An interface-modified carbon fiber material and a preparation method and application thereof

Abstract

The present application relates to an interface modified carbon fiber material and its preparation method and application, which solves the technical problems of large surface inertness, small roughness, poor resin infiltration effect on the fiber, and difficult detection of interface damage of the existing carbon fiber, which comprises 2-(N-carbazolyl) methyl methacrylate-glycidyl methacrylate binary copolymer and aminated carbon nanotubes, and the binary copolymer and the aminated carbon nanotubes are uniformly mixed and dispersed. The present application can be applied to the field of carbon fiber reinforced composite material preparation.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of carbon fiber materials and its preparation method and application, specifically, it is related to a kind of interface modified carbon fiber material and its preparation method and application. BACKGROUND

[0002] Carbon fiber reinforced polymer matrix composite is widely used in automobile manufacturing, aerospace, wind power generation and other fields due to its high specific strength, specific modulus, excellent electrical conductivity, thermal conductivity and other properties. However, due to the high degree of graphitization of the surface of carbon fiber, the chemical inertness is large, and the roughness is small, which makes the adhesion between carbon fiber and resin matrix low, and the interface performance is poor. In addition, the internal damage monitoring of carbon fiber reinforced polymer matrix composite is also a problem to be solved.

[0003] At present, there are many methods for interface modification of carbon fiber composite materials, such as thermal oxidation, acid oxidation, chemical oxidation, electrochemical oxidation, plasma treatment, chemical grafting, nanoparticle deposition, sizing and other methods. Among them, the sizing method is simple to operate, the equipment is simple, and at the same time, the surface structure of the fiber is not damaged, and the excellent performance of the carbon fiber is retained. The introduction of carbon nanotubes and other nanoparticles on the surface of the fiber can increase the roughness of the fiber surface and improve the mechanical interlocking between the fiber surface and the resin matrix. However, due to the strong van der Waals force between carbon nanotubes, carbon nanotubes are prone to agglomeration on the surface of the fiber, which forms defects at the interface of the composite material, causing stress concentration, thereby affecting the interface performance.

[0004] Chinese patent application with publication number CN102817241A discloses a kind of carbon nanotube-containing thermoplastic sizing agent and its preparation method and application, but an external electric field is needed during the sizing process, the process is complicated, and at the same time, the addition of thermoplastic resin will limit the dispersion effect of carbon nanotubes, which is easy to cause the agglomeration of carbon nanotubes, hindering the improvement of fiber interface performance. SUMMARY

[0005] The present application is to solve the technical problems of the prior art, such as large inertness of carbon fiber surface, small roughness, poor resin infiltration effect on fiber, and difficult detection of interface damage, and provides an interface modified carbon fiber material and its preparation method and application.

[0006] Therefore, the present application provides an interface modified carbon fiber material, which comprises carbon fiber and a coating layer; the coating layer is coated on the surface of the fiber and has a fluorescent effect; the coating layer comprises 2-(N-carbazolyl) methyl acrylate-glycidyl methacrylate copolymer and aminated carbon nanotubes; the mass ratio of the aminated carbon nanotubes to the 2-(N-carbazolyl) methyl acrylate-glycidyl methacrylate copolymer is (0.2-4):1.

[0007] The application also provides a preparation method of the interface modified carbon fiber material, which comprises the following steps: (1) preparing 2-(N-carbazolyl) ethyl methacrylate, glycidyl methacrylate, 2-2 ， - a tetrahydrofuran mixed solution of azobisisobutyronitrile; heating the reaction under a nitrogen atmosphere; after the reaction is completed, the reaction product is precipitated with petroleum ether, filtered, washed with ethanol and dried to obtain 2-(N-carbazolyl) ethyl methacrylate-glycidyl methacrylate copolymer; (2) mixing the copolymer obtained in step (1) and carbon nanotubes to prepare a N,N-dimethylformamide mixed dispersion liquid and performing ultrasonic treatment; (3) immersing the unsized carbon fiber in the dispersion liquid obtained in step (2); and (4) taking out the carbon fiber and sequentially washing it with water and ethanol and drying.

[0008] Preferably, in step (1), the mass ratio of 2-(N-carbazolyl) ethyl methacrylate to glycidyl methacrylate is (0.5-2):1; 2-2 ， - the mass of azobisisobutyronitrile accounts for 0.7%-2% of the total mass of the reactants; and the petroleum ether used is added in sufficient amount until no more precipitation occurs. The monomer ratio is beneficial to the reaction and the synthesis of the required structure polymer. The copolymer with the appropriate monomer ratio can effectively modify the carbon fiber. Too high content of the initiator will affect the molecular weight of the product, and too low content will not be able to initiate the reaction.

