polymer-coated wire

Abstract

This disclosure provides an insulated electrical conductor, such as a wire, and a method for manufacturing such an insulated electrical conductor, in order to counteract partial discharge by enhancing the bonding strength between the electrical conductor and a main insulating thermoplastic layer (e.g., PAEK). [Solution] The insulated electrical conductor may include an electrical conductor, an insulating coating on at least a portion of the surface of the electrical conductor, and an oxide layer between the electrical conductor and the insulating coating. A method for producing such an insulated electrical conductor may include extruding an insulating polymer onto the electrical conductor in an ambient atmosphere, and a subsequent heat treatment step which may also be carried out in an ambient atmosphere.

Description

Technical Field

[0001] This application relates generally to the field of insulated electrical conductors and to methods associated with such insulated electrical conductors.

Background Art

[0002] An electrical conductor is a material that enables the flow of electric charge (current). A wire is one of the most common forms of an electrical conductor and is typically made of a metal such as aluminum, copper, or an alloy thereof. As electrons flow through such an electrical conductor, heat can be generated due to the activity of the electrons moving between atoms and the associated high-speed motion.

[0003] Devices that include electrical conductors such as wires cannot operate properly without utilizing electrical insulators. In particular, to prevent problems of excessive heat generation / fire, to prevent electric shock, and to ensure the proper functioning and safety of the conductor and the device(s) associated with the conductor, the wire is typically coated with an insulator. The adhesion between the insulating material and the underlying electrical conductor is important, for example, to avoid an air gap that can cause partial electrical discharge during use. Electrical discharge can occur, for example, between the conductor and the adjacent insulating material, within the insulating layer, and / or from outside the insulator, especially when there is an air gap / interlayer delamination between the conductor and the insulating layer (as described above). In the case where the wire is actively shaped (such as in the winding of a motor), good adhesion (which includes little or no air gap between the insulating material and the electrical conductor) is particularly important to mitigate at least the initial discharge mode.

[0004] Polymers are common materials used for wire insulation for many reasons. Certain polymers have high resistance to electric current, are flexible (and therefore can be easily bent around corners and safely directed towards electrical boxes), dissipate heat easily, burn slowly, and are relatively inexpensive. Polyether ketones, such as polyether ether ketone (PEEK), are particularly desirable as insulating materials for conductive wires due to their typically high-temperature working windows and inherent resistance to many chemicals present in industrial and automotive environments. However, direct extrusion molding of thermoplastic polymers such as PEEK onto metals, as used in electrical conductors, is generally problematic because such thermoplastics typically do not bond well to such metals (which, as mentioned earlier, leads to many problems associated with air gaps and delamination). The adhesion of these polymers to conductors is thought to be subject to the presence / formation of oxide layers during processing, and it is generally understood in the art that the presence of oxide layers is detrimental to adhesion. Therefore, attempts have been made to eliminate oxygen from the metal surface during the coating / bonding process in order to provide an insulating layer on electrical conductors. See, for example, European Patent Application Publication No. 3441986 (which, by reference, forms part of this specification in its entirety). Alternative methods have also been used to address adhesion problems, including the application of multiple polymer layers (e.g., baked enamel layers). See, for example, U.S. Patent Application Publication No. 2015 / 0021067 (which, by reference, forms part of this specification in its entirety). In such multilayer arrangements, delamination between adjacent layers can unfortunately lead to the formation of air gaps again within the insulated wire.

[0005] Several attempts have been made to improve the adhesion of insulators to wires by using "pressure coating" technology to improve the close contact between the insulator and the wire beneath it. Pressure coating is distinct from general extrusion molding because, in pressure coating, the wire pin / mandrel is drawn into the inside of the outer molding die by a thermoplastic extrusion tool. This allows the wire to be coated with high-pressure resin before it leaves the machine. In pressure coating, a die the same size as the OD of the product is used, and the wire exits the extruder in a coated form. In contrast, conventional "jacket coating" or "sleeve coating" uses a larger tool set, and a tube is extruded in the same direction as the wire passes through the machine. This tube is drawn down after exiting the extruder and comes into contact with the conductor. In jacket coating or sleeve coating setups, the molding die and pin / mandrel are in the same plane or nearly in the same plane at the exit of the machine, and an air gap exists between the exiting tube and the conductor. This process is carried out so that the tube is drawn down and comes into close contact with the conductor.

[0006] Generally, while pressure coating techniques can improve the "grip" of the insulating layer to the wire, these techniques are understood to do not result in any bonding to the oxide layer on the wire surface beneath. Furthermore, pressure coating may be less desirable than other alternatives such as jacket coating, which allow for the use of larger tube extrusion tool sets, enabling lower pressures, easier control of insulating concentricity / uniformity, and much faster coating line speeds.

[0007] It would be advantageous to provide a further method for fabricating coated electrical conductors that can provide effective adhesion between the polymer coating and the conductor beneath it. [Overview of the Initiative]

[0008] This disclosure provides a method for obtaining a coated (insulating) electrical conductor, in particular a method for achieving effective adhesion between an insulating coating and an electrical conductor. This disclosure further describes the obtained coated electrical conductor, as well as its properties and characteristics.

[0009] The inventors have developed a method for manufacturing coated electrical conductors that, contrary to conventional understanding, is carried out in ambient air without strict attention to the removal of oxygen from the atmosphere. The method disclosed herein makes it possible to obtain coated / insulated electrical conductors that exhibit sufficient adhesion between the insulating coating and the underlying electrical conductor. Coated electrical conductors manufactured by this method are advantageously highly resistant to delamination of the insulating coating from the electrical conductor, as will be more fully described and demonstrated below herein.

[0010] In one aspect, the present disclosure provides an insulated electrical conductor comprising an electrical conductor having an oxide layer on at least a portion of its surface, and an insulating coating on at least a portion of the oxide layer, wherein the insulating coating exhibits adhesion between the insulating coating and one or more of the electrical conductor and the oxide layer such that the insulating coating is not peelable from the electrical conductor. The feature referred to as "not peelable" in the insulating coating may mean that the insulating coating cannot be peeled off from the electrical conductor in a complete or partial tubular form (e.g., under ambient conditions / at room temperature in air).

[0011] The characteristics of electrical conductors can be diverse. In some embodiments, the electrical conductor is a wire. In some embodiments, the electrical conductor has a circular, square, triangular, rectangular, polygonal, or elliptical cross-sectional shape. In some embodiments, the electrical conductor includes copper, aluminum, or a combination thereof. In certain embodiments, the electrical conductor includes copper. In some embodiments, the electrical conductor includes a silver coating, a nickel coating, or a gold coating.

