CN118029160A - Carbon fiber surface modification method, modified carbon fiber and carbon fiber reinforced resin-based composite material - Google Patents

Abstract

The invention discloses a carbon fiber surface modification method, modified carbon fibers and a carbon fiber reinforced resin matrix composite material, and belongs to the technical field of carbon fiber surface modification. The carbon fiber surface modification method of the invention comprises the following steps: placing the desized carbon fiber into a polyetherimide solution, performing ultrasonic treatment at the temperature of-5-3 ℃ for 10-30 min, and then performing heat preservation and standing for 20-30 h; and taking out after standing, and evaporating and drying at 10-30 ℃. The uniformly distributed hemispherical PEI nano particles are obtained on the surface of the carbon fiber through low-temperature evaporation induction, so that the surface roughness and the surface activity of the carbon fiber are increased, the infiltration of the resin is facilitated, and the mechanical interlocking is formed between the resin and the carbon fiber, and the interface combination between the carbon fiber and the resin is improved. Meanwhile, the carbon fiber surface modification method provided by the invention is simple, strong in operability, low in cost, high in safety and suitable for industrial production, and the operation process is carried out at a lower temperature.

Description

A carbon fiber surface modification method, modified carbon fiber and carbon fiber reinforced resin-based composite material

Technical Field

The invention relates to the technical field of carbon fiber surface modification, and in particular to a carbon fiber surface modification method, modified carbon fiber and a carbon fiber reinforced resin-based composite material.

Background technique

The information disclosed in the background of the invention is only intended to enhance the understanding of the overall background of the invention and should not be necessarily regarded as an acknowledgment or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art.

Carbon fiber reinforced resin composites (CFRP) are widely used in aerospace, transportation and civil fields due to their excellent mechanical properties and low density. In composite materials, carbon fiber reinforcement is the main load-bearing component, resin matrix is the medium for load transmission, and the interface is to ensure the continuous transmission of load between reinforcement and matrix. Therefore, the interface is often the key factor in determining the mechanical properties of composite materials, so the interface bonding and mechanical properties of composite materials can be improved by surface modification of carbon fiber.

In recent years, in addition to wet and dry modifications of carbon fiber, "multi-scale" modification has attracted more and more attention from researchers, that is, grafting nanomaterials on the surface of carbon fiber to increase the surface roughness of the carbon fiber and enhance the surface activity, which is beneficial to the infiltration of resin and the formation of mechanical interlocking with the resin.

Patent CN 104499270 B (authorization announcement date: 2016.07.06) discloses a method for modifying the surface of carbon fiber with nano-silicon dioxide, which performs acetylation treatment on the surface of carbon fiber and then grafts the azidized nano-silicon dioxide through chemical reaction, thereby increasing the wettability and roughness of the carbon fiber surface. However, this method is complicated and cumbersome, the preparation process is long, and the raw materials and preparation process are dangerous and costly, making it difficult to apply industrially.

Patent CN 107407042 B (authorization announcement date: 2020.07.21) discloses a fiber sizing system containing nanoparticles for carbon fiber, which uses an aqueous emulsion containing silica nanoparticles as a sizing agent to modify the carbon fiber to improve the adhesion and wetting properties between the carbon fiber and the resin. However, the sizing agent is not environmentally friendly, has poor stability, and has a complicated preparation process, making it difficult to industrialize.

Therefore, how to provide a simple, low-cost, and high-safe method for grafting nanomaterials on the surface of carbon fiber is an urgent problem to be solved.

Summary of the invention

In view of this, the present invention provides a carbon fiber surface modification method, modified carbon fiber and carbon fiber reinforced resin-based composite material. The present invention improves the surface roughness, surface wettability and activity of the carbon fiber by inducing polyetherimide (PEI) nanoparticles on the carbon fiber surface by low-temperature evaporation, which is beneficial to the infiltration of the resin and the formation of mechanical interlocking with the resin, thereby improving the interface bonding between the carbon fiber and the resin; the surface modification method is simple, low-cost and highly safe.

