Preparation method and application of high-strength graphene modified polycarbonate

Abstract

The invention discloses a preparation method and application of high-strength graphene modified polycarbonate. The method comprises the following steps: carrying out hydrophobic and oleophylic modification on graphene oxide; carrying out surface modification on the hydrophobic oleophylic modified graphene oxide by taking low-molecular-weight polycarbonate as a modifier; the high-strength graphene modified polycarbonate is prepared by taking the surface modified graphene oxide as an additive through a solution blending method. The invention further provides an application of the high-strength graphene modified polycarbonate, and the high-strength graphene modified polycarbonate is used for automobile parts and particularly used for an outer frame of a new energy automobile sensor. The hydrophobic and oleophylic modified graphene oxide is subjected to surface modification, the mechanical property of the material can be effectively improved, good optical performance, wear resistance and weather resistance can be kept, the material is suitable for being used as an outer frame material of a new energy automobile sensor, and then the quality of a new energy automobile is improved.

Description

Technical Field

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

[0002] Polycarbonate (PC in English), also known as PC plastic, is a high molecular polymer containing carbonate groups in the molecular chain. It can be divided into aliphatic, aromatic, aliphatic-aromatic and other types according to the structure of the ester group. It is a strong thermoplastic resin with a large number of applications in modern industry.

[0003] Graphene is a two-dimensional atomic-scale, hexagonal carbon allotrope. Graphene oxide is the 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 automotive parts.

[0004] There are a large number of sensors in new energy vehicles, which require a safe and stable environment for installation. Polycarbonate has extremely high impact resistance, even higher than some metals, and is not easy to break, so it is often called "transparent metal". It can be as transparent as glass, but much lighter, making it an ideal material for making transparent products. Polycarbonate is easy to form and can produce complex shapes and thin-walled structures, which enables designers to integrate the sensor frame with other components of new energy vehicles and hide the sensor in the body decoration to achieve an integrated design that is both beautiful and space-saving. With the advancement of new energy vehicles from electrification to intelligence, sensors such as laser radar and millimeter-wave radar are widely used in new energy vehicles. The installation of laser radar and millimeter-wave radar on new energy vehicles requires further research on existing polycarbonate materials so that they have 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 resulting materials can be used to obtain sensor frames to protect sensors such as laser radar and millimeter-wave radar of new energy vehicles, so that they can operate continuously and stably in harsh environments and improve the quality of new energy vehicles. Therefore, a method for preparing high-strength graphene-modified polycarbonate is needed. Summary of the invention

[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 present invention is achieved through the following scheme:

[0007] A method for preparing high-strength graphene-modified polycarbonate, the method comprising the following steps, measured by weight:

[0008] Step 1, hydrophobic and 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 container and keep the temperature at 145-150° C. for reaction 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, and freeze-dry to obtain hydrophobic and lipophilic modified graphene oxide;

[0009] Step 2: Using low molecular weight polycarbonate as a modifier to surface modify the hydrophobic and lipophilic modified graphene oxide obtained in step 1: 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 hydrophobic and lipophilic 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;

[0010] Step 3: using the surface-modified graphene oxide obtained in step 2 as an additive, preparing high-strength graphene-modified polycarbonate by a solution blending method: adding the surface-modified graphene oxide to an N,N-dimethylacetamide solvent to prepare a 1 mg / mL surface-modified graphene oxide suspension, and adding it to the N,N-dimethylacetamide solvent containing polycarbonate after ultrasonic dispersion; subsequently adding a modifier, an antioxidant, and an ultraviolet absorber, wherein 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, stirring the reaction at 35-45°C for 6-12 hours, and drying the mixed solution to obtain a high-strength graphene-modified polycarbonate.

