Preparation method and application of high-strength graphene modified polycarbonate

Abstract

The application discloses a preparation method and application of high-strength graphene modified polycarbonate, and the method comprises the following steps: hydrophobic and oleophilic modification of graphene oxide; surface modification of the hydrophobic and oleophilic modified graphene oxide by taking low-molecular-weight polycarbonate as a modifier; and preparation of the high-strength graphene modified polycarbonate by taking the surface-modified graphene oxide as an additive through a solution blending method. The application also provides an application of the high-strength graphene modified polycarbonate, and the high-strength graphene modified polycarbonate is used for automobile parts, and is particularly used for an outer frame of a new energy automobile sensor. The surface modification of the hydrophobic and oleophilic modified graphene oxide can effectively improve the mechanical properties of the material, and the material can also maintain good optical properties, wear resistance and weather resistance, so that the material is suitable for being used as an outer frame material of the new energy automobile sensor, and the quality of the new energy automobile is improved.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of polycarbonate materials, and relates to a preparation method and application of high-strength graphene-modified polycarbonate. BACKGROUND

[0002] Polycarbonate (PC for short) is a high-molecular polymer containing carbonate groups in the molecular chain, and can be divided into aliphatic, aromatic and aliphatic-aromatic types according to the structure of the ester group. The polycarbonate is a strong and tough thermoplastic resin and has a large number of applications in modern industry.

[0003] Graphene is a two-dimensional atomic-scale hexagonal carbon allotrope, and graphene oxide is an oxide of graphene. The addition of graphene oxide can improve the strength of the material, delay the aging process of the material and improve the service life and reliability of the automobile parts.

[0004] There are a large number of sensors in new energy vehicles, and these sensors need a safe and stable environment for installation. The impact strength of polycarbonate is extremely high and even exceeds that of some metals, and polycarbonate is not easy to break and is often called "transparent metal". It can be transparent like glass, but is much lighter, and is an ideal material for making transparent products. Polycarbonate is easy to shape and can produce complex shapes and thin-walled structures, which enables designers to integrate the sensor outer frame with other parts of the new energy vehicle and hide the sensor in the vehicle body decoration, achieving integrated design, which is not only beautiful but also saves space. With the promotion of new energy vehicles from electrification to intelligence, laser radar, millimeter wave radar and other sensors are widely used in new energy vehicles. Laser radar and millimeter wave radar need to be installed on new energy vehicles, and the existing polycarbonate material needs to be further studied so that it has high strength, weather resistance, wear resistance and transparency on the basis of the impact resistance, easy processing and heat resistance of traditional polycarbonate materials. The material obtained in this way can obtain a sensor outer frame for protecting the laser radar, millimeter wave radar and other sensors of the new energy vehicle, so that the sensors can continuously and stably operate in harsh environments and improve the quality of the new energy vehicle. Therefore, a preparation method of high-strength graphene-modified polycarbonate is needed. SUMMARY

[0005] In order to overcome the defects in the prior art, a preparation method and application of high-strength graphene-modified polycarbonate are provided.

[0006] The application is realized through the following scheme:

[0007] A preparation method of high-strength graphene-modified polycarbonate, in terms of mass parts, comprises the following steps:

[0008] Step 1: hydrophobic-lipophilic modification of graphene oxide: ultrasonically disperse 2-4 parts of dried graphene oxide in 800-1200 parts of xylene; add 2-4 parts of octadecylamine, ultrasonically treat for 1-3 hours, transfer to a reaction vessel, maintain the temperature at 145-150° C., react for 24-72 hours, and continuously stir during the reaction; after the reaction, cool the reaction solution, centrifuge, wash with ethanol, and finally ultrasonically disperse in water. After freeze-drying, hydrophobic-lipophilic modified graphene oxide is obtained;

[0009] Step 2: Surface-modifying the hydrophobically lipophilically modified graphene oxide obtained in step 1 with a low molecular weight polycarbonate as a modifier: dissolving the low molecular weight polycarbonate in tetrahydrofuran to obtain a low molecular weight polycarbonate solution with a concentration of 4-6 g / 100 mL; then adding 1-2 g / 100 mL of the hydrophobically lipophilically modified graphene oxide to the low molecular weight polycarbonate solution, mixing well, and then ultrasonically reacting for 12-36 hours to obtain the surface-modified graphene oxide;

[0010] Step 3: Using the surface-modified graphene oxide obtained in step 2 as an additive, a high-strength graphene-modified polycarbonate is prepared by a solution blending method: the surface-modified graphene oxide is added to an N,N-dimethylacetamide solvent to prepare a 1 mg / mL surface-modified graphene oxide suspension, and after ultrasonic dispersion, it is added to the N,N-dimethylacetamide solvent containing polycarbonate; subsequently, a modifier, an antioxidant, and an ultraviolet absorber are added, and the mass ratio of the modifier, antioxidant, ultraviolet absorber, surface-modified graphene oxide, and polycarbonate is 0.3-0.6:0.1-0.3:0.1-0.3:1-5:100, and the reaction is stirred at 35-45°C for 6-12 hours. After the mixed solution is dried, a high-strength graphene-modified polycarbonate is obtained.

