A twisting device and twisting method for testing the tensile properties of multifilament fibers

Abstract

This invention relates to a twisting device and method for testing the tensile properties of multifilament fibers. The device includes a first clamp assembly, a second clamp assembly, a drive mechanism, and a control system. The first clamp assembly includes a first clamp for fixing one end of the multifilament sample to be tested. The second clamp assembly includes a second clamp, which is positioned opposite to the first clamp and is used to fix the other end of the multifilament sample. The drive mechanism is connected to either the first or second clamp assembly to drive the first or second clamp to rotate, thereby twisting the multifilament sample. The control system includes a controller and a twisting parameter setting panel. The controller controls the drive mechanism according to the set twisting parameters. This invention effectively avoids the technical problem of poor fiber tensile property characterization results caused by differences in twisting methods, twist counts, and twisting speeds among different testers.

Description

Technical Field

[0001] This invention relates to the field of polyacrylonitrile-based carbon fiber technology, and in particular to a twisting device and twisting method for testing the tensile properties of multifilament fibers. Background Technology

[0002] Polyacrylonitrile-based carbon fiber is an inorganic fiber material with a carbon content greater than 90%, prepared by high-temperature treatment using PAN precursor (i.e., polyacrylonitrile fiber) as a precursor. Polyacrylonitrile-based carbon fiber possesses properties such as high specific strength, high specific modulus, heat resistance, corrosion resistance, fatigue resistance, creep resistance, radiation resistance, and low relative density, and has been widely used in aerospace, national defense, sports equipment, new energy, medical devices, civil engineering, and rail transportation.

[0003] High-quality polyacrylonitrile (PAC) fiber is the foundation for preparing high-performance PAC-based carbon fiber, and PAC fiber is the key factor determining the final carbon fiber performance. Pre-oxidation of PAC fiber is a crucial process in carbon fiber production; pre-oxidized fiber acts as a bridge between the preceding (PAC fiber) and subsequent (carbon fiber) processes, significantly impacting carbon fiber performance and production efficiency. Therefore, precise testing of various performance indicators of PAC fiber and pre-oxidized fiber is necessary to guide their preparation. Tensile properties are key indicators for PAC fiber and pre-oxidized fiber, including breaking strength, coefficient of variation of breaking strength, elongation at break, coefficient of variation of elongation at break, modulus, and coefficient of variation of modulus.

[0004] Currently, enterprises and research institutions often test single filaments of fibers during scientific research, while testing multifilaments is more suitable for industrial production. GB / T19975-2005, "Test Method for Tensile Properties of High-Strength Fiber Filaments," describes the tensile property testing methods for ultra-high molecular weight polyethylene fibers, aromatic polyamide fibers (aramid), and other high-strength chemical fiber filaments. However, it does not further specify the twisting device, and it lacks detailed and precise regulations on the twist number and twisting method for polyacrylonitrile fibers and pre-oxidized fibers used in carbon fiber preparation, and its specificity is weak. "Factors Affecting the Tensile Properties Testing of Polyacrylonitrile-Based Carbon Fiber Protofilaments" further explores and discusses the test methods of GB / T 19975-2005, but it still does not study the twisting device, and the test object is only 12K polyacrylonitrile fiber. Patent CN202211032386.5, "A Method for Testing the Mechanical Properties of Polyacrylonitrile-Based Carbon Fiber Pre-filaments and Pre-oxidized Fibers," provides a detailed description of the mechanical property testing method for polyacrylonitrile-based carbon fiber pre-filaments and pre-oxidized fibers. However, it still does not describe how to twist or the twisting device. Moreover, this patent only provides a range of twist counts for different grades and K-number fibers, which is relatively broad, without a more detailed and precise description of the twist count. Therefore, the aforementioned multifilament testing methods cannot meet the testing needs of carbon fiber manufacturers.

[0005] With the increasing urgency of demand for differentiated carbon fibers in my country's high-end application fields, the differentiation of polyacrylonitrile fibers and pre-oxidized fibers (such as differences in physicochemical properties) has become particularly important. Differentiated polyacrylonitrile fibers and pre-oxidized fibers require more efficient and accurate tensile property testing methods during the testing process. During tensile property testing, poor fiber bundling in untwisted fibers cannot accurately reflect the maximum breaking force achieved by the concentrated extension of all monofilaments; excessive twisting leads to concentrated fiber breakage at the point of torsion, failing to accurately reflect the fiber's tensile properties; simultaneously, incorrect twisting methods, inaccurate twisting numbers, inconsistent twisting speeds, and poor twisting uniformity can also cause problems such as increased fiber hairiness, some monofilaments in the multifilament being unable to withstand certain tensions, and fiber slippage during the test.

[0006] In summary, existing tests on polyacrylonitrile fibers and pre-oxidized fiber multifilaments have at least the following technical problems:

[0007] (1) Currently, the twisting method is manual twisting and manual counting of twists, as follows: Take a piece of fiber to be tested (the fiber length is greater than the distance between the upper and lower clamps of the tensile testing machine), fix one end of the fiber in the upper clamp, and then use a tool such as a clamp to hold the other end of the fiber, perform manual twisting and manual counting of twists, and finally fix the fiber in the lower clamp for testing.

[0008] However, for manual twisting, different testers and test environments can easily cause differences in manual twisting methods, twist count, twisting speed, etc., which can have a significant impact on fiber tensile properties and fail to accurately reflect the fiber's optimal performance indicators.

