A composite material of a thermotropic liquid crystal polymer and a polyimide, and a preparation method and application thereof

Abstract

The present invention discloses a composite material of a thermotropic liquid crystal polymer and a polyimide, its preparation method and application, belonging to the technical field of polymer materials. The composite material is obtained by melt-extruding the thermotropic liquid crystal polymer and the modified polyimide; the modified polyimide is a porous functional material formed by coupling silica aerogel on the polyimide molecular chain. In the present invention, the polyimide is modified, and a porous functional material is formed by coupling silica aerogel on the polyimide molecular chain. The silica aerogel is coupled on the polyimide molecular chain through chemical bonds, avoiding the occurrence of organic-inorganic phase separation during the high-temperature process, thereby affecting the mechanical properties and uniformity of the material, and thus obtaining a composite material of a thermotropic liquid crystal polymer and a polyimide, which not only has a low dielectric constant and a low dielectric loss, but also has good mechanical properties; it can be used for preparing or as a substrate for communication modules.

Description

Technical Field

[0001] The present invention belongs to the technical field of polymer materials, and particularly relates to a composite material of a thermotropic liquid crystal polymer and polyimide, a preparation method thereof, and an application thereof. Background Art

[0002] High-frequency communications (5G / 6G) represented by 5G have characteristics such as high speed, high connection number, and low latency, and have extremely high thermal, mechanical, and electrical properties for the base materials used to manufacture communication modules. Among them, thermotropic liquid crystal polymer LCP and modified polyimide MPI are hot materials in the 5G application field. In addition to having high strength, high modulus, high insulation, and low water absorption, the most important thing is that they have low dielectric constant and dielectric loss, which can reduce the loss during communication, reduce the thermal effect, and enhance stability. Therefore, LCP and MPI are considered to be the two polymer materials with the most application prospects in the high-frequency communication fields of 5G and even 6G. The existing LCP material has a dielectric constant of 3.5 and a dielectric loss of 0.0015; while the MPI has a dielectric constant of 3.2 and a dielectric loss of 0.0025. The dielectric constants and dielectric losses of both materials are relatively high. Therefore, it is of great research significance to modify LCP materials and modified polyimides in the direction of higher dielectric properties (dielectric loss, dielectric constant).

[0003] Currently, the commonly used modification methods for low-dielectric materials mainly include three categories: modification of the functional group structure of the material body, blending modification with low-dielectric polymers, and filling modification with low-dielectric fillers. Introducing some groups into the molecular chain for modification can change the polarity of the molecule and reduce the molecular dipole moment, which helps to reduce the molecular polarity. The weaker the polarity, the smaller the dielectric constant. However, the improvement of the dielectric properties of the material body by adjusting a small amount of functional groups is limited; the dielectric properties of the blending-modified materials with low-dielectric polymers are usually higher than those of LCP and MPI. For example, PTFE and PVDF have a dielectric constant less than 2.5 and a dielectric loss value less than 0.0005. However, the compatibility of fluorine-containing materials is usually poor, and the mechanical properties will be greatly weakened after blending.

[0004] Chinese Patent No. CN113652061A discloses a low-dielectric constant LCP film and a preparation method thereof. In the preparation, the liquid crystal polymer, inorganic filler, and polyimide are ball-milled and mixed to obtain a mixture; the inorganic filler is one of silica, graphene, and carbon nanotubes, with a dielectric constant lower than 2.6 and a dielectric loss factor lower than 0.005. However, the dielectric constant and loss of the composite material prepared by this method are still not low enough, and other composite materials with better properties need to be developed to improve the properties of communication modules. Summary of the Invention

[0005] The object of the present invention is to solve the above technical problems and provide a composite material of a thermotropic liquid crystal polymer and polyimide, which has a low dielectric constant and a low dielectric loss. Another object of the present invention is to provide the preparation and application of this material.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A composite material of a thermotropic liquid crystal polymer and polyimide, which is obtained by melt extrusion of a thermotropic liquid crystal polymer and a modified polyimide; the modified polyimide is a porous functional material formed by coupling silica aerogel on the polyimide molecular chain.

