. This allows for the addition of a paint layer or topcoat. However, manual sanding is labor intensive, raises ergonomic concerns, generates abrasive debris, uses sanding consumables, and increases time in the factory. Thus, existing methods for treating a co-cured surface to prepare it for application of an additional coating layer may lack economic and manufacturing efficiency.

[0007] Therefore, there is a need to develop a surface treatment technique for the co-cured film layer that will increase adhesion of additional layers to the co-cured film layer while minimizing economic viability, health, and safety issues. Summary of the Invention

[0008] In one aspect, the present disclosure relates to a method for reactivating a co-cured film layer on a composite structure, the method comprising applying a reactivation treatment to the co-cured film layer, the reactivation treatment comprising at least two solvents and a surface exchange agent comprising a metal alkoxide or a chelate thereof, and applying the reactivation treatment to form a reactivated co-cured film layer, the co-cured film layer having been previously cured on the composite structure at a cure temperature above about 50° C., e.g., at least about 121° C., or in an autoclave.

[0009] In certain embodiments, the method further comprises applying an additional coating layer, such as a clearcoat, to the co-cured film layer. In certain embodiments, the method does not comprise sanding the co-cured film layer prior to applying the reactivation treatment. In certain embodiments of the methods of the present disclosure, the co-cured film layer, when cured, comprises a polyurethane, a polyimide, a polyester, or an epoxy, and in certain embodiments, the co-cured film layer, when cured, comprises a polyurethane.

[0010] In various embodiments of the present disclosure, the surface exchange agent is zirconium propoxide, and in certain embodiments, the at least two solvents are dipropylene glycol dimethyl ether and n-propanol.

[0011] In certain embodiments, the methods of the present disclosure further comprise applying a cleaning solvent prior to or simultaneously with applying the reactivation treatment.

[0012] In certain embodiments, the method of the present disclosure further comprises applying an additional coating layer, wherein the additional coating layer has an intercoat adhesion level in the range of 6 to 10, for example, in the range of 8 to 10, after a rain erosion test.

[0013] In another aspect, the present disclosure relates to a reactivated co-cured film layer comprising a co-cured film layer disposed on a composite structure and a reactivation treatment layer comprising a surface exchange agent comprising a metal alkoxide or a chelate thereof disposed on the co-cured film layer to form a reactivated co-cured film layer, the co-cured film layer having been previously cured on the composite structure at a cure temperature of at least about 50° C., e.g., at least about 121° C., or in an autoclave.

[0014] In a specific aspect of the reactivated co-cured film layer of the present disclosure, the co-cured film layer is not sanded. In a specific embodiment, the reactivated co-cured film layer further comprises an additional coating layer disposed on the reactivation treatment layer, and in a specific embodiment, the additional coating layer has an intercoat adhesion level in the range of 6 to 10, for example, in the range of 8 to 10, after a rain erosion test.

[0015] In certain embodiments of the reactivated co-cured film layer, the surface exchange agent is zirconium propoxide, and in certain embodiments, the co-cured film layer, when cured, comprises a polyurethane, a polyimide, a polyester, or an epoxy.

[0016] In yet another embodiment, the present disclosure relates to an aircraft part having a cured film layer disposed thereon, the aircraft part comprising a composite structure and a film layer cured on a surface of the composite structure, the co-cured film layer being reactivated according to an embodiment of the present disclosure. [Brief description of the drawings]

[0017] [Figure 1]1 is a schematic diagram of a panel portion of a composite structure having a co-cured film layer disposed thereon that has been treated to reactivate surface properties to promote adhesion of additional coating layers to the co-cured film layer without compromising its integrity; [Diagram 2] FIG. 1 is a visual representation of a scale from 1 to 10 corresponding to maximum tear length and percent peeled area from a rain erosion test. [Figure 3A] FIG. 1 shows rain erosion testing of three composite structures coated with a co-cured film layer and an additional coating layer that was not exposed to ultraviolet (UV) light but was sanded prior to the addition of the coating layer. [Figure 3B] FIG. 1 shows rain erosion testing of three composite structures coated with a co-cured film layer and an additional coating layer that was exposed to 200 kJ / m2 UV light and sanded prior to the addition of the coating layer. [Figure 3C] FIG. 1 shows rain erosion testing of three composite structures coated with a co-cured film layer and an additional coating layer that was exposed to 1,000 kJ / m2 UV light and sanded prior to the addition of the coating layer. [Figure 4A] Figure 1 shows rain erosion testing of three composite structures coated with additional coating layers over a co-cured film layer that was not sanded or exposed to UV light and was treated with the reactivation treatment Sur-Prep® AP-1 prior to the addition of the coating layer. [Figure 4B] Figure 1 shows rain erosion testing of three composite structures coated with a co-cured film layer and an additional coating layer that was exposed to 200 kJ / m2 UV light and then treated with the reactivation treatment Sur-Prep® AP-1 prior to the addition of the coating layer. [Figure 4C] Figure 1 shows rain erosion testing of three composite structures coated with a co-cured film layer and an additional coating layer that was exposed to 1,000 kJ / m2 UV light and then treated with the reactivation treatment Sur-Prep® AP-1 prior to the addition of the coating layer. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] In the accompanying drawings, some details have been simplified without strictly maintaining structural accuracy, detail, and scale, with a priority given to facilitating understanding of the teachings of the present disclosure.

[0019] The following description is merely exemplary in nature and is in no way intended to limit the disclosure or its application or uses.

[0020] Throughout this specification, numerical ranges are used as shorthand for indicating all values ​​within the range. Any value within the range may be selected as the end value of the range. In addition, all references cited herein are incorporated herein by reference in their entirety. In the event of a conflict between the definitions of this disclosure and those of the references, the definitions of this application shall prevail. Unless otherwise stated, percentages and amounts given herein shall be understood to be weight percentages. The amounts given are based on the weight of the active material.

[0021] The methods disclosed herein allow for the reactivation of a film layer that has already been co-cured to a substrate, or to an intermediate layer applied to a substrate, thereby improving the adhesive properties for additional coating layers without compromising the integrity of the coating.

[0022] When a new coating layer is added to a co-cured film layer, a step of mechanically polishing (e.g., sanding) or abrading (e.g., by laser) is typically required to remove the rough surface, thereby preparing the co-cured film layer for application of the additional coating layer. The method provided in the present disclosure advantageously eliminates the need for conventional mechanical polishing of the co-cured film layer before applying coatings and / or other elements to the co-cured film layer. For example, the reactivation method of the present disclosure can reactivate the surface of the co-cured film layer to improve adhesion properties to additional coatings and / or other elements.

[0023] It is well known that when a new coating layer is applied to an autoclave cured or aged film layer, the adhesion of the coating layer may not meet the aircraft operational performance requirements because the cured or aged co-curable film layer has already passed the application window for proper adhesion to the new coating layer. For example, for a co-curable film layer containing polyurethane, the curing process crosslinks the polymer units to form rigidity in the cured polyurethane film layer. The amount of crosslinking is proportional to the curing time and / or temperature of the polyurethane film. Thus, a co-curable film layer cured in an autoclave (e.g., at a temperature of at least about 121° C.) is expected to have a significantly higher crosslink density than a comparable film layer cured by other means, such as at a lower temperature (e.g., at ambient temperature or below 50° C.). Furthermore, the higher the crosslink density in the co-cured film layer, the worse the adhesion of additional coating layers is expected to be.

[0024] In contrast, the present disclosure provides a method for reactivating a co-cured film layer that has already been cured at high temperature, such as in an autoclave. The method includes applying a surface reactivation treatment composition that includes a solvent and a surface reactivation agent. The method of the present disclosure does not require an additional step of sanding the co-cured film layer. It is an unexpected and surprising effect that the application of the reactivation treatment composition can effectively reactivate a film layer that has been cured at high temperature and has a high crosslink density, without the need for a sanding step.

[0025] The term "reactivation" as used herein refers to improving the adhesive properties of a coating layer, such as a co-cured film layer. In this specification, activation and reactivation are used interchangeably. The adhesive properties can be measured by any means known in the art, for example, as a coating's intercoat adhesion level. As used herein, "intercoat adhesion level" refers to the level of adhesion between two coatings, for example, between a co-cured film layer and an additional paint layer placed directly on the co-cured film layer. In this disclosure, the intercoat adhesion level is quantified on a scale of 1 to 10, for example, based on the tear length and peeling degree of the additional paint layer after rain erosion testing.