[0012] Similarly, the characteristics of insulating coatings can be diverse. In some embodiments, the insulating coating comprises polyaryl ether ketone (PAEK). Exemplary PAEK polymers include, but are not limited to, polyether ketone (PEK), polyether ether ketone (PEEK), polyether ketone ketone (PEKK), polyether ether ketone ketone (PEEKK), and polyether ketone ether ketone ketone (PEKEKK). In certain embodiments, the insulating coating may further comprise one or more fibers, fillers, or combinations thereof. In some embodiments, the insulating coating comprises a polymer alloy of PAEK and one or more fluororesins. In other embodiments, the insulating coating consists substantially of a polymer, such as PAEK.

[0013] In some embodiments, an electrical conductor is provided, which is a wire having a circular cross-section and having a tanδ attenuation ratio of 1.10 or less when measured according to the following procedure: a) In a DMA device, the coated wire held by the cantilever grip is first heated from room temperature to a temperature T1 corresponding to the peak of the endothermic melting (determined by DSC), b) After 1 minute has elapsed at T1, allow the coated wire to cool back to room temperature. c) Heat the coated wire to T1 for the second time, d) Determine the slope m1 of the tanδ curve at the start of the thermal transition region of the polymer during the first heating cycle. e) Determine the slope m2 of the tanδ curve at the start of the thermal transition region of the polymer during the second heating cycle, and, The tanδ damping ratio is calculated by dividing f)m1 by m2.

[0014] In some embodiments, an insulated electrical conductor is provided, which is a wire having a rectangular cross-section with a tanδ attenuation ratio of less than 1.60 when measured according to the following procedure: a) In a DMA device, the coated wire held by the cantilever grip is first heated from room temperature to a temperature T1 corresponding to the peak of the endothermic melting (determined by DSC), b) After 1 minute at T1, the coated wire is cooled back to room temperature, and then the coated wire is heated to T1 a second time. c) Determine the slope m1 of the tanδ curve at the start of the thermal transition region of the polymer during the first heating cycle. d) Determine the slope m2 of the tanδ curve at the start of the thermal transition region of the polymer during the second heating cycle, and, e) Calculate the tanδ damping ratio by dividing m1 by m2.

[0015] In some embodiments, it is determined that an insulating coating is not peelable from an electrical conductor by making a notch or tear in the insulating coating and attempting to peel the insulating coating from the conductor along the insulating conductor in the longitudinal direction under ambient conditions in air, and observing that the insulating layer does not peel off from the electrical conductor in a complete or partial tubular shape. In some embodiments, electric motors including an insulated electrical conductor disclosed herein are provided.

[0016] Another aspect of the present disclosure provides a method for producing an insulated electrical conductor, comprising: obtaining an electrical conductor comprising a metal oxide on at least a portion of its surface; extruding a polymer insulating coating onto at least a portion of the electrical conductor, wherein the extrusion is performed under ambient conditions; cooling the coated electrical conductor; heat-treating the cooled coated electrical conductor; and cooling the heat-treated coated electrical conductor to obtain an insulated electrical conductor. In some embodiments, a jacket coating tool is used for extrusion. In some embodiments, a pressure coating tool is used for extrusion. Thus, in some embodiments, the method provides a unique approach that includes a pressure coating technique to obtain a coated conductor having a bond between the electrical conductor and the insulating coating, which cannot generally be obtained by pressure coating alone.

[0017] In certain embodiments, the heat treatment includes exposing the cooled coated electrical conductor to a temperature above the glass transition temperature of the polymeric insulating coating. The heat treatment may further include holding the heated coated electrical conductor at that temperature for a specified period. In some embodiments, the extrusion and heat treatment are performed in an ambient atmosphere. The present disclosure further includes an insulated electrical conductor fabricated according to the methods provided by the present disclosure.

[0018] The present disclosure includes, without limitation, the following embodiments.

[0019] Embodiment 1: An insulated electrical conductor comprising an electrical conductor having an oxide layer on at least a portion of its surface and an insulating coating on at least a portion of the oxide layer, the insulating coating exhibiting adhesion between the insulating coating and one or more of the electrical conductor and the oxide layer such that the insulating coating is not peelable from the electrical conductor.

[0020] Embodiment 2: The insulated electrical conductor of the above embodiment, wherein the electrical conductor is a wire.

[0021] Embodiment 3: The insulated electrical conductor of any of the above embodiments, wherein the electrical conductor has a cross-sectional shape that is circular, square, triangular, rectangular, polygonal, or elliptical.

[0022] Embodiment 4: The insulated electrical conductor of any of the above embodiments, wherein the electrical conductor comprises copper, aluminum, or a combination thereof.

[0023] Embodiment 5: The insulated electrical conductor of any of the above embodiments, wherein the electrical conductor comprises copper or a copper alloy.

[0024] Embodiment 6: The insulated electrical conductor of any of the above embodiments, wherein the electrical conductor comprises a silver coating, a nickel coating, or a gold coating.

[0025] Embodiment 7: An insulated electrical conductor according to any of the above embodiments, wherein the insulating film contains polyaryletherketone (PAEK).

[0026] Embodiment 8: An insulated electrical conductor according to any of the above embodiments, wherein the insulating film further contains one or more fibers, fillers, or combinations thereof.

[0027] Embodiment 9: An insulated electrical conductor according to any of the above embodiments, wherein the insulating film consists essentially of polyaryletherketone (PAEK).

[0028] Embodiment 10: An insulated electrical conductor according to any of the above embodiments, wherein the insulating film contains a polymer selected from the group consisting of polyetherketone (PEK), polyetheretherketone (PEEK), polyetherketoneketone (PEKK), polyetheretherketoneketone (PEEKK), and polyetherketoneetherketoneketone (PEKEKK).

[0029] Embodiment 11: An insulated electrical conductor according to any of the above embodiments, wherein the insulating film contains a polymer alloy of PAEK and one or more fluororesins.

[0030] Embodiment 12: An insulated electrical conductor according to any of the above embodiments, wherein the electrical conductor is a wire having a circular cross-section with a tanδ attenuation ratio of 1.10 or less when measured according to the following procedure: a) In a DMA device, the coated wire held by a cantilever grip is heated for the first time from room temperature to a temperature T1 corresponding to the peak of the melting endotherm (determined by DSC), b) After 1 minute at T1, the coated wire is cooled back to room temperature, c) The coated wire is heated to T1 for the second time, d) Determine the slope m1 of the tanδ curve at the start of the thermal transition region of the polymer during the first heating cycle, e) Determine the slope m2 of the tanδ curve at the start of the thermal transition region of the polymer during the second heating cycle, and The tanδ damping ratio is calculated by dividing f)m1 by m2.