[0011] In step one, 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 item 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 its wear resistance is poor. When it is used in the outer frame of new energy vehicle sensors, it is easy to get scratches and wear in the use scenario where wind, sand and rain wipers are frequently used, which will affect the normal use of internal sensors. Although the surface properties can be enhanced by coating or composite modification, this will increase the cost and complexity. The addition of graphene oxide can not only increase the mechanical properties of the material, but also 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 automotive parts. However, the strong van der Waals force between ordinary graphene oxide sheets makes them easy to agglomerate, resulting in aggregation in the composite material, affecting the uniformity of material performance and the overall enhancement effect. In addition, the interfacial interaction between graphene oxide and polycarbonate is weak, which may limit the effective transfer of the excellent properties of graphene oxide to the composite material. The inventors found that hydrophobic and lipophilic modification of graphene oxide can improve its dispersibility in this system. The reason is speculated to be that the relative content of oxygen elements on its surface increases significantly after modification, which can form various oxygen-containing groups, further improving the hydrophobicity and lipophilicity of graphene oxide, so that it can be better used in hydrophobic and lipophilic environments.

[0015] The hydrophobic and oleophilic modified graphene oxide can improve its dispersion performance in polycarbonate to a certain extent. Polycarbonate is a non-polar polymer, while the surface of graphene oxide is rich in polar functional groups, which leads to poor compatibility between the two. Poor interfacial compatibility will limit the uniform dispersion of graphene oxide nanosheets in the polycarbonate matrix, affecting the overall performance of the composite material, which may lead to insignificant improvement in mechanical properties or uneven dispersion leading to local stress concentration. To solve this problem, the present invention uses low molecular weight polycarbonate as a modifier to perform surface modification on graphene oxide, in order to form a polymer attachment layer on the surface of graphene oxide. Commercially available polycarbonate matrix materials generally have high molecular weight and poor dispersibility, while the low molecular weight polycarbonate prepared by the present invention has higher interfacial interaction force with graphene oxide. It is speculated that the low molecular weight polycarbonate has a lower relative molecular weight, which increases the relative proportion of hydroxyl groups at the end of the molecular chain. On the one hand, the low molecular weight polycarbonate has a certain reaction activity, and has a certain probability of chemical bonding or hydrogen bonding with oxygen-containing functional groups on the surface of hydrophobic and lipophilic modified graphene oxide; on the other hand, since its molecular main chain itself is bisphenol A type polycarbonate, it has good compatibility with the polycarbonate matrix and has the potential to improve the interface performance of the polycarbonate material.

[0016] In step 3, the polycarbonate comprises 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;

[0017] The applicant has found that when the polycarbonate is compounded in the above ratio in the present 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] The polycarbonate A, polycarbonate B and polycarbonate C are all products of Covestro of Germany purchased from Shanghai Xingyun International Trade Co., Ltd. Among them, the polycarbonate A is the 1804 model polycarbonate of the Makro l on brand. The polycarbonate B is the AX2677 model polycarbonate of the Makro l on brand. The polycarbonate C is the LED2247 model polycarbonate of the Makro l on brand.

[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: 34 cm 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 the 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: based on mass parts, 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 into a reactor in the same amount of substances, stirred with 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 0.5h, and then the temperature is raised to 170°C, 190°C and 230°C for 0.5h each, and then vacuumed for 15min to remove the by-product phenol, and a crude product is obtained after cooling; the crude product is dissolved in tetrahydrofuran, and then precipitated with 3 times the volume of anhydrous ethanol to remove unreacted raw materials or residual phenol, and air-dried to obtain a low molecular weight polycarbonate finished product.

[0025] The present invention adds surface-modified graphene oxide as an additive to significantly improve the mechanical properties of the material. Although the surface-modified graphene oxide only accounts for 1-5% compared with 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] In order to solve this problem, the general idea of ​​the prior art is to change the transparency of the material by adding nucleating agents and optical transparent agents, but there are disadvantages such as poor thermal stability, high cost, and compatibility limitations. During high-temperature processing or long-term use, the nucleating agent may affect the long-term performance and stability of the product due to thermal degradation. When used on a large scale, the cost-effectiveness ratio needs to be carefully considered. In addition, the sorbitol derivative nucleating agent cannot be completely compatible in the polycarbonate system of the present invention, but will affect the optical and mechanical properties of the final product.

