Method for measuring boiling water shrinkage of fibers

Abstract

The invention belongs to the technical field of fiber detection, and relates to a method for measuring boiling water shrinkage of fibers, which comprises the following steps of: mounting a clamp I on a metal rod of a slide rheostat, enabling a connecting line between a clamping position of the clamp I and an initial position of a coil of the slide rheostat to be vertical to the metal rod, mounting a clamp II on a slide sheet of the slide rheostat, and enabling the clamp II to be vertical to the metal rod. The slide rheostat is connected to a circuit, and a voltmeter and an ammeter are connected to the circuit and used for testing the voltage and current changes of the slide rheostat; after a fiber to be measured is boiled, two ends of the fiber to be measured are respectively clamped and fixed on the clamp I and the clamp II, the clamp I and the clamp II are kept to coincide, tension is pre-applied to the slip sheet through program control, and the slip sheet generates displacement change, so that the resistance of the sliding resistor is changed. The method provided by the invention is more convenient to operate, and the measured boiling water shrinkage is equivalent and accurate.

Description

Technical Field

[0001] The invention belongs to the technical field of fiber detection and relates to a method for measuring the boiling water shrinkage rate of fibers. Background Art

[0002] Boiling water shrinkage refers to the ratio of the length of a fiber material that shrinks after being boiled in boiling water to its original length. This indicator is an important representation of fiber stability and is of great significance for evaluating the hot water resistance, dimensional stability, and size and unit weight of subsequent processed fabrics of fiber materials. Especially during material processing, it is also necessary to adjust processing parameters such as temperature, pressure, time, etc. according to its boiling water shrinkage to ensure product quality and stability. Therefore, it is also necessary to ensure that the data measured by the boiling water shrinkage test method is more accurate.

[0003] The testing principle of boiling water shrinkage is based on the physical changes of fiber materials in high temperature and high pressure water. The test can intuitively reflect the shrinkage degree of the material in high temperature and high pressure water. It is an important indicator for evaluating the thermal stability of the material. At the same time, it can also understand the deformation ability of the material under high temperature conditions, so as to judge whether it is suitable for use in high temperature environments. With the continuous advancement of materials science and technology, the testing technology of boiling water shrinkage is also constantly developing. At present, a variety of boiling water shrinkage test standards and methods for different fiber materials have been formed.

[0004] GB / T 6505-2017 standard measures boiling water shrinkage by an instrument. The instrument places the sample wire wound by the winding length meter on a wire twisting rack, then puts it into a special boiling water pot to boil, then puts it into a special oven for drying, and finally puts the wire twisting rack into the instrument for measurement. In this process, the special boiling water pot and oven must match the size of the wire twisting rack, that is, the water bath pot, oven, and experimental instrument must match, and none of them can be missing. Without one of them, the experiment cannot be carried out, and the cost of matching experimental tools is relatively high; in addition, the pre-tension during the measurement process of the instrument is a constant value, and different pre-tensions cannot be applied according to the different fineness of the sample wire. Therefore, the number of winding turns of sample wires of different thicknesses is also different, that is, the same test has to be wound multiple times due to different fineness of the sample wire, which is time-consuming and labor-intensive.

[0005] Therefore, it is of great significance to study a method to measure the boiling water shrinkage of fibers in order to solve the above problems. Summary of the invention

[0006] The purpose of the invention is to solve the problems existing in the prior art and provide a method for measuring the boiling water shrinkage of fibers.