[0009] (2) During the testing of polyacrylonitrile fibers and pre-oxidized fibers, more precise and different twisting numbers are required to achieve the best testing results. However, the existing technology has not yet conducted further research on the twisting numbers, thus failing to achieve the best testing results. Summary of the Invention

[0010] In view of this, the present invention provides a twisting device and twisting method for testing the tensile properties of multifilament fibers. The main purpose is to effectively avoid the problem of poor fiber tensile property characterization results caused by differences in twisting methods, twisting number, twisting speed, etc. among different testers.

[0011] To achieve the above objectives, the present invention mainly provides the following technical solutions:

[0012] On one hand, embodiments of the present invention provide a twisting device for testing the tensile properties of multifilament fibers, comprising:

[0013] A first clamping assembly, comprising a first clamp; the first clamp being used to fix one end of the fiber multifilament sample to be tested;

[0014] The second clamp assembly includes a second clamp; the second clamp and the first clamp are disposed opposite to each other, and the second clamp is used to fix the other end of the fiber multifilament sample to be tested;

[0015] A driving mechanism is connected to the first clamp assembly or the second clamp assembly to drive the first clamp or the second clamp to rotate in order to twist the fiber multifilament sample to be tested.

[0016] The control system includes a controller and a twisting parameter setting panel; the controller is connected to the twisting parameter setting panel and to the drive mechanism; wherein the controller controls the drive mechanism according to the set twisting parameters.

[0017] Preferably, the driving mechanism is drivenly connected to the first clamp; wherein, the first clamp assembly includes:

[0018] First base;

[0019] A turntable structure, comprising a turntable and a support; wherein the support is mounted on a first base, the turntable is mounted on the support, and the turntable is rotatable relative to the support;

[0020] A first clamp fixing bracket is mounted on a turntable at one end; the first clamp is fixed to the other end of the first clamp fixing bracket.

[0021] The driving mechanism is connected to the turntable structure and is used to drive the turntable, the first clamp fixing bracket, and the first clamp to rotate.

[0022] Preferably, the turntable is provided with scale values.

[0023] Preferably, the first clamping assembly is a lower clamping assembly and the second clamping assembly is an upper clamping assembly;

[0024] Preferably, the second clamping assembly includes:

[0025] Second base;

[0026] The second clamp fixing bracket has one end mounted on the second base; the second clamp is fixed on the other end of the second clamp fixing bracket.

[0027] Preferably, a transmission mechanism is provided inside the support; wherein, the driving mechanism is driven connected to the transmission mechanism; the transmission mechanism is driven connected to the turntable; preferably, a groove is provided on the support, and a central shaft is provided in the groove; the transmission mechanism is mounted on the central shaft; the turntable is rotatably connected to the central shaft; preferably, the transmission mechanism includes a first gear; a second gear is provided on the turntable; wherein, the first gear and the second gear mesh.

[0028] Preferably, the twisting parameters include the number of twists, and more preferably, the twisting speed.

[0029] Preferably, the controller is located within the twisting parameter setting panel.

[0030] Preferably, the number of twists is less than or equal to 0.1 twists, and more preferably, the number of twists is accurate to 0.1 twists (i.e., the number of twists is accurate to 0.1 twists).

[0031] Preferably, the driving mechanism is a servo motor; preferably, by setting the twist number on the twisting parameter setting panel, the controller converts the set twist number into a corresponding number of pulses, controls the number of rotations of the servo motor, and thus twists the fiber multifilament sample to be tested to the set twist number.

[0032] On the other hand, embodiments of the present invention provide a fiber multifilament tensile performance testing device, wherein the fiber multifilament tensile performance testing device includes the fiber multifilament tensile performance testing twisting device described in any of the above claims.

[0033] In another aspect, embodiments of the present invention provide a twisting method for testing the tensile properties of multifilament fibers, wherein the method includes the following steps:

[0034] Calculate the twist number: Calculate the twist number of the multifilament sample to be tested;

[0035] Twisting: The fiber multifilament sample to be tested is twisted using the twisting device for testing the tensile properties of fiber multifilament as described in any of the above-mentioned methods.

[0036] Preferably, when the fiber multifilament is a polyacrylonitrile fiber multifilament or a polyacrylonitrile-based pre-oxidized fiber multifilament, in the step of calculating the twist number, the twist number of the fiber multifilament sample to be tested is calculated according to the following formula:

[0037] z = 9.25 × e (-0.74×x) ×y;

[0038] Where x represents the linear density of the multifilament fiber to be tested, in g / m;

[0039] y represents the bulk density of the multifilament fiber being tested, in g / cm³. 3 ;

[0040] z represents the number of twists, measured in twists per 100mm.

[0041] Preferably, the twisting step includes:

[0042] 1) Fix both ends of the fiber multifilament sample to be tested onto the first clamp and the second clamp of the fiber multifilament tensile property testing twisting device, respectively;

[0043] 2) Set the twisting parameters on the twisting parameter setting panel of the fiber multifilament tensile performance testing twisting device; wherein, the twisting parameters include the number of twists, and preferably also include the twisting speed; wherein, the twisting speed is characterized by the rotational speed of the turntable; preferably, the rotational speed of the turntable is 0.1-1 r / s (it should be noted here: the controller uses the speed adjustment knob to adjust the pulse frequency of the servo motor so that the turntable speed is within a reasonable range (0.1-1 r / s), the set number of twists is converted into the number of pulses by the controller, and the number of rotations of the given motor drives the turntable to rotate to the same value as the set number of twists. If the speed is too fast, it will damage the yarn and also cause uneven twisting on the fiber; if the speed is too slow, the twisting efficiency will be low).

