High-temperature-resistant and high-thermal-conductivity LCP material and preparation method

Abstract

The application relates to the technical field of liquid crystal polymers, and discloses a high-temperature-resistant and high-thermal-conductivity LCP material and a preparation method. Modified graphene and hydroxyl boron nitride nanosheets are ultrasonically dispersed and stirred to obtain graphene-coated boron nitride, which is then blended with liquid crystal polyarylate to obtain the high-temperature-resistant and high-thermal-conductivity LCP material. The surface of the modified graphene contains a large number of benzoate structures which are the same as those of the liquid crystal polyarylate, the compatibility between the graphene and the liquid crystal polyarylate is significantly improved, the graphene and the coated boron nitride nanosheets can be uniformly dispersed in the LCP material, a continuous thermal conduction path is formed, the thermal conductivity coefficient and the thermal conduction performance of the material are improved, and the high-temperature resistance of the LCP material is improved.

Description

Technical Field

[0001] This invention relates to the field of liquid crystal polymer technology, specifically to a high-temperature resistant and high-thermal-conductivity LCP material and its preparation method. Background Technology

[0002] Liquid crystal polyarylate (LCP) possesses excellent mechanical strength, electrical insulation, and heat resistance, making it widely used in automotive parts, electronics, aerospace, and other fields. However, the poor thermal conductivity of ordinary LCP materials hinders their practical application in aircraft thermal protection structures and battery heat dissipation modules. Adding nano-fillers to LCP materials can improve their thermal and electrical conductivity, as well as their high-temperature resistance.

[0003] Graphene possesses high mechanical strength, high thermal conductivity, and strong high-temperature resistance, which can improve the mechanical and thermal properties of liquid crystal polyarylate materials. Nano-boron nitride has a very high thermal conductivity and is simple to prepare, inexpensive, and readily available, making it important for applications in fibers and plastics. However, improving the dispersibility of graphene and boron nitride in liquid crystal polyarylates remains a research challenge. Summary of the Invention

[0004] This invention solves the problem of low thermal conductivity of LCP materials and improves their high-temperature resistance and other properties.

[0005] The technical solution of this invention is: a method for preparing a high-temperature resistant and high-thermal-conductivity LCP material, comprising the following steps: Step S1: Add tetrahydrofuran and graphene oxide to a flask, disperse by ultrasonication, then add biphenyl tetra(formate benzoic acid), 4-dimethylaminopyridine, and N,N-dicyclohexylcarbodiimide. Stir the reaction, filter, wash successively with water, tetrahydrofuran, and ethanol, and dry to obtain modified graphene. The reaction formula is:

[0006] Step S2: Add water, modified graphene, and boron nitride nanosheets to a flask, disperse by ultrasonication, stir, filter, and dry to obtain graphene-coated boron nitride; then mix with liquid crystal polyarylate, add to a double cone mixer, and co-extrude to obtain a high-temperature resistant and high thermal conductivity LCP material.

[0007] Preferably, in step S1, the reaction temperature is 20-35℃ and the reaction time is 60-72h.

[0008] Preferably, in step S1, the mass ratio of graphene oxide, biphenyl tetra(formate benzoic acid), 4-dimethylaminopyridine, and N,N-dicyclohexylcarbodiimide is 100:(30-120):(18-58):(8-35).

[0009] Preferably, in step S2, the ultrasonic dispersion time is 20-40 min, the stirring time is 3-5 h, and the stirring temperature is 15-40℃.

[0010] Preferably, in step S2, the mass ratio of modified graphene, boron hydroxynitride nanosheets, and liquid crystal polyarylate is (0.2-0.7):(0.1-0.5):100.

[0011] Preferably, in step S2, the blending temperature is 290-305℃.

[0012] Preferably, in step S2, the heat treatment temperature is 270-285℃ and the time is 6-10h.

