CN113930867A - Surface modification method of carbon fiber - Google Patents
Surface modification method of carbon fiber Download PDFInfo
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- CN113930867A CN113930867A CN202111402136.1A CN202111402136A CN113930867A CN 113930867 A CN113930867 A CN 113930867A CN 202111402136 A CN202111402136 A CN 202111402136A CN 113930867 A CN113930867 A CN 113930867A
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- 229920000049 Carbon (fiber) Polymers 0.000 title claims abstract description 99
- 239000004917 carbon fiber Substances 0.000 title claims abstract description 99
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 title claims abstract description 95
- 238000002715 modification method Methods 0.000 title claims abstract description 13
- ATRRKUHOCOJYRX-UHFFFAOYSA-N Ammonium bicarbonate Chemical compound [NH4+].OC([O-])=O ATRRKUHOCOJYRX-UHFFFAOYSA-N 0.000 claims abstract description 43
- 229910000013 Ammonium bicarbonate Inorganic materials 0.000 claims abstract description 43
- 235000012538 ammonium bicarbonate Nutrition 0.000 claims abstract description 43
- 239000001099 ammonium carbonate Substances 0.000 claims abstract description 43
- 239000002243 precursor Substances 0.000 claims abstract description 30
- 239000000047 product Substances 0.000 claims abstract description 27
- 238000000034 method Methods 0.000 claims abstract description 26
- 239000013067 intermediate product Substances 0.000 claims abstract description 15
- 238000003682 fluorination reaction Methods 0.000 claims abstract description 13
- 239000003792 electrolyte Substances 0.000 claims abstract description 11
- 238000003487 electrochemical reaction Methods 0.000 claims abstract description 9
- 238000010000 carbonizing Methods 0.000 claims abstract description 7
- 238000003763 carbonization Methods 0.000 claims description 47
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 claims description 38
- 238000007254 oxidation reaction Methods 0.000 claims description 23
- 230000003647 oxidation Effects 0.000 claims description 20
- 238000001035 drying Methods 0.000 claims description 18
- 239000000243 solution Substances 0.000 claims description 18
- 238000005470 impregnation Methods 0.000 claims description 11
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 11
- 238000012986 modification Methods 0.000 claims description 9
- 230000004048 modification Effects 0.000 claims description 9
- 238000004513 sizing Methods 0.000 claims description 9
- 238000005406 washing Methods 0.000 claims description 9
- 238000002791 soaking Methods 0.000 claims description 7
- 239000000203 mixture Substances 0.000 claims description 4
- 239000008151 electrolyte solution Substances 0.000 claims description 3
- 239000002131 composite material Substances 0.000 abstract description 9
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 abstract description 7
- 229910052799 carbon Inorganic materials 0.000 abstract description 6
- 125000000524 functional group Chemical group 0.000 abstract description 5
- 229920005989 resin Polymers 0.000 abstract description 5
- 239000011347 resin Substances 0.000 abstract description 5
- 238000005868 electrolysis reaction Methods 0.000 abstract description 4
- 239000003795 chemical substances by application Substances 0.000 abstract description 3
- 230000008595 infiltration Effects 0.000 abstract description 3
- 238000001764 infiltration Methods 0.000 abstract description 3
- 239000000835 fiber Substances 0.000 description 48
- 229920002239 polyacrylonitrile Polymers 0.000 description 36
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 28
- 238000010438 heat treatment Methods 0.000 description 15
- 229910052757 nitrogen Inorganic materials 0.000 description 15
- 238000002166 wet spinning Methods 0.000 description 8
- 125000003636 chemical group Chemical group 0.000 description 7
- 230000014759 maintenance of location Effects 0.000 description 7
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 6
- 238000005096 rolling process Methods 0.000 description 6
- 229910052710 silicon Inorganic materials 0.000 description 6
- 239000010703 silicon Substances 0.000 description 6
- 230000000052 comparative effect Effects 0.000 description 4
- 239000012535 impurity Substances 0.000 description 3
- 239000003921 oil Substances 0.000 description 3
- 230000009286 beneficial effect Effects 0.000 description 2
- 230000007613 environmental effect Effects 0.000 description 2
- 230000005477 standard model Effects 0.000 description 2
- 229920002430 Fibre-reinforced plastic Polymers 0.000 description 1
- 238000010306 acid treatment Methods 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 238000007598 dipping method Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000007717 exclusion Effects 0.000 description 1
- 239000011151 fibre-reinforced plastic Substances 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 230000003472 neutralizing effect Effects 0.000 description 1
- 238000011056 performance test Methods 0.000 description 1
- -1 polysiloxane Polymers 0.000 description 1
- 229920001296 polysiloxane Polymers 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 230000002787 reinforcement Effects 0.000 description 1
