3k polyacrylonitrile precursor, high-strength 3k carbon fiber and preparation method of 3k polyacrylonitrile precursor and high-strength 3k carbon fiber

Abstract

The invention relates to a 3k polyacrylonitrile precursor, a high-strength 3k carbon fiber and a preparation method thereof, and belongs to the technical field of carbon fiber production. The preparation method of the 3k polyacrylonitrile precursor comprises the following steps: spraying a spinning stock solution through a 4k spinneret plate by adopting a dry-jet wet spinning method, enabling the spinning stock solution to enter a coagulating bath through an air layer for forming, and then carrying out water washing, water drawing, oiling, drying and steam drawing to prepare the 3k polyacrylonitrile precursor. According to the preparation method, the 3k polyacrylonitrile precursor is prepared by adopting a 4k spinneret plate through a dry-jet wet spinning method, so that the prepared 3k polyacrylonitrile precursor has lower fineness and higher mechanical strength, and correspondingly, the prepared 3k carbon fiber can have excellent mechanical strength.

Description

Technical Field

[0001] The present application relates to the technical field of carbon fiber production, and in particular to a 3k polyacrylonitrile precursor, a high-strength 3k carbon fiber and a preparation method thereof. Background Art

[0002] Small tow carbon fiber is also known as aerospace grade carbon fiber because of its light weight and high strength. It is widely used in helicopter rotor blades, wing components, propellers, seats and instrument housings. Among small tow carbon fibers, 3k carbon fiber is currently the most widely used and popular one, and how to further improve the strength of 3k carbon fiber is also one of the current research hotspots. Summary of the invention

[0003] To solve the above problems, the purpose of the embodiments of the present application includes providing a 3k polyacrylonitrile precursor, a high-strength 3k carbon fiber and a preparation method thereof, which can effectively improve the mechanical strength of the 3k carbon fiber.

[0004] In a first aspect, the present application provides a method for preparing 3k polyacrylonitrile precursor, comprising the following steps:

[0005] The dry-jet wet spinning method is adopted, and the spinning solution is sprayed out through a 4k spinneret and then enters a coagulation bath through an air layer to be formed, and then washed, water-drawn, oiled, dried and steam-drawn to produce 3k polyacrylonitrile precursor.

[0006] In the above technical scheme, a 3k spinneret is usually used in conventional technology to prepare 3k carbon fiber precursor. In the present application, a 4k spinneret is used instead of a 3k spinneret for dry-wet spinning. On the basis of the same total slurry supply and the same drafting multiple, a finer denier and stronger 3k polyacrylonitrile precursor is prepared.

[0007] In some embodiments of the present application, the height of the air layer is 5-15 mm.

[0008] And / or, the coagulation bath comprises a solvent and a coagulant, the coagulant is water, the mass concentration of the solvent is 25% to 45%; the temperature of the coagulation bath is 0 to 15° C., and the pH value is 8.0 to 9.0.

[0009] And / or, the total drafting multiple of the 3k polyacrylonitrile precursor is 9 to 35 times.

[0010] In some embodiments of the present application, the spinning solution and the coagulation bath use the same solvent, which is at least one of dimethyl sulfoxide, dimethylformamide or dimethylacetamide. Optionally, the residual solvent content in the polyacrylonitrile precursor after water drawing is 0 to 100 ppm.

[0011] In the above technical scheme, by controlling the conditions of each stage of the dry-jet wet spinning method, the precursor can be made finer, the molecular chains can be preferentially oriented along the fiber axis, and the crystallinity can be higher. The high orientation and high density of the precursor are the basis for preparing high-strength carbon fibers.

[0012] In some embodiments of the present application, the oil used in the oiling process includes at least one of epoxy silicone oil, amino silicone oil or polyether silicone oil. Optionally, the oil content of the 3k polyacrylonitrile precursor is 0.5% to 0.8%.

[0013] In the above technical scheme, by compounding the above silicone oils, the composite oil agent can not only improve the film-forming and protective properties of the oil agent on the surface of the filament bundle, but also make the filament bundle have high heat resistance, thereby improving the mechanical properties of the carbon fiber.