[0026] In certain aspects, the methods of the present disclosure include applying to the co-cured film layer a surface reactivation treatment comprising a solvent, a surface exchange agent, and optional additives, the surface exchange agent being selected from a metal alkoxide or a chelate thereof, such as a titanium or zirconium alkoxide or a chelate thereof.

[0027] In certain embodiments, the present disclosure discloses a method of promoting adhesion of an additional coating layer to a co-cured film layer disposed on a substrate, the method comprising applying to the co-cured film layer a reactivation treatment comprising a solvent, a surface exchange agent, and optional additives, wherein the surface exchange agent is selected from a metal alkoxide or a chelate thereof, such as a titanium alkoxide or a zirconium alkoxide, or a chelate thereof.

[0028] The methods of the present disclosure can improve adhesion properties to additional coating layers without the need to subject the co-cured film layer to steps such as mechanical abrasion or chemical stripping.

[0029] As shown in FIG. 1, reactivating the adhesion of a previously cured film layer (2) to a rigid substrate (1), such as a composite aircraft part, to form an effective adhesive bond (5) to a new coating layer (4) to be placed on the cured film layer (2) requires not only reactivating the adhesion of the cured film layer (2) to the new coating layer (4), but also not affecting the adhesive bond (3) previously formed between the substrate (1) and the cured film layer (2), and not affecting the integrity of the exposed (uncoated) surface (6) of the substrate. <Composite structure>

[0030] In the method of the present disclosure, at least one co-cured film layer is applied to a substrate, the co-cured film layer having been previously cured to the substrate or intermediate layer, for example, in an autoclave, at a temperature greater than 50° C. The substrate is a support structure, such as a panel configured as part of a support structure of a building, vehicle, or aircraft. For example, the substrate is a panel portion of an aircraft body or wing. In one embodiment, the substrate comprises or consists essentially of a composite material.

[0031] The composite material may be, for example, a carbon fiber reinforced epoxy material or a glass fiber reinforced epoxy material. The composite material may include glass, wood, or fabric. The substrate may be a substantially non-elastic or rigid plastic and may include polyimide or polycarbonate. In one aspect, the substantially non-elastic or rigid plastic does not include plastic films or plastic packaging materials that are stretchable or easily processed and / or that do not provide structural rigidity or are not capable of elastic deformation.

[0032] In some embodiments, the composite structure is formed from an organic matrix and fibers, such as epoxy resin and carbon fiber reinforced polymer (CFRP). In some embodiments, the composite structure is in the form of a prepreg. As used herein, the term "prepreg" refers to one or more sheets or layers of fibers impregnated with a matrix material. The matrix material may be included in a semi-cured state, for example, to provide a desired adhesive or cohesive property.

[0033] In some embodiments, the prepreg layers are disposed adjacent to one another. In certain embodiments, the prepreg layers may be laid up in a predetermined orientation relative to one another. For example, a prepreg layup may include prepreg layers of unidirectional fibers stacked at fiber orientations of 0°, 90°, any angle θ, and combinations thereof relative to the largest dimension, e.g., length, of the layup. It will be appreciated that in certain embodiments, a prepreg layup may include a combination of prepregs of any fiber configuration, e.g., unidirectional and multidirectional fibers.

[0034] In some embodiments, a composite structure is formed of one or more sandwich panels (e.g., honeycomb panels), one or more of which may be composite panels. Each sandwich panel generally comprises a core of a relatively lightweight material sandwiched between two panel skins. A composite structure may include one or more coatings or layers applied to an underlying panel or layer of material. A composite structure may include one or more sandwich panels, joints formed between two or more sandwich panels, and / or three-dimensional structures constructed using one or more sandwich panels.

[0035] As shown, in non-limiting examples, the composite structures are used in aircraft structures such as aircraft wings, fuselages, horizontal stabilizers, vertical stabilizers, and engine housings, although other aircraft components may additionally or alternatively include composite structures such as sandwich panels and / or joints formed between two or more sandwich panels. Other applications of composite structures in aircraft include overhead bins, floor panels, interior walls, galleys, control surfaces, passenger baggage bins, thrust deflectors, capsule panels, ablative shields for nose cones, instrument bins and shelves, and bulkhead panels. Composite structures used in other industries include space satellite or aerospace vehicle parts, transport aircraft, shipping containers, shelters, large antennas or reflectors, refrigeration panels, floor panels for high-speed transport aircraft, electronic decks and shelters for ships, cargo pallets, automobile bodies, boats and other seagoing vessels, architectural curtain walls, partitions, dividing panels, extendable hospital shelters, and / or interior structures in assemblies.

[0036] The composite structures and co-curable film layers of the present disclosure, in some embodiments, are placed together in a mold and co-cured, and in certain embodiments, this co-curing can integrate the co-curable film layers into a composite material. <Co-cured film layer>

[0037] As mentioned above, the co-cured film layer has already been cured onto the surface of a substrate, such as a composite structure or an intermediate layer between a composite structure and the co-cured film layer, and as a result of the curing, it has acquired a poor adhesive bond to other elements, such as additional coating layers. The surface properties of the co-cured film layer may be less reactive than would be expected based on the chemical properties of the individual components and the curing conditions. Without wishing to be bound by theory, this phenomenon is believed to be due to the fact that as the crosslink density increases as a function of curing time, curing temperature, and / or aging, the energy and amount of reactive functional groups on the film surface decreases, which results in less chemical interaction and / or formation of strong adhesive bonds with other elements.

[0038] The co-cured film layers that can be reactivated by the method of the present disclosure include, but are not limited to, fully or partially crosslinked film layers. In some embodiments, the co-cured film layers of the present disclosure are formed from a co-curable film composition that includes a thermosetting resin. Thermosetting resins generally include prepolymers that are soft solid or viscous liquid at room temperature (about 20° C. to about 25° C.) and typically become hard when cured.

[0039] "Cure" includes chemical reactions in which crosslinking occurs among the polymer chains in a curable material, such as a co-curable film composition, to produce an insoluble polymer network. Curing can be accomplished, for example, by processes including exposure to heat and / or ultraviolet light. In some embodiments, curing can be accelerated by high pressure and / or by the incorporation of a curing agent or catalyst. As used herein, the term "cured" refers to subjecting a polymerizable composition to curing conditions, thereby reacting at least a majority of the reactive groups in the composition to form a solid polymer. As will be appreciated by those skilled in the art, subjecting a polymerizable composition to curing conditions, such as an autoclave, will result in a cured composition in which more reactive groups have reacted, and therefore a greater degree of cure than the same polymerizable composition that has not been subjected to curing conditions or that has been cured less, such as by lowering the curing temperature, e.g., ambient temperatures, e.g., about 20°C to about 25°C, or by shortening the curing time.

[0040] In some embodiments, curing comprises baking the one or more co-curable film layers and the composite structure together at a temperature greater than about 50° C., such as from about 65° C. to about 200° C., or from about 121° C. to about 185° C. In some embodiments, curing comprises baking the one or more co-curable film layers and the composite structure together for a period of less than 48 hours, such as from less than 24 hours, or from about 2 hours to about 12 hours.

[0041] In some embodiments, the co-curing can be carried out using an autoclave, oven cure, or out-of-the-autoclave curing. As used herein, "out-of-the-autoclave" refers to a process that includes enclosing a layup of prepregs, including, for example, the co-curable film layers of the present disclosure, in a closed mold. Vacuum, pressure, and heat are then applied using conventional techniques other than an autoclave, such as a resin transfer molding press. In certain other embodiments, the co-curing is carried out using an autoclave at a temperature of at least 121°C.

[0042] Examples of suitable thermosetting resins for use in the co-curable film composition of the present disclosure include polyester resins, epoxy resins, and polyimide resins, such as, for example, bismaleimide (BMI) and / or polyetherimide. In certain embodiments, examples of suitable thermosetting resins for use in the co-curable film composition of the present disclosure include at least one polyisocyanate and at least one polyol that form a polyurethane upon curing. As used herein, the term "polyurethane" refers to a polymer that contains urethane (carbamate) linkages, urea linkages, or a combination of both, such as, for example, polyurethaneureas. Thus, the polyurethanes of the present disclosure contain at least urethane linkages and may optionally contain urea linkages.

[0043] In some embodiments, the co-curable film composition of the present disclosure includes a thermosetting resin in an amount ranging from about 5 to about 100 weight percent (wt%), such as from about 15 to about 75 wt%, or from about 25 to about 60 wt%, based on the total weight of the co-curable film composition.

[0044] In some embodiments, the co-curable film compositions of the present disclosure further comprise non-conductive additives, such as, for example, fillers, flow control agents, toughening agents, stabilizers (e.g., antioxidants, thermal stabilizers, and ultraviolet (UV) stabilizers), curing agents, and / or catalysts.