[0008] In the present invention, polyimide is modified to form a porous functional material by coupling silica aerogel on the polyimide molecular chain. The silica aerogel is coupled on the polyimide molecular chain through chemical bonds to avoid organic-inorganic phase separation during the high-temperature process, thereby affecting the mechanical properties and uniformity of the material. Furthermore, a composite material of a thermotropic liquid crystal polymer and polyimide is obtained, which not only has a low dielectric constant and a low dielectric loss, but also has good mechanical properties.

[0009] Furthermore, the composite material of the thermotropic liquid crystal polymer and polyimide, by weight, comprises 60-90 parts of the thermotropic liquid crystal polymer and 10-40 parts of the modified polyimide.

[0010] Furthermore, the composite material of the thermotropic liquid crystal polymer and polyimide, by weight, comprises 60-80 parts of the thermotropic liquid crystal polymer and 20-30 parts of the modified polyimide.

[0011] Furthermore, the preparation method of the modified polyimide is as follows:

[0012] S1. Dispersing diamine monomers and dianhydride monomers in a polar solvent, polycondensing into polyamic acid, and adding a coupling agent as a capping agent to the solution where the polyamic acid is located to obtain a solution of polyamic acid modified at the terminal with silicon;

[0013] S2. Adding silica aerogel to the solution of polyamic acid modified at the terminal with silicon, so that the silica aerogel is coupled on the polyimide molecular chain through chemical bonding; adding a catalyst and a dehydrating agent, and heating to reflux to obtain the modified polyimide.

[0014] Preferably, the polar solvent is one of N,N-dimethylacetamide, N-methylpyrrolidone, N,N-dimethylformamide, and acetonitrile.

[0015] Furthermore, the catalyst is triethylamine; the dehydrating agent is acetic anhydride.

[0016] Further, in step S1, the diamine monomer is 20-80 parts by weight of phenylenediamine and 20-80 parts by weight of 1,3-bis(4'-aminophenoxy)benzene.

[0017] Further, in the preparation method of the modified polyimide, by weight, the dianhydride monomer is 100-110 parts, the coupling agent is 0.5-2.0 parts, and the silica aerogel is 4-6 parts.

[0018] Furthermore, the silica aerogel is obtained by adding a pore-forming agent to a mixed solution of tetraethyl orthosilicate and an ethanol solution to obtain a silica wet gel, and then through thermal oxidation aging.

[0019] Preferably, the pore-forming agent is PEG200, glycerol, or ethylene glycol.

[0020] Preferably, the molar ratio of tetraethyl orthosilicate to the ethanol solution is 1:2 to 10, and the molar ratio of water to absolute ethanol in the ethanol solution is 1:4 to 1:6.

[0021] Preferably, the mixed solution of tetraethyl orthosilicate and the ethanol solution is a mixture of tetraethyl orthosilicate and the ethanol solution, and is allowed to stand at a pH value of 2-5 and a temperature of 60-100 °C.

[0022] Preferably, the thermal oxidation aging is oxidation at 80-120 °C.

[0023] Further, the molar ratio of the pore-forming agent to tetraethyl orthosilicate is 1:10 to 1:20.

[0024] The present invention provides an application of the composite material of the thermotropic liquid crystal polymer and polyimide in the preparation or as a substrate for a communication module.

[0025] The beneficial effects of the composite material provided by the present invention are:

[0026] The composite material of the thermotropic liquid crystal polymer and polyimide provided by the present invention not only has a low dielectric constant and low dielectric loss, but also has good mechanical properties and uniformity, solving the problem of poor dielectric properties of single polyimide or single thermotropic liquid crystal polymer materials at present; the composite material of the thermotropic liquid crystal polymer and polyimide can be used in the preparation or as a substrate for a communication module. Description of the Drawings

[0027] Figure 1 It is a diagram of various materials involved in Examples 1-8 and Comparative Examples 1-4 of the present invention;

[0028] Figure 1 In it, A represents the modified polyimide resin powder; B represents Vectra A950; C represents the granulation process during melt extrusion; D represents the composite material prepared in Example 1.

[0029] Figure 2 DSC differential scanning calorimeter chart of the material of Example 1.

