A polyurethane high thermal conductivity film containing covalently bonded three-dimensional carbon, and a preparation method and application thereof

Abstract

The present invention belongs to the technical field of photothermal controllability, and discloses a polyurethane high thermal conductivity film containing covalently bonded three-dimensional carbon, a preparation method and an application thereof. The polyurethane high thermal conductivity film is prepared by ultrasonically dissolving three-dimensional carbon composite powder in an organic solvent, adding a thermoplastic polyurethane solution for assembly to obtain a three-dimensional carbon / polyurethane assembly, evaporating and concentrating, dropping it on a glass substrate, and then subjecting it to heat treatment. The three-dimensional carbon composite powder is obtained by covalently grafting functionalized short carbon nanotubes with small pieces of reduced graphene oxide. The covalently bonded three-dimensional carbon accounts for 0.5-5% of the mass of the three-dimensional carbon / polyurethane assembly. In the polyurethane high thermal conductivity film, the three-dimensional carbon material is relatively uniformly distributed, can form an effective heat conduction network, has a high thermal conductivity and good mechanical properties, and is expected to be applied in the field of photothermal controllability.

Description

Technical Field

[0001] The present invention belongs to the technical field of photothermal controllability, and more specifically, relates to a polyurethane high thermal conductivity film containing covalently bonded three-dimensional carbon, a preparation method thereof, and an application thereof. Background Art

[0002] The lightweight and highly integrated development of electronic devices inevitably leads to serious heat accumulation, resulting in an increasing demand for effective heat dissipation of multifunctional materials. Polymer-based composite materials with the advantages of light weight, strong plasticity, and easy assembly and processing have attracted more and more attention and research from researchers in the field of photothermal controllable thin films.

[0003] Thermoplastic polyurethane is a polymer with good tensile strength, tear strength, and plasticity. However, the thermal conductivity of thermoplastic polyurethane is relatively low, and researchers mostly improve the thermal conductivity of thermoplastic polyurethane by adding high thermal conductivity materials. Graphene is a two-dimensional material in which carbon atoms are connected by sp 2 hybridization and has a honeycomb lattice structure. It has excellent mechanical properties and thermal conductivity. Carbon nanotubes are tubular materials composed of several layers of carbon atoms arranged in a hexagonal pattern, with excellent mechanical properties and thermal conductivity. In the existing technology, some scholars improve the thermal conductivity by directly adding high thermal conductivity materials such as carbon materials or by pressing tablets into thermoplastic polyurethane. In addition, some scholars improve the thermal conductivity of thermoplastic polyurethane by adding a large amount of materials with high thermal conductivity. Improving mechanical and processing properties, reducing costs, and preventing material agglomeration to form an effective heat conduction network are the current development directions of polymer thin films. Summary of the Invention

[0004] In order to solve the above-mentioned deficiencies and drawbacks of the existing technology, the present invention provides a polyurethane high thermal conductivity film containing covalently bonded three-dimensional carbon. The polyurethane high thermal conductivity film containing covalently bonded three-dimensional carbon is obtained by assembling a three-dimensional carbon complex and a thermoplastic polyurethane solution to form a three-dimensional carbon / polyurethane assembly, and then preparing a thermal conductivity film through heat treatment, which can form an effective heat conduction network and solve the technical problem of low thermal conductivity of thermoplastic polyurethane.

[0005] Another object of the present invention is to provide a preparation method of the above-mentioned polyurethane high thermal conductivity film containing covalently bonded three-dimensional carbon. The method is to react p-phenylenediamine and short carbon nanotubes through diazonium salt reaction and free radical addition reaction to obtain functionalized short carbon nanotubes, then covalently graft the functionalized short carbon nanotubes with small pieces of reduced graphene oxide, and then add the obtained three-dimensional carbon complex dispersion liquid into thermoplastic polyurethane to obtain a three-dimensional carbon / polyurethane assembly through solution assembly. Subsequently, the concentrated solution of the three-dimensional carbon / polyurethane assembly is dropped on a glass substrate, and a polyurethane high thermal conductivity film containing covalently bonded three-dimensional carbon is obtained through heat treatment.

[0006] The object of the present invention is achieved by the following solutions:

[0007] A polyurethane high thermal conductivity film containing covalently bonded three-dimensional carbon. The polyurethane high thermal conductivity film containing covalently bonded three-dimensional carbon is prepared by dissolving three-dimensional carbon composite powder in an organic solvent and ultrasonicating, then adding a thermoplastic polyurethane solution for assembly to obtain a three-dimensional carbon / polyurethane assembly, evaporating and concentrating, dropping it on a glass substrate, and preparing it by heat treatment; the three-dimensional carbon composite powder is obtained by covalently grafting functionalized short carbon nanotubes and small pieces of reduced graphene oxide; the covalently bonded three-dimensional carbon is 0.5-5% of the mass of the three-dimensional carbon / polyurethane assembly.

[0008] Preferably, the size of the small pieces of reduced graphene oxide is 0.1-0.8 μm 2 .

[0009] Preferably, the functionalized short carbon nanotubes are obtained by adding short carbon nanotubes to a diazonium salt solution and carrying out a diazonium salt reaction and a free radical addition reaction at 25-40 °C; the diazonium salt solution is prepared by adding p-phenylenediamine and NaNO 2 to an HCl solution under an ice bath.