[0044] 3) Start the automatic twisting operation. The controller of the fiber multifilament tensile performance testing twisting device controls the drive mechanism to drive the first clamp or the second clamp to rotate according to the set twisting parameters, so as to twist the fiber multifilament sample to be tested to the required number of twists.

[0045] In another aspect, embodiments of the present invention provide a method for testing the tensile properties of multifilament fibers, which includes the following steps:

[0046] After twisting the fiber multifilament sample to be tested using the above-mentioned twisting method for testing the tensile properties of fiber multifilament, the tensile properties of the fiber multifilament sample to be tested are then tested.

[0047] Compared with the prior art, the twisting device and twisting method for testing the tensile properties of multifilament fibers of the present invention have at least the following beneficial effects:

[0048] On the one hand, the fiber multifilament tensile property testing twisting device provided in this embodiment of the invention, based on the first clamp assembly and the second clamp assembly, incorporates a drive mechanism and a control system. The control system includes a controller and a twisting parameter setting panel. The controller controls the drive mechanism according to the set twisting parameters, and the drive mechanism controls the rotation of the first or second clamp to twist the fiber multifilament sample. In the specific testing process, the twisting parameters only need to be set on the twisting parameter setting panel. Therefore, with simple operation, automatic twisting of the fiber multifilament sample to be tested can be achieved, resulting in high twisting accuracy and effectively avoiding the problem of "poor fiber tensile property characterization results caused by differences in twisting methods, twist numbers, twisting speeds, etc., among different testers".

[0049] On the other hand, the twisting method for testing the tensile properties of multifilaments provided in this embodiment of the invention uses the above-mentioned device for twisting, and therefore has the above-mentioned beneficial effects, which will not be repeated here.

[0050] Furthermore, the twisting method for testing the tensile properties of multifilament fibers provided in this embodiment of the invention proposes for the first time to calculate the twist number z based on the linear density x and bulk density y of the fiber to be tested using the formula: z = 9.25 × e (-0.74×x) ×y. Based on this formula, different twist counts are applied to differentiated polyacrylonitrile fibers and pre-oxidized fibers, thus avoiding problems such as concentrated fiber breakage at twist points, some monofilaments in multifilaments being unable to withstand certain tensions, and fiber slippage caused by improper twist count settings. This allows for obtaining optimal test results that accurately reflect the fiber's tensile properties, ensuring reliable test data. Here, the above formula uses the linear density and bulk density of the fiber under test to calculate the twist count. Compared to the traditional method of applying twist counts based on different K-number fibers, this method provides more accurate test results, precisely reflecting the fiber's optimal performance indicators.

[0051] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, the preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings. Attached Figure Description

[0052] Figure 1 This is a schematic diagram of a twisting device for testing the tensile properties of multifilament fibers provided in an embodiment of the present invention. Detailed Implementation

[0053] To further illustrate the technical means and effects adopted by the present invention to achieve the intended purpose, the specific embodiments, structures, features, and effects according to the present invention will be described in detail below with reference to the accompanying drawings and preferred embodiments. In the following description, different "an embodiment" or "an embodiment" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics in one or more embodiments can be combined in any suitable form.

[0054] On the one hand, this invention mainly addresses the problem that "differences in twisting methods, twist counts, and twisting speeds among different testers during tensile property testing of polyacrylonitrile fibers and pre-oxidized fibers lead to poor fiber tensile property characterization results." This invention provides a highly efficient and precise twisting device and method for testing the tensile properties of multifilament fibers, suitable for testing the tensile properties of polyacrylonitrile fibers and pre-oxidized fibers with different tow specifications (1K, 3K, 6K, 12K, 24K, etc.) and different linear densities of the same tow specification during industrial production.

[0055] Furthermore, it should be noted that as the pre-oxidation process of polyacrylonitrile fibers progresses, the grooves on the fiber surface gradually narrow, and the cyclization and cross-linking of macromolecules continuously increase the degree of densification, resulting in a higher bulk density. Simultaneously, the fiber surface absorbs moisture from the air during pre-oxidation, leading to an increase in surface moisture content. These factors combined result in reduced inter-fiber friction during tensile property testing of pre-oxidized fibers at different stages, making slippage and other problems more likely to occur. Therefore, in the mechanical property testing of polyacrylonitrile fibers and pre-oxidized fibers, more precise twisting with varying numbers of twists is required to achieve optimal testing results.

[0056] To achieve the above objectives, the present invention mainly provides the following technical solutions, as detailed in the following embodiments.

