阅读说明：本技术 一种碳纤维/聚乙烯亚胺/碳纳米管多尺度增强体的制备方法 (Preparation method of carbon fiber/polyethyleneimine/carbon nanotube multi-scale reinforcement ) 是由 韩萍 马丽春 宋国君 李晓茹 路庆标 李佩佳 于 2019-09-29 设计创作，主要内容包括：一种碳纤维/聚乙烯亚胺/碳纳米管多尺度增强体的制备方法,它涉及一种碳纤维的改性方法。本发明的目的是要解决现有碳纳米管接枝到碳纤维表面的方法制备的碳纳米管接枝碳纤维中CFs与CNTs之间的物理吸附较弱和其与基体的界面结合粘性差的问题。方法：一、碳纤维的抽提；二、碳纤维的氧化；三、接枝聚乙烯亚胺；四、碳纳米管的羧基化；五、碳纤维接枝碳纳米管,得到碳纤维/聚乙烯亚胺/碳纳米管多尺度增强体。本发明制备的碳纤维/聚乙烯亚胺/碳纳米管多尺度增强体能够极大提高碳纤维/环氧树脂复合材料的界面性能和力学性能。本发明可获得一种碳纤维/聚乙烯亚胺/碳纳米管多尺度增强体。(A preparation method of a carbon fiber/polyethyleneimine/carbon nanotube multi-scale reinforcement relates to a modification method of carbon fiber. The invention aims to solve the problems that the physical adsorption between CFs and CNTs is weak and the interface bonding viscosity between the CFs and CNTs and a matrix is poor in the carbon nanotube grafted carbon fiber prepared by the existing method for grafting the carbon nanotube onto the surface of the carbon fiber. The method comprises the following steps: firstly, extracting carbon fibers; secondly, oxidizing the carbon fiber; thirdly, grafting polyethyleneimine; fourthly, carboxylation of the carbon nano tube; and fifthly, grafting the carbon nano tube by the carbon fiber to obtain the carbon fiber/polyethyleneimine/carbon nano tube multi-scale reinforcement. The carbon fiber/polyethyleneimine/carbon nanotube multi-scale reinforcement prepared by the method can greatly improve the interface performance and mechanical property of the carbon fiber/epoxy resin composite material. The invention can obtain a carbon fiber/polyethyleneimine/carbon nanotube multi-scale reinforcement.)

1. A preparation method of a carbon fiber/polyethyleneimine/carbon nanotube multi-scale reinforcement is characterized in that the preparation method of the carbon fiber/polyethyleneimine/carbon nanotube multi-scale reinforcement is completed according to the following steps:

firstly, extracting carbon fibers:

firstly, placing carbon fibers in a Soxhlet extractor, then heating and refluxing the carbon fibers by using acetone to remove sizing agent and impurities on the surfaces of the carbon fibers, and finally placing the carbon fibers in a vacuum drying oven for drying to obtain carbon fibers extracted by the acetone;

secondly, oxidation of carbon fibers:

firstly, immersing carbon fiber extracted by acetone into concentrated nitric acid, and then placing the carbon fiber in an oil bath for heating and refluxing to obtain oxidized carbon fiber;

secondly, cleaning the oxidized carbon fibers to be neutral by using distilled water, and heating and refluxing by using absolute ethyl alcohol to obtain carbon fibers extracted by the absolute ethyl alcohol;

thirdly, placing the carbon fiber extracted by the absolute ethyl alcohol into a vacuum drying oven for drying to obtain the cleaned oxidized carbon fiber;

thirdly, grafting polyethyleneimine:

adding polyethyleneimine into 1-methyl-2-pyrrolidone, and performing ultrasonic dispersion to obtain a polyethyleneimine solution with the mass fraction of 10%; immersing the cleaned oxidized carbon fiber into a polyethyleneimine solution with the mass fraction of 10%, and reacting under the conditions of inert atmosphere and room temperature to obtain a reaction solution I;

secondly, adding polyethyleneimine into 1-methyl-2-pyrrolidone, and performing ultrasonic dispersion to obtain a polyethyleneimine solution with the mass fraction of 20%; adding a polyethyleneimine solution with the mass fraction of 20% into the reaction solution I, and reacting under the conditions of inert atmosphere and room temperature to obtain a reaction solution II;

