Method for detecting mechanical properties of polyacrylonitrile-based carbon fiber precursor and pre-oxidized fiber
By optimizing the tensile speed, modulus algorithm, and fixture design, and combining the method of taking the average value of multiple repeated tests, the problem of low detection accuracy of carbon fiber precursor and pre-oxidized fiber bundles in the existing technology has been solved, and rapid and accurate mechanical property testing has been achieved.
Patent Information
- Application Number
- CN202211032386.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2022-08-26
- Publication Date
- 2025-10-17
- Estimated Expiration
- 2042-08-26
AI Technical Summary
The existing technology lacks a simple, fast and accurate method for testing the mechanical properties of carbon fiber precursor and pre-oxidized fiber bundles, resulting in low testing accuracy and poor repeatability, which makes it difficult to meet the rapid testing needs of carbon fiber production processes.
A mechanical properties testing machine was used for testing. The tensile speed was set to 80-100 mm/min, the modulus algorithm was Young's modulus, the modulus value range was 0.1-1.0% strain, the data acquisition speed was 8-10 ms, the fixture spacing and clamping method were optimized, including pneumatic fixtures and a specific twist number, the test was repeated 8-10 times, and the calculation formula was in accordance with GB/T3362-2005 and GB/T1446.
It enables rapid and accurate mechanical property testing of carbon fiber precursor and pre-oxidized fiber bundles, reduces the coefficient of variation in testing, improves the repeatability and accuracy of testing, and is suitable for large-scale production environments.
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Figure CN115372142B_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The application relates to the technical field of carbon fibers, in particular to a mechanical property detection method for polyacrylonitrile-based carbon fiber precursors. BACKGROUND
[0002] The polyacrylonitrile-based carbon fiber precursors (hereinafter referred to as precursors) and pre-oxides directly affect the mechanical properties of carbon fibers. At present, the detection methods for the mechanical properties of the precursors and pre-oxides (such as tensile breaking strength, coefficient of variation of breaking strength, elongation at break, coefficient of variation of elongation at break, modulus and the like) are only the Chinese Textile Industry Standard FZ / T 54065-2012 "Polyacrylonitrile-based Carbon Fiber Precursors" and the enterprise standards Q / 320705WAF 13-2017, Q / 320705WAF 14-2017 and Q / 320705WAF 15-2017 of Zhongfu Goderich Carbon Fiber Co., Ltd. and the like. No relevant standards are found for the detection method of the mechanical properties of the pre-oxides.
[0003] In the FZ / T 54065-2012 "Polyacrylonitrile-based Carbon Fiber Precursors" standard, the detection method of the mechanical properties is quoted from the GB / T19975 "High-strength filament tensile property test method" and the GB / T14337 "Chemical fiber short-cut filament tensile property test method".
[0004] In the GB / T19975 "High-strength filament tensile property test method", the test sample is a precursor bundle. However, at least the following problems exist: (1) for the detection method of the initial modulus, the point at which the change of the strength with the elongation is the largest on the tensile curve needs to be found, and the slope of the tangent line at the point needs to be calculated, which is relatively complicated to operate. (2) According to the 8.2.7 item, the untwisted filament is twisted before the test. For aramid fibers, the unit of the twist number is twist / meter, and the number of twists needs to be large, but no specific provisions are given for how to twist the long filament of the precursor before the test. (3) No specific provisions are given for how to clamp the precursor on the clamp to prevent the precursor from untwisting or slipping during the clamping process. (4) In the breaking strength tensile test process, the clamping distance is large, the required sample length is long (500 mm), and the tensile speed is 250 mm / min. However, the detection accuracy is affected by the too fast tensile speed. (5) Each sample is tested 5 times, which is too few for the carbon fiber precursors and is not representative. In summary, this method is mainly for ultra-high molecular weight polyethylene fibers and aramid fibers, and is not strong in pertinence for the tensile properties of carbon fiber precursors.
[0005] GB / T14337 "Chemical fiber short fiber tensile property test method" is suitable for the detection of the single fiber mechanical property of the raw yarn. In the detection process, one single fiber is stripped out of the raw yarn bundle and then fixed on the tension clamp. The operation process requires special care and is complicated, which is not suitable for rapid detection in mass production and timely guidance of process adjustment of the production line.
[0006] In addition, the detection method of the mechanical property of the raw yarn in the enterprise standards Q / 320705WAF 13-2017, Q / 320705WAF 14-2017 and Q / 320705WAF 15-2017 of Zhongfushenying Carbon Fiber Co., Ltd. also refers to GB / T14337 "Chemical fiber short fiber tensile property test method", which is also not suitable for rapid detection of the raw yarn index.
[0007] In summary, there is an urgent need for a carbon fiber raw yarn and pre-oxidized yarn bundle mechanical property detection method that is simple and fast, accurate and has a small dispersion coefficient, to meet the requirements of the raw yarn and carbon fiber production process for rapid provision of mechanical property detection data. SUMMARY
[0008] Therefore, the present application provides a polyacrylonitrile-based carbon fiber raw yarn and pre-oxidized yarn mechanical property detection method, which is simple and fast, accurate and has a small dispersion coefficient, to meet the requirements of the raw yarn and carbon fiber production process for rapid provision of mechanical property detection data.