[0030] Figure 3 DSC differential scanning calorimeter chart of the material of Comparative Example 1.

[0031] Figure 4 DSC differential scanning calorimeter chart of the material of Comparative Example 2.

[0032] Figure 5 DSC differential scanning calorimeter chart of the material of Comparative Example 3. Detailed implementation manners

[0033] In order to enable those skilled in the art to better understand the solution of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work shall fall within the protection scope of the present invention. The reagents and drugs involved in the embodiments of the present invention are commercially available unless otherwise specified, and those skilled in the art can obtain and use them through well-known channels in the art.

[0034] Example 1

[0035] This example provides a composite material of a thermotropic liquid crystal polymer and polyimide, which is obtained by melt extrusion of a thermotropic liquid crystal polymer and a modified polyimide ( Figure 1 C); the modified polyimide is a porous functional material formed by coupling silica aerogel on the polyimide molecular chain.

[0036] As an optional solution, the preparation method of the modified polyimide is as follows:

[0037] S1. Dispersing diamine monomers and dianhydride monomers in a polar solvent, polycondensing into polyimide acid, and adding a coupling agent as a capping agent to the solution where the polyimide acid is located to obtain a solution of polyimide acid modified at the end with silicon;

[0038] S2. Adding silica aerogel to the solution of polyimide acid modified at the end with silicon, so that the silica aerogel is coupled to the polyimide molecular chain in a chemical bonding form; adding a catalyst and a dehydrating agent, and heating to reflux to obtain the modified polyimide. Among them, preferably, the catalyst is triethylamine; the dehydrating agent is acetic anhydride; the diamine monomers are phenylenediamine and 1,3-bis(4'-aminophenoxy)benzene.

[0039] As an alternative, the method for preparing silica aerogel is as follows: adding a pore-forming agent to a mixed solution of tetraethyl orthosilicate and ethanol solution to obtain a silica wet gel, and then performing thermal oxidation aging to obtain silica aerogel.

[0040] Among them, the mixed solution of tetraethyl orthosilicate and ethanol solution is a mixture of tetraethyl orthosilicate and ethanol solution, and is allowed to stand at a pH value of 2-5 and a temperature of 60-100 °C. Preferably, the pore-forming agent is PEG200, glycerol, or ethylene glycol; preferably, the thermal oxidation aging is oxidation at 80-120 °C.

[0041] The specific steps for preparing the composite material of the thermotropic liquid crystal polymer and polyimide in this example are as follows:

[0042] (1) Add tetraethyl orthosilicate (TEOS) to a mixed solution of an appropriate amount of deionized water and absolute ethanol (the mixing ratio of the mixed solution is 1:1), the molar ratio of TEOS to the mixed solution is 1:4, and use a 0.1 mol / L dilute hydrochloric acid solution to adjust the pH of the reaction system to 4. Raise the temperature to 60 °C and continue stirring for 1 h. After standing for 12 h, add an appropriate amount of pore-forming agent PEG200 (the molar ratio of PEG200 to TEOS is 1:5), and use 5% ammonia water to adjust the pH to neutral. Stand at room temperature for 3 h to obtain a silica wet gel. Place it in a vacuum freeze dryer at -10 °C to -20 °C, freeze-dry to obtain a dry aerogel precursor, and then dry it at normal pressure at 80-120 °C to obtain a functional material. Grind and crush the aerogel through an 800-mesh sieve to obtain uniformly sized aerogel particles.

[0043] (2) Polycondense diamine monomers, dianhydride monomers, silica aerogel particles, and silane coupling agent KH550 in a certain proportion to form a modified polyimide resin powder ( Figure 1 A). The specific process is as follows: Based on the number of moles as the number of parts, select 40 parts of p-phenylenediamine and 60 parts of 1,3-bis(4'-aminophenoxy)benzene as diamine monomers, 102 parts of biphenyltetracarboxylic dianhydride as dianhydride monomer, 2 parts of silane coupling agent (3-aminopropyltriethoxysilane, commercial brand KH550), and 5 parts of silica aerogel particles as reactants. First, mix the dry materials of diamine and diacid monomers, add 500 parts of polar solvent, preferably DMAc, lower the temperature to -5 °C and then start stirring, with a stirring speed of 200 r / min. After stirring for 3 h, the viscosity rises to more than 20,000 mPa·s. Add the coupling agent and silica aerogel, and continue stirring for 1 h. Then add 150 parts of acetic anhydride as a dehydrating agent and 50 parts of triethylamine as a catalyst, heat to 160 °C, and yellow powder precipitates after 12 h, which is the modified polyimide (MPI) resin powder. Filter and collect the powder and dry it at 120 °C for 2 h.