[0009] Preferably, in step (1), the concentration of 2-(N-carbazolyl) ethyl methacrylate and glycidyl methacrylate is 0.05 mmol / ml-0.10 mmol / ml. This concentration range can have a suitable reaction speed. Too high concentration will cause a violent reaction which is difficult to control, and too low concentration will affect the normal progress of the reaction.

[0010] Preferably, in step (1), the reaction temperature is 65°C-75°C and the reaction time is 20h-30h. This is the initiation temperature of the initiator. Too low temperature cannot initiate the reaction, and too high temperature will make the reaction too violent and the solution reflux too fast. The reaction time is related to the reaction speed. The faster the reaction speed, the shorter the required reaction time.

[0011] Preferably, in step (2), the mass ratio of the aminated carbon nanotube to the 2-(N-carbazolyl) ethyl methacrylate-glycidyl methacrylate copolymer is (0.2-4):1, and the concentration of the carbon nanotube is 1-3 mg / ml; and the ultrasonic treatment time is 10-40 min. The ratio of the carbon nanotube to the copolymer and the concentration of the carbon nanotube will affect the structure of the coating layer formed on the surface of the carbon fiber, thereby affecting the modification effect. The ultrasonic treatment time will affect the dispersion state of the carbon nanotube, thereby affecting the modification effect.

[0012] Preferably, in step (3), the carbon fiber soaking time is 20–90 min. The soaking time affects the content of the mixed coating on the carbon fiber surface; too low or too high a content is not conducive to the modification effect of the carbon fiber.

[0013] Preferably, in step (4), the water used is deionized water or tap water.

[0014] The present invention also provides an application of interface-modified carbon fiber material in automotive and aerospace reinforced composite materials.

[0015] The present invention has the following beneficial effects:

[0016] This invention constructs an embedded multi-layered reinforcing structure on the surface of carbon fibers by coating the carbon fiber surface with carbazole-based binary copolymers and aminated carbon nanotubes, using different preparation processes. This improves the interfacial properties of carbon fibers and endows the carbon fiber reinforced composite material with a self-reporting function for internal damage. Attached Figure Description

[0017] Figure 1 and Figure 2 These are the CF-PD2-CNT images prepared in Example 1 of this invention; wherein Figure 1 The magnification is 2000 times; Figure 2 The magnification is 5000 times. Detailed Implementation

[0018] The invention will now be further described with reference to implementation examples.

[0019] Example 1

[0020] (1) Measure 20 mL of tetrahydrofuran and add it to a flask. Add 1 mmol of ethyl 2-(N-carbazolyl)methacrylate and 2 mmol of glycidyl methacrylate. Stir for 30 min, then add 0.0028 g of 2-2 ， Azobisisobutyronitrile (AIBN) was added, with nitrogen continuously purging. After reflux at 75°C, the nitrogen was turned off, and the reaction continued for 20 hours. After the reaction was complete, the flask contained a pale yellow, slightly viscous liquid. The liquid was poured into 250 mL of petroleum ether, resulting in a large amount of milky white solid. The mixture was filtered three times, washed with alcohol, and dried in a vacuum oven to obtain a milky white solid, yielding a 2-(N-carbazolyl)ethyl methacrylate-glycidyl methacrylate copolymer.

[0021] (2) Dissolve the binary copolymer obtained in step (1) in N,N-dimethylformamide at a concentration of 10 mg / ml and stir for 10 min;

[0022] (3) Prepare a dispersion of 2 mg / ml aminated carbon nanotubes in N,N- dimethylformamide, sonicate in a water bath for 10 min;

[0023] (4) Mix the solutions obtained in steps (2), (3) 1:1 (volume ratio), sonicate for 20 min;

[0024] (5) Soak the un-sized carbon fibers in the mixture obtained in step (4) for 20 min;

[0025] (6) Take the fibers out of the mixture, wash them with ethanol and water in turn, and dry them.