[0045] Examples of suitable non-conductive fillers for use in the co-curable film compositions of the present disclosure include ground or precipitated chalks, ground quartz, alumina, dolomite, carbon fibers, glass fibers, polymeric fibers, titanium dioxide, fused silica, carbon black, calcium oxide, calcium magnesium carbonate, barytes, and silicate-like fillers, especially of the aluminum magnesium calcium silicate type. Other suitable non-conductive fillers include: Examples of fillers include ceramics and fumed silica. These fillers may be in the form of, for example, flakes, powders, fibers, microspheres, or glass balloons, and may be solid or hollow structures. A more detailed description of fillers is provided, for example, in U.S. Patent No. 4,980,234, the entire contents of which are incorporated herein by reference.

[0046] In some embodiments, the filler content in the co-curable film composition of the present disclosure can be in the range of about 0 wt % to about 40 wt %, for example, in the range of about 5 wt % to about 30 wt %, based on the total weight of the co-curable film composition.

[0047] Flow control agents can be used to control the rheological properties of the co-curable film composition. Examples of suitable flow control agents include fumed silica and metal powders. The content of the flow control agent can be in the range of about 0 wt% to about 40 wt%, for example, in the range of about 0.1 wt% to about 10 wt%, based on the total weight of the composition.

[0048] In some embodiments, a toughening agent can be added to the co-curable film composition to adjust the stiffness and surface hardness of the cured film. In certain embodiments, the toughening agent can be polymeric or oligomeric, have a glass transition temperature less than about 20° C. (e.g., less than about 0° C., less than about −30° C., or less than about −50° C.), and / or contain functional groups, such as carboxylic acid groups, amino groups, and / or hydroxyl groups, that can react with other components of the co-curable film composition when cured by heating.

[0049] Examples of suitable toughening agents include elastomeric toughening agents, such as carboxylated nitriles (e.g., Nipol® 1472, Zeon Chemical, Inc.), carboxyl-terminated butadiene acrylonitrile (CTBN), carboxyl-terminated polybutadiene (CTB), poly(ether ether ketone) (PEEK), and polyether ketone ketone (PEKK). Other examples of suitable toughening agents are described, for example, in U.S. Pat. No. 4,980,234, U.S. Patent Application Publication No. 2008 / 0188609, and International Patent Publication No. WO2008 / 087467, each of which is incorporated herein by reference in its entirety. In certain embodiments, the concentration of the toughening agent may range from about 5 wt % to about 40 wt %, for example, between about 1 wt % and about 30 wt %, based on the total weight of the composition.

[0050] The co-curable film composition may include a UV stabilizer as an optional additive. In some embodiments, the UV stabilizer includes an ultraviolet light absorber, an antioxidant, a pigment, a blocking agent, and a filler. In some embodiments, the UV stabilizer includes butylated hydroxytoluene (BHT), 2-hydroxy-4-methoxybenzophenone (UV-9), 2,4-bis(2,4-dimethylphenyl)-6-(2-hydroxy-4-octyloxyphenyl)-1,3,5-triazine, 3,5-di-tert-butyl-4-hydroxybenzoic acid, n-hexadecyl ester, titanium dioxide, and carbon black. In some embodiments, the content of each UV stabilizer may range from about 0.1 wt% to about 5 wt%, for example, from about 0.5 wt% to about 3 wt%, based on the total weight of the composition.

[0051] Examples of suitable curing agents and / or catalysts that can be added to the co-curable film compositions of the present disclosure include aliphatic and aromatic primary amines, and aliphatic and aromatic tertiary amines. For example, amine-based curing agents and / or catalysts include dicyandiamide, bis-ureas (e.g., 2,4-toluene bis-(dimethylurea), 4,4′-methylene bis-(phenyl dimethylurea), and 4,4′-diaminodiphenyl sulfone (4,4-DDS). Other suitable curing agents and / or catalysts include boron trifluoride complexes, guanidines, and dicyandiamide. Other examples of suitable curing agents and / or catalysts are described, for example, in U.S. Pat. No. 4,980,234 and U.S. Patent Application Publication No. 2008 / 0188609, each of which is incorporated herein by reference in its entirety. In certain embodiments, the co-curable film composition of the present disclosure may include one or more curing agents and / or catalysts in an amount ranging from about 0.1 wt % to about 40 wt %, for example, from about 0.5 wt % to about 10 wt %, based on the total weight of the co-curable film composition.

[0052] Other suitable additives that may be included in the co-curable film composition include, for example, crosslinkers (e.g., aluminum or melamine crosslinkers), binders, corrosion inhibitors, plasticizers, and / or other additives conventionally known to one of ordinary skill in the art. In some embodiments, the co-curable film composition of the present disclosure may further include an electrically conductive material.

[0053] In some embodiments, the thickness of the co-cured film layer of the present disclosure when cured onto the surface of a composite structure ranges from about 1 mil to about 15 mils, such as from about 2 mils to about 10 mils, from about 3 mils to about 7 mils, or from about 3 mils to about 4 mils, where 1 mil is approximately equal to 25 microns.

[0054] The co-curable film layer of the present disclosure may further include at least one colorant, such as a pigment or dye, or may have a colored marking material printed thereon. In certain embodiments, at least one colored marking material is printed onto the co-curable film layer, and in certain embodiments, at least one colorant is mixed into the co-curable film composition. The at least one colorant is used to change the color and appearance of the co-curable film layer. The term "colorant" as used herein refers to any substance that imparts color to the co-curable film layer, a term that may include both colorants (known in the art) and pigments. Suitable colorants include, for example, titanium dioxide, carbon black, black pigments, and other colorants, including both inorganic and organic pigments. The colorant may be in the form of flakes, powders, fibers, or color concentrate liquids. Multiple colorants may be added to one co-curable film. In certain embodiments, the colorant is a solvent or water-based colorant. In certain embodiments, the colorant imparts special effects to the co-curable film layer, such as, for example, increasing reflectance, adding pearlescence, or providing luster.

[0055] It will be understood that the co-cured film layer being reactivated is a film layer that has been co-cured to a substrate, but that various coating layers may be present underneath the co-cured film layer, such as, for example, other decorative or co-cured film layers, primer layers, intermediate layers, and conversion or anti-corrosion coating layers. <Surface reactivation treatment agent>

[0056] The present disclosure discloses a surface reactivation treatment that can be applied to the surface of the co-cured film provided on the composite structure. The surface reactivation treatment of the present disclosure includes at least two solvents and a surface exchange agent, and may additionally include one or more additives as optional elements. According to the method of the present disclosure, the at least two solvents, the surface exchange agent, and the optional additives can be applied to the co-cured film layer in a mixed form as a reactivation treatment. The reactivation treatment of the present disclosure can take various physical forms, such as a solution, a suspension, a mixture, an aerosol, an emulsion, a paste, or a combination thereof. In one embodiment, the reactivation treatment takes the form of a solution, a suspension, or an aerosol.

[0057] The reactivation treatment agent can be prepared by mixing the various components by any mixing device known to those skilled in the art, such as, but not limited to, agitators, shakers, high-speed mixers, internal mixers, in-line mixers such as static mixers, extruders, mills, ultrasonic and gas dispersers, or by completely manual shaking. When the reactivation treatment agent is in the form of a solution, the solution may be prepared as a concentrate and diluted before use, or it may be prepared so that it can be used as it is.

[0058] In certain embodiments, the reactivation treatment may be prepared as a spray formulation. In certain embodiments, the reactivation treatment may be prepared in a state that can be applied to the co-cured film layer. It is understood that the components of such a formulation may be selected to provide a formulation with a particular rheology or viscosity suitable for use in a particular environment, such as a formulation for spraying or brushing. A spray formulation may be tailored for use with a particular spray gun and system (e.g., pressure, flow rate, nozzle diameter, etc.). The formulation may, for example, provide a wet film that dries to form a powder having a thickness of about 0 microns to about 15 microns, such as about 0.1 microns to about 5 microns, about 0.5 microns to about 2 microns, or about 0.1 microns to about 1 micron. The formulation may be applied to a surface of about 1 m. 2 / L ~ approx. 50m 2 / L coverage, e.g., about 15 m 2 / L ~ approx. 30m 2 / L coverage.