[0044] (3) Preparation of LCP / MPI composite material, with the following formulation ratios: LCP is Vectra A950( Figure 1 B) 60 parts of pure resin and 40 parts of MPI resin powder prepared according to the above scheme. Then, the mixture is extruded, melted, and granulated at 350 °C to obtain a homogeneous composite material of thermotropic liquid crystal polymer and polyimide( Figure 1 D).

[0045] Example 2

[0046] This example provides another preparation method for the composite material of this thermotropic liquid crystal polymer and polyimide. The specific steps are as follows:

[0047] (1) The same as step (1) of Example 1 above;

[0048] (2) The diamine monomer, dianhydride monomer, silica aerogel particles, and silane coupling agent KH550 are polycondensed into modified polyimide resin powder according to a certain ratio. The specific process is as follows: Select 20 parts of p-phenylenediamine and 80 parts of 1,3-bis(4'-aminophenoxy)benzene as diamine monomers, 102 parts of biphenyltetracarboxylic dianhydride as dianhydride monomer, 2 parts of silane coupling agent, and 5 parts of silica aerogel particles as reactants. First, mix the dry materials of diamine and diacid monomers, add 500 parts of polar solvent, preferably DMAc, cool to -5 °C and then start stirring at a stirring speed of 200 r / min. After stirring for 3 h, the viscosity rises to more than 20,000 mPa·s. Add the coupling agent and silica aerogel, and continue stirring for 1 h. Then add 150 parts of acetic anhydride and 50 parts of triethylamine as a catalyst, heat to 160 °C for 12 h, and yellow powder is precipitated, which is the modified polyimide (MPI) resin powder. Filter and collect the powder and dry it at 120 °C for 2 h.

[0049] (3) The same as step (3) of Example 1 above to obtain a homogeneous composite material of thermotropic liquid crystal polymer and polyimide.

[0050] Example 3

[0051] This example provides another preparation method for the composite material of this thermotropic liquid crystal polymer and polyimide. The specific steps are as follows:

[0052] (1) The same as step (1) of Example 1 above;

[0053] (2) Polycondense diamine monomers, dianhydride monomers, silica aerogel particles, and silane coupling agent KH550 in a certain proportion to form modified polyimide resin powder. The specific process is as follows: Select 60 parts of p-phenylenediamine and 40 parts of 1,3-bis(4'-aminophenoxy)benzene as diamine monomers, 102 parts of biphenyltetracarboxylic dianhydride as dianhydride monomer, 2 parts of silane coupling agent, and 5 parts of silica aerogel particles as reactants. First, mix the dry materials of diamine and diacid monomers, add 500 parts of polar solvent, preferably DMAc, start stirring after cooling to -5°C, and the stirring speed is 200 r / min. After stirring for 3 h, the viscosity rises above 20,000 mPa·s, add the coupling agent and silica aerogel, and continue stirring for 1 h. Then add 150 parts of acetic anhydride and 50 parts of triethylamine as a catalyst, heat to 160°C for 12 h, precipitate yellow powder, which is modified polyimide (MPI) resin powder, filter and collect the powder, and dry it at 120°C for 2 h.

[0054] (3) The same as step (3) of Example 1 above to obtain a homogeneous composite material of thermotropic liquid crystal polymer and polyimide.

