Polyimide resin-based composite material and preparation method thereof

Abstract

The invention discloses a polyimide resin-based composite material and a preparation method thereof, and belongs to the technical field of composite materials. In order to solve the problems of poor high-temperature resistance and complex forming process of a polyimide composite material in the prior art, the invention mainly adopts a mode of combining phenylacetylene-terminated thermosetting polyimide resin with different types of reinforcements, and adopts a process of preparing a prepreg and carrying out outer layer wrapping and high-temperature curing. The method can effectively improve the long-term high temperature resistance of the polyimide composite material, avoids the problem of unstable volatilization of the traditional antioxidant, and ensures the mechanical strength stability of the material. The polyimide composite material can be used for a long time under a high-temperature condition, and is suitable for wider application fields.

Description

Technical Field

[0001] The present invention relates to a polyimide resin-based composite material resistant to long-term high temperature and a preparation method thereof, belonging to the technical field of composite materials. Background Art

[0002] With the development of aerospace and weapon equipment technologies, the working temperatures of components at positions such as aircraft engine blades, bushings, radomes near the tail nozzles, and the airframe structures of high-speed aircraft have exceeded 350 °C. In addition, the components also have to withstand aerodynamic loads and vibration shock damages during flight. Therefore, composite materials need to have high mechanical strength, excellent heat resistance, and long-term service stability. The widely used thermosetting resin-based composite materials such as epoxy resin, cyanate resin, bismaleimide resin, phenolic resin, and cyanide resin have a long-term service temperature not higher than 300 °C and cannot meet the requirements for use at higher temperatures.

[0003] Thermosetting polyimide resin-based composite materials are one of the resin-based composite materials with the highest temperature resistance grades at present. Among them, the polyimide resin capped with phenylene groups can be applied to prepare high-temperature resistant components in aerospace and weapon equipment due to its good processability and high glass transition temperature of the cured product. Although the thermosetting polyimide resin itself has a relatively high glass transition temperature and thermal decomposition temperature, the composite materials cured after being mixed with reinforcing bodies such as glass fiber / quartz fiber / carbon fiber are prone to resin decomposition on the surface and inside of the fiber surface layer at long-term high temperatures, resulting in a decrease in the mechanical properties of the materials. The decomposition of the surface resin of the composite material at long-term high temperatures is because the melt viscosity of the polyimide resin is relatively high and the infiltration with the fiber reinforcing body is limited, so micropores are likely to remain on the fiber surface during the forming process of the composite material. These micropores will show high activity at high temperatures due to their large specific surface area, causing the decomposition of the surface resin of the composite material. Therefore, reducing the thermal aging of the main chain structure of the polyimide resin and the phenylene cross-linked structure caused by the internal micropores of the material is the key to the long-term thermal aging resistance of the material at high temperatures.

[0004] Patent CN105392842A provides a polyimide resin composition and a polyimide resin-fiber composite material. Although it is mentioned that the heat aging resistance of the composite material can be improved by adding an antioxidant as an additive to the polyimide resin system, the addition method of the antioxidant is direct blending, and it is difficult to ensure uniformity. The antioxidant is also easily volatilized at the high temperature during the forming process. Secondly, a relatively high effective content of the antioxidant addition is also required (0.5-2% of the resin mass fraction).

[0005] Patent CN111154260A provides an antioxidant polyimide prepreg and its preparation method. By adding a certain proportion of nano- and micron-sized ceramic powders to the polyimide mixed solution system, the polyimide prepreg is prepared. At high temperatures, the introduction of boron and silicon-based substances can promote the spreading of the melt in the composite system composed of the polyimide mixed solution and the reinforcing fibers during high-airflow scouring and ablation, and then form a protective layer on the surface, playing a role in oxygen resistance and erosion resistance. However, this method also faces problems such as possible agglomeration and difficult uniform dispersion of the ceramic powder additives. Secondly, the protective layer formed by high temperature has low density and limited actual protection effect.

[0006] Currently, there are two methods for preparing polyimide prepregs. One is to use the polyimide acid intermediate in the synthesis process of PMR-type polyimide resin to prepare the prepreg. One is to prepare the resin solution by the PMR method, and then prepare the prepreg, and then carry out imidization reaction and curing after laying up. Another method is that during the resin synthesis process, the polyimide resin is imidized to form an isomeric polyimide oligomer, and then dissolved in an organic solvent at a certain concentration to prepare a prepreg, and then carry out a curing reaction after laying up. Summary of the Invention

[0007] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a polyimide composite material with stable process, simple operation and long-time high-temperature resistance and its preparation method. The polyimide composite material has simple forming processability, a wide applicable system and long-time high-temperature resistance.

