Preparation method of polyimide composite material
By combining phenylacetylene-terminated polyimide prepolymers with o-phenol phenolic resins and other materials to form a cross-linked network structure, the problems of easy creep and interfacial instability of traditional polyimides under high temperature conditions are solved, thereby improving the heat resistance and processing performance of the composite material.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-26
- Publication Date
- 2026-04-14
AI Technical Summary
Traditional thermoplastic polyimides are prone to creep or decomposition at high temperatures, resulting in a contradiction between processability and high performance. The bonding between the resin and fiber interface is unstable, making molding and processing difficult and affecting the mechanical properties and long-term durability of the composite material.
A polyimide prepolymer with phenylacetylene end-capped polymer is mixed with o-phenol phenolic resin, phenolic resin, curing accelerator, coupling agent and release agent, and impregnated with fibers through a tension control system and cured in a stepped heating mold to form a cross-linked network structure, thereby improving interfacial bonding ability and thermal oxidation stability.
It achieves a tight bond between fibers and resin at high temperatures, improving the heat resistance, mechanical properties and thermal stability of the composite material, while also possessing good processability and recyclability.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of polyimide technology, and more specifically to a method for preparing a polyimide composite material. Background Technology
[0002] Polyimide (PI) is a class of high-performance polymers containing imide ring structures in their molecular chains. Renowned for its excellent high-temperature resistance, superior mechanical properties, good chemical stability, and dielectric properties, it is widely used in cutting-edge fields such as aerospace, microelectronics, and the automotive industry. While traditional thermoplastic polyimides have relatively good processability, their glass transition temperature (Tg) and long-term service temperature are limited. They are prone to creep or decomposition in extreme environments exceeding 300°C, restricting their application in higher-temperature scenarios.
[0003] To further improve the heat resistance of polyimides, researchers have developed thermosetting polyimides. Among them, phenylacetylene-terminated polyimide prepolymers prepared with active end-capping agents such as phenylacetylene anhydride are currently a research hotspot. When heated, the terminal phenylacetylene groups undergo a cross-linking and curing reaction, forming a highly cross-linked three-dimensional network structure. This significantly improves the material's glass transition temperature, thermal decomposition temperature, and thermal oxidation stability, enabling long-term use in high-temperature environments above 370°C. However, current polyimide composite material processing still faces the following challenges: 1. The contradiction between processability and high performance: Many high-performance polyimide resins have high viscosity or poor melt flowability in the prepolymer stage, making it difficult to achieve sufficient and uniform wetting of the fiber bundles when compounded with reinforcing fibers (such as PI fibers). This can lead to defects inside the composite material, forming microcrack sources, and ultimately affecting the mechanical properties and long-term durability of the composite material at high temperatures.
[0004] 2. Bottleneck of thermal oxidation stability: Although the matrix resin itself has high thermal stability, in long-term high-temperature and oxygen-containing environments, the interface between the resin and fiber easily becomes a weak point, leading to interfacial degradation and a rapid decline in the overall performance of the composite material. Simple physical blending is insufficient to effectively solve the problem of interfacial stability under extreme conditions.
[0005] 3. Molding and Processing Challenges of Composite Materials: For continuous molding processes such as pultrusion, the resin system must possess suitable reactivity, viscosity window, and curing characteristics. Some existing polyimide resin systems either cure too quickly, leading to mold blockage, or have excessively long curing cycles, impacting production efficiency. Furthermore, precisely controlling the tension and temperature profiles during high-temperature curing to ensure synergistic effects between the fiber and resin is another technical challenge in preparing high-performance composite material products.
[0006] Therefore, there is an urgent need in this field to develop a new type of polyimide resin that not only has extremely high intrinsic heat resistance and resistance to thermal decomposition, but also has good processability and can form a stable and strong interface with polyimide fibers, so as to manufacture composite material structural parts that can be used stably for a long time in more demanding thermal-oxygen environments. Summary of the Invention
[0007] The purpose of this invention is to address the shortcomings of the prior art by providing a method for preparing polyimide composite materials, which can not only improve the interfacial bonding ability between the resin and PI fiber, but also enhance the thermal oxidation stability and high temperature resistance of the composite material.