[0009] To achieve the above-mentioned purpose, the present application mainly provides the following technical solutions:
[0010] On the one hand, the present application provides a polyacrylonitrile-based carbon fiber raw yarn and pre-oxidized yarn mechanical property detection method, which uses a mechanical property testing machine to detect the mechanical property of the test bundle; wherein the test bundle is a polyacrylonitrile-based carbon fiber raw yarn bundle or a polyacrylonitrile-based carbon fiber pre-oxidized yarn bundle, which includes the following steps:
[0011] Establishing a tensile test method step: setting detection parameters according to the characteristics of the test bundle to establish a tensile test method for the test bundle; wherein the detection parameters include: the tensile speed of the mechanical property testing machine, the modulus algorithm, the modulus value point range, the data acquisition speed, the test times, the calculation formula of the mechanical property index and the dispersion coefficient; wherein the tensile speed is set to 80-100mm / min, the modulus algorithm is selected as Young's modulus, the modulus value point range is set to 0.1-1.0% of the strain value range, and the data acquisition speed is set to 8-10ms;
[0012] Instrument adjustment and preparation step: adjust the distance between the two clamps on the mechanical property testing machine, and adjust the load and displacement of the mechanical property testing machine to zero;
[0013] Clamping sample and stretching step: clamp the sample on the two clamps, and then make the mechanical property testing machine enter the stretching test process until the sample is broken;
[0014] Repeat the test step: repeat the stretching of multiple samples for each to-be-tested filament according to the above steps, remove invalid samples, keep valid samples, and take the average value as the detection result.
[0015] Preferably, in the establishing tensile test method step: the calculation formula of the mechanical property index and the dispersion coefficient is set according to the provisions of GB / T3362-2005 and GB / T1446; preferably, the mechanical property index includes tensile strength, tensile strength, elongation at break, and tensile modulus.
[0016] Preferably, in the instrument adjustment and preparation step: input the number and cross-sectional area of the to-be-tested filament.
[0017] Preferably, in the repeat test step: 8-10 samples are stretched for each to-be-tested filament.
[0018] Preferably, in the instrument adjustment and preparation step: the maximum force value (selected) of the clamp on the mechanical property testing machine is 1-2KN; preferably, if the maximum force value (selected) of the clamp on the mechanical property testing machine is 1KN, the distance between the two clamps on the mechanical property testing machine is set to 100-200mm, and the effective sample stretching length is 200-300mm; if the maximum force value (selected) of the clamp on the mechanical property testing machine is 2KN, in order to facilitate the comparison of test data with 1KN clamp stretching, the distance between the two clamps on the mechanical property testing machine is set to 20-120mm, so as to ensure that the effective sample stretching length is 200-300mm.
[0019] Preferably, if the K number of the to-be-tested filament is less than or equal to 12K, a clamp with a maximum force value of 1KN is used; if the to-be-tested filament is 24K, a clamp with a maximum force value of 1-2KN is used; if the K number of the to-be-tested filament is greater than 24K, a clamp with a maximum force value greater than or equal to 2KN is used.
[0020] Preferably, the clamp is a pneumatic clamp; preferably, in the instrument adjustment and preparation step: the pressure of the compressed air used by the mechanical property testing machine is set to 0.45-0.60MPa.
[0021] Preferably, the clamp comprises:
[0022] A first clamp block;
[0023] a second clamp block, the first clamp block and the second clamp block being used to clamp the sample; and a groove being further arranged on the second clamp block, so that the sample can be wound on the second clamp block;
[0024] Preferably, the second clamp block is a horn-shaped clamp block, and the groove is arranged on the horn-shaped clamp block and opposite to the clamping surface of the horn-shaped clamp block.
[0025] Preferably, the clamping surface of the first clamp block and the second clamp block is provided with a wear mark perpendicular to the load direction, so as to ensure that the sample has sufficient friction after being clamped and does not slip, and the sample does not break during clamping; preferably, the depth of the wear mark is not more than 0.2 mm.
[0026] Preferably, the two clamps on the mechanical property testing machine are an upper clamp and a lower clamp; in the clamping and stretching step, the operation of clamping the sample includes:
[0027] 1) unwinding a sample with a set length from a wound sample to be measured, pulling one end of the sample between the first clamp block and the second clamp block of the upper clamp, straightening the sample up and down, not moving the upper part, twisting the sample at the lower part, and clamping the first clamp block and the second clamp block of the upper clamp;
[0028] 2) pulling the other end of the sample to the tip of the second clamp block of the lower clamp, clamping the sample with a metal clamp, and twisting the sample counterclockwise by rotating the metal clamp;
[0029] 3) holding the clamping part of the metal clamp, winding the sample in the groove of the second clamp block of the lower clamp first, then winding the sample between the first clamp block and the second clamp block of the lower clamp, maintaining a certain pre-tension on the sample, clamping the lower clamp, and completing the clamping of the sample;
[0030] Preferably, the set length is 350-400 mm.