[0008] The technical solution adopted by the present invention to achieve its purpose is as follows:

[0009] In the first aspect, the present invention provides a preparation method of a polyimide resin-based composite material, including the following steps:

[0010] (1) Using a thermosetting polyimide resin capped with phenylethynyl as the matrix, mixing it with an organic solvent to prepare a resin solution;

[0011] (2) Based on the above resin solution, using quartz fiber or carbon fiber as the reinforcing body, preparing a quartz fiber or carbon fiber-reinforced polyimide resin prepreg, that is, prepreg A;

[0012] (3) Based on the above resin solution, using polyimide fiber as the reinforcing body, preparing a polyimide fiber-reinforced polyimide resin prepreg, that is, prepreg B;

[0013] (4) Using prepreg A as the main prepreg, carrying out laying or winding for shaping; using prepreg B as the outer prepreg, and carrying out outer wrapping outside the prepreg A that has been laid or wound and shaped;

[0014] (5) Subject all the prepregs with outer wrapping to high-temperature curing to obtain a polyimide composite material resistant to long-term high temperatures.

[0015] Preferably, the phenylacetylene-terminated thermosetting polyimide resin in step (1) is a prepolymer or oligomer of PMR-type polyimide resin.

[0016] More preferably, the prepolymer of PMR-type polyimide resin is obtained by reacting dimethyl aromatic tetracarboxylate or monoalkyl phthalate with aromatic diamine and is soluble in lower alcohols.

[0017] More preferably, the polyimide oligomer is an imidized soluble polyimide and is soluble in polar organic solvents.

[0018] Preferably, the organic solvent in step (1) is selected from one or more of methanol, ethanol, isopropanol, ethylene glycol, glycerol, N,N-dimethylacetamide (DMAC), dimethylformamide (DMF), dioxane, dichloromethane, tetrahydrofuran, dimethyl sulfoxide, m-cresol, and acetone.

[0019] Preferably, the mass fraction of the phenylacetylene-terminated thermosetting polyimide resin in the resin solution in step (1) is not less than 20%.

[0020] Preferably, prepreg A and prepreg B are prepared by conventional manual brushing, wet impregnation or film method.

[0021] Preferably, the resin content (i.e., the mass fraction of the resin in the prepreg) of prepreg A and B is not higher than 40%.

[0022] Preferably, the polyimide fiber in step (3) is obtained by solution spinning or melt spinning, with a melting point greater than 300 °C, and there is no special restriction on the type.

[0023] Preferably, in step (4), prepreg A is laid or wound with n layers for shaping, and prepreg B is laid or wound with 1 - n layers for shaping.

[0024] More preferably, in step (4), prepreg A is laid or wound with 2 layers for shaping, and prepreg B is laid or wound with 1 - 2 layers for shaping.

[0025] Preferably, the high-temperature curing procedure in step (5) is: keep warm at 180 - 220 °C for 0.5 - 3 h and 350 - 400 °C for 0.5 - 3 h in an autoclave or hot press, and set the pressure at 0.5 - 5 MPa.

[0026] More preferably, the high-temperature curing procedure in step (5) is: keep warm at 200 - 220 °C for 2 h and 370 - 380 °C for 3 h in an autoclave or hot press, and set the pressure at 1 - 2 MPa.

[0027] In a second aspect, the present invention provides a polyimide resin-based composite material prepared by the above preparation method.

[0028] The beneficial effects achieved by the present invention are as follows:

[0029] The polyimide resin-based composite material prepared by the present invention has an inner layer of quartz fiber or carbon fiber-reinforced polyimide resin-based composite material as the main body of the material, and an outer layer of polyimide fiber-reinforced polyimide resin-based composite material as a dense skin. During the forming process of the composite material, the polyimide resin in the outer dense skin has good wettability with the polyimide fiber reinforcement, and moreover, the polyimide fiber will also be extruded and deformed under high temperature and high pressure, forming a dense layer with thermoplastic polyimide fiber as the dense skeleton and thermosetting polyimide resin as the connecting matrix on the outer layer of the composite material, effectively improving the mechanical strength of the material at long-term high temperatures. The present invention improves the long-term high-temperature resistance performance of the polyimide resin-based composite material and avoids the problems of unstable high-temperature volatilization, large addition amount, and difficult uniform dispersion of traditional antioxidants. Specific embodiments

[0030] To make the technical features and advantages or technical effects in the above technical solutions of the present invention more obvious and understandable, the following will be described in detail with reference to embodiments.