[0031] Embodiment 13: An insulated electrical conductor according to any of the above embodiments, wherein the electrical conductor is a wire having a rectangular cross-section with a tanδ attenuation ratio of less than 1.60 when measured according to the following procedure: a) In a DMA device, the coated wire held by the cantilever grip is first heated from room temperature to a temperature T1 corresponding to the peak of the endothermic melting (determined by DSC), b) After 1 minute at T1, the coated wire is cooled back to room temperature, and then the coated wire is heated to T1 a second time. c) Determine the slope m1 of the tanδ curve at the start of the thermal transition region of the polymer during the first heating cycle. d) Determine the slope m2 of the tanδ curve at the start of the thermal transition region of the polymer during the second heating cycle, and, e) Calculate the tanδ damping ratio by dividing m1 by m2.

[0032] Embodiment 14: An insulated electrical conductor according to any of the above embodiments, wherein it is determined that the insulating coating is not peelable from the electrical conductor by making a notch or tear in the insulating coating, attempting to peel the insulating coating from the notch or tear along the longitudinal direction in air under ambient conditions along the insulated electrical conductor, and observing that the insulating layer does not peel off from the electrical conductor in a complete or partial tubular shape.

[0033] Embodiment 15: An electric motor comprising an insulated electrical conductor according to any of the above embodiments.

[0034] Embodiment 16: A method for producing an insulated electrical conductor, comprising: obtaining an electrical conductor having an oxide layer on at least a portion of its surface; extruding a polymer insulating film onto one or more of the electrical conductor and the oxide layer such that the insulating film is not peelable from the electrical conductor, wherein the extrusion is performed under ambient atmospheric conditions; cooling the coated electrical conductor; heat-treating the cooled coated electrical conductor; and cooling the heat-treated coated electrical conductor to obtain an insulated electrical conductor.

[0035] Embodiment 17: The method of the above embodiment, wherein extrusion molding is performed using a pressure coating tool.

[0036] Embodiment 18: Extrusion molding is performed using any of the above embodiments, wherein a jacketed tool is used.

[0037] Embodiment 19: A method according to any of the above embodiments, wherein the heat treatment involves exposing a cooled coated electrical conductor to a temperature above the glass transition temperature of the polymer insulating film.

[0038] Embodiment 20: A method according to any of the above embodiments, further comprising holding a heated coated electrical conductor at the above temperature for a specific period of time.

[0039] Embodiment 21: Extrusion molding and heat treatment are carried out in an ambient atmosphere, according to any of the above embodiments.

[0040] Embodiment 22: Any method according to the above embodiments, wherein the electrical conductor is a wire.

[0041] Embodiment 23: A method according to any of the above embodiments, wherein the electrical conductor has a circular, square, triangular, rectangular, polygonal, or elliptical cross-sectional shape.

[0042] Embodiment 24: A method according to any of the above embodiments, wherein the electrical conductor includes copper, aluminum, or a combination thereof.

[0043] Embodiment 25: A method according to any of the above embodiments, wherein the electrical conductor includes a silver film, a nickel film, or a gold film.

[0044] Embodiment 26: A method according to any of the above embodiments, wherein the insulating coating comprises polyaryletherketone (PAEK).

[0045] Embodiment 27: A method according to any of the above embodiments, wherein the insulating coating further comprises one or more fibers, fillers, or combinations thereof.

[0046] Embodiment 28: A method according to any of the above embodiments, wherein the insulating coating consists substantially of polyaryletherketone (PAEK).

[0047] Embodiment 29: A method according to any of the above embodiments, wherein the insulating coating comprises a polymer selected from the group consisting of polyetherketone (PEK), polyetheretherketone (PEEK), polyetherketoneketone (PEKK), polyetheretherketoneketone (PEEKK), and polyetherketoneetherketoneketone (PEKEKK).

[0048] Embodiment 30: A method according to any of the above embodiments, wherein the insulating coating comprises a polymer alloy of PAEK and one or more fluororesins.

[0049] Embodiment 31: An insulated electrical conductor manufactured according to any of the methods of the above embodiments.

[0050] These and other features, aspects and advantages of this disclosure may become apparent by reading the following detailed description in conjunction with the accompanying drawings, which are briefly described below. The present invention includes any combination of two, three, four or more of the embodiments described above, and any combination of two, three, four or more features or elements described herein, regardless of whether such features or elements are identified and combined in the description of specific embodiments herein. This disclosure is intended to be read holistically, and so it is assumed that in any of its various aspects and embodiments, any separable features or elements of the disclosed invention are intended to be combined, unless otherwise explicitly stated in the context. Other aspects and advantages of the present invention will become apparent below.

[0051] To understand embodiments of the present invention, the accompanying drawings are referred to. These drawings are not necessarily drawn to the correct scale, and in the drawings, reference numerals represent components of exemplary embodiments of the present invention. The drawings are illustrative only and should not be construed as limiting the present invention. [Brief explanation of the drawing]

[0052] [Figure 1] This is a comprehensive schematic diagram of the method disclosed herein. [Figure 2] This is a graph of the tanδ dynamic temperature scanning of a bare copper wire. [Figure 3] This graph shows the calculation of the slope during the first scan (solid line) and the second scan (dotted line) for the heat-treated sample of Example 1, representing the tanδ scan. [Figure 4] This graph shows the calculation of the slope during the first scan (solid line) and the second scan (dotted line) for the untreated sample of Example 1, representing the tanδ scan. [Modes for carrying out the invention]

[0053] The present invention will now be described in more detail. However, the present invention can be embodied in many different forms and should not be construed as being limited to the embodiments shown herein. Rather, these embodiments are presented to make this disclosure thorough and complete and to fully convey the scope of the invention to those skilled in the art. Where used herein and in the claims, the singular nouns ("a", "an", and "the") refer to multiple subjects unless the context explicitly states otherwise.

[0054] This disclosure provides coated electrical conductors and methods for manufacturing such coated electrical conductors. Since the coating is typically an insulating material, as will be described more thoroughly below in this specification, coated electrical conductors are insulated electrical conductors. Surprisingly, the coated electrical conductors described herein can be manufactured in an ambient atmosphere (e.g., without strictly excluding oxygen) such that the coated electrical conductor includes at least a partial oxide layer between the insulating coating and the electrical conductor. Nevertheless, as will be demonstrated herein, the insulating coating and electrical conductor exhibit sufficient adhesion, and in some embodiments, excellent adhesion, contrary to the conventional understanding regarding the importance of excluding such oxide layers.

