Polyimide composite material and preparation method thereof

Abstract

The invention discloses a polyimide composite material and a preparation method thereof, and relates to the technical field of functional composites.The polyimide composite material is composed of hollow quartz fibers and silicon-containing polyimide resin, the fiber volume content of the polyimide composite material is 45%-60%, and the density of the polyimide composite material is 1.25-1.55 g / cm < 2 >; wherein the silicon-containing polyimide resin is formed by polymerizing a mixture of aromatic dianhydride, aromatic diamine and diamine containing a siloxane structure, and an end-capping reagent. The preparation method comprises the following steps: synthesizing a polyamide acid solution, preparing a prepreg by preimpregnation, performing by a vacuum bag method, performing hot-pressing curing and performing high-temperature post-treatment. Through collaborative innovation of the components and the process, the preparation method is simple, and the composite material has ultralow density, ultrahigh heat resistance, low dielectric constant and high strength and is suitable for the fields of aerospace, 5G communication, semiconductors and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of functional composite materials, in particular to a polyimide composite material and a preparation method thereof. BACKGROUND

[0002] In the field of aerospace, supersonic aircraft and its radome, antenna cover and other components are faced with severe aerodynamic heat environment, and the material must have extremely high heat resistance (such as glass transition temperature greater than 500℃), excellent wave transmission (low dielectric constant and dielectric loss) and extreme light weight (low density) to reduce the weight of the structure. Although the traditional quartz fiber / cyanate or ordinary polyimide (PI) system has certain wave transmission, its upper limit of heat resistance often cannot meet the requirements of the new generation of supersonic aircraft.

[0003] In the field of 5G communication, high-frequency high-speed signal transmission requires that the substrate material has extremely low dielectric constant (Dk) and dielectric loss (Df) to reduce signal delay, attenuation and interference. At the same time, the high integration and miniaturization of components make the working heat increase sharply, and the material needs to have good heat resistance reliability. Although the existing PTFE, PPO and other high-frequency substrate materials have excellent dielectric properties, they often have problems such as insufficient heat resistance, poor mechanical strength, and weak bonding force with copper foil.

[0004] In the field of semiconductors, especially in advanced packaging and chip manufacturing, the material needs to withstand the high-temperature process in the back-end process (such as reflow soldering, multiple annealing), so the heat resistance (thermal decomposition temperature) is extremely high. At the same time, in order to reduce the signal crosstalk and capacitance delay between interconnection lines, the demand for low dielectric constant materials for interlayer, packaging substrate and other components is increasingly urgent. The commonly used epoxy encapsulating material (EMC), polyester material and other materials have gradually been difficult to meet the development needs in terms of comprehensive performance of dielectric properties and heat resistance.

[0005] Chinese patent publication No. CN110746780A discloses an invention patent application entitled "A light high-strength heat-insulating wave-transparent composite material and a preparation method thereof" on February 4, 2020, which uses hollow quartz fiber as a reinforcing body, organic silicone resin as a matrix, and aerogel powder as an additive to prepare a resin-based wave-transparent composite material by hot pressing. However, the heat resistance and mechanical strength of the organic silicone resin matrix limit its application in extreme high-temperature structural parts.

[0006] Therefore, whether in the fields of aerospace, 5G communication or semiconductor, it is urgent to develop a material that can simultaneously have ultra-light weight, ultra-high strength, ultra-high heat resistance and low dielectric constant to solve the performance bottleneck of "trade-off" in the prior art. SUMMARY

[0007] The polyimide composite material and the preparation method thereof provided by the application have the characteristics of low density, high heat resistance, excellent dielectric performance and good mechanical properties.

[0008] The object of the application is mainly achieved by the following technical solutions. The polyimide composite material preparation method comprises the following steps: Step S1, synthesis of polyimide oligomer precursor: under the protection of inert atmosphere, aromatic diamine and siloxane structure-containing diamine monomer are dissolved in an organic solvent, aromatic dianhydride monomer is added after complete dissolution, reaction is carried out at room temperature for 2-4 hours, a capping agent is added, and stirring is carried out for 3-5 hours to obtain a polyamide acid solution; wherein the mixture of the aromatic dianhydride, the aromatic diamine and the siloxane structure-containing diamine monomer, and the capping agent has a feeding molar ratio of n:(n+1):2, n=1-8; the mass concentration of the organic solvent solution is 25%-65%; Step S2, solution method for preparing a prepreg: hollow quartz fibers are used to impregnate the polyamide acid solution and air-dried at room temperature to obtain a prepreg with a resin content of 30%-50%; wherein the hollow degree of the hollow quartz fibers is 32%-50%; Step S3, preforming of the prepreg: the prepreg is cut and laid according to the set size and angle to obtain a preblank, and the preblank is preformed by a vacuum bag method in an oven to obtain a preformed laminated blank; Step S4, hot-pressing forming and curing: the preformed laminated blank is subjected to hot-pressing curing treatment to obtain a polyimide composite laminated plate; Step S5, post-processing: the polyimide composite blank is subjected to heat treatment to obtain a polyimide composite material.

[0009] Further, in the step S3, the preblank is preformed by a vacuum bag method in a programmed temperature rising manner, the programmed temperature rising process is as follows: rising to 85℃±5℃ and keeping for 60min, continuously rising to 110℃±5℃ and keeping for 60min-120min, and continuously rising to 150℃±5℃ and keeping for 60min-180min to complete preforming, thereby obtaining a preformed laminated blank; wherein the temperature rising rate is 1-2℃ / min each time.

[0010] Further, in the step S3, the preblank is loaded into a vacuum bag, vacuum is drawn in an oven, and the vacuum degree is not less than 0.085 MPa.

[0011] Furthermore, in step S4, the preformed laminate blank is cured in a hot press or autoclave, and a pressure of 1 to 4 MPa is applied when the temperature is raised to 290℃~320℃. Then, the temperature is raised to 385℃±5℃ and held for 300±10 min for hot pressing. After cooling, a polyimide composite laminate is obtained. The heating rate is 1~2℃ / min for each heating.