[0031] Preferably, in the clamping and stretching step, the two clamps are an upper clamp and a lower clamp; in the operation of clamping the sample on the upper clamp and the lower clamp: if the sample to be measured is T300 grade 1K, 3K and 6K sample to be measured, the twist number of the twisted sample is 15-20 twists; if the sample to be measured is T700 grade 6K and 12K sample to be measured, the twist number of the twisted sample is 5-10 twists; if the sample to be measured is T800 grade 6K and 12K sample to be measured, the twist number of the twisted sample is 10-15 twists; if the sample to be measured is 24K and 24K or more sample, the twist number of the twisted sample is 5-10 twists.
[0032] Preferably, the two clamps are respectively an upper clamp and a lower clamp;Wherein, during clamping the sample, when the upper clamp and the lower clamp clamp the sample, the pre-tension of the 1K sample or the 3K sample is not greater than 5N;The pre-tension of the 6K sample or the 12K sample is not greater than 10N;The pre-tension of the 24K sample is not greater than 15N;The pre-tension of the sample above 24K is not greater than 20N.
[0033] Compared with the prior art, the polyacrylonitrile-based carbon fiber precursor and pre-oxidized fiber mechanical property detection method has at least the following beneficial effects:
[0034] In one aspect, the polyacrylonitrile-based carbon fiber precursor and pre-oxidized fiber mechanical property detection method comprises establishing a tensile test method step, an instrument adjustment and preparation step, a sample clamping and stretching step, and a repeated test step. In the establishing a tensile test method step, the tensile speed is set to 80-100mm / min, the modulus algorithm is selected as Young's modulus, the modulus value point range can be initially set to 0.1-1.0% of the strain value range, and the data acquisition speed is set to 8-10ms. In this regard, by setting a wide parameter range (such as the modulus value point range), the instrument collects data within this range, and after the tensile sample is finished, the value range is changed, the value range is gradually reduced and changed, and the value range of the maximum slope is found (which can be compared offline), and finally the modulus value point range suitable for the specifications or characteristics of the precursor and pre-oxidized fiber is determined, and the procedure is standardized. This way can overcome the problem of the prior art that the initial modulus detection method requires finding the point where the strength change with elongation changes the most on the tensile curve and calculating the slope of the tangent line at that point, which is relatively cumbersome. Accurately find the modulus value point range of the corresponding tow. On the other hand, by setting the tensile speed and data acquisition speed to the above range, the detection accuracy can be ensured.
[0035] Further, the polyacrylonitrile-based carbon fiber precursor and pre-oxidized fiber mechanical property detection method according to the embodiments of the present application makes corresponding provisions for the selection of clamps, the twist number when clamping the tow, and the pre-tension of the sample after clamping the sample according to the specifications of the tow to be tested, thereby improving the detection accuracy.
[0036] Further, the polyacrylonitrile-based carbon fiber precursor and pre-oxidized fiber mechanical property detection method according to the embodiments of the present application sets the structure of the clamp, such as the clamping surface of the first clamping block and the second clamping block, which can avoid sample slipping and prevent the sample from breaking during clamping due to deep scratches, thereby achieving rapid detection and improving detection accuracy.
[0037] Further, the application embodiment proposes a mechanical property detection method of polyacrylonitrile-based carbon fiber precursor and pre-oxidized fiber, proposes the operation of clamping the sample (three-step operation), which can further avoid sample slipping, and also avoid the phenomenon of sample breakage in clamping due to too deep grinding marks, so as to realize rapid detection and improve detection accuracy.
[0038] In summary, the embodiment of the application is based on the premise that there is no special mechanical property related detection standard for carbon fiber precursor and pre-oxidized fiber bundle, according to the characteristics of carbon fiber precursor and pre-oxidized fiber bundle, the specific method is proposed from the establishment of the detection method of the tensile speed, modulus algorithm and value point range of the mechanical testing machine, the clamp spacing, the clamping method of the sample and the result calculation of the whole process. Compared with the single filament tensile method, the method has the advantages of simple operation, rapid detection, accurate detection results, small dispersion coefficient and the like, and has promotion value in the industry.
[0039] The above description is only a summary of the technical scheme of the application, in order to more clearly understand the technical means of the application, and can be implemented according to the content of the specification, the following will be described in detail with the preferred embodiment of the application and the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS
[0040] Figure 1 is a schematic diagram of the sample in the upper clamp being clamped and being twisted at the horn tip of the lower clamp in the embodiment of the application;
[0041] Figure 2 is a schematic diagram of the sample being clamped in the upper clamp and the lower clamp in the embodiment of the application;
[0042] Figure 3 is a surface schematic diagram of the first clamp block and the second clamp block in the embodiment of the application;
[0043] Figure 4 is a tensile fracture curve of the sample. DETAILED DESCRIPTION
[0044] In order to further illustrate the technical means and effects adopted by the application to achieve the predetermined invention purpose, the following will be described in detail according to the specific implementation, structure, features and effects of the application, combined with the drawings and the preferred embodiment. In the following description, different "an embodiment" or "embodiments" do not necessarily refer to the same embodiment. In addition, the specific features, structures or characteristics in one or more embodiments can be combined in any suitable form.