[0055] Example 4

[0056] This example provides another preparation method of the composite material of this thermotropic liquid crystal polymer and polyimide. The specific steps are as follows:

[0057] (1) The same as step (1) of Example 1 above;

[0058] (2) Polycondense diamine monomers, dianhydride monomers, silica aerogel particles, and silane coupling agent KH550 in a certain proportion to form modified polyimide resin powder. The specific process is as follows: Select 80 parts of p-phenylenediamine and 20 parts of 1,3-bis(4'-aminophenoxy)benzene as diamine monomers, 102 parts of biphenyltetracarboxylic dianhydride as dianhydride monomer, 2 parts of silane coupling agent, and 5 parts of silica aerogel particles as reactants. First, mix the dry materials of diamine and diacid monomers, add 500 parts of polar solvent, preferably DMAc, start stirring after cooling to -5°C, and the stirring speed is 200 r / min. After stirring for 3 h, the viscosity rises above 20,000 mPa·s, add the coupling agent and silica aerogel, and continue stirring for 1 h. Then add 150 parts of acetic anhydride and 50 parts of triethylamine as a catalyst, heat to 160°C for 12 h, precipitate yellow powder, which is modified polyimide (MPI) resin powder, filter and collect the powder, and dry it at 120°C for 2 h.

[0059] (3) The same as step (3) of Example 1 above to obtain a homogeneous composite material of thermotropic liquid crystal polymer and polyimide.

[0060] Example 5

[0061] This embodiment provides another preparation method of the composite material of the present thermotropic liquid crystal polymer and polyimide, and the specific steps are as follows:

[0062] (1) The same as step (1) of Embodiment 1 above;

[0063] (2) The same as step (2) of Embodiment 1 above;

[0064] (3) Preparation of LCP / MPI composite material, and the formulation ratio is as follows: 70 parts of Vectra A950 pure resin for LCP, 30 parts of MPI resin powder prepared according to the above scheme, and then the mixture is extruded, melted and modified into pellets to obtain a uniform composite material of thermotropic liquid crystal polymer and polyimide.

[0065] Example 6

[0066] This embodiment provides another preparation method of the composite material of the present thermotropic liquid crystal polymer and polyimide, and the specific steps are as follows:

[0067] (1) The same as step (1) of Embodiment 1 above;

[0068] (2) The same as step (2) of Embodiment 1 above;

[0069] (3) Preparation of LCP / MPI composite material, and the formulation ratio is as follows: 80 parts of Vectra A950 pure resin for LCP, 20 parts of MPI resin powder prepared according to the above scheme, and then the mixture is extruded, melted and modified into pellets to obtain a uniform composite material of thermotropic liquid crystal polymer and polyimide.

[0070] Example 7

[0071] This embodiment provides another preparation method of the composite material of the present thermotropic liquid crystal polymer and polyimide, and the specific steps are as follows:

[0072] (1) The same as step (1) of Embodiment 1 above;

[0073] (2) The same as step (2) of Embodiment 1 above;

[0074] (3) Preparation of LCP / MPI composite material, and the formulation ratio is as follows: 90 parts of Vectra A950 pure resin for LCP, 10 parts of MPI resin powder prepared according to the above scheme, and then the mixture is extruded, melted and modified into pellets to obtain a uniform composite material of thermotropic liquid crystal polymer and polyimide.

[0075] Example 8

[0076] This embodiment provides another preparation method of the composite material of the present thermotropic liquid crystal polymer and polyimide, and the specific steps are as follows:

[0077] (1) is the same as step (1) of the above-mentioned Example 1;

[0078] (2) Polycondense diamine monomers, dianhydride monomers, silica aerogel particles, and silane coupling agent KH550 in a certain proportion to form modified polyimide resin powder. The specific process is as follows: Select 60 parts (648.8 g) of p-phenylenediamine and 40 parts (1169.3 g) of 1,3-bis(4'-aminophenoxy)benzene as diamine monomers, 102 parts (3000.9 g) of biphenyltetracarboxylic dianhydride as dianhydride monomer, 1 part of silane coupling agent, and 2.5 parts of silica aerogel particles as reactants. First, mix the dry materials of diamine and diacid monomers, add 500 parts of polar solvent, preferably DMAc, cool to -5°C and then start stirring at a stirring speed of 200 r / min. After stirring for 3 h, the viscosity rises above 20,000 mPa·s, add coupling agent KH550 and silica aerogel, and continue stirring for 1 h. Then add 150 parts of acetic anhydride and 50 parts of triethylamine as catalysts, heat to 160°C for 12 h, precipitate yellow powder, which is modified polyimide (MPI) resin powder, filter and collect the powder and dry it at 120°C for 2 h.

