High-temperature-resistant, electricity-conducting and heat-conducting graphene-LCP material and preparation method thereof

Abstract

The invention relates to the technical field of liquid crystal polymers, and discloses a high-temperature-resistant, electricity-conducting and heat-conducting graphene-LCP material and a preparation method thereof.The preparation method comprises the steps that a diacid monomer, p-hydroxybenzoic acid and 4, 4 '-bis (4-hydroxyphthalimide)-benzamido benzene are subjected to a carboxyl reaction, liquid crystal polyarylester is obtained and mixed with graphene oxide, and the high-temperature-resistant, electricity-conducting and heat-conducting graphene-LCP material is obtained. The liquid crystal polyarylester molecular chain contains an imide ring, so that the thermal decomposition mass loss temperature of the liquid crystal polyarylester LCP material can be improved. The liquid crystal polyarylester contains amido bonds and forms strong interaction with hydroxyl and carboxyl on the surface of the graphene oxide, the interfacial compatibility between the graphene oxide and the liquid crystal polyarylester can be improved, the graphene oxide does not need surface modification and has good dispersity in the LCP material, a conductive path is formed, and the conductivity and the antistatic performance are improved.

Description

Technical Field

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

[0002] Thermotropic liquid crystal polyarylates possess excellent mechanical strength, high modulus, and heat resistance, making them important in protective equipment, automotive parts, and aerospace applications. However, their high resistivity and poor electrical conductivity and antistatic properties limit their practical applications. Polyimide, on the other hand, is a high-performance engineering material with strong high-temperature resistance and high structural stability, making it widely used. Combining polyimide and liquid crystal polyarylates can yield composite materials with even better performance.

[0003] Graphene oxide possesses high mechanical strength, high temperature resistance, and strong electrical conductivity, which can improve the performance of liquid crystal polyarylate materials. Patent CN103333324B discloses a method for preparing a graphene / thermotropic liquid crystal fully aromatic polyester composite material, which uses 6-hydroxy-2-naphthoic acid to non-covalently modify graphene oxide, resulting in excellent dispersion in thermotropic liquid crystal fully aromatic polyester resin. Compared to that patent, this application does not require modification of graphene oxide to improve the high temperature resistance, electrical conductivity, and other properties of liquid crystal polyarylate. Summary of the Invention

[0004] This invention solves the problems of low conductivity and high-temperature resistance in LCP liquid crystal polyarylate materials. The technical solution of this invention is: a method for preparing a high-temperature resistant, conductive, and thermally conductive graphene-LCP material.

[0005] Step S1: Under a nitrogen atmosphere, add pyridine, benzenesulfonyl chloride, and N,N-dimethylformamide to a flask equipped with a reflux condenser. After stirring, add a pyridine solution containing diacid dropwise and stir the reaction. Then, add a pyridine solution containing p-hydroxybenzoic acid and 4,4'-bis(4-hydroxyphthalimide)-benzamidobenzene dropwise and continue the reaction. Pour the solution into ethanol, filter it, wash the filter cake with ethanol and chloroform, and dry it to obtain liquid crystal polyarylate.

[0006] Step S2: Mix liquid crystal polyarylate and graphene oxide, add to a double cone mixer, and co-extrude to obtain high-temperature resistant, conductive and thermally conductive graphene-LCP material.

[0007] Preferably, the temperature during the stirring reaction in step S1 is 115-125℃, the reaction time is 15-30 min, and the reaction continues for 5-8 h.

[0008] Preferably, in step S1, the molar ratio of benzenesulfonyl chloride, N,N-dimethylformamide, diacid monomer, p-hydroxybenzoic acid, and 4,4′-bis(4-hydroxyphthalimide)-benzamidobenzene is (280-330):(3.4-4.2):(12-25):100:(12-25).

[0009] Preferably, the diacid monomer includes terephthalic acid or biphenyl dicarboxylic acid.

[0010] Preferably, in step S2, the mass ratio of liquid crystal polyarylate to graphene oxide is 100:(0.3-1).

[0011] Preferably, the mixing temperature in step S2 is 300-320℃.

[0012] Preferably, the heat treatment temperature in step S2 is 300-320℃ and the time is 6-12h.