[0014] In the second aspect, the present application provides a 3k polyacrylonitrile precursor prepared by the above-mentioned preparation method, which has a fineness of 0.70-0.90 dtex, a single yarn strength of 8.0-10.0 cN / dtex, and a single yarn modulus of 75-110 cN / dtex.

[0015] In the above technical scheme, the polyacrylonitrile precursor prepared by a conventional 3k spinneret has a fineness of about 1.1 dtex. In this application, a 4k spinneret is used instead of a 3k spinneret for dry-wet spinning to prepare a finer denier and higher strength 3k polyacrylonitrile precursor.

[0016] In a third aspect, the present application provides a method for preparing 3k carbon fiber, comprising the following steps:

[0017] The 3k polyacrylonitrile precursor is subjected to pre-oxidation treatment, low-temperature carbonization treatment, high-temperature carbonization treatment and post-treatment in sequence to obtain high-strength 3k carbon fiber.

[0018] In the above technical solution, the mechanical strength of 3k carbon fiber is significantly improved by using 3k polyacrylonitrile precursor with lower fineness and higher strength, combined with pre-oxidation treatment, low-temperature carbonization treatment and high-temperature carbonization treatment.

[0019] In some embodiments of the present application, the pre-oxidation treatment includes: gradient heating the polyacrylonitrile precursor from 210°C to 265°C, providing 5 to 7 oxidation temperature zones in the range of 210°C to 265°C, and the temperature difference between two adjacent oxidation temperature zones is 2°C to 20°C.

[0020] In the above technical solution, the polyacrylonitrile precursor undergoes a violent cyclization reaction during the pre-oxidation stage, which is prone to concentrated heat release for a short period of time, resulting in damage to the internal structure of the fiber. By setting multiple oxidation temperature zones, the reaction rate can be slowed down, thereby improving the fiber structure and enhancing the thermal stability and crystallinity of the fiber.

[0021] In some embodiments of the present application, the low-temperature carbonization treatment includes: performing gradient heating from 380°C to 720°C on the pre-oxidation fiber obtained after the pre-oxidation treatment, and providing 7 to 9 first carbonization temperature zones within the range of 380°C to 720°C, and the temperature difference between two adjacent first carbonization temperature zones is 40°C to 100°C. Optionally, the total time of the low-temperature carbonization treatment is 4 to 6 minutes.

[0022] In the above technical solution, the exothermic reaction of the fiber in the low-temperature carbonization stage is not as intense as the cyclization reaction during the pre-oxidation process, but there will still be a short period of concentrated heat release, which can easily cause the fiber to instantly increase in temperature, resulting in damage to the internal structure. At the same time, the decomposition products of the internal fiber reaction cannot be instantly removed, causing impurities such as tar to adhere to the fiber and cause surface defects, resulting in reduced fiber performance. By setting multiple first carbonization temperature zones in the low-temperature carbonization stage, the temperature gradient of the temperature interval where the fiber reacts violently is reduced, the carbonization time is extended, and the reaction rate of the fiber in the concentrated reaction interval is reduced, which can reduce the decomposition rate of the internal fiber products so that the protective nitrogen can clean them up in time, reducing the risk of pollution.

[0023] In some embodiments of the present application, the high temperature carbonization treatment includes: performing gradient heating from 1050°C to 1300°C on the low temperature carbonized fiber obtained after the low temperature carbonization treatment, and providing 3 to 5 second carbonization temperature zones in the range of 1050°C to 1300°C, and the temperature difference between two adjacent second carbonization temperature zones is 0 to 150°C. Optionally, the total time of the high temperature carbonization treatment is 3 to 5 minutes.

[0024] In the above technical solution, the carbonization temperature in the range of 1000-1300°C is the peak area of ​​denitrification inside the fiber. The condensation reaction intensifies, causing a large amount of nitrogen to escape in the form of nitrogen gas, resulting in a large number of void defects inside the fiber, which reduces the density of the carbon fiber. Therefore, multiple second carbonization temperature zones are set to adjust the temperature gradient of the fiber in different reaction temperature intervals through multiple temperature zones, thereby slowing down the reaction rate, reducing the large pores caused by the concentrated escape of nitrogen from the inside of the fiber, and effectively controlling the nitrogen escape rate, so that the size of the pore channel caused is reduced, thereby reducing the overall porosity of the fiber, effectively improving the density of the carbon fiber, and then improving the tensile strength of the carbon fiber.