[0059] Solvent: The reactivation treatment agent of the present disclosure includes a solvent, which may be a single solvent or a combination of two or more solvents. In certain embodiments, the surface reactivation treatment agent includes at least two solvents. The at least two solvents can be selected from organic solvents suitable for industrial use. For example, the at least two solvents can be selected from esters, ketones, ethers, and alcohols, which can provide additional benefits to the reactivation treatment agent, such as, in some aspects, promoting disruption of the surface of the co-cured film layer disposed on the substrate, or providing an effective carrier for other components in the reactivation treatment agent, such as the surface exchange agent and / or any additional additives. In certain embodiments, the solvent can provide a liquid formulation that can be effectively applied to the surface of the co-cured film layer disposed on the substrate by spraying. In certain embodiments, the solvent can provide a liquid formulation that can be effectively applied to the surface of the co-cured film layer disposed on the substrate by, for example, brush painting. The solvent is a C 10 having one or more (e.g., 1 to 4) functional groups selected from hydroxyl, ether, ketone, and ester. 1-12 The organic solvent may be one or more organic solvents selected from the group consisting of alkyl, aryl ... 1-12 "Alkyl" refers to a straight or branched chain saturated hydrocarbon having 1 to 12 carbon atoms, which may be substituted and / or interrupted with one or more functional groups. In certain embodiments, the solvent is an interrupted and / or substituted C alkyl group as described above. 3-10 The organic solvent may be one or more selected from alkyl.

[0060] Suitable organic solvents or combinations of solvents may provide further benefits depending on the surface exchange agent and optional additives contained in the reactivation treatment agent, and include, but are not limited to, the following: (a) ketones, such as methyl ethyl ketone, methyl propyl ketone, methyl amyl ketone, methyl isoamyl ketone, methyl isobutyl ketone, acetylacetone, and acetone; (b) alcohols, i.e., aromatic alcohols, such as benzyl alcohol; 1-6 Or C 1-4 Alcohols, for example, aliphatic alcohols, such as tert-butanol, n-butanol, sec-butanol, isopropyl alcohol, n-propanol, ethanol, and methanol; cyclic alcohols, such as cyclohexanol; and glycols, such as ethylene glycol, polyethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, and polypropylene glycol; (c) ethers, i.e., glycol ethers, such as di-C of glycol, 1-6 Alkyl ether which glycol diethers include, for example, diethers of alkylene glycols such as ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, and polypropylene glycol, including, but not limited to, cyclic ethers such as diethylene glycol dimethyl ether, dipropylene glycol dimethyl ether, or the methyl butyl ether of diethylene glycol, and tetrahydrofuran; and (d) esters, for example, ethyl acetate, propyl acetate, isopropyl acetate, butyl acetate, isobutyl acetate, tertiary butyl acetate, and glycol ether acetates; or any combination thereof.

[0061] In certain embodiments, the at least one solvent may be selected from the following: alcohols, such as ethanol, methanol, ethoxyethanol, propanol, isopropanol or n-propanol, butanol, tertiary butanol, and secondary butanol; and ether solvents, such as the C of ethylene glycol and propylene glycol. 1-6 alkyl ethers or combinations thereof (i.e., mixed ethers); For example, but not limited to, they may be selected from those including glyme (dimethoxyethane), diglyme, triglyme, tetraglyme, and dipropylene glycol dimethyl ether, as well as cyclic ethers such as tetrahydrofuran.

[0062] Solvent combinations include combinations of alcohols such as glycol ethers: dipropylene glycol dimethyl ether: isopropanol or n-propanol; combinations of alcohols such as ethers: dipropylene glycol dimethyl ether: isopropanol or n-propanol, methanol, isobutanol, secondary butanol, tertiary butanol, ethoxyethanol and / or ethylhexanol; combinations of glycols and monoethers such as ethylene glycol monomethyl ether: ethanol, methanol, ethoxyethanol and / or isopropanol; combinations of ethers such as tetrahydrofuran: triglyme and tetrahydrofuran: dipropylene glycol dimethyl ether; combinations of solvents including ketones such as methyl ethyl ketone, methyl amyl ketone, methyl propyl ketone, etc. Typical solvent combinations include combinations of high boiling point solvents and low boiling point solvents.

[0063] Such solvent combinations include ether:alcohol combinations, such as glycol ethers, such as glycol diethers, such as diethers of alkylene glycols, including dipropylene glycol diether, such as dipropylene glycol dimethyl ether, and alcohols, such as aliphatic alcohols, such as C 2 ethers, such as isopropanol or n-propanol. 1-6 Or C 1-4 There is alcohol.

[0064] In certain embodiments, the solvent of the present disclosure may contain less than about 800 ppm water, such as less than about 700 ppm, 600 ppm, 500 ppm, 400 ppm, 300 ppm, 200 ppm, or less than 100 ppm water, to reduce or prevent precipitation of the surface exchange agent. In certain embodiments, the reactivation treatment comprises the solvent in an anhydrous form. In certain embodiments, it is required that no water be added to the reactivation treatment, and in certain embodiments, the reactivation treatment does not contain water.

[0065] The content of the at least two solvents is less than about 99.5% (based on the total weight of the reactivation treatment), such as less than about 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%, 91%, 90%, 89%, 88%, 87%, 86%, or 85%. In certain embodiments, the content of the at least two solvents is greater than about 85% (based on the total weight of the reactivation treatment), such as greater than about 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99%. In certain embodiments, the content of the at least two solvents may range between any two of these values. For example, the content of the at least two types of solvents contained in the reactivation treatment agent is between about 86% and about 99.5%, and may be, for example, between about 90% and about 99.5%, between about 92% and about 99%, or between about 94% and about 98%. In one embodiment, the content of the at least two types of solvents is greater than about 90% based on the total weight of the reactivation treatment agent, and may be, for example, between about 95% and about 98%.

[0066] The reactivation treatment agent may further include an additional solvent in addition to the at least two types of solvents described above. In this specification, the at least two types of solvents described above that do not include an additional solvent are also referred to as "composition solvent". Thus, the at least two types of solvents consist of "composition solvent", and may include "additional solvent" as an optional element, and may include incidental impurities as an optional element, and may include a small amount of water as described herein. In certain embodiments, the content of the "additional solvent" is less than about 10% (based on the total weight of the reactivation treatment agent), for example, less than about 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, or 1%. In one aspect, the additional solvent may be the same as the selection for the composition solvent. For example, in certain embodiments, the additional solvent may be selected from at least one of acetate and alcohol, for example, at least one of methoxypropyl acetate, methoxypropanol, and isopropanol.

[0067] Surface exchange agent: The reactivation treatment of the present disclosure includes at least one surface exchange agent in addition to at least two solvents. Suitable surface exchange agents include those that promote surface exchange of the co-cured film layers. Suitable surface exchange agents that promote surface exchange may include transesterification agents. Exemplary transesterification agents include those derived from titanates and zirconates or their chelates, such as C 1-10 Alkyl titanate, C 1-10 Alkyl titanate chelate, C 1-10 Alkyl zirconate, and C 1-10The at least one surface exchange agent may be selected from alkyl zirconate chelates, etc. Specific examples include tetraisopropyl titanate, tetra-n-propyl titanate, tetra-n-butyl titanate, tetra-2-ethylhexyl titanate, tetraethyl titanate, tetra-n-propyl zirconate, tetra-n-butyl zirconate, and combinations thereof. In certain embodiments, the at least one surface exchange agent is selected from at least one of tetra-n-propyl zirconate, tetra-n-butyl zirconate, zirconium-n-propoxide, tetra-n-propyl titanate, tetra-isopropyl alcohol, and tetra-n-butyl titanate.

[0068] The content of the at least one surface exchange agent in the reactivation treatment may be greater than about 0.001% (based on the total weight of the reactivation treatment), such as greater than about 0.01%, 0.05%, 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10%. In certain embodiments, the content of the at least one surface exchange agent in the reactivation treatment may be less than about 10% (based on the total weight of the reactivation composition), such as less than about 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%, 0.1%, 0.05%, or 0.01%. In certain embodiments, the content of the at least one surface exchange agent in the reactivation treatment may range between any two of these values ​​(based on the total weight of the reactivation composition). For example, the content of the at least one surface exchange agent may range from about 0.05% to about 10%, such as from about 1% to about 8%, or from about 2% to about 6%. In one embodiment, the content of the at least one surface exchange agent ranges from about 1% to about 8% based on the total weight of the reactivation composition.

[0069] Optional Additives: The reactivation treatment of the present disclosure may include at least one optional additive, for example, to modify drying time or reduce corrosion. Such additives include, but are not limited to, anti-corrosion additives and colorants, such as dyes and pigments. The at least one optional additive may be, for example, a colorant, such as a UV fluorescent dye, to indicate where the reactivation treatment has been sprayed or painted.

