A method for preparing a continuous fiber-reinforced high interlaminar shear liquid crystal polymer composite

Abstract

The application discloses a preparation method of a continuous fiber reinforced high interlaminar shear liquid crystal polymer composite material, and the preparation method is as follows: a low-melting-point liquid crystal polymer film is stacked on and under a continuous fiber bundle to form a laminated body; the formed laminated body is stacked on and under a high-melting-point liquid crystal polymer film respectively to form a secondary laminated body; and the formed secondary laminated body is pre-pressed and formed through a hot static pressure process. The fiber bundle after being pressed through the static pressure process is subjected to heat treatment together with a liquid crystal polymer film laminated body in which a toughening agent is dispersed to obtain the continuous fiber reinforced high interlaminar shear liquid crystal polymer composite material. The application uses the fiber bundle and the liquid crystal polymer film to be hot statically pressed, and then the mechanical properties of the composite material are improved through a heat treatment process, so that the interlaminar shear strength of the obtained continuous fiber reinforced liquid crystal polymer composite material is greater than 80 MPa, and the continuous fiber reinforced liquid crystal polymer composite material can be used for large structural parts.

Description

Technical Field

[0001] This invention relates to a composition, specifically to a method for preparing a continuous fiber-reinforced high-layer interlayer shear liquid crystal polymer composite material, belonging to the field of composite materials. Background Technology

[0002] Resin-based composite materials, as a crucial cornerstone of modern industry and high-tech development, are indispensable basic materials for national security and the national economy. In recent years, with the vigorous development of my country's aerospace industry, advanced resin-based composite materials for space applications have developed rapidly, creating a significant demand for high-performance, lightweight, and large-size resin-based composite component manufacturing technologies.

[0003] Thermotropic liquid crystal polymers (LCPs) are high-performance polymer materials, typically known for their high strength, high modulus, excellent melt processing characteristics, inherent flame retardancy, low water absorption, chemical corrosion resistance, good radiation resistance, and resistance to high and low temperature impacts, as well as their numerous applications at high temperatures. Therefore, they have wide applications in aerospace, specialized industries, and other fields. However, for large components, the strength of pure LCP resin or chopped fiber-reinforced LCP composites is still insufficient; and due to the rapid crystallization rate of LCP materials, it is difficult to injection mold large components. Furthermore, the bonding strength between liquid crystal polymers and inorganic fibers is also somewhat insufficient. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing a continuous fiber-reinforced liquid crystal polymer composite material with interlayer shear, so as to facilitate the preparation of large components.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] The present invention discloses a method for preparing a continuous fiber-reinforced interlayer shear liquid crystal polymer composite material, the preparation method of which is as follows:

[0007] (1) A continuous fiber bundle is stacked on top of a low-melting-point liquid crystal polymer film to form a laminate;

[0008] (2) High melting point liquid crystal polymer films are then stacked on top and bottom of the laminate formed in step (1) to form a secondary laminate;

[0009] (3) The secondary laminate formed in step (2) is pre-pressed using a hot static pressing process. The hot static pressing process is carried out in an inert gas medium for 1–10 minutes. The inert gas is at least one of nitrogen, argon, and carbon dioxide, and the oxygen content is below 20 PPM. If the oxygen content is too high, the content of small molecules in the prepared liquid crystal polymer composite material will be too high, resulting in gaps between the fiber bundles and the liquid crystal polymer, and the tensile strength will be too low.

[0010] The processing temperature used in the hot isostatic pressing process is in the range from the melting point of the liquid crystal polymer to 20°C above the melting point of the liquid crystal polymer. The pressure used is in the range from 5 MPa to 30 MPa.

[0011] (4) The fiber bundle after the isostatic pressing process is laminated with the liquid crystal polymer film layer containing the toughening agent, and then subjected to heat treatment to obtain a continuous fiber-reinforced high interlaminar shear liquid crystal polymer composite. The lamination is subjected to heat treatment in a vacuum or an inert gas medium, and the oxygen content is controlled to be less than or equal to 20 ppm.

[0012] The heat treatment is carried out for 4 to 12 hours in an inert gas stream or a vacuum condition, the inert gas being at least one of nitrogen, argon and carbon dioxide, and the gas flow rate being greater than 10 mL / min; the vacuum condition being a vacuum degree less than or equal to 100 Pa, preferably less than 20 Pa. If the gas flow rate is too small or the vacuum degree is insufficient, the content of small molecules in the prepared liquid crystal polymer composite will be too high, and the tensile strength will be too low. The processing temperature used in the heat treatment is in the range from 100°C below the melting point of the liquid crystal polymer to 20°C below the melting point of the liquid crystal polymer. The processing temperature of the heat treatment is in the range from 230°C to 320°C.

[0013] In the continuous fiber-reinforced high interlaminar shear liquid crystal polymer composite of the present application, the fiber bundle accounts for greater than or equal to 25% and less than 65% of the weight of the composite.