[0025] In some embodiments of the present application, post-processing includes surface treatment, washing, sizing, drying and winding.

[0026] In a fourth aspect, an embodiment of the present application provides a high-strength 3k carbon fiber prepared by the above-mentioned preparation method. The high-strength 3k carbon fiber has a tensile strength of 5000 to 6000 MPa and a tensile modulus of 230 to 260 GPa.

[0027] The high-strength 3k carbon fiber provided in the embodiment of the present application has excellent mechanical properties. Compared with conventional 3k carbon fiber, the tensile strength and tensile modulus are significantly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0029] Figure 1 This is a process flow chart of the method for preparing high-strength 3k carbon fiber provided in an embodiment of the present application. DETAILED DESCRIPTION

[0030] Figure 1 This is a process flow chart of the preparation method of high-strength 3k carbon fiber provided in the embodiment of this application. Figure 1 The preparation method of the high-strength 3k carbon fiber provided in the present application comprises the following steps:

[0031] S110 adopts dry-jet wet spinning method, the spinning solution is sprayed out through the 4k spinneret and then enters the coagulation bath through the air layer to form, and then washed, water drawn, oiled, dried and steam drawn to produce 3k polyacrylonitrile precursor.

[0032] In the dry-jet wet spinning method, the height of the air layer can be controlled to be 5 to 15 mm, for example, 5 mm, 10 mm or 15 mm.

[0033] The coagulation bath comprises a solvent and a coagulant, wherein the coagulant is water and the mass concentration of the solvent can be 25% to 45%.

[0034] The temperature of the coagulation bath is 0 to 15° C., and the pH value is 8.0 to 9.0. For example, an inorganic alkaline solution such as ammonia water or sodium hydroxide aqueous solution may be used to adjust the pH value of the coagulation bath.

[0035] It should be noted that the solvent used in the spinning solution and the coagulation bath is the same, and the solvent is at least one of dimethyl sulfoxide, dimethylformamide or dimethylacetamide.

[0036] As an example, the coagulation bath in the present application contains dimethyl sulfoxide and water, wherein the mass concentration of dimethyl sulfoxide is 40%.

[0037] In the embodiment of the present application, after the water washing stage, the residual solvent content in the 3k polyacrylonitrile precursor can be controlled to be 0 to 100 ppm.

[0038] In the oiling process, the oil used includes at least one of epoxy silicone oil, amino silicone oil or polyether silicone oil. As an example, the oil may include epoxy silicone oil, amino silicone oil and polyether silicone oil (mass ratio is 1.5:1.03:1.0). The oil content of the polyacrylonitrile precursor can be controlled at 0.5% to 0.8%.

[0039] During the entire dry-jet wet spinning process, the total drafting multiple of 3k polyacrylonitrile precursor is 9 to 35 times.

[0040] In the embodiment of the present application, a 4k spinneret is used instead of a conventional 3k spinneret for spinning, and the prepared 3k polyacrylonitrile precursor has a fineness of 0.70 to 0.90 dtex, a single yarn strength of 8.0 to 10.0 cN / dtex, and a single yarn modulus of 75 to 110 cN / dtex, that is, a precursor with lower fineness and higher strength is prepared.

[0041] As an example, the fineness of the 3k polyacrylonitrile precursor in the present application is 0.825 dtex and the linear density is 0.33 g / m.

[0042] It should be noted that those skilled in the art know that a 3k spinneret corresponds to a spinneret with about 3,000 spinneret holes, and a 4k spinneret corresponds to a spinneret with about 4,000 spinneret holes. Unlike conventional 3k carbon fiber precursors, which contain just 3,000 filaments, the 3k polyacrylonitrile precursor prepared in this application actually contains 4,000 filaments. By controlling the same preparation conditions as the original 3k spinneret during the preparation process, that is, controlling the same unit slurry supply of the metering pump and the same drafting multiple, after the precursor is made, the total mass per unit length of the precursor remains unchanged, but the number of filaments increases to 4,000, the fineness of the precursor decreases, and the strength of the precursor is improved.

