electrically insulating conductor

Abstract

In a first aspect, an electrically insulated conductor includes an electrically conductive core and an insulating wrap surrounding the electrically conductive core. The insulating wrap includes a base film tape. The base film tape includes a polymeric core layer and a first thermoplastic polymeric outer layer adhered to a first side of the polymeric core layer. The polymeric core layer and the first thermoplastic polymeric outer layer each have a glass transition temperature (T g ) of 200 °C or greater. A ratio of a bend radius (R) to a width (W) of the insulated conductor is in a range of 0.8: 1 to 2: 1. An interlaminar fracture toughness (G Ic ) of the first thermoplastic polymeric outer layer relative to the electrically conductive core is 200 J / m 2 or greater.

Description

Technical Field

[0001] The field of this disclosure is electrically insulating conductors. Background Technology

[0002] Electrically insulated conductors are used in electric motors in vehicles. In small vehicles (like cars), the smaller motor size presents unique challenges for electrical insulation due to the constrained geometry. Wire insulation capable of withstanding the tight, curved geometry used in these smaller motors is required. Furthermore, the elimination of fluorinated materials used in some insulations is necessary due to environmental concerns.

[0003] Modern electric motors also demand increasingly higher performance from electrically insulating conductors, such as polymer-coated wires. As systems are designed to operate at higher voltages for extended periods, the need for corona-resistant films is becoming increasingly important. These films, when used as wire insulation, need to maintain good electrical properties (e.g., voltage withstand) and mechanical properties (e.g., resistance to abrasion and dynamic cutting). Typically, wires will be bent into various shapes or orientations, and the corona-resistant film covering the wire needs to be able to be bent into these shapes or orientations. Adding fillers to corona-resistant films can negatively impact their mechanical properties, and these films may become more brittle (lower tensile strength and elongation).

[0004] Corona-resistant films have previously been used in the construction of electromagnetic wires for traction motors, i.e., wires consisting of single copper strands covered with an insulating film material. While the performance drawbacks of insulating materials can be overcome in higher voltage applications by using thicker insulating wrapping layers, this adds undesirable volume and weight to the wrapped wire. There is a need for improved electrical insulation, corona-resistant films that can withstand the requirements of higher voltages, such as in aerospace applications, and can do so while limiting the film's shape factor. Summary of the Invention

[0005] In a first aspect, the electrically insulating conductor includes a conductive core and an insulating wrapping surrounding the conductive core. The insulating wrapping includes a base film tape. The base film tape includes a polymer core layer and a first thermoplastic polymer outer layer adhered to a first side of the polymer core layer. The polymer core layer and the first thermoplastic polymer outer layer each have a glass transition temperature (T0) of 200°C or higher. g The ratio of the bending radius (R) to the width (W) of the insulated conductor is in the range of 0.8:1 to 2:1. The interlaminar fracture toughness (G) of the first thermoplastic polymer outer layer relative to the conductive core... Ic ) is 200 J / m 2 Or larger.

[0006] Polyimide films with electrically insulating and corona-resistant composite fillers can be formed from essentially chemically converted or thermally converted polyimides. These films can also be produced by carefully selecting dianhydride and diamine monomers for the polyimide backbone.

[0007] As used herein, the term "substantially chemically converted" means imidizing polyimide by 75% or more, 80% or more, 85% or more, 90% or more, or 95% or more using a method incorporating conversion chemicals (i.e., catalysts and dehydrating agents). In this method, a solvated mixture (polyamic acid casting solution) may be cast or applied to a support to obtain a partially imidized gel film, and then heated in an oven using convective and radiative heat to remove the solvent and complete the imidization. The percentage imidization can be measured by comparing the results at 1365 cm⁻¹ in an attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectrum. -1 (Polyimide CN) relative to 1492 cm -1 The ratio of the strength of the aromatic tensile (used as an internal standard) is compared with the ratio of a sample prepared by a standard curing method that is defined as 100% cured.

[0008] Depending on the context, as used herein, "diamine" is intended to mean: (i) an unreacted form (i.e., a diamine monomer); (ii) a partially reacted form (i.e., one or more portions of an oligomer or other polymer precursor derived from or otherwise attributable to a diamine monomer); or (iii) a fully reacted form (one or more portions of a polymer derived from or otherwise attributable to a diamine monomer). Depending on the specific embodiments chosen in the practice of this invention, the diamine may be functionalized with one or more of these portions.

[0009] In fact, the term "diamine" is not intended to limit (or be interpreted literally) the number of amine moieties in a diamine component. For example, (ii) and (iii) above include polymeric materials that may have two, one, or zero amine moieties. Alternatively, diamines can be functionalized with additional amine moieties (in addition to the amine moieties at the ends of monomers that react with dianhydrides to extend the polymer chain). Such additional amine moieties can be used to crosslink polymers or to provide additional functional groups to the polymer.

[0010] Similarly, the term “dianhydride” as used herein is intended to refer to a component that reacts (in collaboration with) a diamine and is capable of reacting to form an intermediate (which can then be cured into a polymer). Depending on the context, the term “acid anhydride” as used herein may refer not only to the acid anhydride moiety itself, but also to a precursor of the acid anhydride moiety, such as: (i) a pair of carboxylic acid groups (which can be converted to an acid anhydride through dehydration or a similar type of reaction); or (ii) an acyl halide (e.g., chloride) ester functional group (or any other functional group currently known or to be developed in the future) capable of being converted to an acid anhydride functional group.

[0011] Depending on the context, "dianhydride" can mean: (i) an unreacted form (i.e., a dianhydride monomer, whether the anhydride functional group is in the form of a true anhydride or a precursor anhydride, as discussed in the preceding paragraphs); (ii) a partially reacted form (i.e., one or more portions of an oligomer or other partially reacted or precursor polymer composition that has reacted from or is otherwise attributable to a dianhydride monomer); or (iii) a fully reacted form (one or more portions of a polymer derived from or otherwise attributable to a dianhydride monomer).

[0012] Depending on the specific embodiments chosen in the practice of this invention, the dianhydride can be functionalized with one or more portions. In fact, the term "dianhydride" is not intended to be limited (or interpreted literally) in relation to the number of anhydride moieties in the dianhydride component. For example, (i), (ii), and (iii) (in the preceding paragraphs) include organic substances that may have two, one, or zero anhydride moieties, depending on whether the anhydride is in a precursor or reactive state. Alternatively, the dianhydride component can be functionalized with additional anhydride-type moieties (in addition to the anhydride moieties that react with diamines to provide the polymer). Such additional anhydride moieties can be used to crosslink the polymer or to provide other functional groups to the polymer.

[0013] Polymer films can be prepared using any of many polymer manufacturing processes. It would be impossible to discuss or describe all possible manufacturing processes that can be used in the practice of this invention. It should be understood that the monomer system of this invention is capable of providing the aforementioned advantageous properties in a variety of manufacturing processes. The compositions of this invention can be manufactured as described herein and can be readily manufactured using any conventional or unconventional manufacturing techniques in any of many (possibly countless) ways in which a person skilled in the art may employ them.

[0014] Although similar or equivalent methods and materials to those described and materials herein may be used in the practice or testing of this invention, suitable methods and materials are described herein.

[0015] When quantities, concentrations, or other values ​​or parameters are given as ranges, preferred ranges, or a series of upper and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pairing of any upper or preferred value with any lower or preferred value, regardless of whether the range is disclosed individually. When numerical ranges are listed herein, unless otherwise stated, the range is intended to include its endpoints, as well as all integers and fractions within that range. The specific values ​​listed are not intended to limit the scope of the invention.

[0016] In describing certain polymers, it should be understood that applicants sometimes refer to these polymers by the monomers used to make them or by the amount of monomers used to make them. Although such descriptions may not include specific names used to describe the final polymer or may not include process-defining terms for the product, any such reference to monomers and amounts should be interpreted as indicating that the polymer is made from those monomers or that amount of monomers, and as referring to the corresponding polymer and its compositions.

[0017] Unless otherwise stated, the materials, methods, and examples in this article are illustrative only and not intended to be limiting.

[0018] As used herein, the terms “comprises,” “comprising,” “includes,” “including,” “has,” “having,” or any other variation thereof are intended to cover non-exclusive inclusion. For example, a method, process, article, or apparatus that includes a list of elements is not necessarily limited to those elements, but may include other elements not expressly listed or inherent to such a method, process, article, or apparatus. Furthermore, unless expressly stated to the contrary, “or” refers to inclusive or, not exclusive or. For example, conditions A or B are satisfied by any of the following: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); and both A and B are true (or exist).

[0019] Additionally, the term "a / an" is used to describe the elements and components of the invention. This is done merely for convenience and to give the general meaning of the invention. This description should be interpreted as including one / an or at least one / an, and the singular form includes the plural form, unless it is obvious that it refers to something else.

[0020] It should be understood that although the terms first, second, third, etc., may be used herein to describe different elements, components, regions, layers, and / or portions, these elements, components, regions, layers, and / or portions should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer, and / or portion from another element, component, region, layer, and / or portion. Thus, a first element, component, region, layer, and / or portion may be referred to as a second element, component, region, layer, and / or portion without departing from the teachings of this invention. Similarly, the terms "top" and "bottom" are only relative to each other. It should be understood that when an element, component, layer, etc., is inverted, the "bottom" before the inversion will be the "top" after the inversion, and vice versa. When an element is referred to as being "on" or "set" on "another element," it means that it is positioned on or below a part of the object, rather than essentially meaning that it is positioned on the upper side of the part of the object based on the direction of gravity, and it may be directly on other elements or an intervening element may exist between them. In contrast, when an element is referred to as "directly on" another element or "directly set on" another element, there is no intermediary element.

[0021] Furthermore, it should be understood that when an element, component, region, layer, and / or part is referred to as being "between" two elements, components, regions, layers, and / or parts, it can be the only element, component, region, layer, and / or part between the two elements, components, regions, layers, and / or parts, or there may be one or more intervening elements, components, regions, layers, and / or parts. Hairpin bending requirements

[0022] Hairpin winding technology is becoming increasingly prevalent in the design of electric motors (e-motors) used in electric vehicles, particularly for traction motor applications requiring high power density. Compared to other technologies such as round wire winding-based motors, hairpin motors can have a higher copper fill factor, thus allowing for higher power density and better thermal management performance.

[0023] Another common design shift in electric motors is increasing the system voltage to a higher operating voltage. Maintaining the integrity of the electrical insulation around the conductive components in the motor is crucial to preventing ground faults in electric motors; otherwise, a short circuit will render the entire electric motor unusable because insulation failures are difficult to repair.

[0024] Hairpins are typically produced from direct conductive elements (e.g., copper wire) around which an electrically insulating material (composed of one or more distinct layers) is carried. These elements are usually supplied in a continuous form and are therefore first cut into individual blocks, which are then formed into hairpin shapes. The forming process itself can take different forms, such as single-stage or multi-stage processes. The shape of the hairpins is determined by their desired arrangement in the stator of an electromechanical device. The geometry of a hairpin can be described by a series of bends around a defined radius, where the severity of a given bend segment can be described by the ratio of the bend radius (R) of the bend segment to the width (W) of the conductive element segment undergoing the bend (containing any insulating material). A smaller ratio corresponds to a more severe bend, which in turn places higher demands on the mechanical properties of the insulating material and its adhesion to the conductive element. Since the mechanical strain applied to the insulating material during the bend process exceeds the mechanical properties of the insulating material, more severe bends are more likely to trigger mechanical failures in the insulating material, such as wrinkling, creases, delamination, etc. Given the current trend of reducing the size of electric motors, it is becoming increasingly important that the insulation material can be formed without damage for a ratio R / W of less than 1, preferably less than 0.8.