[0055] In a first aspect, the disclosure provides a method for manufacturing a coated electrical conductor, as comprehensively outlined in Figure 1. As illustrated, the method comprises four steps: an extrusion step to obtain a coated electrical conductor; a cooling step to obtain the obtained coated electrical conductor; a heat treatment step; and a second cooling step to obtain a desired product. The extrusion step generally involves melting a thermoplastic polymer and applying it to the surface of the electrical conductor. In the extrusion step of the disclosed method, either a pressure coating technique or a jacket coating technique may be used. Typically, the extrusion is carried out using equipment specific to this purpose, which includes means of orienting the electrical conductor into a diodeifer, drawing the electrical conductor through the diodeifer, and bringing the electrical conductor into contact with the molten polymer under conditions that produce a predetermined insulating film thickness, thereby drawing out a wire. Methods for extruding a thermoplastic polymer onto an electrical conductor are known. An exemplary method is disclosed, for example, at https: / / www.victrex.com / ~ / media / literature / en / victrex_extrusion-brochure.pdf (which, by reference, is in whole part of this specification). Those skilled in the art will understand, for example, that processing conditions can be modified to achieve a consistent insulating coating and to obtain various coating thicknesses, etc.

[0056] Advantageously, the extrusions according to this disclosure do not need to be carried out in the absence of oxygen. In fact, in certain embodiments, the extrusion process is carried out in an ambient atmosphere (such as in air where oxygen has not been intentionally removed from the atmosphere (untreated)). Thus, it may be stated that the extrusion is carried out in the presence of oxygen in some embodiments. No pretreatment steps are required to ensure that the electrical conductor is substantially oxide-free before an insulating coating is extruded thereon (e.g., plasma treatment in an oxygen-free protective gas atmosphere, as outlined in European Patent Application Publication No. 3441986, which is by reference to form the whole of this specification).

[0057] The materials used in extrusion molding can be diverse. Electrical conductors generally include any material suitable for electrical conductivity. In certain embodiments, electrical conductors include metals that can be oxidized, and in certain such embodiments, electrical conductors include such metals on at least a portion of their surface. Typically, electrical conductors include metals such as copper, aluminum, or combinations or alloys thereof. In some embodiments, electrical conductors may include coatings such as metal coatings. Metal coatings may include, for example, silver, nickel, or gold (metal-coated / metal-plated conductors are provided). While this disclosure refers to the application of thermoplastic polymers on electrical conductors, it should be noted that the principles and methods outlined herein may be used for the application of thermoplastic polymers on other materials (e.g., on materials containing metals that are not electrical conductors).

[0058] The size and shape of the electrical conductor can vary. In certain embodiments, the electrical conductor is a wire. For example, the electrical conductor may be a copper-containing wire (e.g., a copper wire), an aluminum-containing wire (e.g., an aluminum wire), or a plated copper-containing wire or aluminum-containing wire. The electrical conductor may have any cross-sectional shape, such as circular, square, triangular, rectangular, polygonal, or elliptical, as long as the size and shape are compatible with the extrusion apparatus used in the above method.

[0059] Polymer materials applied to electrical conductors include thermoplastic polymers known in the art, which can be softened and melted by, for example, the application of heat, and which can be processed in a liquid state (for example, by extrusion). In certain embodiments, the polymer material includes polyaryl ether ketone (PAEK). PAEK is a semi-crystalline thermoplastic polyketone. The polymer material typically contains a majority of PAEK, i.e., at least about 70% by weight of PAEK (the remainder being fillers, fibers, or other polymers, for example, which are described in more detail below). In further embodiments, the polymer material contains at least about 80% by weight, at least about 90% by weight, at least about 95% by weight, at least about 98% by weight, or at least about 99% by weight of PAEK. In some embodiments, the polymer material may consist substantially of PAEK. Exemplary PAEK polymers include, but are not limited to, polymers selected from the group consisting of polyetherketone (PEK), polyetheretherketone (PEEK), polyetherketoneketone (PEKK), polyetheretherketoneketone (PEEKK), and polyetherketoneetherketoneketone (PEKEKK).

[0060] As previously stated, in some embodiments, the polymer material includes one or more additional components in addition to PAEK. Generally, the polymer material may include, in addition to PAEK, any additives suitable for improving the properties when PAEK functions as a primary insulator. In some embodiments, the polymer material includes PAEK and one or more fibers, fillers, or combinations thereof. The fibers and / or fillers optionally included in the thermoplastic polymers disclosed herein may be, for example, any material known to be useful for improving one or more polymer properties. A variety of relevant fillers are known and may be used in the resins and / or corresponding insulating coatings disclosed herein. Certain exemplary fillers and other additives include, but are not limited to, glass spheres, glass fibers, all forms of carbon (e.g., color, nanotubes, powders, fibers), radiopaque agents such as barium sulfate (BaSO4), bismuth carbonate, bismuth oxychloride, and tungsten, cooling fillers such as boron nitride (BN) matrices, colorants / pigments, processing aids, and combinations thereof.

[0061] In other embodiments, the polymer material may include one or more additional polymers (e.g., a polymer alloy with PAEK is obtained). For example, in some embodiments, the polymer material may include one or more fluoropolymers. Various fluoropolymers are known to be readily miscible in PAEK up to fairly high percentages (e.g., up to 30%), and such combinations / alloys may be used in the manner shown herein. In some embodiments, the inclusion of one or more fluoropolymers with PAEK provides physical benefits, for fluoropolymers generally have exceptional electrical properties with respect to absolute dielectric constant and dielectric properties (but are often poor wear resistance and not bondable), and can impart certain properties to the material, such as friction reduction (which can make it easier to mount the resulting product, for example, in tightly packed motor slots). In some embodiments, the content of additional polymers (which may be more than one) is kept at a somewhat lower level, for example, so that about 70% or more of the polymer material contains PAEK, or so that about 80% or more, about 85% or more, about 90% or more, about 95% or more, about 98% or more, or about 99% or more of the polymer material contains PAEK.

[0062] After the extrusion process, the resulting coated conductor is cooled to at least slightly below, for example, the glass transition temperature (Tg) of the material. Following this cooling, the coated conductor is subjected to a heat treatment. This heat treatment typically involves treating the coated conductor under increasing temperature, for example, above the Tg of the insulating coating on the coated conductor. In some embodiments, this temperature may be above the melting point (Tm) of the polymer resin. In various embodiments, any temperature sufficient to at least partially remelt the resin is sufficient for this heat treatment. The parameters of the heat treatment are not particularly limited, and the heat treatment may be carried out in an ambient atmosphere, such as in an oxygen-containing atmosphere, for example, in (untreated) air. Suitable heating methods are widely known and may be used in the manner disclosed herein. For example, in various embodiments, the heat treatment is carried out by exposing the coated conductor to heat generated in a furnace. In various embodiments, the heat treatment can be one or more of radiant heating, infrared heating, induction heating, microwave heating, heating via conduction with a fluid, convection heating, and any combination thereof. In some embodiments, the heat treatment includes, but is not limited to, a single heating. In some embodiments, the coated electrical conductor is heated two or more times (with cooling in between). In certain embodiments, such multiple heatings may be desirable to ensure that the coating melts and flows to achieve sufficient adhesion.

