Preparation method of surface-implanted nano-modified carbon fiber based on PAN (Polyacrylonitrile) precursor

Abstract

The invention relates to the technical field of nano materials, and discloses a PAN precursor-based surface-implanted nano modified carbon fiber preparation method, which comprises the following steps: uniformly mixing a to-be-implanted nano material with a dispersion working medium and a dissolution working medium to prepare a discharge electrode, carrying out gas-phase dispersion on the electrode by using a plasma discharge method to obtain gas-phase-dispersed nano particles, and carrying out surface-implanted nano modified carbon fiber preparation on the surface-implanted nano modified carbon fiber to obtain the PAN precursor-based surface-implanted nano modified carbon fiber. Transferring to the surface of a PAN precursor to be modified through a natural injection or guide injection method, placing the PAN precursor receiving the nano particles for a time length tau 1 to change the proportion of a dispersion working medium and a dissolution working medium carried on the surface of the nano particles, and then placing for a time length tau 2 to change the proportion of the dispersion working medium and the dissolution working medium carried on the surface of the nano particles; vaporizing the dispersing working medium and the dissolving working medium to leave the surface of the PAN precursor to obtain a nano modified PAN precursor with a target structure, and carbonizing the obtained modified PAN precursor to obtain the carbon fiber with the surface implanted with the nano structure.

Description

TECHNICAL FIELD

[0001] The application relates to a preparation method of surface-implanted nano-modified carbon fibers based on PAN precursors and belongs to the technical field of nanomaterials. BACKGROUND

[0002] Carbon fibers are a typical representative of high-performance fibers and are widely used in the fields of aerospace, automobiles, chemical industry and the like. At present, polyacrylonitrile-based carbon fibers, pitch-based carbon fibers and viscose-based carbon fibers are mainly used in the industrial production of carbon fibers, and the PAN-based carbon fibers prepared by taking PAN as a precursor account for more than 90% of the share of the carbon fiber market due to low raw material cost, simple process and excellent performance.

[0003] In recent years, researches on carbon fiber modification technologies are quite active. Carbon nanotubes have been widely applied in the preparation of carbon fibers due to their excellent physical and chemical properties as a new type of carbon material.

[0004] Plasma technology is a technology for processing materials by using a partial ionized plasma generated by a plasma generator. The plasma has properties different from the solid state, liquid state and gaseous state of matter and is a complex mixture composed of free electrons, positive and negative ions, free radicals, photons and excited molecules and is considered as the fourth aggregation state of matter.

[0005] Patent CN201910586775.4 discloses a preparation process of carbon fibers embedded with carbon nanotubes. The carbon fiber precursor with static electricity is adsorbed with gas-phase dispersed carbon nanotubes before solidification, so that a small amount of carbon nanotubes is used to treat the surface of the carbon fiber, and a part of the carbon nanotubes is embedded in the carbon fiber and a part of the carbon nanotubes is exposed on the surface of the carbon fiber, thereby forming a surface structure beneficial to the enhancement of the bonding strength between the carbon fiber and the resin matrix.

[0006] However, according to the disclosed technology, the preparation process of the technology utilizes the electrostatic adhesion of carbon nanotubes on the surface of the carbon fiber. However, due to the smooth surface of the carbon fiber, the carbon nanotubes are difficult to be deeply embedded in the carbon fiber in the form of electrostatic adsorption to form an effective composite structure, so that the interface bonding strength of the carbon fiber composite material is insufficient and the electrical performance is limited. SUMMARY

[0007] In order to solve the above problems, the application provides a preparation method of surface-implanted nano-modified carbon fibers based on PAN precursors.

[0008] 1. A discharge electrode is prepared by uniformly mixing the nano-material to be implanted, a dispersion medium and a dissolving medium, and a plasma discharge method is used to disperse the electrode in gas phase to obtain nano-particles dispersed in gas phase.