[0014] The continuous fiber bundle in the present application is selected from one or both of glass fiber and carbon fiber.

[0015] The glass fiber in the present application can be selected from E-glass fiber, i.e. alkali-free glass, which is an aluminoborosilicate glass fiber. It has good electrical insulation performance and good strength, and the diameter is in the range from 5 to 20 microns.

[0016] The carbon fiber in the present application refers to high-strength high-modulus fiber with a carbon content of more than 90%, which can be selected from high-strength carbon fiber obtained by carbonization of polyacrylonitrile fiber, viscose-based fiber and pitch-based fiber, and the diameter is in the range from 5 to 15 microns.

[0017] The liquid crystal polymer in the present application is a liquid crystal polyester or polyester amide using aromatic compounds as raw monomers, and is preferably a wholly aromatic liquid crystal polyester or polyester amide using only aromatic compounds as raw monomers.

[0018] A typical example of the liquid crystal polymer of the present application is a liquid crystal polyester formed by polymerization of aromatic hydroxyl carboxylic acid and at least one compound selected from the group consisting of aromatic hydroxyl amine, aromatic diamine, aromatic dicarboxylic acid and aromatic diol.

[0019] Part or all of the aromatic hydroxyl carboxylic acid, aromatic hydroxyl amine, aromatic diamine, aromatic dicarboxylic acid, aromatic diol can be independently a polymerizable derivative thereof.

[0020] As the polymerizable derivative of the compound having a hydroxyl group such as aromatic hydroxyl carboxylic acid, aromatic hydroxyl amine, aromatic diamine, aromatic diol, acylate formed by acylating the hydroxyl group to acyloxy can be exemplified.

[0021] In the above combination of each repeating unit constituting the liquid crystal polymer:

[0022] The aromatic hydroxyl carboxylic acid is selected from the repeating unit of p-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid; the aromatic dicarboxylic acid is selected from the repeating unit of terephthalic acid, isophthalic acid, 2,6-naphthalene dicarboxylic acid, preferably from the repeating unit of terephthalic acid, isophthalic acid; the aromatic diol is selected from the repeating unit of hydroquinone, 2,6-naphthalene diol, 4,4'-dihydroxybiphenyl, preferably from the repeating unit of hydroquinone, 4,4'-dihydroxybiphenyl; the aromatic hydroxyl amine is selected from the repeating unit of p-aminophenol, p-aminonaphthol, preferably from the repeating unit of p-aminophenol; the aromatic diamine is selected from the repeating unit of p-phenylenediamine, 4,4'-diphenyl, 2,6-naphthalene diamine.

[0023] The liquid crystal polymer of the present application contains at least one repeating unit of aromatic hydroxyl carboxylic acid.

[0024] The liquid crystal polymer film dispersed with the toughening agent in the present application can be obtained by mixing the toughening agent with the liquid crystal polymer by a known blending method, so that the toughening agent is uniformly dispersed in the liquid crystal polymer. The obtained liquid crystal polymer dispersed with the toughening agent is blown into a film or extruded into a biaxially stretched film by a known extrusion film forming method, to obtain a liquid crystal polymer film material dispersed with the toughening agent. The thickness of the liquid crystal polymer film material is between 20-200 microns.

[0025] The melt viscosity of the liquid crystal polymer is between 30-100 Pa·s. The melting point of the low melting point liquid crystal polymer film is between 260-290°C; the melting point of the high melting point liquid crystal polymer film is between 300-350°C.

[0026] The present application uses continuous fibers as the reinforcing phase, which is compounded with the LCP film to improve the bonding force between the liquid crystal polymer and the inorganic fibers, and then the LCP material is solid-phase polymerized to be hot-pressed to prepare a continuous fiber reinforced high interlaminar shear LCP composite material. After the fiber bundle is hot isostatic pressed with the liquid crystal polymer film, the mechanical properties of the composite material are improved by a heat treatment process, and the interlaminar shear strength of the obtained continuous fiber reinforced liquid crystal polymer composite material is greater than 80 MPa, which can be used for large structural parts. DETAILED DESCRIPTION

[0027] The present application is further illustrated by the following examples and comparative examples, and should not be limited to the specific details of the following examples without departing from the spirit of the present application.

[0028] Product performance test method:

[0029] The melting point (Tm) of the liquid crystal polymer was tested using a differential scanning calorimeter (DSC 8000, PerkinElmer, USA) according to the method of ASTM D3418. m The melt viscosity (MV) of the liquid crystal polymer was tested using a capillary rheometer (RH 2200, Malvern, UK) according to the method of ASTM D3835. The tensile strength and tensile modulus of the liquid crystal polymer were tested using a universal testing machine according to the method of GBT 3354. The bending strength and bending modulus of the liquid crystal polymer were tested using a universal testing machine according to the method of GB / T 3356. The heat distortion temperature of the liquid crystal polymer was tested using a heat distortion Vicat tester according to the method of GB / T 1634. The interlayer shear strength of the liquid crystal polymer was tested using an interlayer bonding strength tester according to the method of GBT 1450.

