A positive and negative double-wrapped spiral strain sensing composite yarn and its preparation method and application

Abstract

The present invention relates to a forward and reverse double-wrapped spiral strain sensing composite yarn and its preparation method and application. The twist of the product is 300~800T / 10cm. During the preparation, a yarn coated with carbon nanotubes is first prepared, and then a PU coating is formed on the surface of the yarn coated with carbon nanotubes to obtain a conductive yarn. Then, the conductive yarn is fed into the space between two friction rollers rotating in the same direction on a friction spinning machine through an adaptive yarn tension device, and the flexible fiber roving is fed into the roller drafting mechanism of the friction spinning machine to prepare a flexible core-wrapped conductive yarn by friction spinning. The flexible core-wrapped conductive yarn is sequentially wound through forward and reverse spirals, and after each winding, it is passed through a same-direction twister to form a secondary twist to obtain a composite yarn product. The composite yarn product can be used in smart wearables. The preparation process of the present invention is simple and efficient; the product has excellent strain-capacitive sensing performance and more stable signal output, excellent adaptability, structural stability and durability, and broad application prospects.

Description

Technical Field

[0001] The invention belongs to the technical field of intelligent textiles and relates to a forward and reverse double-wrapped spiral strain sensing composite yarn and a preparation method and application thereof. Background Art

[0002] Flexible wearable strain sensors used to monitor physiological signals such as human movement, heartbeat, body temperature and pulse can provide timely feedback on human health data, so they have attracted much attention. At present, many researchers have prepared flexible strain sensors with special structural designs, but this complex structural design makes manufacturing difficult, and ultimately makes commercial applications difficult. Therefore, it is an urgent problem to design a strain sensor with stable structure and excellent performance, so that it can be easily manufactured, easy to commercialize, and can fit the human body to accurately measure human physiological signals.

[0003] Textiles are ideal materials for manufacturing wearable flexible sensors due to their softness, elasticity and comfort. As the basis of textiles, yarns show great potential in the preparation of flexible sensors. However, yarn-based flexible sensors prepared by methods such as polymer encapsulation and solution extrusion are difficult to have excellent flexibility and breathability, which affects the comfort of wearing. Yarn-based flexible sensors are mainly divided into two types: piezoresistive and capacitive. Capacitive yarn-based flexible sensors have the advantages of fast response speed and high resolution, making them a good choice for the preparation of flexible sensors. However, most of the current capacitive yarn-based flexible sensors are simply prepared by twisting two conductive yarns. The strand structure of this strand-type capacitive flexible strain sensor is bound to be destroyed after repeated stretching.

[0004] For example, the literature (High-Performance Textile-Based Capacitive Strain Sensors via Enhanced Vapor Phase Polymerization of Pyrrole and Their Application to Machine Learning-Assisted Hand Gesture Recognition) prepared conductive elastic yarn by in-situ polymerization of PPy outside the elastic yarn, and then immersed the conductive yarn in a toluene solution of barium titanate to obtain an insulated conductive elastic yarn; the conductive elastic yarn and the insulated conductive elastic yarn were twisted into strands and fixed together with double-sided tape. However, the production efficiency and cost of preparing conductive elastic yarn by in-situ polymerization are low; at the same time, the method of fixing the strands with double-sided tape cannot solve the problem of the stability of the strand structure during its stretching process, especially after repeated stretching, the double-sided tape will be damaged, resulting in a loose strand structure.

[0005] Chinese patent CN 116147671 A adopts water bath electrospinning method to coat polyamide 6 (PA6) nanofibers on conductive core yarn to prepare nanofiber core-spun yarn; the prepared nanofiber core-spun yarn is divided into two parts, one of which is dyed with a neutral dye; the dyed fiber core-spun yarn and the white fiber core-spun yarn are wound side by side on the rubber band to prepare a double helix structure flexible capacitive sensor; however, this method of wrapping the rubber band in parallel will inevitably cause the rubber to relax after repeated stretching, resulting in loose wrapping and reduced stability.

[0006] Therefore, it is of great significance to study a forward and reverse double-wrapped spiral strain sensing composite yarn and its preparation method and application to solve the problems existing in the prior art. Summary of the invention

[0007] The purpose of the present invention is to solve the problems existing in the prior art and to provide a forward and reverse double-wrapped spiral strain sensing composite yarn and a preparation method and application thereof.