[0013] Preferably, the preparation method of biphenyl tetra(formate benzoic acid) includes the following steps: adding water, sodium carbonate, and p-hydroxybenzoic acid to a flask, stirring, and then adding a chloroform solution containing 3,3',5,5'-biphenyltetracarboxylic acid chloride dropwise in an ice bath, wherein the molar ratio of sodium carbonate, p-hydroxybenzoic acid, and 3,3',5,5'-biphenyltetracarboxylic acid chloride is (4-4.8):(4-4.4):1; rapidly stirring the reaction at 15-25℃ for 24-36 h, controlling the stirring speed at 800-1500 r / min to avoid separation of water and chloroform; adding hydrochloric acid solution dropwise to adjust the pH to 3-4, precipitating the precipitate, filtering, washing with water, and drying to obtain biphenyl tetra(formate benzoic acid). The reaction formula is:

[0014] The beneficial technical effects of this invention are as follows: By using the carboxyl groups of biphenyl tetra (benzoic acid ester) containing multiple carboxyl groups and benzoic acid ester structures to carry out an esterification reaction with the hydroxyl groups on the surface of graphene oxide, a modified graphene containing a large number of carboxyl groups and benzoic acid ester structures is obtained. After coating the boron nitride nanosheets with hydroxyl groups, they are then blended with liquid crystal polyarylate to obtain a high-temperature resistant and high thermal conductivity LCP material.

[0015] The modified graphene of this invention contains a large number of carboxyl groups on its surface, which form strong hydrogen bonds and other interactions with the hydroxyl groups on the surface of boron nitride nanosheets. This enhances the interfacial force between graphene and boron nitride, resulting in a tighter bond and effectively coating the boron nitride. This reduces the interfacial thermal resistance and improves the thermal conductivity of the LCP material. In actual production, adding an excess of graphene to coat boron nitride in the LCP material can achieve a thermal conductivity of 10⁻¹⁵ W·m. -1 ·K -1 However, it affects the high-temperature resistance of the material.

[0016] In this invention, the modified graphene surface contains a large number of benzoate structures identical to those in liquid crystal polyarylates, significantly improving the compatibility between graphene and liquid crystal polyarylates. This allows graphene and coated boron nitride nanosheets to be uniformly dispersed in the LCP material, forming continuous thermally conductive pathways and further improving the material's thermal conductivity and thermal performance. Simultaneously, the uniformly dispersed graphene and coated boron nitride nanosheets can improve the thermal decomposition mass loss temperature and high-temperature resistance of the LCP material. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0018] 100 mL of 5 mol / L sodium hydroxide solution was added to the reaction vessel, followed by 0.8 g of boron nitride nanosheets. The mixture was heated to 130 °C and stirred for 24 h. After filtration, washing with water, and drying, hydroxy boron nitride nanosheets were obtained.

[0019] By Journal J. Org. Chem. 2006, 71 3,3',5,5'-Biphenyltetracarboxylic acid chloride was prepared according to the method described in references 7854-7857, "Recognition Properties of an Acyclic Biphenyl-Based Receptor toward Carbohydrates". 20 mL of tetrahydrofuran, 0.53 mL of thionyl chloride, and 0.3 g of 3,3',5,5'-biphenyltetracarboxylic acid were added to a flask. The mixture was heated to 70 °C and refluxed under condensation for 3 h. The tetrahydrofuran and unreacted thionyl chloride were removed by vacuum distillation to obtain 3,3',5,5'-biphenyltetracarboxylic acid chloride.

[0020] The following liquid crystal polyarylate, model E4008 MR-B, was purchased from Dongguan Zhongxuante Plastics & Chemical Co., Ltd. The graphene oxide has a thickness of 0.6-1.2 nm and a diameter of 0.8-2 μm; the boron nitride nanosheets have a size of 200 nm. Example 1

[0021] (1) Add 20 mL of water, 12 mmol of sodium carbonate and 12 mmol of p-hydroxybenzoic acid to a flask, stir, and then add 8 mL of chloroform solution containing 3 mmol of 3,3',5,5'-biphenyltetracarboxylic acid chloride in an ice bath. Stir rapidly at 25 °C for 24 h, controlling the stirring speed at 1500 r / min. After the reaction, add 25% hydrochloric acid solution to the solution to adjust the pH to 4, precipitate out the precipitate, filter, wash with water and dry to obtain biphenyltetracarboxylic acid (carboxylic acid ester).

[0022] (2) Add 120 mL of tetrahydrofuran and 1 g of graphene oxide to a flask, disperse by ultrasonication for 20 min, add 0.3 g of biphenyl tetra(carbamate benzoic acid), 0.18 g of 4-dimethylaminopyridine and 0.08 g of N,N-dicyclohexylcarbodiimide, stir and react at 25 °C for 60 h, filter, wash with water, tetrahydrofuran and ethanol in sequence, dry to obtain modified graphene.