[0010] More preferably, the length of the short multi-walled carbon nanotubes is 300-700 nm, and the tube diameter is 5-30 nm.

[0011] More preferably, the mass ratio of the short carbon nanotubes to p-phenylenediamine is 1:(1.08-4.32)×10 -4 ; the molar ratio of p-phenylenediamine, NaNO 2 and HCl is (l-2):(1-2):(3-10); the mass ratio of the short carbon nanotubes to the small pieces of reduced graphene oxide is 1:(0.25-4).

[0012] Preferably, the organic solvent is one or more of N,N-dimethylformamide (DMF), tetrahydrofuran or dimethylacetamide (DMAC).

[0013] Preferably, the thermoplastic polyurethane solution is obtained by adding thermoplastic polyurethane to a mixed solution of DMF and tetrahydrofuran and stirring until the thermoplastic polyurethane is dissolved at 25-40 °C.

[0014] The preparation method of the polyurethane high thermal conductivity film containing covalently bonded three-dimensional carbon includes the following specific steps:

[0015] S1. Add the short carbon nanotube dispersion to the diazonium salt solution, stir at 25-40 °C, wash, filter by suction, dry in vacuum, and redisperse to obtain a functionalized short carbon nanotube dispersion;

[0016] S2. Mix the small-piece reduced graphene oxide dispersion with the functionalized short carbon nanotube dispersion, then add NaNO₂, stir at 25 - 40 °C, wash, filter by suction, dry under vacuum, and grind to obtain a covalently bonded three-dimensional carbon composite powder; dissolve the covalently bonded three-dimensional carbon composite powder in an organic solvent and sonicate to obtain a covalently bonded three-dimensional carbon dispersion. 2 , stir at 25 - 40 °C, wash, filter by suction, dry under vacuum, and grind to obtain a covalently bonded three-dimensional carbon composite powder; dissolve the covalently bonded three-dimensional carbon composite powder in an organic solvent and sonicate to obtain a covalently bonded three-dimensional carbon dispersion.

[0017] S3. Add thermoplastic polyurethane to the mixed solution of DMF and tetrahydrofuran, stir at 25 - 40 °C until the thermoplastic polyurethane dissolves to obtain a thermoplastic polyurethane solution.

[0018] S4. Add the covalently bonded three-dimensional carbon dispersion to the thermoplastic polyurethane solution and stir. After obtaining a three-dimensional carbon / polyurethane assembly dispersion by solution assembly, evaporate and concentrate at 130 - 180 °C. Drop the concentrated three-dimensional carbon / polyurethane assembly solution evenly onto a glass substrate and dry at 45 - 80 °C to obtain a polyurethane high thermal conductivity film containing covalently bonded three-dimensional carbon.

[0019] Preferably, in step S1, the stirring time is 3 - 6 h, and the vacuum drying time is 24 - 48 h; in step S2, the ratio of the small-piece reduced graphene oxide dispersion, the functionalized short carbon nanotube dispersion, and NaNO₂ is (100 - 300) mL : (100 - 300) mL : (0.1 - 0.2) mmol, the stirring time is 4 - 8 h, and the sonication time is 20 - 50 min; in step S3, the mass-to-volume ratio of the thermoplastic polyurethane to the mixed solution is (0.9 - 1.5) g : (16 - 32) mL, and the volume ratio of DMF to tetrahydrofuran in the mixed solution is 1:1; in step S4, the volume ratio of the covalently bonded three-dimensional carbon dispersion to the thermoplastic polyurethane solution is (1 - 3) : (4 - 16); the stirring time is 1 - 2 h. It should be noted that if the liquid is too little after concentration, it is difficult to suck and form, and if the liquid is too much, it will cause unevenness on the surface of the film or even difficulty in film formation in the subsequent film-forming process.

[0020] Application of the polyurethane high thermal conductivity film containing covalently bonded three-dimensional carbon in the field of photothermal controllable thin films.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1. In the polyurethane high thermal conductivity film containing covalently bonded three-dimensional carbon of the present invention, the three-dimensional carbon material is evenly distributed, can form an effective heat conduction network, has a high thermal conductivity and good mechanical properties, and is expected to be applied in the field of photothermal control.

[0023] 2. In the high thermal conductivity polyurethane film containing covalently bonded three-dimensional carbon of the present invention, since covalent bonds are used as the connection between graphene and carbon nanotubes, the interaction force between graphene and carbon nanotubes is increased, an effective heat conduction network can be better formed, and the thermal conductivity is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 TEM photograph of the covalently bonded three-dimensional carbon prepared in Example 1;

[0025] Figure 2 TEM photograph of the covalently bonded three-dimensional carbon prepared in Example 2;

[0026] Figure 3 TEM photograph of the covalently bonded three-dimensional carbon prepared in Example 3;

[0027] Figure 4 Physical diagram of the high thermal conductivity polyurethane film containing covalently bonded three-dimensional carbon prepared in Example 1.

[0028] Figure 5 Thermal conductivity of the polyurethane film containing covalently bonded three-dimensional carbon prepared in Examples 1-5. DETAILED DESCRIPTION OF THE INVENTION

[0029] The content of the present invention will be further described below in conjunction with specific examples, but it should not be construed as a limitation to the present invention. Unless otherwise specified, the technical means used in the examples are conventional means well known to those skilled in the art. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the technical field.

