A polyimide precursor, a carbon nanotube resistance stabilizer, and a preparation method and application thereof

Abstract

The application belongs to the technical field of preparation of structural and functional integrated composite materials, and specifically discloses a polyimide precursor, a carbon nanotube resistance stabilizer, and a preparation method and application thereof. The application provides a carbon nanotube resistance stabilizer prepared from a polyimide precursor (i.e. a polyamic acid containing phenolic hydroxyl groups), which has good water solubility and is environmentally friendly. Meanwhile, the carbon nanotube film or coating treated by the resistance stabilizer has the characteristics of high-temperature resistance and water resistance, can match the co-curing conditions of high-temperature curing resin prepreg, and the carbon nanomaterial after curing has good resistance stability and excellent interface with the composite material. The carbon nanotube resistance stabilizer provided by the application has good application prospect and high economic value.

Description

Technical Field

[0001] This invention belongs to the field of structural-functional integrated composite material preparation technology, specifically relating to a polyimide precursor, a carbon nanotube resistance stabilizer, their preparation methods and applications. Background Technology

[0002] Carbon nanotubes are nanomaterials with high aspect ratio, low density, and good electrical conductivity, attracting widespread attention in many fields. Currently, carbon nanotubes have been applied in conductive films, conductive polymers, and battery electrodes. Particularly in conductive films, carbon nanotubes have been used to prepare various lightweight, highly conductive nano-modified conductive film materials. Typical examples include carbon nanotube coatings composed almost entirely of carbon nanotubes, buckypaper obtained through carbon nanotube filtration, and carbon nanotube films grown via chemical vapor deposition (CVD). There are also modified conductive films composed of carbon nanotubes and other materials such as polymers; however, the former exhibits higher conductivity due to the smaller spacing between the carbon nanotubes.

[0003] However, for carbon nanotube films and coatings that are almost entirely composed of carbon nanotubes, their conductivity is significantly affected by the spacing between carbon nanotubes and the filler. In particular, when co-cured with prepregs of composite materials, the penetration of liquid resin and the high pressure during molding have a huge impact on the resistance of carbon nanotube films and coatings. The resistance value is difficult to maintain and control after co-curing, thus limiting its application range.

[0004] Existing technologies generally control the spacing between carbon nanotubes by introducing conductive binders into the carbon nanotube film, thereby achieving relatively stable resistance. Conductive binders typically include polyvinylidene fluoride (PVDF), sodium carboxymethyl cellulose (CMC), and polyvinylpyrrolidone (PVP). For example, Chinese patent application CN117402410A discloses a conductive hollow glass microsphere that uses a binder (selected from one or more thermoplastic polyaryletherketones, PVDF, polyetheretherketones, polyimide, polyetherimide, and polyvinyl alcohol) to maintain the integrity of the conductive network of the carbon nanomaterial, achieving a balance between conductivity and resistance to network disruption by controlling the amount of binder used. However, PVDF is an oil-soluble polymer, which can cause environmental pollution. Sodium carboxymethyl cellulose (CMC) and PPVP have low heat distortion temperatures, and when co-cured with prepregs at high temperatures and pressures, the carbon nanotubes are prone to displacement, leading to uncontrolled resistance. Therefore, there is an urgent need to develop a water-soluble, high-temperature resistant carbon nanotube resistance stabilizer. Summary of the Invention

[0005] The main technical problem solved by this invention is to provide a polyimide precursor and a water-soluble carbon nanotube resistance stabilizer prepared from the precursor. The carbon nanotube film treated with the resistance stabilizer can match the conditions for co-curing with high-temperature curing resin prepreg, maintain the resistance stability of the carbon nanotube film, and have good interfacial adhesion with the composite material.

[0006] Meanwhile, the present invention also provides a method for preparing polyimide precursors and carbon nanotube resistance stabilizers, as well as their applications.

[0007] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0008] A polyimide precursor, specifically a polyamic acid containing phenolic hydroxyl groups, has the structure shown in Formula I:

[0009]

[0010] In Formula I, X1 is selected from the following groups:

[0011]

[0012]

[0013] X2 is selected from the following groups:

[0014]

[0015]

[0016] X3 is selected from the following groups:

[0017]

[0018] In a preferred embodiment of the present invention, in molar quantities, y:(x+y)=0.05-0.25:1.

[0019] A method for preparing a polyimide precursor includes the following steps:

[0020] Diamine monomer A, (phenolic hydroxyl-containing) diamine monomer B, and dianhydride monomer are mixed and subjected to solution polycondensation reaction to obtain polyamic acid containing phenolic hydroxyl groups, which is the polyimide precursor.

