A carbon nanotube film, a conductive prepreg, and a method for manufacturing the same

Abstract

The application discloses a kind of carbon nanotube film, conductive prepreg and its preparation method.The steps include step one, the preparation of carbon nanotube film;Step two, roll composite: carbon nanotube film is rolled with the film of required glue through composite machine and is formed into conductive adhesive film after roll composite, and conductive adhesive film is combined with fiber to form conductive prepreg;Or carbon nanotube film is rolled with the prepreg of required through composite machine and is formed into conductive prepreg;Step three, cutting and curing obtain the required specification of conductive prepreg;By the carbon nanotube film, conductive prepreg and its preparation method described in the application, the cost of carbon nanotube film can be effectively reduced, the preparation efficiency of carbon nanotube film is improved, the storage and transportation mode of carbon nanotube film is optimized, so that carbon nanotube film can be conveniently cut and spliced, and the resistance controllability of conductive prepreg is improved, so that it can realize the patterned resistance distribution setting.

Description

Technical Field

[0001] The present invention belongs to the technical field of composite materials, and in particular relates to a carbon nanotube film, a conductive prepreg and a preparation method thereof. Background Art

[0002] Carbon nanomaterials represented by carbon nanotubes have low density, high conductivity and strength and have attracted widespread attention and application, especially in the field of conductive materials. Carbon nanotubes have been used in many fields such as antistatic, conductive adhesive, electromagnetic shielding, electromagnetic wave absorber, and sensing.

[0003] Carbon nanotube membranes are one of the structural forms of carbon nanotube applications. There are two main types of carbon nanotube membranes: (1) Buckypaper-based carbon nanotube membranes, which are typically made by vacuum filtration of carbon nanotubes dispersed in water or a solvent through a microporous membrane. These membranes have a thickness ranging from tens to over 100 micrometers. (2) Carbon nanotube membranes grown and pulled using the CVD method. These membranes have higher electrical conductivity, a thickness ranging from several micrometers to tens of micrometers, a surface resistance generally below 5Ω, and high strength.

[0004] The above-mentioned carbon nanotube membranes, represented by buckypaper, are difficult to prepare for large-scale carbon nanotube membranes. They also produce a large amount of wastewater or waste liquid and are expensive. Since their preparation, they have generally been used for small-scale scientific research. The above-mentioned method of growing carbon nanotube membranes by CVD has been applied in mass production, but its cost is still high, with a market price of 1,000 yuan / m 2 (300 yuan / gram) or more, and its resistance control range is small, and the design space is small.

[0005] Even when carbon nanotubes are coated and dried to form a film, the safe and environmentally friendly water-dispersed carbon nanotube system has high surface energy and low viscosity, making it difficult to adhere to low-polarity surfaces where adhesion is weak and easy to peel. Consequently, it can only be coated on higher-polarity surfaces and directly integrated into a finished product, and cannot be sold, transported, or used as a standalone carbon nanotube film. Increasing the viscosity to a coatable state often requires the use of a large amount of thickener. The resulting carbon nanotube film has poor conductivity and lacks permeability, requiring washing and other methods to remove excess non-carbon nanotube substances.

[0006] Conductive adhesive films and conductive prepregs are two important applications of conductive materials. Existing conductive adhesive films are typically made by directly mixing conductive fillers into a resin and then scraping the film. However, directly mixing conductive fillers into the resin creates a large number of interfaces. This type of carbon nanotube-modified conductive adhesive film has low conductivity, typically less than 0.1S / cm, and poor resistance adjustability and controllability. The resulting conductive prepregs suffer from the same problems. Furthermore, this method cannot produce a patterned, variable resistance distribution.

[0007] Conductive adhesive films can also be prepared by combining carbon nanotube films with adhesive films. For example, buckypaper and CVD carbon nanotube films can be applied to prepreg surfaces. However, these interfaces are poor, and resistance tunability and controllability are limited, making it impossible to achieve patterned resistance distribution structures. Therefore, research on how to improve the resistance controllability of conductive prepregs prepared with carbon nanotube films and achieve patterned resistance distribution on conductive prepregs is of great significance.

[0008] The existing patent application CN202311701744.1 discloses a continuous nanoporous membrane filtration production method, which is applicable to porous membranes, but the cost of microporous membranes is very high, and the entire device process is complicated. The method of growing carbon nanotube membranes by the CVD method has very high requirements for equipment, and the cost is still relatively high. The resistance stability control range is generally between 1-7Ω / sq., and the design space is relatively small. The method of preparing carbon nanotube membranes by coating, such as CN201910967180.3, is to apply the carbon nanotube dispersion to the surface of the roller, and then dry it to obtain the carbon nanotube film and transfer it to the surface of other substrates. This method is only applicable to substrates infiltrated with the carbon nanotube dispersion and cannot be used for easily peelable substrates with very low surface energy. Summary of the Invention

[0009] The object of the present invention is to provide a carbon nanotube film, a conductive prepreg and a preparation method thereof, which solves the problems existing in the prior art of high preparation cost, low production efficiency, difficulty in storage and transportation, and inability to cut and splice the carbon nanotube film, resulting in poor resistance controllability of the conductive prepreg prepared using the carbon nanotube film and inability to achieve patterned resistance distribution. In this way, the cost of the carbon nanotube film can be effectively reduced, the preparation efficiency of the carbon nanotube film can be improved, the storage and transportation methods of the carbon nanotube film can be optimized, the carbon nanotube film can be easily cut and spliced, and the resistance controllability of the conductive prepreg can be improved, so that it can achieve patterned resistance distribution setting.