[0031] Example 1

[0032] The phenylacetylene-terminated thermosetting polyimide was put into a DMAc solution, where the mass percentage content of the polyimide resin in the solution was 35%, and it was mixed until a homogeneous resin solution without precipitation was obtained, and a polyimide resin solution was prepared. The prepared resin solution was brushed on quartz cloth to prepare prepreg A, and the resin content was controlled at 40% by mass. The prepreg cloth was cut into small pieces of 300 mm * 300 mm. The prepared resin solution was brushed on polyimide fiber cloth to prepare prepreg B, and the resin content was controlled at 40% by mass. The prepreg cloth was cut into small pieces of 300 mm * 300 mm. First, 1 layer of prepreg B was laid in the mold, then 18 layers of prepreg A were laid, and finally 1 layer of prepreg B was laid, for a total of 20 layers. After pushing it into the press, the pressure of the press was set at 2 MPa, held at 220 °C for 2 hours, and then held at 380 °C for 3 hours for curing to obtain a polyimide resin-based composite material.

[0033] The flexural strength of the prepared polyimide resin-based composite material at 350 °C was 403 MPa, and the flexural strength of the composite material after being baked in an oven at 350 °C for 500 h was 291 MPa, and the retention rate of the long-term high-temperature flexural performance was 72.2%.

[0034] Example 2

[0035] The thermosetting polyimide capped with phenylethynyl was put into a DMAc solution, where the mass percentage content of the polyimide resin in the solution was 20%, and it was mixed until a homogeneous resin solution without precipitation was obtained, thus preparing a polyimide resin solution. The prepared resin solution was brushed on a quartz cloth to prepare prepreg A, and the resin content was controlled at 30% by mass. The prepreg cloth was cut into small pieces of 300 mm * 300 mm. The prepared resin solution was brushed on a polyimide fiber cloth to prepare prepreg B, and the resin content was controlled at 30% by mass. The prepreg cloth was cut into small pieces of 300 mm * 300 mm. On a flat mold, 1 layer of prepreg B was first laid, then 18 layers of prepreg A were laid, and finally 1 layer of prepreg B was laid, totaling 20 layers. It was placed in a autoclave, the vacuum bag pressure was -0.099 MPa, the pressure inside the autoclave was set at 5 MPa, and it was kept at 180 °C for 3 hours and then at 350 °C for 2 hours for curing to obtain a polyimide resin matrix composite material.

[0036] The bending strength of the prepared polyimide resin matrix composite material at 350 °C was 425 MPa, and the bending strength of the composite material after being baked in an oven at 350 °C for 500 h at 350 °C was 310 MPa, and the retention rate of the long-term high-temperature bending performance was 72.9%.

[0037] Example 3

[0038] The prepolymer of the PMR-type polyimide resin capped with phenylethynyl was put into an ethanol solution, where the mass percentage content of the PMR-type polyimide resin prepolymer in the solution was 50%, and it was mixed until a homogeneous resin solution without precipitation was obtained, thus preparing a polyimide resin solution. The prepared resin solution was brushed on a quartz cloth to prepare prepreg A, and the resin content was controlled at 40% by mass. The prepreg cloth was cut into small pieces of 300 mm * 300 mm. The prepared resin solution was brushed on a polyimide fiber cloth to prepare prepreg B, and the resin content was controlled at 40% by mass. The prepreg cloth was cut into small pieces of 300 mm * 300 mm. On a flat mold, 1 layer of prepreg B was first laid, then 18 layers of prepreg A were laid, and finally 1 layer of prepreg B was laid, totaling 20 layers. It was placed in a autoclave, the vacuum bag pressure was -0.099 MPa, the pressure inside the autoclave was set at 2 MPa, and it was kept at 200 °C for 1 hour and then at 400 °C for 1 hour for curing to obtain a polyimide resin matrix composite material.

[0039] The bending strength of the prepared polyimide resin matrix composite material at 350 °C was 447 MPa, and the bending strength of the composite material after being baked in an oven at 350 °C for 500 h at 350 °C was 342 MPa, and the retention rate of the long-term high-temperature bending performance was 76.5%.

[0040] Comparative Example 1

[0041] The phenylacetylene-terminated thermosetting polyimide was put into a DMAc solution, where the mass percentage content of the polyimide resin in the solution was 35%. After mixing until a homogeneous resin solution without precipitation was obtained, a polyimide resin solution was prepared. The prepared resin solution was brushed on a quartz cloth to prepare prepreg A, and the resin content was controlled at 40% by mass. The prepreg cloth was cut into small pieces of 300 mm * 300 mm. 20 layers of prepreg A were laid in a mold. After pushing it into a press, the pressure of the press was set at 2 MPa, and it was kept at 220 °C for 2 hours and then at 380 °C for 3 hours for curing to obtain a polyimide resin-based composite material.

[0042] The flexural strength of the prepared polyimide resin-based composite material at 350 °C was 435 MPa. After the composite material was baked in an oven at 350 °C for 500 h, the flexural strength at 350 °C was 247 MPa, and the retention rate of the long-term high-temperature flexural performance was 56.8%.