[0021] The diamine monomer A is selected from the following compounds:

[0022]

[0023]

[0024] The diamine monomer B is selected from the following compounds:

[0025]

[0026]

[0027] The dianhydride monomer is selected from the following compounds:

[0028]

[0029]

[0030] In a preferred embodiment of the present invention, the molar ratio of diamine monomer B to dianhydride monomer (or the sum of the molar amounts of diamine monomer A and diamine monomer B) is 0.05-0.25:1. The molar ratio of diamine monomer A to dianhydride monomer is 0.75-0.95:1.

[0031] A carbon nanotube resistance stabilizer, the raw materials for preparation include: polyimide precursor, organic tertiary amine and polyacid; in molar amounts, polyimide precursor: organic tertiary amine: polyacid = 1:0.5-4:0.01-0.25.

[0032] In a preferred embodiment of the present invention, the organic tertiary amine is selected from one or more of triethylamine, pyridine, triethanolamine, dimethylisopropylamine, dimethylisopropanolamine, diethylmonoethanolamine, and diethanolmonoisopropanolamine.

[0033] As a preferred embodiment of the present invention, the polyacid is selected from one or more of terephthalic acid, phthalic acid, isophthalic acid, triterephthalic acid, maleic acid, succinic acid, naphthalic acid (such as 2,6-naphthalic acid), biphenyl acid (such as 4,4'-biphenyl acid), etc.

[0034] A method for preparing a carbon nanotube resistance stabilizer includes the following steps:

[0035] A carbon nanotube resistance stabilizer was obtained by mixing a polyimide precursor, an organic tertiary amine, and a polyacid.

[0036] The application of a carbon nanotube resistance stabilizer includes, but is not limited to, any one of the following:

[0037] (1) Used as a treatment agent for (modified) carbon nanotube films or coatings;

[0038] (2) Used as a co-dispersion modifier for carbon nanotube slurry.

[0039] In a preferred embodiment of the present invention, when the carbon nanotube resistance stabilizer is used as a treatment agent for (modified) carbon nanotube films or carbon nanotube coatings, the application includes:

[0040] A water-based treatment solution was prepared by mixing carbon nanotube resistance stabilizer with water.

[0041] The (modified) carbon nanotube film or carbon nanotube coating is immersed in an aqueous treatment solution, removed and dried, and then subjected to thermal imidization treatment to obtain a carbon nanomaterial with stable electrical resistance.

[0042] Specifically, the mass percentage concentration of carbon nanotube resistance stabilizer in the aqueous treatment solution is 1%-16%.

[0043] Specifically, the temperature of the thermal imidization treatment is 180-260℃, and the time is 2-5 hours.

[0044] In a preferred embodiment of the present invention, when the carbon nanotube resistance stabilizer is used as a co-dispersion modifier for carbon nanotube slurry, the application includes:

[0045] A water-based treatment solution was prepared by mixing carbon nanotube resistance stabilizer with water.

[0046] Carbon nanotubes are made into an aqueous carbon nanotube slurry, which is then mixed with an aqueous treatment liquid to form a co-treatment slurry. The carbon nanotube coating formed by the co-treatment slurry is subjected to thermal imidization treatment to obtain a carbon nanomaterial with stable electrical resistance.

[0047] Specifically, the amount of carbon nanotube resistance stabilizer used in the aqueous treatment solution is 25%-280% of the mass of carbon nanotubes.

[0048] Specifically, the temperature of the thermal imidization treatment is 180-260℃, and the time is 2-5 hours.

[0049] As a preferred embodiment of the present invention, the application further includes: co-curing resistively stable carbon nanomaterials with high-temperature curing resin prepregs under a molding process to obtain a resin composite material containing carbon nanomaterials.

[0050] Specifically, the high-temperature curing resin prepreg is selected from one or more of epoxy resin prepreg, bismaleimide resin prepreg, etc.

[0051] The beneficial effects of this invention are:

[0052] This invention provides a polyimide precursor and a carbon nanotube resistance stabilizer prepared from the precursor. The resistance stabilizer has good water solubility and is environmentally friendly. At the same time, the carbon nanotube film or coating treated with the resistance stabilizer has the characteristics of high temperature resistance and water resistance, which can match the co-curing conditions of high temperature curing resin prepreg. Furthermore, the cured carbon nanomaterial has good resistance stability and excellent interface with the composite material. Attached Figure Description

[0053] Figure 1 The change in the ratio of resistance to initial resistance after co-curing carbon nanotube coatings treated with different concentrations of resistance stabilizers with quartz fiber fabric-reinforced epoxy resin prepreg QW120 / 1316.

[0054] Figure 2 The resistance of carbon nanotube coatings coated with different concentration ratios of resistance stabilizer / carbon nanotube slurry and the resistance changes after co-curing with quartz fiber fabric reinforced epoxy resin prepreg QW120 / 1316.

