Anisotropic heat transfer, electromagnetic interference shielding composite and method for preparation thereof

Patent metadata

Field	Value
Publication number	US-11612088-B2
Application number	US-202117480152-A
Country	US
Kind code	B2
Filing date	Sep 21, 2021
Priority date	Oct 28, 2020
Publication date	Mar 21, 2023
Grant date	Mar 21, 2023

Abstract

The present invention provides an anisotropic, thermal conductive, electromagnetic interference (EMI) shielding composite including a plurality of aligned polymer nanofibers to form a polymer mat or scaffold having a first and second planes of orientation of the polymer nanofibers. The first plane of orientation of the polymer nanofibers has a thermal conductivity substantially the same as or similar to that of the second plane, and the thermal conductivity of the first or second plane of orientation of the polymer nanofibers is at least 2-fold of that of a third plane of orientation of the polymer nanofibers which is about 90 degrees out of the first and second planes of orientation of the polymer nanofibers, respectively, while the electrical resistance of each of the first and second planes is at least 3 orders lower than that of the third plane. A method for preparing the present composite is also provided.

First claim

The invention claimed is:

1. An anisotropic, electrical conductive and thermal conductive, electromagnetic interference shielding composite comprising:
a plurality of aligned polymer nanofibers to form a polymer mat or scaffold having a first plane and a second plane of orientation of the polymer nanofibers with a thermal conductivity of at least 2-fold higher than that of a third plane of orientation of the polymer nanofibers,
each of the polymer nanofibers being incorporated with a plurality of thermal conductive fillers and a plurality of a first metal compound electrospun with a polymer to form a plurality of electrospun polymer nanofibers with a core or polymer matrix of the thermal conductive fillers and the first metal compound in the polymer nanofibers and deposited with a plurality of a second metal compound on the surface of the electrospun polymer nanofibers to form the plurality of aligned polymer nanofibers,
the composite having the thermal conductivity of at least about 110 W/mK along the first and second planes of orientation of the polymer nanofibers and an electromagnetic interference shielding effectiveness against electromagnetic waves at lower frequency from 100 MHz to 1.5 GHz or higher frequency from 1.5 GHz to 30.0 GHz comparable to or slightly higher than that of the corresponding pure metal of the first or second metal compound, and
the first and second planes of orientation of the aligned polymer nanofibers having substantially identical or similar electrical conductivities and resistances which the electrical resistance of each of the first and second planes of orientation is at least 3 orders lower than that of a third plane of orientation of the polymer nanofibers.

2. The composite of claim 1 , wherein the thermal conductive fillers and first metal compound are jointly or independently one or more of carbon nanotubes, boron nitrates, aluminum nitride, ceramic polymers and metal nanoparticles.

3. The composite of claim 1 , wherein the second metal compound comprises one or more of silver, nickel, platinum and copper, or the metal alloy thereof.

4. The composite of claim 1 , wherein the polymer comprises one or more of polyacrylonitrile (PAN), poly(vinylidene fluoride) (PVDF), polyimide (PI), poly(lactic acid) (PLA), caboxymethyl cellulose (CMC), and poly(vinyl pyrrolidone) (PVP).

5. The composite of claim 1 , wherein the polymer:thermal conductive fillers:first metal compound is in a weight ratio of about 50:1-4:8-32.

6. The composite of claim 1 , wherein the first metal compound:second metal compound is in a weight ratio of about 1.8:1.

7. The composite of claim 1 , wherein the second metal compound is deposited on the electrospun polymer nanofibers by one or more of electroless plating, chemical vapor deposition, physical vapor deposition, plasma-enhanced chemical vapor deposition and thermal evaporation methods.