[0025] If a given R / W value is provided, methods and formulas known in the engineering field can be applied to determine the theoretical minimum mechanical properties that the insulating material needs to possess to be formed by hairpin without visible damage. Determining these minimum mechanical properties also requires considering that the insulating material can be applied and present in various arrangements, such as seamless or overlapping strips spirally wrapped around the conductive element, seamless overlapping or non-overlapping strips longitudinally wrapped around the conductive element, varnish / enamel coatings, or extruded layers, and combinations thereof. In one embodiment, overlapping strips spirally wrapped around the conductive element or seamless overlapping or non-overlapping strips longitudinally wrapped around the conductive element are preferred.

[0026] In order to achieve damage-free formation, insulation must have certain mechanical and structural properties.

[0027] The elongation at break (also known as breaking strain, ultimate strain, elongation at break percentage, or tensile elongation at break) of the insulating material must be high enough to withstand the strain generated during the bending operation during hairpin formation.

[0028] For spirally wrapped insulation, several strain-strengthening points exist in the region near the overlap, and no formula allows for an accurate evaluation of strain on the insulation as a function of the desired variable. A nonlinear finite element model that explicitly captures the geometry of the insulation on the conductor can be used to calculate the elongation at break requirement for a range of desired geometries. In one embodiment, the insulation material has a minimum elongation at break value of at least 60% to accommodate bending with an R / W ratio in the range of 0.8:1 to 2:1, or 0.8:1 to 1.5:1, or 0.8:1 to 1.2:1.

[0029] In addition to having a minimum elongation at break, the insulating material must also possess strong interfaces to prevent debonding or adhesion loss from the conductor or itself during hairpin forming processes. Adhesion interlaminar fracture toughness is a structural mechanical property that quantifies interfacial strength. There is no formula that allows calculation of interlaminar fracture toughness as a function of geometry and material properties. Nonlinear finite element models that explicitly capture the geometry of the insulation on the conductor and the interfaces within the structure can be used to calculate these requirements for a range of desired geometries and material mechanical properties. In one embodiment, the insulating material adhered to the conductive element has a strength of 200 J / m². 2 Or larger, 250 J / m 2 Or larger, 300 J / m 2 Or larger, or 400 J / m 2 Or a greater minimum interlaminar fracture toughness (G Ic In another embodiment, the insulating material itself consists of two or more distinct layers, and any two layers within the insulating material are coupled at a speed of 140 J / m. 2 Or larger, 175 J / m 2 Or larger, 200 J / m 2 Or larger, or 250 J / m 2 Or a larger minimum G Ic They adhere to each other. In another embodiment, the insulating material adheres to itself, for example as part of the insulating material spirally wrapped around the conductive element, with a minimum G. Ic 140 J / m 2 Or larger, 175 J / m 2 Or larger, 200 J / m 2 Or larger, or 250 J / m 2 Or larger.

[0030] In G Ic Beyond a certain value, the interface can be considered no longer related to adhesive failure, as cohesive failure modes begin to compete for the cause of overall material failure. In one embodiment, if the G between the two materials... Ic Over 700 J / m2 If so, it is no longer considered an interface that may undergo damage from the adhesive material.

[0031] Two experimental methods were used to obtain the desired interlaminar fracture toughness. The double cantilever beam experimental compliance method, described by BRK Blackman and AJ Kinloch, “Fracture Tests for Structural Adhesive Joints,” in “Fracture Mechanics Testing Methods for Polymers, Adhesives and Composites,” edited by A. Pavan, DR Moore, and JG Williams (Elsevier Science, Amsterdam, 2001), was used to measure the Type I interlaminar fracture toughness (G) of most insulation-insulation interfaces. Ic In cases where debonding occurs at the substrate interface rather than at the insulation-insulation interface, G Ic The values ​​are reported as greater than those obtained using this testing method. T-peel and 90-degree peel tests are used to derive interlaminar fracture toughness for some insulation-insulation interfaces and all insulation-conductor interfaces. Although peel strength is typically reported as a measurement of interfacial strength, it is less reliable than a quantitative measure because it has contributions from other deformation modes (strain energy stored in the peel arm, energy dissipated due to tensile deformation of the peel arm, and energy generated due to bending of the peel arm). For a more detailed discussion of this topic, see Kinloch, AJ, Lau, CC, and Williams, JG. The peeling of flexible laminates. Int J Fract 66, 45-70 (1994). Methods for recovering interlaminar fracture toughness are similar to those described in the paper by Kinloch et al., but instead of using formulas, a finite element model of the peel test is employed to more accurately interpret the material response. In the case of multilayer insulation materials, where delamination propagates from the conductor-film interface to the interfaces within the multilayer insulation material, these values ​​are reported as greater than those obtained using this method.

[0032] In the case of multilayer insulation materials, where a compliant insulation layer is adhered to one or more rigid insulation layers, the compliant layer can generate high shear strain during bending operations. To avoid high shear strain and excessive deformation of a single layer in the insulation material when subjected to high lateral loads, it is recommended to use only materials with similar moduli as part of the multilayer insulation material. In one embodiment, the ratio of the tensile moduli between two adjacent layers in the multilayer insulation material is 0.5:1 or greater, 0.6:1 or greater, or 0.7:1 or greater when the smaller tensile modulus value of the first layer is divided by the larger tensile modulus value of the second layer. Electrical insulation materials

[0033] Materials suitable for electrically insulating conductive components include thermoplastic and thermosetting polymers. Within this group of materials, polymers have high thermal ratings, such as a high relative temperature index (RTI) as defined by UL or IEEE, a high temperature index according to ASTM D2304, or a high thermal rating according to IEC 60085 or NEMA ratings or NEMA / UL letter ratings. In one embodiment, the electrical insulating material has a heat resistance rating of 200°C or higher.

[0034] Specific examples of material classes with high heat ratings include polyimide (PI), poly(amide-imide) (PAI), polyaryletherketone (PAEK) (which includes PEK (polyetherketone), PEKK (polyetherketoneketone), PEEK (polyetheretherketone)), polyphenylene sulfide (PPS), polyphenylene sulfone (PPSU), polyethersulfone (PES), polyetherimide (PEI), polyester-imide (PEI), or mixtures thereof. In one embodiment, an electrical insulating material based on polyimide (PI) is used. In one embodiment, the insulating material consists of two or more layers of polyimide material, wherein the chemical properties of each polyimide layer may be the same or different. In one embodiment, a multilayer consisting of two or three layers of polyimide material is used. In one embodiment, a multilayer polyimide material in which the outermost layers are chemically identical is used. In one embodiment, a polyimide material having a residual organic solvent content of 1 wt% or less, 0.8 wt% or less, 0.5 wt% or less, or 0.3 wt% or less is used. In one embodiment, a polyimide (PI)-based electrical insulation material is used, which is in tape form and can be used in longitudinal or spiral wire wrapping processes. In another embodiment, the polyimide (PI)-based electrical insulation material does not contain or come into contact with other material categories, such as silicones or fluoropolymers, such as PTFE, FEP, or PFA.

[0035] While the aforementioned materials can form the majority of the electrical insulation material in terms of weight and volume, other material categories may exist as minor components in the electrical insulation material to improve the adhesion, scratch and abrasion resistance, or abrasion or other properties relevant to this application of the primary insulation material. These material categories may individually have a thermal rating of 200°C or higher, but not lower than 200°C. These minor components may exist macroscopically or microscopically mixed with the majority of the electrical insulation material, or they may exist as a separate layer or component surrounding the conductive element, as the innermost or outermost layer, or as a layer separating two or more primary insulation material layers.

[0036] Based on the theoretically derived mechanical properties that electrical insulating materials should possess to withstand hairpin forming processes described by specific R / W values ​​of 0.8 or greater without visible damage, the tensile properties of a range of polyimide materials are characterized according to ASTM D882-18 and summarized in Table 1. Table 1

[0037] Polyimide 1 is a polyimide film with a thickness of approximately 25 µm, composed of 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) / pyromellitic dianhydride (PMDA) (molar ratio of 1.2:1) and 4,4'-diaminodiphenyl ether (ODA). This film was prepared using a procedure similar to that described in Example 9 below. The Tg of this film... g It is approximately 320°C.

[0038] 100HN is a polyimide film composed of PMDA and ODA, with a thickness of approximately 25 µm, and is commercially available from DuPont de Nemours, Inc. (Wilmington, Delaware).

[0039] Polyimide 2 is a polyimide film composed of PMDA and ODA, additionally containing approximately 17% by weight of alumina. The alumina is added to the polyamic acid in the form of a 25% by weight slurry of alumina in DMAc. The film has a thickness of approximately 25 µm. The film's T... g The temperature is 380°C.

[0040] Polyimide 3 and polyimide 4 are polyimide films composed of PMDA and ODA, additionally containing approximately 21% by weight of alumina. The alumina is added to the polyamic acid in the form of a 25% by weight slurry of alumina in DMAc. These films have thicknesses of approximately 19 µm and approximately 25 µm, respectively. The T0 of these films… g Greater than 380°C.

[0041] 100HA is a polyimide film composed of PMDA and ODA, with a thickness of approximately 25 µm, and is commercially available from DuPont.

[0042] Polyimide 5 is a polyimide film composed of BPDA / PMDA (molar ratio of 1.2:1) and ODA, with a thickness of approximately 25 µm, and further contains 17 wt% alumina. The alumina is added to the polyamic acid in the form of a 25 wt% slurry of alumina in DMAc. The film's T... g It is approximately 325°C.

[0043] Polyimide 6 and polyimide 7 are polyimide films composed of BPDA / PMDA (molar ratio 1:1.45) and ODA / p-phenylenediamine (PPD) (molar ratio 1:1.49), with thicknesses of approximately 12 µm and approximately 25 µm, respectively. These films were prepared using a procedure similar to that described in Example 9 below. The T5 of these films... g It is approximately 350°C.

[0044] 50FEP is a film of a melt-processable copolymer of tetrafluoroethylene and hexafluoropropylene, with a thickness of approximately 12 µm, and is commercially available from McMaster-Carr (Elmhurst, Illinois).

[0045] Polyimide 8 is a polyimide film composed of 4,4'-oxyphthalic anhydride (ODPA) / PMDA (molar ratio 4:1) and 1,3-bis(4-aminophenoxy)benzene (RODA) with a thickness of approximately 51 µm. This film was prepared as described in Example 9 below. The Tg of this film... g It is approximately 230°C.

[0046] Polyimide 9 is a thermoplastic polyimide film derived from ODPA / PMDA (molar ratio 4:1) and RODA / 1,6-diaminohexane (HMD) (molar ratio 2.33:1), with a thickness of approximately 75 µm. This film was prepared using a procedure similar to that described in Example 9 below. The film's T... g It is approximately 198°C.

[0047] The survey of data presented in Table 1 shows that different monomer combinations produce polyimide films with different mechanical properties. More specifically, polyimide films containing PMDA and ODA or doped with RODA appear to be more likely to meet or exceed the previously described minimum elongation at break value of 60% or higher. Furthermore, the inclusion of fillers (specifically alumina) does not deteriorate the elongation at break values ​​of some of these polymers to the point that they would no longer be considered suitable.