[0055] To more clearly illustrate the technical solution protected by this invention, the accompanying drawings in the embodiments and / or experimental examples have been briefly described above. It should be understood that the above drawings should not be construed as any limitation on the scope of protection of this invention. Detailed Implementation

[0056] The technical solution of the present invention will be described in detail below through specific embodiments. These embodiments are intended to further illustrate the content of the present invention, but are not intended to limit the scope of protection of the claims of the present invention.

[0057] Unless otherwise specified, the raw materials, reagents, equipment, etc. used in the following examples and comparative examples are all commercially available products.

[0058] Solution Description

[0059] This invention provides a polyimide precursor and a water-soluble carbon nanotube resistance stabilizer prepared from the precursor. The resistance stabilizer is water-soluble and environmentally friendly, and after high-temperature curing, it has good high-temperature resistance and good water resistance. When used to treat carbon nanotube films or coatings, it can be matched with high-temperature epoxy resin prepreg or bismaleimide resin prepreg co-curing process, and can form good interfacial adhesion with composite material matrix.

[0060] In order to achieve the purpose of the invention, the following design and technical improvements have been creatively made:

[0061] (1) Water solubility, water resistance, and heat resistance

[0062] To achieve the desired water solubility before curing, high water resistance after curing, and good heat resistance, this invention innovatively designs a carbon nanotube resistance stabilizer, unlike existing adhesive materials. The stabilizer primarily uses a polyimide precursor (polyamic acid containing phenolic hydroxyl groups), organic tertiary amines, and polyacids. Before curing, this material exists as a quaternary ammonium salt of polyamic acid, exhibiting excellent water solubility and thus being environmentally friendly. After curing, the final product is polyimide, which possesses excellent water resistance and heat resistance, thereby simultaneously achieving environmental friendliness, high water resistance, and high temperature resistance.

[0063] Preferably, to achieve water solubility in the material, polyamic acid forms soluble quaternary ammonium salts with common tertiary amines such as pyridine, triethylamine, triethanolamine, diethylmonoethanolamine, and diethanolmonoisopropylamine. When the amount of tertiary amine exceeds 20% of the carboxyl group, the system exhibits good water solubility. Furthermore, the polyacids in the system also possess good water solubility and can form a homogeneous water-soluble system together with the polyamic acid quaternary ammonium salt.

[0064] (2) Stability issues of resistance control

[0065] To achieve good resistance stability control, it is necessary to ensure that trace amounts of polyamic acid, after bonding carbon nanotubes and thermal imidization, possess good heat resistance and high mechanical strength to cope with the high curing temperature and pressure during autoclave curing. However, directly using polyamic acid quaternary ammonium salts fails to achieve the desired effect. For example, in Comparative Example 1, after treatment with 3 wt% of conventional polyamic acid quaternary ammonium salts (this concentration does not include the mass of tertiary amine), the resistance of carbon nanotube coatings with resistivity of 50 Ω / sq and 330 Ω / sq increased by 200%-220% after co-curing with quartz fiber reinforced bismaleimide resin prepreg QW280 / 5429, indicating insufficient resistance stability control.

[0066] Compared to conventional polyamic acid quaternary ammonium salts, the system of polyacids and polyamic acid quaternary ammonium salts containing phenolic hydroxyl groups in this invention achieved good resistance control, with resistance change rates ranging from 95% to 140% (see Examples 1-11). The reason for this is that the compound system has the following three synergistic effects: (a) Conventional polyamic acid quaternary ammonium salts are prone to degradation when heated in an aqueous system, resulting in a relatively low molecular weight. The polyacids, however, act as crosslinking agents (as shown in Formula II below), increasing their molecular weight and mechanical properties; (b) After bonding, conventional polyamic acid quaternary ammonium salts, due to the relatively fixed positions between the trace binder and carbon nanotubes, generate high stress within the system after drying, easily causing bond embrittlement, especially at high molding temperatures and pressures. The small-molecule polyacids and polyamic acid are both polyacids with good compatibility, playing a toughening role before crosslinking and reducing the possibility of brittle fracture; (c) The esterification crosslinking of the polyacids and polyamic acid containing phenolic hydroxyl groups is reversible, reducing curing stress to some extent. Therefore, the design of this compound system ensures good adhesion of the resistance stabilizer to carbon nanotubes under low dosage and high temperature and high pressure molding conditions, thus achieving stable control of resistance.