[0012] Furthermore, in step S5, the heat treatment is carried out at 420℃~450℃ for 60~180min.

[0013] Furthermore, the organic solvent is any one or any combination of two or more of N-methylpyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, dimethyl sulfoxide, chloroform, dichloromethane, and dioxane.

[0014] Furthermore, the aromatic diamine may be p-phenylenediamine, m-phenylenediamine, 4,4'-diaminobiphenyl, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenylmethane, 2,2'-dimethyl-4,4'-diaminobiphenyl, 3,3'-dimethyl-4,4'-diaminobiphenyl, 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl, 2,2'-bis(trifluoromethyl)-4,4'-diaminodiphenyl ether, 4,4'-diaminobenzophenone, 2,2'-bis(4-aminophenyl)hexafluoropropane, 1,3-bis(4-aminophenoxy)benzene, 1,3-bis... (3-aminophenoxy)benzene, 1,4-bis(4-aminophenoxy)benzene, 1,4-bis(2-trifluoromethyl-4-aminophenoxy)benzene, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 9,9-bis(4-aminophenyl)fluorene (BAFL), 9,9-bis(3-fluoro-4-aminophenyl)fluorene (FFDA), 9,9-bis[4-(4-aminophenoxy)phenyl]fluorene (BAOFL), 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane, 3,3'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl sulfone, or any combination of two or more of these.

[0015] Furthermore, the aromatic dianhydride is selected from the following: pyromellitic dianhydride (PMDA), 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), 4,4'-oxobisphthalic anhydride (ODPA), 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BTDA), 3,3',4,4'-diphenyl sulfone tetracarboxylic dianhydride (DSDA), 5,5'-(propane-2,2-diyl)bis(isobenzofuran-1,3-dione), 2,3,3',4'-benzophenone tetracarboxylic dianhydride (α-BTDA), and 2,3,3',4'-diphenyl ether tetracarboxylic dianhydride (α-ODPA). 3,3',4,4'-Diphenyl ether tetracarboxylic dianhydride (ODPA), 2,3,3',4'-Diphenyl sulfide tetracarboxylic dianhydride (α-TDPA), 1,2,3,4-Cyclobutanetetracarboxylic dianhydride (CBDA), 1,2,3,4-Cyclopentanetetracarboxylic dianhydride (CPDA), 1,2,4,5-Cyclohexanetetracarboxylic dianhydride (HPMDA), 2,3,5-Tricarboxycyclopentylacetic acid dianhydride, Bicyclo[2.2.1]hepta-2,3,5, The dianhydride is any one or any combination of two or more of the following: 6-tetracarboxylic acid dianhydride, 3,4,6-tricarboxylic bicyclo[2.2.2]heptylacetic acid dianhydride, bicyclo[2.2.2]oct-2,3,5,6-tetracarboxylic acid dianhydride, bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic acid dianhydride, decahydrobiphenyl-3,3',4,4'-tetracarboxylic acid dianhydride, and decahydro-1,4,5,8-dimethylenenaphthalene-2,3,6,7-tetracarboxylic acid dianhydride.

[0016] Furthermore, the diamine containing the siloxane structure is any one or any combination of two or more of the following: 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane (SIDA), bis(4-aminophenoxy)tetramethyldisiloxane (p-TMDS), bis(3-aminophenoxy)tetramethyldisiloxane (m-TMDS), bis(4-aminophenoxy)dimethyl-1,3-diphenyldisiloxane (DPDS), bis(4-aminophenoxy)dimethylsilane (APDS), and bis(4-aminophenoxy)methylphenylsilane (PMPS).

[0017] Furthermore, the capping agent is any one of 4-phenylethynyl phthalic anhydride and 3-phenylethynyl phthalic anhydride, or a combination of both.

[0018] The polyimide composite material prepared by the above-mentioned method is composed of hollow quartz fibers and silicon-containing polyimide resin. The fiber volume content of the polyimide composite material is 45%-60%, and the density of the polyimide composite material is 1.25-1.55 g / cm³. The silicon-containing polyimide resin is polymerized from a mixture of aromatic dianhydride, aromatic diamine and diamine containing siloxane structure, and an end-capping agent.

[0019] This invention addresses the rapid development of aerospace technology, low-altitude aircraft, and the high-speed advancements in 5G communication and semiconductor industries, which demand heat-resistant, lightweight, and low-dielectric composite materials. It proposes a polyimide composite material and its preparation method. The method utilizes hollow quartz fibers and a high-temperature resistant, low-dielectric polyimide resin. A solution prepreg is used to obtain a prepreg, which is then pre-formed in an oven using a vacuum bag method. Finally, it is hot-pressed and cured to obtain a high-temperature resistant, ultra-lightweight, low-dielectric polyimide composite material part. The high-temperature resistant, ultra-lightweight, low-dielectric polyimide composite material obtained by this invention features low density, high temperature resistance, high glass transition temperature and thermal decomposition temperature, high carbon residue at high temperatures, low dielectric constant, and excellent thermal insulation properties. The preparation method is simple and suitable for high-temperature resistant electrical insulation materials with weight reduction requirements, supersonic aircraft radomes, and other aerospace and weaponry fields, as well as 5G communication and semiconductor fields.

[0020] In summary, the present invention has the following advantages compared with the prior art: (1) The present invention selects hollow quartz fibers with a specific degree of hollowness (32%-50%) and optimizes their matching with resin, thereby achieving ultra-low density (1.25-1.55 g / cm³) of the material while maintaining high fiber volume content, and with excellent mechanical strength.

[0021] (2) This invention introduces diamines containing siloxane structures into polyimide resin through molecular design to improve processability and toughness, introduces aromatic diamines to improve rigidity and thermal stability, and uses end-capping agents for crosslinking to control molecular weight and crosslinking density, so that the glass transition temperature of the composite material reaches about 480°C after curing, and can reach 600°C or above after post-treatment, with extremely excellent heat resistance.