[0007] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0008] A method for measuring the boiling water shrinkage of a fiber, comprising: installing a clamp I on a metal rod of a sliding rheostat, the connection line between the clamping position of the clamp I and the starting position of the sliding rheostat coil being perpendicular to the metal rod, installing a clamp II on a sliding piece of the sliding rheostat, connecting the sliding rheostat to a circuit, one end of which is connected to a terminal on the metal rod, and the other end of which is connected to a terminal at the starting position of the coil, and a voltmeter and an ammeter are also connected to the circuit to test the voltage and current changes of the sliding rheostat; after the fiber to be tested is boiled and dried to balance, the two ends are clamped and fixed on the clamp I and the clamp II respectively, and the clamp I and the clamp II are kept overlapped, and the sliding piece is pre-tensioned T through program control, the sliding piece undergoes displacement change, and the clamp II is driven to move, thereby causing the sliding resistor to undergo resistance change; the calculation formula for the boiling water shrinkage of the fiber is as follows:

[0009] Boiling water shrinkage = [1-U×A / (ρ×I×L0)]×100%;

[0010] In the formula, U represents the reading of the voltmeter, A represents the cross-sectional area of ​​the resistance wire used in the sliding rheostat coil, ρ represents the resistivity of the resistance wire used in the sliding rheostat coil, I represents the reading of the ammeter, and L0 represents the original length of the fiber to be tested before boiling;

[0011] When the fiber to be tested is a fully drawn fiber, T = (0.05 ± 0.005) cN × 25 × 2 × fineness × 1.02, 1 cN = 1.02 g;

[0012] When the fiber to be tested is a tensile-deformed fiber, T=(0.2±0.02)cN×25×2×fineness×1.02, 1cN=1.02g.

[0013] From the above formula, we can know that the pre-tension T is related to the thickness of the fiber, that is, it is related to the fineness. At the same time, all fibers of different fineness are wound 25 times, which can be achieved by winding them simultaneously on the same winding length instrument.

[0014] According to the measurement process, the pre-tension T of the present invention is determined according to the thickness of the fiber and the number of turns. When the number of turns is fixed, different pre-tensions can be applied according to the thickness of the fiber. The present invention has concluded through multiple test data that 25 turns are the most suitable.

[0015] When the pre-tension T is accurate, the size of the boiling water shrinkage is related to whether the fiber is affected by the outside world during the measurement process. When the number of turns is too small, the fiber will be deformed by external forces during the winding process. For example, it will be affected by external forces when it is taken off the length measuring instrument after winding, when it is wound into a skein, and when it is hung on the measuring instrument. When the fiber fineness is 8dtex, the size of the boiling water shrinkage is as follows when the number of turns is different:

[0016] Number of laps 5 10 15 20 25 30 40 45 Boiling water shrinkage (%) 9.0 8.8 8.3 8.0 7.8 7.8 7.8 7.8

[0017] Under the condition of accurate pre-tension T, the size of boiling water shrinkage is also affected by the boiling process of boiling water on the fiber. When the number of sample yarn turns is too large, the fiber will be heated unevenly in boiling water and shrink unevenly. After the test process, it was found that the thicker the fiber, the easier it is to affect the uniformity of heating, thereby affecting the boiling water shrinkage of the fiber. When the fiber fineness is 334dtex, the size of the boiling water shrinkage is as follows when the number of turns is different:

[0018] Number of laps 5 10 15 20 25 30 40 45 Boiling water shrinkage (%) 7.3 7.3 7.3 7.3 7.3 6.5 6.0 5.0

[0019] From the above experimental data, it can be seen that when the number of turns of a fiber with a fiber fineness of 8 dtex is less than 25, it is easily affected by external forces, thus affecting the accuracy of the data; when the number of turns of a fiber with a fiber fineness of 334 dtex is greater than 25, it is easily affected by uneven heating, thus affecting the accuracy of the data. Therefore, it is most appropriate to determine the number of turns to be 25.

[0020] In the method of the national standard (i.e. GB / T 6505-2017 standard), all fibers of different fineness are fixed by the total fineness. When the fineness of the sample is ≤400dtex, the number of turns = 2500 / (fineness*2); when the fineness of the sample is >400dtex, the number of turns = 10000 / (fineness*2). For example, if there are 10 fibers of different fineness in a group of samples, they need to be wound 10 times, while the present invention only needs to be wound once. The following table shows the number of turns of sample yarns wound by different methods.