In a first aspect, the present invention provides a method for surface modification of carbon fiber, comprising the following steps:

The desized carbon fiber is placed in a polyetherimide solution, ultrasonicated at -5 to 3°C for 10 to 30 minutes, and then kept warm and allowed to stand for 20 to 30 hours; after standing, the carbon fiber is taken out and placed at 10 to 30°C for evaporation and drying.

Preferably, the preparation method of the desizing carbon fiber is: heating the carbon fiber to 400-500° C. in an inert gas atmosphere, keeping the temperature for 1-2 hours, cooling to room temperature, washing and drying.

Furthermore, the inert gas includes one or both of nitrogen and argon; and the solvent used in the washing step is water or ethanol.

Preferably, before placing the desized carbon fibers in the polyetherimide solution, the desized carbon fibers are pre-impregnated with a solvent of the polyetherimide solution for a period of 10 to 30 minutes.

Preferably, the usage ratio of the desized carbon fiber to the polyetherimide solution is 1 g: 300-700 mL.

Preferably, the mass concentration of the polyetherimide solution is 0.1-0.6 wt %.

Preferably, the solvent of the polyetherimide solution is selected from one or more of N-methylpyrrolidone (NMP), N,N-dimethylformamide (DMF) or N,N-dimethylacetamide (DMAc).

Furthermore, the preparation method of the polyetherimide solution is: placing polyetherimide in a solvent, and stirring and dissolving the polyetherimide at 60 to 80° C. for 1 to 4 hours.

In a second aspect, the present invention provides a modified carbon fiber prepared by the above carbon fiber surface modification method.

In a third aspect, the present invention provides a carbon fiber reinforced resin-based composite material comprising the above-mentioned modified carbon fiber.

Compared with the prior art, the present invention has achieved the following beneficial effects:

(1) The present invention provides a method for modifying the surface of carbon fiber, wherein hemispherical PEI nanoparticles uniformly distributed on the surface of the carbon fiber are obtained by inducing low-temperature evaporation, which can increase the surface roughness of the carbon fiber and improve the surface activity, which is beneficial to the infiltration of the resin and the formation of mechanical interlocking with the resin, thereby improving the interface bonding between the carbon fiber and the resin.

(2) The carbon fiber surface modification method provided by the present invention is simple, easy to operate, and low in cost. Moreover, the operation process is carried out at a relatively low temperature, which is highly safe and suitable for industrial production.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings constituting part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their description are used to explain the present invention and do not constitute an improper limitation of the present invention. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative work.

FIG1 is a surface scanning electron microscope image of the modified carbon fiber of Example 1 of the present invention;

FIG2 is a surface scanning electron microscope image of the modified carbon fiber of Example 2 of the present invention;

FIG3 is a surface scanning electron microscope image of the modified carbon fiber of Comparative Example 1 of the present invention;

FIG4 is a surface scanning electron microscope image of the modified carbon fiber of Comparative Example 2 of the present invention;

5 is a graph of interlaminar shear strength of composite materials prepared from modified carbon fibers of Example 1 of the present invention, Comparative Examples 1-2, and untreated carbon fibers.

Detailed ways

It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

The present invention provides a carbon fiber surface modification method, comprising the following steps:

The desized carbon fiber is placed in a polyetherimide solution, ultrasonicated at -5 to 3°C for 10 to 30 minutes, and then kept warm and allowed to stand for 20 to 30 hours; after standing, the carbon fiber is taken out and placed at 10 to 30°C for evaporation and drying.

The present invention adopts polyetherimide (PEI) nanoparticles to carry out surface modification on carbon fiber. PEI is an amorphous thermoplastic. The imide bond containing benzene ring and semi-trapezoid in the molecular chain gives it excellent heat resistance, and the benzene ring and imide bond in PEI can play a chemical bond with resin, thereby strengthening the interface bonding with resin. The processing temperature is up to more than 350°C, and it has excellent chemical resistance and good mechanical properties. PEI nanoparticles are combined with carbon fiber to improve the surface roughness and wettability of carbon fiber, thereby improving the interface bonding performance between carbon fiber and resin.

