A polyimide adhesive with good adhesion matching with composite materials and its preparation method

Abstract

A polyimide adhesive with good bonding compatibility with composite materials and its preparation method. The present invention relates to a polyimide adhesive and its preparation method. It solves the problems of poor matching, low bonding strength, and insufficient heat resistance existing in the integral bonding of existing polyimide adhesives and polyimide composite materials. The polyimide adhesive is made of polyimide resin, bonding enhancer, bonding low-viscosity promoter, inorganic filler, and solvent; the preparation method: First, prepare polyimide resin; Second, weigh and stir. The present invention is used for a polyimide adhesive with good bonding compatibility with composite materials and its preparation.

Description

Technical Field

[0001] The present invention relates to a polyimide adhesive and a preparation method thereof. Background Art

[0002] With the annual increase in the flight speed of aircraft in industries such as aerospace, resin-based composite materials are currently generally used for surface structures such as skins instead of metals such as titanium alloys and aluminum alloys before, so as to meet the usage requirements such as weight reduction and high speed. Among them, the polyimide resin-based composite material has a service temperature of 300 °C and above, especially has good mechanical properties and thermal stability at 400 °C to 500 °C, and is more suitable for the weight reduction requirements of high-temperature and high-speed aircraft. During the molding process of polyimide composite materials, a special polyimide adhesive is required to form some special structures, such as the molding of complex structural parts such as stiffeners and reinforcing beams.

[0003] At present, due to requirements such as low cost and high load-bearing, composite material structures generally adopt an integral molding method such as co-curing, and the composite material skin, stiffeners, and reinforcing beams are prepared as a process using prepregs, including epoxy-based composite materials, bismaleimide-based composite materials, cyanate ester composite materials, and polyimide composite materials, all of which adopt a similar integral curing molding method.

[0004] However, existing materials and literature reports mainly focus on how to improve the bonding strength of polyimide adhesives to metals and films, and improve the bonding performance at high and low temperatures. There is little discussion on the bonding performance of polyimide composite materials, especially the integral bonding performance and its interface during the co-curing molding of polyimide composite prepregs. This is because although existing polyimide adhesives can bond metals to achieve high bonding strength and cohesive strength, it is difficult to form an interfacial layer with sufficient strength on the rough surface and difficult-to-wet surface of composite materials, resulting in bonding failure. Therefore, the integral bonding molding of polyimide composite materials is restricted by reasons such as the matching of adhesives, and has not been completely solved at present.

[0005] Among many polyimide adhesives, improving the matching with the polyimide composite material substrate and achieving the co-curing bonding effect with the polyimide composite prepreg (the state where the composite material is impregnated with resin to form a film before curing) can improve the structural strength of the overall component, reduce the energy consumption of integrated processing, and avoid interfacial stress and bonding failure caused by multiple bonding molding. How to improve the bonding interface obtained by co-curing with polyimide composite prepregs, improve the co-curing bonding strength, and obtain a bonding effect at a higher temperature is a technical problem that urgently needs to be solved in the prior art. Summary of the Invention

[0006] The present invention aims to solve the problems of poor matching, low bonding strength, and insufficient heat resistance existing in the integral bonding of existing polyimide adhesives and polyimide composites, and provides a polyimide adhesive with good bonding matching with composites and a preparation method thereof.

[0007] A polyimide adhesive with good bonding matching with composites is prepared from 100 parts by weight of polyimide resin, 2 to 5 parts of bonding enhancer, 2 to 15 parts of bonding low-viscosity promoter, 0.1 to 10 parts of inorganic filler, and 100 to 200 parts of solvent;

[0008] The bonding enhancer is an aromatic diamine with a melting point ≤ 150 °C;

[0009] The bonding low-viscosity promoter is a bis(amino-terminated) siloxane-structured substance;

[0010] The inorganic filler consists of metal oxide and graphite-like substance, and the mass ratio of the metal oxide to the graphite-like substance is 1:(0.1 - 1.0);

[0011] The structural general formula of the polyimide resin is:

[0012]

[0013] where n is 19 - 49;

[0014] Ar1 is

[0015] Ar2 is

[0016] A preparation method of a polyimide adhesive with good bonding matching with composites is carried out according to the following steps:

