Thermoplastic surfaces with directly bonded chemical sealants

Abstract

The present disclosure is directed to methods for preparing a thermoplastic surface suitable for application of a paint, adhesive, or surface treatment film, and to structures derived or derivable from these methods. The present disclosure is also directed to composite structures comprising a thermoplastic substrate having a chemical sealant bonded directly to its surface, the chemical sealant providing the thermoplastic surface with a surface suitable for adhering an adhesive, paint, and / or surface treatment film to the thermoplastic surface.

Description

[Technical field]

[0001] This disclosure is directed to methods for treating thermoplastic surfaces to render them suitable for the application of paints, adhesives, or surface treatment films, and to structures derived or derivable from these methods. [Background technology]

[0002] Fiber reinforced polymer matrix composites are high performance structural materials commonly used in aircraft parts, high performance automobiles, boat hulls, and bicycle frames because they can withstand harsh environments, have high specific strength or strength-to-density ratios, and are lightweight.

[0003] Thermosetting resins, combined with an autoclave curing process, have been the central component of aerospace composites since their introduction into the aerospace industry. The continuing trend to optimize the cost of raw materials and associated processing costs has accelerated the use of thermoplastic resins in place of thermosetting resins. Thermoplastic resins, unlike thermosetting resins, do not need to be chemically crosslinked and simply harden under sufficient heat to be molded and maintain their shape at a much faster rate than thermosetting resins do. However, thermoplastic materials applied in the aerospace industry present surfaces to which paints and adhesives will not adhere, at least to the level enjoyed by thermosetting surfaces.

[0004] Direct painting of thermoplastic surfaces is very difficult due to the low surface energy of the substrate. Typical pretreatment methods for thermoplastic substrates, including plasma, UV, etching, flame, and sanding, do not allow multiple coatings to adhere sufficiently for the demanding requirements of aerospace specifications.

[0005] In part for this and other reasons, composite structures used in the aerospace industry today typically include a thermosetting surface treatment film to provide the composite structure with the necessary performance characteristics before painting. Surface treatment films, such as epoxy-based films, are often incorporated into polymer composites to provide the composite with the surface quality required for aerospace applications. Additionally, these surface treatment films may be functionalized to improve their resistance to, for example, lightning strikes, electrostatic discharge, and electromagnetic discharge.

[0006] More recently, however, the aerospace industry has been exploring new coating methods that do not add additional areal weight of the surface treatment film.

[0007] To enable coatings, adhesives, and surface treatment films to bond to these low energy surfaces, several strategies have been developed to make the surface more amenable to bonding prior to the application of the adhesive or coating, including chemical priming, the use of chemical adhesive compositions specifically formulated for use in bonding these substrates, physical abrasion or chemical roughening, flame treatment, and acid or plasma etching. However, each of these methods has tradeoffs that must be considered.

[0008] It will be appreciated that chemical treatments such as acid etching or chemical activation are limiting from a commercial standpoint due to safety and waste disposal concerns, process control, and cost.

[0009] Similarly, the chemical inertness of the surface of thermoplastic materials presents challenges with respect to the use of adhesives and surface treatment films. It is known in the adhesive industry that certain substrates, such as certain high performance plastics, are difficult to bond. Thermoplastics such as PEEK (polyetheretherketone); PPS (polyphenylene sulfide); polyacrylamide (PARA) or polyetherimide (PEI) are attractive structural polymers in terms of their high specific strength or strength to density ratio, but are also characterized by poor bonding properties. Again, the low surface energy of thermoplastics is believed to be the cause of this. Application of UV / plasma to a thermoplastic surface creates polar functional groups on the surface, raising the surface energy and improving wetting and adhesion. These new polar groups often allow for the formation of chemical bonds with the adhesive, which further improves bond strength.

[0010] The chemical reactivity capability of the functional groups is strongly dependent on the adhesive chemistry. The functional groups are often not reactive enough for chemical bonding with various adhesives. Higher curing temperatures are required to overcome the lack of reactivity of certain types of adhesives. In addition, some aggressive adhesives require high temperatures for proper wetting of the substrate. The aerospace industry continues to need bonding methods that can be used with a wide variety of adhesives at lower curing temperatures.

[0011] Similarly, plasma techniques are useful but often require extensive equipment, and one of the drawbacks is the length of time that plasma-treated surfaces retain their ability to accept paints and adhesives.

[0012] Primers can be used to great effect, but another method of activating the surface for subsequent bonding is always necessary. This is especially true for PEEK, PARA, PPS, or PEI, which tend to be difficult plastics to bond to and typically have lower bond strengths than other plastics. This is generally true even when a primer is used.

[0013] Despite the existence of state of the art proposed solutions to these problems, it is desirable to provide alternative solutions so that more options are available to end users. This disclosure is directed to providing expanded options to the industry. Summary of the Invention [Means for solving the problem]

[0014] The present disclosure is directed to composite structures including thermoplastic substrates having a chemical sealant bonded to one or more substrate surfaces, methods of making these composite structures, and articles derived therefrom and derivable therefrom that include these composite structures.

[0015] Definitions of thermoplastic substrates are provided elsewhere herein. Although not necessarily so limited, in certain more specific embodiments, the thermoplastic substrate includes: (a) polyaryletherketones such as polyetheretherketone (PEEK), polyetherketoneketone (PEKK), polyetherketone (PEK), polyetheretherketoneketone (PEEKK), or polyetherketoneetherketoneketone (PEKEKK); (b) a polymer containing a phenyl group bonded directly to a carbonyl group, optionally the carbonyl group being part of an amide group, such as polyacrylamide (PARA); (c) polyphenylene sulfide (PPS); (d) polyphenylene oxide (PPO); or (e) Polyetherimide (PEI).

[0016] Additionally or alternatively, the thermoplastic substrate comprises a thermoplastic polymer that includes some chemical bonds that are susceptible to at least partial photolytic cleavage upon irradiation with actinic radiation of sufficient intensity and duration, in some of these embodiments, the actinic radiation includes radiation having at least one wavelength in the range of about 10 nm to about 500 nm or about 100 nm to about 450 nm, preferably in the range of about 200 nm to about 350 nm.

[0017] Additionally or alternatively, the thermoplastic substrate may have a bonding strength of less than about 0.1 J / cm at at least one wavelength. 2 ~About 300J / cm 2 0.5 J / cm2 at least at one wavelength. 2 ~About 250J / cm 2 or about 1.5 J / cm 2 ~About 250J / cm 2 The thermoplastic polymer comprises a thermoplastic polymer susceptible to at least partial photolytic cleavage upon exposure to at least one wavelength of actinic radiation with energies in the range of 100 .mu.m to 100 .mu.m.

[0018] Chemical sealants are described more broadly elsewhere herein, but for the sake of preliminary understanding, the term "chemical sealant" may be described in terms of mono-, di-, or poly-functional organic, inorganic, or organometallic compounds that exhibit pendant (such as alkyl or aryl) or functional groups that, upon adhering to the surface of a thermoplastic substrate, can promote adhesion of a paint, paint primer, or adhesive thereto. In some embodiments, the pendant or functional groups are chemically bonded to another material (e.g., a paint, adhesive, or surface layer), thereby forming a bond (e.g., a covalent chemical bond) between the thermoplastic substrate and the other material.

[0019] In separate embodiments, the chemical sealant consists of, consists essentially of, or includes an organic or organometallic compound having one or more of the functional groups listed below. one, two or more epoxy or oxetane moieties; one, two or more glycidyl ether moieties; one, two or more carboxylic acid, carboxy ester, carboxy anhydride, amide or lactam moieties; one, two or more hydroxyphosphate moieties; one, two or more -OH, -SH or -NH moieties; one, two or more silanol, alkoxysilanol, or alkoxysilane moieties; one, two or more isocyanate moieties; and / or One, two or more alkoxy titanate or alkoxy zirconate moieties.

[0020] That is, each combination of these functional groups in a chemical sealant represents an independent embodiment. Additionally, the term "chemical sealant" may refer to one or more chemicals (i.e., a mixture of different chemicals).

[0021] Further embodiments include those in which the surface chemical sealant is further adhered or bonded to another second material. In such cases, the composite structure may be defined in terms of the chemical sealant being disposed between and / or bonded to both the thermoplastic substrate and the second material. For example, in one set of embodiments, the composite structure includes a thermoplastic substrate, a chemical sealant, and an adhesive, paint (primer, intermediate, or topcoat layer), or a surface treatment film layer, where the sealant is disposed between and preferably bonded to the thermoplastic substrate and the adhesive, paint, or surface treatment film layer, and the adhesive, paint, or surface treatment film layer is characterized as having a first surface adjacent to or preferably bonded to the sealant. In some of these embodiments, the adhesive, paint, or surface treatment film layer is applied to the coated surface but is not yet cured. In other embodiments, the adhesive, paint, or surface treatment film layer is cured and bonded to the chemical sealant. When the composite structure includes a surface treatment film, in additional embodiments, the surface of the surface treatment film distal to the surface bonded to the chemical sealant is painted.

[0022] When such composite structures include this second material, the second material may include a thermoplastic or thermoset polymer. Exemplary materials useful for this application include benzoxazine, bismaleimide, epoxy, (meth)acrylate, cyanoacrylate (meth)acrylamide, epoxy acrylate, polyamide, polyester, polyimide, polyurethane, triazine, vinyl ester, or copolymers or mixtures thereof, preferably a (meth)acrylate, epoxy, or polyurethane polymer.

[0023] The adhesive strength of such coatings, particularly paints and adhesives, forms an additional embodiment, for example, when the second material comprises an adhesive or paint, the second material is sufficiently adhered to the composite structure to exhibit a score of at least 3B, 4B, or 5B using the standard 45 degree cross-hatch tape test according to ASTM D3359-09, the conditions of which are more fully described in the examples.

[0024] In a composite structure comprising a surface treatment film bonded to a thermoplastic substrate via a chemical sealant, the thermosetting surface treatment film may be uncured (e.g., when first prepared) or partially cured (e.g., after some post-treatment). The surface treatment film adhered to a thermoplastic substrate or surface has a higher degree of cure than the as-applied surface treatment film.

[0025] In a preferred embodiment, the surface treatment film is an epoxy-based thermosetting surface treatment film. Various types of epoxy-based surface treatment films are described herein.

[0026] As composites themselves, the surface treatment films used or adhered to substrates as disclosed herein, in some embodiments, include one or more organic, inorganic, or metallic additives incorporated into the polymer or prepolymer matrix, such as additives such as flow agents, rheology modifiers, density modifiers, impact modifiers, preservatives, pigments, colorants, and the like.

[0027] Alternatively or additionally, the surface treatment film may include at least one particulate filler or additive, including nano-, micro-, and / or macro-sized powders, particles, beads, flakes, whiskers, or fibers, the morphology of which varies depending on the material and function of the particular material.

[0028] Alternatively or additionally, the surface treatment film may include one or more organic or inorganic fibers, fabrics, woven fabrics, meshes, or porous sheets contained in a thermosetting resin or polymer. In some of these embodiments, the thermosetting surface treatment film includes one or more peelable organic or inorganic fabrics, fabrics, meshes, or porous sheets disposed on or below the second side of the thermosetting surface treatment film.

[0029] Alternatively or additionally, the surface treatment film may include at least one electrically conductive material suitable for use in lightning strike protection, current dissipation, EMI shielding, or heat transfer applications.

[0030] Alternatively or additionally, the surface treatment film is adhered to the thermoplastic substrate with sufficient strength to score at least 3B, 4B, or 5B in a 45° crosshatch tape test in accordance with ASTM D3359-09, conditions which are more fully described in the examples.

[0031] Still other embodiments include those methods of preparing a composite structure. In certain of these, the method comprises: (a) exposing a surface of a thermoplastic substrate to actinic radiation and / or plasma sufficient to activate the surface of the thermoplastic substrate; (b) applying a chemical sealant to the activated surface of the thermoplastic substrate to form a chemically sealed thermoplastic substrate having a surface of the chemical sealant; and (c) optionally, heating the chemically sealed thermoplastic substrate; Includes:

[0032] With reference to the methods, the nature of the substrates, coatings, adhesives, surface treatment films, and methods of activating the bond between them are consistent with the composite structures described elsewhere and will not be repeated here any further. Other aspects of the methods (e.g., pressure and heat treatments) are further described elsewhere herein.

[0033] Yet another aspect of the present disclosure includes those articles that include these disclosed composite structures, including parts or land vehicles such as aircraft and automobiles. [Brief description of the drawings]

[0034] The present application is better understood when read in conjunction with the accompanying drawings. For the purpose of illustrating the subject matter, exemplary embodiments of the subject matter are shown in the drawings. However, the presently disclosed subject matter is not limited to the particular methods, apparatus, and systems disclosed. Additionally, the drawings are not necessarily drawn to scale. The drawings are as follows: [Figure 1]

[0035] FIG. 1 shows the 45 degree cross-hatch scribe and tape positioning for the adhesion testing described herein. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0036] The present disclosure is directed to composite structures comprising thermoplastic substrates that include chemically sealed surfaces, methods for making these composite structures, and articles comprising these composite structures.

[0037] The disclosure presented addresses at least some of the shortcomings of existing methods used in the industry and involves the use of UV and / or plasma activation of thermoplastic surfaces in combination with one or more chemical sealers. As described elsewhere herein, this combination provides unique and unexpected performance advantages in providing a sustainable surface on a thermoplastic substrate that readily accepts paints and adhesives for extended periods of time after treatment. Furthermore, the variety of chemical sealers operable in these methods allows for similar versatility in the use of paints and adhesives.

[0038] In particular, the present disclosure provides composite structures having sealed thermoplastic surfaces that accept and retain paints and adhesives with improved adhesion compared to unsealed surfaces and / or retain surface activation (e.g., by plasma and / or UV activation) longer than unsealed surfaces, such that further coatings of paints and adhesives can be applied and retained with better adhesion to the activated, sealed, aged thermoplastic surface than to a similarly aged and activated thermoplastic surface that is not sealed.

[0039] The present disclosure may be more readily understood by reference to the following description taken in conjunction with the accompanying figures and examples, all of which form a part of this disclosure. It is to be understood that the present disclosure is not limited to the specific products, methods, conditions, or parameters described or shown herein, and that the terms used herein are for the purpose of describing specific embodiments by way of example only, and are not intended to limit the claimed invention. Similarly, unless otherwise specified, descriptions of possible mechanisms or mechanisms of action or reasons for improvements are for illustrative purposes only, and the disclosure herein should not be constrained by the correctness or incorrectness of such proposed mechanisms or mechanisms of action or reasons for improvements. It is recognized that throughout this text, descriptions refer to compositions, and methods of making and using said compositions. That is, when the present disclosure describes or claims features or embodiments related to compositions, and methods of making and using compositions, such descriptions or claims are intended to extend these features or embodiments to the embodiments in each of these contexts (i.e., compositions, methods of making, and methods of using).