[0067]

[0068] (3) Interface problems of co-cured composite materials

[0069] Another significant effect of the compound system of this invention is the simultaneous improvement of the interfacial properties of the co-cured composite material. Traditional polyimide systems, due to their relatively rigid molecular chains and lateral chain extension, are difficult to entangle with other binder components, resulting in weak adhesion. However, the compound system of this invention contains abundant phenolic hydroxyl and carboxyl groups (derived from polyamic acid), and the esterification reaction of these two groups is incomplete. Therefore, it contains a large number of active groups that can react with epoxy resin and bismaleimide resin, significantly improving the interfacial adhesion performance of the system (see Examples 1-11). To avoid the adverse effects of excessive polyamic acid (such as a decrease in glass transition temperature), the amount of polyamic acid is controlled to be 20%-60% of the molar number of phenolic hydroxyl groups in the polyamic acid. At this point, the doping amount is less than 8% of the total mass, and has almost no effect on the glass transition temperature of the system.

[0070] (4) Application

[0071] The aqueous carbon nanotube resistance stabilizer provided by this invention is generally dissolved in water first, and then the aqueous treatment solution is used to treat the carbon nanotube film or coating. The rate of change in resistance of the carbon nanotube film or coating before and after curing shows a trend of extreme inflection at both ends with the amount of resistance stabilizer used, such as... Figure 1 As shown in the figure, the mass percentage concentration of carbon nanotube resistance stabilizer in the aqueous treatment solution needs to be controlled at 1%-16% (preferably 2%-12%), especially for the initial treatment. Microscopic analysis shows that at lower concentrations, the main reason for the increased resistance change is the displacement and network disruption of carbon nanotubes during co-curing, while at higher concentrations, the main reason is the increased spacing between carbon nanotubes during treatment, leading to a rapid increase in interfacial resistance. The figure also shows that when the concentration of the aqueous treatment solution is controlled within a certain range, the resistance stabilizer has a good effect; the resistance of the carbon nanotube coating after co-curing can be controlled to 85%-110% of the initial resistance, while without the resistance stabilizer, the resistance can increase to about 850%, indicating poor controllability.

[0072] Furthermore, this resistance stabilizer can also be dissolved in aqueous carbon nanotube slurry and used together with the carbon nanotubes, but its dosage should be 10%-280% of the mass of the carbon nanotubes. Figure 2 As shown, with the increase of the ratio of resistance stabilizer to carbon nanotubes, the resistance of the conductive film coated with this slurry first increases slowly with the increase of the ratio. When it is higher than 280%, the resistance increases rapidly, indicating that the resistance controllability deteriorates. At the same time, the amount of slurry required to coat the same resistance film increases rapidly. Especially after co-curing, the resistance of the film with excessive stabilizer increases significantly, and the resistance controllability is poor.

[0073] As can be seen from the above design and improvements, the material of the present invention has the following significant advantages over the prior art:

[0074] (1) In the prior art, PVDF, which is soluble in NMP, and sodium carboxymethyl cellulose, which is soluble in water, are often used as binders. The former causes environmental pollution and increases costs, while the latter has poor water resistance and heat resistance. The material of the present invention perfectly solves the above problems.

[0075] (2) The material of the present invention has good mechanical properties after curing, which is sufficient to maintain the structural and performance stability of the treated carbon nanotube film and coating under high temperature resin swelling and pressure environment, and solves the problem that the mechanical properties of ordinary polyamic acid quaternary ammonium salts decrease significantly during the curing process and are insufficient to maintain the resistance stability.

[0076] (3) As an additional effect of the material of the present invention, the treated carbon nanotube film and coating have good interfacial bonding properties with the composite material.

[0077] Example 1

[0078] This embodiment provides a polyimide precursor having the structure shown in Formula I:

[0079]

[0080] In Formula I, X1 represents the following groups:

[0081]

[0082] X2 represents the following groups:

[0083] X3 is one of the following groups:

[0084] In molar quantities, y:(x+y)=0.1:1.

[0085] The method for preparing the polyimide precursor provided in this embodiment includes the following steps:

[0086] Take 108g (0.9mol) of diamine monomer A: p-phenylenediamine and 12.4g (0.1mol) of diamine monomer B: 2-hydroxy-p-phenylenediamine, add them to 1500g of N,N-dimethylacetamide (DMAc), stir to dissolve, and place in an ice-water bath; then weigh 218g (PMDA, 1mol) of pyromellitic dianhydride, and slowly add it to the above diamine solution under constant stirring. After all the solution is added, stir for another 1h to obtain a DMAc solution of polyamic acid containing phenolic hydroxyl groups.