[0011] In step 1, the graphene oxide consists of graphene oxide A and graphene oxide B, and the mass ratio of graphene oxide A to graphene oxide B is 2-4:6-8; the graphene oxide A and graphene oxide B are purchased from Shanghai Yuanye Biotechnology Co., Ltd., with product numbers S28018 and S24800 respectively.

[0012] The graphene oxide A has a thickness of 0.33-1 nm and a sheet diameter of 0.5-5 μm;

[0013] The graphene oxide B has a thickness of 1 nm and a sheet diameter of 0.2-10 μm.

[0014] The surface hardness of ordinary polycarbonate on the market is relatively low, and the wear resistance is poor. When it is applied to the outer frame of a new energy vehicle sensor, scratches and wear are likely to occur in the use scene of frequent wind, sand and rain wiping, which will affect the normal use of the internal sensor. Although the surface performance can be enhanced by coating or composite modification, it will increase the cost and complexity. The addition of graphene oxide not only can increase the mechanical properties of the material, but also can improve the weather resistance and oxidation resistance of the material, delay the aging process of the material, and improve the service life and reliability of the automobile parts. However, the ordinary graphene oxide has strong van der Waals force between the layers, which is easy to agglomerate, resulting in the formation of aggregation in the composite material, affecting the uniformity of the material performance and the overall enhancement effect. In addition, the interface interaction between graphene oxide and polycarbonate is weak, which may limit the effective transmission of the excellent performance of graphene oxide to the composite material. The inventors found that the hydrophobic and oleophilic modification of graphene oxide can improve its dispersibility in the system, and the reason may be that the relative content of oxygen elements on the surface of the modified graphene oxide increases significantly, which can form various oxygen-containing groups, further improving the hydrophobicity and oleophilicity of graphene oxide, so that it can be better applied in hydrophobic and oleophilic environments.

[0015] The hydrophobic and oleophilic modified graphene oxide can improve its dispersibility in polycarbonate to some extent. Polycarbonate is a non-polar polymer, while graphene oxide surface is rich in polar functional groups, which leads to poor compatibility between the two. Poor interface compatibility will limit the uniform dispersion of graphene oxide nanosheet in the polycarbonate matrix, affect the overall performance of the composite material, and may cause the mechanical property improvement not obvious or uneven dispersion leading to local stress concentration. To solve this problem, the inventors modified the surface of graphene oxide with low molecular weight polycarbonate as modifier, in order to form a polymer adhesion layer on the surface of graphene oxide. The commercially available polycarbonate matrix material generally has high molecular weight and poor dispersibility, while the self-made low molecular weight polycarbonate has higher interfacial interaction with graphene oxide. It is speculated that the low molecular weight polycarbonate has a certain reactivity due to its low relative molecular mass, which can form chemical bonds or hydrogen bonds with the oxygen-containing functional groups on the surface of the hydrophobic and oleophilic modified graphene oxide. On the other hand, the molecular main chain itself is bisphenol A type polycarbonate, which has good compatibility with polycarbonate matrix and has the potential to improve the interface performance of polycarbonate material.

[0016] In step three, the polycarbonate includes polycarbonate A, polycarbonate B and polycarbonate C, and the mass ratio of the polycarbonate A, polycarbonate B and polycarbonate C is 1-3:6-8:5-7.

[0017] The applicant has found that when the polycarbonate is compounded in the above ratio in this system, the prepared material has strong light stability and high transmittance, can obtain high transparency, and also has strong impact resistance, weather resistance, and wear resistance.

[0018] Polycarbonate A, polycarbonate B, and polycarbonate C were all purchased from Covestro, Germany, and distributed by Shanghai Xingyun International Trading Co., Ltd. Polycarbonate A was Makrolon brand 1804 polycarbonate. Polycarbonate B was Makrolon brand AX2677 polycarbonate. Polycarbonate C was Makrolon brand LED2247 polycarbonate.

