CN105714412A - Preparation method of electrospun polyacrylonitrile pre-oxidized fiber and carbon fiber - Google Patents

Abstract

The invention discloses a method for preparing electrospun polyacrylonitrile oxidized fiber and carbon fiber, belonging to the technical field of carbon fiber preparation. According to the characteristics of electrospun polyacrylonitrile fibers, the present invention controls the total time of pre-oxidation to be 10-30 minutes, and the temperature is controlled at 240-295°C to obtain electrospun polyacrylonitrile oxidized fibers; Carbonization treatment to prepare carbon fibers. The method can prepare electrospun polyacrylonitrile-based carbon fibers with excellent mechanical properties, and greatly improve the production efficiency of electrospun polyacrylonitrile oxidized fibers and carbon fibers.

Description

A kind of preparation method of electrospun polyacrylonitrile preoxygenated fiber and carbon fiber

technical field

The invention relates to a method for preparing electrospun polyacrylonitrile preoxygenated fibers and carbon fibers. Specifically, the electrospun polyacrylonitrile precursor prepared by the electrospinning method is pre-oxidized by a short-time high-temperature heat treatment method, and through a conventional carbonization process, the preparation of electrospun polyacrylonitrile-based carbon fibers with excellent mechanical properties is realized, and can be The invention relates to greatly improving the production efficiency of electrospun polyacrylonitrile oxidized fibers and carbon fibers, and belongs to the technical field of carbon fibers.

Background technique

Carbon fiber is an important composite material reinforcement fiber, which has a wide range of applications and application value. However, the further improvement of the mechanical properties of carbon fiber is currently at the bottleneck. Carbon fiber is a brittle material, and its mechanical properties are controlled by the number and distribution of internal defects. Carbon fiber has a size effect, which is reflected in the increase in the structure and mechanical properties of carbon fiber as the diameter decreases. This is due to the "inheritance" of defects in the carbon fiber precursors and the effect of the diameter of the precursors on the radial uniformity of the fibers during pre-oxidation. Therefore, effectively improving the structure of the precursor and reducing the diameter of the precursor is the key to further improving the mechanical properties of carbon fibers.

The electrospinning method is a continuous preparation method of submicron/nanofibers. The preparation of polyacrylonitrile fibers with a diameter of submicron or even nanometer by electrospinning has the advantages of ultra-fine diameter, perfect structure and few defects. These advantages are what researchers hope to achieve in traditional spinning methods. Therefore, electrospun polyacrylonitrile precursors have the potential to prepare high-performance carbon fibers.

But for electrospun polyacrylonitrile precursors, a targeted pre-oxidation process is very important, because electrospun polyacrylonitrile precursors are very different from traditional micron precursors in two important aspects that affect the pre-oxidation process. The big difference: (1) The diameter of the original filament is greatly reduced and (2) The degree of crystallinity and molecular chain orientation is greatly improved. However, the existing research has not paid enough attention to the pre-oxidation of electrospun polyacrylonitrile precursors. Most researchers still consider the pre-oxidation characteristics of traditional micron precursors, and some researchers are still using Subsequent heat treatment of the raw silk is carried out in a batch manner. Therefore, the potential of electrospinning polyacrylonitrile precursors is limited and the efficiency of the carbon fiber preparation process is also reduced.

Contents of the invention

The main purpose of the present invention is to provide a scientific and efficient pre-oxidation method for electrospun polyacrylonitrile fibers, and then prepare carbon fibers with excellent mechanical properties. According to the characteristics of electrospun polyacrylonitrile, rationally optimize the pre-oxidation process: increase the degree of cyclization of the fiber by increasing the pre-oxidation temperature; shorten the pre-oxidation time to control the density of the fiber, and avoid excessive structural defects in the fiber during the carbonization process Formation. Moreover, the short-term high-temperature pre-oxidation process of electrospun polyacrylonitrile really improves the production efficiency of the carbon fiber preparation process.

In order to achieve the above object, the technical scheme adopted by the present invention is as follows.