[0021] Fineness 47dtex 63dtex 65dtex 71dtex 73dtex 80dtex 83dtex 167dtex 334dtex The present invention takes the number of turns 25 laps 25 laps 25 laps 25 laps 25 laps 25 laps 25 laps 25 laps 25 laps Number of winding turns in GB / T 6505-2017 27 laps 20 laps 19 laps 18 laps 17 laps 16 laps 15 laps 8 laps 4 laps

[0022] As the preferred technical solution:

[0023] In the method for measuring the boiling water shrinkage of fibers as described above, the range of the voltmeter is 0-15V, and the range of the ammeter is 0-3A.

[0024] As described above, a method for measuring the boiling water shrinkage of a fiber is described, wherein the starting position and the end position of the sliding rheostat coil are A and B respectively, and the horizontal distance between A and B is not less than 55 cm; and the length of the fiber to be measured is 50 cm.

[0025] In the method for measuring the fiber boiling water shrinkage as described above, the boiling temperature is 100° C. and the boiling time is 30 minutes.

[0026] Beneficial effects:

[0027] The testing process and equipment used in the present invention are simpler and less costly, and only the same number of turns (25 turns) are required for fibers of different specifications, so the operation is simpler and more convenient. At the same time, the same accuracy is maintained as that of the boiling water shrinkage rate obtained in the GB / T 6505-2017 standard. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a schematic diagram of various components before measuring the fiber boiling water shrinkage rate of the present invention;

[0029] Figure 2 This is a schematic diagram of various components when measuring the fiber boiling water shrinkage rate of the present invention; Figure 1~Figure 2 a, b, c, d are the four terminals on the sliding rheostat;

[0030] Figure 3 A circuit diagram of a sliding resistor of the present invention;

[0031] Among them, 1-clamp Ⅰ, 2-clamp ⅠⅠ. DETAILED DESCRIPTION

[0032] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0033] The calculation formula of the fiber boiling water shrinkage rate of the present invention is: boiling water shrinkage rate = [1-U×A / (ρ×I×L0)]×100%, wherein U represents the reading of the voltmeter, A represents the cross-sectional area of ​​the resistance wire used in the sliding rheostat coil, ρ represents the resistivity of the resistance wire used in the sliding rheostat coil, I represents the reading of the ammeter, and L0 represents the original length of the fiber to be tested before boiling.

[0034] Example 1

[0035] A method for measuring the boiling water shrinkage of fibers, the specific process is as follows: Figure 1 , Figure 2 As shown, first install the clamp I on the metal rod of the sliding rheostat. The line between the clamping position of the clamp I and the starting position of the sliding rheostat coil is perpendicular to the metal rod. The starting position and the end position of the sliding rheostat coil are A and B respectively, and the horizontal distance between A and B is 55cm. Then install the clamp II on the slider of the sliding rheostat, and connect the sliding rheostat to the circuit (the circuit diagram of the sliding rheostat is as shown in Figure 3As shown in the figure, a voltmeter with a range of 0~15V and an ammeter with a range of 0~3A are also connected to the circuit to test the voltage and current changes of the sliding rheostat; the cross-sectional area of ​​the resistance wire used in the sliding rheostat coil is 0.5mm 2 , the resistivity is 6.5×10 -6 Ω·m.

[0036] In order to verify the accuracy of the boiling water shrinkage measured by the above method, a fiber (fully drawn yarn-polyester fiber, specification 73dtex / 48f) was prepared and divided into 6 fiber samples with a length of 50 cm. The fiber samples were tested using the method of this embodiment and the GB / T 6505-2017 standard, respectively. The test was as follows:

[0037] The fiber to be tested is tested by the method of this embodiment: 3 samples of the fiber to be tested are taken from the above-mentioned fiber samples and then tested respectively. The specific process is: first, the 3 fiber samples to be tested are made into corresponding silk twists (the number of turns is 25), and then the silk twists are put into a gauze bag, boiled at 100°C for 30 minutes, the silk twists are taken out and dried, and balanced for two hours under the atmospheric conditions of the inspection room, and finally the two ends of the silk twist are clamped and fixed on the clamp I and the clamp II respectively, and the clamp I and the clamp II are kept overlapped, and the pre-tension T is applied to the slider through program control, and the slider changes in displacement, so that the resistance of the sliding resistor changes; wherein, the pre-tension T is 186.15N;