[0045] Based on the background art, the applicant has developed a rapid detection method suitable for 1K, 3K, 6K, 12K and 24K polyacrylonitrile-based carbon fiber precursor and pre-oxidized fiber bundle, which has the advantages of simple operation, rapidness, good repeatability, high accuracy and small dispersion coefficient, and is suitable for popularization and use in the industry. Each user can completely use this method, or based on the premise of this method, use the principles of this application (for example, selecting appropriate stretching speed and data acquisition speed, under the premise of not affecting the detection accuracy, trying to improve the detection speed; for example, specifying a unified modulus value method to facilitate data comparability; for example, how to determine the appropriate modulus value point range combined with the characteristics of the sample; for example, the twisting number and clamping method are unified, and the data comparability is stronger), combined with the characteristics of the precursor and pre-oxidized fiber of the enterprise, the modulus value point range can be slightly adjusted to develop a mechanical property detection method of the precursor and pre-oxidized fiber bundle of the enterprise, which can quickly characterize the mechanical properties of the precursor and pre-oxidized fiber, and quickly respond to subsequent process production. For the precursor and pre-oxidized fiber bundle greater than 24K, based on the design concept of this method, under the premise of changing the distance and force value of the clamp, it is also applicable.
[0046] The specific scheme of the present application is as follows:
[0047] The present application provides a mechanical property detection method for polyacrylonitrile-based carbon fiber precursor and pre-oxidized fiber, which uses an isometric elongation universal material testing machine, a matched 1-2KN clamp (horn rope pneumatic clamp), and the position measurement accuracy of the testing machine is ±0.01mm or 0.05% of displacement (taking the larger value). The load measurement accuracy is that the sensor is from the full scale of the force gauge to 1 / 1000 scale, and the accuracy is within ±0.5 of the indicated value; the load and strain measurement channel resolution is 1 / 500000. The method meets the tensile test of 1-24K carbon fiber precursor and pre-oxidized fiber, and adjusting other parameters on the basis of the detection method is also applicable to the tensile test of large bundle carbon fiber precursor and pre-oxidized fiber, which includes the following steps:
[0048] Establishing a tensile test method step: setting detection parameters according to the characteristics of the measured bundle, and establishing a tensile test method for the measured bundle; wherein the detection parameters include: tensile speed of the mechanical property testing machine, modulus algorithm, modulus value point range, data acquisition speed, test times, calculation formula of mechanical property index and dispersion coefficient.
[0049] Wherein, the tensile speed of the mechanical property testing machine is set to 80-100 mm / min; the modulus algorithm is selected to be Young's modulus; the modulus value point is determined according to the grade and linear density of the sample, and is generally between 0.1-1.0% of the strain; the data acquisition speed is determined according to the accuracy requirement, and is generally set to 8-10 ms as the best, the test times are 8-10 times for each sample, and the calculation formula of the mechanical property indexes (such as including tensile strength, tensile strength, elongation at break, tensile modulus) and the dispersion coefficient is set according to the provisions of GB / T3362-2005 and GB / T1446. Preferably, the compressed air pressure of the mechanical property testing machine is set to 0.45-0.60 MPa.
[0050] It should be noted that: the modulus value point range can be set to 0.1-1.0% of the strain value range first, by setting a wider modulus value point range, the instrument collects data in this range, after the tensile sample is finished, the value range is changed, the value range is gradually reduced and changed, so as to find out the value point range of the maximum slope (which can be compared offline), and finally determine the modulus value point range suitable for the specification or characteristics of the raw silk and pre-oxidized silk, and then regulate. Here, see Figure 4 (tensile fracture curve), generally, the modulus refers to: in the vicinity of the origin of Figure 4 , find the point A where the change of strength with elongation is the largest (i.e. the point with the largest tangent angle), and the slope of the tangent line at point A is the initial modulus. The inventor found that for 24K or less tow, the range of 0.1-1.0% of the strain definitely contains the point with the largest slope, and for 24K or more tow, the range of the strain value point can be appropriately increased.
[0051] Instrument adjustment and preparation steps: adjust the distance between the clamps on the mechanical property testing machine, and adjust the load and displacement of the mechanical property testing machine to zero (set the air pressure of the pneumatic clamp, adjust the distance between the upper clamp and the lower clamp, and adjust the load and displacement of the mechanical property testing machine to zero. Input the number and cross-sectional area of the tow to be tested).
[0052] Here, the structure of the clamp (pneumatic clamp) is shown in Figures 1-3The mechanical property testing machine is provided with two clamps, one of which is an upper clamp 1 and the other is a lower clamp 2, and the two clamps are identical in structure. The clamp comprises a first clamping block 3 and a second clamping block 4, wherein the first clamping block 3 and the second clamping block 4 are used for clamping the sample 7, and a groove 43 is further arranged on the second clamping block 4 so that the sample 7 can be wound on the second clamping block 4, wherein the second clamping block 4 is a horn-shaped clamping block, and the groove 43 is located on the entire outer side of the horn-shaped clamping block (the outer side is opposite to the clamping surface 41). Preferably, the clamping surface 31 of the first clamping block 3 and the clamping surface 41 of the second clamping block 4 are provided with uniform and slight scratches perpendicular to the load direction, so as to ensure that the sample 7 has sufficient friction force in the clamp after being clamped, and the sample will not slip in the clamping block, and the sample will not be broken in the clamping due to too deep scratches.