The present invention adopts low-temperature evaporation induction method, and the evaporation process is a dynamic process, and as the solvent decreases, the solute concentration increases. When the temperature is low, the speed of evaporation is very slow, and the PEI chain will shrink from the long chain state to the particle state under the action of surface tension, and finally shrink to form hemispherical nanoparticles. Temperature plays a very critical role in the surface modification process. If the temperature is too high, PEI is difficult to form nanoparticles on the carbon fiber surface, thereby failing to give full play to the role of PEI in promoting the combination of carbon fiber and resin.

In the process of carbon fiber production, carbon fiber needs to be sized to reduce the surface friction of carbon fiber and avoid the generation of lint during transportation. However, commercial sizing agents are less effective in improving the interface properties of composite materials. Therefore, it is necessary to remove the commercial sizing agents in the carbon fiber production process (i.e., desizing). In the present invention, the preparation method of the desizing carbon fiber is as follows: heating the carbon fiber to 400-500°C in an inert gas atmosphere, keeping the temperature for 1-2 hours, cooling to room temperature, washing, and drying.

In the preparation process of desizing carbon fiber, the inert gas includes one or both of nitrogen and argon, and the solvent used in the washing step is water or ethanol to remove impurities on the surface of the carbon fiber.

The present invention places the desized carbon fiber before the polyetherimide solution, and pre-impregnates the desized carbon fiber with the solvent of the polyetherimide solution for 10 to 30 minutes. This step is to increase the wetting rate of the desized carbon fiber in the polyetherimide solution.

In the present invention, in order to ensure that the polyetherimide can be evenly impregnated into the desized carbon fiber, the usage ratio of the desized carbon fiber to the polyetherimide solution is 1 g: 300-700 mL.

In the present invention, the mass concentration of the polyetherimide solution is 0.1-0.6 wt %. When the concentration is too high, the PEI nanoparticles will agglomerate, which is not conducive to the combination with the resin.

The solvent of the polyetherimide solution of the present invention is selected from one or more of N-methylpyrrolidone (NMP), N,N-dimethylformamide (DMF) or N,N-dimethylacetamide (DMAc). The above solvent has good solubility for PEI, has a high boiling point, is not easy to volatilize, and will not solidify at the working temperature.

In order to obtain a polyetherimide solution with good solubility, the polyetherimide is placed in the above solvent and stirred and dissolved at 60-80° C. for 1-4 hours.

The present invention also provides a modified carbon fiber prepared by the above carbon fiber surface modification method. The surface of the prepared modified carbon fiber has PEI nanoparticles uniformly distributed in a hemispherical structure.

The present invention also provides a carbon fiber reinforced resin-based composite material, comprising the modified carbon fiber. The present invention does not specifically limit the type of resin, which can be either a thermosetting resin or a thermoplastic resin. For example, it can be selected from epoxy resin, phenolic resin, polyimide resin, polypropylene resin, polyamide resin, polystyrene resin, etc.

The technical solution of the present invention is further described below in conjunction with specific embodiments.

Example 1

This embodiment provides a method for inducing PEI nanoparticles by low-temperature evaporation on the surface of carbon fiber.

Step 1: Place the carbon fiber in a tubular furnace, heat it to 450°C in a nitrogen atmosphere for 1.5 hours to remove the sizing agent on the surface of the carbon fiber, cool it to room temperature and take it out, then wash it several times with deionized water and put it in an oven to dry to obtain desized carbon fiber.

Step 2: Place 1 g of the desized carbon fiber obtained in step 1 in N-methylpyrrolidone for 15 minutes.

Step 3: Dissolve PEI in N-methylpyrrolidone at 70° C. and stir for 2 h, controlling the mass fraction of PEI in N-methylpyrrolidone to be 0.2 wt %.

Step 4: The carbon fiber obtained in step 2 is ultrasonically treated in 500 mL of the PEI solution obtained in step 3 in an ice bath (0° C.) for 20 min, and then placed in an ice bath (0° C.) for 24 h.