[0038] Through the test method of this embodiment, it can be known that the voltage indication numbers of the three samples are 6V, 6V, and 6V respectively, and the current indication numbers of the three samples are 0.987A, 0.990A, and 0.993A respectively. Then, the boiling water shrinkage rates of the three samples are calculated by the calculation formula of the boiling water shrinkage rate to be 6.5%, 6.8%, and 7.0% respectively. Finally, the average value is calculated to obtain the boiling water shrinkage rate of 6.8%;

[0039] The remaining three fiber samples to be tested were tested respectively using the twisted wire method in the GB / T 6505-2017 standard. The specific process is as follows: first, the remaining three fiber samples to be tested were made into corresponding twisted wires (the number of turns was 17), and then the three sample twisted wires were hung on the twisted wire racks respectively. The lengths L0 before cooking were accurately measured by a special instrument, which were 50.0 cm, 50.0 cm, and 50.0 cm respectively. Then, the twisted wire rack was placed in a special water bath, boiled in boiling water at 100°C for 30 minutes, then taken out of the water bath, placed in a special oven for drying for 2 hours, and then balanced under the atmospheric conditions of the physical inspection room for 2 hours. Finally, the balanced twisted wire rack was placed in a special instrument for measurement, and the lengths L1 after cooking were accurately measured to be 46.5 cm, 46.7 cm, and 46.6 cm respectively, and calculated by the boiling water shrinkage calculation formula, which is: boiling water shrinkage % = (L0-L1) / L0.

[0040] Testing using the national standard method shows that the boiling water shrinkage rates of the three samples are 7.0%, 6.6% and 6.8% respectively. Finally, the average value is calculated to obtain a boiling water shrinkage rate of 6.8%.

[0041] It can be seen from the results of the above two test methods that the present invention ensures that the measured boiling water shrinkage is consistent with the boiling water shrinkage measured by the GB / T6505-2017 standard, while its test steps and equipment used are simpler and the cost is lower.

[0042] Example 2

[0043] A method for measuring the boiling water shrinkage of fibers, the specific process is: firstly, a clamp I is installed on the metal rod of a sliding rheostat, the connection line between the clamping position of the clamp I and the starting position of the sliding rheostat coil is perpendicular to the metal rod, the starting position and the end position of the sliding rheostat coil are respectively A and B, and the horizontal distance between A and B is 55cm, then a clamp II is installed on the sliding piece of the sliding rheostat, the sliding rheostat is connected to the circuit, a voltmeter with a range of 0-15V and an ammeter with a range of 0-3A are also connected to the circuit, for testing the voltage and current changes of the sliding rheostat; wherein, the cross-sectional area of ​​the resistance wire used by the sliding rheostat coil is 0.5mm 2 , the resistivity is 6.5×10 -6 Ω·m.

[0044] In order to verify the accuracy of the boiling water shrinkage measured by the above method, a fiber (fully drawn yarn-polyester fiber, specification 47dtex / 32f) was prepared and divided into 6 fiber samples with a length of 50 cm. The fiber samples were tested using the method of this embodiment and the GB / T 6505-2017 standard, respectively. The test was as follows:

[0045] The fiber to be tested is tested by the method of this embodiment: 3 fiber samples to be tested are taken from the above fiber samples to be tested and then tested respectively. The specific process is: first, the 3 fiber samples to be tested are made into corresponding silk twists (the number of turns is 25), and then the silk twists are put into gauze bags, boiled at 100°C for 30 minutes, the silk twists are taken out and dried, and balanced for two hours under the atmospheric conditions of the inspection room, and finally the two ends of the silk twist are clamped and fixed on the clamp I and the clamp II respectively, and the clamp I and the clamp II are kept overlapped, and the pre-tension T is applied to the slider through program control, and the slider changes in displacement, so that the resistance of the sliding resistor changes; wherein, the pre-tension T is 119.85N;

