Abstract:
A self-bonding conductive wire and methods in which it is made and used. The wire comprises a conductor, an insulator, and a self-bonding outer coating. The self-bonding outer coating is a polyester polyether block copolymer. The insulator is an ethylene/tetrafluoroethylene copolymer, one or more layers of which may be used to insulate the conductor. The self-bonding capabilities of the wire may be activated by heating the wire, causing the outer coating to thermoplastically deform and fuse, allowing for the creation of self-supporting structures such as large bobbin-less coils. The use of the polyester polyether block copolymer for the self-bonding outer coating is superior to other materials, in which significant degradation of qualitative properties following self-bonding is observed, resulting in a superior self-bonding conductive wire.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    Not applicable 
       STATEMENT RE: FEDERALLY SPONSORED RESEARCH/DEVELOPMENT 
       [0002]    Not applicable 
       BACKGROUND 
       [0003]    1. Technical Field 
         [0004]    The present disclosure relates generally to self-bonding conductive wire. More particularly, the present disclosure relates to the use of polyester polyether block copolymers in self-bonding wire, and methods of making and using such wire. 
         [0005]    2. Related Art 
         [0006]    In the use of conductive wire, it is common that wire may be placed into specific configurations as desired by a user, such as wrapping the wire into coils. Once the wire has been placed into a desired configuration, it becomes necessary to secure the wire in that configuration. This securing may maintain the integrity of the chosen wire configuration, and ensure that the individual wires do not become loose, noisy, or subject to early failure through vibrations and other movement. Securing wire is especially important when the wire is shaped into self-supporting or unusual configuration, such as bobbin-less coils. 
         [0007]    Many conventional ways have been developed to secure wire. In the past, wire has been coated with a liquid or viscous varnish, which hardens following the coating step to maintain the wire&#39;s configuration. It was later found that wires may be made with outer coatings which may self-adhere or self-bond, eliminating the requirement for a varnishing step. 
         [0008]    Various outer coatings have been used which may confer self-adhering or self-bonding properties to wire. Typically, self-bonding is achieved by softening or melting the coating and then allowing the coating to resolidify and fuse. The softening or melting may be performed by application of heat, electricity, or a suitable solvent. However, previously used outer coatings suffer from various deficiencies, such as sharp reductions in melting point, modulus, tensile strength, and elasticity following resolidification and fusion. 
         [0009]    Consequently, there is a need for an improved self-bonding conductive wire. 
       BRIEF SUMMARY 
       [0010]    To solve these and other problems, it is contemplated that a polyester polyether block copolymer material may be used to form a self-bonding coating over a conductive wire, in order to confer superior self-bonding properties to that wire. Particularly, it is contemplated that the polyester polyether block copolymer material may have a durometer hardness (Type D) measured according to ISO 868 of about 30. Such material may be made by known methods of synthesis, or may be obtained commercially from manufacturers such as E.I. DuPont de Nemours and Co., Inc. 
         [0011]    The self-bonding conductive wire may comprise a conductor and a covering disposed over the conductor formed of a polyester polyether block copolymer. The polyester polyether block copolymer may have a durometer hardness (Type D) measured according to ISO 868 of about 30. 
         [0012]    The conductive wire may also have an insulator disposed between the conductor and the covering. The insulator may comprise one or more layers of insulation disposed between the conductor and the covering. The one or more layers of insulation may be a fluoropolymer. The fluropolymer may be an ethylene/tetrafluoroethylene copolymer. 
         [0013]    Such a conductive wire may be made by disposing an insulator over a conductor, and applying a covering over the insulator comprising a polyester polyether block copolymer. The steps of applying the insulation material and the polyester polyether block copolymer covering may be accomplished by extrusion through an extrusion crosshead. 
         [0014]    Such a conductive wire may be used by configuring the wire into a desired configuration, and applying energy to the covering to allow it to thermoplastically deform. The energy may be applied in the form of heat, such as with an oven or heat gun, or in the form of an electric current or chemical reaction. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]    These and other features and advantages of the various embodiments disclosed herein will be better understood with respect to the following description and drawings, in which: 
           [0016]      FIG. 1  is a perspective view of one embodiment of a self-bonding conductive wire; 
           [0017]      FIG. 2  is a detailed perspective cutaway view taken within circle  2  of  FIG. 1 , showing an individual strand of one embodiment of the self-bonding conductive wire; 
           [0018]      FIG. 3  is a cross-sectional view taken upon line  3  of  FIG. 1 , showing one embodiment of the self-bonding conductive wire; and 
           [0019]      FIG. 4  is the same cross-sectional view of  FIG. 3 , shown after the wire of one embodiment of the self-bonding conductive wire has been self-bonded. 
       