[0027] The present invention has found in the study that after the reaction process is completed, sodium benzoate as an esterification catalyst has a better removal effect on the byproduct phenol in the subsequent separation and purification process. Due to the physicochemical properties of sodium benzoate, sodium benzoate cannot be separated efficiently and at low cost, but it is also unexpectedly found that the sodium benzoate retained in the polycarbonate finished 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 generation, and can promote the reaction of bisphenol A and diphenyl carbonate and other monomers to form polycarbonate polymer chains. After the reaction is completed, these sodium benzoates will naturally be distributed in the polycarbonate finished product, and will be basically evenly distributed. During the reaction process, it is easier to start nucleation of the polycarbonate polymer chain when the molten state is transformed into the crystalline state, which makes the crystallization process change from homogeneous nucleation to heterogeneous nucleation, which may occur on the surface of sodium benzoate. Heterogeneous nucleation usually requires a lower energy barrier than homogeneous nucleation, so the crystallization process is accelerated, the number of crystal nuclei is significantly increased, and the size of each crystal grain is reduced. Smaller grains have a weaker ability to scatter light, which can improve the transparency of polycarbonate products; small and uniform grain distribution can reduce stress concentration inside the material, and small grains can absorb more energy without breaking, so grain refinement can also improve the impact strength and toughness of the material. This overcomes the transparency and performance defects caused by the low molecular weight polycarbonate's own structure, and using it as a modified target for graphene oxide will not affect the optical and mechanical properties of the final product. In addition, the overall stability of the material and its ability to resist environmental stress cracking can also be improved by improving the crystal structure. All of this does not require the addition of any extra auxiliary agents or preparation methods, and can greatly improve efficiency in terms of technology to ensure production costs.

[0028] In the present invention, bisphenol A was purchased from Jinan Century Tongda Chemical Co., Ltd., and its parameters were: 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 extraction is less than 100 Pa.

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

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

[0032] The present invention also provides an application of high-strength graphene-modified polycarbonate, wherein the high-strength graphene-modified polycarbonate is used for automobile parts, specifically for the outer frame of a new energy automobile sensor.

[0033] The beneficial effects of the present invention are:

[0034] The invention discloses a method for preparing high-strength graphene-modified polycarbonate, which adopts low-molecular-weight polycarbonate as a modifier to perform surface modification on hydrophobic and oleophilic modified graphene oxide, thereby effectively improving the compatibility problem between graphene oxide and polycarbonate, achieving uniform distribution of graphene oxide in a polycarbonate matrix and obtaining a good reinforcement 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 and wear resistance and weather resistance, so that the material is suitable as an outer frame material for new energy vehicle sensors, thereby improving the quality of new energy vehicles. DETAILED DESCRIPTION

[0035] The present invention will be further described below in conjunction with specific embodiments and comparative examples:

[0036] Example 1

[0037] A method for preparing high-strength graphene-modified polycarbonate, the method comprising the following steps, measured by weight:

[0038] Step 1, hydrophobic and lipophilic modification of graphene oxide: 4 parts of dried graphene oxide are ultrasonically dispersed in 1000 parts of xylene; 2 parts of octadecylamine are added, ultrasonically treated for 3 hours, transferred into a reaction vessel and kept at 147°C for 24 hours, and stirred continuously during the reaction; after the reaction is completed, the reaction solution is cooled, centrifuged, washed with ethanol, and finally ultrasonically dispersed in water, and freeze-dried to obtain hydrophobic and lipophilic modified graphene oxide;

[0039] Step 2: Surface modification of the hydrophobic and lipophilic modified graphene oxide obtained in step 1 is performed 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 lipophilic modified graphene oxide is added to the low molecular weight polycarbonate solution, mixed evenly, and subjected to ultrasonic reaction 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 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 0.6:0.2:0.1:5:100, and 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: 34 cm 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 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 the molecular chain terminal hydroxyl groups of the low molecular weight polycarbonate is not less than 60%.

[0050] The preparation method of the low molecular weight polycarbonate is as follows: based on mass parts, 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 into a reactor in the same amount, stirred with 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 to make the pH value of the reaction system 9, and the reaction is maintained at 150°C for 0.5h, and then the temperature is raised to 170°C, 190°C and 230°C for 0.5h each, and then vacuumed for 15min to remove the by-product phenol, and a crude product is obtained after cooling; the crude product is dissolved in tetrahydrofuran, and then precipitated with 3 times the volume of anhydrous ethanol to remove unreacted raw materials or residual phenol, and air-dried to obtain a low molecular weight polycarbonate finished product.

