Polyacrylonitrile-based high-strength and high-modulus carbon fiber and preparation method thereof
The formation of elongated graphite microcrystalline structures by multi-stage gradient high-temperature drafting method solves the problem that carbon fibers are difficult to simultaneously improve tensile strength and modulus in the prior art, and achieves the preparation of carbon fibers of high strength and high modulus.
Patent Information
- Application Number
- CN202411251086.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-06
- Publication Date
- 2024-12-13
AI Technical Summary
The prior art is difficult to simultaneously improve the tensile strength and tensile modulus of carbon fibers. Although conventional graphitization treatment can improve the modulus, it is difficult to obtain high strength.
The polyacrylonitrile-based carbon fiber is treated by multi-stage gradient high-temperature drafting method. By performing first-stage, second-stage or third-stage high-temperature drafting in an inert atmosphere, the size of graphite microcrystals is gradually increased to form a slender structure and improve the carbon fibers. tensile strength and modulus.
The tensile strength of carbon fiber is 3.6GPa-7.7GPa and the tensile modulus of carbon fiber is 350GPa-700GPa, forming an elongated graphite microcrystalline structure, which significantly improves the mechanical properties of carbon fibers.
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Figure BDA0005032276070000051
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of carbon fiber, and in particular, relates to a polyacrylonitrile-based high-strength and high-modulus carbon fiber and a preparation method thereof. Background Art
[0002] Carbon fiber has the characteristics of high specific strength, high specific modulus, high temperature resistance, corrosion resistance, good electrical and thermal conductivity, etc., so it is widely used in aerospace, petroleum, chemical, textile, machinery and sports equipment. According to the performance characteristics of carbon fiber, carbon fiber can usually be divided into three categories: high-strength type, high-modulus and high-strength high-modulus. Among them, high-strength and high-modulus carbon fiber has become an indispensable key material in the aerospace field because of its high strength and high modulus characteristics.
[0003] The tensile mechanical properties of carbon fiber are determined by its graphite microcrystal structure. In order to obtain high modulus carbon fiber, the carbon fiber needs to be further graphitized at 1800-3000℃ to further grow the graphite microcrystals in the carbon fiber, thereby increasing the modulus of the carbon fiber. Conventional graphitization treatment causes the graphite microcrystals of carbon fiber to grow synchronously in all directions, which can effectively improve the modulus of the carbon fiber, but it is difficult to obtain high strength. Summary of the invention
[0004] The invention provides a polyacrylonitrile-based high-strength and high-modulus carbon fiber and a preparation method thereof. The carbon fiber has both high strength and high modulus.
[0005] A first aspect of the present invention provides a polyacrylonitrile-based high-strength and high-modulus carbon fiber, wherein the carbon fiber has a tensile strength of 3.6 GPa-7.7 GPa and a tensile modulus of 350 GPa-700 GPa.
[0006] Furthermore, the graphite crystallite size La in the carbon fiber parallel to the fiber axis direction is ∥ The graphite crystallite size La perpendicular to the fiber axis ⊥ Ratio ∥ / La ⊥ It is 1.5-2.5.
[0007] Furthermore, the La of the carbon fiber ∥ is 7nm-20nm; the La of the carbon fiber ⊥ 4nm-11nm.
[0008] A second aspect of the present invention provides a method for preparing polyacrylonitrile-based high-strength and high-modulus carbon fibers, the method comprising: subjecting the polyacrylonitrile-based carbon fibers to multi-stage gradient high-temperature drawing in an inert atmosphere.
[0009] Furthermore, the tensile strength of the polyacrylonitrile-based carbon fiber is 5 GPa-7 GPa, and the tensile modulus is 250 GPa-330 GPa.
[0010] Furthermore, the multi-stage gradient high-temperature drawing includes two-stage high-temperature drawing or three-stage high-temperature drawing.
[0011] Furthermore, the secondary high-temperature stretching includes a first-stage high-temperature stretching and a second-stage high-temperature stretching, wherein the first-stage high-temperature stretching temperature is 1600-2500°C, the first-stage high-temperature stretching ratio is 1.02-1.15, and the first-stage high-temperature stretching time is 0.5-5 minutes; the second-stage high-temperature stretching temperature is 2100-2800°C, the second-stage high-temperature stretching ratio is 1.05-1.20, and the second-stage high-temperature stretching time is 0.5-5 minutes.
[0012] Furthermore, the temperature of the second stage high temperature drawing is higher than that of the first stage high temperature drawing, and the temperature gradient between the first stage high temperature drawing temperature and the second stage high temperature drawing temperature is 100-700°C.