[0048] Table 1 also shows that, based on the preferred ratio of tensile modulus described earlier, not only can any two or more (polyimide) materials be selected to form an insulating (polyimide) multilayer, but the modulus range of the various individual polyimide materials is large, and in the most extreme cases, this can result in a modulus ratio between the two materials of less than 0.7. Instead, the chemical composition of each polyimide layer in the insulating polyimide multilayer must be carefully selected based on the individual modulus of each polyimide film. It should be noted that when this is done on the base film tape (after the material has been applied to the conductor) or its cross-section, the modulus of the material can also be determined very approximately by applying ASTM E2546-15 in combination with methods discussed, for example, in Materials Characterization 58, 380-389 (2007). conductive core

[0049] In one embodiment, the conductive core may include a wire. In one embodiment, the wire may comprise a conductive metal such as copper (e.g., copper classified as 10100, 10200, or 11000), copper alloys, silver, silver alloys, aluminum, stainless steel, etc. In one embodiment, the wire may be solid or hollow. In one embodiment, the copper may include oxygen-free copper. In one embodiment, the copper wire may be plated with a metallic or metallic alloy plating such as tin, silver, nickel, and mixtures and alloys thereof. In one embodiment, a high-strength copper alloy may be used, which is resistant to corrosion and oxidation at high temperatures, as well as to chemicals, alkalis, hydraulic fluids, and fuels. In one embodiment, the wire may have a rectangular, circular, square, stranded, Litz-shaped, or other similar shapes. In one embodiment, the conductor has a rectangular shape with a defined corner radius of 1 mm or less. In one embodiment, the conductor has properties as described in ASTM B250, ASTM B48, ANSI / NEMA MW 1000, and / or IEC 60317.

[0050] In one embodiment, the conductive core may include a stranded conductor, such as a high-temperature multistrand stranded wire having individual strands ranging from 19 to 5000, with a rated temperature up to 260°C. As used herein, the term "stranded conductor" is intended to refer to a wire in which multiple uninsulated wires are bundled together to form a single-conductor wire, as opposed to a "Litz" wire in which each of the multiple strands is individually insulated. In one embodiment, the individual strands may contain copper. In one embodiment, the copper may include oxygen-free copper. In one embodiment, the individual copper strands may be plated with a metallic or metallic alloy plating, such as tin, silver, nickel, and mixtures and alloys thereof. In one embodiment, a high-strength copper alloy may be used, which is resistant to corrosion and oxidation at high temperatures, as well as to chemicals, alkalis, hydraulic fluids, and fuels. In one embodiment, the dimensions of the multistrand stranded wire may range from AWG (United States Wire Gauge) 0000 to AWG 26 (the diameter of the wire ranges from 0.0175 to 0.6050 inches (0.445 to 15.4 mm)). The dimensions of individual strands of a given wire can range from AWG 24 to AWG 40 (diameter ranging from 0.0031 to 0.0201 inches (78.7 to 511 µm)).

[0051] Stranded conductors can be manufactured in various configurations, most commonly concentric (true concentric, equilay concentric, unidirectional concentric, and unilay concentric), bundled, and rope-like, where concentricity is defined as a center strand being surrounded by one or more layers of spiral strands laid out in a geometric pattern. The geometric pattern requires that the concentric configuration be produced using only 7, 19, 37, 61 (etc.) strands or components, following a pattern where each successive layer has 6 more strands than the layer below it. In all types of concentric configurations, the strand geometry is consistent over the entire length of the conductor. That is, the center strand and the strands in each layer remain in their respective positions from the beginning to the end of their length. In one embodiment, a concentric stranded conductor is used. organic solvents

[0052] The useful organic solvent used to synthesize the polymers of the present invention is preferably capable of dissolving the polymer precursor material. This solvent should also have a relatively low boiling point, such as below 225°C, so that the polymer can be dried at moderate (i.e., more convenient and less costly) temperatures. Boiling points below 210°C, 205°C, 200°C, 195°C, 190°C, or 180°C are preferred.

[0053] Available organic solvents include: N-methylpyrrolidone (NMP), N,N-dimethylacetamide (DMAc), methyl ethyl ketone (MEK), N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), tetramethylurea (TMU), ethylene glycol ethyl ether, diethylene glycol diethyl ether, 1,2-dimethoxyethane (monoethylene glycol dimethyl ether), diethylene glycol dimethyl ether (diethylene glycol dimethyl ether), 1,2-bis-(2-methoxyethoxy)ethane (triethylene glycol dimethyl ether), γ-butyrolactone and bis-(2-methoxyethyl) ether, tetrahydrofuran (THF), ethyl acetate, hydroxyethyl acetate, ethylene glycol monoacetate, acetone, and mixtures thereof. In one embodiment, preferred solvents include N-methylpyrrolidone (NMP) and N,N-dimethylacetamide (DMAc). diamine

[0054] In one embodiment, any number of suitable diamines can be used as monomers to form the polymer backbone. Aromatic diamines may include fluorinated aromatic diamines such as 2,2'-bis(trifluoromethyl)benzidine (TFMB), 2,2'-bis-(4-aminophenyl)hexafluoropropane, 4,4'-diamino-2,2'-trifluoromethyl diphenyl ether, 3,3'-diamino-5,5'-trifluoromethyl diphenyl ether, 9,9'-bis(4-aminophenyl)fluorene, 4,4'-trifluoromethyl-2,2'-diaminobiphenyl, and 4,4'-oxy-bis[(2-trifluoromethyl)aniline]( ). 1,2,4-OBABTF), 4,4'-oxy-bis[(3-trifluoromethyl)aniline], 4,4'-thiobis[(2-trifluoromethyl)aniline], 4,4'-thiobis[(3-trifluoromethyl)aniline], 4,4'-sulfoxyl-bis[(2-trifluoromethyl)aniline], 4,4'-sulfoxyl-bis[(3-trifluoromethyl)aniline], 4,4'-keto-bis[(2-trifluoromethyl)aniline], 1,1-bis[4'- [4'-amino-2'-trifluoromethylphenoxy)phenyl]cyclopentane, 1,1-bis[4'-(4'-amino-2'-trifluoromethylphenoxy)phenyl]cyclohexane, 2-trifluoromethyl-4,4'-diaminodiphenyl ether; 1,4-(2'-trifluoromethyl-4',4'-diaminodiphenoxy)benzene, 1,4-bis(4'-aminophenoxy)-2-[(3',5'-ditrifluoromethyl)phenyl]benzene (6F-amine), 1,4-bis[2'-cyano-3'- (4”-Aminophenoxy)phenoxy]-2-[(3',5'-ditrifluoro-methyl)phenyl]benzene (6FC-diamine), 3,5-diamino-4-methyl-2',3',5',6'-tetrafluoro-4'-tri-fluoromethyl diphenyl ether, 2,2-bis[4(4-aminophenoxy)phenyl]phthaloyl-3',5'-bis(trifluoromethyl)aniline (6FADAP) and 3,3',5,5'-tetrafluoro-4,4'-diamino-diphenylmethane (TFDAM).

[0055] Other available aromatic diamines may include 4,4'-diaminobiphenyl, 4,4'-diaminoterphenyl, 4,4'-diaminobenzoylaniline (DABA), 4,4'-diaminophenylbenzoate, 4,4'-diaminobenzophenone, 4,4'-diaminodiphenylmethane (MDA), 4,4'-diaminodiphenyl sulfide, 4,4'-diaminodiphenyl sulfone, 3,3'-diaminodiphenyl sulfone, bis[4-(4-aminophenoxy)phenyl]sulfone (BAPS), 4,4'-bis(4-aminophenoxy)biphenyl (BAPB), 4,4'-diaminodiphenyl ether ( ODA), 3,4'-diaminodiphenyl ether, 4,4'-isopropylidene diphenylamine, 2,2'-bis(3-aminophenyl)propane, 2,2-bis(4-aminophenyl)propane, 3,3'-dimethyl-4,4'-diaminobiphenyl, 4-aminophenyl-3-aminobenzoate, bis(p-β-amino-tert-butylphenyl) ether, p-bis-2-(2-methyl-4-aminopentyl)benzene. In one embodiment, the diamine is a triamine, such as N,N-bis(4-aminophenyl)-n-butylamine, N,N-bis(4-aminophenyl)methylamine, or N,N-bis(4-aminophenyl)aniline.

[0056] Other available aromatic diamines may include 1,2-bis(4-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene (RODA), 1,2-bis(3-aminophenoxy)benzene, 1,3-bis(3-aminophenoxy)benzene, 1-(4-aminophenoxy)-3-(3-aminophenoxy)benzene, 1,4-bis-(4-aminophenoxy)benzene, 1,4-bis(3-aminophenoxy)benzene, 1-(4-aminophenoxy)-4-(3-aminophenoxy)benzene, 2,2-bis(4-[4-aminophenoxy]phenyl)propane (BAPP), and 2,2'-bis(4-phenoxyaniline)isopropylidene.

[0057] Other available aromatic diamines may include p-phenylenediamine (PPD), m-phenylenediamine (MPD), 2,5-dimethyl-1,4-diaminobenzene, 2,5-dimethyl-1,4-phenylenediamine (DPX), 1,4-naphthylenediamine, 1,5-naphthylenediamine, 1,5-diaminonaphthyl, m-phenylenediamine, and p-phenylenediamine.

[0058] In one embodiment, additional available diamines for forming the polyimide may include aliphatic diamines such as 1,2-diaminoethane, 1,6-diaminohexane (HMD), 1,4-diaminobutane, 1,5-diaminopentane, 1,7-diaminoheptane, 1,8-diaminooctane, 1,9-diaminononane, 1,10-diaminodecane (DMD), 1,11-diaminoundecane, 1,12-diaminododecane (DDD), 1,16-hexamethylenediamine, 1,3-bis(3-aminopropyl)-tetramethyldisiloxane, trans-1,4-diaminocyclohexane (CHDA), isophorone diamine (IPDA), bicyclo[2.2.2]octane-1,4-diamine, and combinations thereof. Other aliphatic diamines suitable for practicing the invention include those having six to twelve carbon atoms or combinations of longer-chain and shorter-chain diamines, provided that both the stretchability and flexibility of the polymer are maintained. Long-chain aliphatic diamines can increase flexibility.

[0059] Other available additional diamines for forming the polymer may include alicyclic diamines (which may be fully or partially saturated), such as cyclobutane diamines (e.g., cis- and trans-1,3-diaminocyclobutane, 6-amino-3-azaspiro[3.3]heptane and 3,6-diaminospiro[3.3]heptane), bicyclo[2.2.1]heptane-1,4-diamine, isophorone diamine, and bicyclo[2.2.2]octane-1,4-diamine. Other alicyclic diamines may include cis-1,4-cyclohexane diamine, trans-1,4-cyclohexane diamine, 1,4-bis(aminomethyl)cyclohexane, 4,4'-methylenebis(cyclohexylamine), 4,4'-methylenebis(2-methyl-cyclohexylamine), and bis(aminomethyl)norbornene.

[0060] In one embodiment, the polyimide is primarily derived from 4,4'-diaminodiphenyl ether (ODA) or its isomers, 1,3-bis(4-aminophenoxy)benzene (RODA), and 1,6-diaminohexane (HMD). Dihydride

[0061] In one embodiment, any amount of suitable dianhydride can be used as a monomer to form the polymer backbone. The dianhydride can be used in its tetracarboxylic acid form (or as a mono, di, tri, or tetracarboxylic acid ester), or as its diester acyl halide (chloride). However, in some embodiments, the dianhydride form may be preferred because it is generally more reactive than an acid or ester.

[0062] Examples of suitable aromatic dianhydrides include 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), 2-(3',4'-dicarboxyphenyl)-5,6-dicarboxybenzimidazole dianhydride, 2-(3',4'-dicarboxyphenyl)-5,6-dicarboxybenzoxazole dianhydride, 2-(3',4'-dicarboxyphenyl)-5,6-dicarboxybenzothiazole dianhydride, 2,2',3,3'-benzophenone tetracarboxylic dianhydride, 2,3 3',4'-benzophenone tetracarboxylic dianhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BTDA), 2,2',3,3'-biphenyl tetracarboxylic dianhydride, 2,3,3',4'-biphenyl tetracarboxylic dianhydride, 4,4'-thio-diphthalic anhydride, bis(3,4-dicarboxyphenyl)sulfone dianhydride, bis(3,4-dicarboxyphenyl)sulfoxide dianhydride (DSDA), bis(3,4-dicarboxyphenyloxadiazole-1, 3,4)-Phenylene dianhydride, bis(3,4-dicarboxyphenyl)-2,5-oxadiazole-1,3,4-dianhydride, bis(3',4'-dicarboxydiphenyl ether)-2,5-oxadiazole-1,3,4-dianhydride, 4,4'-oxyphthalic anhydride (ODPA), bis(3,4-dicarboxyphenyl) thioether dianhydride, bisphenol A dianhydride (BPADA), bisphenol S dianhydride, bis-1,3-isobenzofurandione, 1,4-bis (4,4'-oxyphthalic anhydride)benzene, bis(3,4-dicarboxyphenyl)methane dianhydride, perylene-3,4,9,10-tetracarboxylic dianhydride, 1,3-bis-(4,4'-oxydiphthalic anhydride)benzene, 2,2-bis(3,4-dicarboxyphenyl)propane dianhydride, 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA), and 9,9-bis(trifluoromethyl)-2,3,6,7-xanthonestetracarboxylic dianhydride.