[0022] (3) The “air cavity” effect of the hollow quartz fiber of the present invention, as well as the introduction of aromatic diamine and diamine containing siloxane structure, synergistically endow the material with an extremely low dielectric constant, which meets the requirements of high frequency and high speed signal transmission.

[0023] (4) In view of the characteristics of hollow fibers being easily crushed, the viscosity and reactivity of the resin system, the pre-impregnation, pre-forming (vacuum bag method step heating to remove solvent), curing and post-treatment processes were optimized, which effectively ensured the full wetting of the fiber by the resin, the extremely low porosity and the integrity of the hollow structure, thereby realizing the stable preparation of high-performance products.

[0024] (5) The preparation method of the present invention is simple and easy to implement. The prepared polyimide composite material has excellent characteristics such as low density, high temperature resistance, high glass transition temperature and low dielectric constant, which are suitable for the material needs of aerospace, 5G communication, semiconductor and other fields. Attached Figure Description

[0025] The accompanying drawings, which are included to provide a further understanding of embodiments of the invention and form part of this application, do not constitute a limitation thereof. In the drawings: Figure 1 This is a process flow diagram of the preparation method of the present invention. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments and accompanying drawings. The illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention.

[0027] like Figure 1 As shown, a method for preparing a polyimide composite material includes the following steps: Step S1, synthesis of polyimide oligomer precursor: Under an inert atmosphere, an aromatic diamine and a diamine monomer containing a siloxane structure are dissolved in an organic solvent. After complete dissolution, an aromatic dianhydride monomer is added, and the reaction is carried out at room temperature for 2-4 hours. Then, a capping agent is added, and the mixture is stirred for 3-5 hours to obtain a polyamic acid solution. The molar ratio of the mixture of aromatic dianhydride, aromatic diamine, and diamine monomer containing a siloxane structure, to the capping agent is n:(n+1):2, where n=1-8. The mass concentration of the organic solvent solution is 25%-65%. The inert atmosphere used in this invention is a chemical inert gas such as nitrogen, argon, or helium, or a mixture thereof. Nitrogen is preferred due to its low cost. The synthesis of the polyimide oligomer precursor of this invention is carried out in a reaction vessel equipped with a mechanical stirrer.

[0028] This invention involves reacting n moles of aromatic dianhydride with n+1 moles of diamine to generate a prepolymer with amine groups at both ends, followed by end-capping with 2 moles of end-capping agent to obtain the prepolymer. This invention allows for precise control of the prepolymer's molecular weight by controlling the value of n (1~8). Thus, the synthesis process of the polyimide oligomer precursor of this invention produces a soluble polyimide prepolymer with controllable molecular weight and active end groups, serving as the basis for subsequent impregnation processes. This invention controls the molecular weight through the end-capping agent, ensuring the resin has a low melt viscosity during the prepreg stage, facilitating the impregnation of hollow quartz fibers. The polyamic acid stage is soluble in organic solvents, facilitating the preparation of prepregs. The end-capping agent undergoes an addition reaction during high-temperature curing, forming a three-dimensional cross-linked network, thereby endowing the cured product with extremely high heat resistance and mechanical properties. The synthesis of polyamic acid is an exothermic reaction; the synthesis process of the polyimide oligomer precursor of this invention, carried out at room temperature, avoids localized overheating, preventing excessively wide molecular weight distribution or partial imidization leading to solution gelation. In practical implementation of this invention, a reaction time that is too short can easily lead to incomplete reaction, while a reaction time that is too long may result in molecular chain degradation or unstable viscosity. To balance production efficiency and ensure sufficient reaction, this invention sets the reaction time between aromatic dianhydrides and diamines to 2–4 hours, and after adding the capping agent, the reaction time is set to 3–5 hours. Solid content directly affects solution viscosity; if the viscosity is too low, the resin cannot adhere during pre-impregnation; if the viscosity is too high, the fiber cannot be fully wetted. To ensure sufficient resin content while providing a suitable viscosity for process operation, this invention sets the mass concentration of the organic solvent solution to 25%–65%.

[0029] Step S2: Solution impregnation method for prepreg preparation: Hollow quartz fibers are impregnated with a polyamic acid solution and dried at room temperature to obtain a prepreg with a resin content of 30%–50%. The outer diameter of the single filament of the hollow quartz fiber is 5–15 μm, and the hollowness of the hollow quartz fiber is 32%–50%. This invention uses a solution impregnation method to prepare the prepreg. In specific implementation, a roller method is used to wind the reinforcing material, hollow quartz fibers, parallel to each other onto a metal cylinder, then impregnate it in a polyamic acid solution in an impregnation tank. After drying the solvent, the prepreg is cut along the generatrix to obtain the prepreg. The prepreg of this invention has a length of 5.5 meters and a width of 0.3–1 meter, and can be made into different widths according to requirements.

[0030] In this invention, a polyamic acid solution is uniformly and thoroughly coated and impregnated onto hollow quartz fibers to create a prepreg blank that facilitates subsequent lay-up. This invention employs a solution prepreg method, enabling continuous production with high efficiency and precise control of resin content. The prepreg is air-dried at room temperature, evaporating most of the solvent while retaining some volatile components, maintaining a certain level of viscosity and softness for easy cutting and laying without brittleness. If the resin content is too low, the fibers cannot be completely encapsulated, resulting in numerous internal defects and poor mechanical properties in the composite material; if the content is too high, it affects the mechanical properties of the composite material and increases its specific gravity and dielectric constant, failing to achieve the goals of "ultra-lightweight" and "low dielectric." Based on repeated experiments, this invention sets the resin content to 30%–50%. The hollowness of the hollow quartz fibers is crucial for lightweighting; too low a hollowness results in insignificant weight reduction, while too high a hollowness leads to excessively thin fiber walls, making them easily crushed during prepreg and compression molding, thus losing their reinforcing function. To ensure lightweight and fiber structure integrity, the hollowness of the hollow quartz fiber is set to 32% to 50%.