    
    
       [0020]    Common reference numerals are used throughout the drawings and the detailed description to indicate the same elements. 
       DETAILED DESCRIPTION 
       [0021]    According to various aspects of the present invention, a new type of self-bonding conductive wire and a related method of using a self-bonding conductive wire is contemplated, which utilizes a self-bonding outer coating comprising a polyester polyether block copolymer. The wire includes a conductor and a self-bonding outer coating over the conductor, and is formed into the desired configuration of the user, such as in a bobbin-less coil or other self-supporting configuration. Subsequently, an energy source such as heat from an oven or heat gun is used to soften the polyester polyether block copolymer of the self-bonding outer coating. Consequently, the self-bonding outer coating associates with the self-bonding outer coating of adjacent strands of wire. The wire may then be removed from the energy source, allowing the self-bonding outer coating to harden, resulting in a bonded outer coating which attaches adjacent strands of wire to one another. It is additionally contemplated that the polyester-polyether block copolymer have a durometer hardness (Type D) measured according to ISO 686 of about 30, such as those which may be obtained commercially from polymer manufacturers such as E.I. DuPont de Nemours and Co. Inc. It is further contemplated that one or more layers of insulation may be disposed between the conductor and the self-bonding outer coating, and that the insulator may be an ethylene/tetraflouroethylene (“ETFE”) copolymer. 
         [0022]    Referring now to the drawings, and more particularly to  FIG. 1 , a self-bonding conductive wire  10  according to an exemplary embodiment of the present invention is shown. It may be seen that the self-bonding conductive wire  10  may be formed into a desired configuration by a user, such as a coil  12 . However, it may also be seen that the self-bonding conductive wire  10  may be formed into many other configurations. The coil  12  of the exemplary embodiment of the self-bonding conductive wire  10  may find particular utility in certain application because it may not require a bobbin, and may be self-supporting, even when formed into coils of great size. 
         [0023]    Referring now to  FIG. 2 , a cutaway view of an individual strand of the self-bonding conductive wire  10  of the exemplary embodiment is shown. A self-bonding conductive wire  10  may have a conductor  14 , an insulator  16  disposed over the conductor  14 , and a self-bonding outer coating  18  disposed over the insulator  16  and the conductor  14 . 
         [0024]    The conductor  14  may be any conductive material usable in the making and using of conductive wire. For example, but without limitation, the conductor  14  may be a conductive metal such as copper, silver, or aluminum However, it may also be seen that the conductor  14  may not only be limited to electrically conductive materials, but may also include other signal conductors or transmitters, including but not limited to fiber optics, waveguides, or lasing mediums. Further, it may be seen that the conductor  14  may comprise a single wire of conductive material, or may also be a plurality of wires of conductive material as shown in the exemplary embodiment. Such a plurality of wires of conductive material may allow, for example, multiple signals to be conveyed over a single self-bonding conductive wire, or for greater flexibility, kink-resistance, and break-resistance in the self-bonding conductive wire  10 . 
         [0025]    The insulator  16  may be any insulative material useable in conductive wire. In the exemplary embodiment, the insulator  16  is a fluoropolymer, and more specifically, an ETFE copolymer. However, it may also be seen that the insulator  16  may be, for example but without limitation, other insulation materials known in the art and usable in conductive wire, such as silicon rubber or fiber reinforced plastic. The insulator  16  may comprise a single layer of insulative material, or multiple layers of insulative material. In the exemplary embodiment, a single layer of insulation is shown, but multiple layers of insulation comprising the same or different insulation material may also be used without departing from the scope of the present disclosure. 
         [0026]    The self-bonding outer coating  18  may comprise a polyester polyether block copolymer. In the exemplary embodiment, the self-bonding outer coating  18  is a polyester polyether block copolymer having a durometer hardness (Type D) measured according to ISO 868 of about 30. Such a polyester polyether block copolymer may be synthesized by methods known in the art. For example, a polyester-polyether block copolymer may be synthesized with a narrow molecular weight distribution and chain length according to the methods described by Yasuda, Aida and Inoue in their article  Synthesis of Polyester - Polyether Block Copolymer with Controlled Chain Length from β - Lactone and Epoxide by Aluminum Porphyrin Catalyst , published in  Macromolecules  1984, 17, 2217-2222. The polyester polyether block copolymer may also be obtained commercially from companies such as E.I. DuPont de Nemours and Co. Inc., as sold under the trade name Hytrel®. The polyester polyether block copolymer of the exemplary embodiment in particular has a durometer hardness (Type D) measured according to ISO 868 of about 30, which corresponds to DuPont&#39;s Hytrel® 3078 commercial product. 
         [0027]    Other qualities of the polyester polyether block copolymer used in the exemplary embodiment include the following: 
         [0000]    
       
         
               
               
             
           
               
                   
               
             
             
               
                 Flexural Modulus measured according to ISO 128 at −40° C. 
                 145 
               
               
                 Flexural Modulus measured according to ISO 128 at 28° C. 
                 28 
               
               
                 Flexural Modulus measured according to ISO 128 at 100° C. 
                 14 
               
               
                 Melting Point measured according to ISO 1346 
                 170° C. 
               
               
                 Vicat Softening Temperature measured according to ISO 306 
                  83° C. 
               
