High-strength medium-modulus carbon fiber, high-strength high-modulus carbon fiber and preparation method thereof

Abstract

The invention discloses high-strength medium-modulus and high-strength high-modulus carbon fibers and a preparation method thereof, and belongs to the technical field of carbon fiber preparation, the preparation method comprises the following steps: adding polyacrylonitrile, 2, 4, 6-triaminopyrimidine and barbituric acid into an organic solvent according to a raw material ratio to prepare a polyacrylonitrile spinning solution; the preparation method comprises the following steps: defoaming and filtering a polyacrylonitrile spinning solution, preparing nascent fibers by a wet spinning process or a dry-wet spinning process, and then gradually preparing polyacrylonitrile protofilaments from the nascent fibers through washing, drafting, oiling, drying and densifying and steam drafting processes; a polyacrylonitrile precursor is subjected to pre-oxidation treatment through a multi-stage pre-oxidation process and then treated through a carbonization process or a graphitization process, and the high-strength medium-modulus carbon fiber and the high-strength high-modulus carbon fiber are obtained respectively. According to the invention, the carbonization or graphitization temperature required by production can be reduced, and the goals of high modulus and high strength of the carbon fiber can be achieved at the same time.

Description

Technical Field

[0001] The invention relates to high-strength medium modulus and high-strength high modulus carbon fibers and a preparation method thereof, belonging to the technical field of carbon fiber preparation. Background Art

[0002] As a high-performance fiber material, carbon fiber has been widely used in aerospace, automobile manufacturing, sports equipment and other fields due to its low density, high strength, high modulus and high stability. The traditional carbon fiber preparation process mainly includes polymerization, spinning, pre-oxidation, carbonization and other processes. Among them, the carbonization process is the key link to determine the performance of carbon fiber, and it usually needs to be carried out at high temperature to achieve the requirements of high modulus and high strength of the fiber. However, there are some limitations in the existing carbonization technology. First, high carbonization temperature not only consumes a lot of energy, but also has strict requirements on equipment, which limits the production efficiency and cost-effectiveness of carbon fiber. Secondly, the fiber modulus often increases with the increase of carbonization temperature, but too high carbonization temperature will lead to a decrease in fiber strength and affect the comprehensive mechanical properties of the fiber. In order to solve these problems, researchers have been exploring more economical preparation processes to produce high-performance carbon fiber products with both high strength and high modulus characteristics. Some studies have tried to prepare carbon fiber by optimizing precursor materials, improving spinning processes or adjusting carbonization conditions, but these methods are often difficult to achieve the goals of high modulus and high strength of carbon fiber at the same time. Summary of the invention

[0003] The technical problem to be solved by the present invention is to overcome the defects of the prior art and provide a high-strength medium modulus, high-strength high modulus carbon fiber and a preparation method thereof, which can reduce the carbonization or graphitization temperature required for production and can simultaneously achieve the goals of high modulus and high strength of carbon fiber.

[0004] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0005] A method for preparing high-strength medium modulus and high-strength high modulus carbon fibers comprises the following steps:

[0006] According to the raw material ratio, polyacrylonitrile, 2,4,6-triaminopyrimidine and barbituric acid are added into an organic solvent to prepare a polyacrylonitrile spinning solution;

[0007] The polyacrylonitrile spinning solution is degassed and filtered, and then the raw fiber is made into a primary fiber through a wet spinning process or a dry-wet spinning process, and then the primary fiber is gradually made into a polyacrylonitrile precursor through the steps of washing, drawing, oiling, drying and densification, and steam drawing;

[0008] The polyacrylonitrile precursor is pre-oxidized through a multi-stage pre-oxidation process, and then treated through a carbonization process or a graphitization process to obtain high-strength medium modulus carbon fiber and high-strength high modulus carbon fiber, respectively.

[0009] The organic solvent includes dimethyl sulfoxide, dimethylformamide or dimethylacetamide.

[0010] The solid content of polyacrylonitrile is 15-25wt%, and the total amount of 2,4,6-triaminopyrimidine and barbituric acid added accounts for 1-15wt% of the polyacrylonitrile.