A method for preparing electrospun polyacrylonitrile pre-oxidized fibers, characterized in that electrospun polyacrylonitrile is used as a precursor, the total pre-oxidation time is controlled at 10-30 minutes, and the temperature is controlled at 240-295 ° C, specifically comprising the following steps : The electrospun acrylonitrile fiber is pre-oxidized continuously through a heat treatment furnace. Firstly, the residence time of the fiber in the temperature zone of 240-260°C is 5-15 minutes, and then the residence time of the fiber in the temperature zone of 270-295°C is 5 minutes. ~15min to prepare electrospun polyacrylonitrile oxidation fiber.

Further, the pre-oxidation process adopts 3 to 8 temperature zones;

Further, the controlled draft ratio in the temperature zone of 240～260℃ is -4～8%, and the controlled draft ratio in the temperature zone of 270～295℃ is -8～4%;

Further, the electrospun polyacrylonitrile fibers used may be acrylonitrile homopolymer fibers, or acrylonitrile copolymer fibers containing one or more comonomers with a mass fraction below 15%. Carboxyl group, amine group, amide group of cyclization reaction, and ester group which can improve spinning performance;

Further, the electrospun polyacrylonitrile fibers used may be non-woven fabrics/felts or unidirectional fiber bundles.

A method for preparing electrospun polyacrylonitrile-based carbon fibers, which is characterized in that electrospun polyacrylonitrile is used as a precursor, and firstly through pre-oxidation treatment with a total time of 10 to 30 minutes and a temperature of 240 to 295 ° C to prepare electrostatic Spun polyacrylonitrile oxidized fibers, and then carbonized to prepare electrospun polyacrylonitrile-based carbon fibers, specifically including the following steps:

(1) First, the electrospun polyacrylonitrile fiber is subjected to a low-temperature heat treatment for 5 to 15 minutes in a pre-oxidation furnace in a temperature zone of 240 to 260 ° C, and then carried out in a higher temperature zone of a temperature zone of 270 to 295 ° C for 5 to 15 minutes high-temperature heat treatment to produce electrospun polyacrylonitrile oxidized fibers; (2) further, conventional carbonization treatment is carried out on electrospun polyacrylonitrile oxidized fibers to prepare carbon fibers;

Further, the pre-oxidation process adopts 3 to 8 temperature zones;

Further, the controlled draft ratio in the temperature zone of 240～260℃ is -4～8%, and the controlled draft ratio in the temperature zone of 270～295℃ is -8～4%;

Further, the low-temperature carbonization temperature range is 300-900°C, and the time is: the high-temperature carbonization temperature range is 1100-1600°C; the time is:

Further, the electrospun polyacrylonitrile fibers used may be acrylonitrile homopolymer fibers, or acrylonitrile copolymer fibers containing one or more comonomers with a mass fraction below 15%. Carboxyl group, amine group, amide group of cyclization reaction, and ester group which can improve spinning performance;

The electrospun polyacrylonitrile fibers used can be non-woven/felt or unidirectional fiber bundles.

The above-mentioned electrospun polyacrylonitrile fibers can be acrylonitrile homopolymer fibers, or acrylonitrile copolymer fibers containing one or more comonomers with a mass fraction below 15%, and the comonomers include: itaconic acid, methacrylic acid Esters, acrylic acid, allyl chloride, alpha-chloropropene, methacrylic acid, methyl methacrylate, hydroxyalkylacrylonitrile, hydroxyalkylacrylic acid and its esters, acrylamide, methacrylamide, diacetonepropene amide, methacrylacetone; and electrospun polyacrylonitrile fibers can be in the form of non-woven/felt or unidirectional fiber bundles.