[0030] Example 1

[0031] 1. Preparation of a small piece of reduced graphene oxide dispersion:

[0032] (1) Mix 360 mL of concentrated sulfuric acid and 40 mL of concentrated phosphoric acid, pour them into a beaker containing 3 g of flake graphite powder, and then slowly add 18 g of KMnO 4 under an ice bath, stir at 50 °C for 12 h, and pour it onto ice cubes made by mixing 10 mL of 30% H 2 O 2 and 400 mL of deionized water and freezing;

[0033] (2) Let it stand to remove the upper acid solution, add deionized water to dilute it, and repeat (let it stand - remove the upper acid solution - add deionized water to dilute) 7 times until the pH value of the suspension is 6-7. Centrifuge at a speed of 4000 r / min to obtain the upper suspension, and then centrifuge at a speed of 10000 r / min to take the lower precipitate, filter and dry it, and redisperse it to prepare a 1 mg / mL graphene oxide dispersion.

[0034] (3) Weigh 300 mL of the above graphene oxide dispersion, add NaOH to adjust the pH value to 9, and then add 2.4 g of NaBH 4 Stir to make it evenly dispersed, then react at 85 °C for 2 h under nitrogen protection. After washing with deionized water multiple times and suction filtration, vacuum dry at room temperature for 48 h, and then redisperse in deionized water to obtain a 1 mg / mL large flake reduced graphene oxide dispersion;

[0035] (4) Put the large flake reduced graphene oxide dispersion into a cell crusher and ultrasonicate for 2 h, and then use a cell washer to ultrasonicate for 4 h to obtain a small flake reduced graphene oxide dispersion. The size of the small flake reduced graphene oxide is 0.1 - 0.8 μm 2 ,

[0036] 2. Preparation of functionalized short carbon nanotubes:

[0037] (1) Weigh 1.5 g of multi-walled carbon nanotubes and 300 mL of concentrated hydrochloric acid and place them in a round-bottom flask for mixing. Stir for 4 h, dilute with deionized water to neutral, suction filter and then vacuum dry for 24 h to obtain purified multi-walled carbon nanotubes;

[0038] (2) Add 0.4 g of purified multi-walled carbon nanotubes to a conical flask containing 120 mL of concentrated sulfuric acid and 40 mL of concentrated nitric acid. Stir in a water bath at 75 °C for 10 h, ultrasonicate for 4 h, wash, suction filter and vacuum dry for 48 h, grind with a mortar to obtain short carbon nanotube powder, and redisperse to obtain a 1 mg / mL short carbon nanotube dispersion; The length of the short multi-walled carbon nanotubes is 300 - 700 nm, and the tube diameter is 5 - 30 nm.

[0039] (3) Add 0.2 mmol of p-phenylenediamine and 0.1 mmol of NaNO 2 to a conical flask, add an HCl solution 4 times the molar amount of p-phenylenediamine, and stir in an ice bath for 1 h to obtain a diazonium salt solution;

[0040] (4) Measure 100 mL of the short carbon nanotube dispersion and add it to the diazonium salt solution. Stir at 40 °C for 4 h, wash, suction filter and vacuum dry for 48 h, and redisperse to obtain a functionalized short carbon nanotube dispersion.

[0041] 3. Preparation of covalently bonded three-dimensional carbon composite: Mix 300 mL of the small flake reduced graphene oxide dispersion obtained in step 1 with 100 mL of the functionalized short carbon nanotube dispersion obtained in step 2, add 0.1 mmol of NaNO 2 , stir at 40 °C for 6 h, wash, suction filter, vacuum dry and grind to obtain covalently bonded three-dimensional carbon composite powder.

[0042] 4. Preparation of polyurethane high thermal conductivity film containing covalently bonded three-dimensional carbon

[0043] (1) Add 990 mg of thermoplastic polyurethane to a mixed solution of 8 mL of DMF and 8 mL of tetrahydrofuran, and stir at 40 °C until the thermoplastic polyurethane dissolves to obtain a thermoplastic polyurethane solution.

[0044] (2) Weigh 10 mg of covalently bonded three-dimensional carbon composite powder and dissolve it in 4 mL of DMF, and ultrasonicate for 30 min to obtain a covalently bonded three-dimensional carbon dispersion.

[0045] (3) Add the covalently bonded three-dimensional carbon dispersion to the thermoplastic polyurethane solution, stir for 1 h, and obtain a three-dimensional carbon / polyurethane assembly through solution assembly. Then, evaporate and concentrate at 160 °C on a constant temperature heating table. Use a syringe to suck up the concentrated three-dimensional carbon / polyurethane assembly solution and evenly drop it on a glass substrate, and dry at 60 °C for 30 min to obtain a high thermal conductivity polyurethane film containing covalently bonded three-dimensional carbon.

[0046] Figure 4 It is a physical picture of the high thermal conductivity polyurethane film containing covalently bonded three-dimensional carbon prepared in Example 1. Among them, (a) is the surface view of the film, and (b) is the side view of the film. As can be seen from Figure 4 it, the surface of the polyurethane film containing covalently bonded three-dimensional carbon is uniform, and it has high flexibility and can be easily bent and restored; the film is thin and light, and has a certain elasticity.