- 238000010008 shearing Methods 0.000 description 1
- 230000035939 shock Effects 0.000 description 1
- 238000009987 spinning Methods 0.000 description 1
- 238000004381 surface treatment Methods 0.000 description 1
- 238000010998 test method Methods 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- 238000009736 wetting Methods 0.000 description 1
Classifications
-
- D—TEXTILES; PAPER
- D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
- D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
- D01F9/00—Artificial filaments or the like of other substances; Manufacture thereof; Apparatus specially adapted for the manufacture of carbon filaments
- D01F9/08—Artificial filaments or the like of other substances; Manufacture thereof; Apparatus specially adapted for the manufacture of carbon filaments of inorganic material
- D01F9/12—Carbon filaments; Apparatus specially adapted for the manufacture thereof
- D01F9/14—Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments
- D01F9/20—Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments from polyaddition, polycondensation or polymerisation products
- D01F9/21—Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments from polyaddition, polycondensation or polymerisation products from macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds
- D01F9/22—Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments from polyaddition, polycondensation or polymerisation products from macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds from polyacrylonitriles
-
- D—TEXTILES; PAPER
- D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
- D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
- D01F11/00—Chemical after-treatment of artificial filaments or the like during manufacture
- D01F11/10—Chemical after-treatment of artificial filaments or the like during manufacture of carbon
- D01F11/16—Chemical after-treatment of artificial filaments or the like during manufacture of carbon by physicochemical methods
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- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- General Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Textile Engineering (AREA)
- Chemical Or Physical Treatment Of Fibers (AREA)
- Inorganic Fibers (AREA)
Abstract
The invention discloses a surface modification method of carbon fibers, which comprises the following steps: carbonizing carbon fiber precursors to obtain carbonized products; carrying out fluorination treatment on the carbonized product to obtain an intermediate product; taking the intermediate product as an anode and ammonium bicarbonate as electrolyte to carry out electrochemical reaction, and then obtaining a pre-product; the invention can effectively clean tar on the surface of the carbon fiber by carrying out fluorination treatment on the carbon fiber precursor without changing a precursor oil agent system, and the carbon amorphous area on the surface of the carbon fiber can be etched in the fluorination process, so that secondary bonds are increased, and the interface performance of the composite material is enhanced; polar functional groups are introduced into the surface of the carbon fiber through ammonium bicarbonate electrolysis treatment, so that the surface free energy of the carbon fiber is increased, the infiltration performance of the surface of the carbon fiber and resin is improved, and the interlaminar shear strength of the carbon fiber composite material is improved.
Description
Technical Field
The invention relates to the technical field of carbon fiber preparation, in particular to a surface modification method of carbon fibers.
Background
As is well known, Polyacrylonitrile (PAN) carbon fibers are classified according to their mechanical properties, and generally classified into four categories, i.e., a high-strength standard model, a high-strength medium model, a high model, and a high-strength high model. The high-strength medium-model carbon fiber has the characteristics of light weight, high strength, high modulus and the like, also has the characteristics of high heat conduction, high electric conduction, good dimensional stability, good fatigue performance, good shock resistance and the like, has outstanding environmental alternation resistance and strong environmental adaptability, can be used as a reinforcement to prepare various structural and functional composite materials with high rigidity and high dimensional stability, and is widely applied to the fields of aerospace, aviation, high-end sports leisure and the like.
In China, a spinning oil agent used in the production and processing process of Polyacrylonitrile (PAN) carbon fiber generally takes functional group modified polysiloxane as a main component, and the produced Polyacrylonitrile (PAN) carbon fiber has certain ash content, so that the performance of the carbon fiber body is influenced to a certain extent when the Polyacrylonitrile (PAN) carbon fiber is modified.
Therefore, it is necessary to provide a method for modifying the surface of carbon fibers to solve the above problems.
The information disclosed in this background section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.