[0053] In this step, for the 1KN clamp, the distance between the upper clamp and the lower clamp is set to 100-200mm. Since the total length of the middle arc-shaped groove on the horn-shaped clamping block is a fixed value, generally the upper clamp and the lower clamp are 50mm, and the total length of the groove on the upper clamp and the lower clamp is 100mm, so the effective sample stretching length is 200-300mm. Further, in order to compare the data of clamps with different force values, for the 2KN clamp, in order to ensure that the effective sample stretching length is 200-300mm, since the total length of the middle arc-shaped groove on the upper horn-shaped clamping block and the lower horn-shaped clamping block is a fixed value, generally 180mm, the distance between the upper clamp and the lower clamp needs to be set to 20-120mm.
[0054] Preferably, for samples below 12K filaments, a 1KN clamp can be used. For 24K samples, both 1KN and 2KN clamps can be used. For samples greater than 24K, it is recommended to use a 2KN or more than 2KN clamp for tensile testing.
[0055] Preferably, the cross-sectional area is obtained by dividing the linear density of the sample by the bulk density.
[0056] Clamping the sample and stretching step: clamp the sample on the clamp, and then make the mechanical property testing machine enter the stretching test process until the sample is broken (i.e. remove the outermost measured filament on the coiled sample to ensure that the sample surface is smooth without hair and hair balls (prepare the sample). Unwind the sample from the coiled sample to a certain length, clamp the sample on the clamp. Press the start key, and the instrument automatically enters the test process until the sample is broken.
[0057] wherein, referring to Figure 1 and Figure 2The process of clamping the sample is as follows: first, about 350-400 mm long sample is unwound from the sample roll, the sample is pulled into the middle of the two clamping blocks of the upper clamp 1 near the sample end, the sample 7 is pulled straight up and down, the upper part is not moved, the sample 7 is twisted at the lower part, and the two clamping blocks are clamped by stepping on the foot switch. The second step: the other end of the sample 7 is pulled to the tip of the second clamping block 4 (horn-shaped clamping block) of the lower clamp 2, the sample 7 is clamped with a metal clamp 6, and the sample is twisted counterclockwise (at this time, the metal clamp is located at the lower side of the second clamp, and at the lower side of the horn-shaped clamping block). The third step: hold the end clamping part of the metal clamp 6, wrap the sample in the groove 43 of the upper clamp and the lower clamp, and then wrap it to the middle of the two clamping blocks of the lower clamp 2, apply a certain pre-tension to the sample with a certain tension, clamp the two clamping blocks by stepping on the foot switch, and the sample clamping is completed.
[0058] Preferably, for T300 grade 1K, 3K and 6K samples, the twisting number is 15-20 twists; for T700 grade 6K, 12K samples, the twisting number is 5-10 twists; for T800 grade 6K, 12K samples, the twisting number is 10-15 twists; for 24K or more bundle samples, the twisting number is 5-10 twists.
[0059] Preferably, the tension of the sample should be controlled during the clamping process of the sample, and after the upper and lower clamps are clamped, the pre-tension of 1K, 3K sample is not more than 5N; the pre-tension of 6K, 12K sample is not more than 10N; the pre-tension of 24K sample is not more than 15N; the pre-tension of 24K or more sample is not more than 20N.
[0060] Preferably, the clamping part of the metal clamp used in the clamping process of the sample should be pre-sticked with medical adhesive tape or other materials with high roughness on the back to increase the friction between the metal clamp and the sample, preventing the sample from slipping in the clamp.
[0061] Preferably, the hand should not touch the detection section of the sample during the clamping process of the sample.
[0062] Repeat the test steps: according to the above steps, repeat the stretching of multiple samples for each sample to be tested, remove the invalid samples, keep the effective samples, and take the average value as the test result (i.e. according to the above steps, repeat the stretching of 8-10 samples for each sample, remove the invalid samples such as slipping, keep 8 effective samples, and take the average value as the test result).
[0063] The inventors of this application, primarily addressing the lack of specialized mechanical property testing methods and standards for carbon fiber precursor and pre-oxidized tow yarns in current carbon fiber companies, aim to propose a highly efficient, accurate, repeatable, and minimally variable tensile testing method to improve the efficiency of testing the mechanical properties of carbon fiber precursor and pre-oxidized tow yarns. Experimental verification has shown the feasibility of this method, which can be used directly or with minor adjustments based on the characteristics of their products, filling a gap in the industry.
[0064] The present invention is further described below by means of specific examples:
[0065] Example 1
[0066] This embodiment is used to test the mechanical properties of polyacrylonitrile-based carbon fiber precursor; wherein the precursor to be tested is a T300 grade carbon fiber 3K precursor sample, and specifically includes the following steps:
[0067] The steps for establishing the tensile test method are as follows: the tensile speed of the mechanical properties testing machine is set to 80 mm / min, the modulus is taken as the Young's modulus algorithm, the modulus value point is set to 0.2-0.6% of the strain value range, the data acquisition speed is set to 10 ms, the number of tests is 10 times, and the calculation formulas of various mechanical properties indicators are set according to the provisions of GB / T3362-2005 and GB / T1446 to establish the tensile test method for T300 grade 3K raw yarn.