[0013] Furthermore, the three-stage high-temperature stretching includes a first-stage high-temperature stretching temperature, a second-stage high-temperature stretching and a third-stage high-temperature stretching, wherein the first-stage high-temperature stretching temperature is 1600-2500°C, the first-stage high-temperature stretching ratio is 1.02-1.15, and the first-stage high-temperature stretching time is 0.5-5 minutes; the second-stage high-temperature stretching temperature is 2100-2800°C, the second-stage high-temperature stretching ratio is 1.05-1.20, and the second-stage high-temperature stretching time is 0.5-5 minutes; the third-stage high-temperature stretching temperature is 2300-3000°C, the third-stage high-temperature stretching ratio is 1.05-1.20, and the third-stage high-temperature stretching time is 0.5-5 minutes.
[0014] Furthermore, the temperatures of the first-stage high-temperature drawing, the second-stage high-temperature drawing and the third-stage high-temperature drawing processes are increased sequentially, and the temperature gradient of the first-stage high-temperature drawing and the second-stage high-temperature drawing is 100-700°C, and the temperature gradient of the second-stage high-temperature drawing and the third-stage high-temperature drawing is 100-700°C.
[0015] Compared with the prior art, the present invention has at least the following beneficial effects: the present invention performs multi-stage high-temperature drawing on carbon fiber to make it have an elongated graphite microcrystalline structure, thereby simultaneously improving the tensile strength and tensile modulus of the carbon fiber. DETAILED DESCRIPTION
[0016] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments, and the following examples are only descriptive, not restrictive, and cannot be used to limit the scope of protection of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.
[0017] A first aspect of the present invention provides a polyacrylonitrile-based high-strength and high-modulus carbon fiber, wherein the carbon fiber has a tensile strength of 3.6 GPa-7.7 GPa and a tensile modulus of 350 GPa-700 GPa.
[0018] Furthermore, the graphite crystallite size La in the carbon fiber parallel to the fiber axis direction is ∥ The graphite crystallite size La perpendicular to the fiber axis ⊥ Ratio ∥ / La ⊥ is 1.5-2.5. ∥ / La ⊥ Meeting the above conditions indicates that the carbon fiber has an elongated graphite microcrystal structure, and the elongated graphite microcrystal structure arranged along the fiber axis is beneficial to the improvement of the tensile strength and modulus of the carbon fiber.
[0019] Specifically, the XRD test of carbon fiber can be performed to obtain the graphite crystallite size La parallel to the fiber axis. ∥ The graphite crystallite size La perpendicular to the fiber axis ⊥ .
[0020] Furthermore, the La of the carbon fiber ∥ is 7nm-20nm; the La of the carbon fiber ⊥ 4nm-11nm.
[0021] A second aspect of the present invention provides a method for preparing polyacrylonitrile-based high-strength and high-modulus carbon fibers, the method comprising: subjecting the polyacrylonitrile-based carbon fibers to multi-stage gradient high-temperature drawing in an inert atmosphere.
[0022] The present invention performs multi-stage high-temperature drawing on carbon fiber, gradually causing the carbon fiber to undergo plastic deformation at high temperature, and under the action of the drawing stress, the increase rate of the graphite microcrystal size along the fiber axis direction is greater than that in the direction perpendicular to the fiber axis, so that the carbon fiber has a slender graphite microcrystal structure, thereby simultaneously improving the tensile strength and tensile modulus of the carbon fiber.
[0023] According to an embodiment of the present invention, the tensile strength of the polyacrylonitrile-based carbon fiber is 5 GPa-7 GPa, and the tensile modulus is 250 GPa-330 GPa.
[0024] According to an embodiment of the present invention, the inert atmosphere comprises nitrogen, argon or a combination thereof.
[0025] According to an embodiment of the present invention, the multi-stage gradient high-temperature stretching includes two-stage high-temperature stretching or three-stage high-temperature stretching, wherein the two-stage high-temperature stretching includes a first-stage high-temperature stretching and a second-stage high-temperature stretching, wherein the first-stage high-temperature stretching temperature is 1600-2500°C, the first-stage high-temperature stretching ratio is 1.02-1.15, and the first-stage high-temperature stretching time is 0.5-5 minutes; the second-stage high-temperature stretching temperature is 2100-2800°C, the second-stage high-temperature stretching ratio is 1.05-1.20, and the second-stage high-temperature stretching time is 0.5-5 minutes.
[0026] According to an embodiment of the present invention, the temperature of the second-stage high-temperature drawing process is higher than the temperature of the first-stage drawing process, and the temperature gradient of the first-stage high-temperature drawing temperature and the second-stage high-temperature drawing temperature is 100-700° C. Specifically, when the temperature gradient is within the range of 100-700° C., the elongation of the graphite microcrystalline structure of the carbon fiber can be effectively achieved when the latter-stage drawing is implemented. When the temperature gradient is too small, the effect of the latter-stage drawing is not obvious. When the temperature gradient is greater than 700° C., the growth rate of the graphite microcrystalline parallel and perpendicular to the fiber axis during the drawing process is relatively fast, which is not conducive to the formation of an elongated graphite microcrystalline structure.