Disclosure of Invention
The invention aims to provide a surface modification method of carbon fibers, which can enhance the interface performance of the carbon fibers, increase the surface free energy of the carbon fibers and improve the interlaminar shear strength of a carbon fiber composite material.
In order to achieve the above object, an embodiment of the present invention provides a surface modification method of a carbon fiber, including the steps of: carbonizing the PAN precursor to obtain a carbonized product; carrying out fluorination treatment on the carbonized product to obtain an intermediate product; taking the intermediate product as an anode and ammonium bicarbonate as electrolyte to carry out electrochemical reaction, and then obtaining a pre-product; and carrying out post-treatment on the pre-product to obtain the modified carbon fiber.
In one or more embodiments of the present invention, the carbonizing the PAN filaments includes: the PAN protofilament is subjected to pre-oxidation treatment to obtain a pre-oxidation product, and then the pre-oxidation product is subjected to low-temperature carbonization treatment and high-temperature carbonization treatment in sequence.
In one or more embodiments of the present invention, the conditions for subjecting the PAN filaments to the pre-oxidation treatment include: and (3) performing oxidation reaction for 75-85 min at the temperature of 200-260 ℃ by adopting a 6-stage gradient temperature rise mode.
In one or more embodiments of the present invention, the conditions of the low temperature carbonization treatment include: and carrying out low-temperature carbonization treatment for 1.5-2.5 min at a draft ratio of 3-4% and a temperature of 400-750 ℃ by adopting a 6-section gradient temperature rise mode.
In one or more embodiments of the present invention, the conditions of the high temperature carbonization process include: under the condition of a draw ratio of-3% to-4%, and at the temperature of 1000-1600 ℃, carrying out 7-section gradient temperature rise high-temperature carbonization treatment for 1.5-2.5 min.
In one or more embodiments of the present invention, the fluorination treatment conditions include: immersing in hydrofluoric acid solution with pH 2-3 for 30-40 s.
In one or more embodiments of the present invention, before the electrochemically reacting the intermediate product, the surface modification method further includes: and (4) carrying out ammonium bicarbonate impregnation treatment on the intermediate product.
In one or more embodiments of the present invention, the conditions of the ammonium bicarbonate impregnation treatment include: soaking the mixture in 2-8 wt% ammonium bicarbonate solution for 10-15 s.
In one or more embodiments of the invention, the conditions of the electrochemical reaction include: taking 2-8 wt% ammonium bicarbonate as electrolyte solution, the temperature is 20-40 ℃, and the time is 5-25 s.
In one or more embodiments of the invention, the step of post-treating the pre-product comprises: and sequentially carrying out water washing, drying, sizing and re-drying on the pre-product.
Compared with the prior art, according to the surface modification method of the carbon fiber, the carbon fiber precursor is subjected to fluorination treatment, so that tar on the surface of the carbon fiber can be effectively cleaned under the condition that a precursor oil agent system is not changed, a carbon amorphous area on the surface of the fiber can be etched in the fluorination process, secondary bonds are increased, and the interface performance of the composite material is enhanced; polar functional groups are introduced into the surface of the carbon fiber through ammonium bicarbonate electrolysis treatment, so that the surface free energy of the carbon fiber is increased, the infiltration performance of the surface of the carbon fiber and resin is improved, the interlaminar shear strength of the carbon fiber composite material is improved, and the method has good guiding significance for the application of the carbon fiber in high-end fields such as aerospace and the like.
Detailed Description
The following detailed description of specific embodiments of the invention is provided, but it should be understood that the scope of the invention is not limited to the specific embodiments.
Throughout the specification and claims, unless explicitly stated otherwise, the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element or component but not the exclusion of any other element or component.
Compared with the high-strength T300-grade carbon fiber, the high-strength medium-model T800S-grade carbon fiber has the advantages of high inertia state on the surface, smooth surface and low mechanical engagement effect with resin. Therefore, there are problems of weak tensile strength, small tensile modulus, high ash content, and low interlaminar shear strength.
A surface modification method of a carbon fiber according to a preferred embodiment of the present invention includes the steps of:
and S1, carbonizing the carbon fiber precursor to obtain a carbonized product.
In a specific embodiment, the carbon fiber precursor can be 12K Polyacrylonitrile (PAN) precursor prepared by adopting a dry-jet wet spinning method.
