Direct application of thermosetting composite surfacing films to uv-treated thermoplastic surfaces and related composite structures

Abstract

SOLUTION: There are provided methods for directly adhering epoxy-based and other thermosetting surfacing films to solid thermoplastic surfaces, and structures derived or derivable from these methods. In some embodiments, there are provided composite structures comprising a thermoplastic substrate directly bonded to a thermosetting surfacing film, wherein the direct bonding defines an interface between a thermoplastic surface of the thermoplastic substrate and a first surface of the thermosetting surfacing film.SELECTED DRAWING: None

Description

[Technical Field]

[0001] Cross-Reference to Related Applications: None

[0002] This disclosure relates to methods for directly adhering epoxy-based and other thermosetting surface treatment films to solid thermoplastic surfaces, and structures derived or derivable from these methods. [Background technology]

[0003] 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.

[0004] Conventional composite structures used in the aerospace industry typically include a surface treatment film to provide the composite structure with necessary performance characteristics before painting. Surface treatment films, such as epoxy-based films, are often applied to the outer surface of polymer composites to provide the composite with the surface quality required for aerospace applications. For example, the surface treatment film may be co-cured with a prepreg to provide a protective, substantially porosity-free surface, and the resistivity of the surface treatment film may be lower than that of the underlying substrate, reducing the labor, time, and cost of composite manufacturing. Furthermore, these surface treatment films may be functionalized to improve their resistance to, for example, lightning strikes, electrostatic discharge, and electromagnetic discharge.

[0005] However, it is not always possible to co-cure or otherwise bond these surface treatment films with structural elements of polymer matrix composites during the manufacture of structural parts. Because some structural elements are not made of curing composite materials, such bonding to these materials is particularly difficult because the melting points of the thermoplastic materials used in aerospace applications are so high that the mixing process that occurs during bonding is not possible.

[0006] The adhesives industry is also well-known for the difficulty of bonding certain substrates, such as certain high-performance plastics. Thermoplastics such as PEEK (polyetheretherketone), PPS (polyphenylene sulfide), polyacrylamide (PARA), or polyetherimide (PEI) are attractive structural polymers due to their high specific strength or strength-to-density ratio, but they are also characterized by poor bonding properties. At least one reason is believed to be the low surface energy characteristics of the plastics being bonded.

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

[0008] 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] Plasma technology requires large equipment. Apart from capital costs, the size of the equipment presents challenges, making it difficult to transport for use in limited spaces, for example.

[0010] Physical attrition can also have mixed results, as it can be difficult to control the process sufficiently to address the issue of waste attrition by-products.

[0011] Primers can be used to great effect, but another method of activating the surface for subsequent bonding is always required. 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, even when a primer is used.

[0012] Although there are state-of-the-art proposed solutions to these problems, it is desirable to provide alternative solutions so that more choices are available to the end user. Summary of the Invention [Means for solving the problem]

[0013] SUMMARY The present disclosure relates to composite structures comprising a thermoset surface treatment film directly bonded to a thermoplastic substrate, methods for making these composite structures, and articles comprising these composite structures.

[0014] In certain embodiments, the composite structure includes a thermoplastic substrate directly bonded to a thermosetting surface treatment film, where the direct bond defines an interface between the thermoplastic surface of the thermoplastic substrate and a first side of the thermosetting surface treatment film, and the thermosetting surface treatment film further includes a second side opposite the first side of the thermosetting surface treatment film.

[0015] Definitions of thermoplastic substrates are provided elsewhere herein. While not necessarily so limited, in certain more specific embodiments, thermoplastic substrates include: (a) polyaryletherketones such as polyetheretherketone (PEEK), polyetherketoneketone (PEKK), polyetherketone (PEK), polyetheretherketoneketone (PEEKK), or polyetherketoneetherketoneketone (PEKEKK); (b) polymers containing a phenyl group directly attached 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 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 within the range of about 10 nm to about 500 nm or about 100 nm to about 450 nm, preferably within the range of about 200 nm to about 350 nm.

[0017] Additionally or alternatively, the thermoplastic substrate may have a radiation intensity of about 0.1 J / cm at at least one wavelength. 2 ~About 300J / cm 2 , preferably about 0.5 J / cm at at least 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 scission upon exposure to at least one wavelength of actinic radiation with energies in the range of .

[0018] In composite structures comprising a thermosetting surface treatment film directly bonded to a thermoplastic substrate, the thermosetting surface treatment film may be uncured (e.g., when initially prepared) or partially cured (e.g., after some post-treatment). The thermosetting surface treatment film adhered to a thermoplastic substrate or surface has a higher degree of cure than the as-supplied thermosetting surface treatment film.

[0019] In a preferred embodiment, the thermosetting surface treatment film is an epoxy-based thermosetting surface treatment film. Various types of epoxy-based surface treatment films are described herein.

[0020] As composite materials themselves, surface treated 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 flow agents, rheology modifiers, density modifiers, impact modifiers, preservatives, pigments, colorants, and the like.

[0021] 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.

[0022] Alternatively or additionally, the surface treatment film may comprise 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 comprises one or more peelable organic or inorganic fabrics, woven fabrics, meshes, or porous sheets disposed on or below the second side of the thermosetting surface treatment film.

[0023] 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.

[0024] Alternatively or additionally, the thermosetting surface treatment film is adhered to a thermoplastic substrate directly bonded to the thermosetting surface treatment film with sufficient strength to score at least 3B, 4B, or 5B in a 45° crosshatch tape test in accordance with ASTM D3359-09, the conditions of which are more fully described in the examples.