[0030] Example 1:

[0031] First, p-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid and acetic anhydride were reacted at a constant temperature of 120-130°C for 1 hour, then the temperature was increased to 185-195°C within 2 hours, and then reacted at a constant temperature for 0.5-1 hour. The acetylation reaction was completed. Then, the acetic ester obtained by acetylation reaction was subjected to melt polycondensation reaction, and the polymerization temperature was increased to the predetermined temperature within 3 hours, so that the polymerization reaction was continuously carried out. When the torque of the stirrer reached a predetermined level, nitrogen was immediately introduced to terminate the polymerization reaction. The nitrogen gas pressure was increased to 2 kg / cm 2 The monomer ratio for preparing the above liquid crystal polymer is as follows: p-hydroxybenzoic acid 73 mol%, 6-hydroxy-2-naphthoic acid 27 mol%. The melting point is about 280°C, and the viscosity is about 55 Pa·s. The liquid crystal polymer obtained by polymerization was extrusion blow molded into a film with a thickness of about 50 microns. The die temperature was 290°C, the die diameter was 30 mm, the die gap was 0.7 mm, and the blow-up ratio was 6.2. The liquid crystal polymer film obtained by blow molding is referred to as LCP film 1.

[0032] A liquid crystal polymer was synthesized by the same polymerization process, and the monomer ratio was as follows: 42 mol% of p-hydroxybenzoic acid, 22 mol% of 6-hydroxy-2-naphthoic acid, 18 mol% of hydroquinone, and 18 mol% of terephthalic acid. The melting point thereof was about 340°C, and the viscosity thereof was about 42 Pa-s. The liquid crystal polymer was extrusion blow molded into a film. The film thickness was about 50 micrometers. The die temperature was 350°C, the die diameter was 30 mm, the die gap was 0.7 mm, and the blow-up ratio was 6.2. The liquid crystal polymer film obtained by the blow molding was referred to as LCP film 2.

[0033] The carbon fiber bundle (SYT55S, Zhongfu Shenying Carbon Co., Ltd.) was laid flat and then the LCP film 1 was stacked thereon, and then the LCP film 2 was stacked thereon again. The weight ratio of the carbon fiber bundle to the LCP film was 55:45. Then, the mold cavity was replaced with nitrogen, and the mold cavity was sealed, and then slowly heated to 345°C. The hot isostatic pressing process was performed in a nitrogen medium for 3 minutes, and the oxygen content was controlled to be less than 20 PPM.

[0034] Subsequently, the temperature of the mold cavity was reduced to 260°C, and the heat treatment of the carbon fiber and the liquid crystal polymer film laminate after the isostatic pressing process was started. After the temperature was reduced to 260°C, nitrogen was discharged, and vacuum was applied, and the vacuum degree was about 50 Pa, and the oxygen content was controlled to be less than 20 ppm. The entire heat treatment process lasted for 8 hours, and finally a carbon fiber-reinforced high interlaminar shear liquid crystal polymer composite material was obtained, and the performance thereof was shown in Table 1.

[0035] Example 2:

[0036] The carbon fiber bundle (SYT55S, Zhongfu Shenying Carbon Co., Ltd.) was laid flat and then the LCP film 1 was stacked thereon, and then the LCP film 2 was stacked thereon again. The weight ratio of the carbon fiber bundle to the LCP film was 55:45. Then, the mold cavity was replaced with nitrogen, and the mold cavity was sealed, and then slowly heated to 345°C. The hot isostatic pressing process was performed in a nitrogen medium for 3 minutes, and the oxygen content was controlled to be less than 20 PPM.

[0037] Subsequently, the temperature of the mold cavity was reduced to 240°C, and the heat treatment of the carbon fiber and the liquid crystal polymer film laminate after the isostatic pressing process was started. After the temperature was reduced to 240°C, nitrogen was continuously introduced, and nitrogen was discharged on the other side of the mold cavity, and the nitrogen flow was about 20 mL / min, and the oxygen content was controlled to be less than 20 ppm. The entire heat treatment process lasted for 12 hours, and finally a carbon fiber-reinforced high interlaminar shear liquid crystal polymer composite material was obtained, and the performance thereof was shown in Table 1.

[0038] Example 3:

[0039] The carbon fiber bundle (SYT55S, Zhongfushenying Carbon Fiber Co., Ltd.) was laid flat and stacked with LCP film 1 on top and bottom, and then stacked with LCP film 2 again. The weight ratio of the carbon fiber bundle to the LCP film was 55:45. The mold cavity was then replaced with nitrogen, and the mold cavity was then sealed, and then slowly heated to 345°C, and the hot isostatic pressing process was performed in a nitrogen medium for 1 minute, with the oxygen content controlled to be below 20 PPM.