Wherein the carbonization treatment comprises: the method comprises the steps of carrying out preoxidation treatment on carbon fiber precursors to obtain preoxidation products, and then sequentially carrying out low-temperature carbonization treatment and high-temperature carbonization treatment on the preoxidation products.
In one embodiment, the pre-oxidation treatment comprises the following steps: under the condition that the temperature is 200-260 ℃, a 6-section gradient heating mode is adopted, and then oxidation reaction is carried out for 75-85 min. Wherein the temperature is 200-260 ℃ when the temperature is increased from 200 ℃ to 260 ℃.
In one embodiment, the low-temperature carbonization process comprises the following steps: carbonizing at 400-750 deg.c for 1.5-2.5 min under 3-4% drafting ratio. Wherein, the draft ratio of 3% to 4% can be understood as increasing the force of drawing the carbon fiber by 3% to 4% in length. Wherein, at a temperature of 400 ℃ to 750 ℃ means that the temperature is increased from 400 ℃ to 750 ℃.
In one embodiment, the warm carbonization process comprises: under the condition of a draft ratio of-3 to-4 percent and at the temperature of 1000-1600 ℃, carrying out 7-section gradient temperature rise high-temperature carbonization treatment for 1.5-2.5 min. Wherein a draft ratio of-3 to-4% is understood to reduce the force of drawing the carbon fiber to shorten the length of the carbon fiber by 3 to 4%. At 1000 ℃ to 1600 ℃ is meant an increase from 1000 ℃ to 1600 ℃.
It should be noted that O, H, N elements can be removed by carbonization treatment, so that carbon elements are enriched to generate a hexagonal carbon network plane, and finally a disordered-layer graphite structure of the carbon fiber is generated, so that the carbon fiber has excellent mechanical properties.
S2, fluorinating the carbonized product to obtain an intermediate product.
In one embodiment, the fluorination treatment comprises the following steps: immersing in an aqueous solution of hydrofluoric acid having a pH of 2 to 3 for 30 to 40 seconds. The bonding tar on the carbon fiber can be obviously removed by soaking the carbon fiber with hydrofluoric acid, so that the ash content of the carbon fiber is reduced, and meanwhile, the carbon amorphous area on the surface of the fiber is etched in the fluorination process, so that the interlaminar shearing performance of the carbon fiber is improved. Wherein, the water can be washed by water after being soaked by hydrofluoric acid.
And S3, taking the intermediate product as an anode and taking ammonium bicarbonate as electrolyte to perform electrochemical reaction, and then obtaining a pre-product.
In one embodiment, the intermediate product may be further subjected to an ammonium bicarbonate impregnation treatment prior to the electrochemical reaction. Wherein, the concrete steps of the ammonium bicarbonate dipping treatment are as follows: soaking the carbon fiber in 2-8 wt% ammonium bicarbonate solution for 10-15 s, and neutralizing the residual hydrofluoric acid soaking solution to prevent impurities from entering an ammonium bicarbonate electrolytic bath and reduce the concentration of impurity components on the surface of the carbon fiber.
In one embodiment, the electrochemical reaction comprises the following steps: taking the intermediate product as an anode, placing the intermediate product in an electrolyte solution of 2-8 wt% ammonium bicarbonate, and electrifying for 5-25 s at the temperature of 20-40 ℃, wherein the electrified current density can be 0.2-0.4A/beam.
It should be noted that, after the electrolytic treatment of ammonium bicarbonate, polar functional groups are introduced to the surface of the carbon fiber, so that the surface free energy of the carbon fiber is increased, the wetting property of the surface of the carbon fiber and resin is improved, and the interlaminar shear strength of the carbon fiber composite material is improved.
And S4, carrying out post-treatment on the pre-product to obtain the modified carbon fiber.
In one embodiment, the step of post-treating the pre-product comprises: and sequentially carrying out water washing, drying, sizing and re-drying on the pre-product. The final modified carbon fiber can be obtained.
The following will describe the beneficial effects of the modified carbon fiber obtained by the method for surface modification of carbon fiber according to the present invention with reference to specific examples.
In the case of the example 1, the following examples are given,
(1) PAN precursor preoxidation
Selecting 12K PAN precursor produced by Wehai expanded fiber Limited company through wet spinning, and in an air medium, adopting a 6-section gradient heating mode, wherein the pre-oxidation starting temperature is 200 ℃, the termination temperature is 260 ℃, the retention time is 80min, and the obtained density is 1.35g/cm3The pre-oxidized fiber of (1).