[0026] Example 2

[0027] (1) Measure 20 mL of tetrahydrofuran into a flask, add 2 mmol of 2-(N- carbazolyl)methyl acrylate and 1 mmol of glycidyl methacrylate to it, stir for 30 min, then add 0.0140 g of 2-2 ， - azobisisobutyronitrile, continue to introduce nitrogen during the feeding process, heat to 65°C to cause reflux, then turn off the nitrogen, continue to react for 30 h. After the reaction is completed, the flask contains a light yellow, slightly viscous liquid. Pour the liquid in the flask into 350 mL of petroleum ether, a large amount of white solid appears, perform three times of suction filtration, and wash with alcohol, then put into a vacuum oven to dry, obtain a white solid, and obtain 2-(N-carbazolyl)methyl acrylate-glycidyl methacrylate copolymer;

[0028] (2) Dissolve the copolymer obtained in step (1) in N,N-dimethylformamide to a concentration of 1.5 mg / ml, stir for 10 min;

[0029] (3) Prepare a dispersion of 6 mg / ml aminated carbon nanotubes in N,N- dimethylformamide, sonicate in a water bath for 10 min;

[0030] (4) Mix the solutions obtained in steps (2), (3) 1:1 (volume ratio), sonicate for 40 min;

[0031] (5) Soak the un-sized carbon fibers in the mixture obtained in step (4) for 90 min;

[0032] (6) Take the fibers out of the mixture, wash them with ethanol and water in turn, and dry them.

[0033] Example 3

[0034] (1) Measure 20 mL of tetrahydrofuran into a flask, add 1.8 mmol of 2-(N- carbazolyl)methyl ethyl methacrylate, 1.8 mmol of glycidyl methacrylate, stir for 30 min, then add 0.0120 g of 2,2'-azobis(2-methylpropionitrile) and continue stirring for 30 min. During the addition of the initiator, nitrogen is continuously introduced. After the temperature is raised to 70°C and refluxing occurs, the nitrogen is turned off, and the reaction is continued for 24 h. After the reaction is completed, the flask contains a light yellow, slightly viscous liquid. The liquid in the flask is poured into 300 mL of petroleum ether, and a large amount of milky white solid appears. The solid is filtered three times, washed with alcohol, and dried in a vacuum oven to obtain a milky white solid, which is 2-(N-carbazolyl)methyl ethyl methacrylate-glycidyl methacrylate copolymer; ， - azobisdimethylvaleronitrile, nitrogen is continuously introduced during the addition, the temperature is raised to 70°C and refluxing occurs, then the nitrogen is turned off, and the reaction is continued for 24 h. After the reaction is completed, the flask contains a light yellow, slightly viscous liquid. The liquid in the flask is poured into 300 mL of petroleum ether, and a large amount of milky white solid appears. The solid is filtered three times, washed with alcohol, and dried in a vacuum oven to obtain a milky white solid, which is 2-(N-carbazolyl)methyl ethyl methacrylate-glycidyl methacrylate copolymer;

[0035] (2) The copolymer obtained in step (1) is dissolved in N,N-dimethylformamide to a concentration of 1 mg / ml, and stirred for 10 min;

[0036] (3) A dispersion of 1 mg / ml of aminated carbon nanotubes in N,N-dimethylformamide is prepared, and ultrasonically treated in a water bath for 10 min;

[0037] (4) The solutions and dispersions obtained in steps (2) and (3) are mixed in a 1:1 ratio (by volume), and ultrasonically treated for 20 min;

[0038] (5) The un-sized carbon fibers are soaked in the mixture obtained in step (4) for 60 min;

[0039] (6) The fibers are taken out of the mixture, washed with ethanol and water in sequence, and dried.

[0040] Example 4

[0041] (1) Measure 20 mL of tetrahydrofuran into a flask, add 1.8 mmol of 2-(N- carbazolyl)methyl ethyl methacrylate, 1.8 mmol of glycidyl methacrylate, stir for 30 min, then add 0.0120 g of 2,2'-azobis(2-methylpropionitrile) and continue stirring for 30 min. During the addition of the initiator, nitrogen is continuously introduced. After the temperature is raised to 70°C and refluxing occurs, the nitrogen is turned off, and the reaction is continued for 24 h. After the reaction is completed, the flask contains a light yellow, slightly viscous liquid. The liquid in the flask is poured into 300 mL of petroleum ether, and a large amount of milky white solid appears. The solid is filtered three times, washed with alcohol, and dried in a vacuum oven to obtain a milky white solid, which is 2-(N-carbazolyl)methyl ethyl methacrylate-glycidyl methacrylate copolymer; ， - azobisdimethylvaleronitrile, nitrogen is continuously introduced during the addition, the temperature is raised to 70°C and refluxing occurs, then the nitrogen is turned off, and the reaction is continued for 24 h. After the reaction is completed, the flask contains a light yellow, slightly viscous liquid. The liquid in the flask is poured into 300 mL of petroleum ether, and a large amount of milky white solid appears. The solid is filtered three times, washed with alcohol, and dried in a vacuum oven to obtain a milky white solid, which is 2-(N-carbazolyl)methyl ethyl methacrylate-glycidyl methacrylate copolymer;