[0063] In one embodiment, the additional dianhydride used to form the polymer may include 1,2,5,6-naphthalenetetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, bicyclo-[2,2,2]-octene-(7)-2,3,5,6-tetracarboxylic-2,3,5,6-dianhydride, cyclopentadienyltetracarboxylic dianhydride, ethylenetetracarboxylic dianhydride, and pyromellitic dianhydride (PMDA). Tetrahydrofuran tetracarboxylic dianhydride, 2,6-dichloronaphthalene-1,4,5,8-tetracarboxylic dianhydride, 2,7-dichloronaphthalene-1,4,5,8-tetracarboxylic dianhydride, 2,3,6,7-tetrachloronaphthalene-1,4,5,8-tetracarboxylic dianhydride, phenanthrene-1,8,9,10-tetracarboxylic dianhydride, pyrazine-2,3,5,6-tetracarboxylic dianhydride, benzene-1,2,3,4-tetracarboxylic dianhydride, and thiophene-2,3,4,5-tetracarboxylic dianhydride.

[0064] In one embodiment, the additional dianhydride used to form the polyimide may include alicyclic dianhydrides such as cyclobutane-1,2,3,4-tetracarboxylic dianhydride (CBDA), 1,2,4,5-cyclohexanetetracarboxylic dianhydride, 1,2,3,4-cyclohexanetetracarboxylic dianhydride, 1,2,3,4-tetramethyl-1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,2,3,4-cyclopentanetetracarboxylic dianhydride (CPDA), hexahydro-4,8-bridged ethylene-1H,3H-benzo[1,2-c:4,5-c']difuran-1,3,5,7-tetraone (BODA), 3-(carboxymethyl)-1,2,4-cyclopentanetricarboxylic acid 1,4:2,3-dianhydride (TCA), and meso-butane-1,2,3,4-tetracarboxylic dianhydride.

[0065] In one embodiment, the polyimide is primarily derived from pyromellitic dianhydride (PMDA), 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), and 4,4'-oxydiphthalic anhydride (ODPA). In one embodiment, the polyimide may have a weight-average molecular weight (Mi) of 100,000 Daltons or greater, 150,000 Daltons or greater, 200,000 Daltons or greater, or 250,000 Daltons or greater. w ). Imidization catalyst

[0066] In one embodiment, an imidization catalyst (sometimes referred to as an "imidization promoter") can be used as a conversion chemical that helps lower the imidization temperature and shorten the imidization time for the formation of polyimides. The polyamic acid casting solution of the present invention comprises a polyamic acid solution in combination with a certain amount of conversion chemicals. Conversion chemicals found to be usable in the present invention include, but are not limited to: (i) one or more dehydrating agents and / or co-catalysts, such as aliphatic anhydrides (acetic anhydride, trifluoroacetic anhydride, propionic anhydride, monochloroacetic anhydride, bromohexanide, etc.) and aromatic anhydrides; and (ii) one or more imidization catalysts, such as aliphatic tertiary amines (triethylamine, etc.), aromatic tertiary amines (dimethylaniline, N,N-dimethylbenzylamine, etc.), and heterocyclic tertiary amines (pyridine, α-, β-, γ-methylpyridine, 3,5-dimethylpyridine, 3,4-dimethylpyridine, isoquinoline, etc.) and guanidines (e.g., tetramethylguanidine). In one embodiment, the imidization catalyst does not include diazoles. Other available dehydrating agents may include diacetyl oxide, butyryl oxide, benzoyl oxide, 1,3-dichlorohexylcarbodiimide, N,N-dicyclohexylcarbodiimide, benzenesulfonyl chloride, thionyl chloride, and phosphorus pentachloride. In some embodiments, the dehydrating agent may also act as a catalyst to enhance the reaction kinetics of imidization. Anhydride dehydrating materials are typically used in a slight molar excess of the amount of amyl acid groups present in the polyamic acid solution. In one embodiment, the amount of dehydrating agent used is typically about 2.0 to 4.0 mol / equivalent of polyamic acid units. Typically, a considerable amount of tertiary amine catalyst is used. The ratio of these catalysts and their concentration in the polyamic acid solution will affect the imidization kinetics and membrane properties. Polyimide membranes having substantially chemically transformed polyimides may have an imidization catalyst present in the polyimide membrane in an amount ranging from 1 part / billion parts (ppb) to 1 wt%, 10 ppb to 0.1 wt%, or 100 ppb to 0.01 wt%. Corona-resistant composite filler

[0067] The polymer film disclosed herein comprises an electrically insulating, corona-resistant composite filler. In one embodiment, the corona-resistant composite filler may have an organic component and an inorganic ceramic oxide component, wherein the weight ratio of the organic component to the inorganic ceramic oxide component is from 0.01:1 to 1:1. In some embodiments, the weight ratio of the organic component to the inorganic ceramic oxide component may be within the range of any two of the following numbers: 0.01:1, 0.05:1, 0.1:1, 0.2:1, 0.3:1, 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, and 1:1. In one embodiment, at least a portion of the organic component may comprise an organosiloxane portion or an organometaloxane portion (e.g., organozirconate, organotitanate, organoaluminate).

[0068] In one embodiment, the inorganic ceramic oxide component may include ceramic oxides of Al, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ge, Zr, Nb, Mo, Sn, Sb, Ta, W, Pb, Ce, and mixtures thereof. In an exemplary embodiment, the inorganic ceramic oxide component may include silicon dioxide, alumina, titanium dioxide, zirconium oxide, iron, calcium, or mixtures thereof. In one embodiment, the inorganic ceramic oxide component comprises silicon dioxide, alumina, or mixtures thereof. In one embodiment, the inorganic ceramic oxide component is alumina.

[0069] In one embodiment, the electrically insulating and corona-resistant composite filler is an inorganic nitride, such as boron nitride, aluminum oxide nitride, gallium nitride, titanium nitride, silicon nitride, and mixtures thereof.

[0070] In one embodiment, the organic component of the corona-resistant composite filler material is selected primarily to provide or improve the dispersibility of the corona-resistant composite filler material into a specific solvated polymer matrix or polymer matrix precursor. In some embodiments, the organic component of the corona-resistant composite filler material is selected to reduce hygroscopicity on the inorganic ceramic oxide component. For any particular solvent system selected, common skills and experimentation may be necessary to optimize the organic component. In some embodiments, the organosiloxane portion is any of n-octylsilane or its structural isomers. In some embodiments, the corona-resistant composite filler is an inorganic ceramic oxide without an organic component. In another embodiment, the organic component is a coating on the inorganic ceramic oxide component. The organic component may or may not cover the entire surface of the inorganic ceramic oxide component.

[0071] In one embodiment, the electrically insulating, corona-resistant composite filler is present in an amount between and including any two of the following figures based on the total weight of the polyimide film: 5, 10, 15, 20, 25, and 30% by weight. In one embodiment, the corona-resistant composite filler is present in an amount ranging from 5 to 30, 5 to 25, or 5 to 20% by weight based on the total weight of the polyimide film. In one embodiment, the filler content of the polyimide film is determined using ASTM D5630.

[0072] In one embodiment, the corona-resistant composite filler may have a median particle size of 0.1 to 5 µm, wherein at least 80, 85, 90, 92, 94, 95, 96, 98, 99, or 100 percent of the dispersed corona-resistant composite filler is within the size range defined above. In an example embodiment, the filler particle size distribution is 1 µm or less, or 0.5 µm or less. 99 The median particle size can be measured using a Horiba LA-930 particle size analyzer (Horiba Instruments, Inc., Irvine, California). DMAc can be used as the carrier fluid. In some embodiments, the corona-resistant composite filler is a nanofiller. The term "nanofiller" is intended to mean a filler having at least one dimension less than 1000 nm (i.e., less than 1 µm).

[0073] In one embodiment, the polymer film additionally comprises a dispersant. In some embodiments, the polyimide film additionally comprises a dispersant in an amount ranging from 1 to 100 weight percent based on the inorganic ceramic oxide component. In some embodiments, the dispersant is selected from the group consisting of phosphorylated polyethers, phosphorylated polyesters, and mixtures thereof. In another embodiment, the dispersant is an alkyl ammonium salt of polyethylene glycol ester. In another embodiment, the dispersant is selected from the group consisting of: Disperbyk 180, an alkyl ammonium salt of polyethylene glycol ester; Disperbyk 111, a phosphorylated polyester; Byk W-9010, a phosphorylated polyester; or mixtures thereof (all available from Byk-Chemie GmBH, Wessel, Germany). In another embodiment, the dispersant is Solplus D540, a phosphorylated ethylene oxide / propylene oxide copolymer, available from Lubrizol, Inc., Cleveland, Ohio. In yet another embodiment, the dispersant is a mixture of any of the above dispersants. In some embodiments, the dispersant is an aromatic polyamic acid or an aromatic polyimide. In another embodiment, the dispersant is a polyalkylene ether, such as polybutane glycol and polyethylene glycol. Typically, aromatic polyamic acids or aromatic polyimides have high-temperature stability and are therefore largely retained in the polyimide. Dispersants such as polyalkylene ethers, on the other hand, have low-temperature stability and are mostly decomposed or burned off at the temperatures used in the imidization process.

[0074] When the insulating material is a multilayer polyimide film, filler may be present in one or more of these layers. The properties of the filler in each layer can be selected independently. In one embodiment, the insulating material is a bilayer polyimide film consisting of a polyimide core layer and thermoplastic polyimide layers, and only one of these layers contains filler. In another embodiment, the insulating material is a trilayer polyimide film consisting of a polyimide core layer and two outer thermoplastic polyimide layers, and only the core layer contains filler. In yet another embodiment, the insulating material is a trilayer polyimide film consisting of a polyimide core layer and two outer thermoplastic polyimide layers, and only the outer layers contain filler.

[0075] In the case of multilayer polyimide films, the presence of fillers in the outermost layer may affect the final properties of the film, such as adhesion to metal surfaces, pressure resistance, and residual solvent content in the multilayer film. Base film strip

[0076] In one embodiment, the base film tape includes a polymer core layer and at least one first thermoplastic polymer outer layer adhered to a first side of the polymer core layer. In one embodiment, the base film tape includes a second thermoplastic polymer outer layer adhered to a second side of the polymer core layer. In one embodiment, the base film tape includes one or more thermoplastic polymer layers. In one embodiment, the base film tape can be used as an insulating wrapping for an electrically insulating conductor. In one embodiment, the polymer core may comprise polyimide (PI), poly(amide-imide) (PAI), polyaryletherketone (PAEK), polyphenylene sulfide (PPS), polyphenylene sulfone (PPSU), polyethersulfone (PES), polyetherimide (PEI), or mixtures thereof.