[0040] After that, the temperature of the mold cavity was lowered to 260°C, and the heat treatment of the carbon fiber bundle and the liquid crystal polymer film laminated body after the isostatic pressing process was started. After the temperature was lowered to 260°C, nitrogen was continuously introduced, and nitrogen was discharged on the other side of the mold cavity, with a nitrogen flow rate of about 20 mL / min, and the oxygen content was controlled to be below 20 ppm. The entire heat treatment process lasted for 8 hours, and finally a carbon fiber-reinforced high interlaminar shear liquid crystal polymer composite material was obtained, and its performance is shown in Table 1.

[0041] Example 4:

[0042] The glass fiber bundle (362A, China Jushi Co., Ltd.) was laid flat and stacked with LCP film 1 on top and bottom, and then stacked with LCP film 2 again. The weight ratio of the glass fiber bundle to the LCP film was 55:45. The mold cavity was then replaced with nitrogen, and the mold cavity was then sealed, and then slowly heated to 340°C, and the hot isostatic pressing process was performed in a nitrogen medium for 8 minutes, with the oxygen content controlled to be below 20 PPM.

[0043] After that, the temperature of the mold cavity was lowered to 280°C, and the heat treatment of the carbon fiber bundle and the liquid crystal polymer film laminated body after the isostatic pressing process was started. After the temperature was lowered to 280°C, nitrogen was continuously introduced, and nitrogen was discharged on the other side of the mold cavity, with a nitrogen flow rate of about 20 mL / min, and the oxygen content was controlled to be below 20 ppm. The entire heat treatment process lasted for 6 hours, and finally a carbon fiber-reinforced high interlaminar shear liquid crystal polymer composite material was obtained, and its performance is shown in Table 1.

[0044] Example 5:

[0045] The carbon fiber bundle was laid flat and stacked with LCP film 1 on top and bottom, and then stacked with LCP film 2 again. The weight ratio of the carbon fiber bundle to the LCP film was 55:45. The mold cavity was then replaced with nitrogen, and the mold cavity was then sealed, and then slowly heated to 345°C, and the hot isostatic pressing process was performed in a nitrogen medium for 3 minutes, with the oxygen content controlled to be below 20 PPM.

[0046] After that, the temperature of the mold cavity is decreased to 240°C, and the heat treatment of the carbon fiber bundle and the liquid crystal polymer film laminated body after the static pressure process is started. After the temperature is decreased to 240°C, nitrogen is continuously introduced, and the nitrogen is discharged from the other side of the mold cavity. The flow rate of the nitrogen is about 100 mL / min, and the oxygen content is controlled to be less than 20 ppm. The entire heat treatment process lasts for 5 hours, and finally a high interlaminar shear liquid crystal polymer composite material reinforced by mixed fibers is obtained, and the performance is shown in Table 1.

[0047] Example 6:

[0048] The carbon fiber bundle (SYT55S, Zhongfushenying Carbon Fiber Co., Ltd.) is laid and then the LCP film 1 is stacked on top of the carbon fiber bundle, and then the LCP film 2 is stacked again. The weight ratio of the carbon fiber bundle to the LCP film is 55:45. Then, the mold cavity is replaced with nitrogen, and then the mold cavity is sealed, and then slowly heated to 345°C. The hot static pressure process is performed in a nitrogen medium for 3 minutes, and the oxygen content is controlled to be less than 20 PPM.

[0049] After that, the temperature of the mold cavity is decreased to 300°C, and the heat treatment of the carbon fiber bundle and the liquid crystal polymer film laminated body after the static pressure process is started. After the temperature is decreased to 300°C, nitrogen is continuously introduced, and the nitrogen is discharged from the other side of the mold cavity. The flow rate of the nitrogen is about 100 mL / min, and the oxygen content is controlled to be less than 20 ppm. The entire heat treatment process lasts for 5 hours, and finally a high interlaminar shear liquid crystal polymer composite material reinforced by mixed fibers is obtained, and the performance is shown in Table 1.

[0050] Comparative Example 1:

[0051] The carbon fiber bundle (SYT55S, Zhongfushenying Carbon Fiber Co., Ltd.) is laid and then the LCP film 1 is stacked on top of the carbon fiber bundle, and then the LCP film 2 is stacked again. The weight ratio of the carbon fiber bundle to the LCP film is 55:45. Then, the mold cavity is replaced with nitrogen, and then the mold cavity is sealed, and then slowly heated to 345°C. The hot static pressure process is performed in a nitrogen medium for 3 minutes, and the oxygen content is controlled to be less than 20 PPM.