8. A method for preparing the composite of claim 1 , comprising:
providing a solution of the thermal conductive fillers including dispersing the thermal conductive fillers into a solvent for a first period of time;
dissolving the polymer into the solution of the thermal conductive fillers at a temperature for a second period of time to obtain a solution of the thermal conductive fillers and polymer;
mixing the first metal compound with the solution of the thermal conductive fillers and polymer for a third period of time to obtain a solution of the thermal conductive fillers, polymer and first metal compound;
electrospinning the solution of the thermal conductive fillers, polymer and first metal compound to generate a plurality of aligned, electrospun polymer nanofibers;
drying the aligned, electrospun polymer nanofibers;
reducing the first metal compound to become metal nanoparticles;
compressing the aligned, electrospun polymer nanofibers to obtain a mat or scaffold of aligned, electrospun polymer nanofibers;
depositing a solution of the second metal compound onto each of the aligned, electrospun polymer nanofibers electrolessly; and
sintering the mat or scaffold of the aligned, electrospun polymer nanofibers to obtain the composite.

9. The method of claim 8 , wherein the solvent used to dissolve the thermal conductive fillers comprises dimethylformamide (DMF), dimehtylacetamide (DMAC), N-Methyl-2-pyrrolidone (NMP) and acetone.

10. The method of claim 8 , wherein the electrospinning is carried out by an electrospinning device set at a voltage of about 20 to 40 kV, feed rate of about 1 to 5 ml/hour, and a rotational speed of about 150 to 300 rpm.

11. The method of claim 8 , wherein the reducing of the first metal compound into nanoparticles comprises subjecting the aligned, electrospun polymer nanofibers to high intensity UV light with about 70% of power and for about 5 minutes on each side of the aligned, electrospun polymer nanofibers.

12. The method of claim 8 , wherein the compressing of the aligned, electrospun polymer nanofibers is carried out at about 100° C. to 300° C., 100N to SOON and for about 30 to 300 seconds.

13. The method of claim 8 , wherein the depositing of the solution of the second metal compound onto the each of the aligned, electrospun polymer nanofibers electrolessly comprises immersing the aligned, electrospun polymer nanofibers into a solution containing one or both of silver nitrates and copper (II) sulfate for about 20-40 minutes at about 25 to 40° C., followed by rinsing in sufficient amount of deionized water and air drying.

14. The method of claim 8 , wherein the sintering is carried out in tube furnace at about 500° C. to 700° C. and for about 10 to 60 minutes.

15. The method of claim 8 , wherein the thermal conductive fillers and first metal compounds are one or more of carbon nanotubes, boron nitrates, aluminum nitride, and ceramic polymers and metal nanoparticles.

16. The method of claim 8 , wherein the polymer comprises one or more of polyacrylonitrile (PAN), poly(vinylidene fluoride) (PVDF), polyimide (PI), poly(lactic acid) (PLA), caboxymethyl cellulose (CMC), and poly(vinyl pyrrolidone) (PVP).

17. The method of claim 8 , wherein the polymer:thermal conductive fillers:first metal compound is in a weight ratio of about 50:1-4:8-32.

18. The method of claim 8 , wherein the first metal compound: second metal compound is in a weight ratio of about 1.8:1.

19. An anisotropic heat transfer material comprising the composite of claim 1 .

20. An electromagnetic interference shielding apparatus comprising the composite of claim 1 .

Assignees

• Nano & Advanced Materials Inst Ltd

Inventors

• Kwok Chi Ho
• Hsu Mei Mei
• Lee Ka I
• Liu Chenmin

Classifications

• D06M11/83

  with metals; with metal-generating compounds, e.g. metal carbonyls; Reduction of metal compounds on textiles · CPC title

• D01F6/54

  of polymers of unsaturated nitriles · CPC title

• D10B2403/0242

  enhancing chemical properties · CPC title

• D04H1/728

  by electro-spinning {(electro-spinning methods and apparatus D01D5/0007)} · CPC title

• D04H1/74 Primary

  the fibres being orientated, e.g. in parallel {(anisotropic fleeces)} · CPC title