[0025] Still other embodiments include those methods for preparing directly bonded thermoplastic-thermoset composite structures. In certain of these, the method comprises: (a) exposing a surface of a thermoplastic substrate to actinic radiation sufficient to activate the surface of said thermoplastic substrate; (b) contacting the activated thermoplastic substrate surface with a thermosetting or thermosetting surface treatment film; and (c) applying pressure, and optionally heat, to the thermosetting or thermosetting surface treatment film against the thermoplastic substrate for a time and under conditions sufficient to form a direct bond between the thermoplastic substrate and the thermosetting or thermosetting surface treatment film. The method may further include curing the thermosetting or thermosetting surface treatment film, thereby forming a composite structure comprising the thermoplastic substrate directly bonded to the thermosetting surface treatment film.

[0026] With reference to the method, the nature of the substrate, the surface treatment film, and the method for activating the bond therebetween are consistent with the composite structures described elsewhere and will not be repeated here. Other aspects of the method (e.g., pressure and heat treatment) are further described elsewhere herein.

[0027] Yet another aspect of the present disclosure includes those articles that include the disclosed composite structures, including parts or land vehicles such as aircraft and automobiles. [Brief explanation of the drawings]

[0028] This 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. Furthermore, the drawings are not necessarily drawn to scale. The drawings are as follows:

[0029] [Figure 1] FIG. 1 shows the 45 degree crosshatch scribe and tape positioning for the adhesion testing described herein. DETAILED DESCRIPTION OF THE INVENTION

[0030] The present disclosure relates to new compositions of matter, including composite structures comprising a thermoplastic substrate directly bonded to a thermosetting surface treatment film, and methods of making and using these compositions.

[0031] 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 illustrated herein, and that the terminology used herein is for the purpose of describing particular embodiments by way of example only and is not intended to limit the claimed invention. Similarly, unless otherwise specified, any explanation of possible mechanisms or modes of action or reasons for improvement is for illustrative purposes only, and the disclosure herein should not be constrained by the correctness or incorrectness of such proposed mechanisms or modes of action or reasons for improvement. 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 embodiments in each of these contexts (i.e., compositions, methods of making, and methods of using).

[0032] composite structure The present disclosure includes those embodiments of composite structures, which include a thermoplastic substrate directly bonded to a thermosetting surface treatment film. As used herein, the term "direct bond" and its grammatical variations define an interface between the thermoplastic surface of the thermoplastic substrate and the first side of the thermosetting surface treatment film, where the thermoplastic surface and the first side are adhered to one another at a surface that forms a common boundary 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 in which pendant functional groups derived from activation of a polymer portion of the thermoplastic substrate directly bond to complementary binding moieties of the thermosetting surface treatment film, and the bonding is achieved by the presence of an intermediate binding group (e.g., without an external adhesive or similar composition).

[0033] The thermosetting surface treatment film further includes a second side opposite the first side of the thermosetting surface treatment film, which second side may optionally be functionalized as described elsewhere herein.

[0034] As described herein, the bond between a thermoplastic substrate and a 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 distinctions are merely semantic, and the descriptions should be considered equivalent throughout.

[0035] thermoplastic substrate In the context of the present disclosure, a thermoplastic substrate includes a thermoplastic polymer as commonly 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.

[0036] Even in this context, the thermoplastic polymer of the thermoplastic substrate is broadly defined, but those thermoplastic polymers containing 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) polymers containing a phenyl group directly attached 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)

[0037] 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.

[0038] As described elsewhere herein, the thermoplastic substrate may also generally be a composite material, in which 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, mesh, fabric, or porous sheet contained in a polymer matrix, and 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.

[0039] 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.

[0040] When a thermoplastic polymer is described as containing bonds that are 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 within the range of about 10 nm to about 500 nm or about 100 nm to about 450 nm, preferably 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 (approximately 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 (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).

[0041] When 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 those having an intensity of less than about 0.1 J / cm at at least one wavelength. 2 ~About 300J / cm 2 and preferably 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 2Additional embodiments include those activated by actinic radiation having an activation energy of 0.1 to 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 irradiation with two, three, four, or more wavelengths or wavelength ranges is also considered a further independent embodiment.

[0042] Thermosetting surface treatment film In the context of the present disclosure, a thermosetting surface treatment film includes a thermosetting polymer, as generally understood by those skilled in the art of polymer chemistry, however, in a preferred embodiment, the thermosetting surface treatment film encompasses (pre)polymer systems typically used in this context in the aerospace industry, including, for example, benzoxazine, bismaleimide, epoxy, (meth)acrylate, (meth)acrylamide, polyamide, polyimide, polyurethane, vinyl ester, or copolymers or mixtures thereof.

[0043] 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 resin; epoxy novolac; glycidyl ether of mono-, di-, tri- and polyhydric phenol; glycidyl ether of tetraphenol ethane; hydroxylphenylmethane-based epoxy resin; naphthalene-based epoxy resin; triglycidyl ether of amino-phenol resin; tetraglycidyl ether of methylenedianiline resin; glycidyl ether of aliphatic polyol; alicyclic epoxy resin; all epoxy type modified grade (containing halogen, silicon, phosphorus); all epoxy type toughened grade / adduct using rubber (such as butadiene, butadiene-acrylonitrile copolymer). 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 surface treatment films designated as Tencate TC235SF-1, AeroGlide surface treatment film, Surface Master 905 from Cytec, and Redux 641 from Hexcel, can also be used in these applications.

[0044] Independent embodiments include thermosetting surface treatment films that are still uncured, partially cured, or fully cured when adhered to a thermoplastic surface, each of which may occur at various stages in the process.

[0045] 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 thickness may be expressed in the ranges 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.

[0046] In another embodiment, the thermosetting surface treatment film has a hardness 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 to 0.06 psf (25 to 300 g / m 2 ), or some combination of two or more of these ranges.