[0013] Preferably, the preparation method of 4,4′-bis(4-hydroxyphthalimide)-benzamidobenzene includes the following steps: N-methylpyrrolidone, xylene, 4-hydroxyphthalic anhydride and 4,4′-diamino-benzoylaniline in a molar ratio of (200-220):100 are added to a flask equipped with a reflux condenser and a water separator. The mixture is first heated to 150-155°C and azeotropically dehydrated for 1-2 hours. Then, it is heated to 180-190°C and reacted for 7-10 hours. After cooling, the solution is poured into methanol, filtered, and the filter cake is washed with acetone and dried to obtain 4,4′-bis(4-hydroxyphthalimide)-benzamidobenzene.

[0014] The beneficial technical effects of this invention are as follows: In a catalytic system of benzenesulfonyl chloride and pyridine, a diacid monomer, p-hydroxybenzoic acid, and 4,4′-bis(4-hydroxyphthalimide)-benzamidobenzene undergo a carboxylation reaction to obtain a liquid crystal polyarylate. Then, it is blended with graphene oxide to obtain a high-temperature resistant conductive graphene-LCP material. The liquid crystal polyarylate molecular chain contains an imide ring, which has good structural stability, high rigidity, and strong heat resistance, which is beneficial to improving the thermal decomposition mass loss temperature of the liquid crystal polyarylate LCP material.

[0015] The liquid crystal polyarylate of this invention contains amide bonds, which form hydrogen bonds between molecular chains, increasing the degree of cross-linking and enhancing the heat resistance of the LCP. Furthermore, the amide bonds form strong interactions with the hydroxyl and carboxyl groups on the surface of graphene oxide, improving the interfacial compatibility between graphene oxide and the liquid crystal polyarylate. Graphene oxide exhibits excellent dispersibility in the LCP material without surface modification, forming conductive pathways, reducing resistance, and improving conductivity, which is beneficial for improving antistatic properties. The excellent dispersibility of graphene oxide can improve the high-temperature resistance of the LCP material, enabling it to exhibit a higher thermal decomposition mass loss temperature. Graphene itself has strong thermal conductivity; in the actual production process, adding an excess of graphene oxide to the LCP material can achieve a thermal conductivity of 3-5 W·m. -1 ·K -1 However, it does have some impact on the high-temperature resistance of the material. Detailed Implementation

[0016] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0017] The graphene oxide described below has a thickness of 0.6-1.2 nm and a diameter of 0.8-2 μm;

[0018] Example 1

[0019] (1) Add 80 mL of N-methylpyrrolidone, 40 mL of xylene, 100 mmol of 4-hydroxyphthalic anhydride, and 50 mmol of 4,4′-diamino-benzoylaniline to a flask equipped with a reflux condenser and a water separator. First, heat to 155 °C for azeotropic dehydration for 1 h, then heat to 180 °C and react for 10 h. After cooling, pour the solution into methanol, filter, wash the filter cake with acetone, and dry to obtain 4,4′-bis(4-hydroxyphthalimide)-benzamidobenzene. The preparation reaction formula is:

[0020]

[0021] (2) Under a nitrogen atmosphere, 1 L of pyridine, 3 mol of benzenesulfonyl chloride, and 37 mmol of N,N-dimethylformamide were added to a flask equipped with a reflux condenser. The mixture was stirred for 10 min, and 300 mL of a pyridine solution containing 0.12 mol of terephthalic acid was added dropwise. The mixture was heated to 125 °C and stirred for 15 min. Then, a pyridine solution containing 1 mol of p-hydroxybenzoic acid and 400 mL of a pyridine solution containing 0.12 mol of 4,4'-bis(4-hydroxyphthalimide)-benzamidobenzene was added dropwise. The reaction was continued for 7 h. The solution was poured into ethanol, filtered, and the filter cake was washed with ethanol and chloroform and dried to obtain liquid crystal polyarylate. The preparation reaction formula is:

[0022]

[0023] (3) Mix 1kg of liquid crystal polyarylate and 3g of graphene oxide, add them to a double cone mixer, and co-extrude at 300℃ to obtain high-temperature resistant, conductive and thermally conductive graphene-LCP material.