[0010] The objectives of the present invention are achieved through the following technical solutions.

[0011] A carbon nanotube film, a conductive prepreg and a preparation method thereof, the method comprising the following steps:

[0012] Step 1: Preparation of carbon nanotube film: dispersing carbon nanotubes in water to form a uniform and stable dispersion; spraying the dispersion onto the surface of release paper, and after drying, forming a carbon nanotube film adhered to the surface of the release paper;

[0013] Step 2: Rolling and laminating: Rolling and laminating the carbon nanotube film and the desired adhesive film through a laminating machine to form a conductive adhesive film, and then laminating the conductive adhesive film with fibers to form a conductive prepreg; or rolling and laminating the carbon nanotube film and the desired prepreg through a laminating machine to form a conductive prepreg;

[0014] Step 3: Cut and cure to obtain the conductive prepreg of required specifications.

[0015] Furthermore, in step 1, the thickness of the carbon nanotube film is 0.5 μm-80 μm.

[0016] Furthermore, the surface resistance of the carbon nanotube film is 10-10000Ω.

[0017] Furthermore, in step 2, at least one layer of carbon nanotube film is provided.

[0018] Furthermore, step one includes:

[0019] Step S11: dispersing the carbon nanotubes into water under the action of a dispersant to form a uniform and stable dispersion;

[0020] Step S12: by controlling the aperture of the nozzle to be the first aperture d1, the dispersion is first sprayed onto the release paper and then dried to form a continuous carbon nanotube microfilm;

[0021] Step S13: by controlling the aperture of the nozzle to be the second aperture d2, the dispersion is first sprayed onto the release paper and then dried to form a continuous carbon nanotube film adhered to the surface of the release paper.

[0022] Furthermore, the concentration of carbon nanotubes in the dispersion is 0.5 wt% to 3.5 wt%.

[0023] Furthermore, the spraying and drying processes are performed at least once.

[0024] Furthermore, d1<d2.

[0025] Furthermore, the dispersion liquid also includes a polymer binder, and the total mass of the dispersant and the polymer binder does not exceed twice that of the carbon nanotubes.

[0026] A carbon nanotube film, the preparation method of which is included in the preparation method of a conductive prepreg containing the carbon nanotube film, the carbon nanotube film comprising carbon nanotubes and a dispersant; the amount of the dispersant is 5%-40% of the mass of the carbon nanotubes; the carbon nanotube film is compounded with an adhesive film to obtain a conductive adhesive film.

[0027] A conductive prepreg is prepared by the method for preparing a conductive prepreg containing a carbon nanotube film, and the conductive prepreg comprises a conductive adhesive film.

[0028] The beneficial effects of the present invention are as follows: through the carbon nanotube film, conductive prepreg and preparation method thereof, the cost of the carbon nanotube film can be effectively reduced, the preparation efficiency of the carbon nanotube film can be improved, the storage and transportation methods of the carbon nanotube film can be optimized, the carbon nanotube film can be easily cut and spliced, and the resistance controllability of the conductive prepreg can be improved, so that it can realize patterned resistance distribution setting. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The accompanying drawings, which constitute part of the present invention, are provided to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings:

[0030] Figure 1 This is a schematic diagram of the process flow chart for preparing carbon nanotube films;

[0031] Figure 2 Schematic diagram of preparing conductive adhesive film or conductive prepreg by roller pressing of a composite machine;

[0032] Figure 3 Schematic diagram of the conductive prepreg structure with patterned resistor distribution.

[0033] Reference numerals: 1, carbon nanotube film; 2, release paper; 3, upper roller; 4, lower roller. DETAILED DESCRIPTION

[0034] In order to make the objectives, technical solutions and advantages of the present invention more clear, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0035] A carbon nanotube film, a conductive prepreg and a preparation method thereof. The preparation method of the conductive prepreg containing the carbon nanotube film comprises the following steps:

[0036] Step 1: Preparation of carbon nanotube film 1: Dispersing carbon nanotubes in water to form a uniform and stable dispersion; spraying the dispersion onto the surface of release paper 2, and after drying, forming a carbon nanotube film 1 adhered to the surface of release paper 2;

[0037] Step 2: Rolling and compounding: Rolling and compounding the carbon nanotube film 1 and the desired adhesive film through a compounding machine to form a conductive adhesive film, and then compounding the conductive adhesive film with fibers to form a conductive prepreg; or rolling and compounding the carbon nanotube film 1 and the desired prepreg through a compounding machine to form a conductive prepreg;

[0038] Step 3: Cut and cure to obtain the conductive prepreg of required specifications.

