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

Patent metadata

Field	Value
Publication number	US-2020107408-A1
Application number	US-201816611288-A
Country	US
Kind code	A1
Filing date	May 9, 2018
Priority date	May 9, 2017
Publication date	Apr 2, 2020
Grant date	—

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

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).

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 forming comprises dispersing the CNTs within a polymer solution to form a dispersed CNT polymer material, followed by curing the polymer solution.

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

11 . The method of claim 9 , wherein forming includes dispersing the CNTs within the polymer solution using a sonicator, a homogenizer, mechanical stirring, a magnetic stir bar, an external magnetic field, shaking, shearing, or any combination thereof.

12 . The method of claim 11 , 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.

13 . The method of claim 12 , wherein externally applied heat is from a hot plate, radiant heaters, lamps, high-density infrared exposure, drying ovens or any combination thereof.

14 . The method of claim 10 , 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.

15 . The method of claim 10 , wherein the non-volatile organic solvent is selected from N-Methyl-2-pyrrolidone (NMP), acetone, an alcohol, tetrahydrofuran (THF), dichloromethane, and combinations thereof.

16 . The method of claim 9 , wherein forming comprises synthesizing the polymer solution component from a plurality of monomer precursors, of which at least one monomer contains dispersed CNTs.

17 . The method of claim 16 , wherein the monomer containing dispersed CNTs is ethylene glycol.

18 . The method of claim 10 , further comprising:
controlling a viscosity of the joule heating element based on a weight percent of the solvent contained therein.

19 . The method of claim 10 , 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.

20 . The method of claim 19 wherein the miscible liquid added is water.

21 . The method of claim 9 , wherein the CNTs are single-walled, double-walled, multi-walled character, or a combination thereof.

22 . The method of claim 9 , wherein at least one of a diameter, a length, a chirality, or a combination thereof of the CNTs varies.

23 . The method of claim 9 , wherein the CNTs are metallic, semiconducting, or a combination thereof.

24 . The method of claim 9 , 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.

25 . The method of claim 24 , 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.

26 . The method of claim 9 , further comprising:
controlling electrical properties of the joule heating element based on the weight percent CNT content of the joule heating element.

27 . The method of claim 9 , 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.

28 . The method of claim 19 , further comprising:
removing the remaining solvent after shaping to solidify the joule heating element in the desired geometry.

29 . The method of claim 28 , 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.

30 . The method of claim 28 , wherein removing the solvent includes passing an electric current through the mixture, supplied by an applied voltage from 1 V to 500 V.

31 . The method of claim 30 , wherein passing the electric current occurs at ambient pressure or in a vacuum.

32 . The method of claim 30 , wherein passing the electric current occurs while the dispersed CNT polymer composite material is submerged under a liquid.

33 . The method of claim 32 , wherein the liquid is a polar solvent.

34 . The method of claim 33 , wherein the liquid has a moderate to strong dielectric constant.

35 . The method of claim 33 , wherein the liquid is water.

36 . 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.

37 . The method of claim 36 , wherein the external power supply is stationary or portable.

38 . The method of claim 36 , wherein the external power supply is a source of renewable electricity generation.

39 . The method of claim 36 , wherein the electrical contacts comprise a metal material.

40 . The method of claim 39 , wherein the metal material is in the form of a film, a particle deposition, a wire, a sheet, or a mesh.

41 . The method of claim 36 , wherein the electrical contacts comprise a carbon material.

42 . The method of claim 41 , wherein the carbon material is Bucky paper, a CNT/graphene composite solution, carbon fiber, carbon fiber veil, CNT thread, or wire.

43 . The method of claim 36 wherein the electrical contacts comprise a conduc

Assignees

• Univ Cincinnati

Inventors

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

Classifications

• H05B3/286

  the insulating material being an organic material, e.g. plastic · CPC title

• H05B3/36

  heating conductor embedded in insulating material · CPC title

• H05B2214/04

  Heating means manufactured by using nanotechnology · CPC title

• H05B3/145 Primary

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

• H05B3/342

  heaters used in textiles · CPC title