[0077] In one embodiment, a polyimide film for a polymeric core or thermoplastic (outer) layer can be produced by combining a diamine and a dianhydride (monomer or other polyimide precursor form) with a solvent to form a polyamic acid (also known as polyamide acid) solution. The dianhydride and diamine can be combined in a molar ratio of about 0.90 to 1.10. The molecular weight of the polyamic acid formed therefrom can be adjusted by regulating the molar ratio of the dianhydride to the diamine.

[0078] In one embodiment, the polyamic acid casting solution is derived from a polyamic acid solution. The polyamic acid casting solution and / or the polyamic acid solution are combined with conversion chemicals such as: (i) one or more dehydrating agents, such as aliphatic anhydrides (acetic anhydride, etc.) and / or aromatic anhydrides; and (ii) one or more catalysts, such as aliphatic tertiary amines (triethylamine, etc.), aromatic tertiary amines (dimethylaniline, etc.), and heterocyclic tertiary amines (pyridine, methylpyridine, isoquinoline, etc.). The anhydride dehydrating material is typically used in a molar excess relative to the amount of amic acid groups in the polyamic acid. The amount of acetic anhydride used is typically about 2.0 to 4.0 mol / equivalent (repeating unit) of polyamic acid. Typically, a comparable amount of tertiary amine catalyst is used. The filler, dispersed or suspended in a solvent as described above, is then added to the polyamic acid solution.

[0079] In one embodiment, the polyamic acid solution is dissolved in an organic solvent at a concentration of about 5.0 or 10% by weight to 15, 20, 25, 30, 35, or 40% by weight. In one embodiment, a slurry comprising filler is prepared, wherein the slurry has a solids content in the range of 0.1 to 70, 0.5 to 60, 1 to 55, 5 to 50, or 10 to 45% by weight. The slurry may be milled using a ball mill or may not be milled to achieve a desired particle size. The slurry may be filtered or may not be filtered to remove any residual large particles. The polyamic acid solution can be prepared by methods well known in the art. The polyamic acid solution may be filtered or may not be filtered. In some embodiments, the solution is mixed with a filler slurry in a high-shear mixer. When the polyamic acid solution is prepared with a slight excess of diamine, an additional dianhydride solution may or may not be added to increase the viscosity of the mixture to a desired level for film casting. The amounts of polyamic acid solution and filler slurry can be adjusted to achieve a desired loading level in the cured film. In some embodiments, the mixture is cooled to below 10°C and mixed with conversion chemicals before casting.

[0080] The solvated mixture (polyamic acid casting solution) can then be cast or applied to a support (such as a ring belt or drum) to obtain a partially imidized gel film. Alternatively, it can be cast onto a polymer carrier such as PET, other forms of Kapton® polyimide film (e.g., Kapton® HN or Kapton® E film), or other polymer carriers. The gel film can be peeled from the drum or belt, placed on a tenter frame, and cured in an oven using convective and radiant heat to remove the solvent and complete imidization to a solids level greater than 98%. The film can then be separated from the support, oriented (e.g., by tenter frame), and continuously heated (dried and cured) to provide a substantially chemically converted polyimide film.

[0081] Available methods for producing polyimide films are found in U.S. Patent Nos. 5,166,308 and 5,298,331, all of which are incorporated herein by reference for the full extent of their teachings. Many variations are also possible, such as... (a) A method in which a diamine component and a dianhydride component are premixed together and then the mixture is added in batches to a solvent while being stirred. (b) A method in which a solvent is added to a stirred mixture of a diamine and a dianhydride component. (Opposite to (a) above) (c) A method in which a diamine is dissolved separately in a solvent and then a dianhydride is added thereto at a ratio that allows control of the reaction rate. (d) A method in which a dianhydride component is dissolved separately in a solvent and then an amine component is added thereto at a ratio that allows control of the reaction rate. (e) A method in which the diamine component and the dianhydride component are dissolved in a solvent, respectively, and then the solutions are mixed in a reactor. (f) A method in which a polyamic acid having an excess of amine component and another polyamic acid having an excess of dianhydride component are pre-formed, and then reacted with each other in a reactor, particularly in such a way as to produce a non-random or block copolymer. (g) A method wherein a specific portion of the amine component is first reacted with the dianhydride component, and then the remaining diamine component is reacted, or vice versa. (h) A method in which a conversion chemical (catalyst) is mixed with a polyamic acid to form a polyamic acid casting solution and then cast to form a gel film. (i) A method in which the components are added, in part or in whole, in any order to a portion or all of a solvent, wherein any part or in whole of any component may be added as a solution in a portion or all of the solvent. (j) A method in which one of the dianhydride components is first reacted with one of the diamine components to obtain a first polyamic acid. Then, another dianhydride component is reacted with another amine component to obtain a second polyamic acid. The amic acids are then combined in any of a number of ways prior to membrane formation.

[0082] In one embodiment, the filler is first dispersed in a solvent to form a slurry. The slurry is then dispersed in a polyamic acid solution. In one embodiment, the concentration of the filler relative to the polyimide (in the final film) is in the range of 10 vol% to 50 vol%, 15 vol% to 45 vol%, 15 vol% to 40 vol%, 20 vol% to 35 vol%, or 25 vol% to 30 vol%. In another embodiment, the concentration of the filler relative to the polyimide (in the final film) is at least 10 vol%, at least 15 vol%, at least 20 vol%, or at least 25 vol%. The composition of the cured film can be calculated from the composition of the components in the mixture, excluding the DMAc solvent (which is removed during curing) and taking into account the removal of water during the conversion of the polyamic acid to the polyimide.

[0083] In one embodiment, the filled polyamic acid casting solution is a blend of a polyamic acid solution and a filler. In this casting solution, the filler is present at a concentration ranging from 0.1 vol% to 70 vol%, 1 vol% to 60 vol%, 2 vol% to 50 vol%, 5 vol% to 45 vol%, or 5 vol% to 40 vol%. In one embodiment, the filler is first dispersed in the same polar aprotic solvent (e.g., DMAc) used to prepare the polyamic acid solution. Optionally, a small amount of the polyamic acid solution may be added to the filler slurry to increase the viscosity of the slurry. Optionally, a dispersant or dispersing agent may be added to aid dispersion or modify the rheological properties of the slurry.

[0084] Fillers can be co-blended into a specific solvated polymer matrix or polymer matrix precursor using any commonly used technique, such as batch mixing with one or more solvents, dry mixing, or continuous mixing with one or more solvents. Known parameters such as the order of feedstock addition, mixing rate, shear rate, type of mixing blades (e.g., shear blades), mixing time, temperature, and pressure affect the final degree of mixing between the filler and the matrix material.

[0085] In one embodiment, blending the filler slurry with a polyamic acid solution to form a filled polyamic acid casting solution is accomplished using high-shear mixing. In this embodiment, if the final film contains more than 50% filler by volume, the film may be too brittle and may not have sufficient flexibility to form independent, mechanically strong, flexible sheets.

[0086] In one embodiment, the casting solution may further contain any of a number of additives, such as processing aids (e.g., oligomers), antioxidants, light stabilizers, flame retardants, antistatic agents, heat stabilizers, UV absorbers, or various reinforcing agents.

[0087] In some embodiments, a co-extrusion process can be used to form a multilayer polyimide film, wherein an inner core layer is sandwiched between two outer layers. In this process, a finished polyamic acid solution is filtered and pumped into a slot die, where the flow is separated in such a way as to form a first and second outer layer of a three-layer co-extruded film. In some embodiments, a second stream of polyimide is filtered and then pumped into a casting die in such a way as to form an intermediate polyimide core layer of a three-layer co-extruded film. The flow rate of the solution can be adjusted to achieve a desired layer thickness. In one embodiment, strong adhesion between layers can be achieved using co-extrusion. In another embodiment, stronger adhesion between layers in a multilayer polyimide film can be achieved compared to a coating method in which a thermoplastic polyamic acid solution is coated onto a polyimide core film (which has already been imidized) and subsequently cured. In yet another embodiment, stronger adhesion between layers in a multilayer polyimide film can be achieved compared to a lamination method in which a thermoplastic polyimide film is laminated onto a polyimide core film.

[0088] In some embodiments, the multilayer film is prepared by simultaneously extruding a first thermoplastic outer layer, a core layer, and a second thermoplastic outer layer. In some embodiments, these layers are extruded using a single-cavity or multi-cavity extrusion die. In another embodiment, the multilayer film is produced using a single-cavity die. If a single-cavity die is used, the laminar flow of the stream should have a sufficiently high viscosity to prevent mixing of the streams and to provide uniform delamination. In some embodiments, the multilayer film is prepared by casting from a slot die onto a moving stainless steel strip. In one embodiment, the strip is then passed through a convection oven to evaporate the solvent and partially imidize the polymer to produce a "green" film. The green film can be peeled off from the cast strip and rolled up. The green film can then be passed through a tenter oven to produce a fully cured polyimide film. In some embodiments, shrinkage can be minimized during tentering by restraining the film along its edges (i.e., using clips or pins).

[0089] In one embodiment, the outer layer of the multilayer membrane may also be applied to the core layer during an intermediate manufacturing stage in the production of a polyimide membrane, such as a gel membrane or a biofilm.

[0090] When forming a polyimide film, the term "gel film" refers to a sheet of polyamic acid loaded with volatiles, primarily solvents, to the extent that the polyamic acid is in a gel-swelled or rubber-like state, and can be formed during a chemical conversion process. The volatile content is typically in the range of 70% to 90% by weight of the gel film, and the polymer content is typically in the range of 10% to 30% by weight. The final film becomes "self-supporting" during the gel film stage. It can be peeled from the support to which it has been cast and heated to its final curing temperature. Gel films typically have an amic acid to imide ratio between 10:90 and 50:50, most often 30:70.

[0091] The gel film structure can be prepared by the method described in U.S. Patent No. 3,410,826. This patent discloses mixing chemical converting agents and catalysts, such as lower fatty acid anhydrides and tertiary amines, into a polyamic acid solution at low temperatures. This is followed by casting the polyamic acid solution as a film onto a casting drum. After casting, the film is gently heated, for example, at 100°C, to activate the converting agents and catalysts, thereby transforming the cast film into a polyamic acid / polyimide gel film.

[0092] Another type of polymer film is the "green film," which, in the case of polyimide films, is a mixture of polyamic acid and polyimide and can be formed during thermal conversion. Green films typically contain approximately 50% to 75% by weight of polymer and 25% to 50% by weight of solvent. Generally, it should be strong enough to be substantially self-supporting. Green films can be prepared by casting a polyamic acid solution into a film form onto a suitable support such as a casting drum or tape and removing the solvent by gentle heating at up to 150°C. A low proportion of amic acid units in the polymer (e.g., up to 25%) can be converted into imide units.

[0093] The application of the polymer film of the present invention can be achieved in any number of ways. Such methods include coating the film using a slot die, dip coating, or wet roller coating, followed by metering with a doctor blade, doctor blade roller, extrusion roller, or air knife. The coating can also be applied by brushing or spraying. By using such techniques, both single-sided and double-sided coated laminates can be prepared. In the preparation of double-sided coated structures, the coating can be applied to both sides of the polymer simultaneously or sequentially before the curing and drying stages of the polymer.

[0094] Electrically insulating, corona-resistant composite fillers (dispersions or colloids) can be added at several points during the preparation of polyimide films. In one embodiment, the colloid or dispersion is incorporated into a prepolymer having a Brookfield solution viscosity in the range of about 50-100 poise at 25°C. "Prepolymer" is intended to refer to a lower molecular weight polymer, typically made with a small stoichiometric excess (about 2%-4%) of a diamine monomer (or an excess of a dianhydride monomer). In alternative embodiments, the colloid or dispersion can be combined directly with the monomer, and in this case, polymerization occurs during the reaction in the presence of the filler. In another embodiment, the colloid or dispersion can be combined with the "finished" high-viscosity polyimide. During this "in-situ" polymerization, the monomer may have an excess of either monomer (diamine or dianhydride). Monomers can also be added in a 1:1 ratio. In cases where the monomer is added in excess of amine (case i) or dianhydride (case ii), if necessary, the increase in molecular weight (and solution viscosity) can be achieved by adding an incremental amount of additional dianhydride (case i) or diamine (case ii) at a stoichiometric ratio of dianhydride to amine close to 1:1.