[0019] The physical properties of the polycarbonate A are as follows: viscosity: high viscosity; flame retardant grade: V-2·V-0; melt index: 6.0 cm 3 / 10min; Notch impact: 70kJ / m 2 ; Heat deformation temperature: 140℃;

[0020] The physical properties of the polycarbonate B are as follows: viscosity: medium viscosity; melt index: 12 cm 3 / 10min; Notch impact: 70kJ / m 2 : Heat deformation temperature: 135℃;

[0021] The physical properties of the polycarbonate C are as follows: viscosity: low viscosity; flame retardant grade: HB·V-2; melt index: 34cm 3 / 10min; Notch impact: 65kJ / m 2 ; Heat deformation temperature: 136℃.

[0022] In step 2, the low molecular weight polycarbonate is prepared by esterification reaction.

[0023] The number average molecular weight of the low molecular weight polycarbonate is not greater than 4000, the weight average molecular weight is not greater than 6000, and the relative proportion of molecular chain terminal hydroxyl groups of the low molecular weight polycarbonate is not less than 60%.

[0024] In step 2, the preparation method of the low molecular weight polycarbonate is as follows: bisphenol A is recrystallized from toluene and vacuum dried at 60° C.; diphenyl carbonate is recrystallized from methanol and vacuum dried at room temperature; bisphenol A and diphenyl carbonate are added to a reactor in equal amounts, stirred under nitrogen, and heated to 50° C. until the monomers melt, sodium benzoate is added in an amount of 0.1% wt after melting, and then a pre-prepared NaOH solution is added, and the reaction is maintained at 150° C. for 0.5 h, and then the temperature is raised to 170° C., 190° C., and 230° C. for 0.5 h each, and then vacuumed for 15 min to remove the by-product phenol, and cooled to obtain a crude product; the crude product is dissolved in tetrahydrofuran, and then precipitated with 3 volumes of anhydrous ethanol to remove unreacted raw materials or residual phenol, and dried by air to obtain a low molecular weight polycarbonate finished product.

[0025] The addition of surface-modified graphene oxide as an additive in the present invention can significantly improve the mechanical properties of the material. Although the surface-modified graphene oxide only accounts for 1-5% compared to polycarbonate, these additives will affect the transparency of the material, which may affect the normal operation of the sensor in the outer frame. How to maintain the mechanical properties of the material to the greatest extent without affecting the original optical properties of polycarbonate is a practical problem that needs to be overcome.

[0026] To address this issue, the general approach in the prior art is to change the transparency of the material by adding nucleating agents and optical clarifiers. However, this approach suffers from disadvantages such as poor thermal stability, high cost, and compatibility limitations. During high-temperature processing or long-term use, the nucleating agent may thermally degrade, affecting the long-term performance and stability of the product. For large-scale applications, the cost-effectiveness ratio needs to be carefully considered. Furthermore, the sorbitol derivative nucleating agent cannot be fully compatible with the polycarbonate system of the present invention, and may affect the optical and mechanical properties of the final product.

[0027] The present invention has found in research that sodium benzoate, as an esterification catalyst, has a better effect on removing the byproduct phenol in the subsequent separation and purification process after the reaction process is completed. Due to the physicochemical properties of sodium benzoate, it is impossible to separate sodium benzoate efficiently and at low cost. However, it was unexpectedly found that sodium benzoate remaining in the polycarbonate product can improve mechanical properties and transparency. This may be because sodium benzoate, as a catalyst, is deeply involved in the esterification reaction of polycarbonate production, which can promote the reaction of monomers such as bisphenol A and diphenyl carbonate to form polycarbonate polymer chains. After the reaction is completed, these sodium benzoates will naturally be distributed in the polycarbonate product and will be basically evenly distributed. During the reaction process, the polycarbonate polymer chains are more likely to start nucleation when they transition from a molten state to a crystalline state. This causes the crystallization process to shift from homogeneous nucleation to heterogeneous nucleation, which may occur on the surface of sodium benzoate. Heterogeneous nucleation generally requires a lower energy barrier than homogeneous nucleation, so the crystallization process is accelerated, significantly increasing the number of crystal nuclei and resulting in a reduction in the size of each crystal grain. Smaller grains scatter less light, improving the transparency of polycarbonate products. A fine and uniform distribution of grains reduces stress concentration within the material, allowing fine grains to absorb more energy without breaking. Consequently, grain refinement also improves the material's impact strength and toughness. This overcomes the inherent transparency and performance deficiencies of low-molecular-weight polycarbonate, enabling its use as a modification target for graphene oxide without compromising the optical and mechanical properties of the final product. Furthermore, improving the crystal structure enhances the material's overall stability and resistance to environmental stress cracking. All of this occurs without the addition of any additional additives or preparation methods, significantly improving efficiency while maintaining production costs.

[0028] In the present invention, bisphenol A was purchased from Jinan Century Tongda Chemical Co., Ltd., and its parameters are as follows: melting point 158-159°C, boiling point 400.8°C, density 1.195 g / cm 3 , flash point 227℃, appearance is white needle crystal or flaky powder.