[0057] Example 1

[0058] This embodiment mainly provides a twisting device for testing the tensile properties of multifilament fibers, such as... Figure 1As shown, the fiber multifilament tensile property testing twisting device of this embodiment includes: a first clamp assembly, a second clamp assembly, a drive mechanism 9, and a control system. The first clamp assembly includes a first clamp 3, which is used to fix one end of the fiber multifilament sample 1 to be tested. The second clamp assembly includes a second clamp 2, which is disposed opposite to the first clamp 3 and is used to fix the other end of the fiber multifilament sample 1 to be tested. The drive mechanism 9 is drivenly connected to the first clamp assembly or the second clamp assembly to drive the first clamp 3 or the second clamp 2 to rotate, thereby twisting the fiber multifilament sample 1 to be tested. The control system includes a controller and a twisting parameter setting panel 10; the controller is connected to the twisting parameter setting panel 10 and the drive mechanism 9. The controller controls the drive mechanism 9 according to the set twisting parameters.

[0059] The fiber multifilament tensile property testing twisting device provided in this embodiment, based on the first clamp assembly and the second clamp assembly, incorporates a drive mechanism 9 and a control system. The control system includes a controller and a twisting parameter setting panel 10. The controller controls the drive mechanism 9 according to the set twisting parameters, and the drive mechanism controls the rotation of the first or second clamp to twist the fiber multifilament sample. In the specific testing process, the twisting parameters only need to be set on the twisting parameter setting panel 10. Therefore, automatic twisting of the fiber multifilament sample to be tested can be achieved with simple operation, resulting in high twisting accuracy and effectively avoiding the problem of "poor fiber tensile property characterization results caused by differences in twisting methods, twist numbers, twisting speeds, etc. among different testers".

[0060] Example 2

[0061] Preferably, this embodiment provides a twisting device for testing the tensile properties of multifilament fibers, such as... Figure 1 As shown, this embodiment is further designed based on embodiment 1 as follows:

[0062] In this embodiment, the driving mechanism 9 is drivenly connected to the first clamp 3. The first clamp assembly includes a first base 7, a turntable structure 8, and a first clamp fixing bracket 5. The turntable structure 8 includes a support 82 and a turntable 81. The support 82 is mounted on the first base 7, and the turntable 81 is mounted on the support 82 and can rotate relative to the support 82. One end of the first clamp fixing bracket 5 is mounted on the turntable 81 (the first clamp fixing bracket 5 is fixed to the turntable 81 by screws); the first clamp 3 is fixed to the other end of the first clamp fixing bracket 5. The driving mechanism 9 is drivenly connected to the turntable structure 8 and is used to drive the turntable 81, the first clamp fixing bracket 5, and the first clamp 3 to rotate.

[0063] Preferably, a transmission mechanism is provided within the support 82; wherein, the drive mechanism 9 is driven connected to the transmission mechanism; the transmission mechanism is driven connected to the turntable 81. In a preferred embodiment, the support 82 has a groove, and a central shaft is disposed within the groove; the transmission mechanism is mounted on the central shaft; the turntable 81 is rotatably connected to the central shaft. Preferably, the transmission mechanism includes a first gear; a second gear is disposed on the turntable; wherein the first gear and the second gear mesh. Preferably, the transmission structure can be configured as a worm gear structure.

[0064] Preferably, the turntable 81 is provided with a scale value; here, the turntable is provided with a real-time angle scale value, which displays the number of degrees the turntable has rotated, allowing for visual observation of the turntable's rotation position; observing the rotation speed, providing a relative coordinate; after the scale is returned to zero, it can be determined that the upper and lower clamps are aligned.

[0065] Preferably, the first clamping assembly is a lower clamping assembly and the second clamping assembly is an upper clamping assembly.

[0066] Preferably, the second clamp assembly includes: a second base 6 and a second clamp fixing bracket 4; wherein one end of the second clamp fixing bracket 4 is mounted on the second base 6; and the second clamp 2 is fixed on the other end of the second clamp fixing bracket 4.

[0067] In this embodiment, the drive mechanism controls the first clamp with a simple structure, thereby achieving automatic twisting.

[0068] Example 3

[0069] Preferably, this embodiment provides a twisting device for testing the tensile properties of multifilament fibers, such as... Figure 1 As shown, this embodiment further incorporates the following design features based on the aforementioned embodiments:

[0070] The twisting parameters that can be set on the twisting parameter setting panel 10 include the number of twists and the twisting speed. The number of twists is accurate to 0.1 twists.

[0071] Here, a servo motor is used as the drive mechanism 9. The controller is located within the twisting parameter setting panel 10. The twisting parameter setting panel 10 has a twist number setting and display for setting and displaying the set twist number. The twisting parameter setting panel 10 also has a speed adjustment button for setting the twisting speed. The speed adjustment button can adjust the pulse frequency of the servo motor 9 so that the speed of the servo motor 9 is within the corresponding range. Different twist numbers are set on the twisting parameter setting panel 10, and the controller converts them into pulse numbers. The servo motor 9 is given the number of revolutions to rotate, and the servo motor 9 drives the turntable 81 to rotate to the same value as the set twist number. The turntable 81 and the twisting parameter setting panel 10 display the real-time rotation angle of the turntable.

[0072] In addition, the controller is installed inside the twisting parameter setting panel 10.

[0073] In addition, the twist parameter setting panel 10 is also equipped with a main switch, a twist count zeroing button, and start and stop buttons.

[0074] In summary, the fiber multifilament tensile property testing twisting device provided in the above embodiments is simple to operate and has high twisting accuracy; it can effectively avoid the problem of poor fiber tensile property characterization results caused by differences in twisting methods, twist numbers, and twisting speeds among different testers. The fiber multifilament tensile property testing twisting device provided in the above embodiments is not only suitable for tensile property testing of polyacrylonitrile fibers and pre-oxidized fibers, but also suitable for tensile property testing of other high-strength fibers.