[0039] Through the method, the cost of the carbon nanotube film 1 can be effectively reduced, the preparation efficiency of the carbon nanotube film 1 can be improved, the storage and transportation methods of the carbon nanotube film 1 can be optimized, the carbon nanotube film 1 can be easily cut and spliced, and the resistance controllability of the conductive prepreg can be improved, so that it can achieve patterned resistance distribution setting.

[0040] In step 1, a carbon nanotube film 1 is formed by depositing carbon nanotubes and a dispersant. The carbon nanotube film 1 is adhered to a release paper 2. The carbon nanotube film thickness ranges from 0.5 μm to 80 μm, the surface resistivity of the carbon nanotube film 1 ranges from 10 to 10,000 Ω, and the mass of the dispersant in the carbon nanotube film 1 is 5% to 40% of the carbon nanotube mass. In step 2, at least one layer of the carbon nanotube film 1 is formed. During the laminating process, the upper roller 3 of the laminating machine can be a patterned hot press roller, and the lower roller 4 can be a round roller. The specific types of upper roller 3 and lower roller 4 are selected as needed. The distribution of the carbon nanotube film 1 on the conductive adhesive film exhibits a desired pattern. Specifically, the carbon nanotube film can be cut into the desired pattern and then rolled onto the adhesive film under the action of a hot press roller with the corresponding pattern to form a conductive adhesive film having the desired pattern. The conductive adhesive film is provided with a carbon nanotube film 1 having at least one electrical resistance.

[0041] Step one includes:

[0042] Step S11: dispersing the carbon nanotubes in water under the action of a dispersant to form a uniform and stable dispersion; wherein the amount of the dispersant is 5%-40% of the mass of the carbon nanotubes; and the concentration of the carbon nanotubes in the dispersion is 0.5wt%-3.5wt%.

[0043] Step S12: by controlling the aperture of the nozzle to be the first aperture d1, the dispersion is first sprayed onto the release paper 2 and then dried to form a continuous carbon nanotube microfilm; the spraying and drying processes are both set at least once;

[0044] Step S13: by controlling the aperture of the nozzle to be the second aperture d2, the dispersion is first sprayed onto the release paper 2 and then dried to form a continuous carbon nanotube film 1 adhered to the surface of the release paper 2;

[0045] Wherein, d1<d2, and the specific values ​​of d1 and d2 are set as needed. The number of times the dispersion is sprayed is recorded as n, and the initial preset number of sprays is m, where n and m are both positive integers; m<n. Preferably, when n is greater than 4, during the n-times of spraying the dispersion, before the carbon nanotubes cover the release paper, the median size of the droplets sprayed for the initial preset number of sprays, m, is between 3μm and 60μm, and m is 1-4. When the median diameter is controlled to be higher than 3μm, the droplets are not completely dry before reaching the surface of the release paper 2, and can be well adsorbed on the surface of the release paper 2; when the diameter is controlled to be lower than 60μm, the microfilm thickness formed by the carbon nanotubes before covering most of the surface of the release paper 2 is relatively small, which has little effect on the final film thickness. In addition, due to their small diameter, the microfilm formed by the small droplets after being sprayed onto the surface of the release paper 2 has a high density, which is more conducive to the uniform spreading of the droplets on the surface of the release paper during subsequent spraying; therefore, the resulting carbon nanotube film 1 has a high uniformity. The types of dispersants include any one or more of sodium dodecylbenzenesulfonate, sodium stearate, polyvinyl pyrrolidone, and Triton X-100.

[0046] Different from the background technology, the existing methods include carbon nanotube membranes represented by buckypaper, which are generally obtained by nanoporous membrane filtration method. However, it is obviously difficult to prepare large-area carbon nanotube membranes, and the price of nanoporous membranes is very high. The filtration method has high energy consumption and cannot be produced continuously, resulting in high prices. Generally, only areas ≤ 0.1m 2 The present invention adopts a method of multiple spraying to first form a micro-droplet film on the surface of the release paper 2, so that the surface of the non-wetting release paper 2 becomes a wetted surface, and then spraying can form a continuous carbon nanotube film 1. The carbon nanotube film 1 is successfully prepared on the release paper 2 with low surface polarity (see Example 1 for details). The principle is to adopt a method of multiple spraying. Under the initial preset number of spraying times m, the micro-droplets formed by spraying are first dried on the release paper 2 to form a carbon nanotube micro-film with high surface polarity. After the micro-film covers the preset surface area of ​​the release paper 2, the surface of the release paper 2 becomes hydrophilic, and subsequent micro-droplets of different diameters can be well spread and dried on the surface of the release paper 2, and finally form a continuous and uniform carbon nanotube film 1. Among them, the preset surface area is the area occupying most of the surface of the release paper 2, which is specifically set according to the requirements. Compared with the existing methods, the present application has the following advantages:

[0047] (1) Low cost: This application uses a carbon nanotube aqueous dispersion spraying method to prepare a carbon nanotube film 1 attached to a release paper 2. Currently, carbon nanotube production has been scaled up, and the price of carbon nanotubes has dropped to less than 0.2 yuan / g. This preparation method can continuously prepare a roll of carbon nanotube film 1. When multiple nozzles are used, the preparation efficiency is as high as 1000-4000m 2 / h, the equipment requirements are simple, thus significantly reducing costs. Its cost is as low as 1-20 yuan / m 2 , which is much lower than the 1000 yuan / m of CVD carbon nanotube film. 2 .