(2) Low temperature carbonization
And carrying out low-temperature carbonization on the obtained pre-oxidized fiber for 2.0min at the initial temperature of 400 ℃ and the final temperature of 750 ℃ under the protection of nitrogen and at the temperature of 6-section gradient heating, and applying 3% drafting.
(3) High temperature carbonization
And (3) under the protection of nitrogen, treating the obtained low-temperature carbonized fiber for 2.0min by adopting a 7-section gradient temperature rise mode, wherein the high-temperature carbonization starting temperature is 1000 ℃, and the highest temperature is 1600 ℃, and applying-3.0% drafting.
(4) Hydrofluoric acid impregnation
The obtained high-temperature carbonized fiber is treated by hydrofluoric acid solution with pH of 3 at 25 ℃ for 30s to remove silicon element on the surface of the carbon fiber, and then is washed by water for 20 s.
(5) Electrolytic anodic oxidation of ammonium bicarbonate
The obtained fiber is soaked in 5 wt% ammonium bicarbonate solution for 11s, and then treated in 5 wt% ammonium bicarbonate electrolyte at 25 deg.C for 15s to increase surface active chemical groups.
(6) Post-treatment
And washing, drying, sizing, drying and rolling the obtained fiber to obtain the 12K PAN-based high-strength carbon fiber with the diameter of 5.0 mu m.
In the case of the example 2, the following examples are given,
(1) PAN precursor preoxidation
Selecting 12K PAN precursor produced by Wehai expanded fiber Limited company through wet spinning, and in an air medium, adopting a 6-section gradient heating mode, wherein the pre-oxidation starting temperature is 200 ℃, the termination temperature is 260 ℃, the retention time is 80min, and the obtained density is 1.35g/cm3The pre-oxidized fiber of (1).
(2) Low temperature carbonization
And carrying out low-temperature carbonization on the obtained pre-oxidized fiber for 2.0min at the initial temperature of 400 ℃ and the final temperature of 750 ℃ under the protection of nitrogen and at the temperature of 6-section gradient heating, and applying 3.2% drafting.
(3) High temperature carbonization
And (3) under the protection of nitrogen, treating the obtained low-temperature carbonized fiber for 2min by adopting a 7-section gradient temperature rise mode, wherein the high-temperature carbonization starting temperature is 1000 ℃, and the highest temperature is 1600 ℃, and applying-3.1% drafting.
(4) Hydrofluoric acid impregnation
The obtained high-temperature carbonized fiber is treated by hydrofluoric acid solution with pH 2 at 25 ℃ for 32s to remove silicon element on the surface of the carbon fiber, and then is washed by water for 20 s.
(5) Electrolytic anodic oxidation treatment of ammonium bicarbonate
The obtained fiber is soaked in ammonium bicarbonate solution with the concentration of 2 wt% for 15s, and then is treated in ammonium bicarbonate electrolyte with the concentration of 2 wt% at 40 ℃ for 25s to increase surface active chemical groups.
(6) Post-treatment
And washing, drying, sizing, drying and rolling the obtained fiber to obtain the 12K PAN-based high-strength carbon fiber with the diameter of 5.0 mu m.
In the case of the example 3, the following examples are given,
(1) PAN precursor preoxidation
Selecting 12K PAN precursor produced by Wehai expanded fiber Limited company through wet spinning, and in an air medium, adopting a 6-section gradient heating mode, wherein the pre-oxidation starting temperature is 200 ℃, the termination temperature is 260 ℃, the retention time is 83min, and the obtained density is 1.35g/cm3The pre-oxidized fiber of (1).
(2) Low temperature carbonization
And carrying out low-temperature carbonization on the obtained pre-oxidized fiber for 2.5min at the initial temperature of 400 ℃ and the final temperature of 750 ℃ under the protection of nitrogen and at the temperature of 6-section gradient heating, and applying 4% drafting.
(3) High temperature carbonization
And (3) under the protection of nitrogen, treating the obtained low-temperature carbonized fiber for 2.5min by adopting a 7-section gradient temperature rise mode, wherein the high-temperature carbonization starting temperature is 1000 ℃, and the highest temperature is 1600 ℃, and applying-4% drafting.