[0008] A method for preparing a polyimide composite material, characterized by comprising the following steps: S1. Mix the phenylacetylene-terminated polyimide prepolymer powder with o-phenol phenolic resin, phenolic resin, curing accelerator, coupling agent and release agent, stir, add solvent to adjust the viscosity of the mixture, and then disperse at high speed to obtain modified polyimide phenolic resin liquid. S2. The polyimide fiber filament is impregnated with the modified polyimide phenolic resin solution prepared in step S1 through a tension control system. The solution is then drawn into a heating mold for step-by-step temperature curing through a pre-forming mold. Finally, it is cut to obtain the polyimide composite material.
[0009] Furthermore, the phenylacetylene-terminated polyimide prepolymer powder is prepared by the following method: (1) Synthesis of polyamic acid solution: Dissolve 12-15 parts of m-phenylenediamine and 80-90 parts of 1,3-bis(3-aminophenoxy)benzene in 120-140 parts of N-methylpyrrolidone solvent. Under the cooling and stirring of an ice-water bath, add 100-120 parts of bisphenol A type diether dianhydride in batches, and then add 0.1-0.2 parts of phthalic anhydride. Continue stirring and reacting for 2-4 hours to obtain polyamic acid solution; (2) End-capping and chemical imidization: Add 10-20 parts of phenylethynyl trimellitic anhydride to the polyamic acid solution obtained in step (1), react at room temperature for 1-2 hours, add a mixed solution containing 5-7 parts of pyridine and 8-10 parts of acetic anhydride, react at 50-80℃ for 4-6 hours to carry out chemical imidization; after the reaction is completed, pour the solution into deionized water to precipitate, filter, wash, and vacuum dry at 80-120℃ to obtain phenylethynyl-terminated polyimide prepolymer powder.
[0010] Further, in step S1, by weight, there are 100 parts of polyimide prepolymer, 80-100 parts of o-phenolic resin, 40-50 parts of phenolic resin, 5-6 parts of curing accelerator, 0.5-1 part of coupling agent, and 1-2 parts of release agent.
[0011] Furthermore, the curing accelerator is one of 2-ethyl-4-methylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, and 2-undecylimidazole.
[0012] Further, the coupling agent is a silane coupling agent selected from at least one of vinyltris(2-methoxyethoxy)silane, γ-(methacryloyloxy)propyltrimethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, and γ-glycidoxypropyltrimethoxysilane.
[0013] Furthermore, the release agent is an internal release agent, selected from zinc stearate, higher fatty alcohol / amine and ethylene oxide adducts, and polysiloxane compounds.
[0014] Furthermore, the solvent used to adjust the viscosity of the system is ethanol, and the viscosity of the mixed system is 800-1100 mPa at 25°C.
[0015] Furthermore, the polyimide fiber filament is obtained by dry spinning, with a fiber diameter of 16~18 μm, a fineness of 2.2 dtex, a strength of 2.8 cN / dtex, and an elongation of 34%.
[0016] Furthermore, the tension control system consists of a magnetic powder brake tensioner and a tension sensor.
[0017] Furthermore, the preform mold is designed to be made of ceramic / alumina and polytetrafluoroethylene.
[0018] Furthermore, the heating device for the heating mold is an electric heating rod or an electric heating plate with a length of 1.6 m.
[0019] Furthermore, the specific operation of the stepped temperature curing is as follows: The fiber filaments are drawn through the heating zones at a speed of 600~1500 mm / min. The total length of the heating zones is 80 cm, and they are divided into 4 temperatures: the first temperature zone is 15 cm long and the temperature is 200~210℃; the second temperature zone is 20 cm long and the temperature is 220~230℃; the third temperature zone is 25 cm long and the temperature is 240~250℃; and the fourth temperature zone is 20 cm long and the temperature is 260~270℃.
[0020] Furthermore, the traction device is a tracked pultrusion machine with a pultrusion length of 1200 mm and a pressure set at 10000~15000 N.
[0021] The present invention also provides a composite material of polyimide.
[0022] Furthermore, in the composite material, the volume of the polyimide fiber filament is 50-80% of the volume of the polyimide composite material.
[0023] Compared with the prior art, the technical solution provided in this application has the following beneficial effects: (1) The present invention provides a thermosetting resin for blending a phenylacetylene-based carbon-terminated polyimide compound with a phenolic resin. The resin has a lower Tg value than epoxy resin, and its viscosity and reaction rate are basically the same as those of polyurethane. It has excellent processability and is easy to impregnate fibers and pultrude.