[0009] 2. The nanoparticles obtained in step 1 are transferred to the surface of the PAN precursor to be modified by natural spraying or guided spraying method;

[0010] 3. The PAN precursor receiving the nanoparticles is placed for a time period τ1, so that the proportion of the dispersion working medium and the dissolving working medium carried on the surface of the nanoparticles changes, and specifically the ability of the changed mixture of the dispersion working medium and the dissolving working medium to dissolve PAN changes;

[0011] 4. The time period τ1 is set so that the dispersion working medium and the dissolving working medium vaporize away from the surface of the PAN precursor, and the nanomodified PAN precursor with the desired structure is obtained;

[0012] 5. The modified PAN precursor obtained in step 4 is carbonized according to the carbonization process of carbon fiber, and the carbon fiber with the surface-implanted nanostructure is obtained;

[0013] 6. The dispersion working medium is a material that can vaporize and change phase at high temperature without decomposition, such as water;

[0014] 7. The dissolving working medium is a liquid material that is soluble in the dispersion working medium and can dissolve PAN, such as dimethyl sulfoxide;

[0015] 8. The role of the dispersion working medium in step 1 is to vaporize and change phase rapidly during plasma discharge, and the resulting body motion causes the nanoparticles contained therein to generate dispersion force to achieve the effect of dispersing nanoparticles. At the same time, the boiling point of the dispersion working medium needs to be lower than that of the dissolving working medium, and the heat absorption of the vaporization of the dispersion working medium in the high-temperature environment to a certain extent protects the nanoparticles and the dissolving working medium. The mass proportion of the dispersion working medium in the mixture is 5%-90%;

[0016] 9. The role of the dissolving working medium in step 1 is to adhere to the surface of the nanometer gas-phase dispersed particles. After the nanoparticles contact the PAN fiber, the PAN material in the local vicinity of the dissolved nanoparticles forms a viscous solution that embeds the nanoparticles in whole or in part, allowing the nanoparticles to enter the interior of the PAN precursor surface. The dissolving working medium should have high temperature resistance on the basis of satisfying step 7, and the mass proportion of the dissolving working medium in the mixture is 5%-40%;

[0017] 10. Considering the connectivity and micro strength of the discharge electrode in step 1, the proportion of the mixture of the dispersion working medium and the dissolving working medium in the discharge electrode in step 1 is not more than 60%:

[0018] 11. The determination method of the time period τ1 in step 3 is to make the evaporation amount of the dispersion working medium greater than that of the dissolving working medium by natural placement or heating method, so that the composition of the mixture of the dispersion working medium and the dissolving working medium carried on the surface of the nanoparticles changes, the content of the dissolving working medium increases, and the solubility of the mixture to PAN is not less than 15%;

[0019] 12、The determination of the placement duration τ2 in step 4 is that, after the placement duration τ1 in step 3, the mixture of the dispersed working medium and the dissolved working medium is evaporated to reduce the mass remaining on the PAN precursor to within 10% of that at the time τ1;

[0020] The beneficial effects of the present application are that, by naturally spraying or guiding spraying of the mixture of the dispersed substance, the dissolved substance and the nanomaterial to the surface of the PAN precursor, the preparation of the surface-implanted nanomodified carbon fiber based on the PAN precursor is realized. The rapid phase change vaporization of the dispersed substance in the plasma discharge process generates the motion of the increased body to disperse the nanoparticles, so that the nanoparticles are more uniformly distributed in the implantation process. The dissolved substance can locally dissolve the PAN material in the vicinity of the nanoparticles to embed the produced viscous solution in all or part of the structure of the nanoparticles, so that the nanoparticles enter the inside of the surface of the PAN precursor to achieve the purpose of firmly implanting the nanoparticles into the PAN precursor. The obtained nanomodified carbon fiber significantly improves the structural bonding ability between the carbon fiber and the resin, enhances the mechanical, electrical and chemical properties of the carbon fiber composite material and stabilizes the performance. The present application is based on the dry spraying and wet spinning process, and proposes to spray the mixture of the dissolved substance and the dispersed substance mixed with the nanoparticles and having solubility to the spun PAN precursor, to achieve the effect of implanting the carbon nanotube particles into the PAN precursor, and finally to obtain the surface-implanted nanomodified carbon fiber based on the PAN precursor through a series of processes such as pre-oxidation and carbonization. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 is the operation flow diagram of the preparation method of the surface-implanted nanomodified carbon fiber based on the PAN precursor of the present application. DETAILED DESCRIPTION

[0022] The technical solutions in the present application will be described clearly and completely below with reference to the drawings, and the following is known as one of the examples:

[0023] 1. The carbon nanotubes to be implanted are uniformly mixed with water and dimethyl sulfoxide to prepare a discharge electrode, and a plasma discharge method is used to disperse the electrode in gas phase to obtain the dispersed carbon nanotube particles in gas phase;

[0024] 2. The water vaporizes rapidly in the plasma discharge process, and the motion of the increased body generated thereby disperses the carbon nanotube particles contained therein by the dispersion force, and the water vaporization absorbs heat in the high-temperature dispersion environment to a certain extent, thereby protecting the carbon nanotube particles and dimethyl sulfoxide;

[0025] 3. Under the premise that the mixture of water and dimethyl sulfoxide accounts for 60% of the discharge electrode in step 1, the present application proposes that the mass ratio of water in the mixture is 55%, and the mass ratio of dimethyl sulfoxide in the mixture is 5%.