[0043] S120, 3k polyacrylonitrile precursor is subjected to pre-oxidation treatment, low-temperature carbonization treatment, high-temperature carbonization treatment and post-treatment in sequence to obtain high-strength 3k carbon fiber.

[0044] The pre-oxidation treatment includes: heating the polyacrylonitrile precursor at a gradient temperature from 210°C to 265°C, and providing a plurality of oxidation temperature zones within the range of 210°C to 265°C.

[0045] Optionally, the number of oxidation temperature zones is 5, 6 or 7, and the temperature difference between two adjacent oxidation temperature zones is 2°C to 20°C.

[0046] As an example, the number of oxidation temperature zones is 6, and the temperatures are 210°C, 230°C, 250°C, 260°C, 263°C, and 265°C respectively.

[0047] The low-temperature carbonization treatment includes: performing gradient heating from 380°C to 720°C on the pre-oxidized fibers obtained after the pre-oxidation treatment, and providing a plurality of first carbonization temperature zones within the range of 380°C to 720°C.

[0048] Optionally, the number of the first carbonization temperature zones is 7, 8 or 9, and the temperature difference between two adjacent first carbonization temperature zones is 40° C. to 100° C. Optionally, the total time of the low-temperature carbonization treatment is 4 to 6 minutes.

[0049] As an example, the number of the first carbonization temperature zones is 8, and the temperatures are 380°C, 420°C, 480°C, 560°C, 640°C, 740°C, 780°C, and 720°C respectively.

[0050] The high temperature carbonization treatment includes: performing gradient heating from 1050°C to 1300°C on the low temperature carbonized fiber obtained after the low temperature carbonization treatment, and providing a plurality of second carbonization temperature zones within the range of 1050°C to 1300°C.

[0051] Optionally, the number of the second carbonization temperature zones is 3, 4 or 5, and the temperature difference between two adjacent second carbonization temperature zones is 0 to 150° C. Optionally, the total time of the high-temperature carbonization treatment is 3 to 5 minutes.

[0052] As an example, the number of the second carbonization temperature zones is 4, and the temperatures are 1050°C, 1200°C, 1300°C, and 1300°C respectively.

[0053] It should be noted that the carbon fiber runs at a uniform speed during the pre-oxidation and carbonization process, so the time spent in each temperature zone is the same. The low-temperature carbonization process and the high-temperature carbonization process are carried out under a protective atmosphere such as helium or nitrogen, and the oxygen content in the protective atmosphere is 0 to 5 ppm.

[0054] It should be noted that, in some embodiments, the high-temperature carbonization treatment may further include graphitization treatment of the carbonized fibers. For example, the carbon fibers after the high-temperature carbonization treatment may be subjected to gradient heating from 1300° C. to 1600° C.

[0055] It is understood that after the high temperature carbonization treatment, the carbonized fiber is further subjected to post-treatment, such as surface treatment, washing, sizing, drying and winding. These post-treatment steps can be carried out according to conventional processes and will not be described in detail in this application.

[0056] In addition, an embodiment of the present application also provides a high-strength 3K carbon fiber prepared by the above preparation method.

[0057] It should be noted that according to the GB / T 26752-2020 standard, polyacrylonitrile-based carbon fibers can be divided into high-strength type, high-strength medium model, high model and high-strength high model according to their mechanical properties. The tensile strength of high-strength carbon fibers ranges from 3500 to 5500 MPa, and the tensile modulus ranges from 220 to 260 GPa.

[0058] The high-strength 3k carbon fiber prepared in this application has a tensile strength greater than 5000MPa, a tensile modulus greater than 230GPa, and a bulk density greater than 1.80g / cm 3 , that is, it has a higher density and excellent mechanical properties, and can be more effectively used in the aerospace field, thereby expanding the application scope of 3k carbon fiber.

[0059] The features and properties of the present application are further described in detail below in conjunction with specific examples. If no specific conditions are specified in the examples, the conditions are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially.