[0070] In certain embodiments, the at least one optional additive in the reactivation treatment agent of the present disclosure may be comprised of nanoparticles. The term "nanoparticles" as used herein refers to particles having a particle size of less than about 500 nm, such as less than about 450 nm, 400 nm, 350 nm, 300 nm, 250 nm, 200 nm, 150 nm, 100 nm, 90 nm, 80 nm, 70 nm, 60 nm, 50 nm, 40 nm, 30 nm, 20 nm, 10 nm, or 5 nm. These nanoparticles may be organic or inorganic nanoparticles. Examples of organic nanoparticles include carbon-based nanoparticles such as carbon black. Examples of inorganic nanoparticles include metal oxides of aluminum, zirconium, silicon, antimony, cerium, gadolinium, cobalt indium, molybdenum, neodymium, tellurium, yttrium, europium, barium, copper, lithium, titanium, and tungsten; carbides such as silicon carbide; sulfates such as BaSO4; carbonates such as CaCO3; phosphates such as Ca3(PO4)2 and FePO4; BiOCl; and yttria-stabilized zirconia.

[0071] As described below, all additives are optional and may be added to the reactivation treatment to further improve application of the reactivation treatment or to further enhance the performance properties of the final coating system. Suitable additives include, for example: (a) rheology control agents, such as hydroxypropyl methylcellulose (e.g., Methocel® 311), modified ureas (e.g., Byk® 411, Byk® 410), cellulose acetate butyrate (e.g., Eastman CAB-551-0.01, CAB-381-0.5, CAB-381-20), and polyhydroxycarboxylic acid amides (e.g., Byk® 405); (b) wetting agents, such as fluorochemical surfactants (e.g., 3M Fluorad®); (c) surfactants, such as fatty acid derivatives (e.g., AkzoNobel®, Bermodol SPS, etc.); 2543), quaternary ammonium salts, ionic surfactants, and nonionic surfactants; (d) dispersants, such as primary alcohol-based nonionic surfactants (e.g., Merpol® 4481, DuPont) and alkylphenol-formaldehyde-bisulfide condensates (e.g., Clariant® Dispersogen® 1494); (e) defoamers; (f) leveling agents, such as fluorocarbon modified polymers (e.g., EFKA® 3777); (g) pigments, such as those used in aerospace coating compositions, which may include organic phthalocyanine, quinalidone, diketopyrrolopyrrole (DPP), and diarylide derivatives, as well as inorganic oxide pigments (e.g., for reactivation treatments and to enhance the visibility of the coating); (h) fluorescent agents, such as, for example, fluorescent agents (RoyalePi (i) pigments, including organic and inorganic pigments such as phosphate esters (e.g., ADDAPT, Anticor® C6), alkyl ammonium salts of (2-benzothiazolithio)succinic acid (e.g., Irgacor® 153), triazine dithiols, and thiadiazoles;

[0072] In certain embodiments of the present disclosure, the at least one optional additive does not consist of or contain silanes and siloxanes, and thus the reactivation treatment in certain embodiments does not contain silanes or siloxanes.

[0073] When the reactivation treatment agent contains at least one type of optional additive, the content of the one type of optional additive is, for example, less than about 10% based on the total weight of the reactivation treatment agent. For example, when the optional additive is included, the combined content of all additives is less than about 10%, for example, less than about 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%, 0.1%, or 0.05%. In certain embodiments, when the optional additive is included, the combined content of all additives is greater than about 0.01%, for example, greater than about 0.05%, 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, or 9%. In certain embodiments, when the optional additive is included, the combined content of all additives may be in a range between any two of the above values, for example, in a range of about 0.01% to about 10%. For example, it may be in the range of about 0.05% to about 5%, for example, about 0.1% to about 3%, or about 0.5% to about 2%. <Additional coating layer>

[0074] According to the reactivation treatment method of the present disclosure, after applying the reactivation treatment agent to the co-cured film layer on the substrate, at least one additional coating layer is applied. The expression "additional coating layer" as used herein is used in its broadest sense and refers to decorative topcoats; undercoats; intermediate coatings; primers; sealers; lacquers; pigmented or transparent coatings (e.g., clearcoats), coatings designed for specific purposes such as corrosion protection, heat resistance, or camouflage; high gloss, matte, textured or smooth finish coatings; and / or coatings containing special additives such as metal, mica, or glass flakes. In certain embodiments, the at least one additional coating layer is a clearcoat or transparent coating.

[0075] In some embodiments, the at least one additional coating layer applied to the co-cured film layer by the reactivation process of the present disclosure can be more resistant to environmental conditions, such as chemicals or solar radiation, such as ultraviolet (UV), than additional coating layers applied by conventional reactivation processes, such as those involving sanding of the co-cured film layer. For example, the surface of a composite structure may be exposed to certain environmental conditions, such as solar radiation, that can degrade the composite structure. In contrast, the coating layer added by the reactivation process of the present disclosure is more resistant to such environmental conditions than additional coating layers that are not applied by the application of the reactivation process of the present disclosure. In some exemplary embodiments, a composite structure includes a co-cured film layer and at least one layer added to the co-cured film layer by the reactivation process of the present disclosure, and has UV resistance, for example, to UV radiation of about 200 nanometers to about 800 nanometers, for example, from about 200 nanometers to about 400 nanometers.

[0076] In certain embodiments, the at least one additional coating layer applied to the co-cured film layer by the reactivation process of the present disclosure exhibits increased adhesion to the co-cured film layer as compared to additional coating layers applied by conventional reactivation methods, such as those involving sanding of the co-cured film layer. As will be described in more detail below, the adhesion (e.g., intercoat adhesion) of the at least one additional coating layer to the co-cured film layer can be measured by techniques known in the art. <Surface reactivation treatment method>

[0077] The reactivation treatment method of the present disclosure includes applying a reactivation treatment or components of the reactivation treatment to the surface of a co-cured film layer that has previously been cured to a substrate or an interlayer on a substrate. For example, the reactivation treatment method of the present disclosure can be used on a film that has previously been co-cured to a substrate and has been cured or aged to a point where a newly applied coating layer or element will adequately adhere to the substrate without a treatment (e.g., mechanical polishing or other surface roughening) to reactivate adhesion.

[0078] The application time window described above, as will be appreciated by those skilled in the art, defines an environmental time frame, and any newly applied film layer will not adhere to operational performance requirements if aged or cured beyond the time window for adequate adhesion to additional coatings applied thereon. For example, the curing of a co-cured film layer on a substrate will not adhere to new coatings after the time frame. Without wishing to be bound by theory, it is believed that applying a reactivation treatment to the surface of the co-cured film layer can cause the co-cured film layer to swell to some extent, which can expand the entanglement of the polymer chain network in the reactivation treatment. This swelling of the co-cured film layer creates spaces between the polymers to allow for the incorporation of newly applied additional coating layers. Furthermore, without wishing to be bound by theory, it is believed that the reactivation treatment in the disclosed method reactivates the co-cured film layer by forming chemical "bridges" between the reactive sites in the newly applied additional coating layers and the reactive sites in the co-cured film layer.

[0079] In certain embodiments, the co-cured film layers are cured at elevated temperatures. For example, in certain embodiments, the co-cured film layers are cured at temperatures greater than about 50° C., such as at least about 65° C., about 100° C., at least about 121° C., at least about 150° C., at least about 175° C., at least about 185° C., or at least about 200° C. In certain embodiments, the co-cured film layers are cured at temperatures ranging from about 65° C. to about 200° C., such as from about 100° C. to about 185° C., or from about 121° C. to about 175° C. ℃In further embodiments, the co-cured film layer is cured for a time period of less than about 48 hours, such as less than about 24 hours, less than about 12 hours, less than about 8 hours, or at least about 2 hours. In certain embodiments, the co-cured film layer is cured for a time period of about 2 hours to about 24 hours, such as about 2 hours to about 12 hours, or about 2 hours to about 4 hours. In further embodiments, the co-cured film layer is cured at a temperature range of about 65° C. to about 200° C., such as about 100° C. to about 185° C., or about 121° C. to about 175° C., and for a time period of about 2 hours to about 24 hours, such as about 2 hours to about 12 hours, or about 2 hours to about 4 hours. In certain embodiments, the co-cured film layer is cured at a temperature greater than 50° C. In certain embodiments, the co-cured film layers are cured in an autoclave at about 185 ℃ The curing was carried out at a temperature of about 2 hours to about 12 hours.