[0040] composite structure The present disclosure includes those embodiments of composite structures, which include a thermoplastic substrate directly bonded to a chemical sealant, where the chemical sealant is one or more of the chemical materials described elsewhere herein. Additional embodiments include those in which the composite structure including the chemical sealant is further bonded, directly or otherwise, to one or more of a paint, adhesive, or surface treatment film.

[0041] As used herein, the term "direct bond" and grammatical variations thereof define an interface between a thermoplastic surface of a thermoplastic substrate and a first side of a chemical sealant, where the thermoplastic surface and the first side are adhered to one another at a surface that forms a common interface between the thermoplastic surface and the first side, preferably without any material not provided by the thermoplastic surface and the first side. Similarly, the term "direct bond" may refer to a mechanism whereby the bond is achieved by the presence of an intermediate bonding group (e.g., without an external adhesive or similar composition) by pendant functional groups derived from activation of a polymer portion of the thermoplastic substrate bonding directly to a complementary bonding portion of the chemical sealant.

[0042] The chemical sealant further includes a second side opposite the first side of the chemical sealant, which may optionally be functionalized as described elsewhere herein.

[0043] As described herein, the bond between the thermoplastic substrate and the thermosetting surface treatment film is described as the thermoplastic substrate being directly bonded to the thermosetting surface treatment film.Similarly, the bond can be described as the thermosetting surface treatment film being directly bonded to the thermoplastic substrate, or the thermosetting surface treatment film being directly bonded to the thermoplastic substrate.Such a distinction is merely semantic, and the descriptions should be considered equivalent throughout.

[0044] thermoplastic substrate In the context of this disclosure, a thermoplastic substrate includes a thermoplastic polymer as generally understood by those skilled in the art of polymer chemistry, however, in a preferred embodiment, the thermoplastic substrate includes a thermoplastic polymer typically used in the aerospace industry.

[0045] Even in this context, the thermoplastic polymer of the thermoplastic substrate is broadly defined, but those thermoplastic polymers that contain bonds susceptible to photolytic cleavage upon irradiation with actinic radiation of sufficient intensity appear to be preferred. Such bonds include bonds containing heteroatoms such as -O-, -S-, -C(O)-, -S(O)-, -S(O)2-, -C(O)O-, -C(O)-N-, or combinations thereof. Such thermoplastic polymers include, but are not limited to, as independent embodiments: (a) polyaryletherketones such as polyetheretherketone (PEEK), polyetherketoneketone (PEKK), polyetherketone (PEK), polyetheretherketoneketone (PEEKK), or polyetherketoneetherketoneketone (PEKEKK); (b) a polymer containing a phenyl group bonded directly to a carbonyl group, optionally the carbonyl group being part of an amide group, such as polyacrylamide (PARA); (c) polyphenylene sulfide (PPS); (d) polyphenylene oxide (PPO); or (e) polyetherimide (PEI).

[0046] Each of these polymers may include pendant in addition to linking groups, for example, the term "polyetheretherketone (PEEK)" refers to both substituted (e.g., with alkyl groups) and unsubstituted PEEK polymers.

[0047] As described elsewhere herein, the thermoplastic substrate can also generally be a composite material, where the thermoplastic polymer further comprises organic and / or inorganic additives, such as flow agents, rheology modifiers, density modifiers, preservatives, pigments, colorants, etc. The thermoplastic substrate is typically a structurally reinforced material optionally comprising fibers, meshes, fabrics, or porous sheets contained in a polymer matrix, and is preferably a fiber-reinforced composite material comprising multiple layers of polymer composite material containing oriented fibers (e.g., carbon fibers) or the like arranged in a layered stack such that the fibers of adjacent or alternating layers are oriented transversely to one another.

[0048] When an interface is described as being between "a thermoplastic surface of a thermoplastic substrate and a first side of a thermosetting surface treatment film," the thermoplastic surface is identical or chemically identical to the thermoplastic polymer of the thermoplastic substrate. In this regard, the term "chemically identical" means that the polymer building blocks of the substrate and the polymer building blocks of the surface are substantially identical, even if some of the bonding sites of the surface are altered by photolytic activation.

[0049] Where a thermoplastic polymer is described as containing bonds susceptible to photolytic cleavage upon irradiation with actinic radiation of sufficient intensity, in some embodiments the actinic radiation includes radiation having at least one wavelength in the range of from about 10 nm to about 500 nm or from about 100 nm to about 450 nm, preferably from about 200 nm to about 350 nm. In additional embodiments, the actinic radiation encompasses radiation having one or more wavelengths between about 100 nm and 125 nm, 125 nm and 150 nm, 150 nm and 175 nm, 175 nm and 200 nm, 200 nm and 225 nm, 225 nm and 250 nm, 250 nm and 275 nm, 275 nm and 300 nm, 300 nm and 325 nm, 325 nm and 350 nm, 350 nm and 375 nm, 375 nm and 400 nm, 400 nm and 425 nm, 425 nm and 450 nm, 475 nm and 500 nm, or a range defined by any two or more of the foregoing ranges, such as 300 nm and 400 nm or 275 nm and 325 nm. In other embodiments, actinic radiation includes light or radiation having at least one wavelength characterized as UV-A (about 315-400 nm or 320-390 nm) or UV-B (280-315 nm or 280-320 nm). In other embodiments, actinic radiation includes light or radiation having at least one wavelength characterized as UV-C (about 100-280 nm), UV-V (395-445 nm), near ultraviolet (NUV; 300-400 nm), mid ultraviolet (MUV; 200-300 nm), far ultraviolet (FUV; 122-200 nm), vacuum ultraviolet (VUV; 10-200 nm), or extreme ultraviolet (EUV; 10-120 nm).

[0050] Where thermoplastic polymers are described as containing bonds susceptible to photolytic cleavage upon irradiation with actinic radiation of sufficient intensity, in some embodiments these polymers are capable of cleaving at least about 0.1 J / cm at at least one wavelength. 2 ~About 300J / cm 2 0.5 J / cm2, preferably at at least one wavelength 2 ~About 250J / cm 2 or about 1.5 J / cm 2 ~About 250J / cm 2Additional embodiments include those that are activated by actinic radiation having at least one wavelength in the range of activation energy of 0.1-0.5 J / cm 2 , 0.5~1J / cm 2 , 1~1.5J / cm 2 , 1.5~2J / cm 2 , 2~2.5J / cm 2 , 2.5~3J / cm 2 , 3~3.5J / cm 2 , 3.5~4J / cm 2 , 4~4.5J / cm 2 , 4.5~5J / cm 2 , 5~5.5J / cm 2 , 5.5~6J / cm 2 , 6~6.5J / cm 2 , 6.5~7J / cm 2 , 7~7.5J / cm 2 , 7.5~8J / cm 2 , 8~9J / cm 2 , 9~10J / cm 2 , 10~25J / cm 2 , 25~50J / cm 2 , 50~100J / cm 2 , 100~150J / cm 2 , 150~200J / cm 2 , 200~250J / cm 2 , 250~300J / cm 2 Alternatively, the range may be any two or more of the above ranges, for example, 0.1 to 250 J / cm 2 , or 0.5 to 100 J / cm 2 Simultaneous or sequential illumination with two, three, four or more wavelengths or wavelength ranges is also considered to be a further independent embodiment.

[0051] Chemical sealant In the context of this disclosure, and as described elsewhere herein, the term "chemical sealant" refers to one or more chemical compounds, including mono- or polyfunctional organic, inorganic, or organometallic compounds, which, when bonded to the surface of a thermoplastic substrate, present pendant (such as alkyl, alkenyl, alkynyl, or (hetero)aryl) or heteroatom functional groups that can promote adhesion of a paint, adhesive, or surface treatment film thereto, or that are actually bonded to the paint, adhesive, or surface treatment film, thereby forming a bond (e.g., a covalent chemical bond) between the thermoplastic substrate and the paint, adhesive, or surface treatment film.

[0052] In this way, the chemical sealant can be considered as a tunable adhesion promoter, and by appropriately selecting the chemical sealant, any thermoplastic substrate can be made to adhere to a wide range of potential coatings, adhesives, or surface treatment films. Additionally or alternatively, the chemical sealant may be considered as a bonding agent between the thermoplastic substrate and the potential coatings, adhesives, or surface treatment films. The inventors have discovered that the use of a chemical sealer allows for bonding at lower temperatures, possibly by increasing the number of highly reactive functional groups on the surface, and the formation of new bonds to various coatings or other chemicals can occur at room temperature or slightly higher. These features allow for an expansion of the range of thermoplastic and heat-sensitive materials that can be used in the methods and products of the present invention.

[0053] Additionally, while activated thermoplastic substrates (whether activated by UV light, plasma, or a combination of UV light and plasma) typically remain chemically active for only a short period of time, the use of these chemical sealant composite structures retains this chemical activity for a significantly longer period of time, thereby significantly improving manufacturing options for functionalizing thermoplastic substrates.

[0054] Various examples of such chemicals are described elsewhere herein. While the term "chemical sealant" can be broadly defined, in certain independent embodiments, such chemical sealants can consist of, consist essentially of, or include organic or organometallic compounds having one or more heteroatom-containing functional groups, including: (i) one, two or more epoxy or oxetane moieties; (ii) one, two or more glycidyl ether moieties; (iii) one, two or more carboxylic acid, carboxy ester, carboxy anhydride, amide, or lactam moieties; (iv) one, two or more hydroxyphosphate moieties; (v) one, two or more -OH, -SH or -NH moieties; (vi) one, two or more silanol, alkoxysilanol, or alkoxysilane moieties; (vii) one, two or more isocyanate moieties; and / or (viii) one, two or more alkoxytitanate or alkoxyzirconate moieties.

[0055] Each combination of these functional groups in a chemical sealant represents an independent embodiment. When an organic or organometallic compound has more than one functional moiety per compound, these functional moieties may be the same or different. To allow for a stepwise reaction of the chemical sealant with the thermoplastic substrate, it may be assumed that the two functional moieties per compound are different, or at least have different reactivity in terms of either kinetics or mechanism of action. That is, it is preferred that a given compound contains two different functional moieties, with the first functional moiety preferentially reacting with the activated thermoplastic surface and the second functional moiety remaining unreacted or available for bonding to a second material, such as a paint, adhesive, or surface finish. Thus, in two non-limiting examples, the chemical sealant contains (a) any two or more of the moieties listed in (i)-(viii) above (e.g., an epoxy silane); or (b) one or more of the moieties listed in (i)-(viii) above and one or more alkyl, alkenyl, alkynyl, or (hetero)aryl moieties (e.g., an olefinic hydroxyphosphate).

[0056] The term "chemical sealant" may also refer to one or more chemical substances. The chemical sealant may be applied as a mixture of the chemical sealant compound (or a precursor thereof) with suitable solvents and additives (e.g., viscosity modifiers, fillers, tackifiers, etc.) present to facilitate handling and / or proper finishing.

[0057] In certain independent embodiments, the chemical sealant as a compound consists of, consists essentially of, or includes an organic or organometallic compound having one, two, or more epoxy or oxetane moieties. In independent embodiments, such exemplary epoxies or oxetanes include diglycidyl ethers of bisphenol A, F, S, E, and M resins; epoxy novolacs; glycidyl ethers of monophenols, diphenols, triphenols, and polyphenols; glycidyl ethers of tetraphenolethane; hydroxyl-phenyl-methane-based epoxy resins; naphthalene-based epoxies; triglycidyl ethers of aminophenols; tetraglycidyl ethers of methylene dianiline; glycidyl ethers of aliphatic polyols; cycloaliphatic epoxies; epoxies modified with halogens, silicon, and phosphorus; and epoxies modified with rubbers (such as butadiene, butadiene acrylonitrile copolymers). In a preferred embodiment, the chemical sealant is or includes an organic or organometallic compound having one, two, or more glycidyl ether moieties.

[0058] In certain independent embodiments, the chemical sealant consists of, consists essentially of, or comprises an organic or organometallic compound having one, two or more carboxylic acid, carboxy ester, carboxy anhydride, amide or lactam moieties. Exemplary embodiments within this group include optionally substituted HO2C-R-CO2H, where R is an aliphatic (linear, branched, or cyclic) or aromatic C1-C 24 Monocarboxylic acids (e.g., formic acid, acetic acid, propionic acid, etc., via fatty acids), optionally substituted C2-C 18Monocarboxylic acids, dicarboxylic acids, and polycarboxylic acids, including dicarboxylic acids (e.g., oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, etc., maleic acid, fumaric acid, glutaconic acid, itaconic acid, gluconic acid, citraconic acid, mesaconic acid, itaconic acid, etc.; phthalic acid, isophthalic acid, terephthalic acid, diphenic acid, 2,6-naphthalenedicarboxylic acid) (optionally substituted with one or more hydroxy groups); carboxylic acids; aliphatic and aromatic natural and unnatural amino acids (e.g., alanine, arginine, asparagine, aspartic acid, cysteine, glutamic acid, glutamine, glycine, histidine, isoleucine, leucine, phenylalanine, proline, serine, threonine, tryptophan, tyrosine, and valine); phthalic anhydride, pyromellitic dianhydride, ethylenediaminetetraacetic acid dianhydride, and naphthalenetetraacetic acid dianhydride.

[0059] In certain independent embodiments, the chemical sealant consists of, consists essentially of, or comprises an organic or organometallic compound having one, two or more hydroxyphosphate moieties. Exemplary embodiments within this group include: 1-12 -alkyl dihydrogen phosphates and other mono- and di-alkyl phosphate esters; di-C 1-12 -Alkyl hydrogen phosphate; C 1-12 -Alkyl diphosphate; C 1-12 -Trialkyl phosphate; C 2-12 -Alkenyl dihydrogen phosphate mono- and di-alkenyl phosphate esters; di-C 2-12 Alkenyl hydrogen phosphate;C 2-12 -Alkenyl diphosphate; C 2-12 -trialkenyl phosphate; phytic acid; and phytic acid.