[0060] Example 1

[0061] The present application embodiment provides a high-strength 3k carbon fiber, and the preparation method thereof comprises the following steps:

[0062] (1) Using the dry-jet wet spinning method, the polyacrylonitrile-based stock solution with dimethyl sulfoxide as the solvent is spun by a metering pump through a 4k spinneret (aperture 0.12mm, number of holes 4000), and enters the coagulation bath through a 5mm air layer to form a primary fiber. The coagulation bath includes dimethyl sulfoxide and water, the concentration of dimethyl sulfoxide is 40%, the temperature of the coagulation bath is 10℃, and the pH value is 8.5. The primary fiber is then washed with water at 35℃, drawn with water at 70℃, oiled at 25℃, dried at 180℃, and drawn with steam at 0.45MPa to obtain 3k polyacrylonitrile precursor. Among them, after water drawing, the residual amount of dimethyl sulfoxide in the 3k polyacrylonitrile precursor was 40ppm, the pre-drawing multiple was 2.3, the water drawing multiple was 3.0, the steam drawing multiple was 4.0, and the oil agent component was epoxy silicone oil: amino silicone oil: polyether silicone oil = 1.5:1.03:1.0). The oil content of the prepared 3k polyacrylonitrile precursor was 0.8%, the fineness was 0.825dtex, and the linear density was 0.33g / m.

[0063] (2) A pre-oxidation furnace is used to perform six-temperature pre-oxidation treatment on polyacrylonitrile precursor to obtain pre-oxidized fibers. The six-temperature pre-oxidation temperatures are 210°C, 230°C, 250°C, 260°C, 263°C, and 265°C, respectively.

[0064] The pre-oxidized fiber is then passed through a low-temperature furnace for eight-temperature-zone low-temperature carbonization treatment to obtain low-temperature carbonized fiber. The temperatures in the eight temperature zones are 380°C, 420°C, 480°C, 560°C, 640°C, 740°C, 780°C, and 720°C, respectively. The total fiber treatment time is 5 minutes.

[0065] The low-temperature carbonized fiber is then subjected to a high-temperature furnace for a four-temperature-zone high-temperature carbonization treatment to obtain high-temperature carbonized fiber. The temperatures of the four temperature zones are 1050°C, 1200°C, 1300°C, and 1300°C, respectively. The total fiber treatment time is 4 minutes.

[0066] The high-temperature carbonized fiber is surface treated, washed, sized and wound to obtain high-strength 3k carbon fiber.

[0067] When the polyacrylonitrile precursor passes through the pre-oxidation furnace, the low-temperature furnace and the high-temperature furnace in sequence, the temperature of each temperature zone in each furnace is preset first, so that the temperature of each temperature zone reaches the preset value, and then the precursor starts to run at a constant line speed (520m / h) and passes through the pre-oxidation furnace, the low-temperature furnace and the high-temperature furnace in sequence.

[0068] Comparative Example 1

[0069] The comparative example of the present application provides a conventional 3k carbon fiber, and the preparation method thereof differs from that of Example 1 only in that:

[0070] In step (1), a 3k spinneret (with a hole diameter of 0.12 mm and a hole number of 3000) is used instead of a 4k spinneret for spinning.

[0071] Performance testing and result analysis

[0072] The polyacrylonitrile precursor and high-strength 3k carbon fiber prepared in Example 1 were subjected to performance tests, and 15 effective samples of the 3k carbon fiber prepared in Comparative Example 1 were taken for performance tests. The performance test results are shown in Tables 1 to 3.

[0073] Table 1 Performance test results of polyacrylonitrile precursor in Example 1

[0074]

[0075] The conventional AC45-3k carbon fiber is produced by 3k spinneret dry-jet wet spinning (such as comparative example 1), and the fineness of the prepared polyacrylonitrile precursor is about 1.1 dtex. The present application adopts 4k spinneret and dry-jet wet spinning to prepare 3k polyacrylonitrile precursor (actually containing 4000 monofilaments) with a fineness of about 0.825 dtex and a linear density of 0.33 g / m. As shown in Table 1, the precursor strength of the 3k polyacrylonitrile precursor prepared in the present application is 8.0-10.0 cN / dtex, and the precursor modulus is 75-110 cN / dtex.