[0052] After that, the temperature of the mold cavity is decreased to 300°C, and the heat treatment of the carbon fiber bundle and the liquid crystal polymer film laminated body after the static pressure process is started. After the temperature is decreased to 300°C, nitrogen is continuously introduced, and the nitrogen is discharged from the other side of the mold cavity. The flow rate of the nitrogen is about 100 mL / min, and the oxygen content is controlled to be less than 20 ppm. The entire heat treatment process lasts for 5 hours, and finally a high interlaminar shear liquid crystal polymer composite material reinforced by mixed fibers is obtained, and the performance is shown in Table 1.

[0053] Comparative Example 2:

[0054] The carbon fiber bundle (SYT55S, Zhongfu Haohua Carbon Co., Ltd.) was laid flat and then LCP film 1 was stacked on top and bottom, and then LCP film 2 was stacked again. The weight ratio of the carbon fiber bundle to the LCP film was 55:45. The mold cavity was then replaced with nitrogen, and the mold cavity was then sealed, and then slowly heated to 345°C, and the hot isostatic pressing process was carried out in a nitrogen medium for 30 minutes, with the oxygen content controlled to be below 20 PPM.

[0055] After that, the temperature of the mold cavity was lowered to 240°C, and the heat treatment of the carbon fiber bundle and the liquid crystal polymer film laminated body after the isostatic pressing process was started. After the temperature was lowered to 240°C, nitrogen was continuously introduced, and nitrogen was discharged on the other side of the mold cavity, with a nitrogen flow rate of about 20 mL / min, and the oxygen content was controlled to be below 20 ppm. The entire heat treatment process lasted for 12 hours, and finally a carbon fiber reinforced high interlaminar shear liquid crystal polymer composite material was obtained, and its performance is shown in Table 1.

[0056] Comparative Example 3:

[0057] The carbon fiber bundle (SYT55S, Zhongfu Haohua Carbon Co., Ltd.) was laid flat and then LCP film 1 was stacked on top and bottom, and then LCP film 2 was stacked again. The weight ratio of the carbon fiber bundle to the LCP film was 55:45. The mold cavity was then replaced with nitrogen, and the mold cavity was then sealed, and then slowly heated to 380°C, and the hot isostatic pressing process was carried out in a nitrogen medium for 1 minute, with the oxygen content controlled to be below 20 PPM.

[0058] After that, the temperature of the mold cavity was lowered to 260°C, and the heat treatment of the carbon fiber bundle and the liquid crystal polymer film laminated body after the isostatic pressing process was started. After the temperature was lowered to 260°C, nitrogen was continuously introduced, and nitrogen was discharged on the other side of the mold cavity, with a nitrogen flow rate of about 20 mL / min, and the oxygen content was controlled to be below 20 ppm. The entire heat treatment process lasted for 4 hours, and finally a carbon fiber reinforced high interlaminar shear liquid crystal polymer composite material was obtained, and its performance is shown in Table 1.

[0059] Comparative Example 4:

[0060] The carbon fiber bundle (SYT55S, Zhongfu Haohua Carbon Co., Ltd.) was laid flat and then LCP film 1 was stacked on top and bottom, and then LCP film 2 was stacked again. The weight ratio of the carbon fiber bundle to the LCP film was 55:45. The mold cavity was then replaced with nitrogen, and the mold cavity was then sealed, and then slowly heated to 345°C, and the hot isostatic pressing process was carried out in a nitrogen medium for 3 minutes, with the oxygen content controlled to be below 120 PPM.

[0061] After that, the temperature of the mold cavity is decreased to 250°C, and the heat treatment of the carbon fiber bundle and the liquid crystal polymer film laminated body after the static pressure process is started. After the temperature is decreased to 250°C, nitrogen is continuously introduced, and nitrogen is discharged from the other side of the mold cavity. The flow rate of nitrogen is about 20 mL / min, and the oxygen content is controlled to be less than 20 ppm. The entire heat treatment process lasts for 8 hours, and finally the carbon fiber reinforced high interlaminar shear liquid crystal polymer composite material is obtained. The performance is shown in Table 1.

[0062] Comparative Example 5:

[0063] The carbon fiber bundle (SYT55S, Zhongfushenying Carbon Fiber Co., Ltd.) is laid flat and stacked with LCP film 1 on top and bottom, and then stacked with LCP film 2 again. The weight ratio of the carbon fiber bundle to the LCP film is 55:45. Then the mold cavity is replaced with nitrogen, and the mold cavity is sealed. Then it is slowly heated to 345°C, and the hot static pressure process is carried out in a nitrogen medium for 3 minutes, with the oxygen content controlled to be less than 20 PPM.