[0051] In step 2, the concentration of the NaOH solution is 0.057 g / mL, and the vacuum degree of the vacuum extraction 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 present invention also provides an application of high-strength graphene-modified polycarbonate, wherein the high-strength graphene-modified polycarbonate is used for automobile parts, specifically for the outer frame of a new energy automobile sensor.

[0054] Example 2

[0055] A method for preparing high-strength graphene-modified polycarbonate, the specific implementation manner is the same as that of Example 1, except that, in parts by mass, the method comprises the following steps:

[0056] Step 1, hydrophobic and lipophilic modification of graphene oxide: 2 parts of dried graphene oxide are ultrasonically dispersed in 1200 parts of xylene; 3 parts of octadecylamine are added, ultrasonically treated for 1 hour, transferred into a reaction vessel and kept at 150°C for reaction for 36 hours, and stirred continuously during the reaction; after the reaction is completed, the reaction solution is cooled, centrifuged, washed with ethanol, and finally ultrasonically dispersed in water, and freeze-dried to obtain hydrophobic and lipophilic modified graphene oxide;

[0057] Step 2: Surface modification of the hydrophobic and lipophilic modified graphene oxide obtained in step 1 is performed 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 4 g / 100 mL; then 2 g / 100 mL of the hydrophobic and lipophilic modified graphene oxide is added to the low molecular weight polycarbonate solution, mixed evenly, and subjected to ultrasonic reaction 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 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 0.3:0.3:0.2:1:100, and 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 manner is the same as that of Example 1, except that, in parts by mass, the method comprises the following steps:

[0063] Step 1, hydrophobic and 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, ultrasonically treated for 2 hours, transferred into a reaction vessel and kept at 145°C for 72 hours, and stirred continuously during the reaction; after the reaction is completed, the reaction solution is cooled, centrifuged, washed with ethanol, and finally ultrasonically dispersed in water, and freeze-dried to obtain hydrophobic and lipophilic modified graphene oxide;

[0064] Step 2: Surface modification of the hydrophobic and lipophilic modified graphene oxide obtained in step 1 is performed 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 5 g / 100 mL; then 1 g / 100 mL of the hydrophobic and lipophilic modified graphene oxide is added to the low molecular weight polycarbonate solution, mixed evenly, and subjected to ultrasonic reaction 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 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 0.5:0.1:0.3:3:100, and 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 same points as those in 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, and 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 lamella diameter of 0.5-5 μm; the graphene oxide B has a thickness of 1 nm and a lamella diameter of 0.2-10 μm.

[0071] Comparative Example 2

[0072] The same points as those in 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. It was purchased from Xianfeng Nano.

[0074] Comparative Example 3

[0075] The same points as those in 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 same points as those in 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: based on mass parts, 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 into a reactor in the same amount, stirred with nitrogen and heated to 50°C until the monomers melt, then a pre-prepared NaOH solution is added and kept at 150°C for reaction for 0.5h, then the temperature is raised 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, unreacted raw materials or residual phenol are removed, and air drying is performed to obtain a low molecular weight polycarbonate finished product.

[0080] Comparative Example 5

[0081] The same points as those in 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 same points as those in 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 mixed material of the above samples was extruded by a twin-screw extruder at 270°C; the extrudate was injected into a flat vulcanizer and hot-pressed for 5 minutes to obtain composite material specimens of the above samples, and the following tests were performed on these composite material specimens: the tensile strength was tested according to GB / T 1040.1-2018, the flexural strength was tested according to GB / T 9341-2008, and the impact strength was tested according to GB / T1843-2008.

[0088] It can be seen from Table 1 that after the addition of surface-modified graphene oxide, the tensile strength, bending strength and impact strength of the sample are 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 Bending strength(MPa) Tensile strength(MPa) <![CDATA[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] 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. Visible light transmittance is an important parameter for characterizing the transparency of materials. In the present invention, visible light transmittance is used to characterize the transparency. The visible light transmittance of the sample is completed using the CARY 500 UV-visible absorption spectrometer of VARIAN Company of the United States. The pencil hardness test is performed on the surface of the sample: in accordance with the GB / T6739-1996 standard, the hardness can indirectly reflect the ability of the material to resist scratches. The higher the hardness grade, the better the wear resistance.