[0076] Table 2 Performance test results of high-strength 3k carbon fiber in Example 1

[0077]

[0078] Table 3 Performance test results of 3k carbon fiber in comparative example 1

[0079]

[0080]

[0081] Comparing the performance differences between Table 2 and Table 3, in this application, by adjusting the spinneret during the preparation of the precursor, and combining pre-oxidation treatment, low-temperature carbonization treatment and high-temperature carbonization treatment, the tensile strength of the prepared high-strength 3k carbon fiber is greater than 5000MPa, the tensile modulus is greater than 230GPa, and the bulk density is higher than 1.80g / cm 3 When the tensile modulus is within the range of 230-260 GPa, the tensile strength can reach up to 5911 MPa. Compared with the 3k carbon fiber prepared by conventional technology, the tensile modulus and tensile strength are significantly improved.

[0082] The embodiments described above are part of the embodiments of the present application, rather than all of the embodiments. The detailed description of the embodiments of the present application is not intended to limit the scope of the present application for protection, but merely represents the selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present application.

Claims

1. A method for preparing 3k polyacrylonitrile precursor, characterized in that: The following steps are involved: The dry-jet wet spinning method is adopted, and the spinning solution is sprayed out through a 4k spinneret and then enters a coagulation bath through an air layer to be formed, and then washed, water-drawn, oiled, dried and steam-drawn to produce 3k polyacrylonitrile precursor.

2. The preparation method according to claim 1, characterized in that: The height of the air layer is 5 to 15 mm; And / or, the coagulation bath comprises a solvent and a coagulant, the coagulant is water, the mass concentration of the solvent is 25% to 45%; the temperature of the coagulation bath is 0 to 15° C., and the pH value is 8.0 to 9.0; And / or, the total drafting multiple of the 3k polyacrylonitrile precursor is 9 to 35 times.

3. The preparation method according to claim 1 or 2, characterized in that: The spinning solution and the coagulation bath use the same solvent, which is at least one of dimethyl sulfoxide, dimethylformamide or dimethylacetamide; And / or, the residual solvent content in the 3k polyacrylonitrile precursor is 0 to 100 ppm.

4. The preparation method according to claim 1, characterized in that: The oil used in the oiling section includes at least one of epoxy silicone oil, amino silicone oil or polyether silicone oil; And / or, the oil content of the 3k polyacrylonitrile precursor is 0.5% to 0.8%.

5. A 3k polyacrylonitrile precursor prepared by the preparation method according to any one of claims 1 to 4, characterized in that: The 3k polyacrylonitrile precursor has a fineness of 0.70 to 0.90 dtex, a single-filament strength of 8.0 to 10.0 cN / dtex, and a single-filament modulus of 75 to 110 cN / dtex.

6. A method for preparing high-strength 3k carbon fiber, characterized in that: The following steps are involved: The 3k polyacrylonitrile precursor as claimed in claim 5 is subjected to pre-oxidation treatment, low-temperature carbonization treatment, high-temperature carbonization treatment and post-treatment in sequence to obtain a high-strength 3k carbon fiber.

7. The preparation method according to claim 6, characterized in that: The pre-oxidation treatment includes: heating the polyacrylonitrile precursor at a gradient temperature from 210°C to 265°C, providing 5 to 7 oxidation temperature zones within the range of 210°C to 265°C, and the temperature difference between two adjacent oxidation temperature zones is 2°C to 20°C.

8. The preparation method according to claim 6, characterized in that: The low-temperature carbonization treatment includes: gradient heating the pre-oxidized fiber obtained after the pre-oxidation treatment from 380°C to 720°C, providing 7 to 9 first carbonization temperature zones in the range of 380°C to 720°C, and the temperature difference between two adjacent first carbonization temperature zones is 40 to 100°C.

9. The preparation method according to claim 6, characterized in that: The high-temperature carbonization treatment includes: performing gradient heating from 1050°C to 1300°C on the low-temperature carbonized fiber obtained after the low-temperature carbonization treatment, and providing 3 to 5 second carbonization temperature zones in the range of 1050 to 1300°C, and the temperature difference between two adjacent second carbonization temperature zones is 0 to 150°C.

10. A high-strength 3k carbon fiber, characterized in that: The high-strength 3k carbon fiber is prepared by the preparation method according to any one of claims 6 to 9, and has a tensile strength of 5000 to 6000 MPa and a tensile modulus of 230 to 260 GPa.

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