               
                 (Rate B) 
               
               
                 Specific Gravity 
                 1.07 
               
               
                   
               
             
          
         
       
     
         [0028]    However, it may be seen that the polyester polyether block copolymer used may vary in, for example but without limitation, molecular weight and chain length. Such variations may result in variations in the observable properties of the self-bonding outer coating  18  from those listed above, without departing from the scope of the present disclosure. 
         [0029]    The use of a polyester polyether block copolymer to form the self-bonding outer coating  18 , as in the exemplary embodiment, may have particular advantages, including a resistance to the degradation of material qualities pertinent to the structural integrity of the outer coatings of conductive wire. Such material properties may include melting point, modulus, tensile strength, and elasticity. It may be seen that in conventional self-bonding materials, or even in thermoplastic materials including random copolymers, thermoplastic softening may result in sharp reductions in these qualities following resolidification. The use of a polyester polyether block copolymer may, however, strongly mitigate these sharp reductions, as well as provide strong resistance to deterioration from many industrial chemicals, oils and solvents, and the necessary flexibility required in a wire application, due to the unique characteristics of the polyester polyether block copolymer. 
         [0030]    Referring now to  FIG. 3 , the self-bonding conductive wire  10 , when formed into a user&#39;s desired configuration, such as the coil  10  of the exemplary embodiment, may have a one or more individual strands of wire proximal to one another, with the self-bonding outer coatings  18  of the strands of wire preferably in physical contact with one another. Once the self-bonding conductive wire  10  has been configured into a desired configuration, such as the coil  12  of the exemplary embodiment, energy may be applied to the self-bonding outer coating  18 , causing the polyester polyether block copolymer to thermoplastically deform and self-bond. 
         [0031]    Such application of energy may include, for example, but without limitation, heat from a heat gun or oven, electricity, or chemical energy from a chemical reaction. However, it may be seen that any application of energy which may cause the polyester polyether block copolymer of the self-bonding outer coating  18  to thermoplastically deform and self-bond may be utilized. In one particular exemplary method, a user may place a formed coil  12  into an oven for a period of time suitable for the self-bonding outer coating  18  to self-bond. However, it may also be seen that in other configurations, it may be preferable to apply heat to only particular portions of the formed self-bonding conductive wire  10 , such as those portions which are self-contacting. In those situations, a heat gun may be a preferred method of applying energy to the self-bonding outer coating  18 . 
         [0032]    Referring now to  FIG. 4 , following the application of energy which may cause the self-bonding outer coating  18  to thermoplastically deform, the self-bonding outer coating  18  may then be allowed to resolidify. Thus, the individual strands of self-bonding conductive wire  10  may be, in such a fashion, fused into a contiguous structure having the same desired form as configured by the user prior to the application of energy to the self-bonding outer coating  18 . For example, in the exemplary embodiment, the resulting bonded coil  12  of  FIG. 4  has the same approximate shape of the unbounded coil  12  of  FIG. 3 , but the individual strands of self-bonding conductive wire  10  are no longer loose, but instead are retained by the resolidified and fused self-bonding outer coating  18 . Such fusion may allow, for example, a configuration of self-bonding conductive wire  10  to be self-supporting, without requiring the use of extra added materials or equipment. Further, such fusion may mitigate the risk of individual strands becoming loose, noisy, or subject to early failure through vibrations and other movement. 
         [0033]    With the structural features of the self-bonding conductive wire  10  described above, the following discussion concerns methods of making and using the self-bonding conductive wire  10  according to other aspects of the present invention. Such a self-bonding conductive wire  10  as described above may be made by any methods known in the art of making conductive wire. One of these methods may be, for example, passing a conductor  14  through a series of extrusion crossheads. The initial extrusion crosshead may, in one particular embodiment, coat the conductor  14  with a resinous insulator  16  such as a fluropolymer like ETFE. It may be seen that repeating the flowing of the conductor though the same or other extrusion crossheads may result in additional coatings of resinous materials, such as extra layers of insulation. The final extrusion crosshead may coat the conductor  14  and any materials disposed over the conductor by previous coatings, such as an insulator  16 , with a self-bonding outer coating  18  comprising a polyester polyether block copolymer. 
         [0034]    To use the self-bonding conductive wire  10  as described above, a user may first form the self-bonding conductive wire  10  into a desired configuration. Following this forming, the user may then apply energy sufficient to cause the polyester polyether block copolymer of the self-bonding outer coating  18  to thermoplastically deform. Such application of energy may be accomplished by, for example but without limitation, the application of heat through an oven or heat gun, or the application of electrical current or chemical energy. The user may then remove the energy source, and allow the self-bonded outer coating  18  to solidify, resulting in the fusion of the self-bonding outer coating  18  around strands of wire positioned proximally prior to the application of energy. 
         [0035]    The above description is given by way of example, and not limitation. Given the above disclosure, one skilled in the art could devise variations that are within the scope and spirit of the invention disclosed herein, including various types of conductors  14 , insulators  16 , or methods of applying energy to the self-bonding outer coating  18 . Further, the various features of the embodiments disclosed herein can be used alone, or in varying combinations with each other and are not intended to be limited to the specific combination described herein. Thus, the scope of the claims is not to be limited by the illustrated embodiments.