The effect of the present invention: the electrospun polyacrylonitrile oxidized fiber can be prepared by short-term high-temperature pre-oxidation, and the tensile strength of the prepared electrospun polyacrylonitrile-based carbon fiber is above 1.2GPa, and the tensile modulus is 195.0GPa above. Moreover, the method can greatly reduce the preparation time of the electrospun polyacrylonitrile oxidized fiber and the carbon fiber, thereby reducing the preparation cost.

detailed description

In the following specific examples, the same copolymerized acrylonitrile is used to carry out the electrospinning and post-treatment process under the same conditions, and the electrospun polyacrylonitrile precursor is prepared. First, a series of comprehensive analysis is made through DSC, infrared spectroscopy, elemental analysis and other testing means. Appropriate pre-oxidation process conditions.

Example 1

Make the electrospun polyacrylonitrile precursor pass through three pre-oxidation temperature zones successively in normal pressure and air medium, and the total time is 15 minutes. The reaction temperature in the first temperature zone is 260°C, the reaction time is set at 10 minutes, and 2% rigid stretching is added. The reaction temperature in the second temperature zone is 275° C., the reaction time is 5 minutes, and the stretching is 0. The reaction temperature in the third temperature zone is 285° C., the reaction time is 5 minutes, and the stretching is 0. Then carry out conventional carbonization treatment under nitrogen atmosphere: first go through the low-temperature carbonization process of 4 minutes in five temperature zones of 350, 400, 480, 550, and 700 ° C, (the overall time of low-temperature carbonization is 4 minutes, the following examples are the same) then add 5 % of the positive draft; and then after 1300 ℃ 6min high-temperature carbonization process, add 5% of the negative draft. The tensile strength of the electrospun polyacrylonitrile-based carbon fiber prepared by the above method is 1.14GPa, and the Young's modulus is 187.3GPa.

Example 2

Make the electrospun polyacrylonitrile precursor pass through three pre-oxidation temperature zones successively in normal pressure and air medium, and the total time is 15 minutes. The reaction temperature in the first temperature zone is 258° C., the reaction time is set at 5 minutes, and 2% positive stretching is added. The reaction temperature in the second temperature zone is 278° C., the reaction time is set at 5 minutes, and the stretching is 2% positive stretching. The reaction temperature in the third temperature zone is 288° C., the reaction time is 5 minutes, and the stretching is 0. Afterwards, conventional carbonization treatment is carried out under nitrogen atmosphere: first, it goes through 4 minutes of low-temperature carbonization process in five temperature zones of 350, 400, 480, 550, and 700 ° C, and then adds 5% positive drawing; During the high temperature carbonization process, 5% negative draft is added. The tensile strength of the electrospun polyacrylonitrile-based carbon fiber prepared by the above method is 1.28GPa, and the Young's modulus is 201.7GPa.

Example 3

Make the electrospun polyacrylonitrile precursors pass through four pre-oxidation temperature zones sequentially in normal pressure and air medium for a total time of 20 minutes. The reaction temperature in the first temperature zone is 240°C, the reaction time is set at 5 minutes, and 2% positive stretching is added. The reaction temperature in the second temperature zone is 260° C., the reaction time is set at 5 minutes, and the stretching is 2% positive stretching. The reaction temperature in the third temperature zone is 274° C., the reaction time is 5 minutes, and the stretching is 0. The reaction temperature in the fourth temperature zone is 284°C, the reaction time is 5 minutes, and the stretching is 0. After that, conventional carbonization treatment is carried out under nitrogen atmosphere: firstly, it goes through 4 minutes of low-temperature carbonization process in five temperature zones of 350, 400, 480, 550, and 700°C, and then adds 5% positive drawing; then passes through 6min of 1350°C During the high temperature carbonization process, 5% negative draft is added. The tensile strength of the electrospun polyacrylonitrile-based carbon fiber prepared by the above method is 1.32GPa, and the Young's modulus is 225.2GPa.