[0047] Example 2

[0048] The difference from Example 1 is that the mass ratio of small piece reduced graphene oxide to short carbon nanotubes in the covalently bonded three-dimensional carbon is 1:1; the specific steps are as follows:

[0049] 1. Preparation of small piece reduced graphene oxide dispersion:

[0050] (1) Mix 360 mL of concentrated sulfuric acid and 40 mL of concentrated phosphoric acid, pour them into a beaker containing 3 g of flake graphite powder, and then slowly add 18 g of KMnO 4 under an ice bath, stir at 50 °C for 12 h, and pour it onto ice cubes made by mixing 10 mL of 30% H 2 O 2 and 400 mL of deionized water and freezing.

[0051] (2) Let it stand to remove the upper acid solution, add deionized water to dilute it, and repeat (stand - remove the upper acid solution - add deionized water to dilute) 7 times until the pH value of the suspension is 6 - 7. Centrifuge at 4000 r / min to obtain the upper suspension, and then centrifuge at 10000 r / min to take the lower precipitate, filter and dry and redisperse it to prepare a 1 mg / mL graphene oxide dispersion.

[0052] (3) Weigh 300 mL of the above-mentioned graphene oxide dispersion, add NaOH to adjust the pH value to 9, and then add 2.4 g of NaBH 4 Stir to make it evenly dispersed, then react at 85 °C for 2 h under nitrogen protection. After washing with deionized water multiple times and suction filtration, vacuum dry at room temperature for 48 h, and then redisperse in deionized water to obtain a 1 mg / mL large flake reduced graphene oxide dispersion;

[0053] (4) Put the large flake reduced graphene oxide dispersion into a cell disruptor and ultrasonicate for 2 h, and then use a cell washer to ultrasonicate for 4 h to obtain a small flake reduced graphene oxide dispersion. The size of the small flake reduced graphene oxide is 0.1 - 0.8 μm 2 ,

[0054] 2. Preparation of functionalized short carbon nanotubes:

[0055] (1) Weigh 1.5 g of multi-walled carbon nanotubes and 300 mL of concentrated hydrochloric acid and place them in a round-bottom flask for mixing. Stir for 4 h, dilute with deionized water to neutrality, suction filter, and vacuum dry for 24 h to obtain purified multi-walled carbon nanotubes;

[0056] (2) Add 0.4 g of purified multi-walled carbon nanotubes to a conical flask containing 120 mL of concentrated sulfuric acid and 40 mL of concentrated nitric acid. Stir in a 75 °C water bath for 10 h, ultrasonicate for 4 h, wash, suction filter, and vacuum dry for 48 h. Grind and crush with a mortar to obtain short carbon nanotube powder, and redisperse to obtain a 1 mg / mL short carbon nanotube dispersion; The length of the short multi-walled carbon nanotubes is 300 - 700 nm, and the tube diameter is 5 - 30 nm.

[0057] (3) Add 0.2 mmol of p-phenylenediamine and 0.1 mmol of NaNO 2 to a conical flask, add an HCl solution with a molar amount 4 times that of p-phenylenediamine, and stir in an ice bath for 1 h to obtain a diazonium salt solution;

[0058] (4) Measure 100 mL of the short carbon nanotube dispersion and add it to the diazonium salt solution. Stir at 40 °C for 4 h, wash, suction filter, vacuum dry for 48 h, and redisperse to obtain a functionalized short carbon nanotube dispersion.

[0059] 3. Preparation of covalently bonded three-dimensional carbon composite: Mix 200 mL of the small flake reduced graphene oxide dispersion obtained in step 1 with 200 mL of the functionalized short carbon nanotube dispersion obtained in step 2, add 0.1 mmol of NaNO 2 , stir at 40 °C for 6 h, wash, suction filter, vacuum dry, and grind to obtain covalently bonded three-dimensional carbon composite powder.

[0060] 4. Preparation of polyurethane high thermal conductivity film containing covalently bonded three-dimensional carbon

[0061] (1) Add 990 mg of thermoplastic polyurethane to a mixture of 8 mL of DMF and 8 mL of tetrahydrofuran, and stir at 40 °C until the thermoplastic polyurethane dissolves to obtain a thermoplastic polyurethane solution;

[0062] (2) Weigh 10 mg of covalently bonded three-dimensional carbon composite powder and dissolve it in 4 mL of DMF, and ultrasonicate for 30 min to obtain a covalently bonded three-dimensional carbon dispersion;

[0063] (3) Add the covalently bonded three-dimensional carbon dispersion to the thermoplastic polyurethane solution, stir for 1 h, and obtain a three-dimensional carbon / polyurethane assembly through solution assembly. Then, evaporate and concentrate at 160 °C on a constant temperature heating table. Use a syringe to suck up the concentrated three-dimensional carbon / polyurethane assembly liquid and evenly drip it on a glass substrate, and dry at 60 °C for 30 min to obtain a high thermal conductivity polyurethane film containing covalently bonded three-dimensional carbon.