[0029] In step 2, the concentration of the NaOH solution is 0.057 g / mL, and the vacuum degree of the vacuum pumping is less than 100 Pa.

[0030] In step 3, the modifier is polytetrafluoroethylene, which was purchased from Shanghai Yuanye Biotechnology Co., Ltd. with a product number of S24392.

[0031] In step 3, the antioxidant was purchased from Tianjin Li'anlong New Materials Co., Ltd., model number 1010. The ultraviolet absorber was purchased from Tianjin Li'anlong New Materials Co., Ltd., model number UV-326.

[0032] The application further provides application of the high-strength graphene modified polycarbonate to automobile parts, in particular to the outer frame of a new energy automobile sensor.

[0033] The application has the following beneficial effects:

[0034] The preparation method of the high-strength graphene modified polycarbonate adopts low-molecular-weight polycarbonate as a modifier to modify the surface of hydrophobic and oleophilic modified graphene oxide, effectively improves the compatibility of graphene oxide and polycarbonate, realizes the uniform distribution of graphene oxide in the polycarbonate matrix and obtains good reinforcing effect, the modification method is convenient and simple, has low cost, can effectively improve the mechanical properties of the material, and can also maintain good optical properties, wear resistance and weather resistance, so that it is suitable as an outer frame material of a new energy automobile sensor, thereby improving the quality of the new energy automobile. DETAILED DESCRIPTION

[0035] The application will be further described below in combination with specific examples and comparative examples:

[0036] Example 1

[0037] A preparation method of a high-strength graphene modified polycarbonate, in terms of mass parts, includes the following steps:

[0038] Step one, hydrophobic and oleophilic modification of graphene oxide: 4 parts of dried graphene oxide is ultrasonically dispersed in 1000 parts of dimethylbenzene; 2 parts of octadecylamine is added, ultrasonic treatment is performed for 3 hours, and then it is transferred into a reaction container to keep the temperature at 147 DEG C for 24 hours, and stirring is continuously performed during the reaction; after the reaction is completed, the reaction liquid is cooled, centrifugal separation is performed, ethanol is used for washing, and finally ultrasonic dispersion is performed in water, and freeze-drying is performed to obtain hydrophobic and oleophilic modified graphene oxide;

[0039] Step two, surface modification of the hydrophobic and oleophilic modified graphene oxide obtained in step one by using low-molecular-weight polycarbonate as a modifier: low-molecular-weight polycarbonate is dissolved in tetrahydrofuran to obtain a low-molecular-weight polycarbonate solution with a concentration of 6 g / 100 mL; then 1.5 g / 100 mL of the hydrophobic and oleophilic modified graphene oxide is added to the low-molecular-weight polycarbonate solution, and after being uniformly mixed, ultrasonic reaction is performed for 12 hours to obtain surface-modified graphene oxide;

[0040] Step 3. Using the surface-modified graphene oxide obtained in step 2 as an additive, a high-strength graphene-modified polycarbonate is prepared by a solution blending method: the surface-modified graphene oxide is added to an N,N-dimethylacetamide solvent to form a 1 mg / mL surface-modified graphene oxide suspension, and after ultrasonic dispersion, it is added to the N,N-dimethylacetamide solvent containing polycarbonate; subsequently, a modifier, an antioxidant, and an ultraviolet absorber are added, and the mass ratio of the modifier, antioxidant, ultraviolet absorber, surface-modified graphene oxide, and polycarbonate is 0.6:0.2:0.1:5:100. The reaction is stirred at 40°C for 6 hours, and the mixed solution is dried to obtain a high-strength graphene-modified polycarbonate.

[0041] In step 1, the graphene oxide consists of graphene oxide A and graphene oxide B, and the mass ratio of graphene oxide A to graphene oxide B is 4:7;

[0042] The graphene oxide A has a thickness of 0.33-1 nm and a sheet diameter of 0.5-5 μm;

[0043] The graphene oxide B has a thickness of 1 nm and a sheet diameter of 0.2-10 μm.

[0044] In step 3, the polycarbonate includes polycarbonate A, polycarbonate B and polycarbonate C, and the mass ratio of polycarbonate A, polycarbonate B and polycarbonate C is 1:8:6;

[0045] The physical properties of the polycarbonate A are as follows: viscosity: high viscosity; flame retardant grade: V-2·V-0; melt index: 6.0 cm 3 / 10min; Notch impact: 70kJ / m 2 ; Heat deformation temperature: 140℃;

[0046] The physical properties of the polycarbonate B are as follows: viscosity: medium viscosity; melt index: 12 cm 3 / 10min; Notch impact: 70kJ / m 2 : Heat deformation temperature: 135℃;

[0047] The physical properties of the polycarbonate C are as follows: viscosity: low viscosity; flame retardant grade: HB·V-2; melt index: 34cm 3 / 10min; Notch impact: 65kJ / m 2 ; Heat deformation temperature: 136℃.