[0043] Comparative Example 2

[0044] The prepolymer of the phenylacetylene-terminated PMR-type polyimide resin was put into an ethanol solution, where the mass percentage content of the PMR-type polyimide resin prepolymer in the solution was 50%. After mixing until a homogeneous resin solution without precipitation was obtained, a polyimide resin solution was prepared. The prepared resin solution was brushed on a quartz cloth to prepare prepreg A, and the resin content was controlled at 40% by mass. The prepreg cloth was cut into small pieces of 300 mm * 300 mm. 20 layers of prepreg A were laid in a mold. It was put into a autoclave, the vacuum bag pressure was -0.099 MPa, the pressure inside the autoclave was set at 2 MPa, and it was kept at 200 °C for 1 hour and then at 400 °C for 1 hour for curing to obtain a polyimide resin-based composite material.

[0045] The flexural strength of the prepared polyimide resin-based composite material at 350 °C was 482 MPa. After being baked in an oven at 350 °C for 500 h, the flexural strength at 350 °C was 295 MPa, and the retention rate of the long-term high-temperature flexural performance was 61.2%.

[0046] From the comparison of the test results of the polyimide resin-based composite materials prepared in the examples and comparative examples, it can be seen that by the simple strategy of forming a dense skin of a polyimide fiber-reinforced polyimide resin composite material on the outer layer in the method of the present invention, not only the excellent high-temperature mechanical properties of the quartz fiber or carbon fiber-reinforced thermosetting polyimide resin composite material are retained, but also the retention rate of the high-temperature flexural strength of the composite material at long-term high temperature is effectively improved, and the service life of the material in a long-term high-temperature environment is significantly extended.

[0047] Although the present invention has been disclosed above by way of embodiments, it is not intended to limit the present invention. Any appropriate modifications or equivalent replacements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope of the present invention. The protection scope of the present invention shall be subject to what is defined by the claims.

Claims

1. A method for preparing a polyimide resin-based composite material, characterized in that: The following steps are involved: (1) using a thermosetting polyimide resin terminated with phenylethynyl as a matrix, mixing it with an organic solvent, and preparing a resin solution; (2) Based on the above resin solution, a quartz fiber or carbon fiber reinforced polyimide resin prepreg, i.e., prepreg A, is prepared using quartz fiber or carbon fiber as a reinforcement; (3) Based on the above resin solution, a polyimide fiber-reinforced polyimide resin prepreg, i.e., prepreg B, is prepared using polyimide fiber as a reinforcement; (4) Prepreg A is used as the main prepreg and is draped or wound to shape; prepreg B is used as the outer layer prepreg and is wrapped around the draped or wound prepreg A as the outer layer; (5) All prepregs wrapped by the outer layer are cured at high temperature to obtain a polyimide composite material that is resistant to long-term high temperature.

2. The preparation method according to claim 1, characterized in that The phenylethynyl-terminated thermosetting polyimide resin in step (1) is a prepolymer or a polyimide oligomer of a PMR type polyimide resin; the prepolymer of the PMR type polyimide resin is obtained by reacting an aromatic tetracarboxylic acid dimethyl ester or a monoalkyl phthalate with an aromatic diamine, and is soluble in a lower alcohol; the polyimide oligomer is an imidized soluble polyimide, and is soluble in a polar organic solvent.

3. The preparation method according to claim 1, characterized in that: The organic solvent in step (1) is selected from one or more of methanol, ethanol, isopropanol, ethylene glycol, glycerol, N,N-dimethylacetamide, dimethylformamide, dioxane, dichloromethane, tetrahydrofuran, dimethyl sulfoxide, m-cresol, and acetone.

4. The preparation method according to claim 1, characterized in that: In step (1), the mass fraction of the thermosetting polyimide resin terminated with phenylethynyl groups in the resin solution is not less than 20%.

5. The preparation method according to claim 1, characterized in that: The glue content of prepregs A and B is not higher than 40%.

6. The preparation method according to claim 1, characterized in that: The polyimide fiber in step (3) is obtained by solution spinning or melt spinning, and has a melting point greater than 300°C.

7. The preparation method according to claim 1, characterized in that: In step (4), prepreg A is coated or wound with n layers to form a shape, and prepreg B is coated or wound with 1-n layers to form a shape.

8. The preparation method according to claim 1, characterized in that: The high temperature curing procedure in step (5) is: keep warm at 180-220°C for 0.5-3h, keep warm at 350-400°C for 0.5-3h in an autoclave or hot mold press, and set the pressure to 0.5-5MPa.

9. The preparation method according to claim 8, characterized in that: The high temperature curing procedure in step (5) is: keeping the temperature at 200-220° C. for 2 h, and keeping the temperature at 370-380° C. for 3 h in an autoclave or hot mold press, and setting the pressure at 1-2 MPa.

10. A polyimide resin-based composite material, characterized in that: The method is prepared by any one of claims 1 to 9.