[0048] (2) High productivity: This preparation method can continuously prepare rolled carbon nanotube films 1 with a production efficiency of up to 1000-4000 m 2 / h, the equipment can use conventional spraying equipment.

[0049] (3) Easy to store and transport: The carbon nanotubes attached to the release paper 2 can be stored and transported in rolls at a low cost.

[0050] (4) Ease of use: The carbon nanotube film 1 can be readily used. It can be combined with at least one carbon nanotube film 1 of varying resistance and a film or prepreg to produce a multi-resistance film or prepreg. Because it is distributed on the release paper 2, it can be cut into any shape. It can then be applied to the film or prepreg to form films or prepregs with various conductive patterns on their surfaces. Furthermore, it can be combined with the raised pattern on the hot pressing roller to imprint carbon nanotubes with the same pattern onto the film or prepreg, forming patterned films or prepregs. This is something that existing carbon nanotube films such as buckypaper and carbon nanotube film 1 cannot achieve.

[0051] (5) Good material properties such as composite material process matching. This carbon nanotube film 1 matches the requirements of the composite material molding process and meets the requirements of resin permeability. The resulting composite material has good interlaminar shear strength. After adding a small amount of soluble thermoplastic resin, the interlaminar shear strength of the composite material can be further improved. Especially after adding thermoplastic particles, the carbon nanotube film 1 has good permeability, good resin penetration, few interlaminar defects of the composite material, and high interlaminar shear strength.

[0052] Furthermore, to match the molding process of the adhesive film and composite material, the carbon nanotube film 1 requires good permeability. However, a high dispersant dosage significantly reduces the permeability of the resin within the carbon nanotube film 1, thereby degrading the interlaminar properties of the composite material after the carbon nanotube film 1 is distributed between the layers. As shown in Table 1, while maintaining acceptable dispersibility, the composite material's performance is prioritized. Therefore, the preferred dispersant dosage is 5-40% of the total carbon nanotube dosage.

[0053] Table 1 Effect of dispersant dosage on interlaminar shear strength of T800 / 5228 composite materials

[0054]

[0055] The dispersion can also preferably include a polymer binder to enhance the interlaminar shear strength of the composite material. The amount of binder used is adjusted as needed. As shown in Table 2, considering the balance between permeability and strength, the combined mass of the dispersant and polymer binder is preferably no more than twice that of the carbon nanotubes. The polymer binder is a thermosetting or thermoplastic resin with a glass transition temperature greater than 150°C.

[0056] Table 2 Effect of soluble polymer binder dosage on interlaminar shear strength of T800 / 5228 composite materials

[0057]

[0058] The dispersion also includes a granular toughening agent; the amount of toughening agent used is set as needed. Preferably, the total amount of toughening agent does not exceed 10 times the mass of the carbon nanotubes. This prevents excessive amounts of toughening agent from causing a decrease in the conductivity of the carbon nanotube film 1. Preferably, the granular toughening agent is a thermoplastic resin particle; it is used to significantly increase the resin permeability of the carbon nanotube film 1 while improving the interlaminar shear strength of the composite material, as shown in Table 3.

[0059] Table 3 Effect of the amount of insoluble thermoplastic resin particles on the interlaminar shear strength of T800 / 5228 composite materials

[0060]

[0061] The carbon nanotube film 1 also includes a flaky conductive nanomaterial; the flaky conductive nanomaterial includes one or more of graphene and graphite nanosheets, which can slightly improve the conductivity of the carbon nanotube film 1. The amount of flaky conductive nanomaterial should not exceed 20% of the carbon nanotube content in the carbon nanotube film. This prevents the problem of significantly degrading the interlayer performance of the prepared carbon nanotube film 1 due to reduced resin permeability and a poor graphene-resin interface. Details are shown in Table 4.

[0062] Table 4 Effect of graphene dosage on interlaminar shear strength of T800 / 5228 composite materials

[0063]

[0064] A carbon nanotube film, the preparation method of which is included in the preparation method of a conductive prepreg containing the carbon nanotube film, the carbon nanotube film comprising carbon nanotubes and a dispersant; the carbon nanotube film is compounded with an adhesive film to obtain a conductive adhesive film.

[0065] A conductive prepreg is prepared by the method for preparing a conductive prepreg containing a carbon nanotube film, and the conductive prepreg comprises a conductive adhesive film.