[0064] After that, the temperature of the mold cavity is decreased to 240°C, and the heat treatment of the carbon fiber bundle and the liquid crystal polymer film laminated body after the static pressure process is started. After the temperature is decreased to 240°C, nitrogen is continuously introduced, and nitrogen is discharged from the other side of the mold cavity. The flow rate of nitrogen is about 20 mL / min, and the oxygen content is controlled to be less than 120 ppm. The entire heat treatment process lasts for 8 hours, and finally the carbon fiber reinforced high interlaminar shear liquid crystal polymer composite material is obtained. The performance is shown in Table 1.

[0065] Comparative Example 6:

[0066] The carbon fiber bundle (SYT55S, Zhongfushenying Carbon Fiber Co., Ltd.) is laid flat and stacked with LCP film 1 on top and bottom, and then stacked with LCP film 2 again. The weight ratio of the carbon fiber bundle to the LCP film is 55:45. Then the mold cavity is replaced with nitrogen, and the mold cavity is sealed. Then it is slowly heated to 345°C, and the hot static pressure process is carried out in a nitrogen medium for 5 minutes, with the oxygen content controlled to be less than 20 PPM.

[0067] After that, the temperature of the mold cavity is decreased to 220°C, and the heat treatment of the carbon fiber bundle and the liquid crystal polymer film laminated body after the static pressure process is started. After the temperature is decreased to 220°C, nitrogen is continuously introduced, and nitrogen is discharged from the other side of the mold cavity. The flow rate of nitrogen is about 20 mL / min, and the oxygen content is controlled to be less than 20 ppm. The entire heat treatment process lasts for 8 hours, and finally the carbon fiber reinforced high interlaminar shear liquid crystal polymer composite material is obtained. The performance is shown in Table 1.

[0068] Comparative Example 7:

[0069] The carbon fiber bundle (SYT55S, Zhongfu Haohua Carbon Co., Ltd.) was laid flat and then LCP film 1 was stacked on top and bottom, and then LCP film 2 was stacked again. The weight ratio of the carbon fiber bundle to the LCP film was 55:45. The mold cavity was then replaced with nitrogen, and the mold cavity was then sealed, and then slowly heated to 345°C, and the hot isostatic pressing process was carried out in a nitrogen medium for 3 minutes, with the oxygen content controlled to be below 20 PPM.

[0070] After that, the temperature of the mold cavity was lowered to 300°C, and the heat treatment of the carbon fiber bundle and the liquid crystal polymer film laminated body after the isostatic pressing process was started. After the temperature was lowered to 300°C, nitrogen was continuously introduced, and nitrogen was discharged on the other side of the mold cavity, with a nitrogen flow rate of about 20 mL / min, and the oxygen content was controlled to be below 20 ppm. The entire heat treatment process lasted for 3 hours, and finally a carbon fiber reinforced high interlaminar shear liquid crystal polymer composite material was obtained, and its performance is shown in Table 1.

[0071] Comparative Example 8:

[0072] The carbon fiber bundle (SYT55S, Zhongfu Haohua Carbon Co., Ltd.) was laid flat and then LCP film 1 was stacked on top and bottom, and then LCP film 2 was stacked again. The weight ratio of the carbon fiber bundle to the LCP film was 55:45. The mold cavity was then replaced with nitrogen, and the mold cavity was then sealed, and then slowly heated to 345°C, and the hot isostatic pressing process was carried out in a nitrogen medium for 3 minutes, with the oxygen content controlled to be below 20 PPM.

[0073] After that, the temperature of the mold cavity was lowered to 300°C, and the heat treatment of the carbon fiber bundle and the liquid crystal polymer film laminated body after the isostatic pressing process was started. After the temperature was lowered to 300°C, nitrogen was continuously introduced, and nitrogen was discharged on the other side of the mold cavity, with a nitrogen flow rate of about 20 mL / min, and the oxygen content was controlled to be below 20 ppm. The entire heat treatment process lasted for 3 hours, and finally a carbon fiber reinforced high interlaminar shear liquid crystal polymer composite material was obtained, and its performance is shown in Table 1.

[0074] Comparative Example 9:

[0075] The carbon fiber bundle (SYT55S, Zhongfu Haohua Carbon Co., Ltd.) was laid flat and then LCP film 1 was stacked on top and bottom, and then LCP film 2 was stacked again. The weight ratio of the carbon fiber bundle to the LCP film was 55:45. The mold cavity was then replaced with nitrogen, and the mold cavity was then sealed, and then slowly heated to 345°C, and the hot isostatic pressing process was carried out in a nitrogen medium for 3 minutes, with the oxygen content controlled to be below 20 PPM.

[0076] After that, the temperature of the mold cavity is decreased to 240°C, and the heat treatment of the carbon fiber bundle and the liquid crystal polymer film laminated body after the static pressure process is started. After the temperature is decreased to 240°C, nitrogen is continuously introduced, and nitrogen is discharged from the other side of the mold cavity, the nitrogen flow is about 20 mL / min, and the oxygen content is controlled to be less than 20 ppm. The whole heat treatment process lasts for 16 hours, and finally the carbon fiber reinforced high interlaminar shear liquid crystal polymer composite material is obtained, and its performance is shown in Table 1.