[0075] Example 4

[0076] On the other hand, this embodiment provides a fiber multifilament tensile performance testing device, wherein the fiber multifilament tensile performance testing device includes the fiber multifilament tensile performance testing twisting device described in any of the above embodiments.

[0077] The fiber multifilament tensile performance testing device provided in this embodiment has the advantages of simple operation and high twisting accuracy because it adopts the fiber multifilament tensile performance testing twisting device described in any of the above embodiments. At the same time, it can effectively avoid the problem of poor fiber tensile performance characterization results caused by differences in twisting method, twist number, twisting speed and other factors among different testers.

[0078] Example 5

[0079] In another aspect, embodiments of the present invention provide a twisting method for testing the tensile properties of multifilament fibers, wherein the method includes the following steps:

[0080] Calculate the twist number: Calculate the twist number of the multifilament sample to be tested.

[0081] Twisting: The fiber multifilament sample to be tested is twisted using the twisting device for testing the tensile properties of fiber multifilaments described in any of the above embodiments.

[0082] Preferably, the fiber multifilament is a polyacrylonitrile fiber multifilament or a polyacrylonitrile-based pre-oxidized fiber multifilament.

[0083] Preferably, in the step of calculating the twist number, the twist number of the multifilament sample to be tested is calculated according to the following formula:

[0084] z = 9.25 × e (-0.74×x) ×y;

[0085] Where x represents the linear density of the multifilament fiber to be tested, in g / m;

[0086] y represents the bulk density of the multifilament fiber being tested, in g / cm³. 3 ;

[0087] z represents the number of twists, measured in twists per 100mm.

[0088] Here, the formula is explained as follows: (1) The twisting method for testing the tensile properties of multifilament fibers provided in this embodiment provides different twisting numbers for differentiated polyacrylonitrile fibers and pre-oxidized fibers. This avoids problems such as concentrated fiber breakage at the point of torsion, some monofilaments in the multifilament being unable to withstand a certain tension, and fiber slippage. As a result, the best test results can be obtained, which truly reflects the tensile properties of the fibers and the test data is reliable. (2) Compared with the prior art, this embodiment uses the linear density and bulk density of the fiber to be tested to calculate the twisting number for the first time. Compared with the traditional method of implementing the twisting number based on different K-number fibers, the calculation formula of this embodiment makes the test results more accurate and can accurately reflect the best performance indicators of the fiber.

[0089] Preferably, the twisting step includes:

[0090] 1) Fix both ends of the fiber multifilament sample to be tested onto the first clamp and the second clamp of the fiber multifilament tensile property testing twisting device, respectively.

[0091] 2) Set the twisting parameters on the twisting parameter setting panel of the fiber multifilament tensile property testing twisting device; wherein, the twisting parameters include the number of twists, and preferably also the twisting speed; wherein, the twisting speed is characterized by the rotational speed of the turntable; preferably, the rotational speed of the turntable is 0.1-1 r / s. It should be noted that: the controller uses a speed adjustment knob to adjust the pulse frequency of the servo motor, so that the turntable speed is within a reasonable range (0.1-1 r / s). The set number of twists is converted into a pulse number by the controller, and the number of rotations of the given motor drives the turntable to rotate to the same value as the set number of twists. If the speed is too high, it will damage the yarn and cause uneven twisting on the fiber; if the speed is too slow, the twisting efficiency will be low. Figure 1 As shown, input the calculated twist number z into the twisting parameter setting panel 10; set the corresponding twisting speed using the speed adjustment button.

[0092] 3) Start the automatic twisting operation. The controller of the fiber multifilament tensile performance test twisting device controls the drive mechanism to drive the first or second clamp to rotate according to the set twisting parameters, so as to twist the fiber multifilament sample to be tested to the required number of twists.

[0093] Example 6

[0094] Furthermore, this embodiment provides a method for testing the tensile properties of multifilament fibers, which includes the following steps:

[0095] The fiber multifilament sample to be tested was twisted using the twisting method of Example 5 for testing the tensile properties of multifilaments, and then the tensile properties of the fiber multifilament sample to be tested were tested.

[0096] The fiber multifilament tensile performance testing method provided in this embodiment, due to the adoption of the fiber multifilament tensile performance testing twisting method described in Example 5, has the advantages of simple operation and high twisting accuracy. It also effectively avoids the problem of poor fiber tensile performance characterization results caused by differences in twisting methods, twist counts, and twisting speeds among different testers. Furthermore, because the twist count is precisely determined, the test results are more accurate and can accurately reflect the optimal performance indicators of the fiber.

[0097] The following specific experimental examples further illustrate this point:

[0098] Experimental Example 1

[0099] This experimental example is used to test the tensile properties of polyacrylonitrile fibers. The fiber tested was 3K polyacrylonitrile fiber with a linear density of 0.37 g / m and a bulk density of 1.19 g / cm³. 3 The fiber to be tested is a coaxial fiber with Comparative Example 1-1. The specific steps include:

[0100] This invention provides the first proposed formula for calculating the number of twists: z = 9.25 × e (-0.74×x) Calculate the twist number using the formula x = y. Based on the linear density of the fiber to be tested, x = 0.37 g / m³, and the bulk density, y = 1.19 g / cm³. 3 The number of twists is calculated to be z = 8.4 twists.