[0068] Instrument adjustment and preparation steps: Figure 1 and Figure 2 As shown, connect the gas connection port 5 of the fixtures (upper fixture 1, lower fixture 2) to the compressed air line. Set the compressed air pressure for the fixtures to 0.45 MPa. Adjust the distance between the upper and lower fixtures to 100 mm, and adjust the load and displacement of the testing machine to zero. Select a 1 kN fixture. Enter the sample number 1 and cross-sectional area A.
[0069] Sample clamping and stretching steps: Remove the outermost layer of raw silk from the rolled sample to ensure that the sample surface is smooth and free of hair or lint. Figure 1 and Figure 2As shown, (1) about 350 mm long sample is unwound on the sample roll, the two ends of the sample are pinched by hand, the sample is pulled into the middle of the two clamping blocks (first clamping block 3 and second clamping block 4) of the upper clamp 1, the sample 7 is pulled tight downward at one end, the sample 7 is clamped in the groove 43 of the horn-shaped clamping block (second clamping block 4) at one end, the sample 7 is pulled straight up and down, the upper part is not moved, the sample 7 is twisted at the lower part 8, and the two clamping blocks are clamped by stepping on the foot switch. (2) The other end of the sample is pulled to the tip 42 of the horn-shaped clamping block (second clamping block 4) of the lower clamp 2, the sample 7 is clamped with the metal clamp 6, and the metal clamp is rotated counterclockwise for 15 times to twist 15 times. (3) The end of the metal clamp 6 is gripped, the sample 7 is wound in the groove 43 of the horn-shaped clamping block of the upper clamp 1 and the lower clamp 2, and then wound to the middle of the two clamping blocks of the lower clamp, a certain pre-tension 5N is applied to the original wire, the two clamping blocks are clamped by stepping on the foot switch, and the sample is clamped (the effective length of the sample is 200 mm), as shown. Figure 2 The start key is pressed, and the instrument automatically enters the test process until the sample is broken.
[0070] Repeat the test steps: about 350 mm long sample is unwound according to the above steps, and the sample is stretched for 10 times. No slipping phenomenon occurs in the 10 stretching processes, 10 test data and stretching curves are observed, and no abnormally high or low value is observed. The lowest two samples are removed, 8 effective samples are retained, and the average value is taken as the test result. The test results are shown in Table 1.
[0071] Table 1 Mechanical property test results of 1# sample (T300 / 3K original wire)
[0072]
[0073] Example 2
[0074] This embodiment is used to detect the mechanical properties of polyacrylonitrile-based carbon fiber original wire. The original wire to be tested is a T800 grade 12K original wire sample, which specifically includes the following steps:
[0075] Establishing the tensile test method step: the tensile speed of the mechanical property testing machine is set to 80 mm / min, the modulus is calculated according to the Young's modulus algorithm, the modulus value point is set to 0.3-0.8% of the strain value range, the data acquisition speed is set to 10 ms, the test times are 10, and the calculation formula of each force value is set according to the provisions of GB / T3362-2005 and GB / T1446. The tensile test method of T800 grade 12K original wire is established.
[0076] Instrument adjustment and preparation step: as shown in Figure 1 and Figure 2As shown, connect the gas connection port 5 of the clamp (upper clamp 1, lower clamp 2) to the compressed air pipeline, set the compressed air for the clamp to 0.55 MPa, adjust the distance between the upper clamp 1 and the lower clamp 2; make the distance between the upper clamp 1 and the lower clamp 2 100 mm, and adjust the load and displacement of the testing machine to zero. Among them, the clamp type is 1KN. Input sample number 2 and cross-sectional area B.
[0077] Clamping the sample and the stretching step: remove the outermost original wire on the wound sample to ensure that the sample surface is smooth and free of hair and hair balls. Figure 1 and Figure 2 As shown, (1) unwind about 350 mm long sample from the wound sample, hold both ends of the sample with your hand, pull the sample into the middle of the two clamping blocks (first clamping block 3 and second clamping block 4) of the upper clamp at the upper end of the sample, pull the sample 7 tightly downward with one end, and clamp the sample 7 in the groove 43 of the horn-shaped clamping block (second clamping block 4) with one end, pull the sample 7 straight up and down, and do not move the upper part, twist the sample 7 at the lower part 8, and then press the foot switch to clamp the two clamping blocks tightly. (2) Pull the other end of the sample to the sharp end 42 of the horn-shaped clamping block (second clamping block 4) of the lower clamp 2, clamp the sample 7 with the metal clamp 6, and twist 15 times counterclockwise. (3) Hold the end of the metal clamp 6, wrap the sample 7 in the groove 43 of the horn-shaped clamping block of the upper clamp 1 and the lower clamp 2, and then wrap it to the middle of the two clamping blocks of the lower clamp 2, apply a certain pre-tension 5N to the original wire, press the foot switch to clamp the two clamping blocks tightly, and the sample clamping is completed (the effective length is 200 mm), as shown in Figure 2 Press the start key, and the instrument automatically enters the test process until the sample breaks.
[0078] Repeat the test steps: according to the above steps, repeat the unwinding of about 350 mm long sample, repeat the stretching for 10 times, and there is no slipping phenomenon in the 10 stretching processes. Observe the 10 test data and the stretching curve, remove one slipping value and one minimum, keep 8 effective samples, and take the average value as the test result. The test result is shown in Table 2.