[0063] In the heat treatment process, the coated electrical conductor is heated (once or more times as described above) and then held under the aforementioned temperature increase for a given period of time. This period can vary, for example, ranging from a few seconds or minutes to several hours. As an example, heating may be carried out in some embodiments by placing the coated electrical conductor in an oven and holding it in the oven for about one minute or more, for example, from about one minute to about two hours or from about five minutes to about thirty minutes.

[0064] The heat-treated coated electrical conductor is cooled to ambient temperature, for example, after the heat treatment. The resulting coated electrical conductor surprisingly exhibits not only sufficient but even excellent adhesion between the conductor and the insulating coating on top. In particular, such coated electrical conductors have been found to be highly resistant to delamination of the insulating coating layer from the underlying electrical conductor. Thus, surprisingly, the method outlined herein has been found to produce the unique properties associated with the resulting coated electrical conductor. While not intended to be limited by theory, it is believed that the multi-step method outlined herein (including extrusion, cooling, and reheating of the coated conductor) yields a coated product with good bonding between the metal oxide layer on the surface of the conductor and the PAEK present in the adjacent polymer insulating material. Test data, referred to in the form of plaque testing in the following examples herein, actually show that the bond formed between the metal oxide and PAEK is, unexpectedly, stronger than the bond between the metal oxide and the metal of the conductor. It should be noted that in some embodiments, it may be beneficial to measure the change in the dynamic-mechanical response of the coated electrical conductor (described in further detail below herein) to identify the conditions used in the disclosed method that provide sufficient adhesion between the conductor and the insulating layer.

[0065] The coated electrical conductors described herein are distinguished from certain known coated electrical conductors because they include an electrical conductor and an insulating coating thereon, and have metal oxides between the conductor and the insulating coating. It is understood that the specific metal oxides present (there may be more) depend on the composition of the electrical conductor (for example, copper electrical conductors contain copper oxide). The amount of oxide present between the conductor and the insulating coating can vary depending on the processing conditions, e.g., the specific environment in which the steps of the above method are carried out, the time the material is held under increasing temperature during the heat treatment process, and the extrusion and / or heat treatment temperatures. As stated above, although not quantified, the disclosed coated conductors are thought to have a strong bond between the metal oxides present on the surface of the conductor and the PAEK of the insulating polymer. Again, although not intended to be limited by theory, it is thought that the presence of these bonds between the PAEK of the insulating polymer and the metal oxides results in the strength / integrity of the coated product (making it significantly less susceptible to the types of peeling / detachability described later herein compared to conventional products).

[0066] The coated electrical conductors of this disclosure are typically distinguished from certain known coated electrical conductors not only by the type of oxide and the bonds formed thereby, but also by their physical properties, namely the bond strength between the electrical conductor and the insulating coating. The bond strength can be evaluated in various ways.

[0067] In some embodiments, the disclosed coated conductors are described with respect to the manual peelability (also referred to herein as “peelability”) of the insulating coating from the underlying conductor. A peelable insulating coating can be easily pulled away from the conductor in a tubular shape. If peelability is reduced, this becomes impossible, and instead the insulating coating is pulled apart. For example, a manual peel test may be performed in which a notch / tear is made in the insulating coating and the insulating coating is pulled / peeled along the length of the coated conductor in an attempt to separate the insulating coating from the conductor. Products exhibiting insufficient adhesion will easily peel off along the length of the coated conductor, for example, in one long, complete piece of insulating coating. Products within the scope of this disclosure do not exhibit such peelability. Rather, the disclosed coated conductors have sufficient adhesion so that they never peel off to a large extent (for example, so that the insulating layer cannot peel off from the underlying conductor in a complete or partial tubular shape). See the examples for a non-limited demonstration of peelability by manual manipulation.

[0068] In certain embodiments, the coated electrical conductors of the present invention exhibit only small sections of the insulating coating missing when notching / tearing and / or delamination is attempted. Various products described herein exhibit such properties, i.e., the insulating coating is not easily delaminated from the electrical conductor beneath it. In some embodiments, the disclosed coated electrical conductors are described as not exhibiting significant delamination after aggressive shaping (in particular, not involving delamination between the insulating coating and the electrical conductor). Generally, aggressive shaping, in the art, is understood in the case of a round wire as winding a shaping material around the diameter of the wire itself and examining the inner diameter (ID) of the shaping material for wrinkle formation or delamination. In the case of aggressive shaping of a rectangular cross-section, winding can be replaced with a portion bent by a corkscrew bend along the long axis, short axis, or any inner radius, or all twists can be addressed without obvious delamination, cracking, or adverse effects. Delamination is a failure mode in which the material separates into layers (in this specification, the insulating coating separates from the electrical conductor). Delamination can be easily observed visually, that is, by examining the interface between the conductor and the insulating coating. In various embodiments, it is advantageous that no visual delamination is observed with the naked eye (i.e., without magnification) both before and after subjecting the disclosed coated conductor to the aforementioned aggressive shaping method. Various test methods are known and can similarly be used to evaluate the absence of delamination.

[0069] In some embodiments, the disclosed coated electrical conductors are described in relation to their bonding strength, as indicated by their damped dynamic-mechanical response. It has been found that the dynamic-mechanical response of polymer-coated wires dampens with increasing treatment, and this damping serves as an indicator of the polymer's adhesion to the wire. Damping can be determined, for example, from a dynamic temperature scan of tanδ using a dynamic mechanical analyzer (DMA). See, for example, KP Menard, Dynamic Mechanical Analysis: A Practical Introduction, CRC Press, 1999 (which is incorporated herein by reference). Since tanδ is defined as the ratio of the loss modulus (E'') to the storage modulus (E'), this serves as an indicator of damping due to viscous energy dissipation. This analysis is very similar to the heat treatment step of the disclosed method (using a coated wire and examining the dynamic response at the first heat versus the second heat, where the second heat represents subsequent heat treatment of the product).

[0070] For example, when a bare copper wire is subjected to dynamic temperature scanning, the plot of tanδ against temperature is not noteworthy, and no clear transition peak is observed. See Figure 2. When an insulated copper wire is subjected to the same DMA method, the plot of tanδ against temperature shows a clear transition within a range typical of the insulating polymer, as seen in Figures 3 and 4. For example, in the case of PEEK, the transition begins at temperatures above 150°C.