[0024] Example 2

[0025] (1) Add 90 mL of N-methylpyrrolidone, 50 mL of xylene, 110 mmol of 4-hydroxyphthalic anhydride and 50 mmol of 4,4'-diamino-benzoylaniline to a flask equipped with a reflux condenser and a water separator. First, heat to 150 °C and dehydrate azeotropically for 2 h. Then heat to 190 °C and react for 7 h. After cooling, pour the solution into methanol, filter, wash the filter cake with acetone, and dry to obtain 4,4'-bis(4-hydroxyphthalimide)-benzoamide benzene.

[0026] (2) In a nitrogen atmosphere, 1 L of pyridine, 2.8 mol of benzenesulfonyl chloride, and 34 mmol of N,N-dimethylformamide were added to a flask equipped with a reflux condenser. The mixture was stirred for 15 min, and 350 mL of a pyridine solution containing 0.25 mol of biphenyl dicarboxylic acid was added dropwise. The mixture was heated to 125 °C and stirred for 15 min. Then, a pyridine solution containing 1 mol of p-hydroxybenzoic acid and 450 mL of a pyridine solution containing 0.25 mol of 4,4'-bis(4-hydroxyphthalimide)-benzamidobenzene was added dropwise. The reaction was continued for 5 h. The solution was poured into ethanol, filtered, and the filter cake was washed with ethanol and chloroform. The filter cake was dried to obtain liquid crystal polyarylate.

[0027] (3) Mix 1kg of liquid crystal polyarylate and 7g of graphene oxide, add them to a double cone mixer, and co-extrude at 320℃ to obtain high temperature resistant, conductive and thermally conductive graphene-LCP material.

[0028] Example 3

[0029] (1) In a nitrogen atmosphere, 0.8 L of pyridine, 3.3 mol of benzenesulfonyl chloride, and 42 mmol of N,N-dimethylformamide were added to a flask equipped with a reflux condenser. The mixture was stirred for 10 min, and 350 mL of a pyridine solution containing 0.18 mol of terephthalic acid was added dropwise. The mixture was heated to 120 °C and stirred for 30 min. Then, a pyridine solution containing 1 mol of p-hydroxybenzoic acid and 450 mL of a pyridine solution containing 0.18 mol of 4,4'-bis(4-hydroxyphthalimide)-benzamidobenzene (prepared in the same way as in Example 1) was added dropwise. The mixture was continued to react for 8 h. The solution was poured into ethanol, filtered, and the filter cake was washed with ethanol and chloroform. The filter cake was then dried to obtain liquid crystal polyarylate.

[0030] (2) Mix 1kg of liquid crystal polyarylate and 10g of graphene oxide, add them to a double cone mixer, and co-extrude at 320℃ to obtain high-temperature resistant, conductive and thermally conductive graphene-LCP material.

[0031] Comparative Example 1

[0032] (1) In a nitrogen atmosphere, 1 L of pyridine, 3 mol of benzenesulfonyl chloride, and 37 mmol of N,N-dimethylformamide were added to a flask equipped with a reflux condenser. The mixture was stirred for 10 min, and 300 mL of a pyridine solution containing 0.12 mol of terephthalic acid was added dropwise. The mixture was heated to 125 °C and stirred for 15 min. Then, a pyridine solution containing 1 mol of p-hydroxybenzoic acid and 400 mL of a pyridine solution containing 0.12 mol of 4,4'-biphenyl was added dropwise. The mixture was continued to react for 7 h. The solution was poured into ethanol, filtered, and the filter cake was washed with ethanol and chloroform. The filter cake was then dried to obtain liquid crystal polyarylate.

[0033] (2) Mix 1kg of liquid crystal polyarylate and 3g of graphene oxide, add them to a double cone mixer, and co-extrude at 300℃ to obtain high-temperature resistant, conductive and thermally conductive graphene-LCP material.

[0034] Comparative Example 2

[0035] (1) Add 80 mL of N-methylpyrrolidone, 40 mL of xylene, 100 mmol of 4-hydroxyphthalic anhydride, and 50 mmol of p-phenylenediamine to a flask equipped with a reflux condenser and a water separator. First, heat to 155 °C for azeotropic dehydration for 1 h, then heat to 180 °C and react for 10 h. After cooling, pour the solution into methanol, filter, wash the filter cake with acetone, and dry to obtain 4,4'-bis(4-hydroxyphthalimide)benzene, with the following structural formula:

[0036] (2) In a nitrogen atmosphere, 1 L of pyridine, 3 mol of benzenesulfonyl chloride, and 37 mmol of N,N-dimethylformamide were added to a flask equipped with a reflux condenser. The mixture was stirred for 10 min, and 300 mL of a pyridine solution containing 0.12 mol of terephthalic acid was added dropwise. The mixture was heated to 125 °C and stirred for 15 min. Then, a pyridine solution containing 1 mol of p-hydroxybenzoic acid and 400 mL of a pyridine solution containing 0.12 mol of 4,4'-bis(4-hydroxyphthalimide)benzene was added dropwise. The reaction was continued for 7 h. The solution was poured into ethanol, filtered, and the filter cake was washed with ethanol and chloroform and dried to obtain liquid crystal polyarylate.

[0037] (3) Mix 1kg of liquid crystal polyarylate and 3g of graphene oxide, add them to a double cone mixer, and co-extrude at 300℃ to obtain high-temperature resistant, conductive and thermally conductive graphene-LCP material.

[0038] Comparative Example 3

[0039] (1) Add 5 mL of acetone, 1 mol of p-hydroxybenzoic acid, 3 mmol of 2-(7-azabenzotriazole)-N,N,N',N'-tetramethylurea hexafluorophosphate (HATU), 3 mmol of triethylamine, and 2 mol of p-hydroxyaniline to a flask. Stir the mixture at 25 °C for 16 h, then evaporate by rotary evaporation. Separate by column chromatography, using a gradient elution with ethyl acetate and petroleum ether to obtain 4-hydroxy-N-(4-hydroxyphenyl)benzamide, with the following structural formula:

[0040] (2) In a nitrogen atmosphere, 1 L of pyridine, 3 mol of benzenesulfonyl chloride, and 37 mmol of N,N-dimethylformamide were added to a flask equipped with a reflux condenser. The mixture was stirred for 10 min, and 300 mL of a pyridine solution containing 0.12 mol of terephthalic acid was added dropwise. The mixture was heated to 125 °C and stirred for 15 min. Then, a pyridine solution containing 1 mol of p-hydroxybenzoic acid and 400 mL of a pyridine solution containing 0.12 mol of 4-hydroxy-N-(4-hydroxyphenyl)benzamide was added dropwise. The mixture was reacted for 7 h. The solution was poured into ethanol, filtered, and the filter cake was washed with ethanol and chloroform. The filter cake was dried to obtain liquid crystal polyarylate.

[0041] (3) Mix 1kg of liquid crystal polyarylate and 3g of graphene oxide, add them to a double cone mixer, and co-extrude at 300℃ to obtain high-temperature resistant, conductive and thermally conductive graphene-LCP material.

[0042] Weigh 5 mg of graphene-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.

[0043] The volume resistivity of graphene-LCP materials was tested according to the method of GB / T 1410-2006 standard. Each group of samples was tested three times, and the average value was taken. The lower the volume resistivity, the better the conductivity and antistatic properties.

[0044] Table 1 Properties of graphene-LCP materials

[0045]

[0046] The graphene-LCP materials in Examples 1-3 exhibit high thermal decomposition mass loss temperature, excellent high-temperature resistance, and a resistivity of only 1.19 × 10⁻⁶. 7 -4.48×10 12 The conductivity of Ω·cm is relatively high, which is beneficial for improving antistatic properties. This is mainly because 4,4'-bis(4-hydroxyphthalimide)-benzamidobenzene is used as a comonomer, introducing imide rings and amide bonds into the liquid crystal polyarylate molecular chain. The imide ring has good structural stability, high rigidity, and strong heat resistance, which is beneficial for increasing the thermal decomposition mass loss temperature of the liquid crystal polyarylate LCP material. At the same time, the presence of amide bonds in the liquid crystal polyarylate leads to hydrogen bonding interactions between molecular chains, increasing the degree of cross-linking and enhancing the heat resistance of the material. The amide bonds form strong interactions with the hydroxyl and carboxyl groups on the surface of graphene oxide, which can improve the interfacial compatibility between graphene oxide and the liquid crystal polyarylate, resulting in better dispersion of graphene oxide in the LCP material, forming conductive pathways, reducing the resistance value, and improving conductivity. Furthermore, the better dispersion of graphene oxide can improve the high-temperature resistance of the LCP material, exhibiting a higher thermal decomposition mass loss temperature.