(4) Hydrofluoric acid impregnation
The obtained high-temperature carbonized fiber is treated by hydrofluoric acid solution with pH of 3 at 25 ℃ for 40s to remove silicon element on the surface of the carbon fiber, and then is washed by water for 20 s.
(5) Electrolytic anodic oxidation treatment of ammonium bicarbonate
The obtained fiber is soaked in ammonium bicarbonate solution with the concentration of 5 wt% for 14s, and then treated in ammonium bicarbonate electrolyte with the concentration of 8 wt% for 15s, so that surface active chemical groups are increased.
A12K PAN-based high-strength carbon fiber having a diameter of 5.0 μm was obtained.
In the case of the example 4, the following examples are given,
(1) PAN precursor preoxidation
Selecting 12K PAN precursor produced by Wehai expanded fiber Limited company through wet spinning, and in an air medium, adopting a 6-section gradient heating mode, wherein the pre-oxidation starting temperature is 200 ℃, the termination temperature is 260 ℃, the retention time is 75min, and the obtained density is 1.35g/cm3The pre-oxidized fiber of (1).
(2) Low temperature carbonization
And carrying out low-temperature carbonization on the obtained pre-oxidized fiber for 2.0min at the initial temperature of 400 ℃ and the final temperature of 750 ℃ under the protection of nitrogen and at the temperature of 6-section gradient heating, and applying 3.3% drafting.
(3) High temperature carbonization
And (3) under the protection of nitrogen, treating the obtained low-temperature carbonized fiber for 2min by adopting a 7-section gradient temperature rise mode, wherein the high-temperature carbonization starting temperature is 1000 ℃, and the highest temperature is 1600 ℃, and applying-3.3% drafting.
(4) Hydrofluoric acid impregnation
The obtained high-temperature carbonized fiber was treated with a hydrofluoric acid solution having a PH of 2.5 at 25 ℃ for 34 seconds to remove silicon on the surface of the carbon fiber, and then washed with water for 20 seconds.
(5) Electrolytic anodic oxidation treatment of ammonium bicarbonate
The obtained fiber is soaked in 5 wt% ammonium bicarbonate solution for 10s, and then treated in 5 wt% ammonium bicarbonate electrolyte at 20 deg.C for 5s to increase surface active chemical groups.
(6) Post-treatment
And washing, drying, sizing, drying and rolling the obtained fiber to obtain the 12K PAN-based high-strength carbon fiber with the diameter of 5.0 mu m.
In the case of the example 5, the following examples were conducted,
selecting 12K PAN precursor produced by Wehai expanded fiber Limited company through wet spinning, and in an air medium, adopting a 6-section gradient heating mode, wherein the pre-oxidation starting temperature is 200 ℃, the termination temperature is 260 ℃, the retention time is 85min, and the obtained density is 1.35g/cm3The pre-oxidized fiber of (1).
(2) Low temperature carbonization
And carrying out low-temperature carbonization on the obtained pre-oxidized fiber for 1.5min at the initial temperature of 400 ℃ and the final temperature of 750 ℃ under the protection of nitrogen and at the temperature of 6-section gradient heating, and applying 3.2% drafting.
(3) High temperature carbonization
And (3) under the protection of nitrogen, treating the obtained low-temperature carbonized fiber for 1.5min by adopting a 7-section gradient temperature rise mode, wherein the high-temperature carbonization starting temperature is 1000 ℃, and the highest temperature is 1600 ℃, and applying-3.4% drafting.
(4) Hydrofluoric acid impregnation
The obtained high-temperature carbonized fiber is treated by hydrofluoric acid solution with pH of 3 at 25 ℃ for 35s to remove silicon element on the surface of the carbon fiber, and then is washed by water for 20 s.
(5) Electrolytic anodic oxidation treatment of ammonium bicarbonate
The obtained fiber is soaked in 8 wt% ammonium bicarbonate solution and then treated in 8 wt% ammonium bicarbonate electrolyte at 30 ℃ for 25s to increase surface active chemical groups.
(6) Post-treatment
And washing, drying, sizing, drying and rolling the obtained fiber to obtain the 12K PAN-based high-strength carbon fiber with the diameter of 5.0 mu m.