[0087] This embodiment provides a carbon nanotube resistance stabilizer, its preparation method, and its application, including:

[0088] Add 8.3 g (0.05 mol) of phthalic acid to the DMAc solution containing phenolic hydroxyl polyamic acid prepared above and stir until homogeneous; then add 40.4 g of triethylamine and continue stirring for 10 min; subsequently add it to 9700 g of deionized water to obtain an aqueous treatment solution containing 3 wt% carbon nanotube resistance stabilizer (when calculating this mass percentage concentration, the mass of the resistance stabilizer is not included in the mass of triethylamine);

[0089] Take a piece of buckypaper (a carbon nanotube film formed by filtering a carbon nanotube aqueous dispersion through micropores) with a surface resistance R1 of 180Ω, immerse it in the above treatment solution; then take it out, dry it, heat it to 240℃ and keep it for 3 hours to allow the resistance stabilizer to be fully imidized.

[0090] The treated buckypaper was co-laid with quartz fiber fabric-reinforced epoxy resin prepreg QW120 / 1316, with the layup sequence being [0|90]. 20 The base paper is placed in the middle layer; then it is cured under the molding process of QW120 / 1316, with a curing pressure of 0.6MPa and a curing temperature of 180℃. After curing, it is cooled to below 60℃ to obtain the composite material board.

[0091] Experimental method: The resistance R2 of the co-cured bacillus paper was measured, and the tensile strength of the coating of the composite material was tested after processing the above sample.

[0092] Experimental Results: The carbon nanotube resistance stabilizer prepared in this embodiment forms a homogeneous and transparent solution in water. After treatment, R2 / R1 is 1.02, while the ratio of R2 / R1 for the sample prepared from untreated bacillus paper is 1.58, indicating that the resistance stabilizer significantly improves the resistance stability of the bacillus paper. The tensile strength of the composite coating is 34.3 MPa for the treated sample, 29.5 MPa for the sample prepared from untreated bacillus paper, and 36.9 MPa for conventional unintercalated QW120 / 1316.

[0093] Examples 2-4

[0094] Compared to Example 1, Examples 2-4 changed the amount or concentration of raw materials (as shown in Table 1), while the preparation method and application were basically the same as in Example 1.

[0095] Table 1. Preparation information and performance of Examples 2-4

[0096]

[0097] Example 5

[0098] This embodiment provides a polyimide precursor, the preparation method of which includes the following steps:

[0099] Take 169g (0.92mol) of diamine monomer A and 20.6g (0.05mol) of diamine monomer B, add them to 2000g of N,N-dimethylacetamide (DMAc), stir to dissolve, and place in an ice-water bath; then weigh 294g (1mol) of dianhydride, and slowly add it to the above diamine solution under constant stirring. After all the dianhydride has been added, stir for another 1 hour to obtain a DMAc solution of polyamic acid containing phenolic hydroxyl groups.

[0100] Diamine monomer A is:

[0101] Diamine monomer B is:

[0102] The dianhydride monomer is:

[0103] This embodiment provides a carbon nanotube resistance stabilizer, its preparation method, and its application, including:

[0104] Add 11.3 g (0.096 mol) of succinic acid to the DMAc solution containing phenolic hydroxyl polyamic acid prepared above and stir until homogeneous; then add 19.14 g of dimethyl isopropylamine and continue stirring for 10 min; then add it to 6254 g of deionized water to obtain an aqueous treatment solution containing 6 wt% carbon nanotube resistance stabilizer (excluding dimethyl isopropylamine).

[0105] Carbon nanotubes were dispersed in water to form a homogeneous solution with a concentration of 1.6 wt%. Then, a film was coated on aramid fabric to obtain a carbon nanotube conductive film attached to the aramid fabric with a surface resistance R1 of 500 Ω. The film was then immersed in the above treatment solution. After that, it was taken out, dried, and heated to 220°C and kept for 3 hours to allow the resistance stabilizer to be fully imidized.

[0106] The carbon nanotube conductive film attached to the aramid fabric was co-laid with quartz fiber fabric-reinforced epoxy resin prepreg QW120 / 1316, with the layup sequence being [0|90]. 20 A carbon nanotube conductive film is placed in the middle layer; then it is cured under the molding process of QW120 / 1316, with a curing pressure of 0.6MPa and a curing temperature of 180℃. After curing, it is cooled to below 60℃ to obtain a composite material plate.

[0107] Experimental method: The resistance R2 of the co-cured carbon nanotube film was measured, and the tensile strength of the composite material was tested after processing the above sample.

[0108] Experimental results: After treatment, R2 / R1 was 1.27, while the untreated carbon nanotube film, after co-curing using the same method, had a resistivity ratio of 6.94, indicating that the resistance stabilizer significantly improved the resistivity stability of the carbon nanotube conductive film. The tensile strength of the composite material was 35.9 MPa for the treated sample.