[0048] In step 2, the low molecular weight polycarbonate is prepared by esterification reaction.

[0049] The low-molecular-weight polycarbonate has a number average molecular weight of not more than 4000 and a weight average molecular weight of not more than 6000, and the relative proportion of the molecular chain end hydroxyl group of the low-molecular-weight polycarbonate is not less than 60%.

[0050] The preparation method of the low-molecular-weight polycarbonate comprises the following steps: recrystallizing bisphenol A with toluene and vacuum drying at 60 DEG C; recrystallizing diphenyl carbonate with methanol and vacuum drying at room temperature; adding bisphenol A and diphenyl carbonate into a reactor according to the same amount of substance, stirring and heating to 50 DEG C under nitrogen until the monomers are melted, adding sodium benzoate according to the amount of 0.1% wt after melting, then adding a previously prepared NaOH solution to make the pH value of the reaction system 9, and keeping the reaction at 150 DEG C for 0.5 h, then heating at 170 DEG C, 190 DEG C and 230 DEG C respectively for 0.5 h, and then vacuumizing for 15 min to remove the by-product phenol, and obtaining the crude product after cooling; dissolving the crude product in tetrahydrofuran, precipitating with 3 times the volume of anhydrous ethanol to remove unreacted raw materials or residual phenol, and blowing and drying to obtain the finished low-molecular-weight polycarbonate.

[0051] In step two, the concentration of the NaOH solution is 0.057 g / mL, and the vacuum degree of the vacuumizing is less than 100 Pa.

[0052] In step three, the modifier is polytetrafluoroethylene; the antioxidant is antioxidant 1010; and the ultraviolet absorber is UV-326.

[0053] The application further provides a use of the high-strength graphene-modified polycarbonate, and the high-strength graphene-modified polycarbonate is used for automobile parts, in particular, is used for the outer frame of a new energy automobile sensor.

[0054] Example 2

[0055] A preparation method of a high-strength graphene-modified polycarbonate, and the specific implementation manner is the same as that in example 1, and the difference lies in that the method comprises the following steps in terms of mass parts:

[0056] Step one, hydrophobic and oleophilic modification of graphene oxide: 2 parts of dried graphene oxide are ultrasonically dispersed in 1200 parts of dimethylbenzene; 3 parts of octadecylamine are added, ultrasonic treatment is performed for 1 hour, and then the reaction container is transferred and kept at a temperature of 150 DEG C for reaction for 36 hours, and stirring is continuously performed during the reaction; after the reaction is completed, the reaction liquid is cooled, centrifugal separation is performed, ethanol is used for washing, and finally ultrasonic dispersion is performed in water, and freeze drying is performed to obtain the hydrophobic and oleophilic modified graphene oxide;

[0057] Step 2: Surface-modifying the hydrophobically oleophilically modified graphene oxide obtained in step 1 with a low molecular weight polycarbonate as a modifier: dissolving the low molecular weight polycarbonate in tetrahydrofuran to obtain a low molecular weight polycarbonate solution with a concentration of 4 g / 100 mL; then adding 2 g / 100 mL of the hydrophobically oleophilically modified graphene oxide to the low molecular weight polycarbonate solution, mixing well, and then ultrasonically reacting for 24 hours to obtain surface-modified graphene oxide;

[0058] Step 3. Using the surface-modified graphene oxide obtained in step 2 as an additive, a high-strength graphene-modified polycarbonate is prepared by a solution blending method: the surface-modified graphene oxide is added to an N,N-dimethylacetamide solvent to form a 1 mg / mL surface-modified graphene oxide suspension, and after ultrasonic dispersion, it is added to the N,N-dimethylacetamide solvent containing polycarbonate; subsequently, a modifier, an antioxidant, and an ultraviolet absorber are added, and the mass ratio of the modifier, antioxidant, ultraviolet absorber, surface-modified graphene oxide, and polycarbonate is 0.3:0.3:0.2:1:100. The reaction is stirred at 45°C for 9 hours, and the mixed solution is dried to obtain a high-strength graphene-modified polycarbonate.