[0071] Currently, it has been observed that strongly adhesive insulating coatings exhibit a more attenuated response in the tanδ transition region compared to less adhesive polymer layers. This effect can be quantified by calculating the slope of the curve at the start of the thermal transition during the first dynamic temperature scan. The insulated wire is then maintained at its peak melting temperature (determined by differential scanning calorimetry (DSC)) for one minute and then cooled to room temperature. A second slope is then calculated during the subsequent dynamic temperature scan. The degree of attenuation can be quantified by dividing the slope obtained during the first scan by the slope obtained during the second scan.

[0072] The inventors have found that the degree of tanδ decay serves as an indicator of adhesion between the polymer and the conductor. In certain embodiments, in the case of insufficient adhesion, the decay ratio is greater than 1.10, for example, for a wire with a circular cross-section. In other words, heating of the insulator and wire during dynamic temperature scanning results in a significant change in the slope of tanδ between heating cycles if adhesion is insufficient. One such exemplary embodiment is shown in Figure 3. However, in such embodiments, if adhesion is good, the effect of the heating cycle on tanδ is reduced, and the ratio is less than or equal to 1.10. One such exemplary embodiment is shown in Figure 4.

[0073] The slope of this DMA is an indicator of the tightness of the contact between the conductor and the insulating coating. An unbonded wire will have a minute slip at the conductor / insulating coating interface. When the first DMA cycle is performed on an untreated wire, this effectively replicates the heat treatment step of the disclosed method (described in detail above). The wire will respond differently in the second DMA cycle because, if the bonding is improved, it will adhere to the underlying copper oxide layer. In a bonded sample (obtained according to the disclosed method), the difference in slope is much smaller because the minute slip from the first cycle has already been eliminated by bonding to the underlying copper oxide layer.

[0074] In one particular embodiment, a wire-type insulated electrical conductor has a circular cross-section with a tanδ attenuation ratio of 1.10 or less, as measured according to the following procedure: a) In a DMA device, the coated wire held by the cantilever grip is first heated from room temperature to a temperature T1 corresponding to the peak of the endothermic melting (determined by DSC), b) After 1 minute has elapsed at T1, allow the coated wire to cool back to room temperature. c) Heat the coated wire to T1 for the second time, d) Determine the slope m1 of the tanδ curve at the start of the thermal transition region of the polymer during the first heating cycle. e) Determine the slope m2 of the tanδ curve at the start of the thermal transition region of the polymer during the second heating cycle, and, The tanδ damping ratio is calculated by dividing f)m1 by m2.

[0075] In another specific embodiment, a coated electrical conductor in the form of a wire has a rectangular cross-section with a tanδ attenuation ratio of less than 1.60 when measured according to the following procedure: a) In a DMA device, the coated wire held by the cantilever grip is first heated from room temperature to a temperature T1 corresponding to the peak of the endothermic melting (determined by DSC), b) After 1 minute at T1, the coated wire is cooled back to room temperature, and then the coated wire is heated to T1 a second time. c) Determine the slope m1 of the tanδ curve at the start of the thermal transition region of the polymer during the first heating cycle. d) Determine the slope m2 of the tanδ curve at the start of the thermal transition region of the polymer during the second heating cycle, and, e) Calculate the tanδ damping ratio by dividing m1 by m2.

[0076] In further embodiments, a method is provided for obtaining a coated electrical conductor having a sufficient level of adhesion between the electrical conductor and the insulating coating. "Sufficiency" can be varied and may be defined, for example, according to any of the methods outlined herein. This method typically involves manipulating the parameters of the methods described herein to obtain a specific damping of the dynamic mechanical response of the product (for example, obtaining a tanδ damping ratio of 1.10 or less for wires having a round cross-section, or a tanδ damping ratio of less than 1.60 for wires having a rectangular cross-section).

[0077] It should be noted that DMA testing can be affected, for example, by the presence of a significant amount of fillers / additives / other polymers in the polymer insulating coating. Therefore, in some embodiments, the test methods and results presented herein with respect to DMA may be particularly relevant to PAEK-based polymer insulating coatings having low levels of other components (e.g., less than about 10%, less than about 5%, or less than about 2%). A common problem is that the DMA method is unsuitable for evaluation when the DSC trace of the insulating coating is considered complex.

[0078] The properties of certain coated electrical conductors described herein may be further described below based on the partial discharge exhibited in response to longitudinal stretching. A given strain (e.g., 20% strain) is applied to a heat-treated coated wire and a comparative (unheat-treated) coated wire. Such tests are favorably designed to isolate corona discharge on the wire surface, so that only defects in the conductor or within the insulating layer itself are revealed. The wire is wound in two loops around a mandrel five times the wire diameter, simulating the shaping radius for motor winding applications or the bending radius required to attach the wire to a system. This test is designed to determine whether, when stressed and shaped, the product exhibits a significant air gap between the conductor and the insulating layer (which indicates a lack of sufficient bonding between the conductor and the layer). A significant air gap is demonstrated by reaching a high partial discharge (e.g., PD greater than 20 pC) at a low voltage value (e.g., less than 6000 VAC), as described more thoroughly below.

[0079] To isolate corona (surface discharge), which is typical in PDIV testing of twisted pairs where discharge can occur in an external air gap, a wire loop wound on a mandrel is submerged in a saturated salt bath. The salt bath has a ground electrode for testing submerged below the water surface. Since this salt bath effectively carries all charge directly from the wire surface to the submerged ground, no corona effect can be observed in the PD measurement circuit. To prevent discharge when the wire is placed in the water bath, insulating oil or insulating fluid (e.g., silicone oil) can be placed on the water surface. Corona discharge on the wire surface is readily identifiable to those skilled in the art of this electrical test, and can be seen or heard as a characteristic buzzing sound, and the results from this surface corona should be canceled out. In the embodiments shown, the specific insulating fluid was silicone oil. Such treatment / testing (including the strain and mandrel shaping mentioned) simulates aggressive handling and motor winding, which are typical conditions to which coated electrical conductors are exposed. Thus, such results may be particularly relevant in some embodiments to evaluate the ability of a given product to exhibit good coupling under its usage conditions. In certain embodiments, values ​​of 6000 VAC or higher are demonstrated by the disclosed coated conductor without a sustained 20 pC discharge in this test. It should be noted that this test is not always reliable for all embodiments. For example, very thin coated conductors may fail before 6000 VAC. However, for certain coated conductors, such an assessment of bonding strength is a useful method to confirm that the product exhibits sufficient properties to be useful without significant delamination in the relevant conditions.