[0060] In certain independent embodiments, the chemical sealant consists of, consists essentially of, or includes organic or organometallic compounds having one, two, or more -OH, -SH, or -NH moieties. Exemplary embodiments within this group include diols, triols, polyols, alkylamines, dialkylamines, alkanolamines, glycolamines, hydroxythiols, dithiols, hydroxyalkylthiols, amine alkylthiols, alkyldithiols; e.g., ethanolamine, propanolamine, dimethylethanolamine, N-methylethanolamine, aminomethylpropanol, optionally alkoxylated or aminated glycerol, optionally alkoxylated or aminated neopentyl glycol, etc.; optionally alkoxylated or aminated trimethylolpropane, optionally alkoxylated or aminated alkanolamines, etc. These include, but are not limited to, cooxylated or aminated pentaerythritol; optionally alkoxylated or aminated sorbitol, maltitol, sorbitol, xylitol, erythritol, isomalt or other sugar alcohols; alkylated or alkoxylated glycolamines; diethylene glycolamine, methoxypolyethylene glycolamine; d-glucamine; hexa(ethylene glycol)dithiol, hexanedithiol, 2,2'-thiodiethanethiol, mercaptoethanol, 2,3-dimercapto-1-propanol, 2-mercaptobenzyl alcohol, cysteamine.

[0061] In certain independent embodiments, the chemical sealant consists of, consists essentially of, or comprises an organic or organometallic compound having one, two or more silanol, alkoxysilanol, or alkoxysilane moieties. Exemplary embodiments within this group are represented by the formula R x Si(OH) 4-x wherein R is independently selected from the group consisting of 1-12 Alkoxy, C 1-12 Alkyl, C 7-18 Aryloxy, C 7-18 Aryl, C 7-18 Alkoxyaryl, C 7-18 Alkarli, C7-18 aralkyl, where x is independently 1, 2, or 3; for example, trimethylsilanol, epoxy silane oligomers, and diphenylsilanediol; and multifunctional silanes including alkoxysilanes containing organic functional groups including epoxy, amine, methacryloxy, acryloxy, ureido, isocyanate, isocyanurate, thiol, including, for example, 3-glycidoxypropyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-ureidopropyltrialkoxysilane, 3-isocyanatopropyltrialkoxysilane, tris-(trimethoxysilylpropyl)isocyanurate, and 3-mercaptopropyltrimethoxysilane.

[0062] In certain independent embodiments, the chemical sealant consists of, consists essentially of, or comprises an organic or organometallic compound having one, two, or more isocyanate moieties.

[0063] In certain independent embodiments, the chemical sealant consists of, consists essentially of, or comprises an organic or organometallic compound having one, two, or more alkoxy titanate or alkoxy zirconate moieties.

[0064] The stacked composite structure further comprises an adhesive, a coating, or a surface treatment film. As described elsewhere herein, the composite structure may include a stacked composite structure of a thermoplastic substrate, a chemical sealant, and an additional material such as an adhesive, a paint (primer, intermediate, or topcoat layer), or a surface treatment film layer, with the sealant disposed and / or adhered between the thermoplastic substrate and the adhesive, paint, primer, or surface treatment film layer. In such an embodiment, the adhesive, paint, or surface treatment film layer is characterized by having a first side bonded to the sealant and a second side opposite the first side. This means that the second side of the adhesive, paint, or surface treatment film layer may be further functionalized by bonding to an additional material (e.g., the second side of the adhesive may be bonded to a third material, the second side of the primer coating may be overcoated with a topcoat paint coating, or the second side of the surface treatment layer may be painted or otherwise functionalized). Further embodiments are provided.

[0065] The chemistry of this adhesive, paint, or surface treatment film layer is flexibly selected depending on the nature of the pendant functional groups of the chemical sealant and may include thermoplastic or thermosetting polymers, or other materials.

[0066] For example, the adhesive, coating, primer, or surface treatment film layer may be described in terms of comprising a benzoxazine, benzoxazine, bismaleimide, epoxy, (meth)acrylate, (meth)acrylamide, cyanoacrylate, (methacryl)acrylamide, epoxy acrylate, polyamide, polyester, polyimide, polyurethane, triazine, vinyl ester, or copolymer or mixture thereof, preferably a (meth)acrylate, epoxy, or polyurethane polymer or copolymer. Particularly useful materials for use as adhesives and coatings include epoxies, (meth)acrylates, (meth)acrylamides, and polyurethanes.

[0067] Composite structures further comprising adhesive, paint, or surface treatment film layers include embodiments in which these materials are applied but not yet cured, and independently, the materials are partially or fully cured. Again, the cured state may be considered to exist as a gradient relative to the applied material. Stated differently, in separate embodiments, the adhesive, paint, or surface treatment film layer may exist independently as provided, or after some steps have been taken or time has elapsed that allow the applied material to further cure (e.g., polymerize or crosslink).

[0068] In this context of composite structures further including adhesive, coating, or surface treatment film layers, these materials may include epoxies.Preferred epoxy resins include, but are not limited to, epoxy resins including one or more of the following: diglycidyl ethers of bisphenol A, F, S, E, and M resins; epoxy novolacs; glycidyl ethers of monohydric, dihydric, trihydric, and polyhydric phenols; glycidyl ethers of tetraphenolethane; hydroxylphenylmethane-based epoxy resins; naphthalene-based epoxy resins; triglycidyl ethers of amino-phenolic resins; tetraglycidyl ethers of methylenedianiline resins; glycidyl ethers of aliphatic polyols; cycloaliphatic epoxy resins; modified grades of all epoxy types (containing halogens, silicon, phosphorus); and toughened grades / additives of all epoxy types using rubber (butadiene, butadiene acrylonitrile copolymer, etc.).

[0069] Within this context of composite structures further comprising adhesives, coatings, or surface treatment film layers, these materials may comprise (meth)acrylics. Suitable (meth)acrylates, including those based on acrylate or methacrylate components, include methyl acrylate, methyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, tetrahydrofurfuryl acrylate, tetrahydrofurfuryl methacrylate, phenoxyethyl acrylate, phenoxyethyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, n-butyl acrylate, n-butyl methacrylate, t-butyl acrylate, t-butyl methacrylate, isobornyl acrylate, isobornyl methacrylate, isooctyl acrylate, isooctyl methacrylate, acrylamide, n-methylacrylamide, lauryl methacrylate and stearyl methacrylate, cyclohexyl methacrylate, hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxyethyl acrylate, hydroxypropyl methacrylate.

[0070] Other suitable acrylates or methacrylates are the polymeric acrylates and methacrylates as shown in Formula I below.

[0071] [ka]

[0072] where R1 is H, halogen, or C1-C 20 may be alkyl, suitably CH3, and R2 may link multiple monomeric acrylates and / or methacrylates; R2 is C1-C 20 Alkyl, C2-C 20 Alkenyl, C3-C 20 Cycloalkyl, C3-C optionally with at least one C-C unsaturated bond in the ring 20 Cycloalkyl, C6-C 20 Aryl, C4-C20 may be selected from the group consisting of heteroaryl, urethane, urea, glycol, ether, polyether or glycidyl moieties, and combinations thereof, optionally substituted one or more times with at least one of hydroxy, amino, halogen, cyano, nitro, C1-C5 alkoxy, and / or C1-C5 thioalkoxy; n can be 1, 2, 3, or 4 acrylate units. Examples include diethylene glycol diacrylate, diethylene glycol dimethacrylate, 1,6-hexanediol diacrylate, 1,6-hexanediol dimethacrylate, neopentyl glycol diacrylate, neopentyl glycol dimethacrylate, polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, triethylene glycol diacrylate, trimethylolpropane trimethacrylate, pentaerythritol triacrylate, pentaerythritol trimethacrylate, tris(2-hydroxyethyl)isocyanurate triacrylate, tris(2-hydroxyethyl)isocyanurate trimethacrylate, tricyclodecane dimethanol diacrylate, tricyclodecane dimethanol dimethacrylate, and ethoxylated bisphenol diacrylates and dimethacrylates.

[0073] Further suitable (meth)acrylates include di- or trifunctional (meth)acrylates such as polyethylene glycol di(meth)acrylate, tetrahydrofuran 10 (meth)acrylate and di(meth)acrylate, hydroxypropyl (meth)acrylate ("HPMA"), hexanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate ("TMPTMA"), diethylene glycol dimethacrylate, triethylene glycol dimethacrylate ("TRIEGMA"), tetraethylene glycol dimethacrylate, dipropylene glycol dimethacrylate, di-(pentamethane)-1,1-dimethylethyl ether (meth)acrylate, di-methyl ... The monomer may be selected from, but is not limited to, polyfunctional (meth)acrylates including bisphenol-mono and di(meth)acrylates such as ethoxylated bisphenol A (meth)acrylate ("EBIPMA"), and bisphenol F mono and di(meth)acrylates such as ethoxylated bisphenol-F (meth)acrylate.

[0074] The acrylate or methacrylate composition may include a curable component, suitably a maleate, fumarate or maleimide component, or a combination thereof. Examples include, but are not limited to, mono-2-(acryloyloxy)ethyl maleate, mono-2-(methacryloyloxy)ethyl maleate, maleic anhydride, maleic acid, toxic acid, fumaric acid, fumaramide, fumaryl nitrile, fumaryl chloride, zinc, calcium and magnesium fumaric acid monoethyl ester salts, 2,5-pyrroledione and 1,1'-(methylenedi-4,1-phenylene)bismaleimide, or a combination thereof.

[0075] The coating or adhesive contemplated by the composite structure may further include a toughening component. Examples of toughening components include synthetic rubbers such as acrylonitrile / butadiene rubber (NBR rubber), polyurethane, styrene / butadiene rubber, styrene / butadiene / methacrylate rubber, chloroprene rubber or butadiene rubber, natural rubber, styrene thermoplastic elastomers such as styrene / polybutadiene / styrene synthetic rubber, polyacrylate or polymethacrylate elastomers, methacrylate / acrylate block copolymers or polystyrene / EPDM (ethylene / propylene / conjugated diene copolymer) synthetic rubber, and olefin thermoplastic elastomers such as polystyrene / EPDM (ethylene / propylene / conjugated diene copolymer) synthetic rubber. Chlorinated and chlorosulfonated polyethylene elastomers can also be used.

[0076] Thermoplastic or thermosetting surface treatment film As described herein, further embodiments include those that include a composite structure that includes a thermoplastic substrate and a thermoplastic or thermosetting surface treatment film that are bonded together by a chemical sealant. The bond between the chemical sealant and the surface treatment film may be physical or chemical in nature. That is, the surface treatment film may simply be placed adjacent to the chemical sealant and held in place manually or by physical interpenetration of defects in the respective surfaces. In embodiments, the bond between these surfaces is more chemical in nature, including by reactive covalent bonds, where functional groups on the activated surface of the thermoplastic resin are presented to the respective bonding portions of the surface-forming film.

[0077] Again, the surface treatment film may comprise a thermoplastic or thermosetting film, but in a preferred embodiment, the surface treatment film is a thermosetting film, and a thermosetting surface treatment film comprises a thermosetting polymer, as is generally understood by those skilled in the art of polymer chemistry. In a preferred embodiment, the thermosetting surface treatment film comprises a (pre)polymer system typically used in this context in the aerospace industry (e.g., benzoxazine, bismaleimide, epoxy, (meth)acrylate, (meth)acrylamide, polyamide, polyimide, polyurethane, vinyl ester, or copolymers or mixtures thereof, preferably a (meth)acrylate, epoxy, or polyurethane polymer or copolymer).

[0078] From the viewpoint of both function / performance and workability, epoxy-based thermosetting surface treatment film seems to be preferred.In this context, in certain embodiments, epoxy-based surface treatment film includes, but is not limited to, epoxy resins including one or more of the following: diglycidyl ether of bisphenol A, F, S, E and M resins; epoxy novolac; glycidyl ether of monohydric, dihydric, trihydric and polyhydric phenols; glycidyl ether of tetraphenol ethane; hydroxylphenylmethane-based epoxy resins; naphthalene-based epoxy resins; triglycidyl ether of amino-phenol resins; tetraglycidyl ether of methylene dianiline resins; glycidyl ether of aliphatic polyols; cycloaliphatic epoxy resins; all epoxy type modified grades (containing halogen, silicon, phosphorus); all epoxy type toughened grades / additions using rubber (butadiene, butadiene acrylonitrile copolymer, etc.). The inventors have seen good results in the method of the present invention with, but not limited to, Loctite® EA9845 Aero, Loctite® EA9845LC, Loctite® EA9845P&P, Loctite® EA9845LC P&P, and Loctite® EA9837.1 epoxy-based composite surface treatment films using PEEK substrates, and these are considered preferred embodiments. In other independent embodiments, Loctite EA9837.1 Aero, Loctite EA9837.1BLK Aero, Loctite EA9837.1LS Aero, Loctite EA9845 Aero, Loctite EA9845LC Aero, Loctite EA9845LA Aero, Loctite EA9845P&P Aero, and Loctite EA9845LC P&P, as well as epoxy-based surfacing films designated as Tencate TC235SF-1, AeroGlide surfacing film, Surface Master 905 from Cytec, and Redux 641 from Hexcel, can also be used in these applications.

[0079] Independent embodiments include those in which the thermosetting surface treatment film is still uncured, partially cured, or fully cured when adhered to the thermoplastic surface, each of these stages of cure may occur at various stages in the process.

[0080] Typically, the thermosetting surface treatment film, when applied, has a total thickness in the range of 12.5 to 12,500 microns (0.5 to 500 mils), preferably 12.5 to 1250 microns (0.5 to 50 mils). In other embodiments, the total thickness is 12.5 to 25 microns, 25 to 50 microns, 50 to 75 microns, 75 to 100 microns, 100 to 125 microns, 125 to 150 microns, 150 to 175 microns, 175 to 200 microns, 200 to 250 microns, 250 to 300 microns, 300 to 400 microns, 400 to 450 microns, 450 to 500 microns, 500 to 1000 microns. The diameter may be expressed as a range of 1000 to 1500 microns, 1500 to 2000 microns, 2000 to 2500 microns, 2500 to 5000 microns, 5000 to 7500 microns, 7500 to 10,000 microns, 10,000 to 12,500 microns, or a combination of two or more of these ranges, for example, 25 to 500 microns, 50 to 300 microns, or about 25 to 125 microns.

[0081] In another embodiment, the thermosetting surface treatment film has a viscosity of 0.005 to 0.15 lb. / ft 2 (psf) or 24g / m 2 ~730g / m 2 Alternatively or additionally, the area weight may be in the range of 25 to 50 g / m 2 , 50~100g / m 2 , 100~200g / m 2 , 200~300g / m 2 , 300~400g / m 2 , 400~500g / m 2 , 500~600g / m 2 , 600~700g / m 2 , or 700~730g / m 2For aircraft applications, the preferred range is 0.005 to 0.01 psf (25 to 50 g / m 2 ), 0.005~0.02psf(25~100g / m 2 ), 0.005~0.03psf(25~150g / m 2 ), 0.005~0.04psf(25~200g / m 2 ), 0.005~0.05psf(25~250g / m 2 ), or 0.005-0.06psf (25-300g / m 2 ), or any combination of two or more of these ranges.