[0080] The co-cured film layer already applied to the substrate may be a post-cured, aged, and / or in-service coating, where an in-service coating refers to a coating that has been previously applied and cured and is suitable for service or has actually been used in service, for example, on an aircraft panel of an aircraft that has already flown at least once. The application time window depends on the type of co-cured film layer and / or the type of substrate, and other factors related to the curing process may also need to be considered, such as time, humidity, temperature, pressure, type of UV exposure, etc.

[0081] It is understood that the reactivation treatment method of the present disclosure is a chemical method that modifies the surface of the co-cured film layer to promote an interaction that forms adhesion to additional coatings. Without wishing to be bound by theory, it is believed that the solvent and surface exchange agent interact with the co-cured film layer modifier to modify the coating surface chemistry and / or surface structure, making the surface more receptive to other elements, such as, but not limited to, at least one additional coating layer. These solvents, surface exchange agents, and optional additives may be selected to maintain the integrity of the co-cured film layer and its underlying coatings and the overall substrate structure. In addition, the reactivation treatment may be selected for compatibility with the substrate in case of accidental contact of the reactivation treatment with an uncoated substrate surface.

[0082] Application of the reactivation treatment or one or more components thereof can be accomplished using any liquid application method known to one of skill in the art, such as spray, brush, dip, knife, blade, hose, roller, wipe, curtain, flood, flow, mist, pipette, aerosol, or combinations thereof. In one embodiment, application is by spraying, for example, and the reactivation treatment can be a reactivation formulation formulated for spraying.

[0083] The reactivation method of the present disclosure may be carried out at ambient temperatures ranging from about 10° C. to about 35° C., for example, from about 15° C. to about 30° C., or from about 20° C. to about 25° C. The reactivation method may also be carried out at pressures near typical atmospheric pressures (e.g., from about 90 kPa to about 105 kPa, for example, about 101 kPa). Subsequent additional coatings may also be cured at ambient temperatures, for example, from about 10° C. to 35° C. Alternatively, subsequent additional coatings or layers may be cured at elevated temperatures, such as, for example, under the curing conditions for the co-cured film layer described herein (e.g., autoclave). In certain embodiments, the application of the reactivation treatment does not require a step of preheating the co-cured film layer and the substrate.

[0084] The reactivation treatment or one or more of its individual components can be applied to small or large areas, to portions of larger components or parts, or to entire infrastructure structures, such as those related to aerospace (e.g., aircraft), automotive (e.g., vehicles), marine (e.g., ships), transportation (e.g., trains), military (e.g., helicopters, missiles), or construction industry (e.g., buildings, factories, floors). The surfaces to which the reactivation treatment is applied can have simple or complex geometries, including two-dimensional or three-dimensional shapes. The reactivation treatment can be applied once or multiple times before interacting with one or more additional coating layers. The time for exposing the co-cured film layer to the reactivation treatment is not particularly limited. For example, the exposure time can be short, for example, about 5 minutes, about 10 minutes, or about 15 minutes, or long, for example, about 12 hours, about 18 hours, or about 24 hours, without compromising the integrity of the outermost co-cured film layer and the underlying co-cured film layers or coating structure and substrate. In one embodiment, the exposure time should be long enough to allow all or a portion of the solvent in the reactivation treatment to evaporate and the surface of the co-cured film layer to be visibly dry. This time can depend, for example, on the air flow and temperature in the application environment of the reactivation treatment. As the relative humidity approaches 100%, the application time window during which additional coatings can be applied narrows.

[0085] After the co-cured film layer is reactivated, one or more coating layers may be added immediately or at a later time, provided that the surface of the reactivated co-cured film layer remains largely uncontaminated. Additional coating layers may include elements such as adhesives, sealants, pinhole fillers, stencils, sign plates, pressure sensitive decals, or logos.

[0086] The quality of adhesion between the reactivated co-cured film layer and an additional coating layer, or between the reactivated co-cured film layer and a substrate (or an intermediate coating), for a given purpose can be evaluated using any suitable method known in the art, including, but not limited to, standards such as ASTM, ISO, or SAE (ASTMG-73), in-house test methods that simulate in-service performance, in-service performance itself, and real-life or accelerated durability tests.

[0087] For aerospace coatings, test methods based on water impact can be employed, such as the rotating arm rain erosion test and the Single Impact Jet Apparatus (SUA) (MIJA Limited, Cambridge, UK) with immersion times of 16 to 24 hours. In certain embodiments, the rotating arm rain erosion test, which simulates the effects of rain erosion on commercial aircraft, can be used to evaluate intercoat adhesion in aerospace coatings. In these cases, the degree of overcoat delamination is related to the level of intercoat adhesion, with greater overcoat delamination indicating a lower level of intercoat adhesion, where overcoat refers to any additional coating layer applied over the reactivated co-cured film layer. These methods are described in the reference Berry DH and Seebergh JE, "Adhesion Test Measurement Comparison for Exterior Decorative Aerospace Coatings: Two Cases" (p. 12). Studies," Proceedings 26th Annual Adhesion Society Meeting, Myrtle Beach, SC, pp. 228-230 (2003).

[0088] In certain embodiments, the Rain Erosion Test can identify the degree of intercoat adhesion between an overcoat and its underlying coating, such as between a co-cured film layer reactivated by the disclosed method and an additional coating layer applied thereto, based on the percent peeled area or maximum tear length of the overcoat after exposure to a 30 minute simulated rainfall. Intercoat adhesion can be quantified by visual inspection or image analysis, including measurement. FIG. 2 visually illustrates the scale of 1 to 10 that corresponds to the maximum tear length and percent peeled area of ​​the coating in the Rain Erosion Test described above. For example, in FIG. 2, a level 10 intercoat adhesion is a maximum tear length of 0.02 inches. (0.508mm) Level 9 intercoat adhesion corresponds to a maximum tear length of 0.02 to 0.06 inches. (0.508~1.524mm) Level 8 intercoat adhesion corresponds to a maximum tear length of 0.06 to 0.12 inches, which corresponds to a removal area of ​​1% or less. (1.524~3.048mm) Similarly, level 7 intercoat adhesion corresponds to a maximum tear length of 0.12 to 0.25 inches. (0.508~6.35mm) Level 6 intercoat adhesion corresponds to a maximum tear length of 0.25 to 0.5 inches. (6.35~12.7mm) and the peeling area is 25% or less. Level 5 intercoat adhesion corresponds to a coating peeling area of ​​25% or a maximum tear length of 0.75 inches. (19.05mm) Level 4 intercoat adhesion corresponds to a coating peel area of ​​40% or a maximum tear length of 0.75 inches. (19.05mm)Intercoat adhesion level 3 corresponds to a coating having a 50% peeled area. Intercoat adhesion level 2 corresponds to a coating having a 75% peeled area, and intercoat adhesion level 1 corresponds to a coating having a 100% peeled area. According to the method of the present disclosure, additional coating layers can be applied to the reactivated co-cured film layer to form additional coating layers having intercoat adhesion levels, for example, 10, 9, 8, 7, 6, 5, 4, 3, or 2, depending on various factors including the type of coating used. In one embodiment, the level is at least 7, such as at least 8 or at least 9. The disclosed method can reduce the percent peeled area in a rain erosion test to about 0%, for example, less than about 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 15%, 20%, 25%, 30%, 40%, 50%, 60%, 70%, 75%, 80%, or 90%, or any range therebetween, depending on a variety of factors including the type of coating used. Additionally, the disclosed method can reduce the tear length in a rain erosion test to about 1 inch. (25.4mm) The distance can be kept to less than about 0.5 inches. (12.7mm) Tear length less than 0.25 inches (6.35mm) Tear length less than 0.12 inches (3.048mm) Tear length less than 0.06 inches (1.524mm) Tear length of less than 0.02 inches (0.508mm) It will be appreciated that a greater degree of overcoat peeling indicates weaker intercoat adhesion.

[0089] In a specific embodiment, Single Impact Jet Apparatus (SUA, Cambridge) testing can be performed using an instrument configured to use a 0.8 mm nozzle and 0.22 5.5 mm Crosman Accupell Pointed Pellets (#11246). The test involves immersion in water for approximately 16-18 hours and a 45° specimen to vary the geometry of the droplet. A single water jet is used with an impact velocity of approximately 600+25 m / s.

[0090] In a particular embodiment, the rain erosion test can be performed using a rotating arm rain erosion tester with a 1.32 m (52 ​​inch) zero lift helicopter-like propeller rotating at 3,600 rpm. The overcoat (e.g., an additional coating layer on a reactivated co-cured film layer) can be applied to a paint thickness of 80 to 120 microns using masking to create a leading edge. The midpoint of the test sample has a paint thickness of approximately 170 ms. -1 The effective rainfall density is 2.54×10 for raindrops of about 2 mm. -5 kmh -1 (1 inch per hour). In certain embodiments, the effect of rain erosion may be determined after 30 minutes of testing, and the intercoat adhesion of the test samples may be evaluated by the amount of coating peel or tear length as described above.