[0027] According to an embodiment of the present invention, the three-stage high-temperature stretching includes a first-stage high-temperature stretching temperature, a second-stage high-temperature stretching and a third-stage high-temperature stretching, wherein the first-stage high-temperature stretching temperature is 1600-2500°C, the first-stage high-temperature stretching ratio is 1.02-1.15, and the first-stage high-temperature stretching time is 0.5-5 minutes; the second-stage high-temperature stretching temperature is 2100-2800°C, the second-stage high-temperature stretching ratio is 1.05-1.20, and the second-stage high-temperature stretching time is 0.5-5 minutes; the third-stage high-temperature stretching temperature is 2300-3000°C, the third-stage high-temperature stretching ratio is 1.05-1.20, and the third-stage high-temperature stretching time is 0.5-5 minutes.
[0028] According to an embodiment of the present invention, the temperatures of the first-stage high-temperature drawing, the second-stage high-temperature drawing and the third-stage high-temperature drawing process are increased successively, and the temperature gradients of the first-stage high-temperature drawing and the second-stage high-temperature drawing are 100-700°C, and the temperature gradients of the second-stage high-temperature drawing and the third-stage high-temperature drawing are 100-700°C. Specifically, when the temperature gradient is within the range of 100-700°C, the elongation of the graphite microcrystalline structure of the carbon fiber can be effectively achieved when the latter-stage drawing is implemented. When the temperature gradient is too small, the effect of the latter-stage drawing is not obvious. When the temperature gradient is greater than 700°C, the growth rate of the graphite microcrystalline parallel and perpendicular to the fiber axis during the drawing process is fast, which is not conducive to the formation of an elongated graphite microcrystalline structure.
[0029] The present invention will be further described below by way of examples, but the protection scope of the present invention is not limited to these embodiments. The present invention may also have other various embodiments, and those skilled in the art may make various corresponding changes and deformations according to the present invention without departing from the spirit and essence of the present invention, but these corresponding changes and deformations shall all belong to the protection scope of the claims attached to the present invention.
[0030] Example 1
[0031] The polyacrylonitrile-based carbon fiber was subjected to two-stage high-temperature drawing in a nitrogen atmosphere, wherein the first-stage high-temperature drawing temperature was 1800°C, the first-stage high-temperature drawing ratio was 1.02, and the first-stage high-temperature drawing time was 1 minute; the second-stage high-temperature drawing temperature was 2400°C, the second-stage high-temperature drawing ratio was 1.08, and the second-stage high-temperature drawing time was 1 minute.
[0032] Example 2
[0033] In a nitrogen atmosphere, the polyacrylonitrile-based carbon fiber was subjected to two-stage gradient high-temperature drawing, wherein the first-stage high-temperature drawing temperature was 2400°C, the first-stage high-temperature drawing ratio was 1.10, and the first-stage high-temperature drawing time was 2 minutes; the second-stage high-temperature drawing temperature was 2600°C, the second-stage high-temperature drawing ratio was 1.15, and the second-stage high-temperature drawing time was 2 minutes.
[0034] Example 3
[0035] In an argon atmosphere, polyacrylonitrile-based carbon fiber was subjected to three-level gradient high-temperature stretching, wherein the first-level high-temperature stretching temperature was 2200°C, the first-level high-temperature stretching ratio was 1.03, and the first-level high-temperature stretching time was 3 minutes; the second-level high-temperature stretching temperature was 2400°C, the second-level high-temperature stretching ratio was 1.12, and the second-level high-temperature stretching time was 3 minutes; the third-level high-temperature stretching temperature was 2600°C, the third-level high-temperature stretching ratio was 1.15, and the third-level high-temperature stretching time was 3 minutes.
[0036] Example 4
[0037] In an argon atmosphere, polyacrylonitrile-based carbon fiber was subjected to three-level gradient high-temperature stretching, wherein the first-level high-temperature stretching temperature was 2400°C, the first-level high-temperature stretching ratio was 1.05, and the first-level high-temperature stretching time was 1 minute; the second-level high-temperature stretching temperature was 2600°C, the second-level high-temperature stretching ratio was 1.10, and the second-level high-temperature stretching time was 2 minutes; the third-level high-temperature stretching temperature was 2800°C, the third-level high-temperature stretching ratio was 1.15, and the third-level high-temperature stretching time was 3 minutes.
[0038] Example 5
[0039] In an argon atmosphere, polyacrylonitrile-based carbon fiber was subjected to three-level gradient high-temperature stretching, wherein the first-level high-temperature stretching temperature was 2000°C, the first-level high-temperature stretching ratio was 1.03, and the first-level high-temperature stretching time was 4 minutes; the second-level high-temperature stretching temperature was 2500°C, the second-level high-temperature stretching ratio was 1.08, and the second-level high-temperature stretching time was 4 minutes; the third-level high-temperature stretching temperature was 2700°C, the third-level high-temperature stretching ratio was 1.18, and the third-level high-temperature stretching time was 4 minutes.