[0082] As with thermoplastic substrates, thermosetting surface treatment films are also composites that contain one or more organic, inorganic, or metallic additives, such as flow agents, rheology modifiers, density modifiers, preservatives, pigments, colorants, etc., incorporated into a thermosetting polymer or prepolymer matrix. In some embodiments, these additives include continuous or chopped fibers, whiskers, nanomaterials, particulate minerals, ceramics, impact modifiers, and / or filled or hollow capsules. At least one particulate filler or additive may contain nano-, micro-, and / or macro-sized powders, particles, beads, flakes, whiskers, or fibers, and at least one particulate filler or additive may include ceramics, polymers, glasses, or metal / semi-metallic materials or alloys thereof, including, for example, aluminum, boron, silicon, tin, zirconium, or aluminum carbides, nitrides, or oxides, carbon, copper, nickel, Sn-Zn, or stainless steel, or aramids, or coated hybrid materials. These fillers may be substantially uniformly distributed throughout the thickness dimension of the surface treatment film or may be concentrated on one of its first or second sides. These particulate fillers may comprise one or more of the functional materials described herein, such as ceramic, polymer, glass, or metal / semi-metallic materials or alloys thereof.

[0083] Alternatively or additionally, such surface treatment films may comprise one or more organic, inorganic, or metallic fibers, meshes, fabrics, or porous sheets contained in a thermosetting resin.

[0084] Such fibers may function as reinforcing fibers including continuous or chopped fibers or whiskers of alumina, aramid, boron, carbon, glass, silicon carbide, or mixtures thereof, with glass and / or carbon fibers being particularly preferred.

[0085] The one or more organic or inorganic fibers, fabrics, woven fabrics, meshes, or porous sheets may be contained in the thermosetting resin or (pre)polymer, or may include one or more peelable organic or inorganic fabrics, fabrics, meshes, or porous sheets disposed on or under the second side of the thermosetting surface treatment film. The use of such peelable materials allows for the subsequent removal of the peelable fabrics, fabrics, meshes, or sheets from the second side opposite the first side of the thermosetting surface treatment film, providing a new surface suitable for subsequent painting. In certain embodiments of the present disclosure, the composite structure is one in which such peelable layers are removed to reveal a paint-ready surface.

[0086] In a further embodiment, the composite structure is a structure in which a paint or other filled or unfilled or clear coat finish is applied to this paint-ready surface, i.e., the second side of the thermosetting surface treatment film is so painted or coated. The choice of paint is not limited, as long as the paint is compatible with the final surface configuration. Preferred paints are those that include polyacrylates, polyesters, polymethacrylates, polyurethanes, or copolymers or mixtures thereof. The bond of the paint to the exposed surface can be physical or chemical, or both, depending on the nature of the paint selected. It is expected that the exposed surface will have a higher concentration of reactive chemical groups attached to the surface as a result of the stripping process than would be the case in the absence of the process described herein. As a result, it is expected that the bond that occurs between the exposed surface and the paint will likely have a higher contribution of chemical interaction with the paint than would be the case in the absence of the process, thereby providing a more integral bond.

[0087] As used herein, the term "fabric" refers to a woven or non-woven material. The term "film" refers to a flat polymer section, consistent with its ordinary meaning. The size of the fabric or film may vary to include sheets, tapes, or continuous rolls. Films may be porous, semi-permeable, or non-porous. Non-porous, apertured films are preferred. Both the fabric and the film may include materials including polyester, polyamide, polyethylene, polypropylene, polyethylene naphthalate (PEN), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyether ether ketone (PEEK), polyamide, polyaryl ether ketone (PAEK), polyethersulfone (PES), polyethyleneimine (PEI), poly(p-phenylene sulfide) (PPS), polyvinyl chloride (PVC), fluorinated or perfluorinated polymers such as polytetrafluoroethylene (PTFE or Teflon), polyvinylidene fluoride (PVDF), polyvinyl fluoride (PVF or Tedlar), or mixtures or copolymers thereof. Preferred exemplary fabrics may include polyester, polyamide, carbon fiber, glass or other inorganic fibers, or Kevlar. Polyester, nylon, or mixtures thereof are particularly useful for fabrics or films for this purpose. Each of the fabrics or films may be coated or impregnated by lamination with an adhesive resin. The resin may be 5-50% or 10-40% by weight of the surface treatment film composition. The polymeric surface of the fabric or film may be optionally coated with silica, siloxane, aluminum oxide or metal, or treated with plasma or silane.

[0088] The fabric or film may be a single layer or multi-layer fabric structure. If the fabric is woven, the woven fabric comprises tightly woven monofilament or multifilament tows. Tightly woven, dense fabrics are preferred to provide a smooth finish that matches the finish desired for the final coating product. Thus, preferred fabrics include plain weave, harness satin weave, crowfoot satin weave, or twill, with crowfoot satin weave styles being most preferred. Polymeric films may be envisioned as the ultimate closed weave and calendared fabric, with polymeric films providing significantly less surface roughness than highly calendared, closed weave fabrics.

[0089] Weave tightness can be described in terms of warp ends and weft ends per inch, both terms being readily understood by those skilled in the art of weaving fabrics. Fabrics or films of the invention include those that independently contain at least 80 warp ends per inch, or at least 100, 120, 140, or 160 warp ends per inch, and at least 40 weft ends per inch, or at least 60, 80, or 100 weft ends per inch. For example, good results are obtained when the fabric or film contains at least about 80 warp ends per inch and at least about 40 weft ends per inch. More preferred embodiments include fabrics woven with at least 120 warp ends per inch and at least 60 weft ends per inch. Such fabrics are commercially available, for example, from Precision Fabrics Group, Greensboro, North Carolina, and are most preferably characterized as providing a "fine surface impression." Exemplary compositions include 60004 / 56111 polyester, 51789 / 52006 nylon, and 2008 / 56115 nylon materials. The fiber or yarn thickness is such that it matches the overall fabric thickness and provides a minimally open weave, taking into account warp end / weft end parameters.

[0090] Alternatively or additionally, the thermosetting surface treatment film may include one or more sheets of a second functional material, at least some of which are in the form of a porous woven or nonwoven fabric, an expanded metal foil or polymer film, a grid, a mesh, a screen or a web. In certain preferred embodiments, these porous sheets of additional functional materials are present in or on the surface treatment film. Thus, the surface treatment film may be optionally monofunctional (e.g., also containing conductive metal filaments or fibers) or multifunctional. Such additional materials include conductive materials suitable for use in lightning protection, current dissipation, EMI shielding, or heat transfer applications.

[0091] That is, in some embodiments, these additional functional materials may be present as multiple sheets of functional material, or a single sheet may include materials with multiple different functions (including so-called hybrid materials). While the peelable porous sheet described above provides one functional capability (i.e., peelability), in the context used herein, the term "functional" refers to attributes of the sheet material that provide several properties (e.g., impact stability, dimensional stability, electrical conductivity, and heat transfer capability) to the film that improve its performance to provide enhanced strength, EMI shielding material, and static and lightning protection to the substrate to which it is ultimately attached. Furthermore, the expression "at least one sheet of a second functional material" may be one or more sheets of a non-peeling functional material, as distinguished from a peelable fabric or sheet. That is, such a second functional material represents an embodiment that includes (a) one sheet of one or more (non-peeling) functional materials, as described below; (b) two or more sheets of the same (non-peeling) functional material; (c) two or more sheets of different (non-peeling) materials; or (d) two or more sheets of two or more (non-peeling) functional materials.

[0092] In addition, the porous sheets of the second functional material may include woven fabrics and expanded films, but may also include nonwoven fabrics, meshes, screens, or webs of continuous or chopped organic or inorganic fibers, including the same or similar materials as those useful for peelable porous sheets, i.e., one or more fluorinated or perfluorinated polymers (such as polytetrafluoroethylene (PTFE or Teflon®), polyvinylidene fluoride (PVDF), polyvinyl fluoride (PVF or Tedlar®), (meth)acrylates, (meth)acrylamides, polyesters, polyamides, polyethylene, polypropylene, polyethylene naphthalate (PEN), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyether ether ketone (PEEK), polyaryl ether ketone (PAEK), polyether sulfone (PES), polyethyleneimine (PEI), poly(p-phenylene sulfide), polyvinyl chloride, or copolymers or mixtures thereof. Other useful organic materials include polyaniline, polypyrrole, polythiophene, or copolymers or mixtures thereof, alone or in admixture with any of the other materials described for this purpose. Aramid (e.g., Kevlar® fiber) and imide fibers (e.g., Kapton®) are also attractive for this application. Because the second functional material is intended to remain in the multifunctional surface treatment film after curing and during end use, the physical integrity or woven nature of these sheets is less important than for peelable materials; i.e., they do not need to survive the peeling operation.

[0093] The functional material may also include ceramic or glass fibers (e.g., oxides, carbides, nitrides, oxycarbides, oxynitrides, carbonitrides, or oxycarbonitrides including aluminum, boron, silicon, and / or titanium), cermet fibers, carbon, metal fibers (e.g., aluminum, copper, iron, silver, tin, zinc, or mixtures, alloys), or coated hybrids including these materials. Exemplary materials include alumina, aramid, boron, carbon, glass, silicon carbide, aluminum nitride, coated hybrids, or mixtures thereof, fibers or whiskers, preferably fibers coated with glass, carbon, or metal. As used herein, the term "fiber" includes those of macro, micro, or nano dimensions, including wires passing through elongated single crystals, also known as whiskers. In some cases, these materials are composites of various material classes, including, for example, carbon-coated metals, glasses, or polymers; metal-coated polymers, carbons, or glasses; polymer-coated glass, carbon, or metals, etc. In some cases, the functional material is electrically conductive. In some embodiments, the functional material imparts magnetic properties to the surface treatment film.

[0094] In a particular embodiment within this more general description, the composite structure includes an adhered thermosetting surface treatment film that is a multi-functional solid composite material that includes two or more of the following: (a) a first peelable cloth, fabric, mesh, or porous sheet disposed on or beneath the second surface; (b) at least one electrically conductive material suitable for use in lightning protection, current dissipation, EMI shielding, or heat transfer applications; (c) at least one particulate filler or additive comprising nano-, micro-, and / or macro-sized powders, particles, beads, flakes, whiskers, or fibers, the at least one particulate filler or additive comprising, for example, aluminum, boron, silicon, tin, zirconium, or carbides, nitrides, or oxides of aluminum, carbon, copper, nickel, Sn-Zn, or stainless steel, or ceramic, polymer, glass, or metal / semi-metallic materials or alloys thereof, including aramid; and, optionally (d) UV resistant polymers or UV stabilizing additives known in the art.

[0095] Physical Properties of Composite Structures The composite structures disclosed herein may also be characterized by one or more of their physical attributes, for example, by the strength of the direct bond of the thermoplastic and thermoset materials.

[0096] For example, in some embodiments, the composite structures are characterized by their wettability both as prepared and after aging. In some embodiments, under the conditions described in Example 3, either as prepared or after 8 months of aging, or both, the sealed surfaces exhibit contact angles with HPLC grade water in the range of 50°-60°, 60°-70°, 70°-80°, or any two or more of the foregoing ranges. In other embodiments, such contact angles after aging are at least 80%, 90%, 95%, or more than the contact angles of the initially prepared samples.

[0097] For example, in some embodiments, a composite structure further comprising an adhesive or coating is characterized by adhesion strength to a thermoplastic substrate via a chemical sealant as measured using a standard cross-hatch tape test, such as the 45° cross-hatch tape test according to ASTM D3359-09. In some of these separate embodiments, the coating or adhesive exhibits a score of at least 3B, 4B, or 5B in the test. Details of this test are described in the Examples.

[0098] In certain other embodiments, the composite structure further comprises an adhesive, and the bond has a strength of at least 100, 200, 300, 400, 500, 600, 700, 800, 900, or 1000 J / m as measured using a double cantilever beam test in accordance with ASTM D5528. 2 to about 1500 J / m 2 Fracture toughness up to G 1C It may be characterized as indicating a value.

[0099] In certain embodiments, the composite structure further comprises a surface treatment film, which is adhered to the thermoplastic substrate with sufficient strength to score at least 3B, 4B, or 5B in a 45° cross-hatch tape test in accordance with ASTM D3359-09, conditions which are more fully described in the examples.

[0100] How to create a composite structure Up to this point, the present disclosure has described composite structures, but the present disclosure also encompasses methods of making these structures. Alternative embodiments include structures derived or derivable from the following methods, even if different from those described with respect to the specifically disclosed composite structures.

[0101] As described herein, the present disclosure includes a method for preparing a directly bonded thermoplastic-thermoset composite material, the method comprising: (a) exposing a surface of a thermoplastic substrate to actinic radiation and / or plasma sufficient to activate the surface of the thermoplastic substrate; (b) applying a chemical sealant to the activated surface of the thermoplastic substrate to form a chemically sealed thermoplastic substrate having a surface of the chemical sealant; and (c) heating the optionally chemically sealed thermoplastic substrate; Includes.

[0102] In some embodiments, the method further includes heating the chemically sealed thermoplastic substrate. In yet other embodiments, the chemical sealant is cured onto the thermoplastic substrate at a temperature ranging from ambient temperature (e.g., 25-25° C.) to 150° C. for a time sufficient to remove volatile solvents from the chemical sealant and / or force a chemical reaction between at least one of the chemical moieties and the activated thermoplastic surface.

[0103] These embodiments include methods of using any of the thermoplastic substrates and surface treatment films described elsewhere herein.

[0104] These embodiments also encompass the use of actinic radiation, as described elsewhere herein. For completeness, they are repeated here in part as encompassing the case where actinic radiation is applied at sufficient intensity at one or more wavelengths in the range of about 10 nm to about 450 nm, preferably in the range of about 200 nm to about 350. Suitable subranges are described elsewhere herein. Similarly, actinic radiation may be applied at a wavelength of about 0.1 J / cm. 2 ~About 300J / cm 2 at least one wavelength with an energy in the range of about 0.5 J / cm 2 ~About 250J / cm 2 or about 1.5 J / cm 2 ~About 250J / cm 2 , or any one or more of the additional embodied ranges described herein, at one or more wavelengths.

[0105] Further, the actinic radiation may be about 2 mW / cm for a time ranging from about 2 to about 600 seconds, or from about 10 to about 60 seconds. 2 ~About 3000mW / cm 2 , about 2 mW / cm 2 ~about 2000mW / cm 2 , about 300mW / cm 2 ~about 600mW / cm 2 or preferably at a rate of about 40 to 500 mW / cm 2In certain other embodiments, the actinic radiation may be applied at a rate ranging from about 2 to about 5 mW / cm. 2 , about 5~10mW / cm 2 , about 10~25mW / cm 2 , about 25~50mW / cm 2 , about 50~100mW / cm 2 , about 100~200mW / cm 2 , about 200~300mW / cm 2 , about 300~400mW / cm 2 , about 400~500mW / cm 2 , about 500~600mW / cm 2 , about 600~700mW / cm 2 , about 700~800mW / cm 2 , about 800~900mW / cm 2 , about 900~1000mW / cm 2 , about 1000~2000mW / cm 2 , about 2000~3000mW / cm 2 In some embodiments, the range is about 2 to 2000 mW / cm. 2 , or preferably about 40 to 500 mW / cm 2 It is.