[0011] The weight ratio of 2,4,6-triaminopyrimidine to barbituric acid was 1:1.

[0012] The pre-oxidation process temperature is 280~300℃.

[0013] The carbonization process temperature is 1200~1400℃.

[0014] The graphitization process temperature is 1900~2100℃.

[0015] A high-strength medium modulus and high-strength high modulus carbon fiber is prepared by the high-strength medium modulus and high-strength high modulus carbon fiber preparation method.

[0016] The fiber strength of high-strength medium-modulus carbon fiber is 4.0~5.0GPa and the modulus is 300~400 GPa.

[0017] The fiber strength of high-strength and high-modulus carbon fiber is 4.0~5.0GPa and the modulus is 400~500 GPa.

[0018] Beneficial effects of the present invention: The present invention provides a high-strength medium modulus, high-strength high modulus carbon fiber and a preparation method thereof. The high-performance carbon fiber contains an in-situ formed graphitized seed additive, and the graphitized seed additive includes 2,4,6-triaminopyrimidine and barbituric acid. In the process of preparing carbon fiber, the small molecule precursors of the graphitized seed additive, 2,4,6-triaminopyrimidine and barbituric acid, are pre-dissolved in the spinning solution. Such small molecule precursors can be in-situ self-assembled in the fiber matrix through hydrogen bonding in the subsequent fiber solidification and molding process to synthesize the graphitized seed additive, thereby achieving uniform dispersion of the graphitized seed additive in the fiber and playing a role in the subsequent heat treatment process. In addition, the graphitized seed additive in the fiber has good thermal stability, which can induce the graphitization transformation of the fiber matrix during low-temperature carbonization and low-temperature graphitization treatment and promote the initial graphite base plane to form a more complete graphite domain through rearrangement and cross-linking, thereby improving the strength and modulus of the fiber at the same time, and also reducing the carbonization temperature required for production, effectively reducing production costs, energy consumption and environmental impact. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a SEM morphology image of the polyacrylonitrile precursor prepared in Example 1 of the present invention;

[0020] Figure 2 This is a SEM morphology image of the carbon fiber prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0021] The present invention will be further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention and are not intended to limit the protection scope of the present invention.

[0022] Example 1

[0023] The present invention discloses a high-strength medium-modulus carbon fiber and a preparation method thereof. The method can successfully prepare the high-strength medium-modulus carbon fiber by adding specific graphitization seeds at a relatively low carbonization or graphitization temperature, and mainly comprises the following steps:

[0024] Step 1: According to the raw material ratio, polyacrylonitrile, 2,4,6-triaminopyrimidine and barbituric acid are added to dimethyl sulfoxide to prepare a polyacrylonitrile spinning solution. The solid content of polyacrylonitrile is 20wt%, and the total amount of 2,4,6-triaminopyrimidine and barbituric acid added accounts for 5wt% of polyacrylonitrile. The weight ratio of 2,4,6-triaminopyrimidine to barbituric acid added is 1:1.

[0025] Step 2: After degassing and filtering, the polyacrylonitrile spinning solution is processed into primary fibers through a wet spinning process or a dry-wet spinning process. Subsequently, the primary fibers are gradually processed into polyacrylonitrile precursor fibers through water washing, drawing, oiling, drying and densification, and steam drawing. The SEM morphology of the prepared polyacrylonitrile precursor fibers is shown in FIG. Figure 1 shown.

[0026] Step 3: pre-oxidize the polyacrylonitrile precursor through a multi-stage pre-oxidation process, and then process it through a carbonization process or a graphitization process to obtain high-strength medium modulus carbon fiber and high-strength high modulus carbon fiber, respectively. The pre-oxidation process temperature is 280°C, and the carbonization process temperature is 1400°C.

[0027] The invention makes a high-strength medium-modulus carbon fiber product, and the SEM morphology of the product is as follows: Figure 2 As shown, the fiber strength is 4.8 GPa and the modulus is 360 GPa.

