Polymer-coated wires
The present disclosure provides insulated electrical conductors, e.g., wires, and methods for producing such insulated electrical conductors to combat partial discharge by enhancing bond strength between the electrical conductor and a base insulating thermoplastic layer (e.g., including a PAEK). Such insulated electrical conductors can include: an electrical conductor; an insulating coating on at least a portion of a surface of the electrical conductor; and an oxide layer between the electrical conductor and the insulating coating. Methods for producing such insulated electrical conductors can involve extrusion of an insulating polymer onto the electrical conductor under ambient atmosphere and a subsequent heat treatment step, which can also be conducted under ambient atmosphere.
1. An insulated electrical conductor, comprising:
an electrical conductor comprising an oxide layer on at least part of a surface of the electrical conductor; and
an insulating coating on at least a portion of the oxide layer,
wherein:
a combination of the electrical conductor and the insulating coating has been subjected to heat treatment after the insulating coating is applied to at least the portion of the oxide layer, the heat treatment comprising heating to a temperature at or greater than the glass transition temperature of the insulating coating; and
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 strippable from the electrical conductor after the heat treatment.
2. The insulated electrical conductor of claim 1 , wherein the electrical conductor has a cross-sectional shape that is round, square, triangular, rectangular, polygonal, or elliptical.
3. The insulated electrical conductor of claim 1 , wherein the electrical conductor comprises copper, aluminum, or a combination or alloy thereof.
4. The insulated electrical conductor of claim 3 , wherein the electrical conductor comprises copper or a copper alloy.
5. The insulated electrical conductor of claim 1 , wherein the electrical conductor comprises a silver, nickel, or gold coating.
6. The insulated electrical conductor of claim 1 , wherein the insulating coating comprises a polyaryl ether ketone (PAEK).
7. The insulated electrical conductor of claim 1 , wherein the insulating coating further comprises one or more fibers, fillers, or a combination thereof.
8. The insulated electrical conductor of claim 1 , wherein the insulating coating consists essentially of a polyaryl ether ketone (PAEK).
9. The insulated electrical conductor of claim 1 , wherein the insulating coating comprises a polymer selected from the group consisting of polyether ketone (PEK), polyether ether ketone (PEEK), polyetherketoneketone (PEKK), polyether ether ketone ketone (PEEKK), and polyether ketone ether ketone ketone (PEKEKK).
10. The insulated electrical conductor of claim 1 , wherein the insulating coating comprises a polymeric alloy of a PAEK with one or more fluororesins.
11. The insulated electrical conductor of claim 1 , wherein the insulating coating being not strippable from the electrical conductor is determined by initiating a nick or tear in the insulating coating; peeling the insulating coating from the nick or tear lengthwise in air under ambient conditions along the coated electrical conductor to attempt to peel the insulating coating off the conductor; and observing that the insulating layer is not peeled from the electrical conductor in full or partial tubular form.
12. An electric motor comprising the insulated electrical conductor of claim 1 .
13. A method of preparing the insulated electrical conductor of claim 1 , comprising:
providing an electrical conductor comprising an oxide layer on at least part of a surface of the electrical conductor;
extruding a polymeric insulating coating onto one or more of the electrical conductor and the oxide layer such that the insulating coating is not strippable from the electrical conductor, wherein the extruding is conducted 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 provide the insulated electrical conductor.
14. An insulated electrical conductor, prepared according to the method of claim 13 .
15. The insulated electrical conductor of claim 1 , wherein the electrical conductor is a wire.
16. The insulated electrical conductor of claim 15 , wherein the insulating coating comprises a polyaryl ether ketone (PAEK).
17. The insulated electrical conductor of claim 15 , wherein the insulating coating further comprises one or more fibers, fillers, or a combination thereof.
18. The insulated electrical conductor of claim 15 , wherein the insulating coating consists essentially of a polyaryl ether ketone (PAEK).
19. The insulated electrical conductor of claim 15 , wherein the insulating coating comprises a polymer selected from the group consisting of polyether ketone (PEK), polyether ether ketone (PEEK), polyetherketoneketone (PEKK), polyether ether ketone ketone (PEEKK), and polyether ketone ether ketone ketone (PEKEKK).
20. The insulated electrical conductor of claim 15 , wherein the insulating coating comprises a polymeric alloy of a PAEK with one or more fluororesins.
21. The insulated electrical conductor of claim 1 , wherein the electrical conductor is a wire with a circular cross-section that has a tan δ damping ratio of 1.10 or less when measured according to the following procedure:
a) heating a coated wire held by a cantilever grip in a DMA instrument a first time from room temperature up to a temperature, T1, corresponding to a peak of a melting endotherm (determined by DSC);
b) cooling the coated wire back to room temperature after one minute at T1;
c) heating the coated wire a second time up to T1;
d) determining the slope, m1, of the tan δ curve at the start of a thermal transition region of the polymer during the first heating cycle;
e) determining the slope, m2, of the tan δ curve at the start of a thermal transition region of the polymer during the second heating cycle; and
f) calculating the tan δ damping ratio by dividing m1 by m2.
22. The insulated electrical conductor of claim 21 , wherein the electrical conductor comprises copper or a copper alloy.
23. The insulated electrical conductor of claim 1 , wherein the electrical conductor is a wire with a rectangular cross-section that has a tan δ damping ratio of less than 1.60 when measured according to the following procedure:
a) heating a coated wire held by a cantilever grip in a DMA instrument a first time from room temperature up to a temperature, T1, corresponding to a peak of a melting endotherm (determined by DSC);
b) cooling the coated wire back to room temperature after one minute at T1;
c) heating the coated wire a second time up to T1;
d) determining the slope, m1, of the tan δ curve at the start of a thermal transition region of the polymer during the first heating cycle;
e) determining the slope, m2, of the tan δ curve at the start of a thermal transition region of the polymer during the second heating cycle; and
f) calculating the tan δ damping ratio by dividing m1 by m2.
24. The insulated electrical conductor of claim 23 , wherein the electrical conductor comprises copper or a copper alloy.