[0066] Example 1:

[0067] The implementation process of the technical solution of this embodiment is as follows:

[0068] (1-1) 150 g of carbon nanotubes (8-10 nm in diameter, 25 μm in length) were added to 9900 g of deionized water, and 15 g of sodium dodecylbenzenesulfonate was added as a dispersant. The mixture was ultrasonically dispersed for 0.5 h, for a total of 5 times. After the dispersion was complete, the undispersed carbon nanotubes were removed by centrifugation to obtain a 1.2% carbon nanotube aqueous dispersion.

[0069] (1-2) The sprayer uses five rows of nozzles. The dispersion is injected into a liquid storage tank as the spray liquid. The nozzles and air pressure are adjusted to control the median diameter of the droplets sprayed by the first two rows of nozzles to be between 10 μm and the median diameter of the droplets sprayed by the last three rows of nozzles to be between 50 μm, 50 μm, and 80 μm, respectively. After inserting the release paper 2 into the unwinding and rewinding device of the reciprocating sprayer, the machine is turned on, and the release paper 2 is advanced at a speed of 0.5 m / s. The hot air drying device between the nozzles is controlled at 150°C. The carbon nanotube film 1 attached to the surface of the release paper 2 is rewound. The film has a thickness of 7.1 μm and a surface resistance of 280 Ω and is designated as C280 carbon nanotube film 1.

[0070] (1-3) The epoxy resin 5228A film and the carbon nanotube film 1 were rolled and compounded by a compounding machine to obtain a conductive epoxy resin 5228A film JM5228A-C280;

[0071] (1-4) The epoxy resin carbon fiber prepreg T800 / 5228A and the carbon nanotube film 1 are rolled and compounded by a compounding machine, using single-sided compounding to obtain a conductive epoxy resin carbon fiber prepreg T800 / 5228A-C280;

[0072] (1-5) Compounding the conductive epoxy resin film JM5228A-280 obtained in (1-3) above with continuous carbon fibers to form a conductive epoxy resin carbon fiber prepreg T800 / 5228A-C280-2;

[0073] (1-6) The conductive epoxy resin carbon fiber prepreg T800 / 5228A-C280 obtained above was cut into a size of 300 mm х 300 mm, including 8 sheets at 0° and 8 sheets at 45°, and laid in a quasi-isotropic manner. After curing using the epoxy resin curing process, a conductive modified composite material was obtained.

[0074] The conductive modified composite material has a high thickness conductivity of 0.27S / cm and a 0° interlaminar shear strength of 93MPa.

[0075] Example 2:

[0076] The implementation process of the technical solution of this embodiment is as follows:

[0077] (2-1) 220 g of carbon nanotubes (3-5 nm in diameter, 15 μm in length) were added to 9900 g of deionized water, along with 25 g of graphene. 75 g of sodium stearate was then added as a dispersant, and the mixture was dispersed by high-speed shearing for 6 h. After the dispersion was complete, the undispersed carbon nanotubes were removed by centrifugation to obtain an aqueous dispersion having a carbon nanotube concentration of 1.9% and a graphene concentration of 0.15% (total conductive agent concentration of 2.05%).

[0078] (2-2) The spraying machine uses 3 rows of nozzles, injects the dispersion as the spraying liquid into the liquid storage tank, adjusts the nozzle and air pressure, and inserts the release paper 2 into the unwinding-rewinding device of the reciprocating sprayer. Then, the machine is turned on and the reciprocating spraying mode is adopted. The median diameters of the droplets sprayed by the three nozzles in the first 3 times are controlled to be 5μm, 20μm, and 40μm respectively. After 2 reciprocating times, the surface of the release paper 2 is completely covered with black. Then the median diameter of the droplets sprayed by the nozzle is adjusted to 70μm, and 3 more reciprocating times are performed. During the spraying, the temperature of the hot air drying device between the nozzles is controlled at 150°C. After the reciprocating is completed, the release paper 2 with the carbon nanotube film 1 is moved forward and rewound, and replaced with a blank release paper 2 to continue spraying. The carbon nanotube film 1 attached to the surface of the release paper 2 is rewound, with a thickness of 27μm and a surface resistance of 78Ω, and is named CG78 carbon nanotube film 1;

[0079] (2-3) The epoxy resin BA9916 film and the carbon nanotube film 1 were rolled and laminated by a laminating machine to obtain a conductive epoxy resin film JM9916-C78;

[0080] (2-4) The T700 / BA9916 epoxy resin carbon fiber prepreg and the carbon nanotube film 1 were rolled and compounded by a compounding machine, using single-sided compounding to obtain a conductive epoxy resin carbon fiber prepreg T700 / BA9916-C78;

[0081] (2-5) Compounding the conductive epoxy resin film JM9916-C78 obtained in (2-3) above with continuous carbon fibers to form a conductive epoxy resin carbon fiber prepreg T700 / BA9916-C78-2;

[0082] (2-6) The conductive epoxy resin carbon fiber prepreg T700 / BA9916-C78 obtained above was cut into a size of 300mmх300mm, including 8 sheets at 0° and 8 sheets at 45°, and laid out in a quasi-isotropic manner. After curing using the epoxy resin curing process, a conductive modified composite material was obtained.

[0083] The conductive modified composite material has a high thickness conductivity of 0.48S / cm and a 0° interlaminar shear strength of 82MPa.