[0106] The time required to deliver these energies depends on the nature of the substrate and the rate at which the energy is delivered to the substrate. In a continuously moving production line, for example, where successive substrates pass the light source to activate them, faster activation may be desirable. The exposure time may be from about 0.1 seconds to about 360 minutes, for example, from about 0.5 seconds to about 180 minutes, or from about 0.5 seconds to about 30 minutes, or from about 3 seconds to about 19 minutes, or less than about 240 seconds. From the standpoint of throughput, it is preferred that the exposure time is from about 0.1 seconds to about 360 minutes.

[0107] Additionally or alternatively, actinic radiation may be applied at one or more wavelengths, in one or more of the aforementioned ratios, for a time period defined in one or more ranges of about 2 to about 5 seconds, about 5 to about 10 seconds, about 10 to about 20 seconds, about 20 to about 30 seconds, about 30 to about 40 seconds, about 40 to about 60 seconds, about 60 to about 80 seconds, about 80 to about 100 seconds, about 100 to about 200 seconds, about 200 to about 300 seconds, about 300 to about 400 seconds, about 400 to about 500 seconds, about 500 to about 600 seconds, or even longer, up to about 20 minutes, up to about 60 minutes, or up to about 360 minutes.

[0108] The energy required to prepare individual thermoplastic and thermoset bond pairs varies with the nature of the materials being bonded and the time available for such chemical activation. Good results have been achieved and are considered to be generally available following the following procedures: UV-A (320~390nm) - 200mW / cm 2 ×30 seconds=6000mJ / cm 2 =6J / cm 2 UV-B (280~320nm) - 306mW / cm 2 ×30 seconds=9180mJ / cm 2 =9.2J / cm 2 UV-C (100~260nm) - 70mW / cm 2 ×30 seconds=2100mJ / cm 2 =2.1J / cm 2 UV-V (395~445nm - 200mW / cm 2 ×30 seconds=6J / cm 2 The following ranges are suggested to be at least, if not more generally, appropriate, either individually or collectively, for the materials tested: UV-A(320~390nm) - 100~400mW / cm 2 ×10~120 seconds=1~48J / cm 2 UV-B (280~320nm) - 10~300mW / cm 2 ×10~120 seconds=0.1~36J / cm2 UV-C (100~260nm) - 5~200mW / cm 2 ×10~120 seconds=0.5~24J / cm 2 UV-V (395~445nm) - 50~400mW / cm 2 ×10~120 seconds=0.5~48J / cm 2 Illumination using each of these ranges independently is considered a separate embodiment.

[0109] In all aspects of the present invention where actinic radiation is mentioned, the actinic radiation is from a light source that is purposefully and / or specifically positioned to irradiate the substrate to be bonded. In some instances, the light source is within 1 meter of the substrate, for example, within 30 cm of the substrate. For clarity, exposure to actinic radiation from such a source is not intended to encompass, and in some embodiments specifically excludes, the use of ambient light, such as natural light, light from overhead lights, and the like.

[0110] As will be appreciated by those skilled in the art, the gas plasmas used in such applications include energized forms of any number of gases or mixtures of gases, such as air, oxygen, nitrogen, carbon dioxide, energized forms of gas molecules including one or more of atomic oxygen, hydrogen, nitrogen, carbon tetrafluoride, sulfur hexafluoride, argon, helium, and mixtures thereof, which compositions are included in the embodiments of the present disclosure. Plasmas including oxygen (including air) are preferred. These gases are typically excited into plasmas by application of oscillating electric fields having frequencies ranging from very low frequencies, such as 50-60 Hz, to high radio frequencies of 40 KHz to 13.5 MHz, or even microwave frequencies, such as 2-4 GHz. In the present disclosure, the DC is preferably a plasma having a frequency in a range defined by one or more of 1KHz to 5KHz, 5KHz to 10KHz, 10KHz to 15KHz, 15KHz to 20KHz, 20KHz to 25KHz, 25KHz to 30KHz, 30KHz to 35KHz, 35KHz to 40KHz, 40KHz to 45KHz, or 45KHz to 50KHz. In aerospace applications, as contemplated herein, the plasma has a power in the range of 30W to 600W, although in separate embodiments the plasma power can be defined in any 20 or more year increments within this range (i.e., "decade increments" defined as a range of 10W), for example, 50W to 300W or 100W to 600W. The plasma may be impinged on the surface of the substrate under a pressure ranging from 0.13 mbar to 50 bar (0.013 KPa to 5 MPa), although in separate embodiments the range can be defined in any two or more unit millibar increments within this range, for example, from 1 mbar to 1 bar (1000 mbar) or from 1 bar to 5 bar.

[0111] The methods described herein do not require the incorporation of an active agent into the thermoplastic substrate, nor do they require treatments that physically alter the surface to improve adhesion, such as chemical etching (e.g., acid etching), physical abrasion (e.g., sand / grit blasting), or other treatments (e.g., flame).

[0112] Unless otherwise specified, the surface of the thermoplastic substrate may be irradiated and / or plasma treated in some embodiments at above ambient temperatures (e.g., in one or more ranges of 20° C.-25° C., 25° C.-30° C., 30° C.-40° C., 40° C.-50° C., or 50° C.-60° C.) or otherwise at ambient temperatures and conditions. Additionally or alternatively, in separate embodiments, irradiation may be performed in the absence of oxygen, in vacuum conditions, in ambient air, or in an oxygen-rich environment. The surface may be UV irradiated and plasma treated simultaneously or sequentially, or in cycles of both simultaneous and sequential treatment.

[0113] The irradiation and / or plasma treatment may be performed on either the entire surface of the thermoplastic substrate or on patterned portions. For example, these activations may be applied selectively to create areas of the surface that are activated for subsequent bonding and areas of the surface that are not activated for subsequent bonding. A mask can be used that has areas that transmit the actinic radiation / plasma to create areas of the surface that are activated for subsequent bonding areas and areas that block the actinic radiation / plasma to create areas of the surface that are not activated for subsequent bonding. Small or large areas can be treated with a variety of equipment (from spot radiation sources to multiple radiation sources) as needed. Only the areas to be bonded need to be exposed to radiation. When performed in a patterned or spotted manner, the surface treatment film adheres substantially only to those activated areas or substantially more than the non-activated areas.

[0114] Without intending to be bound by the correctness of any particular theory, actinic radiation and / or plasma activates the thermoplastic surface by breaking at least some of these heteroatom bonds, thereby providing activated pendant -OH, -SH, -C(O)H, -C(O)OH, or -C(O)-NH moieties that are capable of forming cross-polymer bonds when reactive groups are presented on the surface treated film.

[0115] After activating the thermoplastic surface, a chemical sealant is applied, optionally with heat and / or pressure, before the surface is allowed to passivate upon standing. Subsequent materials (e.g., adhesives, paints, and surface treatment films) can be applied conventionally. In the case of surface treatment films, once the thermoplastic surface is activated, the surface treatment film is applied with pressure and optionally heat. In certain embodiments, the pressure applied is in the range of about 0.05 MPa to 1.2 MPa, or in one or more ranges of 0.05 MPa to 0.1 MPa, 0.1 MPa to 0.2 MPa, 0.2 MPa to 0.3 MPa, 0.3 MPa to 0.4 MPa, 0.4 MPa to 0.5 MPa, 0.5 MPa to 0.6 MPa, 0.6 MPa to 0.7 MPa, 0.7 MPa to 0.8 MPa, 0.8 MPa to 0.9 MPa, 0.9 MPa to 1.0 MPa, 1.0 MPa to 1.1 MPa, 1.1 MPa to 1.2 MPa, or a combination of two or more of the foregoing ranges, such as one or more pressures of 0.4 MPa to 0.8 MPa or 0.6 MPa to 0.7 MPa. The pressure may be applied for a time period ranging from 30 minutes to 60 minutes, 60 minutes to 90 minutes, 90 minutes to 120 minutes, 120 minutes to 180 minutes, 180 minutes to 240 minutes, or more. In certain embodiments, the composite structure of thermoplastic substrate and thermosetting surface treatment film is heated during this pressure treatment. In other embodiments, no external heat is applied, but if applied, the temperature of the structure is heated to one or more temperatures of 150°C to 160°C, 160°C to 170°C, 170°C to 180°C, 180°C to 190°C, 190°C to 200°C, for example, in the range of 170°C to 180°C. In separate embodiments, heat is applied statically or at an increasing rate as described in the examples, for part or all of the time described.

[0116] After bonding, the bond strength between the thermoplastic substrate and each coating is consistent with the bond metrics described elsewhere herein.

[0117] Articles incorporating these composite structures In addition to the composite structures and methods of making them, the present disclosure contemplates all articles that include these composite structures. Composite structures are suitable for articles of any size, but are particularly attractive for large structures. The contemplated structures include structures that may be one of any one or more of primary structural elements, secondary structural elements, exterior elements, interior elements, and any one or more of commercial and personal aircraft and aerospace applications, automobiles, watercraft (including marine vessels), railroad cars and tankers, and storage tanks.

[0118] That is, aircraft parts that include any of the composite structures described herein are considered within the scope of this disclosure, including, but not limited to, aircraft tails, wings, fuselages, or propellers, and corresponding features of other winged or wingless aircraft or spacecraft.

[0119] Additionally, components of an automobile, bicycle, motorcycle, truck, or land vehicle, such as a watercraft, including any of the composite structures described herein, including, but not limited to, a hood, fender, bumper, hull, or frame, are also considered within the scope of the present disclosure.

[0120] term In this disclosure, the singular forms "a," "an," and "the" include plural references, and a reference to a numerical value includes at least that value unless the context clearly dictates otherwise. Thus, for example, a reference to a "material" is a reference to at least one of such materials and equivalents thereof known to those of skill in the art.

[0121] When values ​​are expressed as approximations using the descriptor "about", it will be understood that the values ​​form another embodiment. In general, the use of the term "about" indicates an approximation that can vary depending on the desired properties sought to be obtained by the disclosed subject matter and should be interpreted in the particular context in which it is used based on its function. Those skilled in the art will be able to interpret this as a matter of routine. In some cases, the number of significant figures used in a value may be one non-limiting way of determining the range of the word "about". In other cases, the incremental changes used in a series of values ​​may be used to determine the intended range that can be used with the term "about" for each value. When present, all ranges are inclusive and combinable. That is, reference to values ​​set forth in a range includes all values ​​within that range.

[0122] For clarity, certain features of the present disclosure described herein in the context of separate embodiments may also be provided in combination in a single embodiment. That is, unless expressly incompatible or specifically excluded, each embodiment is considered to be combinable with other embodiments, and such combinations are separate embodiments. Conversely, for brevity, various features of the present disclosure described in the context of a single embodiment may also be provided separately or in any subcombination. Finally, while an embodiment may be described as part of a series of steps or as part of a more general structure, each of said steps may be considered as an independent embodiment that can be combined with other steps.

[0123] The transitional terms "comprising," "consisting essentially of," and "consisting of" are intended to connote their generally accepted meaning in patent language; that is, (i) "comprising," which is synonymous with "including," "containing," or "characterized by," is inclusive or open-ended and does not exclude additional, unrecited elements or method steps; (ii) "consisting of" excludes elements, steps, or ingredients not specified in the claim; and (iii) "consisting essentially of" limits the scope of the claim to certain materials or steps that "do not materially affect the basic and novel characteristics" of the claimed invention. The embodiments described with respect to the phrase "comprising" (or its equivalent) also provide as embodiments what is described independently with respect to "consisting of" and "consisting essentially of." For those embodiments provided in terms of "consisting essentially of," the basic and novel characteristic is the ready operation of the method or composition / system to provide a composite structure as described herein or related to a particular composition or method step.

[0124] When a list is presented, unless otherwise stated, each individual element of that list, and every combination of that list, is to be understood as a separate embodiment. For example, a list of embodiments presented as "A, B, or C" includes C. 1-3 Similarly, the terms "A", "B", "C", "A or B", "A or C", "B or C", or "A, B, or C" should be construed as including the embodiments "A", "B", "C", "A or B", "A or C", "B or C", or "A, B, or C" as separate embodiments.

[0125] The use of parentheses or brackets to describe materials such as (meth)acrylic or [meth]acrylic or (pre)polymers is intended to imply the presence or absence of the term or phrase enclosed within the parentheses or brackets. For example, the term "(meth)acrylic" refers to either or both acrylic and methacrylic, and the term "(pre)polymer" refers to either or both polymers or prepolymers (the latter including monomers or oligomers or even non-crosslinked polymers depending on the nature of the organic components).

[0126] Throughout this specification, words should be given their ordinary meaning as understood by a person of ordinary skill in the relevant art. However, to avoid any doubt, the meaning of certain terms will be specifically defined or clarified.

[0127] The term "actinic radiation" refers to wavelengths of electromagnetic radiation capable of producing photochemical reactions, including the ability of incident actinic radiation to activate a thermoplastic composition or surface. In various embodiments of the present disclosure, in addition to the specific ranges described elsewhere herein, the term "actinic radiation" also encompasses light or radiation having at least one wavelength characterized as UV-A (approximately 315-400 nm or 320-390 nm) and UV-B (280-315 nm or 280-320 nm). In other embodiments, actinic radiation encompasses light or radiation having at least one wavelength characterized as UV-C (approximately 100-280 nm), UV-V (395-445 nm), near ultraviolet (NUV; 300-400 nm), mid ultraviolet (MUV; 200-300 nm), far ultraviolet (FUV; 122-200 nm), vacuum ultraviolet (VUV; 10-200 nm), or extreme ultraviolet (EUV; 10-120 nm).

[0128] In the context of this disclosure, the term "carboxylic acid moiety" refers to a pendant carboxylic acid, -C(O)OH group. Similarly, the terms carboxy ester, carboxy anhydride, amide, or lactam moiety each refer to the corresponding functional groups, i.e., -C(O)OR, -C(O)-OC(O)-R, -C(O)N(R')2, respectively, where R is alkyl or aryl and R' is independently H, alkyl, or aryl.