[0064] Example 3

[0065] The difference from Example 1 is that the mass ratio of small flake reduced graphene oxide to short carbon nanotubes in the covalently bonded three-dimensional carbon is 1:3; the specific steps are as follows:

[0066] 1. Preparation of small flake reduced graphene oxide dispersion:

[0067] (1) Mix 360 mL of concentrated sulfuric acid and 40 mL of concentrated phosphoric acid, pour them into a beaker containing 3 g of flake graphite powder, and then slowly add 18 g of KMnO 4 , under ice bath conditions, stir at 50 °C for 12 h. After cooling, pour it onto ice cubes made by mixing 10 mL of 30% H 2 O 2 and 400 mL of deionized water and freezing;

[0068] (2) Let it stand to remove the upper acid solution, add deionized water to dilute it, and repeat (stand - remove the upper acid solution - add deionized water to dilute) 7 times until the pH value of the suspension is 6 - 7. Centrifuge at 4000 r / min to obtain the upper suspension, and then centrifuge at 10000 r / min to take the lower precipitate. Filter and dry, and redisperse it to prepare a 1 mg / mL graphene oxide dispersion.

[0069] (3) Weigh 300 mL of the above graphene oxide dispersion, adjust the pH value to 9 with NaOH, then add 2.4 g of NaBH 4 and stir to disperse it evenly. Then, react at 85 °C for 2 h under nitrogen protection. After washing with deionized water multiple times and filtering, vacuum dry at room temperature for 48 h, and then redisperse it in deionized water to obtain a 1 mg / mL large flake reduced graphene oxide dispersion;

[0070] (4)Disperse a large amount of reduced graphene oxide dispersion in a cell crusher and ultrasonicate for 2 h, and then use a cell washer to ultrasonicate for 4 h to obtain a small-piece reduced graphene oxide dispersion. The size of the small-piece reduced graphene oxide is 0.1 - 0.8 μm 2 ,

[0071] 2. Preparation of functionalized short carbon nanotubes:

[0072] (1) Weigh 1.5 g of multi-walled carbon nanotubes and 300 mL of concentrated hydrochloric acid, place them in a round-bottom flask and mix. Stir for 4 h, dilute with deionized water to neutrality, filter by suction, and then dry in vacuum for 24 h to obtain purified multi-walled carbon nanotubes;

[0073] (2) Add 0.4 g of purified multi-walled carbon nanotubes to a conical flask containing 120 mL of concentrated sulfuric acid and 40 mL of concentrated nitric acid. Stir in a water bath at 75 °C for 10 h, ultrasonicate for 4 h, wash, filter by suction, and dry in vacuum for 48 h. Grind and crush with a mortar to obtain short carbon nanotube powder, and redisperse to obtain a 1 mg / mL short carbon nanotube dispersion; the length of the short multi-walled carbon nanotubes is 300 - 700 nm, and the tube diameter is 5 - 30 nm.

[0074] (3) Add 0.2 mmol of p-phenylenediamine and 0.1 mmol of NaNO 2 to a conical flask, add an HCl solution with a molar amount 4 times that of p-phenylenediamine, and stir in an ice bath for 1 h to obtain a diazonium salt solution;

[0075] (4) Measure 100 mL of the short carbon nanotube dispersion and add it to the diazonium salt solution. Stir at 40 °C for 4 h, wash, filter by suction, dry in vacuum for 48 h, and redisperse to obtain a functionalized short carbon nanotube dispersion.

[0076] 3. Preparation of covalently bonded three-dimensional carbon composite: Mix 100 mL of the small-piece reduced graphene oxide dispersion obtained in step 1 with 300 mL of the functionalized short carbon nanotube dispersion obtained in step 2, add 0.1 mmol of NaNO 2 , stir at 40 °C for 6 h, wash, filter by suction, dry in vacuum, grind, and obtain covalently bonded three-dimensional carbon composite powder.

[0077] 4. Preparation of polyurethane high thermal conductivity film containing covalently bonded three-dimensional carbon

[0078] (1) Add 990 mg of thermoplastic polyurethane to a mixed solution of 8 mL of DMF and 8 mL of tetrahydrofuran, and stir at 40 °C until the thermoplastic polyurethane dissolves to obtain a thermoplastic polyurethane solution;

[0079] (2) Weigh 10 mg of covalently bonded three-dimensional carbon composite powder and dissolve it in 4 mL of DMF, ultrasonicate for 30 min to obtain a covalently bonded three-dimensional carbon dispersion;

[0080] (3) Add the covalently bonded three-dimensional carbon dispersion into the thermoplastic polyurethane solution, stir for 1 h, and after obtaining the three-dimensional carbon / polyurethane assembly through solution assembly, evaporate and concentrate it on a constant-temperature heating table at 160 °C. Then, use a syringe to suck up the concentrated solution of the three-dimensional carbon / polyurethane assembly and evenly drip it onto a glass substrate, and dry it at 60 °C for 30 min to obtain a high thermal conductivity polyurethane film containing covalently bonded three-dimensional carbon.

[0081] Figure 1 TEM photograph of the covalently bonded three-dimensional carbon prepared in Example 1; Figure 2 TEM photograph of the covalently bonded three-dimensional carbon prepared in Example 2; Figure 3 TEM photograph of the covalently bonded three-dimensional carbon prepared in Example 3. It can be seen from Figure 1 that since the mass ratio of small flake reduced graphene oxide to short carbon nanotubes is 3:1, compared with the 1:1 mass ratio ( Figure 2 ) prepared in Example 2 and the 1:3 mass ratio ( Figure 3 ) prepared in Example 3, the short carbon nanotubes grafted on the surface of small flake reduced graphene oxide are less. In addition, it can be seen from Figures 1-3 that there are quite a number of short carbon nanotubes acting as "bridges" between two small flake reduced graphene oxides on the surface of small flake reduced graphene oxide, which is proof of the construction of an effective heat conduction network.