[0084] Example 3:

[0085] The implementation process of the technical solution of this embodiment is as follows:

[0086] (3-1) 250 g of carbon nanotubes (8-10 nm in diameter, 25 μm in length) were added to 10 kg of deionized water, and 60 g of sodium dodecylbenzenesulfonate was added as a dispersant. The mixture was ultrasonically dispersed for 0.5 h, for a total of 5 times, and then ball-milled for 1 h. After the milling, the undispersed carbon nanotubes were removed by centrifugation to obtain a 2.2% aqueous dispersion of carbon nanotubes.

[0087] (3-2) The sprayer uses five rows of nozzles. The dispersion is injected into a liquid storage tank as the spray liquid. The nozzles and air pressure are adjusted to control the median diameters of the droplets sprayed by the first three rows of nozzles to be 10 μm, 20 μm, and 40 μm, respectively, and the median diameters of the droplets sprayed by the last two rows of nozzles to be 70 μm and 100 μm, respectively. After the release paper 2 is inserted into the unwinding and rewinding device of the reciprocating sprayer, the machine is turned on, and the release paper 2 is advanced at a speed of 0.8 m / s. The hot air drying device between the nozzles is controlled at 150°C. The carbon nanotube film 1 attached to the surface of the release paper 2 is rewound. The film has a thickness of 15 μm and a surface resistance of 210 Ω and is designated as C210 carbon nanotube film 1.

[0088] (3-3) The bismaleimide resin film QY9611 and the carbon nanotube film 1 were rolled and laminated by a laminating machine to obtain a conductive epoxy resin film JM9611-C210;

[0089] (3-4) CCF800 / QY9611 bismaleimide resin carbon fiber prepreg and carbon nanotube film 1 were rolled and compounded by a compounding machine, using single-sided compounding to obtain conductive bismaleimide resin carbon fiber prepreg CCF800 / QY9611-C210;

[0090] (3-5) Compounding the conductive bismaleimide resin film JM210 obtained in (3-3) above with continuous carbon fiber to form a conductive bismaleimide resin carbon fiber prepreg CCF800 / QY9611-C210-2;

[0091] (3-6) The conductive bismaleimide resin carbon fiber prepreg YJ210 obtained above was cut into a size of 300mmх300mm, including 8 sheets at 0° and 8 sheets at 45°, and laid in a quasi-isotropic manner. After curing using the bismaleimide resin curing process, a conductive modified composite material CCF800 / QY9611-C210 was obtained.

[0092] Water-soluble carboxyl modified PEK-C was added to the carbon nanotube aqueous dispersion in (3-7) and (3-1) in an amount of 100 g, and then used for spraying. The other steps were the same as (3-2) to (3-6). The obtained carbon nanotube film 1 had a resistance of 810Ω (CT810) and a film thickness of 21 μm, and a conductive modified composite material CCF800 / QY9611-CT810 was obtained.

[0093] (3-8) Non-water-soluble PEK-C micron particles with a particle size of 10-20 μm and an addition amount of 340 g were added to the carbon nanotube aqueous dispersion in (3-1), and then used for spraying. The other steps were the same as (3-2)-(3-6). The obtained carbon nanotube film 1 had a resistance of 770Ω (CT770) and a film thickness of 39 μm, obtaining a conductive modified composite material CCF800 / QY9611-CT770.

[0094] CCF800 / QY9611-C210 has a high through-thickness conductivity of 0.35 S / cm and a 0° interlaminar shear strength of 76 MPa. CCF800 / QY9611-CT810 has a through-thickness conductivity of 0.29 S / cm and a 0° interlaminar shear strength of 95 MPa. CCF800 / QY9611-CT770 has a through-thickness conductivity of 0.34 S / cm and a 0° interlaminar shear strength of 98 MPa.

[0095] Example 4:

[0096] The implementation process of the technical solution of this embodiment is as follows:

[0097] (4-1) 93 g of carbon nanotubes (7-10 nm in diameter, 50 μm in length) were added to 9900 g of deionized water, and 12 g of polyvinyl pyrrolidone was added as a dispersant. The mixture was dispersed by sand milling for 2 h. After the dispersion was completed, the undispersed carbon nanotubes were removed by centrifugation to obtain a 0.87% aqueous dispersion of carbon nanotubes.

[0098] (4-2) The sprayer uses three rows of nozzles. The dispersion is injected into a liquid storage tank as the spray liquid. The nozzle and air pressure are adjusted to control the median diameters of the droplets sprayed by the first two rows of nozzles to be 5 μm and 15 μm, respectively, and the median diameter of the droplets sprayed by the last row of nozzles to be 80 μm. After inserting the release paper 2 into the unwinding and rewinding device of the reciprocating sprayer, the machine is turned on, and the release paper 2 is advanced at a speed of 0.8 m / s. The hot air drying device between the nozzles is controlled at 150°C. The carbon nanotube film 1 attached to the surface of the release paper 2 is rewound, with a thickness of 1.8 μm and a surface resistance of 3600 Ω (C3600).