[0047] In Comparative Example 1, 4,4'-biphenyl was added during the preparation of liquid crystal polyarylate. The prepared liquid crystal polyarylate did not contain imide rings and amide bonds, resulting in a low thermal decomposition mass loss temperature and poor high-temperature resistance of the LCP material. Furthermore, it had poor interfacial compatibility with graphene oxide, which was not conducive to improving the dispersibility of graphene oxide and affected the conductivity and high-temperature resistance of the LCP material.

[0048] In Comparative Example 2, the 4,4'-bis(4-hydroxyphthalimide)benzene added during the preparation of liquid crystal polyarylate did not contain amide bonds, resulting in poor interfacial compatibility between the liquid crystal polyarylate and graphene oxide. This was not conducive to improving the dispersibility of graphene oxide and affected the conductivity and high-temperature resistance of the LCP material.

[0049] In Comparative Example 3, the 4-hydroxy-N-(4-hydroxyphenyl)benzamide added during the preparation of liquid crystal polyarylate did not contain an imide ring, resulting in lower high-temperature resistance of the LCP material.

[0050] Of course, those skilled in the art will understand that the embodiments described above are merely some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. A method for preparing a high-temperature resistant, electrically and thermally conductive graphene-LCP material, characterized in that, The preparation method includes the following steps: Step S1: Under a nitrogen atmosphere, add pyridine, N,N-dimethylformamide, and benzenesulfonyl chloride to a flask equipped with a reflux condenser. After stirring, add a pyridine solution containing diacid dropwise and stir the reaction. Then, add a pyridine solution containing p-hydroxybenzoic acid and 4,4′-bis(4-hydroxyphthalimide)-benzamidobenzene dropwise and continue the reaction. Pour the solution into ethanol, filter, wash the filter cake, and dry it to obtain liquid crystal polyarylate. Step S2: Mix liquid crystal polyarylate and graphene oxide, add to a double cone mixer, and co-extrude to obtain high-temperature resistant, conductive and thermally conductive graphene-LCP material.

2. The preparation method of the high-temperature resistant, electrically and thermally conductive graphene-LCP material according to claim 1, characterized in that, In step S1, the temperature during the stirring reaction is 115-125℃, the reaction time is 15-30 min, and the reaction continues for 5-8 h.

3. The preparation method of the high-temperature resistant, conductive, and thermally conductive graphene-LCP material according to claim 1, characterized in that, In step S1, the molar ratio of benzenesulfonyl chloride, N,N-dimethylformamide, diacid monomer, p-hydroxybenzoic acid, and 4,4′-bis(4-hydroxyphthalimide)-benzamidobenzene is (280-330):(3.4-4.2):(12-25):100:(12-25).

4. The preparation method of the high-temperature resistant, conductive, and thermally conductive graphene-LCP material according to claim 3, characterized in that, The dicarboxylic acid monomers include terephthalic acid or biphenyl dicarboxylic acid.

5. The preparation method of the high-temperature resistant, conductive, and thermally conductive graphene-LCP material according to claim 1, characterized in that, The preparation method of the 4,4'-bis(4-hydroxyphthalimide)-benzamidobenzene includes the following steps: N-methylpyrrolidone, xylene, 4-hydroxyphthalic anhydride and 4,4'-diamino-benzoylaniline in a molar ratio of (200-220):100 are added to a flask equipped with a reflux condenser and a water separator. The mixture is first heated to 150-155℃ and azeotropically dehydrated for 1-2 hours. Then it is heated to 180-190℃ and reacted for 7-10 hours. After cooling, the solution is poured into methanol, filtered, the filter cake is washed, and dried to obtain 4,4'-bis(4-hydroxyphthalimide)-benzamidobenzene.

6. The method for preparing high-temperature resistant, electrically and thermally conductive graphene-LCP material according to claim 1, characterized in that, In step S2, the mass ratio of liquid crystal polyarylate to graphene oxide is 100:(0.3-1).

7. The method for preparing high-temperature resistant, electrically and thermally conductive graphene-LCP material according to claim 1, characterized in that, The mixing temperature in step S2 is 300-320℃.

8. A high-temperature resistant, conductive, and thermally conductive graphene-LCP material obtained by the preparation method according to any one of claims 1-7.

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