[0077] Comparative Example 10:

[0078] The carbon fiber bundle (SYT55S, Zhongfushenying Carbon Fiber Co., Ltd.) is laid and then stacked with LCP film 1 up and down, and then stacked with LCP film 2 again. The weight ratio of the carbon fiber bundle to the LCP film is 55:45. Then the mold cavity is replaced with nitrogen, and then the mold cavity is sealed, and then slowly heated to 345°C, and the hot static pressure process is carried out in a nitrogen medium for 3 minutes, and the oxygen content is controlled to be less than 20 PPM.

[0079] After that, the temperature of the mold cavity is decreased to 330°C, and the heat treatment of the carbon fiber bundle and the liquid crystal polymer film laminated body after the static pressure process is started. After the temperature is decreased to 330°C, nitrogen is continuously introduced, and nitrogen is discharged from the other side of the mold cavity, the nitrogen flow is about 20 mL / min, and the oxygen content is controlled to be less than 20 ppm. The whole heat treatment process lasts for 4 hours, and finally the carbon fiber reinforced high interlaminar shear liquid crystal polymer composite material is obtained, and its performance is shown in Table 1.

[0080] Comparative Example 11:

[0081] The carbon fiber bundle (SYT55S, Zhongfushenying Carbon Fiber Co., Ltd.) is laid and then stacked with LCP film 1 up and down, and then stacked with LCP film 2 again. The weight ratio of the carbon fiber bundle to the LCP film is 20:80. Then the mold cavity is replaced with nitrogen, and then the mold cavity is sealed, and then slowly heated to 345°C, and the hot static pressure process is carried out in a nitrogen medium for 3 minutes, and the oxygen content is controlled to be less than 20 PPM.

[0082] After that, the temperature of the mold cavity is decreased to 260°C, and the heat treatment of the carbon fiber bundle and the liquid crystal polymer film laminated body after the static pressure process is started. After the temperature is decreased to 260°C, nitrogen is continuously introduced, and nitrogen is discharged from the other side of the mold cavity, the nitrogen flow is about 20 mL / min, and the oxygen content is controlled to be less than 20 ppm. The whole heat treatment process lasts for 12 hours, and finally the carbon fiber reinforced high interlaminar shear liquid crystal polymer composite material is obtained, and its performance is shown in Table 1.

[0083] Comparative Example 12:

[0084] The carbon fiber bundle (SYT55S, Zhongfugongying Carbon Fiber Co., Ltd.) is laid flat, and the LCP film 1 is stacked on top of it, and then the LCP film 2 is stacked again. The weight ratio of the carbon fiber bundle to the LCP film is 70:30. Then the mold cavity is replaced with nitrogen, and then the mold cavity is sealed, and then slowly heated to 345℃, and the hot isostatic pressing process is carried out in a nitrogen medium for 3 minutes, and the oxygen content is controlled to be below 20PPM.

[0085] Then the temperature of the mold cavity is reduced to 260℃, and the hot treatment of the carbon fiber bundle and the liquid crystal polymer film laminated body after the isostatic pressing process is started. After the temperature is reduced to 260℃, nitrogen is continuously introduced, and nitrogen is discharged on the other side of the mold cavity, the nitrogen flow is about 20mL / min, and the oxygen content is controlled to be below 20ppm. The whole heat treatment process lasts for 12 hours, and finally the composite material cannot be formed.

[0086] Table 1 summarizes the properties of the liquid crystal polymer composite materials of Examples 1-6 and Comparative Examples 1-12.

[0087]

[0088] The properties of the continuous fiber reinforced high interlaminar shear liquid crystal polymer composite materials prepared in Examples 1-6 and Comparative Examples 1-12 are shown in Table 1. The liquid crystal polymer film penetrates into the gap between the fiber bundle and fully contacts and combines with the fiber bundle during the hot isostatic pressing process, and the liquid crystal polymer itself is fused into a continuous phase matrix of the composite material, and then the liquid crystal polymer is subjected to high temperature heat treatment to improve the polymerization degree of the liquid crystal polymer to achieve the required molecular weight. Compared with Comparative Example 3 and Comparative Example 1, the temperature during the hot isostatic pressing process is too low, which can make the liquid crystal polymer and the fiber weakly combined, and the matrix itself is not fully fused, resulting in a poor overall strength of the obtained composite material. By comparing Comparative Example 3 with Comparative Examples 2-5, it can be seen that too high a hot isostatic pressing temperature, too long a time or too high an oxygen content can result in poor mechanical properties of the obtained composite material, which is due to the decomposition or oxidation of the liquid crystal polymer during the process. By comparing Comparative Example 3 with Comparative Examples 6 and 9, if the inert gas flow is too small or the vacuum degree is not enough, the mechanical properties of the liquid crystal polymer composite material during the heat treatment process do not improve significantly, and cannot meet the required strength requirements, and even can decrease. By comparing Comparative Example 3 with Comparative Examples 7-8, if the heat treatment temperature is too low or the time is not enough, the performance of the composite material is basically not improved. Similarly, in Comparative Examples 10 and 11, if the heat treatment temperature is too high or the time is too long, the performance of the composite material cannot be improved, but rather is damaged. By comparing Comparative Example 3 with Comparative Examples 11 and 12, if the fiber content is too low, the overall strength of the obtained composite material cannot meet the required requirements, and the composite material cannot be formed.