[0129] In the context of this disclosure, the term "composite structure" refers to a layered structure resulting from direct bonding between a thermoplastic substrate and a thermosetting surface treatment film. It is recognized that both the thermoplastic substrate and the thermosetting surface treatment film itself may also be considered composites in the true sense of the term (i.e., a polymer or prepolymer matrix containing additives, fillers, fibers, etc.). When the term "composite" is used throughout in these contexts, they are referred to herein as either composite thermoplastic substrates or composite surface treatment films.

[0130] The term "chemical sealant" as used herein refers to one or more chemicals, including mono-, di-, or polyfunctional organic, inorganic, or organometallic compounds, that upon adhering to the surface of a thermoplastic substrate, exhibit pendant (such as alkyl or aryl) or functional groups that can promote adhesion of a coating, adhesive, or surface treatment film thereto, or that actually bond to the coating, adhesive, or surface treatment film, thereby forming a bond (e.g., a covalent chemical bond) between the thermoplastic substrate and the coating, adhesive, or surface treatment film. Various examples of such chemicals are described elsewhere herein.

[0131] As conventionally understood, the term "cured" refers to a chemical process that results in the toughening or hardening of a polymeric material by cross-linking of polymer chains. It is strongly associated with the manufacture of thermoset polymers. Curing can be by the effect of heat, radiation, electron beam, or chemical additives. As used herein, the term "partially cured" refers to any increase in the degree of cross-linking compared to that of the original polymer or prepolymeric material.

[0132] "Optional" or "optionally" means that the subsequently described circumstance may or may not occur, so that the description encompasses cases where the circumstance occurs and cases where it does not occur.

[0133] The terms "method" and "process" are considered interchangeable within this disclosure.

[0134] The terms "photolysis," "photolytic," and the like refer to the controlled activation of a thermoplastic surface by the use of UV light, during which certain chemical bonds, typically those involving heteroatoms, are broken, thereby generating functional groups that make the surface more chemically active than an untreated surface. These more chemically active functional groups are capable of bonding or bond with a thermosetting surface treatment film during cure of the surface treatment film.

[0135] The term "plasma" as used herein refers to an energized gas phase, typically containing ionized atoms or molecules, more typically oxygen atoms or molecules. Plasma typically contains energized atoms, molecules, ions, electrons, free radicals, and photons in the short wave ultraviolet (vacuum UV, or VUV for short) range that can interact with thermoplastic surfaces. When the gas used is oxygen, plasma can be used to break certain chemical bonds to clean the surface of a substrate (in this case a thermoplastic substrate) as well as activate the surface through further treatments as described herein. Additional explanation of this term is provided elsewhere herein.

[0136] As used herein, the term "resin" has its conventional meaning of a liquid, typically viscous or highly viscous material that is converted to a solid material upon curing.

[0137] The term "surface treatment film" refers to a composite material in solid form, well known in the field of aerospace engineering, typically having an areal weight of less than 0.150 pounds per square foot and a total thickness ranging from 25 to 12,500 microns (1 to 500 mils). They are typically applied to the substrate surface of an aircraft to provide the surface quality required for aerospace applications. In some embodiments, reference to a surface treatment film refers to such a composite material in which one or more organic, inorganic, or metallic additives, such as flow agents, rheology modifiers, density modifiers, preservatives, pigments, colorants, and the like, are incorporated into a polymer or prepolymer matrix. In other embodiments, the surface treatment film may additionally or instead include one or more organic, inorganic, or metallic fibers, meshes, fabrics, or porous sheets contained in a thermosetting resin. In an epoxy-based thermosetting surface treatment film, the thermosetting resin includes an epoxy-based resin. The surface treatment film may optionally be monofunctional (e.g., containing conductive metal filaments or fibers) or multifunctional (as in previous applications).

[0138] As used herein, the term "thermoplastic" refers to a plastic polymeric material that becomes flexible or moldable at a certain elevated temperature and solidifies upon cooling. Thermoplastics contemplated within this disclosure, such as those used in aerospace applications, typically undergo such transformation at elevated temperatures. Specific types of materials encompassed by this label are disclosed elsewhere herein and include, but are not limited to, polymers of (meth)acrylic, acrylonitrile (including acrylonitrile butadiene styrene), ethylene vinyl alcohol (EVOH), ethylene vinyl acetate (EVA), polyamide, polyamideimide (PAI, polyaryletherketone (PAEK), polybenzimidazole, polycarbonate, polylactic acid (polylactide), polyethersulfone, polyoxymethylene (also known as acetal), polyetheretherketone, polyetherimide, polyetheretherketone (PEEK), polyetherimide (PEI), polyetherketoneketone (PEKK), polyethersulfone (PES), polyethylene, polyhydroxyalkanoate polyimide, polyketone, polyphenylene oxide, polyphenylene sulfide, polysulfone, polypropylene, polystyrene, polytetrafluoroethylene, polyurethane, polyvinyl chloride, and polyvinylidene fluoride.

[0139] The terms "thermosetting" or "thermosettable" are used herein in the conventional sense to refer to polymers or prepolymers or resins that irreversibly harden during cure by a crosslinked network (i.e., "thermoset"). Crosslinked (meth)acrylic, (meth)acrylamide, benzoxazine, bismaleimide, epoxy, polyamide, polyimide, polyurethane, vinyl ester, phenolic, amino and furan resins, or copolymers or mixtures thereof, are non-limiting examples of these types of materials.

[0140] As a common practice in the industry, either the term "thermoset" or "thermoset(ting)" may be used broadly to describe the properties of a polymer or surface treatment film, regardless of the degree of cure. The term "thermoset(ting)" encompasses both partially or fully cured (thermoset) materials, and uncured or less cured (thermosetting or thermosettable) materials. Obviously, the degree of cure is a spectrum for any material, but one of ordinary skill in the art will be able to distinguish the meaning of these terms in the context of their use.

[0141] A "thermosetting or thermosettable surface treatment film" or "thermoset(ting) film" is a solid composite material that includes the cited polymer or prepolymer, respectively. Such surface treatment films include a polymer and / or prepolymer and one or more organic, inorganic, or metallic additives, such as flow agents, rheology modifiers, density modifiers, preservatives, pigments, colorants, etc., that are incorporated into the polymer or prepolymer matrix. These surface treatment films may also optionally include one or more organic, inorganic, or metallic fibers, meshes, fabrics, or porous sheets contained within or on one surface of the polymer or prepolymer matrix. In epoxy-based thermosetting surface treatment films, the thermosetting resin includes an epoxy-based resin. The surface treatment film may optionally be monofunctional (e.g., containing conductive metal filaments or fibers) or multifunctional (as described elsewhere herein). It should be understood that the terms "thermosetting or thermosettable surface treatment film" and "thermoset surface treatment film" refer to surface treatment film compositions with different degrees of cure. For clarity, these terms should be considered in the context in which they occur.

[0142] The following list of embodiments is intended to supplement, not replace or replace, the previous description.

[0143] EMBODIMENT 1 A composite structure comprising a thermoplastic substrate having a chemical sealant directly bonded to a surface thereof, in certain aspects of this embodiment, the direct bond defines an interface between the thermoplastic surface of the thermoplastic substrate and a first side of the chemical sealant coating layer, and the chemical sealant coating layer further comprises a second side opposite the first side of the chemical sealant coating layer.

[0144] Unless otherwise specified, the thermoplastic surface is identical or chemically identical to the thermoplastic substrate. The term "chemically identical" means that the polymer building blocks of the substrate and the polymer building blocks of the surface are identical, even if some of the bonding sites of the surface are altered by photolytic activation.

[0145] In some aspects of this embodiment, the composite structure exhibits wettability both as prepared and after aging, as described elsewhere herein. For example, in some aspects, the sealed surface exhibits a contact angle with HPLC grade water in the range of 50°-80° either as prepared or after 8 months of aging, or both, and / or such aged contact angle is at least 80% of the contact angle of the initially prepared sample. Additional aspects of these ranges are described elsewhere herein.

[0146] EMBODIMENT 2 the thermoplastic substrate independently comprising: (a) polyaryletherketones such as polyetheretherketone (PEEK), polyetherketoneketone (PEKK), polyetherketone (PEK), polyetheretherketoneketone (PEEKK), or polyetherketoneetherketoneketone (PEKEKK); (b) a polymer containing a phenyl group bonded directly to a carbonyl group, optionally the carbonyl group being part of an amide group, such as polyacrylamide (PARA); (c) polyphenylene sulfide (PPS); (d) polyphenylene oxide (PPO); or (e) The composite structure of embodiment 1, comprising polyetherimide (PEI).

[0147] EMBODIMENT 3 3. The composite structure of embodiment 1 or 2, wherein the thermoplastic substrate comprises a thermoplastic polymer whose bonds are susceptible to at least partial photolytic scission upon exposure to actinic radiation of sufficient intensity, and the actinic radiation includes radiation having at least one wavelength in the range of about 10 nm to about 500 nm or about 100 nm to about 450 nm, preferably in the range of about 200 nm to about 350 nm. Additional aspects of this embodiment include subranges of these ranges described elsewhere herein.

[0148] EMBODIMENT 4 The thermoplastic substrate has a bond of about 0.1 J / cm at at least one wavelength. 2 ~About 300J / cm 2 0.5 J / cm2 at least one wavelength, preferably in the range of about 0.5 J / cm2 2 ~About 250J / cm 2 or about 1.5 J / cm 2 ~About 250J / cm 2 The composite structure of any of embodiments 1-3, comprising a thermoplastic polymer that is susceptible to at least partial photolytic cleavage upon exposure to at least one wavelength (optionally 1, 2, 3, or 4 wavelengths) of actinic radiation with energies in the range of 0.1 to 0.5 nm. Additional aspects of this embodiment include subranges of these ranges as described elsewhere herein.

[0149] EMBODIMENT 5 5. The composite structure of any of embodiments 1-4, wherein the chemical sealant bonds directly to the patterned portion of the thermoplastic substrate. Independent examples of this chemical group are described elsewhere herein.

[0150] EMBODIMENT 6 The composite structure of any of embodiments 1-5, wherein the chemical sealant is or comprises an organic or organometallic compound having one, two or more epoxy or oxetane moieties, independent examples of which chemical groups are described elsewhere herein.

[0151] EMBODIMENT 7 The composite structure of any of embodiments 1-6, wherein the chemical sealant is or comprises an organic or organometallic compound having one, two or more glycidyl ether moieties. Independent examples of this chemical group are described elsewhere herein.

[0152] EMBODIMENT 8 The composite structure of any of embodiments 1-7, wherein the chemical sealant is or comprises an organic or organometallic compound having one, two or more carboxylic acid, carboxy ester, carboxy anhydride, amide or lactam moieties. Independent examples of this chemical group are described elsewhere herein.

[0153] EMBODIMENT 9 The composite structure of any of embodiments 1-8, wherein the chemical sealant is or comprises an organic or organometallic compound having one, two or more hydroxyphosphate moieties, independent examples of which chemical groups are described elsewhere herein.

[0154] EMBODIMENT 10 The composite structure of any of embodiments 1-9, wherein the chemical sealant is or comprises an organic or organometallic compound having one, two or more -OH, -SH or -NH moieties. Independent examples of this chemical group are described elsewhere herein.

[0155] EMBODIMENT 11 The composite structure of any of embodiments 1-10, wherein the chemical sealant is or comprises an organic or organometallic compound having one, two or more silanol, alkoxysilanol or alkoxysilane moieties, independent examples of which chemical groups are described elsewhere herein.

[0156] EMBODIMENT 12 12. The composite structure of any of embodiments 1-11, wherein the chemical sealant is or comprises an organic or organometallic compound having one, two or more isocyanate moieties. Independent examples of this chemical group are described elsewhere herein.

[0157] EMBODIMENT 13 13. The composite structure of any of embodiments 1-12, wherein the chemical sealant is or comprises an organic or organometallic compound having one, two or more alkoxy titanate or alkoxy zirconate moieties, independent examples of which chemical groups are described elsewhere herein.

[0158] EMBODIMENT 14 14. The composite structure of any of the preceding claims, further comprising an adhesive, paint (primer, intermediate, or topcoat layer), or surface-treated film layer, wherein the sealant is disposed between and bonds the thermoplastic substrate and the adhesive, paint, or surface-treated film layer, and wherein the adhesive, paint, or surface-treated film layer has a first surface bonded to the sealant and a second surface opposite the first surface.

[0159] EMBODIMENT 15 15. The composite structure of embodiment 14, wherein the adhesive, paint or surface treatment film layer comprises a thermoplastic or thermoset polymer.

[0160] EMBODIMENT 16 16. The composite structure of any of embodiments 14 or 15, wherein the adhesive, coating, primer, or surface treatment film layer comprises a benzoxazine, bismaleimide, cyanoacrylate, epoxy, epoxyacrylate, (meth)acrylate, (meth)acrylamide, polyamide, polyester, polyimide, polyurethane, triazine, vinyl ester, or copolymers or mixtures thereof, preferably a (meth)acrylate, epoxy, or polyurethane polymer.

[0161] EMBODIMENT 17 17. The composite structure of any of embodiments 14-16, wherein the adhesive, paint, or surface treatment film layer is applied but not cured (i.e., not crosslinked) or not solidified (where the paint does not crosslink but is still an intact film).

[0162] EMBODIMENT 18 17. The composite structure of any of embodiments 14-16, wherein the adhesive, paint, or surface treatment film layer is cured or fully solidified.

[0163] EMBODIMENT 19 19. The composite structure of any of embodiments 14-18, wherein the adhesive or coating is sufficiently adherent to the composite structure to exhibit a score of at least 3B, 4B, or 5B in a 45° cross-hatch tape test in accordance with ASTM D3359-09, the conditions of which are more fully described in the examples.

[0164] EMBODIMENT 20 19. The composite structure of any of embodiments 14-18, wherein the thermosetting surface treatment film is an epoxy-based thermosetting surface treatment film.

[0165] EMBODIMENT 21 21. The composite structure of any of embodiments 14-18 or 20, wherein the surface treatment film itself is a solid composite material comprising one or more organic or inorganic fibers, cloths, fabrics, meshes, or porous sheets within a thermoplastic or thermosetting polymer.

[0166] EMBODIMENT 22 22. The composite structure of any of embodiments 14-18, 20 or 21, wherein the surface treatment film is a solid composite material comprising one or more peelable organic or inorganic cloths, fabrics, meshes, or porous sheets disposed on or under the second surface of the surface treatment film.

[0167] EMBODIMENT 23 23. The composite structure of any of embodiments 14-18 or 20-22, wherein the surface treatment film is a solid composite material comprising one or more organic or inorganic cloths, fabrics, meshes, or porous sheets contained within a thermosetting resin, and further comprising at least one conductive material suitable for use in lightning strike protection, current dissipation, EMI shielding, or heat transfer applications.