[0047] 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, and the like, 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. At least one particulate filler or additive may include, for example, ceramics, polymers, glasses, or metal / semi-metallic materials or alloys thereof, or coated hybrid materials, including aluminum, boron, silicon, tin, zirconium, or aluminum carbides, nitrides, or oxides, carbon, copper, nickel, Sn—Zn, or stainless steel, or aramid. These fillers may be distributed substantially uniformly throughout the thickness dimension of the surface treatment film or may be concentrated on one of its first or second surfaces. These particulate fillers may comprise one or more of the functional materials described herein, such as ceramic, polymer, glass, or metal / metalloid materials or alloys thereof.

[0048] Alternatively or additionally, such surface treatment films may comprise one or more organic, inorganic, or metallic fibers, mesh, fabric, or porous sheet contained in a thermosetting resin.

[0049] 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.

[0050] The one or more organic or inorganic fibers, cloths, 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 cloths, fabrics, meshes, or porous sheets disposed on or beneath the second side of the thermosetting surface treatment film. The use of such peelable materials allows for subsequent removal of the peelable cloths, 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 has such peelable layers removed, revealing such a paint-ready surface.

[0051] In a further embodiment, the composite structure has a paint or other filled, unfilled, or clear coat finish applied to its 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 include polyacrylate, polyester, polymethacrylate, polyurethane, or copolymers or mixtures thereof. Bonding of the paint to the exposed surface can be physical, chemical, or both, depending on the nature of the selected paint. 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 without the processes described herein. As a result, it is expected that the bond formed between the exposed surface and the paint will likely be more strongly attributable to chemical interaction with the paint than would be the case without the process, thereby providing a more integral bond.

[0052] 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), polyetheretherketone (PEEK), polyamide, polyaryletherketone (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 laminating with an adhesive resin. The resin may be 5 to 50% by weight or 10 to 40% by weight of the surface treatment film composition. The polymer surface of the fabric or film may optionally be coated with silica, siloxane, aluminum oxide, or metal, or may be treated with plasma or silane.

[0053] The fabric or film may be a single-layer or multi-layer fabric structure. When the fabric is woven, the woven fabric comprises tightly woven monofilament or multifilament tows. Tightly woven, densely packed fabrics are preferred to provide a smooth finish that matches the finish desired in 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, providing significantly less surface roughness than highly calendared, closed weave fabrics.

[0054] Weave tightness can be described in terms of warp ends and weft ends per inch, both terms readily understood by those skilled in the art of woven fabrics. Fabrics or films of the present invention include those containing, independently, 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 of 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, taking into account warp end / weft end parameters, to provide a minimally open weave.

[0055] 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, expanded metal foil or polymer film, grid, mesh, screen, or web. In certain preferred embodiments, these porous sheets of additional functional material are present in or on the surface treatment film. Thus, the surface treatment film may optionally be 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.

[0056] That is, in some embodiments, these additional functional materials may be present as multiple sheets of functional material, or a single sheet may comprise a material 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 impart several properties (e.g., impact stability, dimensional stability, electrical conductivity, and heat transfer capability) to the film that improve its performance, such as providing increased strength, EMI shielding, and static and lightning protection to the substrate to which it is ultimately adhered. Furthermore, the phrase "at least one sheet of a second functional material" can refer to one or more sheets of a non-peelable 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-peelable) functional materials, as described below; (b) two or more sheets of the same (non-peelable) functional material; (c) two or more sheets of different (non-peelable) materials; or (d) two or more sheets of two or more (non-peelable) functional materials.

[0057] Additionally, while porous sheets of second functional materials may include woven fabrics and expanded films, these sheets 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), polyethersulfone (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 combination with any of the other materials described for this purpose. Aramid fibers (e.g., Kevlar® fibers) and imide fibers (e.g., Kapton® fibers) 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 withstand the peeling operation.

[0058] Functional materials may also include ceramic or glass fibers (e.g., oxides, carbides, nitrides, oxycarbides, oxynitrides, carbonitrides, or oxycarbonitrides containing 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 containing these materials. Exemplary materials include fibers or whiskers of alumina, aramid, boron, carbon, glass, silicon carbide, aluminum nitride, coated hybrids, or mixtures thereof, preferably fibers coated with glass, carbon, or metal. As used herein, the term "fiber" includes macro-, micro-, or nano-dimensional fibers, including wires 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; and polymer-coated glass, carbon, or metals. In some cases, the functional material is electrically conductive. In some embodiments, the functional material imparts magnetic properties to the surface treatment film.

[0059] In a particular embodiment within this more general description, the composite structure comprises an adhered thermosetting surface treatment film that is a multifunctional solid composite material that includes two or more of the following: (a) a first releasable 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, said at least one particulate filler or additive comprising, for example, a ceramic, polymer, glass, or metal / semi-metallic material or alloy thereof, including carbides, nitrides, or oxides of aluminum, boron, silicon, tin, zirconium, or aluminum, carbon, copper, nickel, Sn—Zn, or stainless steel, or aramid; and, optionally (d) UV resistant polymers or UV stabilizing additives known in the art.

[0060] 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 between the thermoplastic and thermoset materials.

[0061] In some embodiments, the thermosetting 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 according to ASTM D3359-09, the conditions of which are more fully described in the Examples.

[0062] Production method 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.

[0063] 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 sufficient to activate the surface of said thermoplastic substrate; (b) contacting the activated thermoplastic substrate surface with a thermosetting or thermosetting surface treatment film; and (c) applying pressure, and optionally heat, to the thermosetting or thermosetting-capable surface treatment film against the thermoplastic substrate for a time and under conditions sufficient to form a direct bond between the thermosetting or thermosetting-capable surface treatment film and the thermoplastic substrate.

[0064] In some embodiments, the methods further include curing the thermosetting or thermosettingable surface treatment film, thereby forming a composite structure comprising a thermoplastic substrate directly bonded to the thermosetting surface treatment film.

[0065] These embodiments include methods using any of the thermoplastic substrates and surface treated films described elsewhere herein.