[0091] The adhesive bond between the co-cured film layer and the substrate (or layers therebetween), or between the co-cured film layer and additional coating layers, may be evaluated using any other method known in the art, such as, for example, wet and dry cross-hatch scribe tests. The dry adhesion of the coatings may be evaluated using ASTM D3359, Standard Test Methods for Measuring Adhesion by Tape Test, Test method B. In certain embodiments, a cross-hatch pattern may be scribed through each coating composition to the substrate. The coatings are then scribed using a 1 inch wide tape such as 3M® 250. (25.4mm) Then, for example, 4.5 lbs masking tape is applied. (approx. 2Kg) A rubber-covered roller is passed over the tape twice to press it down. The tape is then removed in one swift motion in a direction perpendicular to the panel. The paint in the cross-hatched areas is then visually inspected to determine the percent area of ​​coating removed, and adhesion is assessed as above.

[0092] In aerospace applications, the reactivation methods of the present disclosure can provide the advantages of improving flow times of the reactivation process, increasing repeatability and consistency across large areas and between operators, and improving the ergonomics of the process. These and other advantages can result in net cost savings.

[0093] The disclosed method promotes adhesion of one or more additional coating layers to a co-cured film layer on a substrate by applying a reactivation treatment to the co-cured film layer, the reactivation treatment including at least two solvents and a surface exchange agent, which may optionally include at least one additive, to reactivate the surface of the co-cured film layer and improve adhesion to the additional coating layer. The combination of the solvent and surface exchange agent disrupts the surface of the co-cured film layer and reactivates adhesion to, for example, the additional coating, thereby providing effective adhesion to meet operational performance, such as the aerospace ASTM intercoat adhesion properties described herein.

[0094] The method of the present disclosure may further include one or more optional steps, such as at least one of washing, wiping, and drying the co-cured film layer before applying the reactivation treatment to the surface of the co-cured film layer. In certain embodiments, the method of the present disclosure may further include washing the co-cured film layer by applying a cleaning solvent to the co-cured film layer before applying the reactivation treatment to the surface of the co-cured film layer. The cleaning solvent may be any solvent with optional addition of a desired component to clean the surface of the co-cured film layer before reactivation. The cleaning solvent may be applied to the co-cured film layer by any means known in the art, such as, for example, wiping the co-cured film layer with the cleaning solvent or spraying the cleaning solvent. In certain embodiments, the cleaning solvent may include a volatile organic solvent, such as, for example, methyl ethyl ketone, toluene, isopropyl alcohol, and methyl isobutyl ketone. Applying the cleaning solvent to the surface of the co-cured film layer may ensure that the co-cured film layer is clean and free of contaminants and debris. Other pretreatment steps are contemplated prior to application of the reactivation treatment to the co-cured film layer. For example, a non-reactivation step, such as a cleaning step or a mechanical abrasion step to remove surface contaminants, may be performed prior to application of the reactivation treatment. It is understood that pretreatment steps can be omitted from the methods of the present disclosure. For example, in certain embodiments of the methods of the present disclosure, the co-cured film layer is not sanded or mechanically abraded after it is cured and before the reactivation agent is applied.

[0095] The method of the present disclosure may include one or more optional steps after applying the reactivation treatment to the surface of the co-cured film layer, such as at least one of drying, washing, and wiping the surface of the reactivated co-cured film layer. In one aspect, the method includes drying the surface of the reactivated co-cured film layer prior to application of the additional coating layer. In certain embodiments, the drying step may be performed for at least about 15 minutes, such as at least about 30 minutes, at least about 45 minutes, at least about 1 hour, at least about 2 hours, at least about 4 hours, at least about 8 hours, at least about 1 day, or any range of these lengths of time, such as from about 15 minutes to about 1 day, from about 30 minutes to about 8 hours, or from about 45 minutes to about 4 hours.

[0096] In certain embodiments, the additional coating layers may be applied to an average dry film thickness (dft) of at least about 1 mil dft (about 25 microns), for example, an average dft ranging from about 1 mil to about 3 mils. The additional coating layer or layers may be applied to a thickness sufficient for the intended use of the additional coating layer, such as restoring or improving the gloss of the co-cured film layer. At least one additional coating layer may be applied, for example, to a thickness of at least 1 mil, for example, in a range of about 2 mils to about 25 mils.

[0097] It will be appreciated that one or more steps in the process may be repeated to provide additional coating layers to the previously coated co-cured film layer and substrate, and that further aspects described herein are also applicable to the methods described above.

[0098] Although one or more exemplary embodiments have been described in the present teachings, modifications and / or variations can be made to the described examples without departing from the scope or concept of the present disclosure. Furthermore, the term "about" as used herein indicates that the described value can be modified to some extent without substantially affecting the described embodiment.

[0099] Although the disclosed methods have been described in connection with coating aircraft, the disclosed methods may be practiced to apply coatings to any type of surface, without limitation, in this regard, such surfaces may include, for example, the surface of an automobile, including a tractor trailer, the surface of a building, the surface of a banner, or any type of movable or stationary structure, object, article, material, etc., having a surface upon which some image or image may be placed. Additionally, such surfaces may be flat, simply curved, and / or have a compound curved surface. [Example]

[0100] The following examples are presented to further define the various species of the present disclosure. The examples are for illustrative purposes only and are not intended to limit the scope of the present disclosure. Unless otherwise stated, parts and percentages indicated are by weight.

[0101] First, nine samples were prepared. Each sample was prepared by applying a polyurethane-containing co-curable film layer onto the composite structure and then heating the composite structure in an autoclave (at a pressure of 100 psi). (689.476KPa)The composite structures were prepared by curing the composites at room temperature for at least 14 days (at 220°F / °C and maintaining the elevated temperature at 121°C for at least one hour), sanding, and applying the coating layers. The first coating layer was a polyamide paint coating, over which a polyurethane basecoat and a polyurethane clearcoat were applied. After applying these coating layers, the composite structures were cured either at room temperature for at least 14 days or at elevated temperature (between 38°C and 55°C) for at least three days. The samples were then subjected to a rotating arm rain erosion test similar to ASTM G-73, as described in Berry DH and Seebergh JE, "Adhesion Test Measurement Comparison for Exterior Decorative Aerospace Coatings: Two Case Studies," Proceedings 26th Annual Adhesion Society Meeting, Myrtle Beach, SC, pp. 228-230 (2003). Three samples were exposed to no ultraviolet (UV) light (see Figure 3A) and three samples were exposed to 200 kJ / m before sanding the film layers co-cured on the composite structure. 2 The three samples were irradiated with ultraviolet light (see Figure 3B). For the 1000kJ / m 2 The cells were then irradiated with ultraviolet light (see FIG. 3C).

[0102] The three samples shown in Figure 3A were co-cured film layers that had been reactivated by sanding and not exposed to UV light. As shown in Figure 3A, degradation of the film layers occurred in at least one of the three samples. For example, the intercoat adhesion (31) of the panel shown in the top row of Figure 3A was equivalent to Level 4 (i.e., approximately 40% of the coating area has peeled off, or 0.75 inches). (19.05mm)The inter-coat adhesive strength (32) of the panel shown in the middle row was equivalent to level 6, and the inter-coat adhesive strength (33) of the panel shown in the bottom row was equivalent to level 9.

[0103] The three samples shown in FIG. 3B are co-cured film layers that were reactivated by sanding, with a 200 kJ / m 2 The three samples shown in Figure 3C were co-cured film layers that had been reactivated by sanding, and were exposed to 1,000 kJ / m2 of UV light. 2 As shown in Figure 3B, the sample was irradiated with 200 kJ / m 2 The film layer also deteriorated in the sample exposed to 1,000 kJ / m of UV light. 2 The same was true for the sample irradiated with UV light (see FIG. 3C). For example, the intercoat adhesion (34) of the panel shown in the top row of FIG. 3B was equivalent to level 7, the intercoat adhesion (35) of the panel shown in the middle row of FIG. 3B was equivalent to level 4, and the intercoat adhesion (36) of the panel shown in the bottom row of FIG. 3B was equivalent to level 6. In addition, the intercoat adhesion (37, 39) of the panels shown in the top and bottom rows of FIG. 3C was equivalent to level 5, and the intercoat adhesion (38) of the panel shown in the middle row was equivalent to level 4. The results of the deterioration of these coating layers indicate that the coating layers applied to the sanded co-cured film layer did not adhere sufficiently to the co-cured film layer.