[0095] The thickness of the base film strip can be adjusted according to the intended purpose or end-application specifications of the membrane. In one embodiment, the base film strip has a total thickness ranging from 14 to 95 µm, 14 to 80 µm, 16 to 65 µm, 18 to 50 µm, or 20 to 50 µm. In one embodiment, the polymer core layer has a thickness ranging from 12 µm to 75 µm, 12 to 50 µm, or 12 to 25 µm. In one embodiment, each of the first and second (when present) thermoplastic outer layers has a thickness ranging from 1 µm to 10 µm, 1 to 8 µm, or 1 to 6 µm. In one embodiment, the thicknesses of the first and second thermoplastic outer layers can be the same or different; for example, one layer can be 3 µm, 4 µm, or 5 µm thicker than the other layer.

[0096] In one embodiment, the polymer core layer, the first thermoplastic polymer outer layer, and the second thermoplastic polymer outer layer each have a Tc of 200°C or higher, 205°C or higher, 210°C or higher, 215°C or higher, 220°C or higher, or 225°C or higher. g In one embodiment, the polymer core layer, the first thermoplastic polymer outer layer, and the second thermoplastic polymer outer layer each have a T value in the range of 200°C to 250°C, 205°C to 245°C, 210°C to 240°C, or 215°C to 235°C. g In one embodiment, the T of the polymer core layer g T than one or more thermoplastic polymer outer layers gThe temperature is at least 50°C, 70°C, 100°C, or 120°C. In one embodiment, The ratio of the bending radius (R) to the width (W) of the insulated conductor is within the range of 0.8:1 to 2:1, 1:1 to 2:1, 1.2:1 to 1.9:1, or 1.4:1 to 1.9:1. In one embodiment, the base film tape has 200 J / m 2 Or a larger first thermoplastic polymer outer layer relative to the conductive core G Ic In one embodiment, the average ultimate strain of the polymer core layer and the first thermoplastic polymer outer layer is 60% or greater. In one embodiment, the ratio of the tensile modulus of the first thermoplastic polymer outer layer to the tensile modulus of the polymer core layer is 0.7:1 or greater. In one embodiment, the polyimide film may have other desired properties, such as: (a) a dielectric strength of 3 kV / mil or greater (e.g., as determined using ASTM D149), (b) a thermal rating of 200°C or greater, (c) a residual volatile content of less than 1% by weight (excluding water), and / or (d) improved withstand voltage life under AC, DC, or pulse width modulation conditions compared to unfilled insulation applied at the same thickness (e.g., as determined using ASTM D2275). These properties may be tested according to industry-known standard procedures, such as those disclosed by ASTM (e.g., D2305) or UL. Adhesion promoter

[0097] In one embodiment, a thin layer of adhesion promoter material can be applied to the conductive element before the insulating material is applied. Using an adhesion promoter can increase the measured G between the two material layers. Ic In one embodiment, the adhesion promoter is applied as a coating solution in the form of a solution or dispersion in a liquid medium or carrier. The liquid medium or carrier may be based on aqueous and / or organic solvents, such as ketones, esters, ethers, aromatic hydrocarbons, aliphatic hydrocarbons, lactones, amides, alcohols, mixtures thereof, or water. The coating solution may be applied as a single coating and dried. However, additional coatings may also be applied. If multiple coatings are applied, a curing step may be performed between each application step.

[0098] In the exemplary embodiments disclosed herein, the application of the coating solution can be performed in any manner. Such methods include using stencil or dip coating, brush coating, or spray coating.

[0099] The non-volatile solid contents of a coating solution can be cured once applied to a substrate and dried. In this context, "curing" refers to a process that alters the state and / or structure of the non-volatile solid contents, a process typically but not necessarily triggered by variables such as moisture, temperature, and / or the addition of chemicals such as alkalis, acids, or other catalysts. The curing process can be partial or complete in relation to the conversion of reactive groups, such as silanol groups, contained in the coating solution. The conversion of reactive groups can occur through several reaction mechanisms, which in one embodiment may include a condensation reaction driven by humidity / moisture at ambient temperature. In one embodiment, the dried coating solution is cured at ambient humidity and temperature for 24 hours or less. In another embodiment, heat is applied to accelerate the curing process. The curing time can be shortened by adding more moisture or one or more suitable catalysts, such as acids, alkalis, or metal-based compounds, or mixtures thereof. Several methods can be combined to accelerate the curing process.

[0100] When applied to a conductive element, the cured release coating can have an average dry coating thickness of less than 1 µm. In one embodiment, the average dry coating thickness is less than 0.5 µm, less than 0.25 µm, or less than 0.1 µm.

[0101] The coating solution may contain one or more siloxane monomers, oligomers, or polymers. Each siloxane oligomer or polymer may have a branched or linear structure, or both. In one embodiment, the siloxane is in the form of SiR. 1 X 1 X 2 X 3 Silanes or mixtures of silanes. Substituent R 1 It can be alkyl or aryl, and supports additional substituents or functional groups, such as vinyl, alkoxy, amino, hydroxyl, hydrogen, mercapto, halogen, epoxy, and cyano. The alkyl group can be selected from C1-C20 alkyl groups, preferably C1-C8 alkyl groups. The aryl group can be selected from C6-C18 aryl groups, preferably phenyl. The substituent X can be the same or different, and can be selected from amino, acetoxy, alkoxy, alkyl, allyl, hydroxyl, hydrogen, vinyl, enoxy, and oxime functional groups. The alkoxy group can be selected from C1-C8 alkoxy groups, especially methoxy or ethoxy. In some embodiments, at least one or more hydroxyl or alkoxy groups are directly attached to the silicon atom.

[0102] In one embodiment, the coating solution contains one or more silanes that can react partially or completely to produce crosslinking with themselves or with other present silanes and / or with surfaces in contact with the coating solution. Electrically insulating conductor

[0103] In one embodiment, an electrically insulating conductor with an electrically insulating, corona-resistant composite filler can be used as a wire wrapping. Suitable materials to be wrapped include bare conductors, conductors coated in an enamel (such as polyester-imide (PEI), polyamide-imide (PAI), a PEI / PAI combination, or polyimide enamel), conductors coated with extruded resin, or conductors coated with a film tape. In some embodiments, the wire wrapping may include additional layers, such as an adhesive layer or abrasion-resistant layer. The film or sheet of the wire wrapping can be cut into narrow widths to provide a tape. These tapes can then be wound around the conductor in a helical, overlapping, or longitudinal manner, with or without overlap. The amount of overlap can vary depending on the angle of the wrapping. In one embodiment, the overlap is 20% or more, 45% or more, or 52% or more. In one embodiment, the overlap does not exceed 70%. The tension used during the wrapping operation can also vary widely, ranging from just enough to prevent wrinkling to enough to stretch and contract the tape. Even at low tension, tight wrapping is possible because the tape will typically shrink under the influence of heat during any subsequent heat-sealing operation. Heat sealing of the tape can be achieved by processing the tape-wrapped conductor at temperatures and times sufficient to fuse the bonding layer to other layers in the composite material. The required heat-sealing temperatures typically range from 240°C, 250°C, 275°C, 300°C, 325°C, or 350°C to 375°C, 400°C, 425°C, 450°C, 475°C, or 500°C, depending on the insulation thickness, the gauge of the metallic conductor, the speed of the production line, and the length of the seal. Parameters such as the absolute humidity level and temperature of the ambient atmosphere, wire tension, wrapping angle, heating and cooling rates, and the means of applying heat (e.g., convection, radiation, or induction) and pressure can affect the performance of the final wire insulation material.

[0104] One advantage of using a corona-resistant insulating film on a conductor is that the resulting structure has a significantly thinner overall diameter compared to similar solutions using non-corona-resistant insulating films, which generally allows for savings in both space and weight in any given application.

[0105] The encapsulated conductor can possess certain desired properties. The desired characteristics include: (a) a thermal rating of 200°C or greater when applied to a copper conductor; (b) a residual solvent content of 1% by weight or less; (c) a breakdown voltage of 2 kV or greater that retains at least 50% of its initial value after: (i) the wrapped conductor elongates by at least 5%; (ii) bending at an R / W ratio in the range of 0.8:1 to 2:1; (iii) exposure to chemicals (such as automotive transmission fluid (ATF) or other motor cooling fluids); or (iv) thermal exposure to temperatures of 200°C or higher; (d) no visible damage when bent 180° along the edge or flat around a mandrel with a diameter twice the conductor width; (e) no visible damage when exposed to at least 200°C for at least 30 minutes, or when additionally first bent flat or along the edge, or when additionally first elongated by at least 10%; (f) at least 30% elongation at break; and (g) [followed by the following description:] After elongation of at least 20% or when additionally subjected to thermal aging at at least 150°C for at least 30 minutes, the following properties must be observed: (h) a certain coefficient of static friction; (i) a certain partial discharge initiation voltage of 700 V or higher at a threshold of 20 picocoulombs under ambient conditions; (j) a certain abrasion / scratch resistance; and (k) a certain degree of concentricity. Concentricity is a measurement of the position of the conductor's center relative to the geometric center of the surrounding insulation. The more uniform the insulation around the conductor, the better the match between the conductor's center and the geometric center of the surrounding insulation. A match where the positions of these two values ​​are as close as possible is preferred. Testing for any of these properties can be performed according to industry-known standard procedures such as IEC 60851, ASTM (e.g., using procedures as described in ASTM D1676), or ANSI / NEMA MW 1000.

[0106] The advantageous features of the invention can be observed by referring to the following examples, which are not limiting of the invention. Unless otherwise specified, all parts and percentages are by weight. Example Test methods thickness

[0107] The membrane thickness was determined by measuring five locations on the membrane profile using a contact-type FISCHERSCOPE MMS PC2 modular measurement system thickness gauge (Fisher Technology Inc., Windsor, CT, Windsor, Connecticut). Glass transition temperature

[0108] Glass transition temperature (T) g The measurements were performed using Dynamic Mechanical Analysis (Q800 DMA, TA Instruments, New Castle, DE) following the IPC-TM-650 test method. Prior to testing, the test specimens were conditioned at 23°C and 50% relative humidity for at least 24 hours. Heat was applied to dry air at a rate of 5°C / min, and the value of the tanδ peak was recorded. Peel test performed on smooth copper

[0109] A polished 110 copper sheet (4 × 8 × 0.08, McMaster-Carl, Elmhurst, Illinois) was used for peel testing. Surface roughness was analyzed using a 3D laser scanning confocal microscope (VK-X260K, Keyence Corp. of America, Itasca, IL). Imagery was performed at 11 locations using a 50x objective lens (287 µm × 216 µm FOV). The polished copper sheet exhibited the following surface roughness: S a = 21nm; S dr = 0.41%.

[0110] First, immerse the copper sheet sample in an acetic acid pickling solution (acetic acid / deionized water (10 / 90 v / v), containing NaCl (1.75 wt%)) for 30 seconds, rinse thoroughly with deionized water, and blot dry with a paper towel. Use the control sample as is (without adhesion promoter). Apply the adhesion promoter by transferring excess solution onto a horizontal copper substrate to cover the entire surface. After 30 seconds, tilt the copper sheet at a 90-degree angle to allow excess solution to flow from the surface onto the paper towel. Air dry the copper sheet in an upright position under ambient conditions for at least 30 minutes.

[0111] The polyimide film was cut into test strips (0.5 × 8”) using a JDC precision sample cutter (model JDC 5-10, Thwing-Albert Instruments, West Berlin, NJ).