[0101] Automatic twisting is performed using the fiber multifilament tensile property testing twisting device provided in this embodiment of the invention, such as... Figure 1 As shown, the main steps are as follows: Turn on the switch of the twisting parameter setting panel 10 to start the setting panel, and press the zeroing button to zero the data. Set the twisting number to 8.4 twists on the twisting parameter setting panel 10, which is converted into pulse count by the controller. This sets the number of rotations of the drive mechanism 9 (a fixed servo motor), causing the drive mechanism 9 to drive the turntable 81 to rotate 8.4 times. Rotate the speed adjustment button to set the twisting speed. The controller adjusts the pulse frequency of the drive mechanism 9 through the speed adjustment button to keep the speed of the drive mechanism 9 within the corresponding range.

[0102] Tensile properties were tested on the fiber multifilament samples to be tested. Ten samples were repeatedly stretched, the two lowest-performing samples were removed, and the eight valid samples were retained. The average value was taken as the test result. The test results are shown in Table 1.

[0103] Comparative Example 1-1

[0104] This comparative example was used to test the tensile properties of polyacrylonitrile fibers. The fiber tested was 3K polyacrylonitrile fiber with a linear density of 0.37 g / m and a bulk density of 1.19 g / cm³. 3 The fiber to be tested is a coaxial fiber with that in Experimental Example 1. The specific steps include:

[0105] Tester A takes a section of 3K polyacrylonitrile fiber to be tested (the fiber length is greater than the distance between the upper and lower clamps of the tensile testing machine), fixes one end of the fiber in the upper clamp, and then uses a tool such as a clamp to hold the other end of the fiber manually to perform manual twisting. The twist number is 8 twists (according to the formula provided by this invention, the twist number is 8.4 twists, but manual twisting cannot be accurate to 8.4 twists, so 8 twists are used), and performs tensile performance testing on it.

[0106] Ten specimens were subjected to repeated stretching. The two lowest-performing specimens were removed, and eight valid specimens were retained. The average value was taken as the test result. The test results are shown in Table 1.

[0107] Comparative Examples 1-2

[0108] This comparative example is used to test the tensile properties of polyacrylonitrile fibers. The fiber under test is a coaxial fiber, similar to that in Comparative Example 1-1. The specific steps include:

[0109] Tester B repeated the operating steps of tester A in Comparative Example 1-1, and the test results are shown in Table 1.

[0110] Table 1 Tensile properties of 3K polyacrylonitrile fiber multifilament

[0111]

[0112] According to the test results in Table 1:

[0113] (1) Comparative Examples 1-1 and 1-2 show that the tensile performance test results of different testers vary greatly.

[0114] (2) Experimental Example 1 uses the fiber multifilament tensile performance testing twisting device and twisting method proposed in the present invention. It can be seen that Experimental Example 1 can effectively avoid the problem of inconsistent fiber tensile performance characterization results caused by different twisting methods, twisting number, twisting speed and other factors of different testers, and the fiber test results have a small coefficient of variation.

[0115] The following experimental example 2 and comparative example 2 demonstrate that the twist number calculation formula z = 9.25 × e proposed in this invention embodiment is used to prove that the twist number calculation formula is as follows: (-0.74×x) ×y can more accurately determine the twist number, making the test results more precise and able to accurately reflect the fiber's optimal performance indicators.

[0116] Experimental Example 2

[0117] This example demonstrates the testing of the tensile properties of polyacrylonitrile fibers. The fiber tested was 12K polyacrylonitrile fiber with a linear density of 1.57 g / m and a bulk density of 1.18 g / cm³. 3 The fiber under test and Comparative Example 2 are coaxial fibers. The specific steps include:

[0118] Using the twisting method for testing the tensile properties of multifilaments proposed in this invention, the formula z = 9.25 × e is applied. (-0.74×x) Calculate the twist number using the formula xy. Based on the fiber linear density x = 1.57 g / m and bulk density y = 1.18 g / cm³,... 3 The number of twists is calculated to be z = 3.4 twists.

[0119] Twisting is performed using the fiber multifilament tensile property testing twisting device provided in the above embodiment, and the steps are as follows: Figure 1 As shown, turn on the switch of the twisting parameter setting panel 10 to start the setting panel, and press the zeroing button to zero the data. Set the twisting number to 3.4 twists on the twisting parameter setting panel 10. The controller converts this into a pulse count, which is used to give the drive mechanism 9 (a fixed servo motor) the number of revolutions. The drive mechanism 9 drives the turntable 81 to rotate 3.4 revolutions. Rotate the speed adjustment button to set the twisting speed. The controller adjusts the pulse frequency of the drive mechanism 9 through the speed adjustment button to keep the speed of the drive mechanism 9 within the corresponding range.

[0120] Ten specimens were subjected to repeated stretching. The two lowest-performing specimens were removed, and eight valid specimens were retained. The average value was taken as the test result. The test results are shown in Table 2.