[0023] (3) Add 0.4L water, 2g modified graphene and 1g boron nitride nanosheets to the flask, ultrasonically disperse for 20min, stir at 20℃ for 3h, filter, dry to obtain graphene-coated boron nitride; then mix with 1kg liquid crystal polyarylate, add to a double cone mixer, and co-extrude at 290℃ to obtain high temperature resistant and high thermal conductivity LCP material. Example 2

[0024] (1) Add 25 mL of water, 14.4 mmol of sodium carbonate and 13.2 mmol of p-hydroxybenzoic acid to a flask, stir, and then add 10 mL of chloroform solution containing 3 mmol of 3,3',5,5'-biphenyltetracarboxylic acid chloride in an ice bath. Stir rapidly at 15 °C for 36 h, controlling the stirring speed at 800 r / min. After the reaction, add 25% hydrochloric acid solution to the solution to adjust the pH to 3, precipitate out, filter, wash with water, and dry to obtain biphenyltetracarboxylic acid (carboxylic acid ester).

[0025] (2) Add 150 mL of tetrahydrofuran and 1 g of graphene oxide to the flask, disperse by ultrasonication for 30 min, add 1.2 g of biphenyl tetra(carbamate benzoic acid), 0.58 g of 4-dimethylaminopyridine and 0.35 g of N,N-dicyclohexylcarbodiimide, stir and react at 20 °C for 72 h, filter, wash with water, tetrahydrofuran and ethanol in sequence, dry to obtain modified graphene.

[0026] (3) Add 0.7L water, 3.5g modified graphene and 2g boron nitride nanosheets to the flask, ultrasonically disperse for 30min, stir at 40℃ for 3h, filter, dry to obtain graphene-coated boron nitride; then mix with 1kg liquid crystal polyarylate, add to a double cone mixer, and co-extrude at 305℃ to obtain high temperature resistant and high thermal conductivity LCP material. Example 3

[0027] (1) Add 150 mL of tetrahydrofuran and 1 g of graphene oxide to a flask, disperse by ultrasonication for 30 min, add 0.6 g of biphenyl tetra(formate benzoic acid) (prepared by the same method as in Example 1), 0.32 g of 4-dimethylaminopyridine and 0.16 g of N,N-dicyclohexylcarbodiimide, stir and react at 35 °C for 60 h, filter, wash with water, tetrahydrofuran and ethanol in sequence, dry, and obtain modified graphene.

[0028] (2) Add 1L of water, 5.5g of modified graphene and 3.5g of boron nitride nanosheets to a flask, ultrasonically disperse for 40min, stir at 15℃ for 5h, filter, and dry to obtain graphene-coated boron nitride; then mix with 1kg of liquid crystal polyarylate, add to a double cone mixer, and co-extrude at 305℃ to obtain high temperature resistant and high thermal conductivity LCP material. Example 4

[0029] (1) Add 150 mL of tetrahydrofuran and 1 g of graphene oxide to a flask, disperse by ultrasonication for 30 min, add 0.9 g of biphenyl tetra(formate benzoic acid) (prepared by the same method as in Example 1), 0.45 g of 4-dimethylaminopyridine and 0.26 g of N,N-dicyclohexylcarbodiimide, stir and react at 25 °C for 72 h, filter, wash with water, tetrahydrofuran and ethanol in sequence, dry to obtain modified graphene.

[0030] (2) Add 1L of water, 7g of modified graphene and 5g of boron nitride nanosheets to a flask, ultrasonically disperse for 40min, stir at 25℃ for 5h, filter, and dry to obtain graphene-coated boron nitride; then mix with 1kg of liquid crystal polyarylate, add to a double cone mixer, and co-extrude at 290℃ to obtain high temperature resistant and high thermal conductivity LCP material.

[0031] Comparative Example 1 (1) Add 0.4L water, 2g graphene oxide and 1g boron nitride nanosheets to a flask, ultrasonically disperse for 20min, stir at 20℃ for 3h, filter, dry to obtain graphene-boron nitride blend; then mix with 1kg liquid crystal polyarylate, add to a double cone mixer, co-extrude at 290℃ to obtain LCP material.