[0059] In step 1, the graphene oxide consists of graphene oxide A and graphene oxide B, and the mass ratio of graphene oxide A to graphene oxide B is 2:8;

[0060] In step 3, the polycarbonate includes polycarbonate A, polycarbonate B and polycarbonate C, and the mass ratio of polycarbonate A, polycarbonate B and polycarbonate C is 2:6:7;

[0061] Example 3

[0062] A method for preparing high-strength graphene-modified polycarbonate, the specific implementation method is the same as Example 1, except that, based on parts by mass, the method comprises the following steps:

[0063] Step 1: hydrophobic-lipophilic modification of graphene oxide: 3 parts of dried graphene oxide are ultrasonically dispersed in 800 parts of xylene; 4 parts of octadecylamine are added, and the mixture is ultrasonically treated for 2 hours, and then transferred into a reaction vessel and maintained at a temperature of 145° C. for 72 hours, with continuous stirring during the reaction; after the reaction, the reaction solution is cooled, centrifuged, washed with ethanol, and finally ultrasonically dispersed in water. After freeze-drying, hydrophobic-lipophilic modified graphene oxide is obtained;

[0064] Step 2: Surface-modifying the hydrophobically oleophilically modified graphene oxide obtained in step 1 with a low molecular weight polycarbonate as a modifier: dissolving the low molecular weight polycarbonate in tetrahydrofuran to obtain a low molecular weight polycarbonate solution with a concentration of 5 g / 100 mL; then adding 1 g / 100 mL of the hydrophobically oleophilically modified graphene oxide to the low molecular weight polycarbonate solution, mixing well, and then ultrasonically reacting for 36 hours to obtain surface-modified graphene oxide;

[0065] Step 3. Using the surface-modified graphene oxide obtained in step 2 as an additive, a high-strength graphene-modified polycarbonate is prepared by a solution blending method: the surface-modified graphene oxide is added to an N,N-dimethylacetamide solvent to form a 1 mg / mL surface-modified graphene oxide suspension, and after ultrasonic dispersion, it is added to the N,N-dimethylacetamide solvent containing polycarbonate; subsequently, a modifier, an antioxidant, and an ultraviolet absorber are added, and the mass ratio of the modifier, antioxidant, ultraviolet absorber, surface-modified graphene oxide, and polycarbonate is 0.5:0.1:0.3:3:100. The reaction is stirred at 35°C for 12 hours, and the mixed solution is dried to obtain a high-strength graphene-modified polycarbonate.

[0066] In step 1, the graphene oxide consists of graphene oxide A and graphene oxide B, and the mass ratio of graphene oxide A to graphene oxide B is 3:6;

[0067] In step 3, the polycarbonate includes polycarbonate A, polycarbonate B and polycarbonate C, and the mass ratio of polycarbonate A, polycarbonate B and polycarbonate C is 3:7:5;

[0068] Comparative Example 1

[0069] The similarities between this comparative example and Example 3 are not repeated here, and the differences are as follows:

[0070] Steps 1 and 2 are not performed. In step 3, the additive is graphene oxide, and the graphene oxide consists of graphene oxide A and graphene oxide B. The mass ratio of graphene oxide A to graphene oxide B is 3:6; the graphene oxide A has a thickness of 0.33-1 nm and a sheet diameter of 0.5-5 μm; the graphene oxide B has a thickness of 1 nm and a sheet diameter of 0.2-10 μm.

[0071] Comparative Example 2

[0072] The similarities between this comparative example and Example 3 are not repeated here, and the differences are as follows:

[0073] The physical properties of graphene oxide are different. The graphene oxide sheet has a diameter of 0.5-5 μm and a thickness of 0.8-1.2 nm and was purchased from Xianfeng Nano.

[0074] Comparative Example 3

[0075] The similarities between this comparative example and Example 3 are not repeated here, and the differences are as follows:

[0076] In step three, the polycarbonate includes polycarbonate A, polycarbonate B and polycarbonate C, and the mass ratio of polycarbonate A, polycarbonate B and polycarbonate C is 1:1:1.

[0077] Comparative Example 4

[0078] The similarities between this comparative example and Example 3 are not repeated here, and the differences are as follows:

[0079] In step 2, the preparation method of the low molecular weight polycarbonate is as follows: bisphenol A is recrystallized from toluene and vacuum dried at 60°C; diphenyl carbonate is recrystallized from methanol and vacuum dried at room temperature; bisphenol A and diphenyl carbonate are added to a reactor in equal amounts, stirred with nitrogen, and heated to 50°C until the monomers melt, then a pre-prepared NaOH solution is added and maintained at 150°C for reaction for 0.5h, then heated to 170°C, 190°C and 230°C for reaction for 0.5h each, then vacuumed for 15min to remove the by-product phenol, and cooled to obtain a crude product; the crude product is dissolved in tetrahydrofuran, then precipitated with 3 times the volume of anhydrous ethanol to remove unreacted raw materials or residual phenol, and dried by air to obtain a low molecular weight polycarbonate finished product.