[0112] Assemble the test sample as follows: Place a 1.5 × 4” PFA (PerFluoroAlkoxy, 1 mil) film on top of the copper sheet to prevent adhesion between the test strips and the copper (creating peel arms). Four polyimide test strips (0.5 × 8”) are spaced evenly on the copper sheet. In some cases, the thickness of the test strips is increased by placing a second or third strip on top of the first. Apply a Kapton® tape to the bottom of the sample to hold the multilayer test strips in place. Cover the film strips with a PTFETeflon® sheet (3 mils). Clamp the sample between Pacopad™ high-temperature Thermopads™ and place them inside a 12 × 12” mirror-polished stainless steel plate lined with a 12 × 12” Kapton® HN film.

[0113] The membrane samples were laminated by loading the assembled test samples into a vacuum press (model 1553 / 10 / 17 / 32755 / HELC, OEM Press Systems Inc., Fullerton, CA) with a pressure plate preheated to 120°C. A vacuum was applied for 10 minutes with a force of 500 lbs, and the test samples were heated to the final temperature and pressure (typically 310°C, 16,000 lbs (500 psi) for 1 hour, unless otherwise specified). The samples were then cooled to room temperature under pressure.

[0114] Peel test according to ASTM D6862-11. Double cantilever beam test

[0115] The polyimide film was cut into test strips (0.5”) using a JDC precision sample cutter. To measure adhesion to aluminum, the test strips were cut to a length of 3” and positioned on a 0.125 × 0.5 × 4” 6061 aluminum beam, leaving a 1” gap on one side of the beam. A second aluminum beam was placed on the film, and Kapton® tape was wrapped around the sandwich structure (at both ends) to maintain layer alignment.

[0116] Position the samples between PTFE Teflon® (3 mils) inside Pacopad™ high-temperature Thermopads™, placing them inside a 12 × 12” mirror-polished stainless steel plate lined with a 12 × 12” Kapton® HN membrane. Load the samples into a vacuum press with a pressure plate preheated to 120°C. Apply vacuum for 10 minutes, apply a force of 500 lbs, and heat the samples to the final temperature and pressure for 1 hour, then cool to room temperature under pressure.

[0117] The method described in BRK Blackman and AJ Kinloch, “Fracture Tests for Structural Adhesive Joints,” in “Fracture Mechanics Testing Methods for Polymers, Adhesives and Composites,” edited by A. Pavan, DR Moore, and JG Williams (Elsevier Sciences, Amsterdam), 2001, measures type I interlaminar fracture toughness (G). Ic For samples where no delamination occurs at the interface of the laminated layers, G Ic The value was reported as greater than 700 J / m 2 Furthermore, this interface is no longer considered an interface that can undergo adhesive failure. T-peel test

[0118] The film sample was cut into 3 × 6” pieces, and a 1 × 3” PFA (1 mil) was stacked between the tops of the samples to create a peel arm. The sample was laminated using the conditions described above for peel testing on smooth copper. Comparison Example 1

[0119] For Comparative Example 1 (CE1), a first polyamic acid solution "A" of monomer compositions ODPA (4,4'-oxyphthalic anhydride) / PMDA (pyromellitic dianhydride) (molar ratio 4:1) and 1,3-bis(4-aminophenoxy)benzene (RODA) was prepared by dissolving the diamine in DMAc under nitrogen with a mechanical stirrer, followed by the addition of dianhydride powder over a short period until a molar stoichiometric ratio of approximately 1:0.97 between the amine and the anhydride monomers was obtained. The polyamic acid solution was then completed by incrementally adding 6% by weight of PMDA solution in DMAc to obtain a maximum viscosity of 2500-3000 poise. A second polyamic acid solution "B" of monomer compositions BPDA 0.35 / PMDA 0.65 / PPD 0.13 / ODA 0.87 was prepared by following the procedure described above. Both polyamic acid solutions were co-cast on a stainless steel strip and then dried and imidized by heating in an oven. A polyimide trilayer ABA film (polyimide 10) with a total thickness of approximately 50 µm was obtained. The thickness of each layer A in the trilayer film was on the order of 5 to 6 µm, while the thickness of layer B was approximately 40 µm. The film's Tg... gThe temperature was approximately 220°C for layer A and approximately 350°C for layer B. The resulting film was then laminated onto the copper sheet as generally described above using the lamination conditions shown in Table 2. Peel tests were performed on the test samples, and the results are recorded in Table 2. Example 1

[0120] For Example 1 (E1), the CE1 membrane was used with an adhesion promoter. MEGUM™ W-3295 (DuPont, Wilmington, .D.) (aqueous single-coat adhesive) was diluted with deionized water to 1.0% by weight solids and applied to the copper as described above. The membrane was laminated at the same temperature and pressure as CE1, and a peel test was performed. Example 2

[0121] For Example 2 (E2), the membrane from CE1 was used with an adhesion promoter. PEDTMS (N-[3-(trimethoxysilyl)propyl]ethylenediamine, 1% v / v) was added to a methanol / deionized water (95 / 5 v / v) solution. The solution was shaken several times and aged overnight, then applied to copper as described above. The membrane was laminated at the same temperature and pressure as CE1, and a peel test was performed. Example 3

[0122] For Example 3 (E3), the membrane from CE1 was used with an adhesion promoter. APTMS ((3-aminopropyl)triethoxysilane, 1% v / v) was added to a methanol / deionized water (95 / 5 v / v) solution. The solution was shaken several times and aged overnight, then applied to copper as described above. The membrane was laminated at the same temperature and pressure as CE1, and a peel test was performed. Example 4

[0123] For Example 4 (E4), the AB bilayer of the membrane composition of CE1 was used with an adhesion promoter. MEGUM™ W-3295 was diluted with deionized water to 0.5% by weight solids and applied to copper as described above. The membrane was laminated at the same temperature and pressure as CE1, and a peel test was performed. Example 5

[0124] For Example 5 (E5), the membrane from CE1 was used with an adhesion promoter. 1% PEDTMS was used as described in E2. The membrane was laminated at the same temperature and pressure as CE1, and a peel test was performed. Example 6

[0125] For Example 6 (E6), the AB bilayer of the membrane composition of CE1 was used with an adhesion promoter. 1% MEGUM™ W-3295 was used as described in E1. The membrane was laminated at the same temperature and pressure as in CE1, and a peel test was performed. Example 7

[0126] For Example 7 (E7), the AB bilayer of the membrane composition of CE1 was used with an adhesion promoter. APTMS (0.25% v / v) was added to a methanol / deionized water (95 / 5 v / v) solution. The solution was shaken several times and aged overnight, then applied to copper as described above. The membrane was laminated at the same temperature and pressure as CE1, and a peel test was performed. Example 8

[0127] For Example 8 (E8), the membrane of CE1 was used without an adhesion promoter and laminated at a lower temperature than CE1 and the same pressure as CE1, and a peel test was performed.

[0128] Table 2 shows that the adhesion of the polyimide layer to the copper surface was significantly improved by applying adhesion promoters in the form of various silane materials, to the extent that in some cases the interface was no longer considered an interface likely to undergo adhesion failure. Furthermore, Table 2 shows that temperature is a more important variable than pressure in determining the effectiveness of the adhesion promoter. Table 2 Example 9

[0129] For Example 9 (E9), a first polyamic acid solution "A" of monomer compositions ODPA / PMDA (molar ratio 4:1) and RODA was prepared by dissolving the diamine in DMAc under nitrogen with a mechanical stirrer, followed by the addition of dianhydride powder over a short period until a molar stoichiometric ratio of approximately 1:0.97 between the amine and the anhydride monomers was obtained. The polyamic acid solution was then completed by incrementally adding 6% by weight of PMDA solution in DMAc to obtain a maximum viscosity of 2500–3000 poise. The polyamic acid solution was then cast onto a stainless steel tape and subsequently dried and imidized by heating in an oven. The resulting film (polyimide 8) had a thickness of approximately 50 µm and a To of approximately 230°C. g A double cantilever beam test was performed on the membrane to measure the gamma at the interface between the 6061 aluminum and the polyimide membrane. Ic . Comparison Example 2

[0130] For Comparative Example 2 (CE2), a polyimide 4 film was laminated with a 50 FEP film following a double cantilever beam test procedure, and the G at the interface between the two polymer films was measured. Ic . Example 11

[0131] For Example 11 (E11), a first polyamic acid solution "C" of monomer compositions ODPA / PMDA (molar ratio 4:1) and RODA / 1,6-diaminohexane (HMD) (molar ratio 2.33:1) was prepared by dissolving the diamine in DMAc under nitrogen with a mechanical stirrer, followed by the addition of dianhydride powder over a short period until a molar stoichiometric ratio of approximately 1:0.97 between the amine and the anhydride monomers was obtained. The polyamic acid solution was then completed by incrementally adding 6% by weight of PMDA solution in DMAc to obtain a maximum viscosity of 2500-3000 poise. A second polyamic acid solution "B" of monomer compositions BPDA 0.35 / PMDA 0.65 / PPD 0.13 / ODA 0.87 was prepared by following the procedure described above. Both polyamic acid solutions were co-cast on a stainless steel strip and then dried and imidized by heating in an oven. A polyimide trilayer ABA film (polyimide 11) with a total thickness of approximately 25 µm was obtained. The thickness of each layer A in the trilayer film is approximately 3 µm, while the thickness of layer B is approximately 19 µm. The T0 of this film... g The temperature was approximately 195°C for layer A and approximately 350°C for layer B. A double cantilever beam test was performed on the resulting films to measure the gamma at the interface between the 6061 aluminum and the polyimide film. Ic . Comparison Example 3

[0132] For Comparative Example 3 (CE3), following the T-peel test procedure, the E11 film was laminated onto a polyimide film composed of BPDA / PMDA (molar ratio 1.2:1) and ODA (4,4'-oxydiphenylamine). The BPDA / PMDA / / ODA film further contained 17 wt% alumina, which was added to the polyamic acid in the form of a 25 wt% slurry of alumina in DMAc, and the film had a thickness of approximately 25 µm. The G at the interface between the two polyimide films was measured. Ic . Example 12

[0133] For Example 12 (E12), two E11 films were laminated together following the T-peel test procedure. The G at the interface between the two polyimide films was measured. Ic . Example 13

[0134] For Example 13 (E13), the film of E11 was laminated onto polyimide film 12, prepared as described in Example 11, following a T-peel test procedure, but additionally containing 17% by weight alumina, which was added to the polyamic acid in the form of a 25% by weight slurry of alumina in DMAc. The G at the interface between the two polyimide films was measured. Ic . Table 3

[0135] Table 3 shows that E9 and E11 indicate that certain RODA-containing polyimide compositions exhibit very strong adhesion to 6061 aluminum surfaces.

[0136] Table 3 shows, in addition to E12 and E13, that some RODA-containing polyimide compositions also exhibit very strong adhesion to themselves.

[0137] Table 3 shows that CE2 has high T g The polyimide film has relatively weak adhesion to fluoropolymers FEP (which are typically used as adhesives), and therefore cannot withstand the previously described bending radius without visible damage.