[0109] Example 6

[0110] This embodiment provides a polyimide precursor, the preparation method of which includes the following steps:

[0111] Take 154g (0.78mol) of diamine monomer A and 61.6g (0.22mol) of diamine monomer B, add them to 2000g of N,N-dimethylacetamide (DMAc), stir to dissolve, and place in an ice-water bath; then weigh 294g (1mol) of dianhydride monomer, slowly add it to the above diamine solution under constant stirring, and stir for 1 hour after all the solution is added to obtain a DMAc solution of polyamic acid containing phenolic hydroxyl groups.

[0112] Diamine monomer A is:

[0113] Diamine monomer B is:

[0114] The dianhydride monomer is:

[0115] This embodiment provides a carbon nanotube resistance stabilizer, its preparation method, and its application, including:

[0116] Add 37g (0.176mol) of isophthalic acid to the DMAc solution containing phenolic hydroxyl polyamic acid prepared above and stir until homogeneous; then add 45.1g of a mixture of triethylamine and pyridine in a mass ratio of 1:1 and continue stirring for 10min; then add it to 7117g of deionized water to obtain an aqueous treatment solution containing 6wt% carbon nanotube resistance stabilizer (excluding triethylamine and pyridine).

[0117] Carbon nanotubes were dispersed in water to form a dispersion with a concentration of 4.0 wt%. This dispersion was then combined with the above-mentioned aqueous treatment solution to prepare four mixed dispersions with carbon nanotube concentrations of 2 wt% and stabilizer concentrations of 0.6 wt%, 1.0 wt%, 2.0 wt%, and 4.0 wt%, respectively. The mixed dispersions were then brushed onto glass cloth, and the resistance R1 after drying was controlled to be 180 Ω / sq. The coated glass cloth was then heated to 200°C in an oven and held for 2 hours to allow the resistance stabilizer to be fully imidized. Finally, any residual tertiary amines were removed by vacuum extraction.

[0118] The glass cloth-carbon nanotube membranes treated with different mixed dispersions were co-laid with quartz fiber fabric-reinforced bismaleimide resin prepreg QW280 / 5429, with the layup sequence being [0|90]. 10 A glass cloth-carbon nanotube film is placed in the middle layer; then it is cured under the molding process of QW280 / 5429, with a curing pressure of 0.6MPa and a curing temperature of 200℃. After curing, it is cooled to below 60℃ to obtain a composite material board.

[0119] Experimental method: The resistance R2 of the co-cured carbon nanotube film was measured, and the tensile strength of the composite material was tested after processing the above sample.

[0120] Experimental Results: The co-dispersion prepared in this embodiment exhibits good stability and can be stored for extended periods. The resistivities of the carbon nanotube films coated with the four different dispersions are 237 Ω / sq, 202 Ω / sq, 172 Ω / sq, and 179 Ω / sq, respectively, with resistance change ratios of 132%, 112%, 95.5%, and 99.4%. The tensile strengths are 29.4 MPa, 31.5 MPa, 37.2 MPa, and 34.2 MPa, respectively, while the tensile strength of the composite material without the resistive layer is 33.7 MPa.

[0121] Examples 7-9

[0122] Compared to Example 6, Examples 7-9 changed the amount or concentration of raw materials (as shown in Table 2), but the preparation method and application were basically the same as in Example 6.

[0123] Table 2. Preparation information and performance of Examples 7-9

[0124]

[0125]

[0126] Example 10

[0127] This embodiment provides a polyimide precursor, the preparation method of which includes the following steps:

[0128] Take 223g (0.9mol) of diamine monomer A and 25.8g (0.1mol) of diamine monomer B, add them to 2000g of N,N-dimethylacetamide (DMAc), stir to dissolve, and place in an ice-water bath; then weigh 294g (1mol) of dianhydride monomer, slowly add it to the above diamine solution under constant stirring, and stir for 1 hour after all the solution is added to obtain a DMAc solution of polyamic acid containing phenolic hydroxyl groups.

[0129] Diamine monomer A is:

[0130] Diamine monomer B is:

[0131] The dianhydride monomer is:

[0132] This embodiment provides a carbon nanotube resistance stabilizer, its preparation method, and its application, including:

[0133] 13.0 g (0.06 mol) of 2,6-naphthalenedic acid was added to the DMAc solution containing phenolic hydroxyl polyamic acid prepared above and stirred until homogeneous; then 101 g of triethylamine was added and stirred for another 10 min; subsequently, it was added to 11900 g of deionized water to obtain an aqueous treatment solution containing 4 wt% carbon nanotube resistance stabilizer (excluding triethylamine).

[0134] Take a piece of barkey paper with a surface resistance R1 of 75Ω and immerse it in the above treatment solution; then take it out, heat it to 200℃ and keep it for 3 hours to allow the resistance stabilizer to be fully imidized, and then vacuum remove any possible residual tertiary amine.