Step 5: Evaporate the carbon fiber obtained in step 4 at 20° C. until the carbon fiber is dry to obtain modified carbon fiber.

The surface scanning electron microscope image of the modified carbon fiber prepared in this example is shown in Figure 1. It can be seen that the surface of the carbon fiber is evenly loaded with PEI nanoparticles, which increases the roughness of the carbon fiber surface. The PEI nanoparticles are hemispherical on the surface of the carbon fiber and have a large specific surface area.

Example 2

This embodiment provides a method for inducing PEI nanoparticles by low-temperature evaporation on the surface of carbon fiber.

Step 1: Place the carbon fiber in a tubular furnace, heat it to 450°C in a nitrogen atmosphere for 1.5 hours to remove the sizing agent on the surface of the carbon fiber, cool it to room temperature and take it out, then wash it several times with deionized water and put it in an oven to dry to obtain desized carbon fiber.

Step 2: Place 1 g of the desized carbon fiber obtained in step 1 in N-methylpyrrolidone for 15 minutes.

Step 3: Dissolve PEI in N-methylpyrrolidone at 70° C. and stir for 2 h, so that the mass fraction of PEI in the N-methylpyrrolidone obtained in step 3 is 0.3 wt %.

Step 4: The carbon fiber obtained in step 2 is ultrasonically treated in 500 mL of the PEI solution obtained in step 3 in an ice bath (0° C.) for 20 min, and then placed in an ice bath (0° C.) for 24 h.

Step 5: Evaporate the carbon fiber obtained in step 4 at 20° C. until the carbon fiber is dry to obtain modified carbon fiber.

The surface scanning electron microscope image of the modified carbon fiber prepared in this embodiment is shown in Figure 2. It can be seen that the PEI nanoparticles are evenly loaded on the surface of the carbon fiber, increasing the roughness of the carbon fiber surface; the PEI nanoparticles are hemispherical on the surface of the carbon fiber and have a large specific surface area.

Example 3

Step 1: Place the carbon fiber in a tubular furnace, heat it to 450°C in a nitrogen atmosphere for 1.5 hours to remove the sizing agent on the surface of the carbon fiber, cool it to room temperature and take it out, then wash it several times with deionized water and put it in an oven to dry to obtain desized carbon fiber.

Step 2: Place 1 g of the desized carbon fiber obtained in step 1 into N,N-dimethylformamide for 15 minutes.

Step 3: Dissolve PEI in N,N-dimethylformamide at 70°C and stir for 2 hours to make the mass fraction of PEI in N,N-dimethylformamide be 0.4 wt%.

Step 4: The carbon fiber obtained in step 2 is ultrasonically treated in 500 mL of the PEI solution obtained in step 3 in an ice bath (0° C.) for 20 min, and then placed in an ice bath (0° C.) for 24 h.

Step 5: Evaporate the carbon fiber obtained in step 4 at 20° C. until the carbon fiber is dry to obtain modified carbon fiber.

Example 4

Step 1: Place the carbon fiber in a tubular furnace, heat it to 450°C in a nitrogen atmosphere for 1.5 hours to remove the sizing agent on the surface of the carbon fiber, cool it to room temperature and take it out, then wash it several times with deionized water and put it in an oven to dry to obtain desized carbon fiber.

Step 2: Place 1 g of the desized carbon fiber obtained in step 1 in N-methylpyrrolidone for 15 minutes.

Step 3: Dissolve PEI in N-methylpyrrolidone in a 70° C. oil bath and stir for 2 h to make the mass fraction of PEI in N-methylpyrrolidone be 0.5 wt %.

Step 4: The carbon fiber obtained in step 2 is ultrasonically treated in 500 mL of the PEI solution obtained in step 3 in an ice bath (0° C.) for 20 min, and then placed in an ice bath (0° C.) for 24 h.

Step 5: Evaporate the carbon fiber obtained in step 4 at 20° C. until the carbon fiber is dry to obtain modified carbon fiber.