[0082] Example 4

[0083] Different from Example 1: The covalently bonded three-dimensional carbon accounts for 3% of the mass of the three-dimensional carbon / polyurethane assembly. The specific steps are as follows:

[0084] 1. Preparation of the small flake reduced graphene oxide dispersion:

[0085] (1) Mix 360 mL of concentrated sulfuric acid and 40 mL of concentrated phosphoric acid, pour them into a beaker containing 3 g of flake graphite powder, and then slowly add 18 g of KMnO 4 under an ice bath, stir at 50 °C for 12 h, and after cooling, pour it onto ice cubes made by mixing 10 mL of 30% H 2 O 2 and 400 mL of deionized water and freezing;

[0086] (2) Let it stand to remove the upper acid solution, add deionized water to dilute it, and repeat (stand - remove the upper acid solution - add deionized water to dilute) 7 times until the pH value of the suspension is 6 - 7. Centrifuge at a speed of 4000 r / min to obtain the upper suspension, and then centrifuge at a speed of 10000 r / min to take the lower precipitate, filter and dry it, and redisperse it to prepare a 1 mg / mL graphene oxide dispersion.

[0087] (3) Weigh 300 mL of the above graphene oxide dispersion, add NaOH to adjust the pH value to 9, and then add 2.4 g of NaBH 4 Stir to disperse it evenly, then react at 85 °C for 2 h under nitrogen protection. After washing with deionized water multiple times and suction filtration, vacuum dry at room temperature for 48 h, and then redisperse in deionized water to obtain a 1 mg / mL large flake reduced graphene oxide dispersion;

[0088] (4) Put the large flake reduced graphene oxide dispersion into a cell disruptor and ultrasonicate for 2 h, and then use a cell washer to ultrasonicate for 4 h to obtain a small flake reduced graphene oxide dispersion. The size of the small flake reduced graphene oxide is 0.1 - 0.8 μm 2 .

[0089] 2. Preparation of functionalized short carbon nanotubes:

[0090] (1) Weigh 1.5 g of multi-walled carbon nanotubes and 300 mL of concentrated hydrochloric acid and place them in a round-bottom flask for mixing. Stir for 4 h, dilute with deionized water to neutrality, filter by suction, and vacuum dry for 24 h to obtain purified multi-walled carbon nanotubes;

[0091] (2) Add 0.4 g of purified multi-walled carbon nanotubes to a conical flask containing 120 mL of concentrated sulfuric acid and 40 mL of concentrated nitric acid. Stir in a 75 °C water bath for 10 h, ultrasonicate for 4 h, wash, filter by suction, and vacuum dry for 48 h. Grind and crush with a mortar to obtain short carbon nanotube powder, and redisperse to obtain a 1 mg / mL short carbon nanotube dispersion; The length of the short multi-walled carbon nanotubes is 300 - 700 nm, and the tube diameter is 5 - 30 nm.

[0092] (3) Add 0.2 mmol of p-phenylenediamine and 0.1 mmol of NaNO 2 to a conical flask, add an HCl solution with a molar amount 4 times that of p-phenylenediamine, and stir in an ice bath for 1 h to obtain a diazonium salt solution;

[0093] (4) Measure 100 mL of the short carbon nanotube dispersion and add it to the diazonium salt solution. Stir at 40 °C for 4 h, wash, filter by suction, and vacuum dry for 48 h, then redisperse to obtain a functionalized short carbon nanotube dispersion.

[0094] 3. Preparation of covalently bonded three-dimensional carbon composite: Mix 300 mL of the small flake reduced graphene oxide dispersion obtained in step 1 with 100 mL of the functionalized short carbon nanotube dispersion obtained in step 2, add 0.1 mmol of NaNO 2 , stir at 40 °C for 6 h, wash, filter by suction, vacuum dry, and grind to obtain covalently bonded three-dimensional carbon composite powder.

[0095] 4. Preparation of polyurethane high thermal conductivity film containing covalently bonded three-dimensional carbon

[0096] (1) Add 970 mg of thermoplastic polyurethane to a mixture of 8 mL of DMF and 8 mL of tetrahydrofuran, and stir at 40 °C until the thermoplastic polyurethane dissolves to obtain a thermoplastic polyurethane solution;

[0097] (2) Weigh 30 mg of covalently bonded three-dimensional carbon composite powder and dissolve it in 4 mL of DMF, and ultrasonicate for 30 min to obtain a covalently bonded three-dimensional carbon dispersion;

[0098] (3) Add the covalently bonded three-dimensional carbon dispersion to the thermoplastic polyurethane solution, stir for 1 h, and obtain a three-dimensional carbon / polyurethane assembly through solution assembly. Then, evaporate and concentrate it at 160 °C on a constant-temperature heating table. Use a syringe to suck up the concentrated three-dimensional carbon / polyurethane assembly liquid and evenly drop it on a glass substrate, and dry it at 60 °C for 30 min to obtain a high thermal conductivity polyurethane film containing covalently bonded three-dimensional carbon.