[0031] Step S3: Prepreg Preforming: The prepreg is cut and laid according to the set dimensions and angles to obtain a preform. The preform is then preformed in an oven using a vacuum bag method to obtain a preformed laminated blank. In specific implementation of this invention, the prepreg is dried at room temperature and relative humidity <50% until the volatile content reaches below 15% before cutting. This invention uses a vacuum bag method for preforming the preform using a programmed temperature rise process. The programmed temperature rise process is as follows: heat to 85℃±5℃ and hold for 60 min, continue heating to 110℃±5℃ and hold for 60 min~120 min, then continue heating to 150℃±5℃ and hold for 60 min~180 min to complete the preforming and obtain the preformed laminated blank; wherein, the heating rate during each heating is 1~2℃ / min. In a specific implementation of the present invention, step S3 involves loading the pre-formed material into a vacuum bag, evacuating it in an oven to a vacuum level of not less than 0.085 MPa, and then proceeding with programmed heating.

[0032] This invention utilizes a prepreg preforming process to initially remove residual solvent, allowing the laid prepreg layers to initially bond into a single unit. The invention employs a stepped heating method: gently and gradually removing solvents with different boiling points, avoiding defects such as bubbles and delamination caused by rapid solvent evaporation. The use of a vacuum bag method, operating under negative pressure, effectively extracts residual air and evaporating solvent from between layers, significantly reducing the porosity of the final product. The preform obtained after this invention is a rigid blank: easy to remove from the mold and transfer to a hot press for high-temperature, high-pressure curing, improving production flexibility and efficiency. The insulation temperature point of this invention is set based on the azeotropic and volatile characteristics of the solvent used. Gradually increasing the temperature allows the solvent to escape smoothly and completely, rather than boiling violently. 150℃ is far below the resin's curing initiation temperature, ensuring that only physical changes (solvent evaporation) occur at this stage, without chemical changes. In specific implementations, the vacuum degree is not less than 0.085 MPa to remove most of the gas in the system, providing impetus for solvent evaporation and suppressing bubble formation.

[0033] Step S4, Hot Pressing and Curing: The pre-formed laminate blank is hot-pressed and cured to obtain a polyimide composite laminate. In a specific implementation of this invention, the pre-formed laminate blank is cured in a hot press or autoclave. When the temperature is raised to 290℃~320℃, a pressure of 1~4MPa is applied, and then the temperature is further raised to 385℃±5℃ and held for 300±10min for hot pressing. After cooling, a polyimide composite laminate is obtained; wherein, the heating rate is 1~2℃ / min for each heating.

[0034] This invention utilizes a hot-pressing curing process to induce imidization and cyclization reactions in the prepolymer under high temperature and pressure, ultimately forming a three-dimensional network structure through the cross-linking reaction of end-capping groups, achieving complete curing. The hot-pressing curing process of this invention is carried out at high temperature, providing the activation energy required for the cyclization and cross-linking reactions. The purpose of pressurization is to: ensure close contact between the layers of prepreg; inhibit resin decomposition and the vaporization of small molecule byproducts, preventing the formation of pores; and counteract the internal pressure of the hollow fibers, preventing them from being burst or crushed by internal gases under high heat. This invention applies pressure at 290℃ to 320℃. Within this temperature range, the resin viscosity reaches a minimum point (before the gel point), resulting in optimal flowability. At this temperature, the resin can flow uniformly and fully wet the fibers while effectively suppressing air bubbles. If the temperature is too low (<290℃), the resin viscosity is too high, and pressure cannot effectively facilitate flow; if the temperature is too high (>320℃), the resin has already begun rapid cross-linking, and the viscosity rises sharply (geling). At this point, pressurization is too late to eliminate defects. The final curing temperature of this invention is 385℃±5℃ and held for 300±10min to ensure that the end-capping agent can fully and completely undergo cross-linking reaction. This temperature and time were optimized through a large number of experiments and are sufficient to achieve high conversion rate, thereby obtaining the highest glass transition temperature and the best mechanical properties.

[0035] Step S5, Post-treatment: The polyimide composite preform is heat-treated to obtain the polyimide composite material. Specifically, the heat treatment in this invention is performed at 420℃~450℃ for 60~180 min.

[0036] This invention involves heat-treating a cured composite material under high temperature and pressureless conditions to remove any trace amounts of small molecules that may remain in the system and promote further orientation and compact packing of molecular chains. This improves the material's density and performance stability: eliminating internal stress and making the material more stable. The glass transition temperature after treatment can be significantly increased from around 480℃ to 600℃ and above. The heat treatment temperature of this invention is set at 420℃~450℃, which is higher than the curing temperature (385℃) but lower than the resin's decomposition temperature. This temperature provides sufficient energy for molecular chain movement, enabling it to reach a more stable thermodynamic state without causing material degradation. The heat treatment time is coordinated with the temperature; higher temperatures require shorter times, while lower temperatures require longer times to achieve the same effect.