In the comparative example 1,
(1) PAN precursor preoxidation
Selecting 12K PAN precursor produced by Wehai expanded fiber Limited company through wet spinning, and in an air medium, adopting a 6-section gradient heating mode, wherein the pre-oxidation starting temperature is 200 ℃, the termination temperature is 260 ℃, the retention time is 80min, and the obtained density is 1.35g/cm3The pre-oxidized fiber of (1).
(2) Low temperature carbonization
And carrying out low-temperature carbonization on the obtained pre-oxidized fiber for 2.0min at the initial temperature of 400 ℃ and the final temperature of 750 ℃ under the protection of nitrogen and at the temperature of 6-section gradient heating, and applying 3% drafting.
(3) High temperature carbonization
And (3) under the protection of nitrogen, treating the obtained low-temperature carbonized fiber for 2min by adopting a 7-section gradient temperature rise mode, wherein the high-temperature carbonization starting temperature is 1000 ℃, and the highest temperature is 1600 ℃, and applying-3.0% drafting.
(4) Electrolytic anodic oxidation of ammonium bicarbonate
The surface active chemical groups are increased by treating the mixture in an ammonium bicarbonate electrolyte with the concentration of 5% for 15 s.
(5) Post-treatment
And washing, drying, sizing, drying and rolling the obtained fiber to obtain the 12K PAN-based high-strength carbon fiber with the diameter of 5.0 mu m.
In the comparative example, ammonium bicarbonate soaking is not needed, and the ammonium bicarbonate soaking is used for removing residual liquid on the surface of the carbon fiber after hydrofluoric acid treatment for reaction, so that impurities are prevented from being introduced into an ammonium bicarbonate electrolysis process.
In a comparative example 2,
(1) PAN precursor preoxidation
Selecting 12K PAN precursor produced by Wehai expanded fiber Limited company through wet spinning, and in an air medium, adopting a 6-section gradient heating mode, wherein the pre-oxidation starting temperature is 200 ℃, the termination temperature is 260 ℃, the retention time is 80min, and the obtained density is 1.35g/cm3The pre-oxidized fiber of (1).
(2) Low temperature carbonization
And carrying out low-temperature carbonization on the obtained pre-oxidized fiber for 2.0min at the initial temperature of 400 ℃ and the final temperature of 750 ℃ under the protection of nitrogen and at the temperature of 6-section gradient heating, and applying 3.1% drafting.
(3) High temperature carbonization
And (3) under the protection of nitrogen, treating the obtained low-temperature carbonized fiber for 2min by adopting a 7-section gradient temperature rise mode, wherein the high-temperature carbonization starting temperature is 1000 ℃, and the highest temperature is 1600 ℃, and applying-3.0% drafting.
(4) Hydrofluoric acid impregnation
The obtained high-temperature carbonized fiber is treated by hydrofluoric acid solution with pH of 3 at 25 ℃ for 30s to remove silicon element on the surface of the carbon fiber, and then is washed by water for 20 s.
(5) Electrolytic anodic oxidation of ammonium bicarbonate
The surface active chemical groups are increased by treating the mixture in an ammonium bicarbonate electrolyte with the concentration of 5% for 15 s.
(6) Post-treatment
And washing, drying, sizing, drying and rolling the obtained fiber to obtain the 12K PAN-based high-strength carbon fiber with the diameter of 5.0 mu m.
The tensile strength and the tensile modulus are tested according to polyacrylonitrile-based carbon fiber (GB/T26752-2020), and the interlaminar shear strength is tested according to the interlaminar shear strength test method of unidirectional fiber reinforced plastics (JC/T773-1982).
The test results are shown in table 1:
TABLE 1 concrete parameters of carbon fiber surface treatment and results of performance test in examples 1 to 5 and comparative examples 1 to 2
In the conventional modification treatment of 12K PAN precursor, the interlaminar shear strength of the carbon fiber of the modified high-strength medium model can be generally made to exceed 110MPa, but if it exceeds this value, it becomes extremely difficult to extract the interlaminar shear strength. The interlaminar shear strength of the modified carbon fiber obtained from example 1 in table 1 can reach 123MPa, and compared with the interlaminar shear strength of the modified high-strength medium-model carbon fiber obtained by a conventional method which is 110MPa, the interlaminar shear strength of the high-strength medium-model carbon fiber is improved by more than 10%. Therefore, the surface modification method of the carbon fiber can effectively improve the interlaminar shear strength to 110MPa and then remarkably improve the interlaminar shear strength.