[0080] The 20% strain and subsequent aggressive shaping in this test method are designed to create an air gap. Products subjected to the method described herein do not exhibit partial discharge or dielectric breakdown in the bath (in the case of very thin coatings), similar to the previously disclosed values ​​(up to 6000VAC). In properly bonded wires (obtained according to the disclosed method), no sustained discharge exceeding 20 pc occurs after 20% strain and aggressive shaping. In unbonded wires, 20% strain and aggressive shaping may be possible without the presence of an air gap, which does not exhibit a sustained discharge of 20 pC, but is evident in the DMA test response during gradient analysis of heat treatment. Therefore, the combination of partial discharge analysis and DMA analysis previously disclosed herein may be particularly suitable for analyzing coated wires in some embodiments.

[0081] It should be understood that the coated electrical conductors and related methods disclosed herein are not limited to electrical conductors having a single insulating (e.g., PAEK) coating thereon. Rather, this disclosure is intended to further encompass coated products with one or more additional layers. As described and illustrated herein, the inventors have independently developed the ability to form a strong bond between an electrical conductor and a thermoplastic polymer coating. Once this initial coating is obtained (as shown herein), further layers are not particularly limited. Thus, coated electrical conductors having one, two, three, four, five, or more additional layers are also within the scope of this disclosure, and these additional layers may be the same or different from each other and may include any polymer bonded to the insulating coating polymer, for example, by co-extrusion or sequential layer formation. Any such additional layers may be entirely polymer or may contain any of the types of fillers and / or additives described herein. The insulated conductors disclosed herein can be used in a variety of applications. For example, in some embodiments, this disclosure provides an electric motor comprising one or more insulated electrical conductors disclosed herein. [Examples]

[0082] Example 1: PEEK (Vestakeep 5000G) on AWG15 Cu wire Two samples were prepared, one with a heat treatment process and the other without. The wire was AWG15 Cu wire, and a nominal 0.006-inch PEEK insulating layer was applied using a 3 / 4-inch 24:1 thermoplastic extruder with a tube coating crosshead at a speed of 9 FPM. Before coating, the wire was preheated to approximately 400°F in an oxygen-containing environment (ambient air) using an external heat source. A 0.285-inch die and a 0.210-inch mandrel (designed for sleeve coating techniques, which are generally considered unfavorable for bond formation) were used to set the drawdown of the PEEK thermoplastic on the AWG15 wire. After extrusion, each coated product was allowed to cool completely; one product was left unprocessed, while the other was subsequently heated (melted) at a temperature higher than the glass transition temperature of PEEK and then cooled in ambient air. The method for characterizing these samples is described below. All characteristic evaluation data is shown in Table 1 below Example 5.

[0083] Peelability by manual operation The adhesion strength between the insulating coating and the conductor was evaluated using a method of propagation by manual peeling. Near one end, a 1.5-inch length was removed from around the insulated wire. Then, using a razor blade, an incision was made in the insulating coating for a length of 0.5 inches, starting from this end. The effort required to separate the insulating coating from the wire was then evaluated on a scale of 1 to 3. A value of 1 was assigned if the insulating material peeled off with little to no effort after the incision. A value of 2 was assigned if the insulating layer required effort to begin peeling but peeled off easily once it started. A value of 3 was assigned if the insulating material did not peel off or peeled off in a section of less than 0.125 inches. Tests of propagation by manual peeling yielded a value of "1" for unheat-treated samples and a value of "3" for heat-treated samples.

[0084] Damping ratio The thermal behavior of the sample was characterized using ASTM D3418-15: Standard Test Method for Transition Temperatures and Enthalpies of Fusion and Crystallization of Polymers by Differential Scanning Calorimetry (2015) with a TA Instruments DSC Q2000. The insulating material was removed from the conductor, equilibrated at 30°C in an aluminum pan, and then heated to 400°C at a constant rate of 10°C / min. The sample was then cooled back down to 30°C at a constant rate of 10°C / min. The sample was heated again to 400°C at a rate of 10°C / min. The DSC data was analyzed using TA Instruments Universal Analysis 2000 v4.5A software. The peak of endothermic fusion was determined to be at 339°C.

[0085] The DMA test was performed according to ASTM D4065-12: Standard Practice for Plastics: Dynamic Mechanical Properties: Determination and Report of Procedures (2012) (which is incorporated herein by reference) to determine the tanδ curve in dynamic temperature scanning. Using a TA Instruments Q800 DMA with a cantilever fixture, tanδ was determined by dynamic temperature scanning from room temperature to 339°C and holding at 339°C for 1 minute. The sample was heated at a constant rate of 3°C / min while being displaced with a constant amplitude of 30 μm by a flexural vibration at a fixed frequency of 1 Hz. After the first temperature scan was completed, the sample was cooled to room temperature. Then, a second dynamic temperature scan was performed using the same parameters as the first heating lamp. After both heating cycles were completed, the DMA data was imported into OriginLab's OriginPro 2019b v.9.65 data analysis and graphing software. The slope was calculated after the inflection point corresponding to the thermal transition of the insulating layer. Then, the ratio of the slopes obtained for each dynamic temperature scan was taken by dividing the first slope by the second slope. This ratio is 1.65 when the sample is not heat-treated. This ratio is 0.76 when the sample is heat-treated.

[0086] Example 2: PEEK on AWG15 Cu wire (Solvay KT-820NT) Two samples were prepared: one with a heat treatment process and the other without. These samples were prepared in the same manner as the samples in Example 1, except that different PEEK resins were used and the extrusion rate was 8 feet per minute. The characterization data is shown in Table 1 below Example 5.

[0087] Example 3: PEEK (Victrex 381G) on AWG18 Cu wire Two samples were prepared, one with a heat treatment process and the other without (prepared in the same manner as in Example 1 above). The wire was AWG18 Cu wire, and a nominal 0.00145 inch PEEK insulation layer was applied using a 3 / 4 inch 24:1 thermoplastic extruder with a pipe coating crosshead at a speed of 15.5 FPM. Before coating, the wire was preheated to approximately 400°F using an external heat source. A 0.253 inch die and a 0.200 mandrel were used to set the drawdown of the PEEK thermoplastic on the AWG18 wire. After extrusion, each coated product was allowed to cool completely; one product was left unprocessed, while the other was subsequently heated (melted) at a temperature higher than the glass transition temperature of PEEK for 1 hour and then cooled in ambient air. Characterization data are shown in Table 1 below Example 5.

[0088] Comparative Example 1: AWG20 Cu wire from Dacon's D-20APK2 This is a comparable commercially available product (PEEK on Cu wire) with a nominal wall thickness of 0.003. The PEEK coating easily detached from the material using a wire stripper and could not withstand shaping.