[0037] The organic solvent of the present invention is any one or any combination of two or more of N-methylpyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, dimethyl sulfoxide, chloroform, dichloromethane, and dioxane. The aromatic diamines of this invention are p-phenylenediamine, m-phenylenediamine, 4,4'-diaminobiphenyl, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenylmethane, 2,2'-dimethyl-4,4'-diaminobiphenyl, 3,3'-dimethyl-4,4'-diaminobiphenyl, 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl, 2,2'-bis(trifluoromethyl)-4,4'-diaminodiphenyl ether, 4,4'-diaminobenzophenone, 2,2'-bis(4-aminophenyl)hexafluoropropane, 1,3-bis(4-aminophenoxy)benzene, 1,3-bis( 3-Aminophenoxy)benzene, 1,4-bis(4-aminophenoxy)benzene, 1,4-bis(2-trifluoromethyl-4-aminophenoxy)benzene, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 9,9-bis(4-aminophenyl)fluorene (BAFL), 9,9-bis(3-fluoro-4-aminophenyl)fluorene (FFDA), 9,9-bis[4-(4-aminophenoxy)phenyl]fluorene (BAOFL), 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane, 3,3'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl sulfone, any one or any combination of two or more of these.The aromatic dianhydrides of this invention are pyromellitic dianhydride (PMDA), 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), 4,4'-oxobisphthalic anhydride (ODPA), 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BTDA), 3,3',4,4'-diphenyl sulfone tetracarboxylic dianhydride (DSDA), 5,5'-(propane-2,2-diyl)bis(isobenzofuran-1,3-dione), 2,3,3',4'-benzophenone tetracarboxylic dianhydride (α-BTDA), and 2,3,3',4'-diphenyl ether tetracarboxylic dianhydride (α-ODPA). 3,3',4,4'-Diphenyl ether tetracarboxylic dianhydride (ODPA), 2,3,3',4'-Diphenyl sulfide tetracarboxylic dianhydride (α-TDPA), 1,2,3,4-Cyclobutanetetracarboxylic dianhydride (CBDA), 1,2,3,4-Cyclopentanetetracarboxylic dianhydride (CPDA), 1,2,4,5-Cyclohexanetetracarboxylic dianhydride (HPMDA), 2,3,5-Tricarboxycyclopentylacetic acid dianhydride, Bicyclo[2.2.1]hepta-2,3,5, The dianhydride is any one or any combination of two or more of the following: 6-tetracarboxylic acid dianhydride, 3,4,6-tricarboxylic bicyclo[2.2.2]heptylacetic acid dianhydride, bicyclo[2.2.2]oct-2,3,5,6-tetracarboxylic acid dianhydride, bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic acid dianhydride, decahydrobiphenyl-3,3',4,4'-tetracarboxylic acid dianhydride, and decahydro-1,4,5,8-dimethylenenaphthalene-2,3,6,7-tetracarboxylic acid dianhydride. The diamine containing a siloxane structure of the present invention is any one or a combination of two or more of the following: 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane (SIDA), bis(4-aminophenoxy)tetramethyldisiloxane (p-TMDS), bis(3-aminophenoxy)tetramethyldisiloxane (m-TMDS), bis(4-aminophenoxy)dimethyl-1,3-diphenyldisiloxane (DPDS), bis(4-aminophenoxy)dimethylsilane (APDS), and bis(4-aminophenoxy)methylphenylsilane (PMPS). The end-capping agent of the present invention is any one or a combination of two or more of the following: 4-phenylethynylphthalic anhydride and 3-phenylethynylphthalic anhydride.

[0038] The polyimide composite material prepared using the above-described method comprises hollow quartz fibers and a silicon-containing polyimide resin. The fiber volume content of the polyimide composite material is 45%-60%, and the density is 1.25-1.55 g / cm³. The silicon-containing polyimide resin is polymerized from a mixture of aromatic dianhydride, aromatic diamine, and diamine containing a siloxane structure, along with a capping agent. The polyimide composite material prepared by this invention has a glass transition temperature greater than 480℃, and after post-treatment at 420℃~450℃, it exceeds 600℃.

[0039] Example 1: A method for preparing a polyimide composite material includes the following steps: Step S1, Synthesis of polyimide oligomer precursor: In a 300 ml three-necked flask equipped with a mechanical stirrer and a nitrogen inlet, 0.068 mol (23.556 g) of 9,9-bis(4-aminophenyl)fluorene (BAFL) and 0.159 mol (43.605 g) of bis(4-aminophenoxy)dimethylsilane (APDS) were dissolved in 331.734 g of N-methylpyrrolidone. Under nitrogen protection, the solution was stirred at room temperature to dissolve. After dissolution, 0.201 mol (62.352 g) of 3,3',4,4'-diphenyl ether tetracarboxylic dianhydride (ODPA) was gradually added. The mixture was stirred at room temperature for 4 h. After the reaction was completed, 0.051 mol (12.659 g) of 4-phenylethynylphthalic anhydride was gradually added to the solution. The mixture was stirred at room temperature for 3 h to obtain a polyamic acid solution with a solid content of 30%.

[0040] Step S2: Solution method for preparing prepreg: Hollow quartz fibers are impregnated with polyamic acid solution and dried at room temperature to obtain a prepreg with a resin content of 38%. The prepreg is 5.5 meters long and 1 meter wide. The hollowness of the hollow quartz fibers is 41%.

[0041] Step S3: Prepreg Preforming: The prepreg is air-dried at room temperature until the volatile content reaches below 15%. It is then cut to the set dimensions and angles, laid out, and a preform is obtained. The preform is placed in a vacuum bag and placed in an oven under vacuum (no less than 0.085 MPa). The temperature is increased to 85°C at a rate of 1°C / min and held for 60 minutes. The temperature is then increased to 110°C and held for 120 minutes. Finally, the temperature is increased to 150°C and held for 120 minutes to complete the preforming process, resulting in a preformed laminate.

[0042] Step S4, Hot Pressing and Curing: The pre-formed laminate blank obtained in Step S3 is cured in a hot press or autoclave. The temperature is raised to 290℃ and pressure is applied at 290℃ to a pressure of 4MPa. The temperature is then raised to 385℃ and held at 385℃ for 300 minutes for hot pressing. After cooling, a polyimide composite laminate is obtained. The heating rate is 1℃ / min for each heating step.

[0043] Step S5, Post-processing: The polyimide composite laminate obtained in step S4 is heat-treated at 420℃ for 120 minutes to obtain a high-temperature resistant, ultra-lightweight, low-dielectric polyimide composite material.

[0044] Example 2: A method for preparing a polyimide composite material includes the following steps: Step S1, Synthesis of polyimide oligomer precursor: In a 300 ml three-necked flask equipped with a mechanical stirrer and a nitrogen inlet, 0.068 mol (23.556 g) of 9,9-bis(4-aminophenyl)fluorene (BAFL) and 0.159 mol (39.489 g) of 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane (SIDA) were dissolved in 322.131 g of N-methylpyrrolidone. Under nitrogen protection, the mixture was stirred at room temperature to dissolve. After dissolution, 0.201 mol (62.352 g) of 3,3',4,4'-diphenyl ether tetracarboxylic dianhydride (ODPA) was gradually added. The mixture was stirred at room temperature for 4 h. After the reaction was completed, 0.051 mol (12.659 g) of 4-phenylethynylphthalic anhydride was gradually added to the solution. The mixture was stirred at room temperature for 3 h to obtain a polyamic acid solution with a solid content of 30%.

