A method of carbon fiber defect growth zif-8 for enhancing fiber mechanical properties

Abstract

The present application relates to a kind of carbon fiber defect in situ growth 2-methylimidazole zinc MOF (ZIF-8), after high-temperature carbonization treatment is used for the method for enhancing the mechanical properties of fiber, belong to carbon fiber structural modification technical field.The existence of carbon fiber surface defect makes its actual mechanical properties far less than theoretical mechanical properties, by using nanomaterial to repair carbon fiber surface defect is a kind of feasible control means.ZIF-8 is a kind of zinc-based metal organic framework structure, preparation process is simple, green and environmental protection, and has good application prospect to carbon fiber surface defect repair.The present application is combined with carbon fiber defect by ZIF-8 under ultrasonic environment, and after a certain carbonization procedure treatment, Zn in ZIF-8 and organic structure pyrolysis form zinc oxide and inorganic carbon fill in carbon fiber surface defect, for carbon fiber to transmit stress when stretching, reaches the purpose of enhancing the mechanical properties of carbon fiber.

Description

TECHNICAL FIELD

[0001] The application relates to a method for in-situ growth of ZIF-8 on carbon fiber defects for reinforcing the mechanical properties of the carbon fiber, and belongs to the technical field of carbon fiber structure modification. BACKGROUND

[0002] The carbon fiber has the characteristics of high temperature resistance, friction resistance, electricity conduction, heat conduction and corrosion resistance, so that the carbon fiber has good application prospects in many fields.

[0003] The actual application strength of the carbon fiber can only reach about 10% of the theoretical strength, and the main influencing factor is various defects generated in the preparation process. The main defect form affecting the mechanical properties of the carbon fiber is surface defects, which accounts for 90% of the defects of the carbon fiber composite material, and is mainly generated in the production process. To improve the actual use strength of the carbon fiber, the most direct and effective method is to reduce the surface defects.

[0004] Based on the above analysis, the application relates to in-situ growth of nano-ZIF-8 on the surface defect position of the carbon fiber, high-temperature carbonization treatment of the carbon fiber, and improvement of the mechanical properties of the carbon fiber. The application is simple in operation, and the ZIF-8 can be filled in the defect position of the carbon fiber through ultrasonic auxiliary treatment. After heat treatment, the oxide of zinc and inorganic carbon are filled in the defect position of the carbon fiber, which has important significance for reinforcing the structure of the carbon fiber. SUMMARY

[0005] In view of the problems in the above background art, the purpose of the application is to provide a method for in-situ growth of ZIF-8 on carbon fiber defects for reinforcing the mechanical properties of the carbon fiber.

[0006] In order to achieve the above purpose, the application provides a method for introducing the oxide of zinc and inorganic carbon structure on the surface of the carbon fiber through the cooperation of chemical and heating, and the method is characterized in that the method comprises the following steps:

[0007] Step one, carbon fiber degumming treatment: the carbon fiber is placed in a heated acetone solution, and is treated by 70 DEG C condensation reflux for 48 hours.

[0008] Step two, preparation of ZIF-8 precursor solution: 1.487g of zinc nitrate hexahydrate and 3.284g of 2-methyl imidazole are respectively mixed with methanol in a molar ratio of 1:50, and the mixture is continuously stirred for a period of time.

[0009] Step three, preparation of CF@ZIF-8: the degummed carbon fiber in step one is added to the zinc nitrate methanol solution in step two, and then 2-methyl imidazole methanol solution is added, and ultrasonic treatment is performed for 60 minutes.

[0010] Step four, obtaining dried CF@ZIF-8 composite material: after the CF@ZIF-8 prepared in step three is filtered from the solution, it is washed with distilled water and then placed in a vacuum oven for drying at 60 degrees Celsius for 8 hours.