[0017] I. Under a nitrogen atmosphere, add aromatic dianhydride to N,N-dimethylacetamide, stir for 1 h - 2 h, then add aromatic diamine, stir for 1 h - 5 h to obtain a mixed solution. Add 4-phenylethynylphthalic anhydride to the mixed solution, stir and react for 1 h - 5 h, then add toluene, heat up to 120 °C - 130 °C, and under the condition of 120 °C - 130 °C, reflux and react for 1 h - 4 h to obtain a polyimide solution. After cooling the polyimide solution to room temperature, precipitate, filter, and dry to obtain polyimide resin;

[0018] The molar ratio of the aromatic dianhydride to the aromatic diamine is (0.95-0.98):1; the molar ratio of the aromatic diamine to 4-phenylethynylphthalic anhydride is 1:(0.04-0.1); and the total molar amount of the anhydride functional group of the aromatic dianhydride and the anhydride functional group of 4-phenylethynylphthalic anhydride is equal to the molar amount of the amino functional group of the aromatic diamine;

[0019] The aromatic dianhydride is

[0020] The aromatic diamine is

[0021] 2. Weigh 100 parts of polyimide resin, 2 to 5 parts of bonding enhancer, 2 to 15 parts of bonding low viscosity promoter, 100 to 200 parts of solvent and 0.1 to 10 parts of inorganic filler by weight, stir 100 parts of polyimide resin, 2 to 5 parts of bonding enhancer, 2 to 15 parts of bonding low viscosity promoter, 100 to 200 parts of solvent and 0.1 to 10 parts of inorganic filler at a temperature of 40 to 60°C and under stirring conditions for 10 to 30 minutes to obtain an adhesive.

[0022] The beneficial effects of the present invention are:

[0023] The polyimide of the present invention uses a combination of aromatic dianhydride containing ketocarbonyl and sulfone groups with strong electron-attracting and aromatic diamine containing ester and amide groups, so that the molecular chain can form a very strong intermolecular interaction force (CTC) with the adjacent molecular chain, unexpectedly achieving effective enhancement under the multi-level structural unit construction of the macro-micro interface of the polyimide composite material (such as under the action of long-range forces such as hydrogen bonds). Under the support of the thermosetting end group, it can also ensure that the Tg of the obtained polyimide exceeds 350°C, ensuring high temperature resistance.

[0024] Moreover, the introduction of other functional groups in the molecular chain is avoided, the molecular chain length is controlled, the spacing between the reaction end groups is controlled, and the increase in the interlayer spacing due to the introduction of twisted and non-coplanar structures is avoided, so as to achieve a more compact interaction force between the molecular chains, thereby obtaining a better interface bonding with the polyimide composite material.

[0025] In addition, an adhesive enhancer is introduced. Due to its amino property, stable condensation reaction covalent bonds can be formed on the surface of the polyimide composite prepreg with its carboxyl, hydroxyl, and anhydride groups. Considering that the reaction activity of aromatic main-chain diamine and aromatic dianhydride is much higher than that of aliphatic diamine, aromatic diamine is used as the adhesive enhancer. At the same time, it is unexpectedly found that using aromatic diamine with a melting point of 150 °C or below can better achieve the bonding effect with the composite material interface. This may be because the imidization temperature of polyimide is 150 °C - 250 °C, and monomers that can melt below the imidization temperature are more conducive to migrating from the adhesive to the adhesive / composite material interface, achieving better adhesive applicability.

[0026] In addition, an unexpected discovery is that a low-viscosity adhesive promoter with a bis-amine-terminated siloxane structure is additionally introduced into the adhesive enhancer. While controlling the molecular weight to be 800 - 2000, it can act synergistically with the adhesive enhancer. Utilizing its low viscosity and the reaction activity and polarity of having terminal bis-amino groups similar to aromatic diamine, it can achieve the effect of more conveniently transporting the adhesive enhancer to the composite material interface, thereby greatly improving the interface bonding effect. If the molecular weight is too low, it will be difficult to form a homogeneous system with the adhesive enhancer, resulting in phase separation and other situations. If the molecular weight is too high, the viscosity will be too high to achieve the interface transportation and bonding effect.