[0089] The continuous fiber reinforced high interlaminar shear liquid crystal polymer composite material of the present application is easy to prepare, has high strength, and can be used for large structural parts.

Claims

1. A method for producing a continuous fiber-reinforced high interlaminar shear liquid crystalline polymer composite, characterized by , the preparation steps of which are as follows: (1) stacking low-melting-point liquid crystal polymer films on and under the continuous fiber bundle to form a stack; (2) stacking high-melting-point liquid crystal polymer films on and under the stack formed in step (1) to form a secondary stack; (3) pre-pressing the secondary stack formed in step (2) into a shape through a hot isostatic pressing process; the hot isostatic pressing process is performed in an inert gas medium for 1-10 minutes, the inert gas being at least one of nitrogen, argon and carbon dioxide, and the oxygen content being below 20 PPM; (4) laminating the fiber bundle after the isostatic pressing process with a liquid crystal polymer film body having a toughening agent dispersed therein and then performing heat treatment to obtain a continuous fiber-reinforced high-interlayer-shear liquid crystal polymer composite material; the laminated body is in a vacuum or inert gas medium during the heat treatment process, and the oxygen content is controlled to be below 20 ppm; in the continuous fiber-reinforced high-interlayer-shear liquid crystal polymer composite material in the present application, the fiber bundle accounts for greater than or equal to 25% and less than 65% of the weight ratio of the composite material; the continuous fiber bundle in the present application is selected from one or both of glass fiber and carbon fiber; the carbon fiber is a high-strength high-modulus fiber with a carbon content of more than 90%, selected from high-strength carbon fiber obtained by carbonization of polyacrylonitrile fiber, viscose-based fiber and pitch-based fiber as precursor fiber, and the diameter is between 5-15 microns.

2. The method for preparing a continuous fiber-reinforced interlayer shear liquid crystal polymer composite material according to claim 1, characterized in that: in step (3), the processing temperature used in the hot isostatic pressing process is in the temperature range from the melting point of the liquid crystal polymer to 20°C higher than the melting point of the liquid crystal polymer; and the pressure used is 5-30 MPa.

3. The method for preparing a continuous fiber-reinforced interlayer shear liquid crystal polymer composite material according to claim 1, characterized in that: in step (4), the heat treatment is performed under inert gas flow or vacuum conditions for 4-12 hours, the inert gas being at least one of nitrogen, argon and carbon dioxide, and the gas flow rate being greater than 10 mL / min; the vacuum condition is a vacuum degree of less than or equal to 100 Pa.

4. The method for preparing a continuous fiber-reinforced interlayer shear liquid crystal polymer composite material according to claim 3, characterized in that: in step (4), the vacuum condition is a vacuum degree of less than 20 Pa.

5. The method for preparing a continuous fiber-reinforced interlayer shear liquid crystal polymer composite material according to claim 3, characterized in that: in step (4), the processing temperature used in the heat treatment process is in the temperature range from 100°C below the melting point of the liquid crystal polymer to 20°C below the melting point of the liquid crystal polymer.

6. The method for preparing a continuous fiber-reinforced interlayer shear liquid crystal polymer composite material according to claim 1, characterized in that: the glass fiber in the present application is selected from E-glass fiber, and the diameter is between 5-20 microns.

7. The method for preparing a continuous fiber-reinforced interlayer shear liquid crystal polymer composite material according to claim 1, characterized in that: the liquid crystal polymer is a liquid crystal polyester or polyester amide formed using an aromatic compound as a raw monomer.

8. The method for preparing a continuous fiber-reinforced interlayer shear liquid crystal polymer composite material according to claim 7, characterized in that: the liquid crystal polymer is a liquid crystal polyester formed by polymerization using an aromatic hydroxyl carboxylic acid and at least one compound selected from the group consisting of aromatic hydroxyl amine, aromatic diamine, aromatic dicarboxylic acid and aromatic diol.

9. A continuous fiber-reinforced high interlaminar shear liquid crystalline polymer composite, characterized by: it is manufactured by the preparation method of any one of claims 1-8, and the interlayer shear strength is ≥80 MPa.

10. A molded product composed of the composition manufactured by the preparation method of any one of claims 1-8.

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