[0066] These embodiments also encompass the use of actinic radiation, as described elsewhere herein. For completeness, they are repeated here in part to encompass cases 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 nm. 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.

[0067] Further, the actinic radiation may be about 2 mW / cm for a time period ranging from about 2 to about 600 seconds, or from about 10 to about 60 seconds. 2 ~About 3000mW / cm 2 , approximately 2 mW / cm 2 ~about 2000mW / cm 2 , about 300mW / cm 2 ~about 600mW / cm2 or preferably at a rate within one or more ranges of about 40-500 mW / cm 2 In certain other embodiments, 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 is.

[0068] 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. Faster activation may be desirable in a continuously moving production line, e.g., where successive substrates pass through the light source to activate them. The exposure time may be from about 0.1 seconds to about 360 minutes, e.g., 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 a throughput perspective, an exposure time of from about 0.1 seconds to about 360 minutes is preferred.

[0069] Additionally or alternatively, actinic radiation may be applied at one or more wavelengths, in one or more of the aforementioned rates, for a time 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.

[0070] The energy required to prepare a particular thermoplastic-thermoset bond pair varies depending on the nature of the materials being bonded and the time available for such chemical activation. Good results have been achieved and are generally considered available after 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

[0071] The following ranges are suggested to be at least, if not more generally, appropriate, 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 / cm2 ×10~120 seconds=0.1~36J / cm 2 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

[0072] Illumination using each of these ranges independently is considered an independent embodiment.

[0073] In all aspects of the 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, e.g., 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, etc.

[0074] The methods described herein do not require the incorporation of an active agent into the thermoplastic substrate, and they do not require treatments that physically alter the surface to enhance adhesion, such as chemical etching (e.g., acid etching) or physical abrasion (e.g., sand / grit blasting) or other treatments (e.g., flame treatment; plasma treatment; ozone treatment, etc.).

[0075] Unless otherwise specified, the surface of the thermoplastic substrate is otherwise irradiated at ambient temperatures and conditions, although in some embodiments, irradiation occurs at above ambient temperatures (e.g., within one or more ranges of 20°C to 25°C, 25°C to 30°C, 30°C to 40°C, 40°C to 50°C, or 50°C to 60°C). Additionally or alternatively, in other embodiments, irradiation may occur in the absence of oxygen, in a vacuum, in ambient air, or in an oxygen-enriched environment.

[0076] Irradiation may be performed on either the entire surface of the thermoplastic substrate or in a patterned area. For example, exposure of the surface to actinic radiation may be selectively applied to create areas of the surface that are activated for subsequent bonding and areas that are not activated for subsequent bonding. A mask may be used that has areas that transmit actinic radiation to create areas of the surface that are activated for subsequent bonding and areas that block actinic radiation 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 be exposed to radiation. When performed in a patterned or patchy manner, the surface treatment film will adhere substantially only to these activated sections or will adhere substantially more than the non-activated sections.

[0077] Without intending to be bound by any particular theory, it is possible that actinic radiation 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, which, if reactive groups are present in the surface-treated film, will form cross-polymer bonds.

[0078] Once the thermoplastic surface is activated, pressure, and optionally heat, is applied to the thermosetting surface-treated film. In one embodiment, the applied pressure is one or more pressures in the range of about 0.05 MPa to 1.2 MPa, or one or more of the 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, and 1.1 MPa to 1.2 MPa, or a combination of two or more of the foregoing ranges, such as 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 to 60 minutes, 60 to 90 minutes, 90 to 120 minutes, 120 to 180 minutes, 180 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 ranging from 150°C to 160°C, 160°C to 170°C, 170°C to 180°C, 180°C to 190°C, or 190°C to 200°C, e.g., 170°C to 180°C. In a separate embodiment, heat is applied statically or at an increasing rate as described in the examples, for part or all of the time period described.

[0079] Once adhered, the bond strength between the thermoplastic substrate and the thermosetting surface treatment film is consistent with the bond metrics described elsewhere herein.

[0080] Articles incorporating these composite structures In addition to composite structures and methods for making them, the present disclosure contemplates all articles that include these composite structures. Composite structures are suitable for articles of all sizes, but are particularly attractive for large structures. Contemplated structures include primary structural elements, secondary structural elements, exterior elements, interior elements, and structures that may be one or more of any one of commercial and personal aircraft and aerospace applications, automobiles, watercraft (including ships), railroad cars and tankers, and storage tanks.

[0081] That is, aircraft parts including 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.

[0082] Additionally, components of a land vehicle, such as an automobile, bicycle, motorcycle, truck, or personal 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 this disclosure.

[0083] term In this disclosure, the singular forms "a," "an," and "the" include plural references, and reference to a numerical value includes at least that value unless the context clearly dictates otherwise. Thus, for example, reference to a "material" is a reference to at least one of such materials and equivalents thereof known to those skilled in the art.

[0084] When values ​​are expressed as approximations using the descriptor "about," it will be understood that the value forms another embodiment. In general, the use of the term "about" indicates approximations that can vary depending on the desired properties sought to be obtained by the disclosed subject matter and should be interpreted in the specific 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 gradations 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. Where present, all ranges are inclusive and combinable. That is, reference to values ​​stated in a range encompasses all values ​​within that range.

[0085] For clarity, certain features of the present disclosure that are 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, individual embodiments are considered to be combinable with other embodiments, and such combinations are separate embodiments. Conversely, various features of the present disclosure that are described for brevity in the context of a single embodiment may also be provided separately or in any subcombination. Finally, while embodiments may be described as part of a series of steps or as part of a more general structure, each step may also be considered an independent embodiment that can be combined with other steps.

[0086] 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. Embodiments described with the phrase "comprising" (or its equivalent) also provide, as embodiments, those described independently with the phrases "consisting of" and "consisting essentially of." For those embodiments provided in terms of "consisting essentially of," the basic and novel characteristic is the ease of operation of the method or composition / system to provide a composite structure described herein or associated with a particular composition or method step.