[0046] Through the test method of this embodiment, it can be known that the voltage representation numbers of the three samples are 6V, 6V, and 6V respectively, and the current representation numbers of the three samples are 1.968, 1.970A, and 1.973A respectively. Then, the boiling water shrinkage rates of the three samples are calculated by the calculation formula of the boiling water shrinkage rate to be 53.1%, 53.1%, and 53.2% respectively. Finally, the average value is calculated to obtain the boiling water shrinkage rate of 53.2%;

[0047] Adopt GB / T The remaining three fiber samples to be tested were tested by the twisted wire method in the 6505-2017 standard. The specific process is: first, the remaining three fiber samples to be tested are made into corresponding twisted wires (the number of turns is 27), and then the three sample twisted wires are hung on the twisted wire rack, and the lengths L0 before cooking are accurately measured by a special instrument, which are 50.0cm, 50.0cm, and 50.0cm respectively. Then, the twisted wire rack is placed in a special water bath, and boiled in boiling water at 100°C for 30 minutes. Then, the twisted wire rack is taken out of the water bath, placed in a special oven for drying for 2 hours, and then balanced under the atmospheric conditions of the inspection room for 2 hours. Finally, the balanced twisted wire rack is placed in a special instrument for measurement, and the lengths L1 after cooking are accurately measured to be 23.40cm, 23.45cm, and 23.40cm respectively, and calculated by the boiling water shrinkage calculation formula, which is: boiling water shrinkage % = (L0-L1) / L0.

[0048] Testing using the national standard method shows that the boiling water shrinkage rates of the three samples are 53.2%, 53.1%, and 53.2%, respectively. Finally, the average value is calculated to obtain a boiling water shrinkage rate of 53.2%.

[0049] It can be seen from the results of the above two test methods that the present invention ensures that the measured boiling water shrinkage is consistent with the boiling water shrinkage measured by the GB / T6505-2017 standard, while its test steps and equipment used are simpler and the cost is lower.

[0050] Example 3

[0051] A method for measuring the boiling water shrinkage of fibers, the specific process is: firstly, a clamp I is installed on the metal rod of a sliding rheostat, the connection line between the clamping position of the clamp I and the starting position of the sliding rheostat coil is perpendicular to the metal rod, the starting position and the end position of the sliding rheostat coil are respectively A and B, and the horizontal distance between A and B is 55cm, then a clamp II is installed on the sliding piece of the sliding rheostat, the sliding rheostat is connected to the circuit, a voltmeter with a range of 0-15V and an ammeter with a range of 0-3A are also connected to the circuit, for testing the voltage and current changes of the sliding rheostat; wherein, the cross-sectional area of ​​the resistance wire used by the sliding rheostat coil is 0.5mm 2 , the resistivity is 6.5×10 -6 Ω·m.

[0052] In order to verify the accuracy of the boiling water shrinkage measured by the above method, a fiber (fully drawn yarn-polyester fiber, specification 71dtex / 48f) was first prepared and divided into 6 fiber samples to be tested with a length of 50 cm, and the fiber samples to be tested were tested using the method of this embodiment and the GB / T 6505-2017 standard, respectively, as follows:

[0053] The fiber to be tested is tested by the method of this embodiment: 3 samples of the fiber to be tested are taken from the above-mentioned samples and then tested respectively. The specific process is: first, the 3 fiber samples to be tested are made into corresponding silk twists (the number of turns is 25), and then the silk twists are put into a gauze bag, boiled at 100°C for 30 minutes, the silk twists are taken out and dried, and balanced for two hours under the atmospheric conditions of the inspection room, and finally the two ends of the silk twist are clamped and fixed on the clamp I and the clamp II respectively, and the clamp I and the clamp II are kept overlapped, and the pre-tension T is applied to the slider through program control, and the slider changes in displacement, so that the resistance of the sliding resistor changes; wherein, the pre-tension T is 181.05N;