thirdly, adding polyethyleneimine into 1-methyl-2-pyrrolidone, and performing ultrasonic dispersion to obtain a polyethyleneimine solution with the mass fraction of 20%; adding a polyethyleneimine solution with the mass fraction of 20% into the reaction liquid II, and then placing the reaction liquid II in an oil bath for heating reflux reaction to obtain a reaction liquid III;

fourthly, taking the carbon fiber out of the reaction liquid III, cleaning, and finally drying in a vacuum drying oven to obtain the carbon fiber grafted with the polyethyleneimine;

and fourthly, carboxylation of the carbon nano tube:

firstly, adding a carbon nano tube into mixed acid, and then placing the mixed acid in an oil bath for heating and refluxing to obtain a reaction product;

the volume ratio of the mass of the carbon nano tube to the mixed acid in the fourth step is (0.1 g-0.3 g) 100 mL;

secondly, washing the reaction product to be neutral by using distilled water, and filtering by using a microporous filter membrane to obtain a solid substance; drying the solid matter in a vacuum drying oven to obtain a carboxylated carbon nanotube;

fifthly, carbon fiber grafting carbon nano tube:

adding a carboxylated carbon nano tube into N, N-dimethylformamide, and performing ultrasonic dispersion to obtain a carboxylated carbon nano tube dispersion liquid;

the mass ratio of the carboxylated carbon nano tube in the fifth step to the volume ratio of the N, N-dimethylformamide is 0.1g (60 mL-80 mL);

adding 2- (7-azobenzotriazol) -N, N, N ', N' -tetramethylurea hexafluorophosphate into the carboxylated carbon nano tube dispersion liquid, and performing ultrasonic dispersion to obtain a carbon nano tube/N, N-dimethylformamide dispersion liquid;

the volume ratio of the mass of the 2- (7-azobenzotriazol) -N, N, N ', N' -tetramethylurea hexafluorophosphate to the volume of the carboxylated carbon nano tube dispersion liquid in the fifth step is (5 mg-10 mg) to (60 mL-80 mL);

thirdly, soaking the carbon fiber grafted with the polyethyleneimine into the carbon nano tube/N, N-dimethylformamide dispersion liquid, then stirring at room temperature, and finally standing at room temperature;

fifthly, the mass ratio of the carbon fiber grafted with the polyethyleneimine to the carbon nano tube/carboxylated carbon nano tube in the N, N-dimethylformamide dispersion liquid is 2: 1;

and fourthly, taking out the carbon fibers, alternately washing the carbon fibers by using N, N-dimethylformamide and distilled water, and drying the washed carbon fibers in a vacuum drying box to obtain the carbon fiber/polyethyleneimine/carbon nanotube multi-scale reinforcement.

2. The method for preparing the carbon fiber/polyethyleneimine/carbon nanotube multi-scale reinforcement according to claim 1, wherein the temperature of the heating reflux in the step one is 56.5-57 ℃, and the time of the heating reflux is 24-48 h; the drying parameters in the second step are as follows: the temperature is 50-55 ℃, the vacuum degree is-0.1 MPa, and the vacuum drying time is 12-24 h; the mass fraction of the concentrated nitric acid in the second step is 68 percent; and the heating reflux temperature in the second step is 100 ℃, and the heating reflux time is 2 hours.

3. The method for preparing the carbon fiber/polyethyleneimine/carbon nanotube multi-scale reinforcement according to claim 1, wherein the heating reflux temperature in the second step is 80 ℃, and the heating reflux time is 2-3 h; the drying parameters in the second step and the third step are as follows: the temperature is 50-55 ℃, the vacuum degree is-0.1 MPa, and the vacuum drying time is 10-12 h.

4. The preparation method of the carbon fiber/polyethyleneimine/carbon nanotube multi-scale reinforcement according to claim 1, wherein the ultrasonic dispersion time in the third step is 10-20 min, and the ultrasonic dispersion power is 200-350W; the inert atmosphere in the third step is argon or nitrogen; the reaction time is 34-38 h.

5. The method for preparing the carbon fiber/polyethyleneimine/carbon nanotube multi-scale reinforcement according to claim 1, wherein the ultrasonic dispersion time in the third step is 10-20 min, and the ultrasonic dispersion power is 200-350W; the volume ratio of the polyethyleneimine solution with the mass fraction of 20% to the polyethyleneimine solution with the mass fraction of 10% in the reaction solution I is 1: 1; the inert atmosphere in the third step is argon or nitrogen; the reaction time is 22-26 h.