[0024] (2) The polyimide composite material provided by this invention, during the heating and curing process, in the low-temperature stage (first temperature zone): imidazole promotes the rapid curing of phenolic resin, forming the first network and giving the material its initial shape and strength; in the medium-high temperature stage (second and third temperature zones): phenylacetylene end groups undergo addition polymerization, forming a second extremely heat-resistant polyimide crosslinking network. The two networks interpenetrate and synergistically reinforce each other. The network structure is stabilized by a coupling agent, making the fiber-resin interface tightly bonded, ultimately resulting in a novel composite material with excellent mechanical properties and extreme heat resistance.
[0025] (3) The polyimide composite material of the present invention has extremely high high temperature resistance, making up for the shortcoming of traditional composite materials that cannot work stably for a long time at 350°C, while also having extremely high thermal stability and anti-aging properties. In addition, the composite material is recyclable, which can solve the environmental problem of traditional thermosetting composite materials being difficult to dispose of after disposal. Detailed Implementation
[0026] The following are specific embodiments of the present invention, which further describe the technical solution of the present invention, but the present invention is not limited to these embodiments.
[0027] Example 1 A method for preparing a polyimide composite material is provided, comprising the following steps: (1) Synthesis of phenylethynyl-terminated polyimide prepolymer In a dry reactor equipped with a stirrer and nitrogen protection, 130 parts by weight of N-methylpyrrolidone (NMP), 13 parts by weight of m-phenylenediamine, and 85 parts by weight of 1,3-bis(3-aminophenoxy)benzene were added sequentially, and stirred until completely dissolved. Under ice-water bath cooling (temperature controlled <30°C), 105 parts by weight of bisphenol A diether dianhydride were added in batches. After the addition was complete, 0.15 parts by weight of phthalic anhydride were added, and the reaction was continued to be stirred at room temperature for 3 hours to obtain a viscous polyamic acid solution.
[0028] Add 12 parts of phenylethynyl trimellitic anhydride to the above polyamic acid solution and continue stirring at room temperature for 1.5 hours. Then, add a mixed solution of 5.5 parts pyridine and 9 parts acetic anhydride, gradually heat the reaction system to 60°C, and react for 5 hours to carry out chemical imidization. After the reaction is complete, pour the reaction solution into a large amount of deionized water to precipitate a solid. Filter and wash the solid three times with ethanol. Dry the obtained solid under vacuum at 100°C for 24 hours to obtain a pale yellow powder of phenylethynyl-terminated polyimide prepolymer.
[0029] (2) Preparation of modified polyimide phenolic resin solution By weight, 100 parts of the polyimide prepolymer powder obtained in step (1) above were mixed with 85 parts of o-phenolic resin, 45 parts of thermoplastic phenolic resin, 5.5 parts of 2-ethyl-4-methylimidazolium, 0.8 parts of γ-(methacryloyloxy)propyltrimethoxysilane, and 2 parts of zinc stearate, and stirred. Ethanol was added to adjust the viscosity of the mixture to 900 mPa at 25°C, and the mixture was stirred and mixed in a high-speed disperser for 1 hour to obtain a uniform modified polyimide phenolic resin solution.
[0030] (3) Preparation of composite materials by pultrusion molding Polyimide fiber filaments with a fineness of 2.2 dtex (approximately 18 μm in diameter) were controlled by a tension control system to maintain a single fiber tension of 15 N and a fiber volume content of 80%. After the fibers were neatly arranged by a yarn collecting plate, they were impregnated with the modified polyimide phenolic resin obtained in step (2).
[0031] The impregnated fiber bundles pass through a preformed plate made of ceramic material and enter a 1.6-meter-long heating mold. The mold is divided into four gradient heating zones (total length 80 cm): the first zone (15 cm long) is 210°C; the second zone (20 cm long) is 230°C; the third zone (25 cm long) is 250°C; and the fourth zone (20 cm long) is 270°C.
[0032] Under the traction of a tracked pultrusion machine (traction speed set at 1000 mm / min), the resin-impregnated fibers undergo gradient heating and curing in the mold. After continuous demolding, they are cut into specified lengths to obtain polyimide composite profiles.
[0033] Example 2 The steps and reaction conditions in Example 2 are the same as in Example 1, except that: (1) Synthesis of phenylethynyl-terminated polyimide prepolymer The raw material dosages were adjusted as follows: 140 parts NMP, 15 parts m-phenylenediamine, 90 parts 1,3-bis(3-aminophenoxy)benzene, 110 parts bisphenol A type diether dianhydride, 0.2 parts phthalic anhydride, 15 parts phenylethynyl trimellitic anhydride, 6 parts pyridine, and 10 parts acetic anhydride.