[0087] When a list is presented, unless otherwise stated, it is to be understood that each individual element of that list, and every combination of that list, is a separate embodiment. For example, a list of embodiments presented as "A, B, or C" is a separate embodiment of C. 1-3 Similarly, "A," "B," "C," "A or B," "A or C," "B or C," or "A, B, or C" embodiments should be interpreted as encompassing the embodiments of "A," "B," "C," "A or B," "A or C," "B or C," or "A, B, or C" as separate embodiments.

[0088] 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 component).

[0089] Throughout this specification, words should be given their ordinary meaning as understood by one of ordinary skill in the relevant art. However, to avoid any doubt, the meaning of certain terms will be specifically defined or clarified.

[0090] 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).

[0091] In the context of this disclosure, the term "composite structure" refers to a layered structure resulting from the direct bonding between a thermoplastic substrate and a thermosetting surface-treated film. It is recognized that both the thermoplastic substrate and the thermosetting surface-treated 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-treated films.

[0092] 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. This is closely associated with the production of thermoset polymers. Curing can be affected by 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 pre-polymer material.

[0093] "Optional" or "optionally" means that the subsequently described circumstance may or may not occur, and so the description encompasses both cases where the circumstance occurs and cases where it does not occur.

[0094] The terms "method" and "process" are considered interchangeable within this disclosure.

[0095] 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 containing heteroatoms, are broken, thereby generating functional groups that make the surface more chemically active than an untreated surface. These more chemically active functional groups can or do bond with a thermosetting surface treatment film during curing of the surface treatment film.

[0096] 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.

[0097] The term "surface treatment film" refers to a solid-form composite material 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). These are typically applied to aircraft substrate surfaces 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 alternatively contain one or more organic, inorganic, or metallic fibers, meshes, fabrics, or porous sheets contained in a thermosetting resin. In epoxy-based thermosetting surface treatment films, the thermosetting resin comprises 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).

[0098] As used herein, the term "thermoplastic" refers to a plastic polymer material that becomes pliable 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.

[0099] The terms "thermosetting" or "thermosettable" are used herein in the conventional sense to refer to polymers or prepolymers or resins that irreversibly harden through a crosslinked network during cure (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.

[0100] As is customary 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 skill in the art will be able to distinguish the meaning of these terms in the context of their use.

[0101] A "thermosetting or thermosettable surface treatment film" or "thermoset(ting) film" is a solid composite material comprising a recited 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., 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 comprises an epoxy-based resin. Surface treatment films 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.

[0102] The following list of embodiments is intended to supplement, not replace or replace, the previous description.

[0103] Embodiment 1 A composite structure comprising a thermoplastic substrate directly bonded to a thermosetting surface treatment film; The direct bond defines an interface between the thermoplastic surface of the thermoplastic substrate and a first side of the thermosetting surface treatment film, and the thermosetting surface treatment film further includes a second side opposite the first side of the thermosetting surface treatment film.

[0104] Unless otherwise specified, the thermoplastic surface is identical or chemically matched to the thermoplastic substrate, where the term "chemically matched" means that the polymer building blocks of the substrate and surface are identical, even if some of the surface binding sites are altered by photolytic activation.

[0105] Embodiment 2 The thermoplastic substrate is (a) polyaryletherketones such as polyetheretherketone (PEEK), polyetherketoneketone (PEKK), polyetherketone (PEK), polyetheretherketoneketone (PEEKK), or polyetherketoneetherketoneketone (PEKEKK); (b) polymers containing a phenyl group directly attached 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).

[0106] 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 cleavage upon exposure to actinic radiation of sufficient intensity, and the actinic radiation includes radiation at least one wavelength within the range of about 10 nm to about 500 nm or about 100 nm to about 450 nm, preferably within the range of about 200 nm to about 350 nm. Additional aspects of this embodiment include subranges of these ranges described elsewhere herein.

[0107] Embodiment 4 the thermoplastic substrate has an irradiance of about 0.1 J / cm at at least one wavelength (optionally one, two, three, or four wavelengths); 2 ~About 300J / cm 2 , preferably about 0.5 J / cm at at least one wavelength. 2 ~About 250J / cm 2 or about 1.5 J / cm 2 ~About 250J / cm 2 The composite structure of any one of embodiments 1-3, comprising a thermoplastic polymer whose bonds are susceptible to at least partial photolytic cleavage upon exposure to actinic radiation of energies within the range of: Additional aspects of this embodiment include subranges of these ranges described elsewhere herein.

[0108] Embodiment 5 5. The composite structure of any one of embodiments 1-4, wherein the thermosetting surface treatment film is directly bonded to the patterned portion of the thermoplastic surface.

[0109] Embodiment 6 6. The composite structure of any one of embodiments 1-5, wherein the thermosetting surface treatment film is uncured.

[0110] Embodiment 7 7. The composite structure of any one of embodiments 1-6, wherein the thermosetting surface treatment film is partially cured.

[0111] Embodiment 8 8. The composite structure of any one of embodiments 1-7, wherein the thermosetting surface treatment film is an epoxy-based thermosetting surface treatment film.

[0112] Embodiment 9 9. The composite structure of any one of embodiments 1-8, wherein the thermosetting surface treatment film is itself a solid composite material comprising one or more organic or inorganic fibers, cloth, fabric, mesh, or porous sheet contained within a thermosetting resin.

[0113] Embodiment 10 10. The composite structure of any one of embodiments 1-9, wherein the thermosetting 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 below the second surface of the thermosetting surface treatment film.

[0114] Embodiment 11 11. The composite structure of any one of embodiments 1-10, wherein the thermosetting surface treatment film is a solid composite comprising one or more organic or inorganic cloths, fabrics, meshes, or porous sheets contained within a thermosetting resin, and wherein the thermosetting surface treatment film further comprises at least one electrically conductive material suitable for use in lightning strike protection, current dissipation, EMI shielding, or heat transfer applications.