[0079] (3) Preparation of LCP / MPI composite material, the formula ratio is as follows: LCP is 60 parts of Vectra A950 pure resin, and MPI resin powder is 40 parts prepared according to the above scheme. Then extrude and melt-modify the mixture to granulate, and obtain a homogeneous composite material of thermotropic liquid crystal polymer and polyimide.

[0080] Comparative Example 1

[0081] LCP pure resin single material, the specific composition is Vectra A950 pure resin.

[0082] Comparative Example 2

[0083] It is the modified polyimide MPI prepared in step (2) of Example 1.

[0084] Comparative Example 3

[0085] Without using the silane capping agent KH550, the MPI of silica aerogel was mechanically mixed. The specific steps are as follows. In the first step, diamine monomers, dianhydride monomers, and silica aerogel particles were polycondensed into modified polyimide resin powder in a certain proportion. The specific process is as follows: 20 parts of p-phenylenediamine and 80 parts of 1,3-bis(4'-aminophenoxy)benzene were selected as diamine monomers, 102 parts of biphenyltetracarboxylic dianhydride was used as the dianhydride monomer, and 5 parts of silica aerogel particles were used as reactants. First, the dry materials of diamine and diacid monomers were mixed, 500 parts of a polar solvent, preferably DMAc, was added, and the temperature was lowered to -5°C, then stirring was started at a stirring speed of 200 r / min. After stirring for 3 hours, the viscosity increased to more than 20,000 mPa·s, silica aerogel was added, and stirring was continued for 1 h. Then 150 parts of acetic anhydride and 50 parts of triethylamine were added as catalysts, and the temperature was raised to 160°C for 12 h to precipitate yellow powder, which was the modified polyimide (MPI) resin powder. The powder was filtered and collected and dried at 120°C for 2 h.

[0086] Comparative Example 4

[0087] It was obtained by melt extrusion of the MPI powder of Comparative Example 3 with KH550 and LCP. The specific operation is as follows for the preparation of LCP / MPI composite materials. The formulation ratio is as follows: 60 parts of Vectra A950 pure resin of LCP, 2 parts of KH550, and 40 parts of MPI resin powder prepared by the above scheme. Then the mixture was melt extruded and modified into pellets at 350°C to obtain a uniform composite material.

[0088] Test Example 1

[0089] 1. Test method

[0090] The materials in Examples 1-8 and Comparative Examples 1-4 were melt extruded, and their processing temperatures were recorded. And the prepared materials were tested for dielectric constant, dielectric loss factor, and tensile strength. The specific method is as follows: The extruded composite material particles were put into a hot pressing mold and pressed into a square thin sheet with a side length of 3 cm and a thickness of 0.5 μm. The dielectric constant and dielectric loss factor of the material were tested according to GB / T31838. And the DSC differential scanning calorimeter diagram of each material was determined.

[0091] 2. Test results

[0092] The test results are shown in Table 1. As can be seen from Table 1, the dielectric constant Dk of Examples 1-6 is less than or equal to 3.0, which is much lower than the dielectric constant of 3.5 of conventional polyimide materials and can even be comparable to imported modified polyimide materials (PixeoTM IB of Nippon Kayaku Co., Ltd. in Japan). At the same time, compared with Comparative Example 1 of Veatra A950 LCP pure resin, the dielectric constant of the composite material decreases significantly. In Examples 7 and 8, due to the decrease in the MPI content or the decrease in the filling amount of the functional material, the decrease in the dielectric constant is not obvious.

[0093] The dielectric loss Dk of Examples 1-4 is less than 0.0019, and the lowest reaches 0.0015, which is lower than that of pure LCP resin (Comparative Example 1) and polyimide films on the market (PixeoTM IB of Nippon Kayaku Co., Ltd. in Japan). The dielectric loss of Examples 5-8 is close to that of LCP materials, indicating that the composite material of the thermotropic liquid crystal polymer and polyimide of the present invention has obvious advantages in dielectric properties.