[0032] Comparative Example 2 (1) Add 20 mL of water, 12 mmol of sodium carbonate, and 12 mmol of p-hydroxybenzoic acid to a flask. After stirring, add 8 mL of a chloroform solution containing 6 mmol of terephthaloyl chloride dropwise in an ice bath. Stir rapidly at 25 °C for 24 h, controlling the stirring speed at 1500 r / min. After the reaction, add a 25% hydrochloric acid solution dropwise to the solution to adjust the pH to 4. The precipitate precipitates, is filtered, washed with water, and dried to obtain terephthaloyl benzoic acid, with the structural formula: .

[0033] (2) Add 120 mL of tetrahydrofuran and 1 g of graphene oxide to the flask, disperse by ultrasonication for 20 min, add 0.3 g of terephthalic acid (carbamate benzoic acid), 0.18 g of 4-dimethylaminopyridine and 0.08 g of N,N-dicyclohexylcarbodiimide, stir and react at 25 °C for 60 h, filter, wash with water, tetrahydrofuran and ethanol in sequence, dry to obtain modified graphene.

[0034] (3) Add 0.4L of water, 2g of modified graphene and 1g of boron nitride nanosheets to the flask, ultrasonically disperse for 20min, stir at 20℃ for 3h, filter, dry to obtain graphene-boron nitride blend; then mix with 1kg of liquid crystal polyarylate, add to a double cone mixer, co-extrude at 290℃ to obtain LCP material.

[0035] Comparative Example 3 (1) Add 120 mL of tetrahydrofuran and 1 g of graphene oxide to a flask, sonicate for 20 min, add 0.3 g of 3,3',5,5'-biphenyltetracarboxylic acid, 0.18 g of 4-dimethylaminopyridine and 0.08 g of N,N-dicyclohexylcarbodiimide, stir and react at 25 °C for 60 h, filter, wash with water, tetrahydrofuran and ethanol in sequence, dry, and obtain modified graphene.

[0036] (2) Add 0.4L water, 2g modified graphene and 1g boron nitride nanosheets to a flask, ultrasonically disperse for 20min, stir at 20℃ for 3h, filter, dry to obtain graphene-coated boron nitride; then mix with 1kg liquid crystal polyarylate, add to a double cone mixer, and co-extrude at 290℃ to obtain LCP material.

[0037] Weigh 5 mg of LCP material and place it in a thermogravimetric analyzer. Perform thermal performance testing in a nitrogen atmosphere with a heating rate of 10 °C / min and a temperature range of 25-800 °C.

[0038] The thermal conductivity was tested using a thermal conductivity tester according to the method specified in GB / T 42919.1-2023 standard.

[0039]

[0040] The LCP materials in Examples 1 to 4 exhibit high mass loss temperature, good high-temperature resistance, and high thermal conductivity, demonstrating excellent thermal performance. This is primarily due to the large number of carboxyl groups on the modified graphene surface, which form strong hydrogen bonds and other interactions with the hydroxyl groups on the boron nitride nanosheets. This enhances the interfacial forces between graphene and boron nitride, resulting in a tighter bond and reduced interfacial thermal resistance, thus improving the thermal conductivity of the LCP material. Furthermore, the modified graphene contains a large number of benzoate structures similar to those in liquid crystal polyarylate, significantly improving the compatibility between graphene and liquid crystal polyarylate. This allows graphene and the coated boron nitride nanosheets to be uniformly dispersed in the LCP material, forming continuous thermal pathways and further enhancing the material's thermal conductivity and performance. Simultaneously, the uniformly dispersed graphene and coated boron nitride nanosheets improve the thermal decomposition mass loss temperature and high-temperature resistance of the LCP material.

[0041] The graphene oxide in Comparative Example 1 has a low carboxyl content on its surface, resulting in a low interaction with the boron nitride nanosheets and making it difficult to effectively coat the boron nitride. The interfacial thermal resistance between the two is relatively high, which is not conducive to improving the thermal conductivity of the LCP material. Furthermore, the graphene oxide and boron nitride nanosheets have low compatibility with liquid crystal polyarylate and poor dispersion in the LCP material, resulting in a significantly lower thermal conductivity and thermal decomposition mass loss temperature than in Example 1.