[0138] Table 3 shows that CE3 has high T g The adhesion of polyimide films to metals and themselves is relatively weak in comparison, and therefore it is impossible for them to withstand the previously described bending radius without visible damage. Comparative Examples 4 to 6

[0139] For Comparative Examples 4 to 6 (CE4-CE6), polyethersulfone (PES Ultrason®, CS Hyde Co., Lake Villa, IL) test samples without any adhesion promoters were prepared for peel testing on smooth copper. Table 4 summarizes the testing of the PES films from CE4 to CE6. After lamination, these films peeled from the copper sheet with minimal effort; therefore, their peel strength was too low to be measured, and thus the material could not withstand the previously described flexural radius without visible damage. As a result, polyethersulfone is unsuitable as an insulating material for direct contact with conductive elements. Comparison Examples 7 to 10

[0140] For Comparative Examples 7 to 10 (CE7-CE10), polyetheretherketone (PEEK, CS Hyde Corporation) test samples containing an adhesion promoter (1 wt% MEGUM™ solution) were prepared for peel testing on smooth copper. The film was cut to a size (0.50 × 8”) using a JDC precision sample cutter. Half of the protective cover on the copper was removed, leaving a 2 × 8” exposed copper area. The copper was cleaned by wiping the surface with a nonwoven paper towel soaked in acetone, followed by wiping with a paper towel soaked in isopropanol. The exposed copper surface was allowed to dry under ambient conditions for 30 minutes. An excess of MEGUM™ solution (1 wt%) was aspirated onto the copper surface and allowed to stand for 30 seconds, then the plate was tilted 90 degrees so that the excess solution flowed from the surface onto the paper towel. The copper plate was air-dried in an upright position under ambient conditions for at least 30 minutes. The protective adhesive film was then removed, and the untreated side of the copper was cleaned by wiping the surface with non-woven paper towels soaked in acetone, followed by wiping with paper towels soaked in isopropyl alcohol. The copper surface was then allowed to dry under ambient conditions for 10 minutes.

[0141] Begin assembling the specimen using a 1.5 × 4” PFA (PerFluoroAlkoxy, 1 mil) membrane, placing it on top of the copper sheet to prevent adhesion between the test strips and the copper (creating a peel arm). Place four PEEK membrane test strips (0.5 × 8”) on the copper sheet (two on the MEGUM™ treated side and two on the untreated side). Apply a Kapton® tape to the bottom of the sample to hold the multilayer test strips in place. Cover the membrane strips with a polyimide sheet (NRF-250, 2 mil, Northern Composites, LLC, Hampton, NH) with an ultra-high temperature release film, with the release side facing the sample. Place polyimide 9 (3 mils) on top of the previous layer, and place an additional polyimide sheet with an ultra-high temperature release film on top of polyimide 9, with the release film facing upwards. Place the sample inside a custom-made sealable frame fixture with a vacuum port. The sample was loaded into the Carver M-type laboratory press, a vacuum was applied to the vacuum port, and the sample was heated from 100°C to the final lamination temperature (Table 4). After holding at the desired pressure for 10 minutes, the sample was cooled under pressure to 60°C.

[0142] Table 4 shows the lamination conditions used for the PEEK films. CE7-CE9 examined the effects of different pressures and peel arm thicknesses. CE10 involved a 5-minute rapid nitrogen purging during lamination, followed by a slow nitrogen purging (while a vacuum was applied) to further reduce the oxygen content. In each experiment laminating PEEK onto copper, partial spontaneous delamination of the film occurred after >10 minutes following lamination. Low adhesion to copper ruled out any additional peel force measurements. Table 4 The peel strength is less than the minimum peel strength measured on the Instron. Comparison Example 11

[0143] For Comparative Example 11 (CE11), a polyimide film composed of PMDA and ODA, additionally containing approximately 17% by weight of alumina and having a thickness of approximately 19 µm, was coated on one side with a fluoropolymer coating of tetrafluoroethylene-hexafluoropropylene copolymer (FEP). The dry thickness of the FEP coating resulted in a final film thickness of approximately 28 µm. The resulting film was then converted into a strip, spirally wrapped around a rectangular copper conductor (approximately 0.057” × 0.16”) with a 66% overlap (fluoropolymer side facing the conductor) and heat-sealed. The resulting insulated wire was then bent along the edges using an R / W of 1.1 and visually inspected for damage. Significant buckling and strip-by-strip delamination were observed in the bent areas of the wire. This result was expected based on the analysis from Table 1 (polyimide 3 and 50 FEP). Although both layers met the requirement of an elongation at break greater than 60%, the requirement of a tensile modulus ratio greater than 0.7:1 was not met. Comparison Example 12

[0144] For Comparative Example 12 (CE12), a first polyamic acid solution "A" of monomer compositions ODPA / PMDA (molar ratio 4:1) and RODA was prepared by dissolving the diamine in DMAc under nitrogen with a mechanical stirrer, followed by the addition of dianhydride powder over a short period until a molar stoichiometric ratio of approximately 1:0.97 between the amine and the anhydride monomers was obtained. The polyamic acid solution was then completed by incrementally adding 6% by weight of PMDA solution in DMAc to obtain a maximum viscosity of 2500–3000 poise. A second polyamic acid solution "B" of monomer compositions PMDA / BPDA (molar ratio 1.45:1) and ODA / PPD (molar ratio 1:1.49) was prepared by following the procedure described above. The two polyamic acid solutions were co-cast onto a stainless steel strip and then dried and imidized by heating in an oven. A polyimide trilayer ABA film with a total thickness of approximately 25 µm was obtained. The thickness of each layer A in the three-layer film is on the order of 2 to 3 µm. The three-layer polyimide film was then converted into a tape, which was wrapped around a rectangular copper conductor (approximately 0.06” × 0.12” in a 66% overlap spiral and heat-sealed. The resulting insulated wire was then bent along the edges using an R / W of 0.97 and visually inspected for damage. Significant instances of buckling and delamination were observed in the bent areas of the wire. This result was expected based on the analysis from Table 1. The composition “B” of the core layer of CE12 is the same as that of polyimides 6 and 7 and has a thickness of 19 µm, which is between the thickness of polyimide 6 (12 µm) and the thickness of polyimide 7 (25 µm). Therefore, it is expected that the polyimide core layer of CE12 does not meet the requirement of an elongation at break greater than 60%. Example 14

[0145] For Example 17 (E17), a first polyamic acid solution "A" of monomer compositions ODPA / PMDA (molar ratio 4:1) and RODA was prepared by dissolving the diamine in DMAc under nitrogen with a mechanical stirrer, followed by the addition of dianhydride powder over a short period until a molar stoichiometric ratio of approximately 1:0.97 between the amine and the anhydride monomers was obtained. The polyamic acid solution was then completed by incrementally adding 6% by weight of PMDA solution in DMAc to obtain a maximum viscosity of 2500–3000 poise. A second polyamic acid solution "B" of the monomer compositions PMDA and ODA was prepared by following the procedure described above. The two polyamic acid solutions were co-cast on a stainless steel strip and then dried and imidized by heating in an oven. A polyimide trilayer ABA film with a total thickness of approximately 25 µm was obtained. The thickness of each layer A in the trilayer film was on the order of 2–3 µm. The three-layer polyimide film was then converted into a tape, which was spirally wrapped around a rectangular copper conductor (approximately 0.06” × 0.12”) with 66% overlap and heat-sealed. The resulting insulated wire was then bent along its edges using an R / W of 0.98 and visually inspected for damage. No significant buckling, delamination, or wrinkling was observed in the bent areas of the wire. This result is expected because, based on the analysis of the compositions from Table 1, the combination of the polyimide core layer (based on the 100HN composition) and the outer thermoplastic polyimide layer (based on the polyimide 8 composition) meets the requirements of an elongation at break greater than 60% and a tensile modulus ratio greater than 0.7.

Claims

1. An electrically insulating conductor, comprising: Conductive core; and An insulating wrapping surrounding the conductive core, the insulating wrapping comprising a base film tape, wherein the base film tape comprises: Polymer core layer; and A first thermoplastic polymer outer layer adheres to a first side of the polymer core layer, wherein: The polymer core layer and the first thermoplastic polymer outer layer each have a glass transition temperature of 200°C or higher (T0). g ); The ratio of the bending radius (R) to the width (W) of the insulated conductor is in the range of 0.8:1 to 2:1; and The interlaminar fracture toughness (G) of the first thermoplastic polymer outer layer relative to the conductive core Ic ) is 200 J / m 2 Or larger.

2. The electrically insulating conductor as claimed in claim 1, wherein, The interlaminar fracture toughness (G) of the first thermoplastic polymer outer layer relative to the polymer core layer Ic ) is 140 J / m 2 Or larger.

3. The electrically insulating conductor as described in claim 1, wherein, The average ultimate strain of the base film is 60% or greater.

4. The electrically insulating conductor as claimed in claim 1, wherein, The average ultimate strain of the polymer core layer and the first thermoplastic polymer outer layer is 60% or greater.

5. The electrically insulating conductor as claimed in claim 1, wherein, The ratio of the tensile modulus of the first thermoplastic polymer outer layer to the tensile modulus of the polymer core layer is 0.7:1 or greater.

6. The electrically insulating conductor as claimed in claim 1, wherein, The conductive core comprises wires selected from the group consisting of: copper, copper alloys, silver, silver alloys, aluminum, and stainless steel.

7. The electrically insulating conductor as claimed in claim 1, wherein, The conductive core comprises plated copper wire selected from the group consisting of: nickel-plated copper alloy wire, tin-plated copper alloy wire, and silver-plated copper alloy wire.

8. The electrically insulating conductor as claimed in claim 1, wherein, The polymer core layer further comprises an electrically insulating and corona-resistant composite filler.

9. The electrically insulating conductor as claimed in claim 8, wherein, The electrically insulating, corona-resistant composite filler is present in an amount ranging from 5 to 30% by weight based on the total weight of the polymer core layer.

10. The electrically insulating conductor as claimed in claim 8, wherein, The electrically insulating and corona-resistant composite filler contains organic components and inorganic ceramic oxide components.

11. The electrically insulating conductor as claimed in claim 10, wherein, The organic component is an organosiloxane portion or an organometaloxane portion.

12. The electrically insulating conductor as claimed in claim 10, wherein, The inorganic ceramic oxide component is selected from the group consisting of: silicon dioxide, aluminum oxide, titanium dioxide, zirconium oxide, and mixtures thereof.

13. The electrically insulating conductor as claimed in claim 10, wherein, The weight ratio of the organic component to the inorganic ceramic oxide component is in the range of 0.01:1 to 1:

1.

14. The electrically insulating conductor as claimed in claim 1, wherein, The polymer core layer: It has a heat rating of 200°C or higher; and It includes polyimide, poly(amide-imide), polyaryletherketone, polyphenylene sulfide, polyphenylsulfone, polyethersulfone, polyetherimide, or mixtures thereof.

15. The electrically insulating conductor as claimed in claim 1, wherein, The first thermoplastic polymer outer layer comprises polyimide, poly(amide-imide), polyaryletherketone, polyphenylene sulfide, polyphenylsulfone, polyethersulfone, polyetherimide, or a mixture thereof.

16. The electrically insulating conductor of claim 1, further comprising a second thermoplastic polymer outer layer adhered to a second side of the polymer core layer.

17. The electrically insulating conductor as claimed in claim 16, wherein, The second thermoplastic polymer outer layer comprises polyimide, poly(amide-imide), polyaryletherketone, polyphenylene sulfide, polyphenylsulfone, polyethersulfone, polyetherimide, or a mixture thereof.

18. The electrically insulating conductor of claim 1, further comprising an adhesion promoter layer between the insulating wrapper and the conductive core.

19. The electrically insulating conductor as claimed in claim 18, wherein, The adhesion promoter contains an organosilane portion.

20. The electrically insulating conductor as claimed in claim 19, wherein, The organosilane moiety is an aminosilane.

21. The electrically insulating conductor as claimed in claim 1, wherein, The first thermoplastic polymer outer layer has a thickness in the range of 2 to 10 µm; and The polymer core layer has a thickness ranging from 12 to 75 µm.

22. The electrically insulating conductor as claimed in claim 1, wherein, The cross-sectional profile of the electrically insulating conductor exhibits good concentricity.

23. The electrically insulating conductor as claimed in claim 16, wherein, The interlaminar fracture toughness (G) of the first thermoplastic polymer outer layer relative to the second thermoplastic polymer outer layer Ic ) is 140 J / m 2 Or larger.

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