[0045] The prepreg preparation process in step S2, the prepreg preforming process in step S3, the hot pressing and curing process in step S4, and the post-processing process in step S5 are the same as in Example 1.

[0046] Example 3: A method for preparing a polyimide composite material includes the following steps: Step S1, Synthesis of polyimide oligomer precursor: In a 300 ml three-necked flask equipped with a mechanical stirrer and a nitrogen inlet, 0.159 mol (61.007 g) of 9,9-bis(3-fluoro-4-aminophenyl)fluorene (FFDA) and 0.068 mol (16.973 g) of 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane (SIDA) were dissolved in 356.979 g of N-methylpyrrolidone under nitrogen protection and stirred at room temperature. After dissolution, 0.201 mol (62.352 g) of 3,3',4,4'-diphenyl ether tetracarboxylic dianhydride (ODPA) was gradually added. The mixture was stirred at room temperature for 4 h. After the reaction was completed, 0.051 mol (12.659 g) of 4-phenylethynylphthalic anhydride was gradually added to the solution and stirred at room temperature for 3 h to obtain a polyamic acid solution with a solid content of 30%.

[0047] The prepreg preparation process in step S2, the prepreg preforming process in step S3, the hot pressing and curing process in step S4, and the post-processing process in step S5 are the same as in Example 1.

[0048] Example 4: A method for preparing a polyimide composite material includes the following steps: Step S1, Synthesis of polyimide oligomer precursor: In a 300 ml three-necked flask equipped with a mechanical stirrer and a nitrogen inlet, 0.136 mol (52.357 g) of 9,9-bis(3-fluoro-4-aminophenyl)fluorene (FFDA) and 0.091 mol (22.565 g) of 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane (SIDA) were dissolved in 349.844 g of N-methylpyrrolidone. Under nitrogen protection, the solution was stirred at room temperature until dissolved. After dissolution, 0.201 mol (62.352 g) of 3,3',4,4'-diphenyl ether tetracarboxylic dianhydride (ODPA) was gradually added. The mixture was stirred at room temperature for 4 h. After the reaction was completed, 0.051 mol (12.659 g) of 4-phenylethynyl phthalic anhydride was gradually added to the solution. The mixture was stirred at room temperature for 3 h to obtain a polyamic acid solution with a solid content of 30%.

[0049] The prepreg preparation process in step S2, the prepreg preforming process in step S3, the hot pressing and curing process in step S4, and the post-processing process in step S5 are the same as in Example 1.

[0050] Example 5: A method for preparing a polyimide composite material includes the following steps: Step S1, Synthesis of polyimide oligomer precursor: In a 300 ml three-necked flask equipped with a mechanical stirrer and a nitrogen inlet, 0.114 mol (43.631 g) of 9,9-bis(3-fluoro-4-aminophenyl)fluorene (FFDA) and 0.114 mol (28.206 g) of 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane (SIDA) were dissolved in 342.645 g of N-methylpyrrolidone. Under nitrogen protection, the mixture was stirred at room temperature to dissolve. After dissolution, 0.201 mol (62.352 g) of 3,3',4,4'-diphenyl ether tetracarboxylic dianhydride (ODPA) was gradually added. The mixture was stirred at room temperature for 4 h. After the reaction was completed, 0.051 mol (12.659 g) of 4-phenylethynylphthalic anhydride was gradually added to the solution. The mixture was stirred at room temperature for 3 h to obtain a polyamic acid solution with a solid content of 30%.

[0051] The prepreg preparation process in step S2, the prepreg preforming process in step S3, the hot pressing and curing process in step S4, and the post-processing process in step S5 are the same as in Example 1.

[0052] Example 6: A method for preparing a polyimide composite material includes the following steps: Step S1, Synthesis of polyimide oligomer precursor: In a 300 ml three-necked flask equipped with a mechanical stirrer and a nitrogen inlet, 0.091 mol (34.905 g) of 9,9-bis(3-fluoro-4-aminophenyl)fluorene (FFDA) and 0.136 mol (33.847 g) of 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane (SIDA) were dissolved in 335.447 g of N-methylpyrrolidone under nitrogen protection and stirred at room temperature. After dissolution, 0.201 mol (62.352 g) of 3,3',4,4'-diphenyl ether tetracarboxylic dianhydride (ODPA) was gradually added. The mixture was stirred at room temperature for 4 h. After the reaction was completed, 0.051 mol (12.659 g) of 4-phenylethynylphthalic anhydride was gradually added to the solution and stirred at room temperature for 3 h to obtain a polyamic acid solution with a solid content of 30%.

[0053] The prepreg preparation process in step S2, the prepreg preforming process in step S3, the hot pressing and curing process in step S4, and the post-processing process in step S5 are the same as in Example 1.

[0054] Example 7: A method for preparing a polyimide composite material includes the following steps: Step S1, Synthesis of polyimide oligomer precursor: In a 300 ml three-necked flask equipped with a mechanical stirrer and a nitrogen inlet, 0.068 mol (26.256 g) of 9,9-bis(3-fluoro-4-aminophenyl)fluorene (FFDA) and 0.159 mol (39.439 g) of 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane (SIDA) were dissolved in 328.314 g of N-methylpyrrolidone under nitrogen protection and stirred at room temperature. After dissolution, 0.201 mol (62.352 g) of 3,3',4,4'-diphenyl ether tetracarboxylic dianhydride (ODPA) was gradually added. The mixture was stirred at room temperature for 4 h. After the reaction was completed, 0.051 mol (12.659 g) of 4-phenylethynyl phthalic anhydride was gradually added to the solution and stirred at room temperature for 3 h to obtain a polyamic acid solution with a solid content of 30%.