[0054] Through the test method of this embodiment, it can be known that the voltage indication numbers of the three samples are 6V, 6V, and 6V respectively, and the current indication numbers of the three samples are 1.275A, 1.280A, and 1.290A respectively. Then, the boiling water shrinkage rates of the three samples are calculated by the calculation formula of the boiling water shrinkage rate to be 27.6%, 27.9%, and 28.4% respectively. Finally, the average value is calculated to obtain the boiling water shrinkage rate of 28.0%;

[0055] Adopt GB / T The remaining three fiber samples to be tested were tested by the twisted wire method in the 6505-2017 standard. The specific process is as follows: first, the remaining three fiber samples to be tested are made into corresponding twisted wires (the number of turns is 18), and then the three sample twisted wires are hung on the twisted wire rack, and the lengths L0 before cooking are accurately measured by a special instrument, which are 50.0cm, 50.0cm, and 50.0cm respectively. Then, the twisted wire rack is placed in a special water bath, and boiled in 100°C boiling water for 30 minutes. Then, the twisted wire rack is taken out of the water bath, placed in a special oven for drying for 2 hours, and then balanced under the atmospheric conditions of the inspection room for 2 hours. Finally, the balanced twisted wire rack is placed in a special instrument for measurement, and the lengths L1 after cooking are accurately measured to be 35.95cm, 36.10cm, and 36.00cm respectively, and are calculated by the boiling water shrinkage calculation formula. The boiling water shrinkage calculation formula is: boiling water shrinkage % = (L0-L1) / L0.

[0056] Testing using the national standard method shows that the boiling water shrinkage rates of the three samples are 28.1%, 27.8% and 28.0% respectively. Finally, the average value is calculated to obtain a boiling water shrinkage rate of 28.0%.

[0057] It can be seen from the results of the above two test methods that the present invention ensures that the measured boiling water shrinkage is consistent with the boiling water shrinkage measured by the GB / T6505-2017 standard, while its test steps and equipment used are simpler and the cost is lower.

[0058] Example 4

[0059] A method for measuring the boiling water shrinkage of fibers, the specific process is: firstly, a clamp I is installed on the metal rod of a sliding rheostat, the connection line between the clamping position of the clamp I and the starting position of the sliding rheostat coil is perpendicular to the metal rod, the starting position and the end position of the sliding rheostat coil are respectively A and B, and the horizontal distance between A and B is 55cm, then a clamp II is installed on the sliding piece of the sliding rheostat, the sliding rheostat is connected to the circuit, a voltmeter with a range of 0-15V and an ammeter with a range of 0-3A are also connected to the circuit, for testing the voltage and current changes of the sliding rheostat; wherein, the cross-sectional area of ​​the resistance wire used by the sliding rheostat coil is 0.5mm 2 , the resistivity is 6.5×10 -6 Ω·m.

[0060] In order to verify the accuracy of the boiling water shrinkage measured by the above method, a fiber (stretched textured yarn-polyester fiber, specification 83dtex / 36f) was first prepared and divided into 6 fiber samples with a length of 50 cm. The fiber samples were tested using the method of this embodiment and the GB / T 6505-2017 standard, respectively. The test was as follows:

[0061] The fiber to be tested is tested by the method of this embodiment: 3 samples of the fiber to be tested are taken from the above-mentioned samples and then tested respectively. The specific process is: first, the 3 samples of the fiber to be tested are made into corresponding silk twists (the number of turns is 25), and then the silk twists are put into a gauze bag, boiled at 100°C for 30 minutes, the silk twists are taken out and dried, and balanced for two hours under the atmospheric conditions of the inspection room, and finally the two ends of the silk twist are clamped and fixed on the clamp I and the clamp II respectively, and the clamp I and the clamp II are kept overlapped, and the pre-tension T is applied to the slider through program control, and the slider changes in displacement, so that the resistance of the sliding resistor changes; wherein, the pre-tension T is 846.6N;