[0121] Comparative Example 2

[0122] This comparative example was used to test the tensile properties of polyacrylonitrile fibers. The fiber tested was 12K polyacrylonitrile fiber with a linear density of 1.57 g / m and a bulk density of 1.18 g / cm³. 3 The fiber to be tested is a coaxial fiber with that in Experimental Example 2. The specific steps differ from those in Experimental Example 2 in that:

[0123] Comparative Example 2 did not use the calculation formula proposed in the embodiments of the present invention (z = 9.25 × e). (-0.74×x)Instead of calculating the twist number using ×y), the conventional technique was used to determine the twist number based on the K number of the polyacrylonitrile fiber, which was set to 7 twists. The twist number was then set to 7 twists on the twisting parameter setting panel 10. All other steps were the same, and the test results are shown in Table 2.

[0124] Table 2 Tensile properties of 12K polyacrylonitrile fiber multifilament

[0125]

[0126] By comparing the test results of Comparative Example 2 and Experimental Example 2 in Table 2, it can be seen that the tensile properties of multifilament are closely related to the twist number. The accurate twist number can well reflect the maximum breaking force value reached by the concentrated extension of all monofilaments, avoid the occurrence of concentrated breakage of fibers at the torsion point, and accurately reflect the best performance index of the fiber.

[0127] The following experimental example 3 and comparative example 3 demonstrate that the twist number calculation formula z = 9.25 × e proposed in this invention embodiment is used to prove that the twist number calculation formula is as follows: (-0.74×x) ×y can more accurately determine the twist number, making the test results more precise and able to accurately reflect the fiber's optimal performance indicators.

[0128] Experimental Example 3

[0129] This embodiment is used to test the tensile properties of polyacrylonitrile-based pre-oxidized fibers. The fiber to be tested is 6K polyacrylonitrile-based pre-oxidized fiber with a linear density of 0.78 g / m and a bulk density of 1.36 g / cm³. 3 The fiber under test and Comparative Example 3 are coaxial fibers. The specific steps include:

[0130] The twist number calculation formula z = 9.25 × e, first proposed in this embodiment of the invention, is used. (-0.74×x) Calculate the twist number using the formula xy. Based on the fiber linear density x = 0.78 g / m and bulk density y = 1.36 g / cm³,... 3 The number of twists is calculated to be z = 7.1 twists.

[0131] Using the fiber multifilament tensile performance testing twisting device proposed in this embodiment of the invention, the twisting parameter setting panel 10 was set to 7.1 twists, and then the tensile performance was tested. The test results are shown in Table 3.

[0132] Comparative Example 3

[0133] This comparative example was used to test the tensile properties of polyacrylonitrile-based pre-oxidized fibers. The fiber tested was 6K polyacrylonitrile-based pre-oxidized fiber with a linear density of 0.78 g / m and a bulk density of 1.36 g / cm³. 3The fiber to be tested is a coaxial fiber, similar to that in Experimental Example 3. The specific steps differ from those in Experimental Example 3 in that:

[0134] The automatic twisting was performed using only the fiber multifilament tensile property testing twisting device proposed in this embodiment of the invention, without employing the calculation formula (z = 9.25 × e) proposed in this embodiment of the invention. (-0.74×x) Instead of calculating the twist number using ×y), the conventional technique was used to determine the twist number based on the K number of the polyacrylonitrile-based pre-oxidized fiber, which was set to 4 twists. The twist number was set to 4 twists on the twisting parameter setting panel 10, and the test results are shown in Table 3.

[0135] Table 3 Tensile properties of 6K polyacrylonitrile-based pre-oxidized fiber multifilament

[0136]

[0137] By comparing the test results of Comparative Example 3 and Experimental Example 3 in Table 3, it can be seen that: the precise twist count can well reflect the maximum breaking force value achieved by the concentrated extension of all monofilaments, avoid the occurrence of fiber slippage and other phenomena, and accurately reflect the best performance indicators of the fiber.

[0138] In summary, the fiber multifilament tensile performance testing twisting device and twisting method proposed in this embodiment of the invention can automatically twist the fiber multifilament sample to be tested with simple operation, resulting in high twisting accuracy and effectively avoiding the problem of "poor fiber tensile performance characterization results caused by differences in twisting method, twist number, twisting speed, etc. among different testers".

[0139] Furthermore, the twist calculation formula proposed in this embodiment of the invention provides different twist numbers for differentiated polyacrylonitrile fibers and pre-oxidized fibers, thereby avoiding problems such as concentrated fiber breakage at twist points, some monofilaments in multifilaments being unable to withstand certain tension, and fiber slippage due to improper twist setting. This allows for obtaining optimal test results, truly reflecting the fiber tensile properties, and ensuring reliable test data. Here, the twist calculation formula proposed in this embodiment of the invention uses the linear density and bulk density of the fiber under test to calculate the twist number. Compared to the traditional method of calculating the twist number based on different K-number fibers, this results in more accurate test results, accurately reflecting the fiber's optimal performance indicators.