[0027] The present invention relates to a polyimide adhesive with good adhesion matching with composite materials and a preparation method thereof. Brief Description of the Drawings

[0028] Figure 1 It is a diagram of the adhesive interface of the polyimide composite material bonding part sheared at room temperature. a is Example 1, b is Example 2, c is Example 3, d is Example 4, e is Example 5, f is Example 6, g is Example 7;

[0029] Figure 2 It is the infiltration and interface adhesion effect of different polyimide adhesives on the surface of polyimide composite materials. a is Comparative Experiment 1, b is Example 2, c is Example 7;

[0030] Figure 3 It is the infrared spectrum of the polyimide resin prepared in Example 1. Detailed Description of the Invention

[0031] Detailed Description of the Invention 1: A polyimide adhesive with good adhesion matching with composite materials in this embodiment is prepared from 100 parts by weight of polyimide resin, 2 - 5 parts of adhesive enhancer, 2 - 15 parts of low-viscosity adhesive promoter, 0.1 - 10 parts of inorganic filler, and 100 - 200 parts of solvent;

[0032] The adhesive enhancer is aromatic diamine with a melting point ≤ 150 °C;

[0033] The low viscosity adhesive promoter is a diamino-terminated siloxane structure substance;

[0034] The inorganic filler is composed of metal oxide and graphite, and the mass ratio of the metal oxide to the graphite is 1:(0.1-1.0);

[0035] The general structural formula of the polyimide resin is:

[0036]

[0037] The n is 19 to 49;

[0038] The Ar1 is

[0039] The Ar2 is

[0040] The beneficial effects of this embodiment are:

[0041] The polyimide of this embodiment uses a combination of aromatic dianhydride containing ketocarbonyl and sulfone groups with strong electron-withdrawing and aromatic diamine containing ester and amide groups, so that its molecular chain can form a very strong intermolecular interaction force (CTC) with adjacent molecular chains, unexpectedly achieving effective enhancement under the multi-level structural unit construction of the macro-micro interface of the polyimide composite material (such as under the action of long-range forces such as hydrogen bonds). With the support of thermosetting end groups, it can also ensure that the Tg of the obtained polyimide exceeds 350°C, ensuring high temperature resistance.

[0042] Moreover, the introduction of other functional groups in the molecular chain is avoided, the molecular chain length is controlled, the spacing between the reaction end groups is controlled, and the increase in the interlayer spacing due to the introduction of twisted and non-coplanar structures is avoided, so as to achieve a more compact interaction force between the molecular chains, thereby obtaining a better interface bonding with the polyimide composite material.

[0043] In addition, the bonding enhancer is introduced, and its amino properties are used to form a stable condensation reaction covalent bond with its carboxyl, hydroxyl and anhydride groups on the surface of the polyimide composite prepreg. Considering that the reactivity of aromatic main chain diamine and aromatic dianhydride is much higher than that of aliphatic diamine, aromatic diamine is used as a bonding enhancer. At the same time, it was unexpectedly found that the use of aromatic diamine with a melting point of 150°C or below can better achieve the bonding effect with the composite interface. This may be because the imidization temperature of polyimide is 150°C-250°C, and the monomers that can melt below the imidization temperature are more conducive to migrating from the adhesive to the adhesive / composite interface, achieving better bonding applicability.

[0044] In addition, an unexpected discovery is that adding a bonding low-viscosity promoter with a bis(amino)-terminated siloxane structure to the bonding enhancer while controlling the molecular weight to be between 800 and 2000 can synergistically act with the bonding enhancer. Utilizing its low viscosity and the reaction activity and polarity of having terminal bis-amino groups similar to aromatic diamines, it can achieve the effect of more conveniently transporting the bonding enhancer to the composite material interface, thereby greatly enhancing the interfacial bonding effect. If the molecular weight is too low, it will be difficult to form a homogeneous system with the bonding enhancer, resulting in phase separation and other situations. If the molecular weight is too high, the viscosity will be too high to achieve the interface transportation and bonding effect.

[0045] Specific Embodiment 2: The difference between this embodiment and Specific Embodiment 1 is that the bonding enhancer is 1,3-bis(4'-aminophenoxy)benzene, 3,4'-diaminodiphenyl ether, or 4,4'-diamino-2,2'-dimethyl-1,1'-biphenyl. Others are the same as Specific Embodiment 1.