[0042] (2) The copolymer obtained in step (1) is dissolved in N,N-dimethylformamide to a concentration of 1 mg / ml, and stirred for 10 min;

[0043] (3) Prepare a dispersion of 1 mg / ml of amino-carbon nanotubes in N,N- dimethylformamide, and treat with ultrasonic water bath for 10 min;

[0044] (4) Mix the solutions obtained in steps (2), (3) in a 1:1 ratio (by volume), and treat with ultrasonic for 20 min;

[0045] (5) Soak the un-sized carbon fibers in the mixed solution obtained in step (4) for 30 min;

[0046] (6) Take the fibers out of the mixed solution, wash them with ethanol and water in sequence, and dry them.

[0047] Example 5

[0048] (1) Measure 20 mL of tetrahydrofuran into a flask, add 1.6 mmol of 2-(N- carbazolyl)methyl acrylate and 1.6 mmol of glycidyl methacrylate to it, stir for 30 min, and then add 0.0100 g of 2,2'-azobis(2-methylpropionitrile) to it, continuously pass nitrogen during the feeding process, heat to 70°C to cause reflux, and then turn off the nitrogen, continue the reaction for 24 h. After the reaction is completed, the flask contains a light yellow, slightly viscous liquid, pour the liquid in the flask into 300 mL of petroleum ether, a large amount of milky white solid appears, perform three times of suction filtration, and wash with alcohol, and then place in a vacuum oven to dry, to obtain a milky white solid, to obtain a 2-(N-carbazolyl)methyl acrylate-glycidyl methacrylate copolymer; ， - azobisdimethylvaleronitrile, continuously pass nitrogen during the feeding process, heat to 70°C to cause reflux, and then turn off the nitrogen, continue the reaction for 24 h. After the reaction is completed, the flask contains a light yellow, slightly viscous liquid, pour the liquid in the flask into 300 mL of petroleum ether, a large amount of milky white solid appears, perform three times of suction filtration, and wash with alcohol, and then place in a vacuum oven to dry, to obtain a milky white solid, to obtain a 2-(N-carbazolyl)methyl acrylate-glycidyl methacrylate copolymer;

[0049] (2) Dissolve the copolymer obtained in step (1) in N,N-dimethylformamide to a concentration of 1 mg / ml, and stir for 10 min;

[0050] (3) Prepare a dispersion of 1 mg / ml of amino-carbon nanotubes in N,N- dimethylformamide, and treat with ultrasonic water bath for 10 min;

[0051] (4) Mix the solutions obtained in steps (2), (3) in a 1:1 ratio (by volume), and treat with ultrasonic for 40 min;

[0052] (5) Soak the un-sized carbon fibers in the mixed solution obtained in step (4) for 90 min;

[0053] (6) Take the fibers out of the mixed solution, wash them with ethanol and water in sequence, and dry them.

[0054] Example 6

[0055] Internal damage self-reporting function: take the modified carbon fiber of example 5, under the laser confocal scanning microscope, respectively observe the luminescence condition before and after the interface shear strength test, compared with the fluorescence of the sample before the test, the fluorescence of the damaged site after the interface shear strength test disappears.

[0056] Comparative example

[0057] The main sizing agent epoxy resin 1.5 g, mixed emulsifier Span 80 and Tween 40 and 0.25 g and deionized water 98.75 g were weighed respectively, wherein the mass ratio of the mixed emulsifier Span 80 and Tween 40 was 2:3, and the HLB value was 11.08. The main sizing agent and the emulsifier were added into the deionized water, the system temperature was controlled at 80℃, and high-speed stirring was carried out by the emulsifying machine at a speed of 13000 rpm for 50 min, and the epoxy resin emulsion was obtained after cooling. To the epoxy resin emulsion, 0.8 g of carboxylated single-walled carbon nanotube with a length of 1 μm and 0.8 g of silane coupling agent γ-aminopropyl triethoxysilane were added. After mixing uniformly, ultrasonic treatment was carried out for 2 h, and then stirring was carried out at a speed of 1000 rpm for 9 h, to obtain the emulsion type carbon fiber sizing agent containing carbon nanotubes. The mass fraction of each component of the sizing agent was as follows: main sizing agent 1.3%, emulsifier 0.5%, deionized water 98.2%, carbon nanotube addition amount 0.8%, and dispersant addition amount 0.8%.