[0080] Comparative Example 5

[0081] The similarities between this comparative example and Example 3 are not repeated here, and the differences are as follows:

[0082] In step 2, the modified substance is a commercially available high molecular weight polycarbonate, and the other steps are the same. The commercially available high molecular weight polycarbonate was purchased from Shanghai Zhenzhun Biotechnology Co., Ltd., with a product number of 34036186, a number average molecular weight of 17,000, and a weight average molecular weight of 28,200.

[0083] Comparative Example 6

[0084] The similarities between this comparative example and Example 3 are not repeated here, and the differences are as follows:

[0085] The mass ratio of the modifier, antioxidant, ultraviolet absorber, surface-modified graphene oxide and polycarbonate is 05:0.1:7:100.

[0086] 1. Mechanical properties test

[0087] The mixture of the above samples was extruded using a twin-screw extruder at 270°C; the extrudate was injected into a flat-plate vulcanizer and hot-pressed for 5 minutes to obtain composite material specimens of the above samples. These composite material specimens were subjected to the following tests: tensile strength was tested according to GB / T 1040.1-2018, flexural strength was tested according to GB / T 9341-2008, and impact strength was tested according to GB / T1843-2008.

[0088] As can be seen from Table 1, after the addition of surface-modified graphene oxide, the tensile strength, flexural strength and impact strength of the sample are all increased; the reason may be that the honeycomb network structure of the added surface-modified graphene oxide is easy to absorb energy and avoid stress concentration when subjected to external loads; the surface-modified graphene oxide has high strength and can improve the mechanical properties of the material.

[0089] Table 1 Mechanical properties test results

[0090] Analyze samples Flexural strength (MPa) Tensile strength (MPa) Impact strength (kJ / m 2 ) Example 1 159.6 92.6 85.3 Example 2 157.7 91.1 86.2 Example 3 166.3 93.9 86.8 Comparative Example 1 128.4 82.1 80.6 Comparative Example 2 135.3 81.7 75.8 Comparative Example 3 137.6 83.1 81.3 Comparative Example 4 120.1 79.9 73.9 Comparative Example 5 121.9 80.3 75.2 Comparative Example 6 132.3 82.3 76.9

[0091] 2. Abrasion resistance and transparency performance test

[0092] Specimens were prepared using the same methods as described in the mechanical properties test as described in Examples 1-3 and Comparative Examples 1-6. Visible light transmittance is an important parameter for characterizing material transparency, and is used in this invention to characterize transparency. Visible light transmittance of the specimens was measured using a CARY 500 UV-Visible absorption spectrometer (Varian, USA). The specimen surfaces were tested for pencil hardness according to GB / T6739-1996. Hardness indirectly reflects a material's resistance to scratching; higher hardness levels indicate better wear resistance.

[0093] Table 2 Abrasion resistance and transparency test results

[0094]

[0095] As can be seen from Table 2, the visible light transmittance of the embodiments of the present invention is above 90%, far exceeding the visible light transmittance of the comparative examples, especially the transmittance of comparative example 4. The hardness of the embodiments of the present invention is significantly higher than that of the comparative examples.

[0096] 3. Weather resistance test

[0097] The samples in Examples 1-3 and Comparative Examples 1-6 were made into test specimens with reference to the method in the mechanical property test. The weather resistance test in the present invention uses the method of ASTM G155-232 of the United States to evaluate the weather resistance of the samples. Among them, the spectral irradiation wavelength is 340nm, the temperature and humidity are 38°C, RH 50%, and the cycle time of each watering and stopping watering is 120min in total, of which the watering is 18min. The mechanical property test is carried out after 50 cycles. The mechanical properties after 50 cycles of light erosion are shown in Table 3. The mechanical property results of the samples that have not been subjected to cyclic light erosion are shown in the results in Table 1. It can be seen from the results of the two comparative examples that the mechanical properties of the samples of Comparative Examples 1-6 have declined significantly, among which the impact strength has declined the most, and some have even exceeded 50%. Although the mechanical properties of Examples 1-3 of the present invention have also declined, the magnitude is not very large.

[0098] Table 3 Weather resistance test results

[0099]

[0100] Although the technical solutions of the present invention have been described and listed in detail, it should be understood that it is obvious to those skilled in the art to make modifications to the above embodiments or adopt equivalent alternatives. These modifications or improvements made without departing from the spirit of the present invention are within the scope of protection claimed by the present invention.