[0099] Example 5

[0100] The difference from Example 1 is that the covalently bonded three-dimensional carbon accounts for 5% of the mass of the three-dimensional carbon / polyurethane assembly. The specific steps are as follows:

[0101] 1. Preparation of a small piece of reduced graphene oxide dispersion:

[0102] (1) Mix 360 mL of concentrated sulfuric acid and 40 mL of concentrated phosphoric acid, pour them into a beaker containing 3 g of flake graphite powder, and then slowly add 18 g of KMnO 4 under an ice bath, stir at 50 °C for 12 h, and after cooling, pour it onto ice cubes made by mixing 10 mL of 30% H 2 O 2 and 400 mL of deionized water and freezing;

[0103] (2) Let it stand to remove the upper acid solution, add deionized water to dilute it, and repeat (stand - remove the upper acid solution - add deionized water to dilute) 7 times until the pH value of the suspension is 6 - 7. Centrifuge at 4000 r / min to obtain the upper suspension, and then centrifuge at 10000 r / min to take the lower precipitate, filter and dry it, and redisperse it to prepare a 1 mg / mL graphene oxide dispersion.

[0104] (3) Weigh 300 mL of the above graphene oxide dispersion, adjust the pH value to 9 with NaOH, then add 2.4 g of NaBH 4 and stir to disperse it evenly. Then react at 85 °C for 2 h under nitrogen protection. After washing with deionized water many times and filtering, vacuum dry it at room temperature for 48 h, and then redisperse it in deionized water to obtain a 1 mg / mL large piece of reduced graphene oxide dispersion;

[0105] (4) Disperse a large amount of reduced graphene oxide dispersion in a cell crusher and ultrasonicate for 2 h, and then use a cell washer to ultrasonicate for 4 h to obtain a small piece of reduced graphene oxide dispersion. The size of the small piece of reduced graphene oxide is 0.1 - 0.8 μm 2 ,

[0106] 2. Preparation of functionalized short carbon nanotubes:

[0107] (1) Weigh 1.5 g of multi-walled carbon nanotubes and 300 mL of concentrated hydrochloric acid, place them in a round-bottom flask and mix. Stir for 4 h, dilute with deionized water to neutral, filter by suction, and vacuum dry for 24 h to obtain purified multi-walled carbon nanotubes;

[0108] (2) Add 0.4 g of purified multi-walled carbon nanotubes to a conical flask containing 120 mL of concentrated sulfuric acid and 40 mL of concentrated nitric acid. Stir in a water bath at 75 °C for 10 h, ultrasonicate for 4 h, wash, filter by suction, and vacuum dry for 48 h. Grind and crush with a mortar to obtain short carbon nanotube powder, and redisperse to obtain a 1 mg / mL short carbon nanotube dispersion; The length of the short multi-walled carbon nanotubes is 300 - 700 nm, and the tube diameter is 5 - 30 nm.

[0109] (3) Add 0.2 mmol of p-phenylenediamine and 0.1 mmol of NaNO 2 to a conical flask, add an HCl solution 4 times the molar amount of p-phenylenediamine, stir in an ice bath for 1 h to obtain a diazonium salt solution;

[0110] (4) Measure 100 mL of short carbon nanotube dispersion and add it to the diazonium salt solution. Stir at 40 °C for 4 h, wash, filter by suction, vacuum dry for 48 h, and redisperse to obtain a functionalized short carbon nanotube dispersion.

[0111] 3. Preparation of covalently bonded three-dimensional carbon composite: Mix 300 mL of the small piece of reduced graphene oxide dispersion obtained in step 1 with 100 mL of the functionalized short carbon nanotube dispersion obtained in step 2, add 0.1 mmol of NaNO 2 , stir at 40 °C for 6 h, wash, filter by suction, vacuum dry and grind to obtain covalently bonded three-dimensional carbon composite powder.

[0112] 4. Preparation of a polyurethane high thermal conductivity film containing a high content of covalently bonded three-dimensional carbon

[0113] (1) Add 950 mg of thermoplastic polyurethane to a mixture of 8 mL of DMF and 8 mL of tetrahydrofuran, stir at 40 °C until the thermoplastic polyurethane dissolves to obtain a thermoplastic polyurethane solution;

[0114] (2) Weigh 50 mg of covalently bonded three-dimensional carbon composite powder and dissolve it in 4 mL of DMF, ultrasonicate for 30 min to obtain a covalently bonded three-dimensional carbon dispersion;

[0115] (3) Add the covalently bonded three-dimensional carbon dispersion into the thermoplastic polyurethane solution, stir for 1 h, and after obtaining the three-dimensional carbon / polyurethane assembly through solution assembly, evaporate and concentrate it on a constant-temperature heating table at 160 °C. Use a syringe to suck up the concentrated solution of the three-dimensional carbon / polyurethane assembly and evenly drop it on a glass substrate, and dry it at 60 °C for 30 min to obtain a high thermal conductivity polyurethane film containing covalently bonded three-dimensional carbon.

[0116] Figure 5 Thermal conductivity of the polyurethane films containing covalently bonded three-dimensional carbon prepared in Examples 1-5. It can be seen from Figure 5 that the thermal conductivity of the polyurethane film containing covalently bonded three-dimensional carbon prepared in Example 1 is higher than that of Examples 2 and 3. On the premise that the mass ratio of small flake reduced graphene oxide to short carbon nanotubes in the covalently bonded three-dimensional carbon in Example 1 is 3:1, change the proportion of the covalently bonded three-dimensional carbon in the three-dimensional carbon / polyurethane assembly. The thermal conductivity of the polyurethane film containing covalently bonded three-dimensional carbon in Example 5 with a relatively large proportion is better than that of Examples 4 and 1.