[0079] Table 2 Mechanical property test results of 2# sample (T800 / 12K original wire)
[0080]
[0081] Example 3
[0082] This example is used to detect the mechanical properties of polyacrylonitrile-based carbon fiber pre-oxidized wire; wherein the original wire to be tested is T700 grade carbon fiber 12K pre-oxidized wire sample, which specifically includes the following steps:
[0083] Establishment of tensile test method steps: set the tensile speed of the mechanical property testing machine to 80 mm / min, the modulus to Young's modulus algorithm, the modulus value point to 0.1-0.5% of the strain value range, the data acquisition speed to 10 ms, the test times to 10, and the calculation formula of each force value to be set according to the provisions of GB / T3362-2005 and GB / T1446, and the tensile test method of T800 grade 12K pre-oxidized yarn is established;
[0084] Instrument adjustment and preparation steps: as shown in Figure 1 and Figure 2 , connect the gas connection port 5 of the clamp (upper clamp 1, lower clamp 2) to the compressed air pipeline, set the compressed air for the clamp to 0.50 MPa, adjust the distance between the upper clamp 1 and the lower clamp 2; the distance between the upper clamp 1 and the lower clamp 2 is 100 mm, and the load and displacement of the testing machine are adjusted to zero. Among them, the clamp selection is 1KN. Input sample number 1 and cross-sectional area A.
[0085] Clamping sample and tensile step: remove the outermost original yarn on the wound sample to ensure smooth surface without hair and hair balls. As shown in Figure 1 and Figure 2 , (1) unwind about 350 mm long sample 7 on the wound sample, hold both ends of the sample 7 with your hand, pull the sample into the middle of the two clamping blocks (first clamping block 3 and second clamping block 4) of the upper clamp, pull the sample tightly downward, and clamp the sample in the groove 43 of the horn-shaped clamping block (second clamping block 4), pull the sample straight up and down, and pull the sample at the lower part of the twist 8. Step on the foot switch to clamp the two clamping blocks tightly. (2) pull the other end of the sample to the sharp end 42 of the horn-shaped clamping block (second clamping block 4) of the lower clamp 2, clamp the sample 7 with the metal clamp 6, and rotate the metal clamp counterclockwise 15 times to twist 15 times. (3) hold the end of the metal clamp 6, wrap the sample 7 in the groove 43 of the horn-shaped clamping block of the upper clamp and the lower clamp, and then wrap it to the middle of the two clamping blocks of the lower clamp, apply a certain pre-tension 5N to the original yarn, step on the foot switch to clamp the two clamping blocks tightly, and the sample clamping is completed (the effective length is 200 mm), as shown in Figure 2 . Press the start key, and the instrument automatically enters the test process until the sample breaks.
[0086] Repeat the test steps: according to the above steps, repeat the unwinding of about 350 mm long sample, repeat the tensile test 10 times, and there is no slipping phenomenon in the 10 times of tensile test. Observe the 10 test data, and there is no abnormally high or low value. Remove the lower two samples, keep 8 effective samples, and take the average value as the test result. The test results are shown in Table 3.
[0087] Table 3 Mechanical property test results of 3# sample (T800 / 12K pre-oxidized yarn)
[0088]
[0089] In summary, the scheme of the embodiment of the present application gives a specific mechanical tensile property method of carbon fiber precursor and pre-oxidized fiber bundle, which has the advantages of simple operation, rapidness, good repeatability, small data dispersion coefficient and high accuracy, and is suitable for popularization and use in the industry.
[0090] The above is only the preferred embodiment of the present application, and does not limit the present application in any form. Any simple modification, equivalent change and modification made to the above embodiment according to the technical essence of the present application still belongs to the scope of the technical scheme of the present application.
Claims
1. A method for testing the mechanical properties of polyacrylonitrile-based carbon fiber precursor and pre-oxidized fiber, wherein a mechanical properties testing machine is used to test the mechanical properties of the tested fiber bundle; wherein: The tow yarn to be tested is a polyacrylonitrile-based carbon fiber raw tow yarn or a polyacrylonitrile-based carbon fiber pre-oxidized tow yarn, and is characterized by comprising the following steps: Establishing a tensile test method: setting test parameters according to the characteristics of the tested bundle of wire, and establishing a tensile test method for the tested bundle of wire; wherein the test parameters include: a tensile speed of a mechanical properties testing machine, a modulus algorithm, a modulus value point range, a data acquisition speed, a number of tests, and a calculation formula for a mechanical properties index and a coefficient of dispersion; wherein the tensile speed is set to 80-100 mm / min, the modulus algorithm is selected as Young's modulus, the modulus value point range is set to 0.1-1.0% of the strain value range, and the data acquisition speed is set to 8-10 ms; Instrument adjustment and preparation steps: Adjust the distance between the two fixtures on the mechanical properties testing machine, and adjust the load and displacement of the mechanical properties testing machine to zero; Specimen clamping and stretching steps: The specimen is clamped on two fixtures, and then the mechanical properties testing machine enters the tensile test process until the specimen breaks; Repeat the test steps: Follow the above steps to repeatedly stretch multiple samples for each tow to be tested, remove invalid samples, retain valid samples, and take the average value as the test result; Wherein, in the steps of clamping the sample and stretching, the two clamps are respectively an upper