6. The method for preparing the carbon fiber/polyethyleneimine/carbon nanotube multi-scale reinforcement according to claim 1, wherein the volume ratio of the polyethyleneimine solution with the mass fraction of 20% in the third step to the polyethyleneimine solution with the mass fraction of 10% in the reaction solution II is 1: 1; the temperature of the heating reflux reaction is 154-164 ℃, and the time of the heating reflux reaction is 22-26 h.

7. The method for preparing the carbon fiber/polyethyleneimine/carbon nanotube multi-scale reinforcement according to claim 1, wherein in the step III, the carbon fibers are taken out of the reaction solution III, and are alternately washed 3 to 5 times with N, N-dimethylformamide and distilled water, i.e., the carbon fibers are washed 1 time with N, N-dimethylformamide, and then washed 1 time with distilled water is recorded as alternate washing 1 time; the drying process parameters are as follows: the temperature is 50-55 ℃, the vacuum degree is-0.1 MPa, and the vacuum drying time is 10-14 h.

8. The preparation method of the carbon fiber/polyethyleneimine/carbon nanotube multi-scale reinforcement according to claim 1, wherein the temperature of the heating reflux in the fourth step is 154-164 ℃, and the time of the heating reflux is 8-10 h; the mixed acid in the fourth step is a mixed solution of 65% by mass of nitric acid and 98% by mass of sulfuric acid, wherein the volume ratio of the 65% by mass of nitric acid to the 98% by mass of sulfuric acid is 3: 1; the drying process parameters in the fourth step are as follows: the temperature is 50-55 ℃, the vacuum degree is-0.1 MPa, and the vacuum drying time is 10-14 h.

9. The preparation method of the carbon fiber/polyethyleneimine/carbon nanotube multi-scale reinforcement according to claim 1, wherein the ultrasonic dispersion time in the fifth step is 5-6 h, and the ultrasonic dispersion power is 200-350W; fifthly, the ultrasonic dispersion time is 10-20 min, and the ultrasonic dispersion power is 200-350W; the stirring speed in the fifth step is 60r/min to 100r/min, and the stirring time is 30min to 60 min; and the standing time in the fifth step is 10-12 h.

10. The method for preparing the carbon fiber/polyethyleneimine/carbon nanotube multi-scale reinforcement according to claim 1, wherein in the step fifthly, the carbon fiber is washed with N, N-dimethylformamide and distilled water for 3 to 5 times, i.e., the carbon fiber is washed with N, N-dimethylformamide for 1 time, and then washed with distilled water for 1 time is recorded as alternate washing for 1 time; the drying process parameters in the step V are as follows: the temperature is 50-55 ℃, the vacuum degree is-0.1 MPa, and the vacuum drying time is 10-14 h.

Technical Field

The invention relates to a method for modifying carbon fibers.

Background

The carbon fiber reinforced polymer matrix composite has excellent performances of light weight, high specific strength, high specific stiffness and the like, is widely applied to the fields of aerospace, military and military industry, light-weight automobiles, sports facilities and the like, but has poor interfacial adhesion with a matrix due to smooth surface, chemical inertness and lack of active groups, so that the interface performance and the mechanical property of the composite are low, and the advantage of the carbon fiber as a reinforcement cannot be fully exerted. Carbon Nanotubes (CNTs) are often used as reinforcement for Carbon Fiber (CF) reinforced polymer matrix composites due to their unique nanostructure and excellent mechanical properties. However, due to the structural characteristics, CNTs have high specific surface area, high specific surface energy and strong intermolecular van der waals force, which makes them easy to agglomerate in the matrix and difficult to uniformly disperse, thus being unfavorable for their performance to be fully exerted. The CNTs are grafted to the surface of the CF to prepare the multi-scale carbon fiber reinforcement, so that the problem of agglomeration of the CNTs in a matrix can be avoided, the mechanical meshing effect and the chemical bonding effect of the carbon fibers and matrix resin can be enhanced, and the interface performance and the mechanical performance of the composite material are improved. The methods for grafting CNTs to CF surfaces are mainly Chemical Vapor Deposition (CVD), slurry coating, electrophoretic deposition (EPD), and chemical vapor deposition and chemical grafting. The bonding force between the nano-component and the carbon fiber is weak in a CVD method, a coating method, an electrophoretic deposition method and the like, the preparation condition is harsh, and the introduced catalyst is easy to damage the strength of the carbon fiber body to a certain extent.