It should be noted that the surface modification method of the carbon fiber of the present invention is mainly a surface modification method for the carbon fiber of the high-strength medium model, but can also improve the interlaminar shear strength for the carbon fiber of other high-strength standard models, high models and high-strength high models.
In conclusion, the beneficial effects of the invention are as follows: by carrying out fluorination treatment on carbon fiber precursors, tar on the surfaces of the carbon fibers can be effectively cleaned under the condition of not changing a precursor oil solution system, carbon amorphous areas on the surfaces of the fibers can be etched in the fluorination process, secondary bonds are increased, and the interface performance of the composite material is enhanced; polar functional groups are introduced into the surface of the carbon fiber through ammonium bicarbonate electrolysis treatment, so that the surface free energy of the carbon fiber is increased, the infiltration performance of the surface of the carbon fiber and resin is improved, the interlaminar shear strength of the carbon fiber composite material is improved, and the method has good guiding significance for the application of the carbon fiber in high-end fields such as aerospace and the like.
The foregoing descriptions of specific exemplary embodiments of the present invention have been presented for purposes of illustration and description. It is not intended to limit the invention to the precise form disclosed, and obviously many modifications and variations are possible in light of the above teaching. The exemplary embodiments were chosen and described in order to explain certain principles of the invention and its practical application to enable one skilled in the art to make and use various exemplary embodiments of the invention and various alternatives and modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims and their equivalents.
Claims (10)
1. A surface modification method of carbon fiber is characterized by comprising the following steps:
carbonizing carbon fiber precursors to obtain carbonized products;
carrying out fluorination treatment on the carbonized product to obtain an intermediate product;
taking the intermediate product as an anode and ammonium bicarbonate as electrolyte to carry out electrochemical reaction, and then obtaining a pre-product;
and carrying out post-treatment on the pre-product to obtain the modified carbon fiber.
2. The method for modifying the surface of carbon fiber according to claim 1, wherein the carbonizing treatment of the carbon fiber precursor comprises: the method comprises the steps of carrying out preoxidation treatment on carbon fiber precursors to obtain preoxidation products, and then sequentially carrying out low-temperature carbonization treatment and high-temperature carbonization treatment on the preoxidation products.
3. The method for modifying the surface of carbon fiber according to claim 2, wherein the conditions for subjecting the carbon fiber precursor to the pre-oxidation treatment include: and (3) performing oxidation reaction for 75-85 min at the temperature of 200-260 ℃ by adopting a 6-stage gradient temperature rise mode.
4. The method for surface modification of carbon fiber according to claim 2, wherein the conditions of the low-temperature carbonization treatment include: under the condition of a draft ratio of 3-4%, carrying out 6-section gradient low-temperature carbonization treatment at 400-750 ℃ for 1.5-2.5 min.
5. The method for surface modification of carbon fiber according to claim 2, wherein the conditions of the high-temperature carbonization treatment include: under the condition of a draw ratio of-3% to-4%, and at the temperature of 1000-1600 ℃, carrying out 7-section gradient temperature rise high-temperature carbonization treatment for 1.5-2.5 min.
6. The method for surface modification of carbon fiber according to claim 1, wherein the fluorination treatment conditions include: immersing in hydrofluoric acid solution with pH 2-3 for 30-40 s.
7. The method for modifying the surface of carbon fibers according to claim 1, wherein before subjecting the intermediate product to the electrochemical reaction, the method for modifying the surface further comprises: and (4) carrying out ammonium bicarbonate impregnation treatment on the intermediate product.
8. The method for surface modification of carbon fiber according to claim 7, wherein the conditions of the ammonium bicarbonate impregnation treatment include: soaking the mixture in 2-8 wt% ammonium bicarbonate solution for 10-15 s.
9. The method for surface modification of carbon fiber according to claim 1, wherein the conditions of the electrochemical reaction include: taking 2-8 wt% ammonium bicarbonate as electrolyte solution, the temperature is 20-40 ℃, and the time is 5-25 s.
10. The method for modifying the surface of carbon fibers according to claim 1, wherein the step of post-treating the pre-product comprises: and sequentially carrying out water washing, drying, sizing and re-drying on the pre-product.
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