[0034] (2) Preparation of modified polyimide phenolic resin solution The coupling agent was adjusted to 0.8 parts of β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane and 0.8 parts of γ-glycidyl etheroxypropyltrimethoxysilane, and the release agent was changed to 2 parts of polysiloxane. The viscosity of the mixed system was adjusted to 800 mpas at 25°C.
[0035] Example 3 The steps and reaction conditions in Example 3 are the same as in Example 1, except that: (1) Synthesis of phenylethynyl-terminated polyimide prepolymer The raw material dosages were adjusted as follows: 120 parts NMP, 12 parts m-phenylenediamine, 80 parts 1,3-bis(3-aminophenoxy)benzene, 100 parts bisphenol A type diether dianhydride, 0.1 parts phthalic anhydride, 10 parts phenylethynyl trimellitic anhydride, 5 parts pyridine, and 8 parts acetic anhydride.
[0036] (2) Preparation of modified polyimide phenolic resin The raw material dosage was adjusted as follows: 80 parts of o-phenolic resin, 40 parts of thermoplastic phenolic resin, 5 parts of 2-ethyl-4-methylimidazolium, 0.5 parts of vinyltris(2-methoxyethoxy)silane as coupling agent, and 1 part of zinc stearate as mold release agent. The viscosity of the mixture was adjusted to 1100 mpas at 25°C.
[0037] (3) Preparation of composite materials by pultrusion molding The temperatures of each zone of the mold are adjusted as follows: Zone 1 200℃, Zone 2 220℃, Zone 3 240℃, and Zone 4 260℃.
[0038] Comparative Example 1 A comparative example of a composite material is provided, the raw materials and preparation method of which are the same as those of Example 3, except that 1,3-bis(3-aminophenoxy)benzene is not added in step (1).
[0039] Comparative Example 2 A comparative example of a composite material is provided, the raw materials and preparation method of which are the same as those of Example 3, except that: in step (2), the polyimide prepolymer obtained in step (1) is not added.
[0040] Comparative Example 3 A comparative example of a composite material is provided, the raw materials and preparation method of which are the same as those of Example 3, except that: in step (2), an equal weight of general-purpose epoxy resin (such as E-51 type) is used to replace thermoplastic phenolic resin, and the amount of curing accelerator 2-ethyl-4-methylimidazole is adjusted to 1 part by weight (based on the conventional amount of epoxy resin).
[0041] The composite materials prepared in the above embodiments and comparative examples were tested for high temperature resistance, thermal stability, flame retardancy, aging resistance, and mechanical properties using the following methods: High temperature resistance: GB / T 36264-2018 Test method for tensile strength of fiber composites under ultra-high temperature oxidizing environment; Thermal stability (°C): GB / T22567—2008 Test method for determination of glass transition temperature of electrical insulating materials; Flame retardancy: GB / T8924 Test method for combustion performance of fiber reinforced plastics by oxygen index method; Aging performance: GB / T2573 Test method for aging performance of glass fiber reinforced plastics; Mechanical properties, i.e., tensile strength (MPa): Refer to GB_T 31539-2015 Pultruded profiles of fiber reinforced composite materials for structural use.
[0042] The test results are shown in Table 1.
[0043] Table 1 Performance Test Table
[0044] As shown in Table 1, the composite material prepared in the embodiments of the present invention exhibits excellent comprehensive properties: extremely high glass transition temperature (>280℃) and high temperature strength retention rate (>90%), indicating its excellent heat resistance; high oxygen index (>70%) and excellent resistance to damp heat aging, indicating its good flame retardancy and durability; and high room temperature mechanical strength.
[0045] Compared with Comparative Example 1, the Example introduced a flexible segment monomer, 1,3-bis(3-aminophenoxy)benzene, which improved the toughness and processability of the material while maintaining high heat resistance, resulting in better overall performance.
[0046] Compared with Comparative Example 2 (pure phenolic resin matrix), the heat resistance, mechanical properties and aging resistance of the examples were greatly improved due to the introduction of phenylacetylene-terminated polyimide prepolymers for modification.
[0047] Compared with Comparative Example 3 (epoxy resin replacing part of the phenolic resin), the all-phenolic system in the examples has better compatibility and reactivity with the polyimide prepolymer, making the composite material more advantageous in terms of high temperature resistance and flame retardancy.