[0094] Compared with directly melt-extruding silica particles, LCP, and polyimide powder, the present invention can uniformly disperse inorganic-organic materials, avoid local accumulation and phase separation, and ensure that the mechanical properties of the composite material are not affected.

[0095] From Figures 2 to 5 the DSC diagrams, the measurable glass transition temperatures are 318 °C, 302 °C, 261 °C, and 296 °C respectively. It shows that Comparative Example 3 is MPI without a coupling agent, and its dielectric properties are significantly poor. Due to the difficulty of two-phase dispersion, surface and internal defects are caused, not only the dielectric properties are poor, but also the tensile strength drops sharply. Comparative Example 4 is adding a coupling agent during the processing. Similarly, due to the poor compatibility of the organic-inorganic phases, both the dielectric properties and the tensile strength decrease. For the in-situ modified composite material, due to the incorporation of inorganic phase silica aerogel, the heat resistance is improved. Mainly, the silica aerogel increases the glass transition temperature of MPI. As can be seen from Comparative Example 3, the temperature of pure PI resin is nearly 40 degrees lower than that of silica aerogel resin-modified MPI, and the heat resistance is insufficient. As can be seen from Example 1 and Comparative Example 4, the PI capped with coupling agent KH550 forms a chemical bond with silica aerogel in-situ, and has high thermal stability, and the glass transition temperature is increased by 20 °C compared with simple mechanical compounding.

[0096] Table 1 Electrical properties, mechanical properties, and processing temperatures of the materials of Examples 1-8 and Comparative Examples 1-4

[0097]

[0098] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the solutions. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that they can modify or equivalently replace the technical solutions of the present invention on the basis of understanding the solutions, without departing from the purpose and scope of the technical solutions of the present invention, and all of them should be covered by the scope of the claims of the present invention.

Claims

1. A composite material of a thermotropic liquid crystal polymer and a polyimide, characterized in that: The composite material comprises 60-90 parts of a thermotropic liquid crystal polymer and 10-40 parts of a modified polyimide, wherein the composite material is obtained by melt extrusion of the thermotropic liquid crystal polymer and the modified polyimide; the modified polyimide is a porous functional material formed by coupling a silicon dioxide aerogel to a polyimide molecular chain; The preparation method of the modified polyimide is as follows: S1. dispersing a diamine monomer and a dianhydride monomer in a polar solvent, polycondensing to form a polyimide acid, adding a coupling agent as a capping agent to the polyimide acid solution to obtain a terminal silicon-modified polyimide acid solution, wherein the coupling agent is a silane coupling agent; The diamine monomer is 20-80 parts by weight of phenylenediamine and 20-80 parts by weight of 1,3-bis(4'-aminophenoxy)benzene; the dianhydride monomer is 100-110 parts by weight, the coupling agent is 0.5-2.0 parts, and the silica aerogel is 4-6 parts; S2. Adding silica aerogel to the terminal silicon-modified polyimide acid solution to couple the silica aerogel to the polyimide molecular chain through chemical bonding; adding a catalyst and a dehydrating agent, heating and refluxing to obtain a modified polyimide.

2. The composite material of thermotropic liquid crystal polymer and polyimide according to claim 1, characterized in that: The invention comprises 60-80 parts of thermotropic liquid crystal polymer and 20-30 parts of modified polyimide by weight.

3. The composite material of thermotropic liquid crystal polymer and polyimide according to claim 1, characterized in that: The catalyst is triethylamine; the dehydrating agent is acetic anhydride.

4. The composite material of thermotropic liquid crystal polymer and polyimide according to claim 1, characterized in that: The silicon dioxide aerogel is prepared by adding a porogen into a mixture of tetraethyl orthosilicate and an ethanol solution to obtain a silicon dioxide wet gel, which is then subjected to thermal oxygen aging to obtain the silicon dioxide aerogel.

5. The composite material of thermotropic liquid crystal polymer and polyimide according to claim 4, characterized in that: The molar ratio of the porogen to tetraethyl orthosilicate is 1:10-1:

20.

6. The method according to any one of claims 1 to 5 of Application of a composite material of thermotropic liquid crystal polymer and polyimide in the preparation or as a communication module substrate.

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