[0062] Through the test method of this embodiment, it can be known that the voltage indication numbers of the three samples are 6V, 6V, and 6V respectively, and the current indication numbers of the three samples are 0.952A, 0.950A, and 0.954A respectively. Then, the boiling water shrinkage rates of the three samples are calculated by the calculation formula of the boiling water shrinkage rate to be 3.0%, 2.8%, and 3.2% respectively. Finally, the average value is calculated to obtain the boiling water shrinkage rate of 3.0%;

[0063] Adopt GB / T The remaining three fiber samples to be tested were tested by the twisted wire method in the 6505-2017 standard. The specific process is: first, the remaining three fiber samples to be tested are made into corresponding twisted wires (the number of turns is 15), and then the three sample twisted wires are hung on the twisted wire rack, and the lengths L0 before cooking are accurately measured by a special instrument, which are 50.0cm, 50.0cm, and 50.0cm respectively. Then, the twisted wire rack is placed in a special water bath, boiled in 100℃ boiling water for 30 minutes, and then the twisted wire rack is taken out of the water bath, placed in a special oven for drying for 2 hours, and then balanced under the atmospheric conditions of the inspection room for 2 hours. Finally, the balanced twisted wire rack is placed in a special instrument for measurement, and the lengths L1 after cooking are accurately measured to be 48.40cm, 48.50cm, and 48.60cm respectively, and calculated by the boiling water shrinkage calculation formula, and the boiling water shrinkage calculation formula is: boiling water shrinkage %=(L0-L1) / L0.

[0064] Through the national standard method test, it was found that the boiling water shrinkage rates of the three samples were 3.2%, 3.0% and 2.8% respectively. Finally, the average value was calculated to obtain a boiling water shrinkage rate of 3.0%.

[0065] It can be seen from the results of the above two test methods that the present invention ensures that the measured boiling water shrinkage is consistent with the boiling water shrinkage measured by the GB / T6505-2017 standard, while its test steps and equipment used are simpler and the cost is lower.

[0066] Example 5

[0067] A method for measuring the boiling water shrinkage of fibers, the specific process is: firstly, a clamp I is installed on the metal rod of a sliding rheostat, the connection line between the clamping position of the clamp I and the starting position of the sliding rheostat coil is perpendicular to the metal rod, the starting position and the end position of the sliding rheostat coil are respectively A and B, and the horizontal distance between A and B is 55cm, then a clamp II is installed on the sliding piece of the sliding rheostat, the sliding rheostat is connected to the circuit, a voltmeter with a range of 0-15V and an ammeter with a range of 0-3A are also connected to the circuit, for testing the voltage and current changes of the sliding rheostat; wherein, the cross-sectional area of ​​the resistance wire used by the sliding rheostat coil is 0.5mm 2 , the resistivity is 6.5×10 -6 Ω·m.

[0068] In order to verify the accuracy of the boiling water shrinkage measured by the above method, a fiber (stretched textured yarn-polyester fiber, specification 167dtex / 288f) was first prepared and divided into 6 fiber samples to be tested with a length of 50 cm, and the fiber samples to be tested were tested using the method of this embodiment and the GB / T 6505-2017 standard, respectively, as follows:

[0069] The fiber to be tested is tested by the method of this embodiment: 3 samples of the fiber to be tested are taken from the above-mentioned fiber samples and then tested respectively. The specific process is: first, the 3 fiber samples to be tested are made into corresponding silk twists (the number of turns is 25), and then the silk twists are put into a gauze bag, boiled at 100°C for 30 minutes, the silk twists are taken out and dried, and balanced for two hours under the atmospheric conditions of the inspection room, and finally the two ends of the silk twist are clamped and fixed on the clamp I and the clamp II respectively, and the clamp I and the clamp II are kept overlapped, and the pre-tension T is applied to the slider through program control, and the slider changes in displacement, so that the resistance of the sliding resistor changes; wherein, the pre-tension T is 1703.4N;