[0115] Embodiment 12 12. The composite structure of any one of embodiments 1-11, wherein the epoxy-based thermosetting surface treatment film is a solid composite comprising one or more organic or inorganic cloths, fabrics, meshes, or porous sheets, and wherein the epoxy-based thermosetting surface treatment film further comprises at least one particulate material suitable for use as an impact modifier contained in a thermosetting resin.

[0116] Embodiment 13 The thermosetting surface-treated film is (a) a first releasable 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, said at least one particulate filler or additive comprising, for example, a ceramic, polymer, glass, or metal / semi-metallic material or alloy thereof, including aluminum, boron, silicon, tin, zirconium, or aluminum carbides, nitrides, or oxides, carbon, copper, nickel, Sn—Zn, or stainless steel, or aramid; (d) UV-resistant polymers or UV-stabilizing additives; 13. The composite structure of any one of embodiments 1 to 12, which is a multifunctional solid composite comprising two or more of:

[0117] Embodiment 14 14. The composite structure of any one of embodiments 1-13, wherein the thermosetting surface treatment film has an area weight of less than 0.150 pounds per square foot.

[0118] Embodiment 15 15. The composite structure of any one of embodiments 1-14, wherein the thermosetting surface treatment film has a total thickness in the range of 25 to 12,500 microns (1 to 500 mils). Additional aspects of this embodiment include subranges of these ranges as described elsewhere herein.

[0119] Embodiment 16 16. The composite structure of any one of claims 1 to 15, wherein the thermosetting surface treatment film is adhered to the thermoplastic substrate to which it is directly bonded with sufficient strength to score at least 3B, 4B, or 5B in a 45° crosshatch tape test according to ASTM D3359-09 (conditions are more fully described in the examples).

[0120] Embodiment 17 1. A method for preparing a directly bonded thermoplastic-thermoset composite material, comprising: (a) exposing a surface of a thermoplastic substrate to actinic radiation sufficient to activate the surface of said thermoplastic substrate; (b) contacting the activated thermoplastic substrate surface with a thermosetting or thermosetting surface treatment film; and (c) applying pressure, and optionally heat, to the thermosetting or thermosetting-capable surface treatment film against the thermoplastic substrate for a time and under conditions sufficient to form a direct bond between the thermosetting or thermosetting-capable surface treatment film and the thermoplastic substrate.

[0121] 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.

[0122] Embodiment 18 18. The method of embodiment 17, further comprising curing the thermosetting or thermosettingable surface treatment film, thereby forming a composite structure comprising the thermoplastic substrate directly bonded to the thermosetting surface treatment film.

[0123] Embodiment 19 the thermoplastic substrate comprising: (a) Polyaryletherketones such as polyetheretherketone (PEEK), polyetherketoneketone (PEKK), polyetherketone (PEK); polyetheretherketoneketone (PEEKK), or polyetherketoneetherketoneketone (PEKEKK); (b) polymers containing a phenyl group directly attached 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 19. The method of claim 17 or 18, comprising (e) polyetherimide (PEI).

[0124] Embodiment 20 20. The method of any one of embodiments 17-19, wherein the thermosetting or thermosetting-capable surface treatment film is an epoxy-based thermosetting or thermosetting-capable surface treatment film, and the corresponding thermosetting surface treatment film is an epoxy-based thermosetting surface treatment film.

[0125] Embodiment 21 21. The method of any one of embodiments 17-20, wherein the actinic radiation is applied at one or more wavelengths within the range of about 10 nm to about 450 nm, preferably within 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.

[0126] Embodiment 22 The actinic radiation is about 0.1 J / cm at at least one wavelength 2 ~About 300J / cm 2 , preferably about 0.5 J / cm at at least one wavelength. 2 ~About 250J / cm 2 or about 1.5 J / cm 2 ~About 250J / cm 2 The method of any one of embodiments 17-21, wherein actinic radiation is applied at one or more wavelengths with an energy within the range of 1000 to 15000 Hz. Additional aspects of this embodiment include subranges of these ranges as described herein. Similarly, additional aspects of this embodiment include rates and durations of application of actinic radiation as described and listed elsewhere herein.

[0127] Embodiment 23 23. The method of any one of embodiments 17 to 22, wherein the pressure applied to the thermosetting surface-treated film is 0.4 to 1 MPa at one or more elevated temperatures, for example, 160°C to 180°C, for a time period ranging from about 30 minutes to about 240 minutes.

[0128] Embodiment 24 24. The method of any one of claims 17-23, wherein the directly bonded thermoplastic-thermoset composite exhibits an adhesive strength between the thermoplastic substrate and the thermoset surface treatment film, exhibiting a score of at least 3B, 4B, or 5B in a 45° crosshatch tape test according to ASTM D3359-09.

[0129] Embodiment 25 A composite structure prepared by the method according to any one of embodiments 17 to 24.

[0130] Embodiment 26 An aircraft part comprising the composite structure of any one of embodiments 1 to 16. In certain aspects of this embodiment, the aircraft part comprises an aircraft tail, wing, fuselage, or propeller.

[0131] Embodiment 27 A part or portion of an automobile, bicycle, motorcycle, truck, or land vehicle such as a personal watercraft, comprising the composite structure of any one of embodiments 1 to 16. In certain aspects of this embodiment, the part comprises a hood, a fender, a bumper, a hull, or a frame. [Example]

[0132] Standard Terms of Use Under standard conditions, the surface of the thermoplastic substrate was cleaned using isopropanol wipes to remove dust. After cleaning, where indicated, the surface of the thermoplastic substrate was irradiated with UV light for the specified time and energy using a UVALOC1000 light source equipped with a mercury D-type bulb (iron doped). The surface treatment film was then layered onto the thermoplastic surface, and the assembly was consolidated using 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) First, a test specimen was prepared by placing a single-sided adhesive (OST) surface treatment film with its adhesive side facing onto a thermoplastic substrate, and then the part / specimen was pre-positioned. Then, using an arrangement of film material (nylon film), test specimen, perforated Teflon film, and breather cloth, the test specimen was placed inside the edge of the caul plate. (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 an 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.