Example 4

Make the electrospun polyacrylonitrile precursors pass through four pre-oxidation temperature zones sequentially in normal pressure and air medium for a total time of 20 minutes. The reaction temperature in the first temperature zone is 245° C., the reaction time is set at 5 minutes, and 2% positive stretching is added. The reaction temperature in the second temperature zone is 258° C., the reaction time is set at 5 minutes, and the stretching is 2% positive stretching. The reaction temperature in the third temperature zone is 278° C., the reaction time is 5 minutes, and the stretching is 0. The reaction temperature in the fourth temperature zone is 282°C, the reaction time is 5 minutes, and the stretching is 0. After that, conventional carbonization treatment is carried out under nitrogen atmosphere: firstly, it goes through 4 minutes of low-temperature carbonization process in five temperature zones of 350, 400, 480, 550, and 700°C, and then adds 5% positive drawing; then passes through 6min of 1350°C During the high temperature carbonization process, 5% negative draft is added. The tensile strength of the electrospun polyacrylonitrile-based carbon fiber prepared by the above method is 1.36GPa, and the Young's modulus is 236.9GPa.

Example 5

Make the electrospun polyacrylonitrile precursors pass through four pre-oxidation temperature zones sequentially in normal pressure and air medium for a total time of 20 minutes. The reaction temperature in the first temperature zone is 245° C., the reaction time is set at 5 minutes, and 2% positive stretching is added. The reaction temperature in the second temperature zone is 258° C., the reaction time is set at 5 minutes, and the stretching is 2% positive stretching. The reaction temperature in the third temperature zone is 278° C., the reaction time is 5 minutes, and the stretching is -1.5%. The reaction temperature in the fourth temperature zone is 282°C, the reaction time is 5 minutes, and the draft is -1.5%. After that, conventional carbonization treatment is carried out under nitrogen atmosphere: firstly, it goes through 4 minutes of low-temperature carbonization process in five temperature zones of 350, 400, 480, 550, and 700°C, and then adds 5% positive drawing; then passes through 6min of 1350°C During the high temperature carbonization process, 5% negative draft is added. The tensile strength of the electrospun polyacrylonitrile-based carbon fiber prepared by the above method is 1.47GPa, and the Young's modulus is 242.2GPa.

Example 6

Make the electrospun polyacrylonitrile precursors pass through four pre-oxidation temperature zones sequentially in normal pressure and air medium for a total time of 20 minutes. The reaction temperature in the first temperature zone is 245° C., the reaction time is set at 5 minutes, and 2% positive stretching is added. The reaction temperature in the second temperature zone is 262° C., the reaction time is set at 5 minutes, and the drafting is 2% positive drafting. The reaction temperature in the third temperature zone is 278° C., the reaction time is 5 minutes, and the stretching is -1.5%. The reaction temperature in the fourth temperature zone is 284° C., the reaction time is 5 minutes, and the stretching is -2%. After that, conventional carbonization treatment is carried out under nitrogen atmosphere: firstly, it goes through 4 minutes of low-temperature carbonization process in five temperature zones of 350, 400, 480, 550, and 700°C, and then adds 5% positive drawing; then passes through 6min of 1350°C During the high temperature carbonization process, 5% negative draft is added. The tensile strength of the electrospun polyacrylonitrile-based carbon fiber prepared by the above method is 1.53GPa, and the Young's modulus is 222.2GPa.

Example 7

Make the electrospun polyacrylonitrile precursors pass through four pre-oxidation temperature zones sequentially in normal pressure and air medium for a total time of 20 minutes. The reaction temperature in the first temperature zone is 247° C., the reaction time is set at 5 minutes, and 4% positive stretching is added. The reaction temperature in the second temperature zone is 262° C., the reaction time is set at 5 minutes, and the stretching is 0% positive stretching. The reaction temperature in the third temperature zone is 278° C., the reaction time is 5 minutes, and the stretching is -1.5%. The reaction temperature in the fourth temperature zone is 284°C, the reaction time is set at 5 minutes, and the draft is -2.5%. After that, conventional carbonization treatment is carried out under nitrogen atmosphere: firstly, it goes through 4 minutes of low-temperature carbonization process in five temperature zones of 350, 400, 480, 550, and 700°C, and then adds 5% positive drawing; then passes through 6min of 1350°C During the high temperature carbonization process, 5% negative draft is added. The tensile strength of the electrospun polyacrylonitrile-based carbon fiber prepared by the above method is 1.77GPa, and the Young's modulus is 219.4GPa.