Claims

1. A method for preparing high-strength graphene-modified polycarbonate, characterized in that: In parts by mass, the method comprises the following steps: Step 1: hydrophobically and oleophilically modifying graphene oxide: ultrasonically dispersing 2-4 parts of dried graphene oxide in 800-1200 parts of xylene; adding 2-4 parts of octadecylamine, ultrasonically treating for 1-3 hours, transferring the resulting mixture into a reaction vessel, maintaining the temperature at 145-150°C, and reacting for 24-72 hours, with continuous stirring during the reaction; after the reaction, cooling the reaction solution, centrifuging, washing with ethanol, and finally ultrasonically dispersing it in water. After freeze-drying, hydrophobically and oleophilically modified graphene oxide is obtained; the graphene oxide comprises graphene oxide A and graphene oxide B, wherein the mass ratio of graphene oxide A to graphene oxide B is 2-4:6-8; the graphene oxide A has a thickness of 0.33-1 nm and a flake diameter of 0.5-5 μm; the graphene oxide B has a thickness of 1 nm and a flake diameter of 0.2-10 μm; Step 2: Surface-modifying the hydrophobically oleophilically modified graphene oxide obtained in step 1 with a low molecular weight polycarbonate as a modifier: dissolving the low molecular weight polycarbonate in tetrahydrofuran to obtain a low molecular weight polycarbonate solution; adding the hydrophobically oleophilically modified graphene oxide to the low molecular weight polycarbonate solution, mixing well, and then ultrasonically reacting for 12-36 hours to obtain surface-modified graphene oxide; the low molecular weight polycarbonate has a number average molecular weight of no more than 4000 and a weight average molecular weight of no more than 6000, and the relative proportion of terminal hydroxyl groups in the molecular chain of the low molecular weight polycarbonate is no less than 60%; Step 3: Using the surface-modified graphene oxide obtained in step 2 as an additive, a high-strength graphene-modified polycarbonate is prepared by a solution blending method: the surface-modified graphene oxide is added to an N, N-dimethylacetamide solvent to prepare a surface-modified graphene oxide suspension, which is then added to an N, N-dimethylacetamide solvent containing polycarbonate after ultrasonic dispersion; a modifier, an antioxidant, and an ultraviolet absorber are then added, wherein the modifier, antioxidant, and ultraviolet absorber are The mass ratio of the agent, surface-modified graphene oxide, and polycarbonate is 0.3-0.6:0.1-0.3:0.1-0.3:1-5:100, and the mixture is stirred and reacted at 35-45°C for 6-12 hours. The mixed solution is dried to obtain a high-strength graphene-modified polycarbonate; the polycarbonate includes polycarbonate A, polycarbonate B, and polycarbonate C, and the mass ratio of polycarbonate A, polycarbonate B, and polycarbonate C is 1-3:6-8:5-7; The polycarbonate A has a melt index of 6.0 cm³ / 10 min, a notched impact strength of 70 kJ / m², and a heat deformation temperature of 140°C; the polycarbonate B has a melt index of 12 cm³ / 10 min, a notched impact strength of 70 kJ / m², and a heat deformation temperature of 135°C; the polycarbonate C has a melt index of 34 cm³ / 10 min, a notched impact strength of 65 kJ / m², and a heat deformation temperature of 136°C.

2. The method for preparing a high-strength graphene-modified polycarbonate according to claim 1, wherein: In step 2, the low molecular weight polycarbonate is prepared by esterification reaction, and the preparation method is as follows: bisphenol A is recrystallized from toluene and vacuum dried at 60°C; diphenyl carbonate is recrystallized from methanol and vacuum dried at room temperature; bisphenol A and recrystallized diphenyl carbonate are added to a reactor in equal amounts, stirred under nitrogen, and heated to 50°C until the monomers are melted, sodium benzoate is added in an amount of 0.1%wt after melting, and then a pre-prepared NaOH solution is added, and the reaction is maintained at 150°C for 0.5 h, and then the temperature is raised to 170°C, 190°C and 230°C for 0.5 h each, and then vacuumed for 15 minutes to remove the by-product phenol, and cooled to obtain a crude product; the crude product is dissolved in tetrahydrofuran, and then precipitated with 3 volumes of anhydrous ethanol to remove unreacted raw materials or residual phenol, and air-dried to obtain a low molecular weight polycarbonate finished product.

3. The method for preparing a high-strength graphene-modified polycarbonate according to claim 2, wherein: In step 2, the concentration of the NaOH solution is 0.057 g / mL, and the vacuum degree of the vacuum pumping is less than 100 Pa.

4. The method for preparing a high-strength graphene-modified polycarbonate according to claim 1, wherein: In step three, the modifier is polytetrafluoroethylene.

5. An application of a high-strength graphene-modified polycarbonate prepared by the method according to any one of claims 1 to 4, characterized in that: The high-strength graphene-modified polycarbonate is used for the outer frame of new energy vehicle sensors.

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