[0133] After this integration, the assembly was disassembled, visually inspected, and tested for adhesion.

[0134] Standard Test Conditions Adhesion performance was evaluated using the crosshatch test method, which was carried out as follows: (1) Test specimens were scribed with a cutting tool as shown in Figure 1. In Figure 1, the cut was made through the coating (surface treatment film) to the substrate. The cutting tool can be a sharp razor blade, scalpel, or knife. In this test, 45-degree crosshatch scribes were made, with the angle between the two sets of parallel scribes being 45±5 degrees and the parallel scribes spaced approximately 3.05 mm apart. (2) Masking tape (3M Tape No. 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 ranged from 0B to 5B, with 0B being the worst condition, representing greater than 65% area removed. The rating classifications are summarized in Table 1.

[0135] [Table 1]

[0136] material: Thermoplastic substrate: The thermoplastic substrate used in these examples was a thermoplastic integral laminate (TPCL) made from several layers of woven powder thermoplastic fabric. The powder fabric consisted of high tenacity carbon fiber (Tenax-E HTA40 E13 3K 200tex) and a PEEK matrix (42% by weight). The fabric had an areal weight of 285 g / m 2 The panel had a total thickness of 1.5 mm and five harness patterns.

[0137] Surface treatment film: The surface treatment film used in these examples was a dual-care option (120-177°C) epoxy-based composite surface treatment film that could be cured under non-autoclave conditions (vacuum bag at low vacuum pressure of 0.07 MPa) or autoclave (higher pressure of 0.31 MPa). The surface treatment film contained nonwoven fabric (polyester or carbon) and had a total area weight of 146 g / m. 2 had.

[0138] Lightning Strike Surface Treatment Film: This film was also a dual-care option (120-177°C) epoxy-based composite surface treatment film that could be cured under non-autoclave conditions (vacuum bag at low vacuum pressure of 0.07 MPa) or autoclave (higher pressure of 0.31 MPa). The lightning strike film also contained expanded copper foil (in addition to polyester / carbon nonwoven fabric). The area weight of the epoxy resin was 122 g / m. 2 and the area weight of the copper foil is 70 g / m 2 It was.

[0139] Peel-off and paint-on surface treatment film: This film is also a dual-care option (120-177°C) epoxy-based composite surface treatment film, which can be cured under non-autoclave conditions (vacuum bag at low vacuum pressure of 0.07 MPa) or autoclave (higher pressure of 0.31 MPa) without polyester / carbon nonwoven fabric. This film has a plain weave pattern and an area weight of 59 g / m. 2 The final areal weight of the film after curing and peel ply removal was approximately 78 g / m 2 It was.

[0140] Peel-off and Paint-on Lightning Film: This film is also a dual-care option (120-177°C) epoxy-based composite surface treatment film, which can be cured under non-autoclave conditions (vacuum bag at low vacuum pressure of 0.07 MPa) or autoclave (higher pressure of 0.31 MPa) without polyester / carbon nonwoven fabric. This film contains expanded copper foil in addition to nylon peel-ply fabric. The copper foil area weight is 70 g / m. 2 and the final areal weight of the film after curing is about 148 g / m 2 It was.

[0141] Comparative Examples 1 to 4: No UV light pretreatment The thermoplastic substrates were treated only by wiping the surface with an isopropanol wipe to remove dust (i.e., no UV light was applied). Each surface-treated film was layered onto the PEEK surface and cured as described above. The surface-treated films used in these comparative examples are listed in Table 2. In each case, visual inspection of the resulting surface-treated films revealed a smooth, uniform surface. In each case, a hatching rating of 0B was obtained.

[0142] [Table 2]

[0143] Examples 1 to 4: Use of UV light treatment The conditions of the comparative example were repeated, except that before applying the surface-treated film to the thermoplastic carbon-reinforced substrate Tenax-ETPCL PEEK-HTA40, the substrate was irradiated with UV light for 30 seconds using a UVALOC 1000 light source equipped with a mercury D-type bulb (iron doped). The pretreatment strengths of the various films are summarized in Table 3.

[0144] [Table 3]

[0145] In both cases, the bond strength was rated at 4B by the crosshatch test, indicating good adhesion. See Table 2.

[0146] As those skilled in the art will appreciate, many modifications and variations of the present disclosure are possible in light of these teachings, and all such 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 directly bonded to a thermosetting surface treatment film, the direct bond defines an interface between a thermoplastic surface of the thermoplastic substrate and a first side of the thermosetting surface treatment film; The thermosetting surface treatment film further comprises a second surface opposite the first surface of the thermosetting surface treatment film.

2. The thermoplastic substrate is (a) polyaryletherketones such as polyetheretherketone (PEEK), polyetherketoneketone (PEKK), polyetherketone (PEK), polyetheretherketoneketone (PEEKK), or polyetherketoneetherketoneketone (PEKEKK); (b) polymers containing phenyl groups directly bonded to carbonyl groups, optionally the carbonyl groups being part of amide groups, such as polyacrylamide (PARA); (c) polyphenylene sulfide (PPS); (d) polyphenylene oxide (PPO); or 10. The composite structure of claim 1, comprising: (e) polyetherimide (PEI).

3. 10. The composite structure of claim 1, 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, the actinic radiation comprising radiation at least one wavelength within the range of about 10 nm to about 500 nm or about 100 nm to about 450 nm, preferably within the range of about 200 nm to about 350 nm.