[0055] The prepreg preparation process in step S2, the prepreg preforming process in step S3, the hot pressing and curing process in step S4, and the post-processing process in step S5 are the same as in Example 1.

[0056] Comparative Example 1: A method for preparing a polyimide composite material includes the following steps: Step S1, Synthesis of polyimide oligomer precursor: In a 300 ml three-necked flask equipped with a mechanical stirrer and a nitrogen inlet, 0.068 mol (23.556 g) of 9,9-bis(4-aminophenyl)fluorene (BAFL) and 0.159 mol (17.194 g) of m-phenylenediamine were dissolved in 270.109 g of N-methylpyrrolidone. Under nitrogen protection, the mixture was stirred at room temperature to dissolve. After dissolution, 0.201 mol (62.352 g) of 3,3',4,4'-diphenyl ether tetracarboxylic dianhydride (ODPA) was gradually added. The mixture was stirred at room temperature for 4 h. After the reaction was completed, 0.051 mol (12.659 g) of 4-phenylethynyl phthalic anhydride was gradually added to the solution. The mixture was stirred at room temperature for 3 h to obtain a polyamic acid solution with a solid content of 30%.

[0057] The prepreg preparation process in step S2, the prepreg preforming process in step S3, the hot pressing and curing process in step S4, and the post-processing process in step S5 are the same as in Example 1.

[0058] Comparative Example 2: A method for preparing a polyimide composite material includes the following steps: Step S1, Synthesis of polyimide oligomer precursor: In a 300ml three-necked flask equipped with a mechanical stirrer and a nitrogen inlet, 0.068mol (13.616g) of 4,4'-diaminodiphenyl ether and 0.159mol (17.194g) of m-phenylenediamine were dissolved in 246.916g of N-methylpyrrolidone. Under nitrogen protection, the mixture was stirred at room temperature to dissolve. After dissolution, 0.201mol (62.352g) of 3,3',4,4'-diphenyl ether tetracarboxylic dianhydride (ODPA) was gradually added. The mixture was stirred at room temperature for 4 hours. After the reaction was completed, 0.051mol (12.659g) of 4-phenylethynylphthalic anhydride was gradually added to the solution. The mixture was stirred at room temperature for 3 hours to obtain a polyamic acid solution with a solid content of 30%.

[0059] The prepreg preparation process in step S2, the prepreg preforming process in step S3, the hot pressing and curing process in step S4, and the post-processing process in step S5 are the same as in Example 1.

[0060] Comparative Example 3: A method for preparing a polyimide composite material includes the following steps: Step S1, Synthesis of polyimide oligomer precursor: In a 300 ml three-necked flask equipped with a mechanical stirrer and a nitrogen inlet, 0.068 mol (34.711 g) of 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane and 0.159 mol (17.194 g) of m-phenylenediamine were dissolved in 296.137 g of N-methylpyrrolidone. Under nitrogen protection, the mixture was stirred at room temperature to dissolve. After dissolution, 0.201 mol (62.352 g) of 3,3',4,4'-diphenyl ether tetracarboxylic dianhydride (ODPA) was gradually added. The mixture was stirred at room temperature for 4 h. After the reaction was completed, 0.051 mol (12.659 g) of 4-phenylethynyl phthalic anhydride was gradually added to the solution. The mixture was stirred at room temperature for 3 h to obtain a polyamic acid solution with a solid content of 30%.

[0061] The prepreg preparation process in step S2, the prepreg preforming process in step S3, the hot pressing and curing process in step S4, and the post-processing process in step S5 are the same as in Example 1.

[0062] The performance testing methods for the embodiments and comparative examples of this invention are as follows: Density: Tested in accordance with standard GB / T 1463-2005 "Test Method for Density and Relative Density of Fiber Reinforced Plastics".

[0063] Dielectric constant: The waveguide method was used, referring to the standard GB / T 12636-1990 "Test Method for Complex Dielectric Constant of Microwave Dielectric Substrates", and the test was conducted at a frequency of 10 GHz.

[0064] Glass transition temperature (Tg): The dynamic thermomechanical analysis (DMA) method was used, referring to the standard GB / T 22567-2008 "Determination of glass transition temperature of electrical insulating materials", under nitrogen atmosphere, heating rate of 5℃ / min and frequency of 1 Hz.

[0065] Table 1. Comparison of material properties of Examples 1 to 3, Comparative Examples 1, 2 and 3 above. Table 1 shows that comparing Examples 1 and 2, it can be seen that adding a silane structure to the resin can effectively reduce the dielectric constant, and the effect of siloxane is better than that of silane. Comparing Examples 2, 7, Comparative Examples 1, 2, and 3, it can be seen that adding fluorene and fluorine elements to the resin simultaneously can effectively increase Tg and reduce the dielectric constant. It was also found that 9,9-bis(3-fluoro-4-aminophenyl)fluorene (FFDA) and 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane (SIDA) have a more significant effect on reducing the dielectric constant and increasing Tg. Comparing Examples 3 to 7, it was found that the material performance was best when the molar ratio of 9,9-bis(3-fluoro-4-aminophenyl)fluorene (FFDA) and 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane (SIDA) was 1:1.

[0066] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a polyimide composite material, characterized in that, Includes the following steps: Step S1, Synthesis of polyimide oligomer precursor: Under an inert atmosphere, aromatic diamine and diamine monomers containing siloxane structures are dissolved in an organic solvent. After complete dissolution, aromatic dianhydride monomers are added, and the reaction is carried out at room temperature for 2-4 hours. Then, a capping agent is added, and the mixture is stirred for 3-5 hours to obtain a polyamic acid solution. The molar ratio of the mixture of aromatic dianhydride, aromatic diamine, and diamine monomers containing siloxane structures, to the capping agent is n:(n+1):2, where n=1-8. The mass concentration of the organic solvent solution is 25%-65%. Step S2: Preparation of prepreg by solution method: Hollow quartz fibers are impregnated with polyamic acid solution and dried at room temperature to obtain a prepreg with a resin content of 30% to 50%; wherein the hollowness of the hollow quartz fibers is 32% to 50%. Step S3, Prepreg Preforming: Cut and lay the prepreg according to the set size and angle to obtain the preform. Use the vacuum bag method in the oven to preform the preform to obtain the preformed laminated blank. Step S4, Hot pressing and curing: The pre-formed laminate blank is hot-pressed and cured to obtain a polyimide composite laminate. Step S5, Post-processing: Heat-treat the polyimide composite preform to obtain the polyimide composite material.