Comparative Example 1

Compared with Example 1, the difference is that step five of this comparative example is as follows: the carbon fiber obtained in step four is evaporated at 40° C. until the carbon fiber is dry to obtain modified carbon fiber.

The surface scanning electron microscope image of the modified carbon fiber of this comparative example is shown in Figure 3. It can be seen that there are unevenly sized protrusions on the surface of the carbon fiber. The particle size of the protrusions is very small, and there are no hemispherical nanoparticles with larger particle size, and the roughness is low.

Comparative Example 2

Compared with Example 1, the difference is that step five of this comparative example is as follows: the carbon fiber obtained in step four is evaporated at 80° C. until the carbon fiber is dry to obtain modified carbon fiber.

The surface scanning electron microscope image of the modified carbon fiber of this comparative example is shown in FIG4 . It can be seen that the surface smoothness of the carbon fiber is relatively high, and the formation of nanoparticles is not observed.

Test example

Carbon fiber reinforced polypropylene composite materials were prepared using untreated carbon fiber, Comparative Example 1, Comparative Example 2 and Example 1, and the interlaminar shear strength of the prepared carbon fiber reinforced polypropylene composite materials was measured. The results are shown in FIG1 .

It can be seen that the interlaminar shear strength of the composite material prepared by the modified carbon fiber of Example 1 is the highest, which is 119.35% higher than that of the untreated one. This is because the hemispherical PEI nanoparticles form a mechanical interlocking effect with the polypropylene resin. When the composite material is damaged by stress, the crack propagation at the interface is hindered by the PEI nanoparticles, and the interface failure requires more energy, and its cracks mainly extend along the resin rather than the interface, so the interlaminar performance of the composite material is improved. However, the interlaminar shear strength of the composite material prepared by the modified carbon fiber of Comparative Examples 1 and Comparative Examples 2 is not much improved compared to the untreated one, which shows that the mechanical interlocking effect of the PEI nanoparticles with the resin is the strongest only when they are hemispherical, so that the composite material has the best interface performance.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims (10)

1. The carbon fiber surface modification method is characterized by comprising the following steps of:

Placing the desized carbon fiber into a polyetherimide solution, performing ultrasonic treatment at the temperature of-5-3 ℃ for 10-30 min, and then performing heat preservation and standing for 20-30 h; and taking out after standing, and evaporating and drying at 10-30 ℃.

2. The method for modifying the surface of carbon fiber according to claim 1, wherein the method for preparing desized carbon fiber comprises the following steps: heating the carbon fiber to 400-500 ℃ in an inert gas atmosphere, preserving heat for 1-2 h, cooling to room temperature, washing and drying to obtain the carbon fiber.

3. The method of modifying a surface of a carbon fiber according to claim 2, wherein the inert gas comprises one or both of nitrogen and argon; the solvent adopted in the washing step is water or ethanol.

4. The method for modifying the surface of carbon fibers according to claim 1, wherein the desized carbon fibers are pre-impregnated with a solvent of the polyetherimide solution for 10 to 30 minutes before being placed in the polyetherimide solution.

5. The method for modifying the surface of a carbon fiber according to claim 1, wherein the ratio of the desized carbon fiber to the polyetherimide solution is 1g: 300-700 mL.

6. The method for modifying the surface of a carbon fiber according to claim 1, wherein the mass concentration of the polyetherimide solution is 0.1 to 0.6wt%.

7. The method of modifying the surface of a carbon fiber according to claim 1, wherein the solvent of the polyetherimide solution is selected from one or more of N-methylpyrrolidone (NMP), N-Dimethylformamide (DMF), or N, N-dimethylacetamide (DMAc).

8. The method for modifying the surface of a carbon fiber according to claim 7, wherein the method for preparing the polyetherimide solution comprises the steps of: the polyetherimide is placed in a solvent and stirred and dissolved for 1 to 4 hours at the temperature of between 60 and 80 ℃.

9. A modified carbon fiber produced by the carbon fiber surface modification method according to any one of claims 1 to 8.

10. A carbon fiber reinforced resin matrix composite comprising the modified carbon fiber of claim 9.