[0070] Through the test method of this embodiment, it can be known that the voltage representation numbers of the three samples are 6V, 6V, and 6V respectively, and the current representation numbers of the three samples are 0.956A, 0.955A, and 0.957A respectively. Then, the boiling water shrinkage rates of the three samples are calculated by the calculation formula of the boiling water shrinkage rate to be 3.4%, 3.3%, and 3.5% respectively. Finally, the average value is calculated to obtain the boiling water shrinkage rate of 3.4%;

[0071] The remaining three fiber samples to be tested were tested respectively using the twisted wire method in the GB / T 6505-2017 standard. The specific process was as follows: first, the remaining three fiber samples to be tested were made into corresponding twisted wires (the number of turns was 8), and then the three sample twisted wires were hung on the twisted wire racks respectively, and the lengths L0 before cooking were accurately measured by a special instrument, which were 50.0 cm, 50.0 cm, and 50.0 cm respectively. Then, the twisted wire rack was placed in a special water bath, and boiled in boiling water at 100°C for 30 minutes. The twisted wire rack was taken out of the water bath, placed in a special oven for drying for 2 hours, and then balanced under the atmospheric conditions of the inspection room for 2 hours. Finally, the balanced twisted wire rack was placed in a special instrument for measurement, and the lengths L1 after cooking were accurately measured to be 48.35 cm, 48.30 cm, and 48.25 cm respectively, and calculated by the boiling water shrinkage calculation formula, and the boiling water shrinkage calculation formula was: boiling water shrinkage % = (L0-L1) / L0.

[0072] Through the national standard method test, it was found that the boiling water shrinkage rates of the three samples were 3.3%, 3.4% and 3.5% respectively. Finally, the average value was calculated to obtain a boiling water shrinkage rate of 3.4%.

[0073] It can be seen from the results of the above two test methods that the present invention ensures that the measured boiling water shrinkage is consistent with the boiling water shrinkage measured by the GB / T6505-2017 standard, while its test steps and equipment used are simpler and the cost is lower.

Claims

1. A method for measuring fiber boiling water shrinkage, characterized in that: A clamp I is installed on the metal rod of the sliding rheostat, and the connection line between the clamping position of the clamp I and the starting position of the sliding rheostat coil is perpendicular to the metal rod. A clamp II is installed on the sliding piece of the sliding rheostat, and the sliding rheostat is connected to the circuit. A voltmeter and an ammeter are also connected to the circuit to test the voltage and current changes of the sliding rheostat. After the fiber to be tested is boiled, the two ends are clamped and fixed on the clamp I and the clamp II respectively, and the clamp I and the clamp II are kept overlapped. The sliding piece is pre-tensioned by program control, and the sliding piece undergoes displacement change, thereby causing the resistance of the sliding resistor to change. The calculation formula of the fiber boiling water shrinkage rate is as follows: Boiling water shrinkage = [1-U×A / (ρ×I×L0)]×100%; In the formula, U represents the reading of the voltmeter, A represents the cross-sectional area of ​​the resistance wire used in the sliding rheostat coil, ρ represents the resistivity of the resistance wire used in the sliding rheostat coil, I represents the reading of the ammeter, and L0 represents the original length of the fiber to be tested before boiling; When the fiber to be tested is a fully drawn fiber, T=(0.05±0.005)cN×25×2×fineness×1.02; When the fiber to be tested is a tensile-deformed fiber, T=(0.2±0.02)cN×25×2×fineness×1.

02.

2. The method for measuring fiber boiling water shrinkage according to claim 1, characterized in that: The range of the voltmeter is 0~15V, and the range of the ammeter is 0~3A.

3. The method for measuring fiber boiling water shrinkage according to claim 1, characterized in that: The starting and ending positions of the sliding rheostat coil are A and B respectively, and the horizontal distance between A and B is not less than 55 cm; the length of the fiber to be tested is 50 cm.

4. The method for measuring the boiling water shrinkage of a fiber according to claim 1, characterized in that: The boiling temperature is 100°C and the boiling time is 30 minutes.

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