[0089] Example 4: PEEK (Victrex 150G) on AWG20.5 Cu wire Samples were prepared with a heat treatment process (similar to the corresponding method in Example 1 above). The wire was an AWG 20.5 Cu wire, and a nominal 0.0039 inch PEEK insulating layer was applied. Before coating, the wire was preheated to approximately 400°F using an external heat source. After extrusion, the coated product was allowed to cool completely. This was then heated (melted) at a temperature higher than the glass transition temperature of PEEK for 1 hour, and then cooled in ambient air. Characterization data are shown in Table 1 below Example 5.

[0090] Example 5: PEEK on a Cu rectangular wire (Solvay KT-820NT) Two samples were prepared, one with a heat treatment process and the other without (prepared in the same manner as in Example 1 above). The wire was a Cu rectangular wire, and a nominal 0.0075 inch PEEK insulation layer was applied using a 1-inch 24:1 thermoplastic extruder with a pipe coating crosshead at a speed of 3.6 FPM. Before coating, the wire was preheated to approximately 400°F using an external heat source. A 0.400-inch die and a 0.361-inch mandrel were used to set the drawdown of the PEEK thermoplastic on the rectangular wire. After extrusion, each coated product was allowed to cool completely; one product was left unprocessed, while the other was subsequently heated (melted) at a temperature higher than the glass transition temperature of PEEK for 1 hour and then cooled in ambient air. Characterization data are shown in Table 1 below this example.

[0091] Various resins and wires tested in different embodiments showed little to no variability (size and / or shape) associated with the specific resin or wire selected. As a result, the disclosed method is not specific to resin grades, and it was found that not only PAEK resins but also filler resins and alloy resins function well using the disclosed method (based on, for example, a reduction in tanδ with respect to heat treatment values, improved bonding, and possible shaping without significant delamination).

[0092] [Table 1]

[0093] Many variations and other embodiments of the present invention will be conceivable to those skilled in the art in which the invention relates, who will benefit from the teachings presented in the above description. Therefore, it should be understood that the present invention is not limited to the specific embodiments disclosed, and that variations and other embodiments are intended to be included within the scope of the appended claims. Certain terms are used herein, but these terms are used only in a general and descriptive sense, and not for restrictive purposes.

Claims

1. An electrical conductor having an oxide layer on at least a portion of its surface, An insulating coating extruded onto at least a portion of the oxide layer to form an insulated electrical conductor, An insulated electrical conductor containing, The aforementioned electrical conductor includes copper or a copper alloy. The insulated electrical conductor is cooled, and after the insulating coating is applied to at least a portion of the oxide layer, it is subjected to a heat treatment, the heat treatment comprising heating the insulated electrical conductor to a temperature equal to or greater than the melting point Tm of the insulating coating. An insulated electrical conductor, wherein the insulating coating is not detachable from the electrical conductor after the heat treatment, and therefore cannot be peeled off from the electrical conductor in a complete or partial tubular shape, exhibiting adhesion between the insulating coating and one or more of the electrical conductor and the oxide layer.

2. The insulated electrical conductor according to claim 1, wherein the electrical conductor is a wire.

3. The insulated electrical conductor according to claim 1, wherein the electrical conductor has a circular, square, triangular, rectangular, polygonal, or elliptical cross-sectional shape.

4. The insulated electrical conductor according to claim 1 or 2, wherein the insulating coating comprises polyaryl ether ketone (PAEK).

5. The insulated electrical conductor according to claim 1 or 2, wherein the insulating coating further comprises one or more fibers, fillers, or combinations thereof.

6. The insulated electrical conductor according to claim 1 or 2, wherein the insulating coating is substantially composed of polyaryl ether ketone (PAEK).

7. The insulated electrical conductor according to claim 1 or 2, wherein the insulating coating comprises a polymer selected from the group consisting of polyetherketone (PEK), polyetheretherketone (PEEK), polyetherketoneketone (PEKK), polyetheretherketoneketone (PEEKK), and polyetherketoneetherketoneketone (PEKEKK).

8. The insulated electrical conductor according to claim 1 or 2, wherein the insulating coating comprises a polymer alloy of PAEK and one or more fluororesins.

9. The insulated electrical conductor according to claim 1, wherein the electrical conductor is a wire having a circular cross-section having a tanδ attenuation ratio of 1.10 or less when measured according to the following procedure: a) In a DMA instrument, the coated wire held by the cantilever grip is heated for the first time from room temperature to a temperature T1 corresponding to the peak of endothermic melting (determined by DSC), b) After 1 minute has elapsed at T1, the coated wire is cooled back to room temperature. c) The coated wire is heated to T1 for the second time, d) Determine the slope m1 of the tanδ curve at the start of the thermal transition region of the polymer during the first heating cycle. e) Determine the slope m2 of the tanδ curve at the start of the thermal transition region of the polymer during the second heating cycle, and, f) Calculate the tanδ damping ratio by dividing m1 by m2.

10. The insulated electrical conductor according to claim 1, wherein the electrical conductor is a wire having a rectangular cross-section having a tanδ attenuation ratio of less than 1.60 when measured according to the procedure: a) In a DMA instrument, the coated wire held by the cantilever grip is heated for the first time from room temperature to a temperature T1 corresponding to the peak of endothermic melting (determined by DSC), b) After 1 minute has elapsed at T1, the coated wire is cooled back to room temperature, and b) the coated wire is heated to T1 a second time. c) Determine the slope m1 of the tanδ curve at the start of the thermal transition region of the polymer during the first heating cycle. d) Determine the slope m2 of the tanδ curve at the start of the thermal transition region of the polymer during the second heating cycle, and, e) Calculate the tanδ damping ratio by dividing m1 by m2.

11. The insulated electrical conductor according to claim 1, wherein it is determined that the insulating coating is not peelable from the electrical conductor by making a notch or a slit in the insulating coating, attempting to peel the insulating coating from the notch or the slit along the coated electrical conductor in the longitudinal direction under ambient conditions in air, and observing that the insulating layer does not peel off from the electrical conductor in a complete or partial tubular shape.

12. An electric motor comprising an insulated electrical conductor as described in claim 1.

13. A method for producing an insulated electrical conductor, The objective is to obtain an electrical conductor having an oxide layer on at least a portion of its surface, wherein the electrical conductor contains copper or a copper alloy. Extrude a polymer insulating film onto one or more of the electrical conductor and the oxide layer; Cooling the coated electrical conductor, The method involves heat-treating the cooled coated electrical conductor, wherein the heat treatment includes heating the coated electrical conductor to a temperature above the melting point Tm of the insulating coating so that the insulating coating cannot be peeled off the electrical conductor after the heat treatment, and therefore cannot be peeled off from the electrical conductor in a complete or partial tubular shape. The heat-treated coated electrical conductor is cooled to obtain an insulated electrical conductor, Methods that include...

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