4. The thermoplastic substrate has an energy density of about 0.1 J / cm at at least one wavelength (optionally 1, 2, 3, or 4 wavelengths). ２ ~Approx. 300J / cm ２ , preferably about 0.5 J / cm at at least one wavelength. ２ ~Approx. 250J / cm ２ or about 1.5 J / cm ２ ~Approx. 250J / cm ２ 10. The composite structure of claim 1, comprising a thermoplastic polymer whose bonds are susceptible to at least partial photolytic scission upon exposure to actinic radiation of energies in the range of .

5. The composite structure of any one of claims 1 to 4, wherein the thermosetting surface treatment film is uncured.

6. The composite structure of any one of claims 1 to 4, wherein the thermosetting surface treatment film is partially cured.

7. The composite structure of any one of claims 1 to 4, wherein the thermosetting surface treatment film is an epoxy-based thermosetting surface treatment film.

8. 8. The composite structure of any one of claims 1 to 7, wherein the thermosetting surface treatment film itself is a solid composite material comprising one or more organic or inorganic fibers, cloths, fabrics, meshes, or porous sheets contained within a thermosetting resin.

9. 9. The composite structure of claim 1, wherein the thermosetting surface treatment film is a solid composite material comprising one or more peelable organic or inorganic fabrics, textiles, meshes, or porous sheets disposed on or below the second surface of the thermosetting surface treatment film.

10. 10. The composite structure of any one of claims 1 to 9, wherein the thermosetting surface treatment film is a solid composite comprising one or more organic or inorganic cloths, fabrics, meshes, or porous sheets contained within a thermosetting resin, and wherein the thermosetting surface treatment film further comprises at least one electrically conductive material suitable for use in lightning strike protection, current dissipation, EMI shielding, or heat transfer applications.

11. 11. The composite structure of any one of claims 1 to 10, wherein the epoxy-based thermosetting surface treatment film is a solid composite material comprising one or more organic or inorganic cloths, fabrics, meshes, or porous sheets, and the epoxy-based thermosetting surface treatment film further comprises at least one particulate material suitable for use as an impact modifier contained in a thermosetting resin.

12. The thermosetting surface-treated film is (a) a first releasable 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, said at least one particulate filler or additive comprising, for example, a ceramic, polymer, glass, or metal / semi-metallic material or alloy thereof, including carbides, nitrides, or oxides of aluminum, boron, silicon, tin, zirconium, or aluminum, carbon, copper, nickel, Sn—Zn, or stainless steel, or aramid; (d) UV-resistant polymers or UV-stabilizing additives; 12. The composite structure of any one of claims 1 to 11, which is a multifunctional solid composite material comprising two or more of:

13. 13. The composite structure of any one of claims 1 to 12, wherein the thermosetting surface treatment film is adhered to the thermoplastic substrate directly bonded to the thermosetting surface treatment film with sufficient strength to score at least 3B, 4B, or 5B according to ASTM D3359-09 of the 45° Crosshatch Tape Test.

14. 1. A method for preparing a directly bonded thermoplastic-thermoset composite material comprising: (a) exposing a surface of a thermoplastic substrate to actinic radiation sufficient to activate the surface of said thermoplastic substrate; (b) contacting the activated thermoplastic substrate surface with a thermosetting or thermosetting surface treatment film; and (c) applying pressure, and optionally heat, to the thermosetting or thermosetting surface treatment film against the thermoplastic substrate for a time and under conditions sufficient to form a direct bond between the thermosetting or thermosetting capable surface treatment film and the thermoplastic substrate; and A method comprising:

15. 15. The method of claim 14, further comprising curing the thermosetting or thermosettingable surface treatment film, thereby forming a composite structure comprising a thermoplastic substrate directly bonded to the thermosetting surface treatment film.

16. The thermoplastic substrate comprises: (a) Polyaryletherketones such as polyetheretherketone (PEEK), polyetherketoneketone (PEKK), polyetherketone (PEK); polyetheretherketoneketone (PEEKK), or polyetherketoneetherketoneketone (PEKEKK); (b) polymers containing phenyl groups directly bonded to carbonyl groups, optionally the carbonyl groups being part of amide groups, such as polyacrylamide (PARA); (c) polyphenylene sulfide (PPS); (d) polyphenylene oxide (PPO); or The method of claim 14, comprising (e) polyetherimide (PEI).

17. The method according to any one of claims 14 to 16, wherein the thermosetting or thermosetting-capable surface treatment film is an epoxy-based thermosetting or thermosetting-capable surface treatment film, and the corresponding thermosetting surface treatment film is an epoxy-based thermosetting surface treatment film.

18. 17. The method of any one of claims 14 to 16, 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.

19. The actinic radiation is about 0.1 J / cm at at least one wavelength. ２ ~Approx. 300J / cm ２ , preferably about 0.5 J / cm at at least one wavelength. ２ ~Approx. 250J / cm ２ or about 1.5 J / cm ２ ~Approx. 250J / cm ２ 17. The method of any one of claims 14 to 16, wherein the radiation is applied at one or more wavelengths with an energy in the range

20. 17. The method according to any one of claims 14 to 16, wherein the pressure applied to the thermosetting surface treatment film is 0.4 to 1 MPa, optionally at one or more elevated temperatures, for example 160°C to 180°C, for a time in the range of about 30 minutes to about 240 minutes.

21. 21. The method of any one of claims 14 to 20, wherein the directly bonded thermoplastic-thermoset composite exhibits an adhesive strength between the thermoplastic substrate and the thermoset surface treatment film that scores at least 3B, 4B, or 5B in a 45° crosshatch tape test according to ASTM D3359-09.

22. A composite structure prepared by the method of any one of claims 14 to 21.

23. An aircraft part comprising a composite structure according to any one of claims 1 to 13.

24. An automotive part comprising a composite structure according to any one of claims 1 to 13.

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