[0011] Step five, obtaining CF@ZIF-8 (H-CF@ZIF-8) after carbonization: after the dried CF@ZIF-8 in step four is placed in a tube furnace and heated to 450-600 degrees Celsius at a rate of 3 degrees Celsius per minute according to the carbonization procedure and kept at the temperature for 1 hour, the carbon fiber with improved mechanical properties is obtained.

[0012] The present application has the following outstanding technical advantages:

[0013] The active functional groups exist at the defect sites on the surface of the carbon fiber, can be effectively combined with ZIF-8, and enhance the interaction between the two, so that the ZIF-8 can be targeted to grow at the defect sites of the carbon fiber; the small particle size ZIF-8 nanoparticles grow at the defect sites of the carbon fiber first, and form zinc metal oxide and inorganic carbon structure after carbonization, providing stress dispersion effect for the stretching of the carbon fiber, and effectively reinforcing the defect sites of the carbon fiber. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 Preparation process schematic diagram of ZIF-8 loaded carbon fiber.

[0015] Figure 2 SEM image of CF after degumming.

[0016] Figure 3 SEM image of CF@ZIF-8 after sonochemical treatment.

[0017] Figure 4 SEM image of H-CF@ZIF-8 obtained after carbonization treatment.

[0018] Figures 5-6 XPS image of CF, CF@ZIF-8 and H-CF@ZIF-8.

[0019] Figure 7 Bar chart of breaking strength of CF and CF@ZIF-8 at different carbonization temperatures. DETAILED DESCRIPTION

[0020] The present application will be further described in detail below in conjunction with specific examples, which should be understood as only for explaining and introducing the present application, and cannot limit the application range of the present application. Any modification and change made to the present application within the purpose and range of the present application falls into the protection range of the present application.

[0021] The main evaluation of the reinforcement of the mechanical properties of the carbon fiber is the determination of the breaking tensile strength of the carbon fiber.

[0022] The breaking strength (si) of the carbon fiber defines the ratio of the tensile force to the breaking cross-sectional area when the material breaks. The calculation formula is:

[0023] Examples 1-4:

[0024] The preparation method of the polyamide composite nanofiltration membrane with high permeation selectivity in this embodiment is carried out by the following steps:

[0025] Step one, the carbon fiber in the present application needs to be degummed first: immerse a certain amount of carbon fiber in acetone solution, 60℃ acetone condensation reflux treatment for 48 hours.

[0026] Step two, prepare ZIF-8 precursor solution, the specific steps are as follows: 1.487g zinc nitrate is stirred and dissolved in 50ml of methanol solution, and 3.284g 2-methyl imidazole is stirred and dissolved in 50ml of methanol solution.

[0027] Step three, take 20g of carbon fiber obtained in step one and place it in the zinc nitrate methanol solution, then add the 2-methyl imidazole methanol solution inward, and perform acoustic chemical treatment for 60 minutes to obtain CF@ZIF-8.

[0028] Step four, the CF@ZIF-8 prepared in step three is washed with distilled water for 3 times and placed in a vacuum oven for drying at 60℃ for 8 hours.

[0029] Step five, carbonize the CF@ZIF-8 dried in step four in an Ar atmosphere, and heat it to 450℃, 500℃, 550℃ and 600℃ at a heating rate of 3℃ / min respectively and keep it for 1 hour to obtain H-CF@ZIF-8.

[0030] Take an appropriate amount of H-CF@ZIF-8 obtained in step five, use a single fiber tensile standard card to prepare a sample, and then perform a tensile test under normal temperature and pressure conditions.

[0031] Figure 1 The preparation process of ZIF-8 loaded carbon fiber is shown in the schematic diagram. Under the condition of acoustic chemistry, nano ZIF-8 can be effectively grown in situ at the defect position of carbon fiber. After carbonization, zinc metal oxide and inorganic carbon are formed and combined with the surface of carbon fiber, which can transfer stress when the carbon fiber is stretched and broken.