[0135] The treated buckypaper was co-laid with quartz fiber fabric-reinforced bismaleimide resin prepreg QW280 / 5429, with the layup sequence being [0|90]. 20 The base paper is placed in the middle layer and then cured under the molding process of QW280 / 5429. The curing pressure is 0.6MPa and the curing temperature is 200℃. After curing, it is cooled to below 60℃ to obtain the composite material board.

[0136] Experimental method: The resistance R2 of the co-cured bacillus paper was measured, and the tensile strength of the composite material was tested after processing the above sample.

[0137] Experimental results: In the co-cured composite obtained above, the surface resistivity of the cured bacillus paper was measured to be 78 Ω, and the R2 / R1 ratio was 1.04, indicating that the resistance stabilizer significantly improved the resistance curing stability of the bacillus paper. The tensile strength of the composite material was 37.8 MPa.

[0138] Example 11

[0139] This embodiment provides a polyimide precursor, the preparation method of which includes the following steps:

[0140] Take 180g (0.9mol) of diamine monomer A and 25.8g (0.1mol) of diamine monomer B, add them to 2000g of N,N-dimethylacetamide (DMAc), stir to dissolve, and place in an ice-water bath; then weigh 294g (1mol) of dianhydride monomer, slowly add it to the above diamine solution under constant stirring, and stir for 1 hour after all the solution is added to obtain a DMAc solution of polyamic acid containing phenolic hydroxyl groups.

[0141] Diamine monomer A is:

[0142] Diamine monomer B is:

[0143] The dianhydride monomer is:

[0144] This embodiment provides a carbon nanotube resistance stabilizer, its preparation method, and its application, including:

[0145] 24.2 g (0.1 mol) of 4,4'-biphenyl dicarboxylic acid was added to the DMAc solution containing phenolic hydroxyl polyamic acid prepared above and stirred until homogeneous; then 45.1 g of a mixture of triethylamine and diethanol monoisopropanolamine in a mass ratio of 2:1 was added and stirring was continued for 10 min; subsequently, it was added to 7266 g of deionized water to obtain an aqueous treatment solution containing 6 wt% carbon nanotube resistance stabilizer (excluding triethylamine and diethanol monoisopropanolamine);

[0146] Carbon nanotubes were dispersed in water to form a dispersion with a concentration of 4.0 wt%. This dispersion was then combined with the above-mentioned aqueous treatment solution to prepare three mixed dispersions with carbon nanotube concentrations of 2 wt% and stabilizer concentrations of 1.0 wt%, 2.0 wt%, and 3.0 wt%, respectively. The mixed dispersions were then brushed onto glass cloth, and the resistance R1 after drying was controlled to be 180 Ω / sq. Subsequently, the coated glass cloth was heated to 200°C in an oven and kept there for 3 hours to allow the resistance stabilizer to be fully imidized. Then, any residual tertiary amines were removed by vacuum extraction.

[0147] The glass cloth-carbon nanotube membranes treated with different mixed dispersions were co-laid with quartz fiber fabric-reinforced epoxy resin prepreg QW120 / 1316, with the layup sequence being [0|90]. 20 A glass cloth-carbon nanotube film is placed in the middle layer; then it is cured under the molding process of QW120 / 1316, with a curing pressure of 0.6MPa and a curing temperature of 180℃. After curing, it is cooled to below 60℃ to obtain a composite material board.

[0148] Experimental method: The resistance R2 of the co-cured carbon nanotube film was measured, and the tensile strength of the composite material was tested after processing the above sample.

[0149] Experimental Results: The R2 / R1 ratios of the three treatment solutions for the obtained composite materials were 1.02, 0.94, and 1.01, respectively. The resistivity change rate of the carbon nanotube film without added resistance stabilizer was as high as 9.32 after coating, indicating that the resistance stabilizer significantly improved the curing resistance stability of the carbon nanotube film. The tensile strengths of the composite materials were 31.5 MPa, 34.6 MPa, and 37.2 MPa, showing an increasing trend, with the composite material without added resistance stabilizer having a tensile strength of 27.5 MPa.

[0150] Comparative Example 1

[0151] This comparative example provides a polyimide precursor (i.e., a conventional polyamic acid quaternary ammonium salt), and the preparation method includes the following steps:

[0152] Take 184g (1.0mol) of diamine monomer and add it to 2000g of N,N-dimethylacetamide (DMAc). Stir to dissolve and place in an ice-water bath. Then weigh 294g (1mol) of dianhydride monomer and slowly add it to the above diamine solution under continuous stirring. After all the solution is added, stir for another 1h to obtain a DMAc solution of polyamic acid.