Disclosure of Invention

The invention aims to solve the problems of weak physical adsorption between CFs and CNTs and poor interface bonding viscosity with a matrix in the carbon nanotube grafted carbon fiber prepared by the existing method for grafting the carbon nanotube to the surface of the carbon fiber, and provides a preparation method of a carbon fiber/polyethyleneimine/carbon nanotube multi-scale reinforcement.

A preparation method of a carbon fiber/polyethyleneimine/carbon nanotube multi-scale reinforcement is completed according to the following steps:

firstly, extracting carbon fibers:

firstly, placing carbon fibers in a Soxhlet extractor, then heating and refluxing the carbon fibers by using acetone to remove sizing agent and impurities on the surfaces of the carbon fibers, and finally placing the carbon fibers in a vacuum drying oven for drying to obtain carbon fibers extracted by the acetone;

secondly, oxidation of carbon fibers:

firstly, immersing carbon fiber extracted by acetone into concentrated nitric acid, and then placing the carbon fiber in an oil bath for heating and refluxing to obtain oxidized carbon fiber;

secondly, cleaning the oxidized carbon fibers to be neutral by using distilled water, and heating and refluxing by using absolute ethyl alcohol to obtain carbon fibers extracted by the absolute ethyl alcohol;

thirdly, placing the carbon fiber extracted by the absolute ethyl alcohol into a vacuum drying oven for drying to obtain the cleaned oxidized carbon fiber;

thirdly, grafting polyethyleneimine:

adding polyethyleneimine into 1-methyl-2-pyrrolidone, and performing ultrasonic dispersion to obtain a polyethyleneimine solution with the mass fraction of 10%; immersing the cleaned oxidized carbon fiber into a polyethyleneimine solution with the mass fraction of 10%, and reacting under the conditions of inert atmosphere and room temperature to obtain a reaction solution I;

secondly, adding polyethyleneimine into 1-methyl-2-pyrrolidone, and performing ultrasonic dispersion to obtain a polyethyleneimine solution with the mass fraction of 20%; adding a polyethyleneimine solution with the mass fraction of 20% into the reaction solution I, and reacting under the conditions of inert atmosphere and room temperature to obtain a reaction solution II;

thirdly, adding polyethyleneimine into 1-methyl-2-pyrrolidone, and performing ultrasonic dispersion to obtain a polyethyleneimine solution with the mass fraction of 20%; adding a polyethyleneimine solution with the mass fraction of 20% into the reaction liquid II, and then placing the reaction liquid II in an oil bath for heating reflux reaction to obtain a reaction liquid III;

fourthly, taking the carbon fiber out of the reaction liquid III, cleaning, and finally drying in a vacuum drying oven to obtain the carbon fiber grafted with the polyethyleneimine;

and fourthly, carboxylation of the carbon nano tube:

firstly, adding a carbon nano tube into mixed acid, and then placing the mixed acid in an oil bath for heating and refluxing to obtain a reaction product;

the volume ratio of the mass of the carbon nano tube to the mixed acid in the fourth step is (0.1 g-0.3 g) 100 mL;

secondly, washing the reaction product to be neutral by using distilled water, and filtering by using a microporous filter membrane to obtain a solid substance; drying the solid matter in a vacuum drying oven to obtain a carboxylated carbon nanotube;

fifthly, carbon fiber grafting carbon nano tube:

adding a carboxylated carbon nano tube into N, N-dimethylformamide, and performing ultrasonic dispersion to obtain a carboxylated carbon nano tube dispersion liquid;

the mass ratio of the carboxylated carbon nano tube in the fifth step to the volume ratio of the N, N-dimethylformamide is 0.1g (60 mL-80 mL);

adding 2- (7-azobenzotriazol) -N, N, N ', N' -tetramethylurea hexafluorophosphate into the carboxylated carbon nano tube dispersion liquid, and performing ultrasonic dispersion to obtain a carbon nano tube/N, N-dimethylformamide dispersion liquid;