[0048] For any points not covered above, existing technologies shall apply.
[0049] Although specific embodiments of the present invention have been described in detail by way of examples, those skilled in the art should understand that the above examples are for illustrative purposes only and are not intended to limit the scope of the invention. Those skilled in the art can make various modifications or additions to the described specific embodiments or use similar methods to replace them, without departing from the direction of the invention or exceeding the scope defined by the appended claims. Those skilled in the art should understand that any modifications, equivalent substitutions, improvements, etc., made to the above embodiments based on the technical essence of the present invention should be included within the protection scope of the present invention.
Claims
1. A method for preparing a polyimide composite material, characterized in that, Includes the following steps: S1. Mix the phenylacetylene-terminated polyimide prepolymer powder with o-phenol phenolic resin, phenolic resin, curing accelerator, coupling agent and release agent, stir, add solvent to adjust the viscosity of the mixture, and then disperse at high speed to obtain modified polyimide phenolic resin liquid. S2. Impregnate polyimide fiber filaments with modified polyimide phenolic resin solution, preform, cure by step heating, and finally cut to obtain polyimide composite material. The phenylacetylene-terminated polyimide prepolymer powder was prepared by the following method: (1) Synthesis of polyamic acid solution: Dissolve 12-15 parts of m-phenylenediamine and 80-90 parts of 1,3-bis(3-aminophenoxy)benzene in 120-140 parts of N-methylpyrrolidone solvent. Under the cooling and stirring of an ice-water bath, add 100-120 parts of bisphenol A type diether dianhydride in batches, and then add 0.1-0.2 parts of phthalic anhydride. Continue stirring and reacting for 2-4 hours to obtain polyamic acid solution; (2) End-capping and chemical imidization: Add 10-20 parts of phenylethynyl trimellitic anhydride to the polyamic acid solution obtained in step (1), react at room temperature for 1-2 hours, add a mixed solution containing 5-7 parts of pyridine and 8-10 parts of acetic anhydride, react at 50-80℃ for 4-6 hours to carry out chemical imidization; after the reaction is completed, pour the solution into deionized water to precipitate, filter, wash, and vacuum dry at 80-120℃ to obtain phenylethynyl-terminated polyimide prepolymer powder.
2. The preparation method according to claim 1, characterized in that, In step S1, by weight, there are 100 parts of polyimide prepolymer, 80-100 parts of o-phenolic resin, 40-50 parts of phenolic resin, 5-6 parts of curing accelerator, 0.5-1 part of coupling agent, and 1-2 parts of release agent.
3. The preparation method according to claim 1, characterized in that, The curing accelerator is one of 2-ethyl-4-methylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, and 2-undecylimidazole.
4. The preparation method according to claim 1, characterized in that, The coupling agent is a silane coupling agent selected from at least one of vinyltris(2-methoxyethoxy)silane, γ-(methacryloyloxy)propyltrimethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, and γ-glycidoxypropyltrimethoxysilane.
5. The preparation method according to claim 1, characterized in that, The release agent is an internal release agent, selected from zinc stearate, higher fatty alcohol / amine and ethylene oxide adducts, and polysiloxane compounds.
6. The preparation method according to claim 1, characterized in that, The solvent used to adjust the viscosity of the system is ethanol, and the viscosity of the mixed system is 800-1100 mpas at 25°C.
7. The preparation method according to claim 1, characterized in that, The polyimide fiber filaments are produced by dry spinning, with a fiber diameter of 16-18 μm, a fineness of 2.2 dtex, a strength of 2.8 cN / dtex, and an elongation of 34%.
8. The preparation method according to claim 1, characterized in that, The specific operation of the stepped temperature curing is as follows: The fiber filaments are drawn through the heating zones at a speed of 600~1500 mm / min. The total length of the heating zones is 80 cm, and they are divided into 4 temperatures: the first temperature zone is 15 cm long and the temperature is 200~210℃; the second temperature zone is 20 cm long and the temperature is 220~230℃; the third temperature zone is 25 cm long and the temperature is 240~250℃; and the fourth temperature zone is 20 cm long and the temperature is 260~270℃.
9. A polyimide composite material prepared by the preparation method according to any one of claims 1-7.
10. The polyimide composite material according to claim 9, characterized in that, The volume of the polyimide fiber filament is 50-80% of the volume of the polyimide composite material.