[0093] Table 2 Abrasion resistance and transparency test results

[0094]

[0095] It can be seen from Table 2 that 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 according 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, and the mechanical properties test is carried out after 50 cycles. The mechanical properties after 50 cycles of light erosion are shown in Table 3, and the mechanical properties 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 in Comparative Examples 1-6 have decreased significantly, among which the impact strength has decreased the most, and some even exceed 50%. Although the mechanical properties of Examples 1-3 of the present invention have also decreased, the magnitude is not very large.

[0098] Table 3 Weathering 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 required by the present invention.

Claims

1. A method for preparing high-strength graphene-modified polycarbonate, It is characterized in that In parts by mass, the method comprises the following steps: Step 1, hydrophobic and 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 container and keep the temperature at 145-150° C. for reaction 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, and freeze-dry to obtain hydrophobic and lipophilic modified graphene oxide; Step 2: Using low molecular weight polycarbonate as a modifier to surface modify the hydrophobic and lipophilic modified graphene oxide obtained in step 1: dissolving low molecular weight polycarbonate in tetrahydrofuran to obtain a low molecular weight polycarbonate solution; adding the hydrophobic and lipophilic modified graphene oxide to the low molecular weight polycarbonate solution, mixing well, and then subjecting to ultrasonic reaction for 12-36 hours to obtain surface-modified graphene oxide; Step 3: using the surface-modified graphene oxide obtained in step 2 as an additive, preparing high-strength graphene-modified polycarbonate by a solution blending method: adding the surface-modified graphene oxide to an N,N-dimethylacetamide solvent to prepare a surface-modified graphene oxide suspension, and adding it to the N,N-dimethylacetamide solvent containing polycarbonate after ultrasonic dispersion; then adding a modifier, an antioxidant, and an ultraviolet absorber, wherein 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, stirring the reaction at 35-45°C for 6-12 hours, and drying the mixed solution to obtain a high-strength graphene-modified polycarbonate.

2. A method for preparing a high-strength graphene-modified polycarbonate according to claim 1, Features: In step one, 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.

3. A method for preparing a high-strength graphene-modified polycarbonate according to claim 2, Features: 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.

4. A method for preparing a high-strength graphene-modified polycarbonate according to claim 1, Features: 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 1-3:6-8:5-7.

5. A method for preparing a high-strength graphene-modified polycarbonate according to claim 4, Features: The melt index of the polycarbonate A is 6.0 cm 3 / 10min; notched impact strength: 70kJ / m 2 ; Heat deformation temperature is 140℃; The melt index of the polycarbonate B is 12 cm 3 / 10min; notched impact strength: 70kJ / m 2 : Heat deformation temperature is 135℃; The melt index of the polycarbonate C is 34 cm 3 / 10min; notched impact strength: 65kJ / m 2 ; Heat deformation temperature is 136℃.

6. A method for preparing a high-strength graphene-modified polycarbonate according to claim 1, Features: In step 2, the low molecular weight polycarbonate is prepared by esterification reaction, and the preparation method is as follows: in parts by mass, 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 the same amount of substances, stirred with 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 0.5h, and then the temperature is raised to 170°C, 190°C and 230°C for 0.5h each, and then vacuumed for 15min to remove the by-product phenol, and a crude product is obtained after cooling; the crude product is dissolved in tetrahydrofuran, and then precipitated with 3 times the volume of anhydrous ethanol to remove unreacted raw materials or residual phenol, and air-dried to obtain a low molecular weight polycarbonate finished product.

7. A method for preparing a high-strength graphene-modified polycarbonate according to claim 4, Features: 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 the molecular chain terminal hydroxyl groups of the low molecular weight polycarbonate is not less than 60%.

8. A method for preparing a high-strength graphene-modified polycarbonate according to claim 4, Features: 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.

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

10. Use of high-strength graphene-modified polycarbonate prepared by the method of any one of claims 1 to 7, Features: The high-strength graphene-modified polycarbonate is used for the outer frame of a new energy vehicle sensor.

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