[0140] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A twisting method for testing the tensile properties of multifilament fibers, characterized in that, The method includes the following steps: Calculate the twist number: Calculate the twist number of the multifilament sample to be tested; Twisting: The fiber multifilament sample to be tested is twisted using a twisting device for testing the tensile properties of multifilaments; Among them, the fiber multifilament is polyacrylonitrile fiber multifilament or polyacrylonitrile-based pre-oxidized fiber multifilament; In the step of calculating the twist count, the twist count of the multifilament sample to be tested is calculated according to the following formula: z=9.25×e (-0.74×x) ×y; Where x represents the linear density of the multifilament fiber to be tested, in g / m; y represents the bulk density of the multifilament fiber being tested, in g / cm³. z represents the number of twists, and the unit is twists / 100mm; The twisting device for testing the tensile properties of multifilament fibers includes: A first clamping assembly, comprising a first clamp; the first clamp being used to fix one end of the fiber multifilament sample to be tested; The second clamp assembly includes a second clamp; the second clamp and the first clamp are disposed opposite to each other, and the second clamp is used to fix the other end of the fiber multifilament sample to be tested; A driving mechanism is connected to the first clamp assembly or the second clamp assembly to drive the first clamp or the second clamp to rotate in order to twist the fiber multifilament sample to be tested. The control system includes a controller and a twisting parameter setting panel; the controller is connected to the twisting parameter setting panel and to the drive mechanism; wherein the controller controls the drive mechanism according to the set twisting parameters.

2. The twisting method for testing the tensile properties of multifilament fibers according to claim 1, characterized in that, The driving mechanism is driven by the first clamp; wherein the first clamp assembly includes: First base; A turntable structure, comprising a turntable and a support; wherein the support is mounted on a first base, the turntable is mounted on the support, and the turntable is rotatable relative to the support; A first clamp fixing bracket is mounted on a turntable at one end; the first clamp is fixed to the other end of the first clamp fixing bracket. The driving mechanism is connected to the turntable structure and is used to drive the turntable, the first clamp fixing bracket, and the first clamp to rotate.

3. The twisting method for testing the tensile properties of multifilament fibers according to claim 2, characterized in that, The turntable is equipped with scale values.

4. The twisting method for testing the tensile properties of multifilament fibers according to claim 2, characterized in that, The first clamping assembly is a lower clamping assembly, and the second clamping assembly is an upper clamping assembly.

5. The twisting method for testing the tensile properties of multifilament fibers according to claim 2, characterized in that, The second clamping assembly includes: Second base; The second clamp fixing bracket has one end mounted on the second base; the second clamp is fixed on the other end of the second clamp fixing bracket.

6. The twisting method for testing the tensile properties of multifilament fibers according to claim 2, characterized in that, The support is provided with a transmission mechanism; wherein, the drive mechanism is drivenly connected to the transmission mechanism; and the transmission mechanism is drivenly connected to the turntable.

7. The twisting method for testing the tensile properties of multifilament fibers according to claim 6, characterized in that, The support has a groove, and a central shaft is disposed in the groove; the transmission mechanism is mounted on the central shaft; the turntable is rotatably connected to the central shaft.

8. The twisting method for testing the tensile properties of multifilament fibers according to claim 6, characterized in that, The transmission mechanism includes a first gear; a second gear is provided on the turntable; wherein the first gear and the second gear mesh.

9. The twisting method for testing the tensile properties of multifilament fibers according to claim 1, characterized in that, The twisting parameters include the number of twists.

10. The twisting method for testing the tensile properties of multifilament fibers according to claim 9, characterized in that, The twisting parameters also include the twisting speed.

11. The twisting method for testing the tensile properties of multifilament fibers according to claim 1, characterized in that, The controller is located within the twisting parameter setting panel.

12. The twisting method for testing the tensile properties of multifilament fibers according to claim 1, characterized in that, The accuracy of the twist count is less than or equal to 0.1 twists.

13. The twisting method for testing the tensile properties of multifilament fibers according to claim 12, characterized in that, The accuracy of the twist count is 0.1 twists.

14. The twisting method for testing the tensile properties of multifilament fibers according to claim 1, characterized in that, The drive mechanism uses a servo motor.

15. The twisting method for testing the tensile properties of multifilament fibers according to claim 14, characterized in that, By setting the twist number on the twisting parameter setting panel, the controller converts the set twist number into a corresponding number of pulses, controls the number of rotations of the servo motor, and thus twists the fiber multifilament sample to be tested to the set twist number.

16. The twisting method for testing the tensile properties of multifilament fibers according to any one of claims 1-15, characterized in that, The twisting step includes: 1) Fix both ends of the fiber multifilament sample to be tested onto the first clamp and the second clamp of the fiber multifilament tensile property testing twisting device, respectively; 2) Set the twisting parameters on the twisting parameter setting panel of the fiber multifilament tensile property testing twisting device; wherein, the twisting parameters include the number of twists; 3) Start the automatic twisting operation. The controller of the fiber multifilament tensile performance testing twisting device controls the drive mechanism to drive the first clamp or the second clamp to rotate according to the set twisting parameters, so as to twist the fiber multifilament sample to be tested to the required number of twists.

17. The twisting method for testing the tensile properties of multifilament fibers according to claim 16, characterized in that, In step 2), the twisting parameters also include the twisting speed; wherein, when the twisting device for testing the tensile properties of multifilament fibers includes a turntable, the twisting speed is characterized by the rotational speed of the turntable.

18. The twisting method for testing the tensile properties of multifilament fibers according to claim 17, characterized in that, The rotational speed of the turntable is 0.1-1 r / s.

19. A method for testing the tensile properties of multifilament fibers, characterized in that, It includes the following steps: After twisting the fiber multifilament sample to be tested using the twisting method for testing the tensile properties of fiber multifilaments according to any one of claims 1-18, the tensile properties of the fiber multifilament sample to be tested are then tested.

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