[0168] EMBODIMENT 24 24. The composite structure of any of embodiments 14-18 or 20-23, wherein the surface treatment film is a solid composite material comprising one or more organic or inorganic cloths, fabrics, meshes, or porous sheets, and further comprises at least one particulate material suitable for use as an impact modifier contained within a thermoplastic or thermosetting polymer.

[0169] EMBODIMENT 25 25. The composite structure of any of embodiments 14-18 or 20-24, wherein the surface treatment film adheres to the thermoplastic substrate with sufficient strength to exhibit a score of at least 3B, 4B, or 5B in a 45° crosshatch tape test according to ASTM D3359-09, the conditions of which are more fully described in the examples.

[0170] EMBODIMENT 26 25. The composite structure of any of embodiments 14-18 or 20-24, wherein the second side of the surface treatment film is coated with paint.

[0171] EMBODIMENT 27 (a) exposing a surface of a thermoplastic substrate to actinic radiation and / or plasma sufficient to activate the surface of said thermoplastic substrate; (b) applying a chemical sealant to the activated surface of the thermoplastic substrate to form a chemically sealed and activated thermoplastic substrate having a surface of the chemical sealant; and (c) optionally, heating the chemically sealed thermoplastic substrate; A method for manufacturing a composite structure comprising:

[0172] In certain independent aspects of this embodiment, irradiation is carried out at ambient or super-ambient temperatures and conditions, in the absence of oxygen, under vacuum conditions, in ambient air, or in an oxygen-rich environment, as described elsewhere herein.

[0173] In certain independent aspects of this embodiment, the irradiation or plasma treatment is carried out under any one or more of the conditions described elsewhere herein.

[0174] EMBODIMENT 28 28. The method of embodiment 27, further comprising heating the chemically sealed thermoplastic substrate.

[0175] EMBODIMENT 29 The thermoplastic substrate comprising: (a) polyaryletherketones such as polyetheretherketone (PEEK), polyetherketoneketone (PEKK), polyetherketone (PEK), polyetheretherketoneketone (PEEKK), or polyetherketoneetherketoneketone (PEKEKK); (b) a polymer containing a phenyl group bonded directly to a carbonyl group, optionally the carbonyl group being part of an amide group, such as polyacrylamide (PARA); (c) polyphenylene sulfide (PPS); (d) polyphenylene oxide (PPO); or (e) polyetherimide (PEI); 29. The method of embodiment 27 or 28, comprising:

[0176] EMBODIMENT 30 30. The method of any of embodiments 27-29, wherein the surface treatment film is an epoxy-based thermosetting or thermosettable surface treatment film, and the corresponding thermosetting surface treatment film is an epoxy-based thermosetting surface treatment film.

[0177] EMBODIMENT 31 The method of any of embodiments 27-30, wherein the actinic radiation is applied at one or more wavelengths in the range of about 10 nm to about 450 nm, preferably in the range of about 200 nm to about 350 nm, and at sufficient intensity. Additional aspects of this embodiment include subranges of these ranges as described elsewhere herein.

[0178] EMBODIMENT 32 The actinic radiation is about 0.5 J / cm at at least one wavelength. 2 ~About 300J / cm 2 0.5 J / cm2 at least at one wavelength. 2 ~About 250J / cm 2 or about 1.5 J / cm 2 ~About 250J / cm 2 The method of any of embodiments 27-31, wherein the actinic radiation is applied at one or more wavelengths with an energy in the range of 100 to 200 nm. Additional aspects of this embodiment include subranges of these ranges as described elsewhere herein. Similarly, additional aspects of this embodiment include rates and times of application of actinic radiation as described and described elsewhere herein.

[0179] EMBODIMENT 33 33. The method of any of embodiments 27-32, further comprising applying an adhesive, a coating (primer, intermediate, or topcoat layer), or a surface treatment film layer to the second side of the chemical sealant.

[0180] EMBODIMENT 34 34. The method of embodiment 33, further comprising curing or fusing said adhesive, coating (primer, intermediate, or topcoat layer), or surface treatment film layer.

[0181] EMBODIMENT 35 The method of any of embodiments 27-34, wherein the adhesive, coating, or surface treatment film adheres to the thermoplastic substrate with sufficient strength to exhibit a score of at least 3B, 4B, or 5B in a 45° cross-hatch tape test in accordance with ASTM D3359-09, conditions which are more fully described in the examples. Alternatively or additionally, the composite structure further comprises an adhesive, and the bond exhibits a strength of at least 100, 200, 300, 400, 500, 600, 700, 800, 900, or 1000 J / m2 as measured using a double cantilever beam test in accordance with ASTM D5528. 2 to about 1500 J / m 2 Fracture toughness up to G 1C It may be characterized as indicating value.

[0182] EMBODIMENT 36 A composite structure prepared by the method of any one of embodiments 27 to 35.

[0183] EMBODIMENT 37 An aircraft or aerospace vehicle part comprising the composite structure of any of embodiments 1 to 26. In certain aspects of this embodiment, the aircraft part comprises an aircraft empennage, wing, fuselage, or propeller.

[0184] EMBODIMENT 38 A part or portion of a land vehicle, such as an automobile, bicycle, motorcycle, truck, or personal watercraft, comprising the composite structure of any of embodiments 1-26. In certain aspects of this embodiment, the part comprises a hood, a fender, a bumper, a hull, or a frame. EXAMPLES

[0185] Standard application conditions

[0186] Under standard test conditions, the surface of the thermoplastic substrate was cleaned to remove dust using an isopropanol wipe, and after cleaning, where so indicated, the surface of the thermoplastic substrate was either irradiated with UV light using a UVALOC1000 light source fitted with a mercury D-type bulb (iron doped) for the indicated time and energy, or plasma treated.

[0187] Where paint or adhesive was applied, it was applied using conventional methods (spray, brush, etc.).

[0188] After the surface treatment film was applied, it was laminated onto the thermoplastic surface and the assembly was consolidated in a standard vacuum bag / autoclave process according to the following procedure. (1) After wiping and cleaning the aluminum caul plate with acetone, a release agent was applied to all areas except the edges of the plate. (2) The edges of the plate were lined with vacuum putty. (3) The test specimen was first prepared by placing a single-sided adhesive (OST) surface treatment film, adhesive side first, onto the thermoplastic substrate to pre-position the part / specimen, and then the specimen was placed inside the edge of the caul plate using an arrangement of film material (nylon film), specimen, perforated Teflon film, and breather cloth. (4) A vacuum line vent was placed on the plate and the entire assembly was covered with nylon film. The nylon film was pressed into the putty to seal. A vacuum was applied to test the quality of the seal. (5) The entire bagged plate was placed in the autoclave. (6) The test specimens were cured under the following conditions: temperature 177°C, ramp rate 1.7°C / min, pressure 0.31 MPa, and time 120 min. After this integration, the assembly was disassembled, visually inspected, and tested for adhesion.

[0189] Standard Test Conditions The adhesive performance was evaluated by the crosshatch test method. The test was carried out as follows. (1) Test specimens were scribed with a cutting tool as shown in Figure 1, which cut through the coating (surface treatment film) to the substrate. The cutting tool can be a sharp razor blade, scalpel, or knife. In this test, a 45 degree cross-hatch scribe was made, with the angle between the two sets of parallel scribes being 45±5 degrees, and the parallel scribes being approximately 3.05 mm apart. (2) Masking tape (3M tape number 250) was applied as shown in Figure 1. The tape was pressed firmly using the roll of tape itself. (3) One minute after applying the tape to the panel, the tape was removed in one quick motion and pulled perpendicular to the panel. (4) The test areas were visually inspected and rated according to ASTM D3359-09. Crosshatch ratings range from 0B to 5B, with 0B being the worst condition, with greater than 65% area removed. The rating classifications are summarized in Table A.

[0190] [Table 1]

[0191] Pretreatment of Thermoplastic Substrates - General Procedure: Unless otherwise specified, standard conditions are to wipe the surface of the thermoplastic substrate with an isopropanol wipe to remove dust. After cleaning, if so indicated, the surface of the thermoplastic substrate was irradiated with UV light using a UVALOC1000 light source fitted with a mercury D-type bulb (iron doped) for a given period of time. Exposure times are typically 0.1 J / cm2 at wavelengths ranging from about 200 nm to about 400 nm. 2 ~About 300J / cm 2 The experiments involved exposing the samples to UV light for times ranging from 10 to 60 seconds, with energies ranging from 100 to 200 s.

[0192] Where so indicated, plasma activation typically involves application of a DC-Arc dry air plasma with a frequency of 21 KHz, plasma power of 400 W, and gas pressure of 3.5 bar (350 KPa). Plasma traverse speed was 2.5 mm / sec to 25 mm / sec. Plasma parameters were as follows: nozzle: 14 degrees, distance: 8 to 12.7 mm, pressure 3.5 to 50 psi.

[0193] After activation, the activated surface was treated with a chemical sealer, preferably by spraying, although other application techniques such as wiping, brushing, and dipping have also been used. Curing of the sealer was carried out at room temperature and / or elevated temperature, depending on the sealer chemistry.

[0194] Materials used in the examples Thermoplastic substrate: The thermoplastic substrate used in these examples was a thermoplastic integral laminate (TPCL) made from several layers of woven powdered thermoplastic fabric. The powdered fabric consisted of high toughness carbon fibre (Tenax-E HTA40 E13 3K 200tex) and a PEEK matrix (42wt%). The fabric had an areal weight of 285g / m 2 It had a 5-harness pattern with a total panel thickness of 1.5 mm.

[0195] Epoxy-based paint primer: The primer used in the examples was a chrome-free epoxy primer paint designed for application to composite aircraft surfaces in the aerospace industry. It is a solvent-based product, compatible with polyurethane topcoats and epoxy primers, has a working temperature range of -54°C to 177°C, and cures in 7 days at room temperature (25°C).

[0196] Silane-Based Sealer: The Silane-Based Sealer was a silane-based organometallic, chrome-free, water-based product based on sol-gel technology. It is a two-part system and is + It contains a catalyzed, alkoxysilane epoxy component and cures at room temperature and at temperatures as high as 177° C. A variety of application methods were used including spray, brush and wipe.

[0197] Chrome-Free Epoxy-Based Sealers: Chrome-free epoxy-based products are two-part water-based systems with reactants in each part that can be combined to form a sealer. Curing is a high temperature cure (120 and 177°C).

[0198] Loctite EA9696 Aero: This material is an epoxy film adhesive containing a pre-catalyzed epoxy resin that is cast into a film and contains a modified epoxy resin designed for high toughness and use temperatures up to 121°C. The film is reticulated. It cures at 107-129°C.

[0199] Coating Activated Thermoplastic Substrates - General Procedure Coatings were typically sprayed onto chemically sealed surfaces, although other methods (brushing or rolling) were also used. After application, coatings were allowed to cure at room temperature for several hours to several days. Elevated cure temperatures of 150 and 200°F were used for approximately 30 to 60 minutes. Adhesion was tested using the cross-hatch test method.

[0200] Bonding Adhesives to Thermoplastic Substrates - General Procedure: The adhesive was typically sprayed onto a chemically sealed surface, although other methods (brushing or rolling) have also been used. Adhesive performance was evaluated with multiple test methods including a floating roller peel test and potentially a G1C double cantilever beam (fracture toughness) test.

[0201] The surface treatment film was physically laminated onto the chemically sealed surface and a vacuum heat treatment was used to bond the surface treatment film to the chemically sealed thermoplastic substrate. Adhesion was tested using the crosshatch test method.

[0202] Example 1: Effect of chemical sealers on increasing adhesion between thermoplastic substrates and adhesives Example 1.1: Scope: Sealer + Adhesive: Fracture toughness (G 1CThe G-value measurement is one of the standard tests to evaluate the adhesion between an adhesive and a substrate. It was found that when bonding a thermosetting substrate to a thermoplastic PEEK substrate using several adhesives at a specific cure temperature, the adhesion decreased both with UV activation (87.56) and without UV activation (52.53) of the PEEK panel. The poor adhesion to PEEK was due to the G 1C In contrast, the use of a chemical silane-based sealer applied after UV activation of the PEEK substrate resulted in dramatically higher G 1C (1085.75), indicating a significant improvement in adhesion to the PEEK side.

[0203] Example 1.2: General application procedure The thermoplastic composite substrate Tenax-ETPCL PEEK-HTA40 was tested for bonding to epoxy-based thermoset composite skins with and without UV activation and with and without chemical sealants. Adhesion was measured using double cantilever beam (DCB) testing according to ASTM D5528 to determine fracture toughness energy (G 1C The specimens were prepared by co-bonding a thermoplastic substrate to a thermoset prepreg according to the following procedure.

[0204] First, the substrate was washed twice with IPA (isopropyl alcohol) and dried for 10 minutes after each wipe. The washed substrate was then optionally exposed to a 290 mW / cm 2 The adhesive was activated by UV irradiation at 40°C for 30 seconds. A chemical silane-based organometallic sealer was then applied. The silane sealer was applied by wiping for 1 minute to wet the surface and then drying it for 1 hour. Curing was then carried out at room temperature for 1 hour. In the fourth step, consolidation was carried out using the standard vacuum bag / autoclave process described above. In the fifth step, the adhesive performance was evaluated with a double cantilever beam test according to ASTM D5528.

[0205] Example 1.3: Results Sample 1.1: A non-UV activated thermoplastic substrate and silane sealer were co-bonded to a carbon fiber reinforced epoxy skin following typical application procedures. The fracture toughness evaluation showed that the G 1C The value is 52.53(J / m 2 ) was.

[0206] Sample 1.2: A UV-activated thermoplastic substrate (without silane sealer) was co-bonded to a carbon fiber reinforced epoxy skin following typical application procedures. The fracture toughness evaluation showed a G 1C The value is 87.56(J / m 2 ) was.

[0207] Sample 1.3: A UV-activated thermoplastic substrate and silane sealer were co-bonded to a carbon fiber reinforced epoxy skin following typical application procedures. The fracture toughness evaluation showed that the G 1C The value is 1085.78(J / m 2 ) was.

[0208] Example 2: Effect of chemical sealers on increasing adhesion between thermoplastic substrates and paints Example 2.1: General application procedure Studies were conducted to test the adhesion of paint applied directly to a chemically sealed thermoplastic composite substrate, Tenax-E TPCL PEEK-HTA40, with and without UV activation using an epoxy-based paint primer (DeSoto 512X310 from PPG Aerospace Coatings).

[0209] The substrate was washed twice with isopropyl alcohol and allowed to dry for 10 minutes after each wipe. When so treated, the washed substrate was exposed to a 290 mW / cm 2 When so treated, a silane-based sealer and a chrome-free epoxy sealer (Loctite EA9296NC) were applied to separate samples.