[0028] This method effectively reduces production costs, reduces energy consumption and environmental impact by lowering the carbonization temperature required for production, while improving the performance of carbon fiber, meeting the needs of modern industry for high-performance fiber materials. Through the method of the present invention, the efficient graphitization structure transformation of the precursor polyacrylonitrile can be achieved at a lower carbonization temperature, reducing the generation of fiber defects, thereby obtaining carbon fiber with excellent mechanical properties. In addition, this method also has the advantages of simple process and easy large-scale production, and is expected to promote the application of carbon fiber materials in a wider range of fields, such as transportation, aerospace and other fields.

[0029] Example 2

[0030] The present invention discloses a high-strength and high-modulus carbon fiber and a preparation method thereof. The method can successfully prepare the high-strength and high-modulus carbon fiber by adding specific graphitization seeds at a relatively low carbonization or graphitization temperature, and mainly comprises the following steps:

[0031] Step 1: According to the raw material ratio, polyacrylonitrile, 2,4,6-triaminopyrimidine and barbituric acid are added to dimethyl sulfoxide to prepare a polyacrylonitrile spinning solution. The solid content of polyacrylonitrile is 18wt%, and the total amount of 2,4,6-triaminopyrimidine and barbituric acid added accounts for 10wt% of polyacrylonitrile. The weight ratio of 2,4,6-triaminopyrimidine to barbituric acid added is 1:1.

[0032] Step 2: After degassing and filtering, the polyacrylonitrile spinning solution is processed into primary fibers through a wet spinning process or a dry-wet spinning process, and then the primary fibers are gradually processed into polyacrylonitrile raw fibers through water washing, drawing, oiling, drying and densification, and steam drawing processes.

[0033] Step 3: pre-oxidize the polyacrylonitrile precursor through a multi-stage pre-oxidation process, and then process it through a carbonization process or a graphitization process to obtain high-strength medium modulus carbon fiber and high-strength high modulus carbon fiber, respectively. The pre-oxidation process temperature is 300°C, and the low-temperature graphitization process temperature is 2100°C.

[0034] The high-strength and high-modulus carbon fiber product prepared by the present invention has a fiber strength of 4.3 GPa and a modulus of 460 GPa.

[0035] Example 3

[0036] The present invention discloses a high-strength medium-modulus carbon fiber and a preparation method thereof. The method can successfully prepare the high-strength medium-modulus carbon fiber by adding specific graphitization seeds at a relatively low carbonization or graphitization temperature, and mainly comprises the following steps:

[0037] Step 1: According to the raw material ratio, polyacrylonitrile, 2,4,6-triaminopyrimidine and barbituric acid are added to dimethyl sulfoxide to prepare a polyacrylonitrile spinning solution. The solid content of polyacrylonitrile is 25wt%, and the total amount of 2,4,6-triaminopyrimidine and barbituric acid added accounts for 1wt% of polyacrylonitrile. The weight ratio of 2,4,6-triaminopyrimidine to barbituric acid added is 1:1.

[0038] Step 2: After degassing and filtering, the polyacrylonitrile spinning solution is processed into primary fibers through a wet spinning process or a dry-wet spinning process. Subsequently, the primary fibers are gradually processed into polyacrylonitrile precursor fibers through water washing, drawing, oiling, drying and densification, and steam drawing. The SEM morphology of the prepared polyacrylonitrile precursor fibers is shown in FIG. Figure 1 shown.

[0039] Step 3: pre-oxidize the polyacrylonitrile precursor through a multi-stage pre-oxidation process, and then process it through a carbonization process or a graphitization process to obtain high-strength medium modulus carbon fiber and high-strength high modulus carbon fiber, respectively. The pre-oxidation process temperature is 300°C, and the carbonization process temperature is 1200°C.

[0040] The high-strength medium-modulus carbon fiber product prepared by the present invention has a fiber strength of 4.2 GPa and a modulus of 330 GPa.