clamp and a lower clamp; wherein, in the operation of clamping the sample on the upper clamp and the lower clamp: if the to-be-tested yarn is a T300-grade 1K, 3K and 6K to-be-tested yarn, the number of twists of the sample is 15-20 twists; if the to-be-tested yarn is a T700-grade 6K and 12K to-be-tested yarn, the number of twists of the sample is 5-10 twists; if the to-be-tested yarn is a T800-grade 6K and 12K to-be-tested yarn, the number of twists of the sample is 10-15 twists; if the to-be-tested yarn is a 24K and above yarn, the number of twists of the sample is 5-10 twists; In the process of clamping the specimen, after the upper and lower fixtures clamp the specimen, the pre-tensioning force for 1K specimens or 3K specimens shall not exceed 5N; the pre-tensioning force for 6K specimens or 12K specimens shall not exceed 10N; the pre-tensioning force for 24K specimens shall not exceed 15N; the pre-tensioning force for specimens above 24K shall not exceed 20N; If the number of K of the wire to be measured is less than or equal to 12K, use a fixture with a maximum force of 1KN; if the number of K of the wire to be measured is 24K, use a fixture with a maximum force of 1-2KN; if the number of K of the wire to be measured is greater than 24K, use a fixture with a maximum force greater than or equal to 2KN; Wherein, the clamp comprises: First clamping block; a second clamping block, the first clamping block and the second clamping block being used to clamp the sample; the second clamping block is further provided with a groove so that the sample can be wound around the second clamping block; Wherein, the second clamping block is a horn-shaped clamping block; the groove is located on the horn-shaped clamping block, and the groove is arranged opposite to the clamping surface of the horn-shaped clamping block; The clamping surfaces of the first and second clamping blocks are provided with wear marks perpendicular to the load direction to ensure that the sample has sufficient friction to prevent slipping after clamping, and to prevent the sample from breaking during clamping; wherein the depth of the wear marks does not exceed 0.2 mm; The two clamps on the mechanical properties testing machine are an upper clamp and a lower clamp respectively; in the sample clamping and stretching steps, the operation of clamping the sample includes: 1) Unwind a sample of a set length from the packaged wire bundle to be tested, pull one end of the sample between the first and second clamps of the upper clamp, straighten the sample up and down, keep the upper part still, twist the sample at the lower twist point, and clamp the first and second clamps of the upper clamp tightly; 2) Pull the other end of the specimen to the tip of the second clamp of the lower fixture, clamp the specimen with a metal clamp, and twist the metal clamp counterclockwise to twist the specimen; 3) Hold the clamping part of the metal clamp tightly, first wrap the specimen around the groove of the second clamping block of the lower clamp, then wrap it between the first clamping block and the second clamping block of the lower clamp, keep applying a certain pre-tension to the specimen, clamp the lower clamp, and the specimen is clamped.
2. The method for detecting mechanical properties of polyacrylonitrile-based carbon fiber precursor and pre-oxidized fiber according to claim 1, characterized in that: In the step of establishing the tensile test method: the calculation formulas for the mechanical performance index and the dispersion coefficient are set according to the provisions of GB / T3362-2005 and GB / T1446.
3. The method for detecting mechanical properties of polyacrylonitrile-based carbon fiber precursor and pre-oxidized fiber according to claim 2, characterized in that: Mechanical performance indicators include tensile strength, tensile strength, elongation at break, and tensile modulus.
4. The method for detecting mechanical properties of polyacrylonitrile-based carbon fiber precursor and pre-oxidized fiber according to claim 1, characterized in that: In the instrument adjustment and preparation step: inputting the number and cross-sectional area of the tow to be measured; and / or In the repeated test step: 8-10 specimens are repeatedly stretched for each tow to be tested.
5. The method for detecting mechanical properties of polyacrylonitrile-based carbon fiber precursor and pre-oxidized fiber according to claim 1, characterized in that: During the instrument setup and preparation steps: The maximum force value of the clamp on the mechanical properties testing machine is 1-2KN.
6. The method for detecting mechanical properties of polyacrylonitrile-based carbon fiber precursor and pre-oxidized fiber according to claim 5, characterized in that: If the maximum force of the clamp on the mechanical properties testing machine is 1KN, the distance between the two clamps on the mechanical properties testing machine is set to 100-200mm, and the effective tensile length of the specimen is 200-300mm; If the maximum force value of the clamp on the mechanical properties testing machine is 2KN, in order to facilitate comparison with the test data of 1KN clamp tension, the distance between the two clamps on the mechanical properties testing machine is set to 20-120mm to ensure that the effective specimen tension length is 200-300mm.
7. The method for detecting mechanical properties of polyacrylonitrile-based carbon fiber precursor and pre-oxidized fiber according to claim 1, characterized in that: The clamp is a pneumatic clamp.
8. The method for detecting mechanical properties of polyacrylonitrile-based carbon fiber precursor and pre-oxidized fiber according to claim 7, characterized in that: In the instrument adjustment and preparation step: the pressure of the compressed air used in the mechanical properties testing machine is set to 0.45-0.60 MPa.
9. The method for detecting mechanical properties of polyacrylonitrile-based carbon fiber precursor and pre-oxidized fiber according to claim 1, characterized in that: The set length is 350-400 mm.