[0210] The silane sealer was applied by wiping the surface for 1 minute, allowing it to wet, then drying for 1 hour. It was then cured at room temperature for 1 hour or at elevated temperature (65.5 or 177°C) for 30 minutes. The final dry thickness of the silane sealer was 0.5-0.7 μm.

[0211] The chrome-free epoxy sealer was applied using a spray gun (Campbell Hausfeld Detailing Spray Gun Model #DH5500), a siphon-feed type gun with a 1.8 mm fluid nozzle size. During priming, the inlet air pressure was set at approximately 0.34 MPa and the parts were sprayed with the gun from approximately 15.2 cm away from the substrate surface. A Fisher Delta Isoscope Model #FMP10 was used to non-destructively measure the thickness of the dried primer on the adjacent aluminum "witness" panel via eddy currents. After drying for 30 minutes at room temperature, the product was cured for 1 hour at 177 °C. The dried thickness was approximately 1-2.5 μm and the resulting assessments shown in the table are valid for this range of thicknesses.

[0212] Primer paint was applied to each sealed surface of the thermoplastic substrate at a target thickness of 20-25 μm. Drying or curing of the paint was done according to the TDS of the paint primer. In case of epoxy based primers, the primer was cured at room temperature (25°C) for 7 days.

[0213] The samples were evaluated for their adhesive properties using the cross-hatch test method described elsewhere herein.

[0214] Example 2.2: Results (see Table 1) Sample 2.1: The epoxy-based primer was sprayed following typical application procedures onto a thermoplastic substrate that had no UV activation or sealer applied, and a crosshatch rating of 0B was obtained.

[0215] Sample 2.2: An epoxy-based primer was applied to a non-UV activated thermoplastic, but no sealer was applied. Crosshatch evaluation resulted in a rating of 0B.

[0216] Sample 2.3: The epoxy-based primer was applied to a non-UV activated thermoplastic substrate, followed by a silane sealer, both following typical application procedures, and cured at ambient temperature (25°C). Crosshatch evaluation yielded a rating of 0B.

[0217] Sample 2.4: The epoxy-based primer was applied to a UV-activated thermoplastic substrate and a silane sealer was applied following typical application procedures and cured at ambient temperature (25°C). A cross-hatch rating of 2B was obtained.

[0218] Sample 2.5: The epoxy-based primer was applied to a non-UV activated thermoplastic substrate and a silane sealer was applied and cured at elevated temperature (65.5°C) following typical application procedures. A cross-hatch rating of 0B was obtained.

[0219] Sample 2.6: The epoxy-based primer was applied to a UV-activated thermoplastic substrate, followed by a silane sealer and cured at elevated temperature (65.5°C) according to typical application procedures. A cross-hatch rating of 4B was obtained.

[0220] Sample 2.7: The epoxy-based primer was applied to a UV-activated thermoplastic substrate, followed by a silane sealer and cured at elevated temperature (177°C) following typical application procedures. A cross-hatch rating of 4B was achieved.

[0221] Sample 2.8: The epoxy-based primer was applied to a UV-activated thermoplastic substrate, followed by a silane sealer according to typical application procedures, dried at room temperature (25°C), and cured by UV exposure (similar conditions to the UV treatment). A cross-hatch rating of 4B was obtained.

[0222] Sample 2.9: An epoxy based primer was applied to a non-UV activated thermoplastic substrate and a chrome free epoxy sealer was applied and cured at elevated temperature (177°C) following typical application procedures. A crosshatch rating of 0B was obtained.

[0223] Sample 2.10: An epoxy-based primer was applied to a UV-activated thermoplastic substrate, and a chrome-free epoxy sealer was applied and cured at elevated temperature (177°C) following typical application procedures. A cross-hatch rating of 4B was obtained.

[0224] [Table 2]

[0225] Example 3: Effect of Silane-Based Sealers on Retaining UV and Plasma Activation of Thermoplastic Substrates Plasma activated substrates should be further processed (bonded / painted) in a fairly short time, as it is a well-known issue that plasma activation fades over time. Testing was performed using the methods described elsewhere herein. These experiments showed that the use of chemical sealants allows for retention of chemical activity over extended periods of time, both from adhesion angles and contact angles (using wettability as a reflection of surface activity).

[0226] Example 3.1: Summary of Results Plasma activated surface: The initial contact angle of the untreated PEEK substrate showed a contact angle of 64° and poor paint adhesion (0B). After plasma activation, the substrate had a contact angle of about 13° and could be painted with good adhesion (4B).

[0227] The contact angles of the activated plasma samples returned to their original value (58°) after aging (e.g., 8 months), reflecting partial or complete loss of activation. Paint adhesion on the aged specimens was also poor (1B).

[0228] In contrast to this observation, applying a chemical silane-based sealer after plasma activation provided samples where the plasma activation was preserved over this same period, allowing the samples to be painted after 8 months, with good paint adhesion (4B).

[0229] UV-activated surface: UV activation also resulted in a lower contact angle (54°), and over time (e.g., 8 months) the contact angle returned to its original value (64°).

[0230] In contrast, samples that were UV activated and treated with a chemical silane-based sealer after UV activation showed preserved activation over time, with the sample having a surface that allowed it to be painted after 8 months, and good paint adhesion (4B).

[0231] Example 3.2: General application procedure Studies were carried out to test the influence of different parameters on the preservation of UV / plasma activation of thermoplastic PEEK substrates with and without a silane-based chemical sealant. For this purpose, untreated and treated PEEK substrates with and without a chemical sealant were aged to evaluate the deactivation of the substrate over time and to prove the preservative effect of the sealant.

[0232] To evaluate the deactivation of treated substrates due to aging, the contact angle between a HPLC grade water drop and the substrate was measured with a BTG LABS Surface Analyst 3001. Cross-hatch adhesion tests of painted substrates were performed to investigate the activation of thermoplastic substrates after aging. All experiments were performed according to standard procedures. The contact angle between a HPLC grade water drop and the substrate was measured before and after the various treatment regimes. Where indicated to apply, the chemical silane-based sealer was a chemical silane-based organometallic sealer. The silane sealer was applied by wiping for 1 minute to wet the surface and then allowed to dry for 1 hour. Curing was then carried out at room temperature for 1 hour or at elevated temperature (65.5 or 177°C) for 30 minutes. The final dry thickness of the silane sealer was 0.5-0.7 μm. A Fisher Delta Isoscope Model #FMP10 was used to non-destructively measure the dry sealant thickness on adjacent aluminum "Witness" panels.

[0233] PEEK substrates with and without surface treatment and with and without chemical sealant were sealed in plastic bags with an aluminum interlayer for real-time aging. The sealed specimens were stored at room temperature without exposure to sunlight. After 8 months of aging, the contact angles of an HPLC grade water droplet with the untreated and UV / plasma treated substrates were remeasured. After aging, an epoxy-based paint primer (DeSoto 512X310 from PPG Aerospace Coatings) was applied to the surfaces of all thermoplastic substrates (including untreated, new and aged UV / plasma treated substrates) using a spray gun (Campbell Hausfeld Detailing Spray Gun Model #DH5500), a siphon feed type gun with a 1.8 mm fluid nozzle size. During priming, the inlet air pressure was set at approximately 0.34 MPa, and the parts were sprayed with the gun from approximately 15.2 cm away from the substrate surface. The target thickness of the dried paint primer was approximately 20-25 μm. Drying or curing of the paint was done according to the TDS of the paint primer cured for 7 days at room temperature (25° C.) Adhesion was done using the cross-hatch method as described elsewhere herein.

[0234] Example 3.3: Results (see Table 2) Sample 3.1: No treatment: Initial contact angle (control)

[0235] The contact angle of the untreated PEEK substrate without silane sealer was measured by a surface analyzer following typical application procedures, and the average contact angle value was approximately 64 degrees.

[0236] Sample 3.2: No treatment: Contact angle after 8 months (control)

[0237] The contact angle of the aged untreated PEEK substrate (without silane sealer) was measured by a surface analyzer following typical application procedures, and the average contact angle value was approximately 64 degrees.

[0238] Sample 3.3: Plasma (no aging): Contact angle

[0239] The contact angle of a fresh plasma activated PEEK substrate without any silane sealer was measured by a surface analyzer following typical application procedures. The average contact angle value was approximately 13 degrees.

[0240] Sample 3.4: Plasma + Aging: Contact angle

[0241] The contact angle of the aged plasma-activated PEEK substrate without silane sealer was measured by a surface analyzer following typical application procedures. After aging, the surface energy of the plasma-treated substrate decreased and the contact angle value nearly reached that of the untreated substrate. The average contact angle value was about 58 degrees.

[0242] Sample 3.5: UV (no aging): Contact angle

[0243] The contact angle of a fresh UV-activated PEEK substrate without any silane sealer was measured by a surface analyzer following typical application procedures. The average contact angle value was approximately 54 degrees.

[0244] Sample 3.6: UV+Aging: Contact angle

[0245] The contact angle of the aged UV-activated PEEK substrate without silane sealer was measured by a surface analyzer following the general application procedure. After aging, the surface energy of the UV-treated substrate decreased and the contact angle value nearly reached that of the untreated substrate. The average contact angle value was about 65 degrees.

[0246] Sample 3.7: Untreated (no aging) + Paint: Crosshatch

[0247] The epoxy-based primer was sprayed onto new, untreated thermoplastic substrates without a silane sealer following typical application procedures. Crosshatch evaluation yielded a rating of 0B.

[0248] Sample 3.8: Untreated + Aged + Paint: Crosshatch

[0249] The epoxy-based primer was sprayed onto aged, untreated thermoplastic substrates without a silane sealer following typical application procedures. Crosshatch evaluation yielded a rating of 0B.

[0250] Sample 3.9: Plasma (no aging) + paint: crosshatch

[0251] The epoxy-based primer was sprayed onto a virgin plasma-activated thermoplastic substrate without a silane sealer following typical application procedures. A cross-hatch evaluation resulted in a rating of 4B.

[0252] The epoxy-based primer was sprayed onto an aged plasma-activated thermoplastic substrate without a silane sealer following typical application procedures. A cross-hatch rating of 1B was obtained.

[0253] Sample 3.11: Plasma (no aging) + sealer + paint: crosshatch

[0254] The epoxy-based primer was sprayed onto a virgin plasma-activated thermoplastic substrate with a silane sealer following typical application procedures. A cross-hatch rating of 4B was obtained.

[0255] Sample 3.12: Plasma + Sealer + Aging + Paint: Crosshatch

[0256] The epoxy-based primer was sprayed onto an aged plasma-activated thermoplastic substrate with a silane sealer following typical application procedures. A cross-hatch rating of 4B was obtained.

[0257] Sample 3.13: UV (no aging) + paint: crosshatch

[0258] Apply the epoxy-based primer and silane sealer according to general application procedures. noneThe coating was sprayed onto a virgin UV-activated thermoplastic substrate and a cross-hatch rating of 0B was obtained.

[0259] Sample 3.14: UV+Aging+Paint: Crosshatch

[0260] The epoxy-based primer was sprayed onto an aged UV-activated thermoplastic substrate without a silane sealer following typical application procedures. A cross-hatch evaluation yielded a rating of 0B.

[0261] Sample 3.15: UV (no aging) + sealer + paint: crosshatch

[0262] The epoxy-based primer was sprayed onto a virgin UV-activated thermoplastic substrate with a silane sealer following typical application procedures. A cross-hatch rating of 4B was obtained.

[0263] Sample 3.16: UV + sealer + aging + paint: crosshatch

[0264] The epoxy-based primer was sprayed onto an aged UV-activated thermoplastic substrate with a silane sealer following typical application procedures. A cross-hatch rating of 4B was obtained.

[0265] [Table 3]

[0266] As those skilled in the art will appreciate, numerous modifications and variations of the present disclosure are possible in light of these teachings, all of which are contemplated herein. All references cited herein are incorporated by reference for their teachings at least in the context presented.

Claims

1. 1. A composite structure comprising a thermoplastic substrate having a chemical sealant bonded directly to a surface thereof by cross-polymer bonds between photolytically cleaved bonds of the thermoplastic substrate and reactive groups of the chemical sealant, and a surface treatment film layer, the chemical sealant is or comprises an organic or organometallic compound having one, two or more silanol, alkoxysilanol or alkoxysilane moieties; the chemical sealant is disposed between the thermoplastic substrate and the surface treatment film layer and bonds to both the thermoplastic substrate and the surface treatment film layer; the surface treatment film layer having a first surface bonded to the chemical sealant and a second surface opposite the first surface; The thermoplastic substrate comprises: (a) a polyaryletherketone selected from the group consisting of polyetheretherketone, polyetherketoneketone, polyetherketone, polyetheretherketoneketone, and polyetherketoneetherketoneketone; (b) a polymer containing a phenyl group bonded directly to a carbonyl group, optionally the carbonyl group being part of an amide group; (c) polyphenylene sulfide; (d) polyphenylene oxide; or (e) comprises a polyetherimide; The composite structure, wherein the surface treatment film layer is an epoxy-based thermosetting surface treatment film layer.

2. The composite structure of claim 1 , wherein the chemical sealant is bonded directly to a patterned portion of a surface of the thermoplastic substrate.

3. 3. The composite structure of claim 1 or 2, wherein the surface treatment film layer comprises an epoxy, an epoxy acrylate, or a copolymer or mixture thereof.

4. The composite structure of any one of claims 1 to 3, wherein the surface treatment film layer is applied but not cured or hardened.

5. The composite structure of any one of claims 1 to 3, wherein the surface treatment film layer is cured or fully solidified.

6. The surface treatment film layer is present, The surface treatment film layer itself comprises organic or inorganic fibers, cloth, fabric, mesh, or porous sheet in a thermoplastic or thermosetting polymer; (a) one or more peelable organic or inorganic cloths, fabrics, meshes, or porous sheets disposed on or under the second surface of the surface treatment film layer; (b) contained within, on, or under the second surface of said surface treatment film layer, one or more organic or inorganic cloths, fabrics, meshes, or porous sheets further comprising at least one electrically conductive material suitable for use in lightning strike protection, current dissipation, EMI shielding, or heat transfer applications; and / or (c) one or more particulate materials suitable for use as an impact modifier; 6. The composite structure of claim 1 which is a solid composite material, optionally comprising one or more of:

7. the second side of the surface treatment film layer is coated with a paint, optionally including a chemical sealant disposed between the second side of the surface treatment film layer and the paint; The composite structure of any one of claims 1 to 6, wherein the chemical sealant is or comprises an organic or organometallic compound having one, two or more silanol, alkoxysilanol or alkoxysilane moieties.

8. An aircraft or aerospace vehicle part comprising a composite structure according to any one of claims 1 to 7.

9. A part of a land vehicle comprising a composite structure according to any one of claims 1 to 7.

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