[0058] The performance data of examples 1-5 and the comparative example are shown in the following table:

[0059] Interfacial shear strength (MPa) Example 1 86.6 Example 2 89.2 Example 3 87.1 Example 4 93.5 Example 5 88.7 Comparative Example 83.5

[0060] The above data show that, compared with the comparative example, the structure obtained in examples 1-5 has better interface enhancement effect on carbon fiber; in addition, by adjusting various process parameters, the sizing structure and effect will also be affected, wherein the interface shear strength of the fiber after sizing in example 4 is the largest.

[0061] Concentration and ratio of 2-(N-carbazolyl) ethyl methacrylate and glycidyl methacrylate, 2-2 ， The mass of azobisisobutyronitrile, the reaction temperature and the reaction time will all affect the synthesis and chemical structure of the copolymer, and a suitable molecular structure is conducive to the improvement of the interface shear strength of the carbon fiber composite. The ratio of the carbon nanotube and the binary copolymer, and the concentration of the carbon nanotube will all affect the structure of the coating layer formed on the surface of the carbon fiber, and then affect the modification effect. The ultrasonic treatment time will affect the dispersion state of the carbon nanotube, and then affect the modification effect. The soaking time will affect the thickness of the coating layer on the surface of the fiber, and too high or too low thickness is not conducive to the improvement of the interface shear strength.

[0062] The sizing agent for carbon fiber interface modification provided by the application can impart strong interface shear strength to carbon fibers, and can be used as a sizing agent for automobile and aerospace reinforced composites.

[0063] The above is only a specific embodiment of the application, and cannot limit the scope of the application. The replacement of equivalent components or equivalent changes and modifications made within the scope of the patent protection of the application shall still fall within the scope of the claims of the application.

Claims

1. An interfacially modified carbon fiber material comprising carbon fibers and a coating layer; characterized in that, The coating layer is coated on the surface of the fiber and has a fluorescent effect; the coating layer comprises 2-(N-carbazolyl) methyl acrylate-glycidyl methacrylate binary copolymer and aminated carbon nanotubes; the mass ratio of the aminated carbon nanotubes to the 2-(N-carbazolyl) methyl acrylate-glycidyl methacrylate binary copolymer is (0.2-4):1; The preparation method of the interface-modified carbon fiber material comprises the following steps: (1) preparing 2-(N-carbazolyl)methyl ethyl methacrylate, glycidyl methacrylate, 2-2 ， - a mixture solution of azobisisobutyronitrile in tetrahydrofuran; heating the reaction under nitrogen atmosphere; at the end of the reaction, precipitating with petroleum ether, filtering, washing with ethanol, and drying to obtain 2-(N-carbazolyl)methyl ethyl methacrylate-glycidyl methacrylate copolymer; the mass ratio of 2-(N-carbazolyl)methyl ethyl methacrylate to glycidyl methacrylate is (0.5-2):1; 2-2 ， - the mass of azobisisobutyronitrile is 0.7%-2% of the total mass of the reactants; the petroleum ether used is sufficient to add until no more precipitation occurs; (2) mixing the binary copolymer and the carbon nanotubes obtained in the step (1) to configure an N,N-dimethylformamide mixed dispersion liquid and performing ultrasonic treatment; (3) soaking the unsized carbon fiber in the dispersion liquid obtained in the step (2); (4) taking out the carbon fiber and washing it with water and ethanol in sequence and drying it.

2. The interface-modified carbon fiber material according to claim 1, wherein In the step (1), the concentration of the 2-(N-carbazolyl) methyl acrylate and the glycidyl methacrylate is both 0.05-0.10 mmol / ml.

3. The interface-modified carbon fiber material of claim 1, wherein, In the step (1), the reaction temperature is 65-75 ℃ and the reaction time is 20-30 h.

4. The interface-modified carbon fiber material of claim 1, wherein, In the step (2), the mass ratio of the aminated carbon nanotubes to the 2-(N-carbazolyl) methyl acrylate-glycidyl methacrylate binary copolymer is (0.2-4):1 and the concentration of the carbon nanotubes is 1-3 mg / ml; the ultrasonic treatment time is 10-40 min.

5. The interface-modified carbon fiber material of claim 1, wherein, In the step (3), the soaking time of the carbon fiber is 20-90 min.

6. The interface-modified carbon fiber material of claim 1, wherein In the step (4), the water used is deionized water or tap water.

7. Application of the interface-modified carbon fiber material of claim 1 to automotive and aerospace reinforced composites.

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