[0042] Comparative Example 2 utilizes terephthalic acid (benzoic acid ester) with a lower content of carboxyl and benzoate groups. After modifying the graphene oxide surface, it does not introduce a large number of carboxyl and benzoate groups into the graphene surface. As a result, the interfacial force between the graphene oxide and boron nitride is lower, the coating effect is poor, and the compatibility with liquid crystal polyarylate is lower than that of Example 1. The dispersion in LCP materials is also poor, resulting in a lower thermal conductivity and thermal decomposition mass loss temperature than that of Example 1.

[0043] Comparative Example 3 utilizes 3,3',5,5'-biphenyltetracarboxylic acid, which does not contain benzoate groups. After modifying the surface of graphene oxide, a large number of benzoate groups were not introduced into the graphene surface, resulting in low compatibility with liquid crystal polyarylate. This leads to poor dispersion of graphene and its coated boron nitride nanosheets in LCP materials, resulting in lower thermal conductivity and thermal decomposition mass loss temperature than in Example 1.

[0044] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions within the technical scope disclosed in the present invention should be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for preparing a high-temperature resistant and high-thermal-conductivity LCP material, characterized in that, The preparation method includes the following steps: Step S1: Add tetrahydrofuran and graphene oxide to the flask, disperse by ultrasonication, add biphenyl tetra(formate benzoic acid), 4-dimethylaminopyridine, and N,N-dicyclohexylcarbodiimide, stir the reaction, filter, wash, and dry to obtain modified graphene. Step S2: Add water, modified graphene, and boron nitride nanosheets to a flask, disperse by ultrasonication, stir, filter, and dry to obtain graphene-coated boron nitride; then mix with liquid crystal polyarylate, add to a double cone mixer, and co-extrude to obtain a high-temperature resistant and high thermal conductivity LCP material.

2. The method for preparing the high-temperature resistant and high-thermal-conductivity LCP material according to claim 1, characterized in that, In step S1, the reaction temperature is 20-35℃ and the reaction time is 60-72h.

3. The method for preparing the high-temperature resistant and high thermal conductivity LCP material according to claim 1, characterized in that, In step S1, the mass ratio of graphene oxide, biphenyl tetra(formate benzoic acid), 4-dimethylaminopyridine, and N,N-dicyclohexylcarbodiimide is 100:(30-120):(18-58):(8-35).

4. The method for preparing the high-temperature resistant and high thermal conductivity LCP material according to claim 3, characterized in that, The preparation method of the biphenyl tetra (formate benzoic acid) includes the following steps: adding water, sodium carbonate, and p-hydroxybenzoic acid to a flask, stirring, and then adding a chloroform solution containing 3,3',5,5'-biphenyl tetracarboxylic acid chloride dropwise in an ice bath. The mixture is then stirred at 15-25°C for 24-36 h, with the stirring speed controlled at 800-1500 r / min. Hydrochloric acid solution is added dropwise to the solution to adjust the pH to 3-4, precipitating the precipitate. The precipitate is then filtered, washed, and dried to obtain biphenyl tetra (formate benzoic acid).

5. The method for preparing the high-temperature resistant and high-thermal-conductivity LCP material according to claim 4, characterized in that, The molar ratio of sodium carbonate, p-hydroxybenzoic acid, and 3,3',5,5'-biphenyltetracarboxylic acid chloride is (4-4.8):(4-4.4):

1.

6. The method for preparing the high-temperature resistant and high-thermal-conductivity LCP material according to claim 1, characterized in that, In step S2, the ultrasonic dispersion time is 20-40 min, the stirring time is 3-5 h, and the stirring temperature is 15-40℃.

7. The method for preparing the high-temperature resistant and high-thermal-conductivity LCP material according to claim 1, characterized in that, In step S2, the mass ratio of modified graphene, boron hydroxynitride nanosheets, and liquid crystal polyarylate is (0.2-0.7):(0.1-0.5):

100.

8. The method for preparing the high-temperature resistant and high-thermal-conductivity LCP material according to claim 1, characterized in that, In step S2, the blending temperature is 290-305℃.

9. A high-temperature resistant and high-thermal-conductivity LCP material obtained by the preparation method according to any one of claims 1-8.

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