[0117] The above embodiments are the preferred embodiments of the present invention, but the embodiments of the present invention are not limited by the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. A polyurethane high thermal conductivity film containing covalently bonded three-dimensional carbon, characterized in that, The polyurethane high thermal conductivity film containing covalently bonded three-dimensional carbon is prepared by dissolving the three-dimensional carbon composite powder in an organic solvent and ultrasonicating it, then adding a thermoplastic polyurethane solution to assemble a three-dimensional carbon / polyurethane assembly, evaporating and concentrating it, dropping it on a substrate, and preparing it by heat treatment; the three-dimensional carbon composite powder is obtained by mixing functionalized short carbon nanotubes with small pieces of reduced graphene oxide, adding NaNO 2 , stirring at 25-40 °C, washing, filtering by suction, drying in vacuum, grinding, and performing covalent grafting; the covalently bonded three-dimensional carbon is 0.5-5% of the mass of the three-dimensional carbon / polyurethane assembly; the thermoplastic polyurethane solution is obtained by adding thermoplastic polyurethane to a mixed solution of DMF and tetrahydrofuran and stirring until the thermoplastic polyurethane is dissolved at 25-40 °C; the size of the small pieces of reduced graphene oxide is 0.1-0.8 μm 2 , and the functionalized short carbon nanotubes are obtained by adding short carbon nanotubes to a diazonium salt solution and performing a diazonium salt reaction and a radical addition reaction at 25-40 °C; The diazonium salt solution is prepared by adding p-phenylenediamine and NaNO 2 to the HCl solution under an ice bath.

2. The polyurethane high thermal conductivity film containing covalently bonded three-dimensional carbon according to claim 1, characterized in that, the length of the short carbon nanotubes is 300 - 700 nm, and the tube diameter is 5 - 30 nm.

3. The polyurethane high thermal conductivity film containing covalently bonded three-dimensional carbon according to claim 1, characterized in that, The mass ratio of the short carbon nanotubes to p-phenylenediamine is 1:(1.08 - 4.32)×10 -4 ; the molar ratio of p-phenylenediamine, NaNO 2 and HCl is (1 - 2):(1 - 2):(3 - 10); the mass ratio of the short carbon nanotubes to the small piece of reduced graphene oxide is 1:(0.25 - 4).

4. The polyurethane high thermal conductivity film containing covalently bonded three-dimensional carbon according to claim 1, characterized in that, the organic solvent is one or more of DMF, tetrahydrofuran or DMAC.

5. The preparation method of the polyurethane high thermal conductivity film containing covalently bonded three-dimensional carbon according to any one of claims 1-4, characterized in that, comprises the following specific steps: S1. Add the short carbon nanotube dispersion into the diazonium salt solution, stir at 25 - 40 °C, wash, filter by suction and dry in vacuum, and redisperse to obtain a functionalized short carbon nanotube dispersion; S2. Mix the small piece of reduced graphene oxide dispersion with the functionalized short carbon nanotube dispersion, then add NaNO 2 , stir at 25 - 40 °C, wash, filter by suction, dry in vacuum and grind to obtain a covalently bonded three-dimensional carbon composite powder; dissolve the covalently bonded three-dimensional carbon composite powder in an organic solvent and sonicate to obtain a covalently bonded three-dimensional carbon dispersion; S3. Add the thermoplastic polyurethane into the mixed solution of DMF and tetrahydrofuran, stir at 25 - 40 °C until the thermoplastic polyurethane dissolves to obtain a thermoplastic polyurethane solution; S4. Add the covalently bonded three-dimensional carbon dispersion into the thermoplastic polyurethane solution and stir. After obtaining a three-dimensional carbon / polyurethane assembly dispersion by solution assembly, evaporate and concentrate at 130 - 180 °C. Drop the concentrated three-dimensional carbon / polyurethane assembly solution evenly on a glass substrate and dry at 45 - 80 °C to obtain a polyurethane high thermal conductivity film containing covalently bonded three-dimensional carbon.

6. The preparation method of the polyurethane high thermal conductivity film containing covalently bonded three-dimensional carbon according to claim 5, characterized in that, The stirring time in step S1 is 3 to 6 h, and the vacuum drying time is 24 to 48 h; in step S2, the volume ratio of the small-piece reduced graphene oxide dispersion, the functionalized short carbon nanotube dispersion, and NaNO 2 is (100 to 300) mL : (100 to 300) mL : (0.1 to 0.2) mmol, the stirring time is 4 to 8 h, and the ultrasonic time is 20 to 50 min; in step S3, the mass-volume ratio of the thermoplastic polyurethane to the mixed solution is (0.9 to 1.5) g : (16 to 32) mL, and the volume ratio of DMF to tetrahydrofuran in the mixed solution is 1:1; in step S4, the volume ratio of the covalently bonded three-dimensional carbon dispersion to the thermoplastic polyurethane solution is (1 to 3) : (4 to 16); the stirring time is 1 to 2 h.

7. The application of the polyurethane high thermal conductivity film containing covalently bonded three-dimensional carbon according to any one of claims 1-4 in the field of photothermal controllable thin films.

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