[0104] Next, nine more samples were prepared. Each sample was prepared by applying a co-curable film layer onto the composite structure, curing as described for the first nine samples (i.e., curing in an autoclave at 100 psi and 121° C. for at least one hour), and then wiping with Sur-Prep AP-1 available from Zip-Chem, a reactivation treatment comprising tetra-n-propyl zirconate in a dipropylene glycol dimethyl ether / n-propanol solvent. Additional coating layers were then applied thereover. The first additional coating layer was a polyamide paint coating, over which a polyurethane basecoat and polyurethane clearcoat were applied. After application of these additional coating layers, each composite structure was cured either at room temperature for at least 14 days or at elevated temperature (between 38° C. and 55° C.) for at least three days. As with the first nine samples, three samples were not exposed to ultraviolet (UV) light (see Figure 4A) and three samples were exposed to 200 kJ / m before applying Sur-PrepAP-1 to the film layer co-cured on the composite structure. 2 For the three samples, the UV light was irradiated at 1000 kJ / m (see Figure 4B). 2 (See FIG. 4C). Finally, the samples were subjected to a rotating arm rain erosion test (according to BSS7393).

[0105] As shown in Figures 4A to 4C, in all nine samples, the coating did not deteriorate or deteriorated only slightly. The intercoat adhesion strength of each panel ranged from level 6 to level 10. Specifically, in Figure 4A, which shows a sample that was not irradiated with ultraviolet light, the intercoat adhesion strength (41) of the panel shown in the upper row was equivalent to level 8, the intercoat adhesion strength (42) of the panel shown in the middle row was equivalent to level 9, and the intercoat adhesion strength (43) of the panel shown in the lower row was equivalent to level 8. 200 kJ / m 2In FIG. 4B, which shows a sample irradiated with ultraviolet light of 200 kJ / m, the inter-coat adhesive strength (44) of the panel shown in the upper row corresponds to level 9, the inter-coat adhesive strength (45) of the panel shown in the middle row corresponds to level 8, and the inter-coat adhesive strength (46) of the panel shown in the lower row corresponds to level 9. 2 In FIG. 4C, which shows a sample irradiated with 200 kJ / m of UV light, the intercoat adhesion strength (47) of the panel shown in the top row corresponds to level 8, the intercoat adhesion strength (48) of the panel shown in the middle row corresponds to level 7, and the intercoat adhesion strength (49) of the panel shown in the bottom row corresponds to level 7. The result that these coating layers did not deteriorate is that the coating layer applied after wiping off the co-cured film layer with the reactivation treatment agent was irradiated with 200 kJ / m 2 Even after being exposed to 1,000 kJ / m2 of ultraviolet light, 2 It was found that the adhesive bonded to the co-cured film layer adequately even after exposure to UV light up to 1000 nm. <Additional Notes>

[0106] Furthermore, the present disclosure also encompasses embodiments according to the following appendices:

[0107] 1. A method for reactivating a co-cured film layer (2) disposed on a composite structure, comprising: applying a reactivation treatment to the co-cured film layer (2) comprising at least two solvents and a surface exchange agent comprising a metal alkoxide or a chelate thereof; applying the reactivation treatment to form a reactivated co-cured film layer (2); The method, wherein the co-cured film layer (2) has been previously cured at a curing temperature greater than about 50°C.

[0108] 2. The method of claim 1, further comprising applying an additional coating layer (4) to the reactivated co-cured film layer (2).

[0109] 3. The method of claim 1 or 2, wherein the curing is performed at a curing temperature of at least about 121° C.

[0110] 4. The method according to any one of claims 1 to 3, which does not include sanding the co-cured film layer (2) prior to applying the reactivation treatment.

[0111] 5. The method according to any one of claims 1 to 4, wherein the co-cured film layer (2) is cured in an autoclave.

[0112] 6. The method of any one of claims 1 to 5, wherein the co-cured film layer (2), when cured, comprises a polyurethane, a polyimide, a polyester, or an epoxy.

[0113] 7. The method of any one of claims 1 to 6, wherein the co-cured film layer (2), upon curing, comprises a polyurethane.

[0114] 8. The method of any one of claims 1 to 7, wherein the surface exchange agent is zirconium propoxide.

[0115] 9. The method according to any one of claims 1 to 8, wherein the at least two solvents are dipropylene glycol dimethyl ether and n-propanol.

[0116] 10. The method of any one of claims 1 to 9, further comprising applying a cleaning solvent prior to or simultaneously with applying the reactivation treatment.

[0117] 11. The method of claim 2, wherein the additional coating layer (4) is a clear coat.

[0118] 12. The method according to claim 2, wherein the additional coating layer (4) has an intercoat adhesion level (31, 32, 33, 34, 35, 36, 37, 38, 39, 41, 42, 43, 44, 45, 46, 47, 48, 49) in the range of 6 to 10 after a rotating arm rain erosion test.

[0119] 13. The method according to claim 2, wherein the additional coating layer (4) has an intercoat adhesion level (31, 32, 33, 34, 35, 36, 37, 38, 39, 41, 42, 43, 44, 45, 46, 47, 48, 49) in the range of 8 to 10 after a rotating arm rain erosion test.

[0120] 14. A co-cured film layer (2) disposed on the composite structure; a reactivation treatment layer comprising a surface exchange agent comprising a metal alkoxide or a chelate thereof, the reactivation treatment layer being disposed on the co-cured film layer (2) to form a reactivated co-cured film layer (2); The co-cured film layer (2) was previously cured at a temperature of at least about 50° C., a reactivated co-cured film layer (2).

[0121] 15. The reactivated co-cured film layer (2) of claim 14, wherein the co-cured film layer (2) has not been sanded.

[0122] 16. An additional coating disposed on the reactivated co-cured film layer (2). 16. The reactivated co-cured film layer (2) of claim 14 or 15, further comprising a co-curing layer (4).

[0123] 17. The reactivated co-cured film layer (2) of claim 16, wherein the additional coating layer (4) has an intercoat adhesion level (31, 32, 33, 34, 35, 36, 37, 38, 39, 41, 42, 43, 44, 45, 46, 47, 48, 49) in the range of 6 to 10 after a rotating arm rain erosion test.

[0124] 18. The reactivated co-cured film layer (2) according to any one of claims 14 to 17, wherein the surface exchange agent is zirconium propoxide.

[0125] 19. The reactivated co-cured film layer (2) of any one of Appendices 14 to 18, wherein the co-cured film layer (2), upon curing, comprises a polyurethane, a polyimide, a polyester, or an epoxy.

[0126] 20. An aircraft part having a co-cured film layer (2) disposed thereon, A composite structure; and a reactivated co-cured film layer (2) according to any one of appendixes 14 to 19, cured on a surface of the composite structure.

Claims

1. 1. A method for reactivating a co-cured film layer disposed on a composite structure, comprising: applying a reactivation treatment to the co-cured film layer, the reactivation treatment comprising at least two solvents and a surface exchange agent comprising a metal alkoxide or chelate thereof; and applying the reactivation treatment to form a reactivated co-cured film layer; The method wherein the co-cured film layer was previously cured at a cure temperature greater than 50°C.

2. The method of claim 1 further comprising applying an additional coating layer to the reactivated co-cured film layer.

3. 3. The method of claim 1 or 2, wherein the curing is performed at a curing temperature of at least 121°C.

4. The method of any of claims 1 to 3, which does not include sanding the co-cured film layer prior to applying the reactivation treatment.

5. The method of any of claims 1 to 4, wherein the co-cured film layer, when cured, comprises a polyurethane, a polyimide, a polyester, or an epoxy.

6. The method according to any one of claims 1 to 5, wherein the surface exchange agent is zirconium propoxide.

7. The method of claim 2 , wherein the additional coating layer is a clearcoat.

8. The method of claim 2, wherein the additional coating layer has an intercoat adhesion level in the range of 6 to 10 after a rotating arm rain erosion test.

9. a co-cured film layer disposed in the composite structure; a reactivation treatment layer comprising a surface exchange agent comprising a metal alkoxide or chelate thereof, the reactivation treatment layer disposed on the co-cured film layer to form a reactivated co-cured film layer; A reactivated co-cured film layer, wherein the co-cured film layer was previously cured at a temperature of at least 50°C.

10. 1. An aircraft part having a co-cured film layer disposed thereon, comprising: A composite structure; and a reactivated co-cured film layer according to claim 9 cured onto a surface of the composite structure.

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