[0046] Specific Embodiment 3: The difference between this embodiment and one of Specific Embodiments 1 or 2 is that the bonding low-viscosity promoter is with a molecular weight of 800 - 2000. Others are the same as Specific Embodiment 1 or 2.

[0047] The bonding low-viscosity promoter described in this specific embodiment is such as DMS-A12 of GELEST.

[0048] Specific Embodiment 4: The difference between this embodiment and one of Specific Embodiments 1 to 3 is that the metal oxide is α-aluminum oxide, magnesium oxide, flaky aluminum oxide, spherical aluminum oxide, or nano-aluminum oxide. Others are the same as Specific Embodiments 1 to 3.

[0049] Specific Embodiment 5: The difference between this embodiment and one of Specific Embodiments 1 to 4 is that the graphite-like substance is one or a mixture of several of graphite, carbon black, graphene, and carbon nanotubes. Others are the same as Specific Embodiments 1 to 4.

[0050] Specific Embodiment 6: The difference between this embodiment and one of Specific Embodiments 1 to 5 is that the solvent is m-cresol or N-methylpyrrolidone. Others are the same as Specific Embodiments 1 to 5.

[0051] Specific Embodiment 7: The difference between this embodiment and one of Specific Embodiments 1 to 6 is that the particle size of the inorganic filler is 0.2 μm - 20 μm. Others are the same as Specific Embodiments 1 to 6.

[0052] Specific Embodiment 8: A preparation method of a polyimide adhesive with good bonding matching property with a composite material, which is carried out according to the following steps:

[0053] 1. Under a nitrogen atmosphere, an aromatic dianhydride is added to N,N-dimethylacetamide and stirred for 1 h to 2 h, then an aromatic diamine is added and stirred for 1 h to 5 h to obtain a mixed solution. 4-Phenylethynylphthalic anhydride is added to the mixed solution and stirred for reaction for 1 h to 5 h, then toluene is added and the temperature is raised to 120°C to 130°C. Under the condition of a temperature of 120°C to 130°C, reflux reaction is carried out for 1 h to 4 h to obtain a polyimide solution. After the polyimide solution is cooled to room temperature, it is precipitated, filtered and dried to obtain a polyimide resin;

[0054] The molar ratio of the aromatic dianhydride to the aromatic diamine is (0.95 to 0.98):1; the molar ratio of the aromatic diamine to 4-phenylethynylphthalic anhydride is 1:(0.04 to 0.1); and the total moles of the acid anhydride functional groups of the aromatic dianhydride and the acid anhydride functional groups of 4-phenylethynylphthalic anhydride are equal to the moles of the amino functional groups of the aromatic diamine;

[0055] The aromatic dianhydride is

[0056] The aromatic diamine is

[0057] 2. Weigh 100 parts of polyimide resin, 2 parts to 5 parts of bonding enhancer, 2 parts to 15 parts of bonding low-viscosity promoter, 100 parts to 200 parts of solvent and 0.1 part to 10 parts of inorganic filler by weight. Under the condition of a temperature of 40°C to 60°C and stirring, 100 parts of polyimide resin, 2 parts to 5 parts of bonding enhancer, 2 parts to 15 parts of bonding low-viscosity promoter, 100 parts to 200 parts of solvent and 0.1 part to 10 parts of inorganic filler are stirred for 10 min to 30 min to obtain an adhesive.

[0058] In this specific embodiment, the aromatic dianhydride is 3,3,4',4'-benzophenone tetracarboxylic dianhydride or 3,3,4',4'-diphenylsulfone tetracarboxylic dianhydride; the aromatic diamine is 4-aminophenyl 4-aminobenzoate (CAS No.: 20610-77-9) or 4,4'-diaminobenzanilide (CAS No.: 785-30-8).

[0059] Specific Embodiment 9: The difference between this embodiment and Specific Embodiment 8 is that: in Step 1, the mass ratio of N,N-dimethylacetamide to toluene is 1:(0.2 to 0.5); in Step 1, the total mass of N,N-dimethylacetamide and toluene and the total mass of 4-phenylethynylphthalic anhydride, aromatic dianhydride and aromatic diamine is (2 to 5):1. Others are the same as Specific Embodiment 8.