[0041] Example 4

[0042] The present invention discloses a high-strength and high-modulus carbon fiber and a preparation method thereof. The method can successfully prepare the high-strength and high-modulus carbon fiber by adding specific graphitization seeds at a relatively low carbonization or graphitization temperature, and mainly comprises the following steps:

[0043] Step 1: According to the raw material ratio, polyacrylonitrile, 2,4,6-triaminopyrimidine and barbituric acid are added to dimethylformamide to prepare a polyacrylonitrile spinning solution. The solid content of polyacrylonitrile is 15wt%, and the total amount of 2,4,6-triaminopyrimidine and barbituric acid added accounts for 15wt% of polyacrylonitrile. The weight ratio of 2,4,6-triaminopyrimidine to barbituric acid added is 1:1.

[0044] Step 2: After degassing and filtering, the polyacrylonitrile spinning solution is processed into primary fibers through a wet spinning process or a dry-wet spinning process, and then the primary fibers are gradually processed into polyacrylonitrile raw fibers through water washing, drawing, oiling, drying and densification, and steam drawing processes.

[0045] Step 3: pre-oxidize the polyacrylonitrile precursor through a multi-stage pre-oxidation process, and then process it through a carbonization process or a graphitization process to obtain high-strength medium modulus carbon fiber and high-strength high modulus carbon fiber, respectively. The pre-oxidation process temperature is 300°C, and the low-temperature graphitization process temperature is 1900°C.

[0046] The high-strength and high-modulus carbon fiber product prepared by the present invention has a fiber strength of 4.5 GPa and a modulus of 430 GPa.

[0047] 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 principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing high-strength medium modulus and high-strength high modulus carbon fibers, characterized in that: The following steps are involved: Adding polyacrylonitrile, 2,4,6-triaminopyrimidine and barbituric acid into an organic solvent to prepare a polyacrylonitrile spinning solution; The polyacrylonitrile spinning solution is degassed and filtered, and then the raw fiber is made into a primary fiber through a wet spinning process or a dry-wet spinning process, and then the primary fiber is gradually made into a polyacrylonitrile precursor through the steps of washing, drawing, oiling, drying and densification, and steam drawing; The polyacrylonitrile precursor is pre-oxidized through a multi-stage pre-oxidation process, and then treated through a carbonization process or a graphitization process to obtain high-strength medium modulus carbon fiber and high-strength high modulus carbon fiber, respectively.

2. The method for preparing high-strength medium modulus and high-strength high modulus carbon fibers according to claim 1, characterized in that: The organic solvent includes dimethyl sulfoxide, dimethylformamide or dimethylacetamide.

3. The method for preparing high-strength medium modulus and high-strength high modulus carbon fibers according to claim 1, characterized in that: The solid content of polyacrylonitrile is 15-25wt%, and the total amount of 2,4,6-triaminopyrimidine and barbituric acid added accounts for 1-15wt% of the polyacrylonitrile.

4. The method for preparing high-strength medium modulus and high-strength high modulus carbon fibers according to claim 3, characterized in that: The weight ratio of 2,4,6-triaminopyrimidine to barbituric acid was 1:

1.

5. The method for preparing high-strength medium modulus and high-strength high modulus carbon fibers according to claim 1, characterized in that: The pre-oxidation process temperature is 280~300℃.

6. The method for preparing high-strength medium modulus and high-strength high modulus carbon fibers according to claim 1, characterized in that: The carbonization process temperature is 1200~1400℃.

7. The method for preparing high-strength medium modulus and high-strength high modulus carbon fibers according to claim 1, characterized in that: The graphitization process temperature is 1900~2100℃.

8. A high-strength medium modulus or high-strength high modulus carbon fiber, characterized in that: The carbon fiber is prepared by the method for preparing high-strength medium modulus or high-strength high modulus carbon fiber according to any one of claims 1 to 7.

9. The high-strength medium modulus and high-strength high modulus carbon fiber according to claim 8, characterized in that: The fiber strength of high-strength medium-modulus carbon fiber is 4.0~5.0GPa and the modulus is 300~400 GPa.

10. The high-strength medium modulus and high-strength high modulus carbon fiber according to claim 8, characterized in that: The fiber strength of high-strength and high-modulus carbon fiber is 4.0~5.0GPa and the modulus is 400~500 GPa.

Images