[0099] (4-3) The BA9916 epoxy resin film and the carbon nanotube film 1 were rolled and laminated by a laminating machine to obtain a single-resistance conductive epoxy resin film JM9916-C3600;

[0100] (4-4) The carbon nanotube films 1CG78, C280, CT810, and C3600 obtained in Examples 1-4 were cut into short rolls with a width of 100 mm and then laminated with a 400 mm wide bismaleimide film in order of increasing resistance from left to right. This yielded four bismaleimide films (JM70-280-810-3600) with a continuous distribution of resistance and conductivity. These films were then intercalated between the middle layers of a composite component. The composite component was obtained by orthogonally laying eight layers of QW280 / QY9611 prepreg. During the prepreg laying process, the JM70-280-810-3600 film was placed in the middle layer. The composite component was then cured using the same curing process as the QW280 / QY9611. This composite component exhibited excellent surface wave absorption.

[0101] Example 5:

[0102] The implementation process of the technical solution of this embodiment is as follows:

[0103] (5-1) 180 g of carbon nanotubes (3-5 nm in diameter, 35 μm in length) were added to 9900 g of deionized water, and 15 g of Triton X-100 was added as a dispersant. The mixture was ball milled for 3 h. After grinding, the undispersed carbon nanotubes were removed by centrifugation to obtain a 1.55% aqueous dispersion of carbon nanotubes.

[0104] (5-2) The sprayer uses five rows of nozzles. The dispersion is injected into a liquid storage tank as the spray liquid. The nozzles and air pressure are adjusted to control the median diameters of the droplets sprayed by the first two rows of nozzles to be 10 μm and 20 μm, and the median diameters of the droplets sprayed by the last three rows of nozzles to be 40 μm, 60 μm, and 100 μm. After inserting the release paper 2 into the unwinding and rewinding mechanism of the reciprocating sprayer, the machine is turned on, and the release paper 2 is advanced at a speed of 0.2 m / s. The hot air drying device between the nozzles is controlled at 150°C. The carbon nanotube film 1 attached to the surface of the release paper 2 is rewound, resulting in a thickness of 12.5 μm and a surface resistance of 135 Ω (C135).

[0105] (5-3) The epoxy resin 5228A film and the carbon nanotube film 1 were rolled and laminated using a laminating machine. A cross pattern was arranged on the surface of one roller. The length and height of a single cross were 80 mm, the length of the end side of the cross was 10 mm, and the horizontal and vertical spacing of the cross was 50 mm. A conductive epoxy resin film JM5228-135TA with a cross carbon nanotube film 1 conductive pattern with a resistance of 135 Ω was obtained.

[0106] (5-4) Quartz fiber, conductive epoxy resin film JM5228-135TA, and conventional epoxy resin film are rolled and laminated by a laminating machine to obtain a conductive epoxy resin quartz fiber prepreg QW280 / 5228A-135TA with a patterned carbon nanotube film 1 on one side;

[0107] (5-5) The patterned conductive epoxy resin quartz fiber prepreg QW280 / 5228A-135TA obtained above was cut into a size of 600mmх600mm, of which 16 sheets were orthogonally laid in layers and cured using the epoxy resin curing process to obtain a conductive patterned modified quartz fiber reinforced epoxy resin-based composite material.

[0108] The conductive modified composite material has a 0° interlaminar shear strength of 93 MPa and has good low-frequency wave absorbing performance.

[0109] Table 5 Technical parameters and material properties in each embodiment

[0110]

[0111] As shown in Table 5, Examples 1-5 demonstrate that the conductive prepregs prepared using the preparation method of the present invention exhibit a wide range of controllable film thickness and adjustable resistance. Furthermore, a carbon nanotube film 1 with a toughening function can be prepared, which is particularly suitable for the preparation of conductive adhesive films, prepregs, and composite materials.

[0112] Comparative Example 1:

[0113] The implementation process of this comparative technical solution is as follows:

[0114] (DB1) 180 g of carbon nanotubes (3-5 nm in diameter, 35 μm in length) were added to 9900 g of deionized water, and 15 g of Triton X-100 was added as a dispersant. The mixture was ball milled for 3 h. After grinding, the undispersed carbon nanotubes were removed by centrifugation to obtain a 1.55% aqueous dispersion of carbon nanotubes.

[0115] (2) After the release paper 2 is inserted into the unwinding-rewinding device of the wet-process dipping machine, the carbon nanotube aqueous dispersion is poured into the dipping machine, and the release paper with the carbon nanotube film on the surface is prepared by the dip coating method. The release paper 2 moves at a speed of 0.2 m / s. At the same time, a hot air drying device is added between the liquid outlet of the release paper 2 and the rewinding device. The temperature of the hot air drying device is controlled at 150°C.

[0116] In this comparative example, since the carbon nanotube aqueous dispersion does not wet the release paper surface, the liquid is almost completely debonded after the release paper 2 is pulled out of the liquid surface, and a small amount of liquid beads remain on the paper surface. Therefore, a release paper with a carbon nanotube film on the surface cannot be prepared.