[0060] Embodiment 10: The difference between this embodiment and one of Embodiments 8 or 9 is that after the polyimide solution is cooled to room temperature in Step 1, it is dropped into distilled water, precipitated for 1 h to 2 h and then filtered, and finally dried at a temperature of 130 °C to 140 °C. Others are the same as those in Embodiment 8 or 9.

[0061] The following examples are used to verify the beneficial effects of the present invention:

[0062] Example 1:

[0063] A polyimide adhesive with good adhesion matching with composite materials, which is made of 100 parts by weight of polyimide resin, 5 parts of adhesion enhancer, 10 parts of adhesion low-viscosity promoter, 5 parts of inorganic filler and 100 parts of solvent;

[0064] The adhesion enhancer is 1,3-bis(4'-aminophenoxy)benzene;

[0065] The adhesion low-viscosity promoter is with a molecular weight of 1000;

[0066] The inorganic filler is composed of metal oxide and graphite-like substances, and the mass ratio of the metal oxide to the graphite-like substance is 1:0.4; the metal oxide is spherical alumina; the graphite-like substance is carbon nanotube;

[0067] The solvent is N-methylpyrrolidone;

[0068] The particle size of the inorganic filler is 4 μm;

[0069] The structural formula of the polyimide resin is:

[0070]

[0071] The n is 49;

[0072] The Ar1 is

[0073] The Ar2 is

[0074] The preparation method of the above polyimide adhesive with good adhesion matching with composite materials is carried out according to the following steps:

[0075] 1. Under a nitrogen atmosphere, add an aromatic dianhydride to N,N-dimethylacetamide, stir for 2 h, then add an aromatic diamine and stir for 5 h to obtain a mixed solution. Add 4-phenylethynylphthalic anhydride to the mixed solution, stir and react for 5 h, then add toluene, raise the temperature to 130 °C, and under the condition of 130 °C, reflux and react for 4 h to obtain a polyimide solution. After cooling the polyimide solution to room temperature, drop it into distilled water, carry out precipitation for 2 h and then filter, and finally dry it under the condition of 130 °C to obtain a polyimide resin;

[0076] The molar ratio of the aromatic dianhydride to the aromatic diamine is 0.98:1; the molar ratio of the aromatic diamine to 4-phenylethynylphthalic anhydride is 1:0.04; and the total moles of the acid anhydride functional groups of the aromatic dianhydride and the acid anhydride functional groups of 4-phenylethynylphthalic anhydride are equal to the moles of the amino functional groups of the aromatic diamine; the mass ratio of N,N-dimethylacetamide to toluene is 1:0.5; the total mass ratio of N,N-dimethylacetamide and toluene to the total mass of 4-phenylethynylphthalic anhydride, aromatic dianhydride and aromatic diamine is 2:1;

[0077] The aromatic dianhydride is

[0078] The aromatic diamine is

[0079] 2. Weigh 100 parts of polyimide resin, 5 parts of bonding enhancer, 10 parts of bonding low-viscosity promoter, 5 parts of inorganic filler and 100 parts of solvent by weight. Under the condition of 60 °C and stirring, stir 100 parts of polyimide resin, 5 parts of bonding enhancer, 10 parts of bonding low-viscosity promoter, 5 parts of inorganic filler and 100 parts of solvent for 30 min to obtain an adhesive.

[0080] Example 2: The difference between this example and Example 1 is that the bonding enhancer is 3,4'-diaminodiphenyl ether. Others are the same as in Example 1.

[0081] Example 3: The difference between this example and Example 1 is that the bonding enhancer is 4,4'-diamino-2,2'-dimethyl-1,1'-biphenyl. Others are the same as in Example 1.

[0082] Example 4: The difference between this example and Example 1 is that the metal oxide is α-aluminum oxide; the particle size of the inorganic filler is 3 μm. Others are the same as in Example 1.

[0083] Example 5: The difference between this example and Example 1 is that the aromatic dianhydride is The Ar1 is Others are the same as in Example 1.

[0084] Example 6: The difference between this example and Example 1 is that the aromatic diamine is The Ar2 is Others are the same as those in Example 1.

