Process of making conformable, low voltage, light weight joule heating elements

Patent metadata

Field	Value
Publication number	US-11696369-B2
Application number	US-201816611288-A
Country	US
Kind code	B2
Filing date	May 9, 2018
Priority date	May 9, 2017
Publication date	Jul 4, 2023
Grant date	Jul 4, 2023

Abstract

Disclosed are methods of making low voltage joule heating elements ( 10, 40, 50 ) from carbon nanotubes (CNT) ( 32 ). In an embodiment, the heating element ( 10 ) includes layers ( 12 ) of aligned thin film CNTs. In another embodiment, the heating element ( 40 ) includes CNTs ( 32 ) dispersed in a polymer ( 34 ) to form a CNT polymer composite ( 30 ). In another embodiment, the heating element ( 50 ) includes CNT thread ( 52 ) stitched to a fabric ( 54 ). Each embodiment further includes a pair of electrodes ( 20, 22, 42, 44, 56, 58 ) that are configured to be couple to a source of electricity. Embodiments further include an encapsulating film ( 24, 46 ) over at least the heating element. The heating elements ( 10, 40, 50 ) produced by the processes disclosed herein are lightweight and highly efficient and suitable for many uses including incorporation into objects such as clothing and footwear.

First claim

What is claimed is:

1. A method of making a low voltage joule heating element, conformable to its substrate, comprising:
forming said joule heating element from carbon nanotubes (CNTs);
wherein forming comprises dispersing the CNTs within a polymer solution to form a dispersed CNT polymer material, followed by curing the polymer solution;
wherein dispersing the CNTs within the polymer solution includes using a sonicator, a homogenizer, mechanical stirring, a magnetic stir bar, an external magnetic field, shaking, shearing, or any combination thereof; and
wherein dispersing the CNTs with the polymer solution is carried out in the presence of externally applied heat in the range of 50-300° C.

2. The method of claim 1 , wherein forming comprises drawing an aligned layer of the CNTs from a CNT array and stacking two or more aligned layers of the CNTs.

3. The method of claim 2 , wherein the joule heating element comprises from 2 aligned layers to 1000 aligned layers.

4. The method of claim 1 , further comprising:
controlling electrical properties of the joule heating element based on a thickness of the joule heating element.

5. The method of claim 2 , further comprising:
controlling electrical properties of the joule heating element based on a number of the aligned layers.

6. The method of claim 2 , further comprising:
encapsulating the aligned layers of the CNTs in an encapsulating film.

7. The method of claim 6 , wherein the encapsulating film is selected from polymer films, ceramic films, adhesive films, layers of paint, or a combination thereof.

8. The method of claim 6 , wherein the polymer film includes a polyurethane (TPU), a polystyrene, a polyvinyl chloride (PVC), a fluorinated polymer, a hydrogenated butadiene rubber, a polyethylene, a polystyrene, a polypropylene, a polytetrafluoroethylene, a polyimide, a polyamide and combinations thereof.

9. The method of claim 1 , wherein the polymer solution includes a polymer dissolved in a non-volatile organic solvent that is soluble with both the polymer and the CNTs.

10. The method of claim 1 , wherein externally applied heat is from a hot plate, radiant heaters, lamps, high-density infrared exposure, drying ovens or any combination thereof.

11. The method of claim 9 , wherein the polymer is selected from a thermoplastic polyurethane (TPU) such as ethylene glycol and precursor of polyurethane (TPU), polystyrene, polyvinyl chloride (PVC), fluorinated polymers, hydrogenated butadiene rubber, polyethylene, polystyrene, polypropylene, polytetrafluoroethylene, polyimides and polyamides.

12. The method of claim 1 , wherein forming comprises synthesizing the polymer solution component from a plurality of monomer precursors, of which at least one monomer contains dispersed CNTs.

13. The method of claim 9 , further comprising:
adding a liquid, which is completely miscible with the non-volatile organic solvent yet immiscible to the CNT and polymer, to the dispersed CNT polymer solution to drive the separation of 40-90% of the original solvent content by mass from the CNT and polymer components, and resulting in a putty-like consistency that is viscous enough to be handled and shaped.