[0153] The diamine monomer is:

[0154] The dianhydride monomer is:

[0155] This comparative example provides a carbon nanotube binder, its preparation method, and its applications, including:

[0156] Add 60g of triethylamine to the polyamic acid DMAc solution prepared above and continue stirring for 10min; then add it to 16333g of deionized water to obtain a treatment solution containing 3wt% binder (excluding triethylamine);

[0157] Carbon nanotubes were dispersed in water to form a dispersion with a concentration of 2.0 wt%. The above mixed dispersion was brushed onto glass cloth, and the resistance R1 was controlled to be 50 Ω / sq and 300 Ω / sq. The coated glass cloth was then heated to 200°C in an oven and kept for 3 hours to allow the resistance stabilizer to be fully imidized. Then, any residual tertiary amine was removed by vacuum extraction.

[0158] The glass cloth-carbon nanotube films with different surface resistivities were co-laid with quartz fiber fabric-reinforced bismaleimide resin prepreg QW280 / 5429, with the layup sequence being [0|90]. 10 A glass cloth-carbon nanotube film is placed in the middle layer; then it is cured under the molding process of QW280 / 5429, with a curing pressure of 0.6MPa and a curing temperature of 200℃. After curing, it is cooled to below 60℃ to obtain a composite material board.

[0159] Experimental method: The resistance R2 of the co-cured carbon nanotube film was measured, and the tensile strength of the composite material was tested after processing the above sample.

[0160] Experimental results: After treatment with 3 wt% conventional polyamic acid quaternary ammonium salt, the resistivity of the co-cured coating was 151 Ω / sq and 1040 Ω / sq, which were 202% and 215% higher than the coating resistivity (50 Ω / sq and 330 Ω / sq), respectively. The tensile strengths were 21.6 MPa and 28.2 MPa, respectively.

[0161] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent transformations made based on the content of the present invention specification, or direct or indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A carbon nanotube resistance stabilizer, characterized in that: The raw materials for preparation include polyimide precursor, organic tertiary amine and polyacid; in molar amounts, the ratio of polyimide precursor: organic tertiary amine: polyacid is 1:0.5-4:0.01-0.

25. The polyimide precursor has the structure shown in Formula I: Formula I In Formula I, X1 is selected from the following groups: ， ， ， ， ， ， ， ； X2 is selected from the following groups: ， ， ； ， ， ， ； X3 is selected from the following groups: ， ， ， ， ； In molar quantities, y : (x + y) = 0.05 - 0.25 : 1; The organic tertiary amine is selected from one or more of triethylamine, pyridine, triethanolamine, dimethylisopropylamine, dimethylisopropanolamine, diethylmonoethanolamine, and diethanolmonoisopropanolamine; The polyacid is selected from one or more of terephthalic acid, phthalic acid, isophthalic acid, triphthalic acid, maleic acid, succinic acid, naphthalic acid, and biphenyl acid.

2. A method for preparing the carbon nanotube resistance stabilizer as described in claim 1, characterized in that: Includes the following steps: A carbon nanotube resistance stabilizer was obtained by mixing a polyimide precursor, an organic tertiary amine, and a polyacid.

3. An application of the carbon nanotube resistance stabilizer as described in claim 1, characterized in that: When carbon nanotube resistance stabilizers are used as treatment agents for carbon nanotube films or carbon nanotube coatings, the applications include: A carbon nanotube resistance stabilizer is prepared into an aqueous treatment solution; the mass percentage concentration of the carbon nanotube resistance stabilizer in the aqueous treatment solution is 1%-16%. The carbon nanotube film or carbon nanotube coating is immersed in an aqueous treatment solution, taken out and dried, and then subjected to thermal imidization treatment to obtain a carbon nanomaterial with stable resistance. When carbon nanotube resistance stabilizers are used as co-dispersion modifiers for carbon nanotube slurries, the applications include: A carbon nanotube resistance stabilizer is prepared into an aqueous treatment solution; the amount of carbon nanotube resistance stabilizer in the aqueous treatment solution is 25%-280% of the mass of carbon nanotubes; Carbon nanotubes are made into an aqueous carbon nanotube slurry, which is then mixed with an aqueous treatment liquid to form a co-treatment slurry. The carbon nanotube coating formed by the co-treatment slurry is subjected to thermal imidization treatment to obtain a carbon nanomaterial with stable electrical resistance.

4. The application according to claim 3, characterized in that: The thermal imidization treatment is performed at a temperature of 180-260℃ for 2-5 hours.

5. The application according to claim 3, characterized in that: The application also includes: co-curing resistively stable carbon nanomaterials with high-temperature curing resin prepregs under a molding process to obtain a resin composite material containing carbon nanomaterials; The high-temperature curing resin prepreg is selected from one or two of epoxy resin prepreg and bismaleimide resin prepreg.

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