[0026] 4. The carbon nanotube particles obtained in step 1 are transferred to the surface of the PAN precursor by natural spraying method;

[0027] 5. Dimethyl sulfoxide is attached to the surface of the nanometer gas phase dispersed particles, and after the carbon nanotube particles contact the PAN fiber, the PAN material in the vicinity of the carbon nanotube particles is locally dissolved, and the viscous solution formed after the dissolution embeds the carbon nanotube particles in whole or in part, and the carbon nanotube particles enter the interior of the PAN precursor surface;

[0028] 6. The PAN precursor receiving the carbon nanotube particles is placed for 15 minutes, and through the natural placement method, the water evaporation amount is greater than the dimethyl sulfoxide evaporation amount due to the difference in boiling points, the water and dimethyl sulfoxide mixture components carried on the surface of the carbon nanotube change, the dimethyl sulfoxide content increases, and the mixture solubility to PAN is 15%;

[0029] 7. After the placement time of 10 minutes in step 3, the water and dimethyl sulfoxide mixture is evaporated to reduce the mass remaining on the PAN precursor to 5% of that after the placement time of 15 minutes, and the nanometer modified PAN precursor with the desired structure is obtained;

[0030] 8. The modified PAN precursor obtained in step 4 is carbonized according to the carbon fiber carbonization process to obtain the carbon fiber with the surface implanted nanometer structure.

Claims

1. The preparation method of surface implantation type nano-modified carbon fiber based on PAN precursor is to uniformly mix the nanomaterial to be implanted with the dispersing working medium and the dissolving working medium to form a discharge electrode, and use the plasma discharge method to disperse the electrode in the gas phase to obtain gas-phase dispersed nanoparticles. Nanoparticles are transferred to the surface of the PAN precursor fiber to be modified via natural spraying or guided spraying. The PAN precursor fiber receiving the nanoparticles is placed for a time τ1, which changes the ratio of the dispersing and dissolving working medium carried on the surface of the nanoparticles. Specifically, the changed mixture of dispersing and dissolving working medium has the ability to dissolve PAN. The placement time is τ2, which allows the dispersing and dissolving working medium to vaporize and leave the surface of the PAN precursor fiber, thus obtaining the nano-modified PAN precursor fiber with the desired structure. The modified PAN precursor fiber is carbonized according to the carbon fiber carbonization process to obtain carbon fiber with surface implanted nanostructures. The dispersing medium is a material that easily vaporizes and undergoes a phase change at high temperatures without decomposing. The dissolving medium is a liquid material that is soluble in both the dispersing medium and PAN. The dispersing medium's role is to disperse the nanoparticles through rapid phase change and vaporization during plasma discharge, generating a mass movement that disperses the nanoparticles. Simultaneously, the dispersing medium's boiling point must be lower than that of the dissolving medium. In high-temperature dispersion environments, the vaporization of the dispersing medium absorbs heat, which to some extent protects both the nanoparticles and the dissolving medium. Its mass percentage in the mixture is 5%-90%. The dissolving medium adheres to the surface of the nanoparticles in the gaseous phase. After the nanoparticles contact the PAN fibers, it locally dissolves the PAN material in the vicinity of the nanoparticles. The resulting viscous solution encapsulates all or part of the nanoparticle structure. To allow nanoparticles to penetrate the interior of the PAN precursor fiber surface, the dissolving medium should also have high temperature tolerance, and its mass percentage in the mixture should be 5%-40%. Considering the connectability and microscopic strength of the discharge electrode, the mixture of dispersing and dissolving medium should not exceed 60% of the discharge electrode. The placement time τ1 is determined by allowing the evaporation of the dispersing medium to exceed that of the dissolving medium through natural placement or heating, thereby altering the composition of the mixture of dispersing and dissolving medium carried on the nanoparticle surface, increasing the content of the dissolving medium, and ensuring that the solubility of the mixture in PAN is not less than 15%. The placement time τ2 is determined by allowing the mixture of dispersing and dissolving medium to evaporate after placement time τ1, reducing its mass remaining on the PAN precursor fiber to less than 10% of that at τ1.

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