[0032] Figures 2-4The images show SEM images of the carbon fiber surface morphology after degumming, the carbon fiber surface morphology after ZIF-8 growth, and the H-CF@ZIF-8 surface morphology obtained after carbonization. First, it can be seen that the carbon fiber precursor used in this study has many surface defects, forming longitudinal grooves. Under a sonochemical environment, ZIF-8 nanoparticles were successfully grown onto the carbon fiber surface through a solvothermal reaction. Finally, after the carbonization process, Zn groups were released.

[0033] Figures 5-6 XPS images of CF, CF@ZIF-8, and H-CF@ZIF-8 are shown. Analysis indicates that the C and N peaks match those in the literature, and the presence of Zn and N peaks proves that ZIF-8 was successfully grown onto the carbon fibers. After heat treatment, Zn-O bonds appeared, proving the presence of ZnO.

[0034] The tensile strength of the main carbon fibers in these examples is shown in the table.

[0035]

[0036] Figure 7 A bar chart showing the mechanical fracture strength of carbon fiber precursor and ZIF-8 carbon fiber loaded at different temperatures. Figure 7 As can be seen from the table above, the mechanical properties of carbon fiber decrease slightly with increasing temperature under heat treatment conditions. After introducing ZIF-8 onto the surface of carbon fiber, the fracture strength of carbon fiber is improved at different carbonization temperatures, with the maximum fracture strength obtained at 500℃. This is due to the ZnO nanoparticles formed by ZIF-8 after heat treatment and the inorganic carbon filling the defect sites of carbon fiber, forming a uniform filling layer that can transfer stress when carbon fiber is stretched, thereby increasing the mechanical properties of carbon fiber.

[0037] Example 2 is the preferred embodiment of this application (500℃), with a breaking strength reaching 4293 MPa, an improvement of 13.8% compared to the sample. Examples 1, 3, and 4 also exhibited similar performance characteristics after the above performance tests, but the fiber mechanical properties decreased with increasing temperature, as shown in the table above. In summary, the method of using the carbon fiber defect growth ZIF-8 described in this application to enhance the mechanical properties of carbon fibers can provide a large number of Zn groups and inorganic carbon using the relatively common ZIF-8 material, which has a good chemical reaction with carbon fibers after carbonization. This method introduces a way to introduce metal groups on the surface of carbon fibers, providing a new approach for reinforcing carbon fibers with metal groups.

Claims

1.A method for enhancing the mechanical properties of carbon fibers by growing ZIF-8 on defects of the carbon fibers, the method comprising the following steps: (1) degumming treatment of the carbon fibers: placing the carbon fibers in a heated acetone solution and condensing and refluxing for a period of time; (2) preparation of a ZIF-8 precursor solution: stirring and mixing zinc nitrate hexahydrate and 2-methylimidazole with methanol in a certain proportion, and continuously stirring to disperse uniformly; (3) in-situ growth of ZIF-8 on defects of the carbon fibers, denoted as CF@ZIF-8: adding the degummed carbon fibers of step (1) to the zinc nitrate methanol solution of step (2), then adding 2-methylimidazole methanol solution, and placing in an ultrasonic environment for reaction; (4) drying of the CF@ZIF-8: filtering the CF@ZIF-8 composite material prepared in step (3) from the solution, washing with distilled water, and then drying in a vacuum oven; (5) heat treatment of the carbon fibers on which ZIF-8 is grown, denoted as H-CF@ZIF-8: placing the dried CF@ZIF-8 of (4) in a tube furnace according to the carbonization program, heating to 450-600℃ and holding for a period of time, and obtaining carbon fibers with enhanced mechanical properties. In the step (3), the ultrasonic treatment time is 60 minutes. In the step (5), the carbonization heating rate is 3℃ / min, and the holding time is 2 hours. ​ ​ ​ 2. The method of claim 1, wherein the carbon fiber defect growth ZIF-8 is used to enhance the mechanical properties of the fiber. ​ 3. The method of claim 1, wherein the carbon fiber defect growth ZIF-8 is used to enhance the mechanical properties of the fiber. ​

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