14. The method of claim 13 wherein the miscible liquid added is water.

15. The method of claim 1 , wherein the CNTs are single-walled, double-walled, multi-walled character, or a combination thereof.

16. The method of claim 1 , wherein at least one of a diameter, a length, a chirality, or a combination thereof of the CNTs varies.

17. The method of claim 1 , wherein the CNTs are metallic, semiconducting, or a combination thereof.

18. The method of claim 1 , further comprising:
shaping the dispersed CNT polymer composite material into a desired geometry for the joule heating element may be carried out by extrusion, rolling, pressing, molding or otherwise physically manipulating.

19. The method of claim 18 , further comprising:
controlling an electrical conductivity of the joule heating element based on a thickness or an amount of the dispersed CNT polymer composite material.

20. The method of claim 1 , further comprising:
controlling electrical properties of the joule heating element based on the weight percent CNT content of the joule heating element.

21. The method of claim 1 , further comprising:
controlling electrical properties of the joule heating element based on the amount and degree of dispersion of the CNTs within the joule heating element.

22. The method of claim 13 , further comprising:
removing the remaining solvent after shaping to solidify the joule heating element in the desired geometry.

23. The method of claim 22 , wherein removing the solvent includes applying an external heat treatment from a hot plate, radiant heater, lamp, high-density infrared exposure, drying oven, freezer or any combination thereof.

24. The method of claim 1 , further comprising:
installing electrical contacts to the joule heating element, the electrical contacts being configured to be coupled to an external power supply;
wherein the electrical contacts comprise a carbon material.

25. The method of claim 24 , wherein the external power supply is stationary or portable.

26. The method of claim 24 , wherein the external power supply is a source of renewable electricity generation.

27. The method of claim 24 , wherein the electrical contacts comprise a metal material.

28. The method of claim 27 , wherein the metal material is in the form of a film, a particle deposition, a wire, a sheet, or a mesh.

29. The method of claim 27 , further comprising:
enhancing the connection of the electrical contacts to the joule heating element material using a solder, a low-melting metal alloy, a conductive epoxy, or a combination thereof.

30. The method of claim 29 , wherein the solder comprises a tin-based solder containing a transition metal.

31. The method of claim 30 , wherein the transition metal comprises chromium, nickel, or a combination thereof.

32. The method of claim 29 , wherein the low-melting metal alloy comprises gallium alloyed with indium.

33. The method of claim 1 , further comprising:
functionalizing the CNTs;
wherein functionalizing includes exposing the CNTs to atmospheric pressure plasma.

34. The method of claim 33 , wherein functionalizing includes exposing the CNTs to an oxidizing chemical or mixtures thereof.

35. A method of making a low voltage joule heating element, conformable to its substrate, comprising:
forming said joule heating element from carbon nanotubes (CNTs);
the forming further comprising stitching a CNT thread to a fabric and installing a first electrode to a first end of the CNT thread and a second electrode at a second end of the CNT thread;
wherein the CNT thread is stitched to the fabric at a density to increase the weight of the stitched area of fabric by up to 20% g/cm 2 , or at a density between 100 and 10,000 stitches per cm 2 .

36. A low voltage joule heating element prepared by the process of claim 1 .

37. An article including the low voltage heating element of claim 36 .

38. A method of making a low voltage joule heating element, conformable to its substrate, comprising:
forming s

Assignees

• Univ Cincinnati

Inventors

• Torrico Noe Alvarez
• Noga Ryan
• Gbordzoe Seyram
• Shanov Vesselin N

Classifications

• H05B3/36

  heating conductor embedded in insulating material · CPC title

• H05B3/145 Primary

  Carbon only, e.g. carbon black, graphite · CPC title

• H05B3/0014

  Devices wherein the heating current flows through particular resistances · CPC title

• H05B2214/04

  Heating means manufactured by using nanotechnology · CPC title

• H05B3/342

  heaters used in textiles · CPC title