[0040] Comparative Example
[0041] The polyacrylonitrile-based carbon fibers were graphitized at high temperature in an argon atmosphere at a graphitization temperature of 2700°C. The fibers were kept at a fixed length during the graphitization process and the graphitization time was 3 minutes.
[0042] The polyacrylonitrile-based carbon fibers used in Examples 1-5 and the comparative example are from the same batch, and the tensile strength of the polyacrylonitrile-based carbon fibers is 6.3 GPa, and the tensile modulus is 300 GPa.
[0043] The carbon fibers obtained after high temperature drawing treatment in Examples 1-5 and the carbon fibers after graphitization in the comparative example were subjected to XRD tests. The carbon fibers were subjected to equatorial and meridian scanning to obtain XRD spectra, and the crystallite parameters La parallel to and perpendicular to the fiber axis were calculated according to the Bragg equation using the diffraction peak near 43° in the spectra. ∥ and La ⊥ The tensile mechanical properties of carbon fiber are tested according to GB / T3362-2017 "Test method for tensile properties of carbon fiber multifilament". The test data are shown in Table 1.
[0044] Table 1
[0045]
[0046] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.
Claims
1. A polyacrylonitrile-based high-strength and high-modulus carbon fiber, characterized in that: The tensile strength of the carbon fiber is 3.6 GPa-7.7 GPa, and the tensile modulus is 350 GPa-700 GPa.
2. The polyacrylonitrile-based high-strength and high-modulus carbon fiber according to claim 1, characterized in that: The graphite crystallite size La in the carbon fiber parallel to the fiber axis direction ∥ The graphite crystallite size La perpendicular to the fiber axis ⊥ Ratio ∥ / La ⊥ It is 1.5-2.
5.
3. The polyacrylonitrile-based high-strength and high-modulus carbon fiber according to claim 2, characterized in that: The La of the carbon fiber ∥ 7nm-20nm; The La of the carbon fiber ⊥ 4nm-11nm.
4. A method for preparing the polyacrylonitrile-based high-strength and high-modulus carbon fiber according to any one of claims 1 to 3, characterized in that: include: The polyacrylonitrile-based carbon fibers were subjected to multi-stage gradient high-temperature drawing in an inert atmosphere.
5. The method according to claim 4, characterized in that The tensile strength of the polyacrylonitrile-based carbon fiber is 5 GPa-7 GPa, and the tensile modulus is 250 GPa-330 GPa.
6. The method according to claim 4 or 5, characterized in that: The multi-stage gradient high-temperature drawing includes two-stage high-temperature drawing or three-stage high-temperature drawing.
7. The method according to claim 6, characterized in that The two-stage high-temperature drawing includes a first-stage high-temperature drawing and a second-stage high-temperature drawing. Wherein, the first stage high temperature drawing temperature is 1600-2500°C, the first stage high temperature drawing ratio is 1.02-1.15, and the first stage high temperature drawing time is 0.5-5 minutes; The second stage high temperature stretching temperature is 2100-2800° C., the second stage high temperature stretching ratio is 1.05-1.20, and the second stage high temperature stretching time is 0.5-5 minutes.
8. The method according to claim 7, characterized in that The temperature of the second stage high temperature drawing is higher than that of the first stage high temperature drawing, and the temperature gradient between the first stage high temperature drawing and the second stage high temperature drawing is 100-700°C.
9. The method according to claim 6, characterized in that The three-stage high temperature drawing includes a first-stage high temperature drawing, a second-stage high temperature drawing and a third-stage high temperature drawing. Wherein, the first stage high temperature drawing temperature is 1600-2500°C, the first stage high temperature drawing ratio is 1.02-1.15, and the first stage high temperature drawing time is 0.5-5 minutes; The second stage high temperature drawing temperature is 2100-2800°C, the second stage high temperature drawing ratio is 1.05-1.20, and the second stage high temperature drawing time is 0.5-5 minutes; The third stage high temperature stretching temperature is 2300-3000° C., the third stage high temperature stretching ratio is 1.05-1.20, and the third stage high temperature stretching time is 0.5-5 minutes.
10. The method according to claim 9, characterized in that The temperatures of the first-stage high-temperature drawing, the second-stage high-temperature drawing and the third-stage high-temperature drawing processes are increased successively, and the temperature gradients of the first-stage high-temperature drawing and the second-stage high-temperature drawing are 100-700°C, and the temperature gradients of the second-stage high-temperature drawing and the third-stage high-temperature drawing are 100-700°C.