[0085] Example 7: The difference between this example and Example 1 is that the adhesive strength enhancer is 2 parts. Others are the same as those in Example 1.

[0086] Comparative Experiment 1: The difference between this example and Example 1 is that the adhesive strength enhancer is 2-(4-aminophenyl)-5-aminobenzimidazole (7621-86-5) with a melting point above 150 °C. Others are the same as those in Example 1.

[0087] Comparative Experiment 2: The difference between this example and Example 1 is that the adhesive low-viscosity promoter is the adhesive low-viscosity promoter DMS-A32R (from Gelest) with a high-viscosity bis-amine-terminated siloxane structure and a molecular weight of 30,000. Others are the same as those in Example 1.

[0088] Comparative Experiment 3: The difference between this example and Example 1 is that the aromatic dianhydride is 4,4'-oxybisphthalic anhydride (cas: 1823-59-2); the Ar1 is -O-. Others are the same as those in Example 1.

[0089] Comparative Experiment 4: The difference between this example and Example 1 is that the adhesive strength enhancer is 1 part. Others are the same as those in Example 1.

[0090] The polyimide adhesives prepared in Examples 1 to 7 and Comparative Experiments 1 to 4 were placed between polyimide composite prepregs (T700 grade carbon fiber, 12K, the fiber was from Jiangsu Hengshen Co., Ltd.; the polyimide resin was polymerized from 3,3',4,4'-biphenyltetracarboxylic dianhydride and 2,2'-bis(trifluoromethyl)-(1,1'-biphenyl)-4,4'-diamine, and the end-capping agent was 4-phenylethynylphthalic anhydride with a molecular weight of 2500) for bonding. The curing process was as follows: First, heat at a temperature of 80 °C and a pressure of 0.2 MPa for 1 h, then heat at a temperature of 150 °C and a pressure of 0.2 MPa for 1 h, then heat at a temperature of 250 °C and a pressure of 0.2 MPa for 1 h, and finally heat at a temperature of 350 °C and a pressure of 0.5 MPa for 4 h to obtain polyimide composite bonded parts. Various performance tests were carried out on the polyimide composite bonded parts, and the test conditions were referred to the following standards (methods):

[0091] 1. Shear strength: The tensile shear strength of the adhesive is measured according to GB / T7124-2008; the high-temperature tensile shear strength of the adhesive is measured according to GJB444-1988. The specific room-temperature shear strength after high and low temperature cycling is as follows: Under the condition that the heating and cooling rates are both 20°C / min, cycle 500 times between -55°C and 300°C, and then test the room-temperature shear strength.

[0092] 2. Flat tensile test: The test method for tensile properties of oriented fiber-reinforced polymer matrix composites is adopted in accordance with GB / T 3354-2014.

[0093] 3. For the interfacial bonding effect with the polyimide composite material, after cutting, observe whether there are obvious voids and defects between layers, and observe whether there is any situation such as drum hollowing.

[0094] Table 1

[0095]

[0096]

[0097] Figure 1 It is the diagram of the bonding interface of the polyimide composite material bonding part sheared at room temperature. a is Example 1, b is Example 2, c is Example 3, d is Example 4, e is Example 5, f is Example 6, g is Example 7; It can be seen from the figure that the bonding interface is the failure of the adhesive layer.

[0098] Figure 2 It is the infiltration and interfacial adhesion effect of different polyimide adhesives on the surface of the polyimide composite material. a is Comparative Experiment 1, b is Example 2, c is Example 7; It can be seen from the figure that in Comparative Experiment 1, the polyimide adhesive has poor infiltration on the imide composite material, and the contact angle is 80°. In Example 1 and Example 7, the contact angles on the polyimide composite material are small, the contact angles are 60° and 45°, and the infiltration is good, indicating the effect brought by the bonding enhancer and the low-viscosity promoter.

[0099] Figure 3 It is the infrared spectrum of the polyimide resin prepared in Example 1; It can be seen from the figure that at 1778 cm -1 there is complete imidization, which is the polyimide resin. At 1120 cm -1 ~1160 cm -1 is the antisymmetric stretching vibration absorption band of the sulfone group (-SO2-), which proves the presence of the sulfone group monomer. Therefore, it can prove the successful preparation of the polyimide resin in Example 1.