Comparative example

This embodiment adopts the pre-oxidation process of traditional micron polyacrylonitrile precursor. Make the electrospun polyacrylonitrile precursor pass through 4 pre-oxidation temperature zones successively in normal pressure and air medium, and the total time is 80. The reaction temperature in the first temperature zone is 210°C, the reaction time is set at 20 minutes, and 2% positive stretching is added. The reaction temperature in the second temperature zone is 230° C., the reaction time is set at 20 minutes, and the drafting is 2% positive drafting. The reaction temperature in the third temperature zone is 250° C., the reaction time is 20 minutes, and the stretching is 0. The reaction temperature in the fourth temperature zone is 270°C, the reaction time is 20min, and the stretching is 0. After that, conventional carbonization treatment is carried out under nitrogen atmosphere: firstly, it goes through 4 minutes of low-temperature carbonization process in five temperature zones of 350, 400, 480, 550, and 700°C, and then adds 5% positive drawing; then passes through 6min of 1350°C During the high temperature carbonization process, 5% negative draft is added. The tensile strength of the electrospun polyacrylonitrile-based carbon fiber prepared by the above method is 0.43GPa, and the Young's modulus is 53.2GPa.

Claims (10)

1. the preparation method of a Static Spinning polyacrylonitrile pre-oxidation fiber, it is characterised in that specifically include following steps:

Static Spinning Dralon is continued through heat-treatment furnace and carries out pre-oxidation, first making fiber time of staying in the warm area of 240～260 DEG C is 5～15min, and then to make in fiber the time of staying in 270～295 DEG C of warm areas be 5～15min, to produce Static Spinning oxidized polyacrylonitrile fiber.

2. according to the method for claim 1, it is characterised in that preoxidation process adopts 3～8 warm areas.

3., according to the method for claim 1, it is characterised in that it is-4～8% that 240～260 DEG C of warm areas control degree of draft, it is-8～4% that 270～295 DEG C of warm areas control degree of draft.

4. according to the method for claim 1, Static Spinning polyacrylonitrile fibre used is acrylonitrile homopolymerization fiber, or comprise the acrylonitrile compolymer fiber of the mass fraction one or more comonomers below 15%, comonomer comprises one or more in carboxyl, amido, amide groups or ester group.

5., according to the method for claim 1, Static Spinning polyacrylonitrile fibre used is non-woven fabrics/felt or unidirectional fiber bundle.

6. the preparation method of a Static Spinning polyacrylonitrile-based carbon fibre, it is characterised in that specifically include following steps:

(1) Static Spinning polyacrylonitrile fibre is first made to carry out the Low Temperature Heat Treatment of 5～15min in the pre-oxidation furnace of the warm area of 240～260 DEG C, and then in the district at higher temperature of 270～295 DEG C of warm areas, carry out the high-temperature heat treatment of 5～15min again, to produce Static Spinning oxidized polyacrylonitrile fiber；(2) and then, Static Spinning oxidized polyacrylonitrile fiber is carried out further carbonization process, prepares carbon fiber.

7. according to the method for claim 6, it is characterised in that preoxidation process adopts 3～8 warm areas.

8., according to the method for claim 6, it is characterised in that it is-4～8% that 240～260 DEG C of warm areas control degree of draft, it is-8～4% that 270～295 DEG C of warm areas control degree of draft.

9. according to the method for claim 6, Static Spinning polyacrylonitrile fibre used is acrylonitrile homopolymerization fiber, or comprise the acrylonitrile compolymer fiber of the mass fraction one or more comonomers below 15%, comonomer comprises one or more in carboxyl, amido, amide groups or ester group.

10., according to the method for claim 6, Static Spinning polyacrylonitrile fibre used can be non-woven fabrics/felt or unidirectional fiber bundle.