the volume ratio of the mass of the 2- (7-azobenzotriazol) -N, N, N ', N' -tetramethylurea hexafluorophosphate to the volume of the carboxylated carbon nanotube dispersion liquid in the fifth step is 5mg (60-80 mL);

thirdly, soaking the carbon fiber grafted with the polyethyleneimine into the carbon nano tube/N, N-dimethylformamide dispersion liquid, then stirring at room temperature, and finally standing at room temperature;

fifthly, the mass ratio of the carbon fiber grafted with the polyethyleneimine to the carbon nano tube/carboxylated carbon nano tube in the N, N-dimethylformamide dispersion liquid is 2: 1;

and fourthly, taking out the carbon fibers, alternately washing the carbon fibers by using N, N-dimethylformamide and distilled water, and drying the washed carbon fibers in a vacuum drying box to obtain the carbon fiber/polyethyleneimine/carbon nanotube multi-scale reinforcement.

The principle of the invention is as follows:

the invention utilizes the branched structure and amino-rich property of Polyethyleneimine (PEI) and uses PEI as a bridge to graft a carboxylated carbon nanotube onto the surface of Carbon Fibers (CFs) so as to prepare a novel carbon fiber/polyethyleneimine/carbon nanotube multi-scale reinforcement (CF-PEI-CNT multi-scale reinforcement).

The invention has the advantages that:

the invention adopts a novel, simple and mild experimental method, takes Polyethyleneimine (PEI) as a medium, grafts carboxylated Carbon Nanotubes (CNT) on the surface of carbon fibers, and prepares a novel CF-PEI-CNT carbon fiber multi-scale reinforcement;

the carbon nanotubes on the surface of the multi-scale reinforcement of the carbon fiber/polyethyleneimine/carbon nanotube (CF-PEI-CNT) prepared by the method are uniformly distributed and have moderate density, so that the mechanical meshing effect and the chemical bonding effect of the carbon fiber and a resin matrix can be increased to the greatest extent;

the interface performance and the mechanical property of the carbon fiber/polyethyleneimine/carbon nanotube (CF-PEI-CNT) multi-scale reinforcement prepared by the invention can be greatly improved, and compared with unmodified carbon fiber, the interface shear strength (IFSS), the interlayer shear strength (ILSS) and the bending strength are respectively improved by 50-75%, 60-81% and 40-56% compared with the unmodified carbon fiber, and are respectively improved by 10-30%, 20-31% and 10-20% compared with the carbon fiber grafted with polyethyleneimine (CF-PEI).

The invention can obtain a carbon fiber/polyethyleneimine/carbon nanotube multi-scale reinforcement.

Drawings

FIG. 1 is an SEM image of acetone-extracted carbon fibers obtained in step one of the example;

FIG. 2 is an SEM photograph of polyethyleneimine-grafted carbon fibers obtained in step III/IV of the example;

FIG. 3 is an SEM image of the multi-scale reinforcement of carbon fiber/polyethyleneimine/carbon nanotube obtained in the fifth step;

fig. 4 is a bar graph of interfacial shear strength, in which 1 is the interfacial shear strength of an unmodified carbon fiber/epoxy resin composite material, 2 is the interfacial shear strength of a carbon fiber/epoxy resin composite material grafted with polyethyleneimine obtained in the third step of the example, and 3 is the interfacial shear strength of a carbon fiber/polyethyleneimine/carbon nanotube multi-scale reinforcement/epoxy resin composite material obtained in the fifth step of the example;

fig. 5 is a bar graph of interlayer shear strength, in which 1 is the interlayer shear strength of an unmodified carbon fiber/epoxy resin composite material, 2 is the interlayer shear strength of a carbon fiber/epoxy resin composite material grafted with polyethyleneimine obtained in the third step of the example, and 3 is the interlayer shear strength of a carbon fiber/polyethyleneimine/carbon nanotube multi-scale reinforcement/epoxy resin composite material obtained in the fifth step of the example;

fig. 6 is a bar graph of bending strength, in which 1 is the bending strength of an unmodified carbon fiber/epoxy resin composite material, 2 is the bending strength of the carbon fiber/epoxy resin composite material grafted with polyethyleneimine obtained in the third step of the example, and 3 is the bending strength of the carbon fiber/polyethyleneimine/carbon nanotube multi-scale reinforcement/epoxy resin composite material obtained in the fifth step of the example.

Detailed Description