Claims

1. A polyimide adhesive with good adhesion matching for composite materials, characterized in that It is made of 100 parts by weight of polyimide resin, 2 to 5 parts of bonding enhancer, 2 to 15 parts of bonding low-viscosity promoter, 0.1 to 10 parts of inorganic filler and 100 to 200 parts of solvent; The bonding enhancer is an aromatic diamine with a melting point ≤ 150 °C; The described adhesive low-viscosity promoter is , with a molecular weight of 800 to 2000; The inorganic filler consists of metal oxides and graphite-like substances, and the mass ratio of the metal oxides to the graphite-like substances is 1:(0.1 - 1.0); the graphite-like substances are one or a mixture of several of graphite, carbon black, graphene and carbon nanotubes; The structural general formula of the polyimide resin is: ； The n is 19 - 49; The described Ar1 is or ; The aforementioned Ar2 is or .

2. The polyimide adhesive with good adhesion matching property to the composite material according to claim 1, wherein The bonding enhancer is 1,3-bis(4'-aminophenoxy)benzene, 3,4'-diaminodiphenyl ether or 4,4’-diamino-2,2’-dimethyl-1,1’-biphenyl.

3. The polyimide adhesive with good adhesion matching with the composite material according to claim 1, characterized in that The metal oxides are α-aluminum oxide, magnesium oxide, flaky alumina, spherical alumina or nano-alumina.

4. The polyimide adhesive with good adhesion matching property with the composite material according to claim 1, characterized in that The solvent is m-cresol or N-methylpyrrolidone.

5. The polyimide adhesive with good adhesion matching with the composite material according to claim 1, characterized in that The particle size of the inorganic filler is 0.2 μm - 20 μm.

6. The preparation method of a polyimide adhesive with good adhesion matching with composite materials as described in claim 1, characterized in that It is carried out according to the following steps: I. Under a nitrogen atmosphere, add aromatic dianhydride to N,N-dimethylacetamide, stir for 1 h - 2 h, then add aromatic diamine and stir for 1 h - 5 h to obtain a mixed solution. Add 4-phenylethynylphthalic anhydride to the mixed solution, stir and react for 1 h - 5 h, then add toluene, heat up to 120 °C - 130 °C, and under the condition of 120 °C - 130 °C, reflux and react for 1 h - 4 h to obtain a polyimide solution. After cooling the polyimide solution to room temperature, precipitate, filter and dry to obtain polyimide resin; The molar ratio of the aromatic dianhydride to the aromatic diamine is (0.95 - 0.98):1; the molar ratio of the aromatic diamine to 4-phenylethynylphthalic anhydride is 1:(0.04 - 0.1); and the total molar amount of the acid anhydride functional groups of the aromatic dianhydride and 4-phenylethynylphthalic anhydride is equal to the molar amount of the amino functional groups of the aromatic diamine; The aromatic dianhydride described is or ; The aromatic diamine described is or ; II. Weigh 100 parts by weight of polyimide resin, 2 to 5 parts of bonding enhancer, 2 to 15 parts of bonding low-viscosity promoter, 100 to 200 parts of solvent and 0.1 to 10 parts of inorganic filler. Under the conditions of a temperature of 40 °C - 60 °C and stirring, stir 100 parts by weight of polyimide resin, 2 to 5 parts of bonding enhancer, 2 to 15 parts of bonding low-viscosity promoter, 100 to 200 parts of solvent and 0.1 to 10 parts of inorganic filler for 10 min - 30 min to obtain an adhesive.

7. The preparation method of a polyimide adhesive with good adhesion matching with composite materials according to claim 6, characterized in that In step I, the mass ratio of N,N-dimethylacetamide to toluene is 1:(0.2 - 0.5); the mass ratio of the total mass of N,N-dimethylacetamide and toluene to the total mass of 4-phenylethynylphthalic anhydride, aromatic dianhydride and aromatic diamine is (2 - 5):

1.

8. The preparation method of a polyimide adhesive with good adhesion matching with composite materials according to claim 6, characterized in that After cooling the polyimide solution to room temperature in step I, it is dropped into distilled water, precipitated for 1 h - 2 h and then filtered, and finally dried under the condition of a temperature of 130 °C - 140 °C.

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