[0117] By comparing Examples 1-5 with Comparative Example 1, it can be seen that the preparation method in this application can be used for easily peelable substrates with very low surface energy, such as release paper 2; and can make the process of preparing the carbon nanotube film 1 simpler and reduce the cost of preparing the carbon nanotube film 1.

[0118] In addition, through the setting of the above-mentioned preparation method, the desired large-area, high-permeability carbon nanotube film can be prepared simply, quickly, and at low cost. This carbon nanotube film has the characteristics of a large controllable resistance range, high accuracy, and small discreteness. Through the preparation method, a large range of film thickness can be prepared on the basis of small equipment investment, and production efficiency is high. In addition, the prepared carbon nanotube film 1 is easy to roll, store, transport, and reuse in various occasions. It can also be used to prepare various conductive films and prepregs, and has good process compatibility with the film and composite materials. The interlayer performance of the composite material is good, and the pattern of resistance distribution is controllable, which has high process applicability. In addition, the prepared carbon nanotube film 1 can be cut and spliced, which is conducive to the preparation of conductive films and prepregs with various resistance distributions; the modification space is large and can match various applications. Through the preparation method, it is conducive to direct use in the preparation of conductive films or prepregs, and is conducive to expanding the controllable range of conductivity. It can also achieve pattern distribution of carbon nanotube film 1 on conductive prepregs, so as to facilitate the preparation of conductive films and prepregs with conductive patterns.

[0119] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for preparing a conductive prepreg containing a carbon nanotube film, characterized in that: The method comprises the following steps: Step 1: Preparation of carbon nanotube film: dispersing carbon nanotubes in water to form a uniform and stable dispersion; spraying the dispersion onto the surface of release paper, and after drying, forming a carbon nanotube film adhered to the surface of the release paper; Step 2: Rolling and laminating: Rolling and laminating the carbon nanotube film and the desired adhesive film through a laminating machine to form a conductive adhesive film, and then laminating the conductive adhesive film with fibers to form a conductive prepreg; or rolling and laminating the carbon nanotube film and the desired prepreg through a laminating machine to form a conductive prepreg; Step 3: Cut and cure the conductive prepreg to the required specifications; Wherein, the step 1 includes: Step S11: dispersing the carbon nanotubes into water under the action of a dispersant to form a uniform and stable dispersion; Step S12: by controlling the aperture of the nozzle to be the first aperture d1, the dispersion is first sprayed onto the release paper and then dried to form a continuous carbon nanotube microfilm; Step S13: By controlling the pore size of the nozzle to a second pore size d2, the dispersion is first sprayed onto the release paper, and then dried to form a continuous carbon nanotube film adhered to the surface of the release paper; wherein, d1<d2; The number of times the dispersion is sprayed is n, and the initial preset number of sprays is m, where n and m are both positive integers; m<n; during the n-times dispersion spraying process, before the carbon nanotubes cover the release paper, the median droplet size of the spray sprayed with the initial preset number of sprays m is between 3 μm and 60 μm, and the value of m is 1-4.

2. The method for preparing a conductive prepreg containing a carbon nanotube film according to claim 1, characterized in that: In the step 1, the thickness of the carbon nanotube film is 0.5 μm-80 μm.

3. The method for preparing a conductive prepreg containing a carbon nanotube film according to claim 2, wherein: The surface resistance of the carbon nanotube film is 10-10000Ω.

4. The method for preparing a conductive prepreg containing a carbon nanotube film according to claim 1, wherein: In the step 2, at least one layer of carbon nanotube film is provided.

5. The method for preparing a conductive prepreg containing a carbon nanotube film according to claim 4, characterized in that: The concentration of carbon nanotubes in the dispersion is 0.5 wt % to 3.5 wt %.

6. The method for preparing a conductive prepreg containing a carbon nanotube film according to claim 5, characterized in that: The spraying and drying processes are performed at least once.

7. The method for preparing a conductive prepreg containing a carbon nanotube film according to claim 5, characterized in that: The dispersion also includes a polymer binder, and the total mass of the dispersant and the polymer binder is no more than twice that of the carbon nanotubes.

8. A carbon nanotube film, characterized in that: The preparation method of the carbon nanotube film is included in the preparation method of a conductive prepreg containing a carbon nanotube film as described in any one of claims 1 to 7, wherein the components of the carbon nanotube film include carbon nanotubes and a dispersant; the amount of the dispersant is 5%-40% of the mass of the carbon nanotubes; the type of the dispersant includes any one or more of sodium dodecylbenzenesulfonate, sodium stearate, polyvinyl pyrrolidone, and TritonX-100; the polymer binder is a thermosetting resin or thermoplastic resin with a glass transition temperature higher than 150°C; and the carbon nanotube film is compounded with the adhesive film to obtain a conductive adhesive film.

9. A conductive prepreg, characterized in that The conductive prepreg is prepared by the method for preparing a conductive prepreg containing a carbon nanotube film according to any one of claims 1 to 7, wherein the conductive prepreg comprises a conductive adhesive film.

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