2. The method for preparing a polyimide composite material according to claim 1, characterized in that, In step S3, the preform of the preform is pre-formed using a vacuum bag method with programmed heating. The programmed heating process is as follows: heat up to 85℃±5℃ and hold for 60 min, continue to heat up to 110℃±5℃ and hold for 60 min~120 min, and then continue to heat up to 150℃±5℃ and hold for 60 min~180 min to complete the preforming and obtain the preformed laminated preform. The heating rate is 1~2℃ / min for each heating.

3. The method for preparing a polyimide composite material according to claim 1, characterized in that, In step S3, the pre-formed material is placed into a vacuum bag and vacuumed in an oven to a vacuum degree of not less than 0.085 MPa.

4. The method for preparing a polyimide composite material according to claim 1, characterized in that, In step S4, the preformed laminate blank is cured in a hot press or autoclave. When the temperature is raised to 290℃~320℃, a pressure of 1~4MPa is applied. Then, the temperature is raised to 385℃±5℃ and held for 300±10min for hot pressing. After cooling, a polyimide composite laminate is obtained. The heating rate is 1~2℃ / min each time the temperature is raised.

5. The method for preparing a polyimide composite material according to claim 1, characterized in that, In step S5, the heat treatment is carried out at 420℃~450℃ for 60~180min.

6. The method for preparing a polyimide composite material according to claim 1, characterized in that, The organic solvent is any one or any combination of two or more of N-methylpyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, dimethyl sulfoxide, chloroform, dichloromethane, and dioxane.

7. The method for preparing a polyimide composite material according to claim 1, characterized in that, The aromatic diamine is p-phenylenediamine, m-phenylenediamine, 4,4'-diaminobiphenyl, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenylmethane, 2,2'-dimethyl-4,4'-diaminobiphenyl, 3,3'-dimethyl-4,4'-diaminobiphenyl, 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl, 2,2'-bis(trifluoromethyl)-4,4'-diaminodiphenyl ether, 4,4'-diaminobenzophenone, 2,2'-bis(4-aminophenyl)hexafluoropropane, 1,3-bis(4-aminophenoxy)benzene, 1,3-bis(3-aminophenyl)hexafluoropropane, etc. 1,4-Bis(4-aminophenoxy)benzene, 1,4-bis(2-trifluoromethyl-4-aminophenoxy)benzene, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 9,9-bis(4-aminophenyl)fluorene (BAFL), 9,9-bis(3-fluoro-4-aminophenyl)fluorene (FFDA), 9,9-bis[4-(4-aminophenoxy)phenyl]fluorene (BAOFL), 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane, 3,3'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl sulfone, or any combination of two or more of these.

8. The method for preparing a polyimide composite material according to claim 1, characterized in that, The aromatic dianhydrides used are pyromellitic dianhydride (PMDA), 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), 4,4'-oxobisphthalic anhydride (ODPA), 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BTDA), 3,3',4,4'-diphenyl sulfone tetracarboxylic dianhydride (DSDA), 5,5'-(propane-2,2-diyl)bis(isobenzofuran-1,3-dione), 2,3,3',4'-benzophenone tetracarboxylic dianhydride (α-BTDA), 2,3,3',4'-diphenyl ether tetracarboxylic dianhydride (α-ODPA), 3,3',4,4'-diphenyl ether tetracarboxylic dianhydride (ODPA), 2,3,3',4'-diphenyl sulfide tetracarboxylic dianhydride (α-TDPA), 1,2... The dianhydride is any one or any combination of two or more of the following: 3,4-cyclobutanetetracarboxylic dianhydride (CBDA), 1,2,3,4-cyclopentanetetracarboxylic dianhydride (CPDA), 1,2,4,5-cyclohexanetetracarboxylic dianhydride (HPMDA), 2,3,5-tricarboxylated cyclopentylacetic dianhydride, bicyclo[2.2.1]hept-2,3,5,6-tetracarboxylic dianhydride, 3,4,6-tricarboxylated bicyclo[2.2.2]heptylacetic dianhydride, bicyclo[2.2.2]oct-2,3,5,6-tetracarboxylic dianhydride, bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride, decahydrobiphenyl-3,3',4,4'-tetracarboxylic dianhydride, and decahydro-1,4,5,8-dimethylenenaphthalene-2,3,6,7-tetracarboxylic dianhydride.

9. The method for preparing a polyimide composite material according to claim 1, characterized in that, The diamine containing the siloxane structure is any one or any combination of two or more of the following: 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane (SIDA), bis(4-aminophenoxy)tetramethyldisiloxane (p-TMDS), bis(3-aminophenoxy)tetramethyldisiloxane (m-TMDS), bis(4-aminophenoxy)dimethyl-1,3-diphenyldisiloxane (DPDS), bis(4-aminophenoxy)dimethylsilane (APDS), and bis(4-aminophenoxy)methylphenylsilane (PMPS).

10. The method for preparing a polyimide composite material according to claim 1, characterized in that, The capping agent is any one of 4-phenylethynyl phthalic anhydride and 3-phenylethynyl phthalic anhydride, or a combination of both.

11. A polyimide composite material prepared by the method for preparing a polyimide composite material according to any one of claims 1 to 10, characterized in that, The polyimide composite material is composed of hollow quartz fibers and silicon-containing polyimide resin. The fiber volume content of the polyimide composite material is 45%-60%, and the density of the polyimide composite material is 1.25-1.55 g / cm³. The silicon-containing polyimide resin is polymerized from a mixture of aromatic dianhydride, aromatic diamine and diamine containing siloxane structure, and end-capping agent.

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