[0008] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0009] A method for preparing a forward and reverse double-wrapped spiral strain sensing composite yarn comprises the following steps:

[0010] (1) After the yarn is unwound from the yarn bobbin, it is passed through an oiler soaked with a carbon nanotube (CNT) dispersion to obtain a yarn coated with carbon nanotubes, and then wound on a winding machine. The winding machine is started to wind the coated carbon nanotube yarn into a bobbin, and then dried in an oven. The coating and drying processes are repeated until the unit length resistance of the coated carbon nanotube yarn no longer changes; then, a PU coating is formed on the surface of the coated carbon nanotube yarn in the same manner to obtain a conductive yarn; the present invention uses an oiler to repeatedly coat the yarn surface, which not only improves the yarn coating efficiency and is conducive to large-scale production, but also makes the coating material more uniform; at the same time, the present invention performs a PU coating after coating the CNT to ensure that the CNT coating will not fall off due to friction, bending, sweat stains and other factors during subsequent use, thereby ensuring the conductive stability;

[0011] (2) The conductive yarn obtained in step (1) is fed into the space between two friction rollers rotating in the same direction on a friction spinning machine through an adaptive yarn tension device, and the flexible fiber roving is fed into the roller drafting mechanism of the friction spinning machine to prepare a flexible core-spun conductive yarn by friction spinning; the adaptive yarn tension device is composed of a fixed part, a tension control part and a drafting roller; the fixed part plays the role of fixing the device and maintaining the stability of the device to ensure the stability of the equipment operation, the fixed part includes a transverse fixing bracket and four longitudinal fixing brackets, the transverse fixing bracket is fixed in front of the friction roller of the friction spinning machine by screws, and the four longitudinal fixing brackets are respectively recorded as the first longitudinal fixing bracket, the second longitudinal fixing bracket, the third longitudinal fixing bracket and the fourth longitudinal fixing bracket from left to right; the tension control part mainly has the function of monitoring the yarn tension and regulating the yarn tension, and the tension control part includes a yarn tension sensor and an automatic tensioning motor, The yarn tension sensor and the automatic tensioning motor are respectively fixed on the first longitudinal fixed bracket and the second longitudinal fixed bracket, with the yarn tension sensor in front and the automatic tensioning motor in the back, and the yarn tension sensor is a commercially available tension sensor; the automatic tensioning motor assembly is composed of a servo motor and a spring tension wheel; the servo motor is connected to the spring tension wheel, and both are fixed on the second longitudinal fixed bracket; the signal of the tension sensor is transmitted to the servo motor, driving the rotating arm to retract and rotate the spring tension wheel, and quickly turn to the process position set by the computer, so as to perform adaptive tension adjustment on the yarn tension, thereby avoiding uneven tension; the drafting roller is composed of two pairs of front and rear pressure rollers, each pair of pressure rollers is composed of two upper and lower rollers, and the two pairs of pressure rollers are respectively fixed on the third longitudinal fixed bracket and the fourth longitudinal fixed bracket by two support rods, and the yarn passes through the middle of the upper and lower pressure rollers in the drafting roller in turn, so that the yarn keeps a stable route and is evenly drafted during the forward process;

[0012] During the friction spinning process, the core yarn is subjected to a reverse rotational force during the fiber flow coating process, which will affect the tension of the core yarn and thus affect its drafting speed. When the core yarn drafting speed is uneven, it will affect the outer fiber flow coating thickness and make the yarn uneven. At the same time, the uneven yarn tension will cause the tension on the inner core yarn to disappear after the friction spinning machine, resulting in uneven shrinkage of the core yarn and accumulation of outer fibers. The core yarn of the present invention first passes through an adaptive yarn tension device, which ensures the stability of the yarn tension and the drafting speed at the same time. Finally, the core-wrapped conductive yarn obtained has uniform fiber distribution and excellent yarn dryness.

[0013] (3) The two flexible core-wrapped conductive yarns obtained in step (2) are wound on the first tube and the second tube of the ring twisting machine at one time through a winding machine to obtain a first core-wrapped conductive yarn and a second core-wrapped conductive yarn respectively; the elastic spandex yarn is drawn by the front leather roller of the core yarn roller and the overfeed wheel and then output, and the first core-wrapped conductive yarn sent out by the clockwise rotating first tube is fed to the front roller jaws through a yarn guide, merges with the output elastic spandex yarn on the central axis and is wrapped around the elastic spandex yarn to form a positive single helical structure wrapped yarn, and then the second core-wrapped conductive yarn is reversely helically wound by the counterclockwise rotating second tube, and after each wrapping, it is passed through a same-direction twister to form a secondary twist, and finally a positive and negative double-wrapped helical strain sensing composite yarn is obtained; during the double wrapping process, the positive and negative wrapping process will generate tension on the middle core yarn to cause the yarn to deform, and the double-wrapped yarn will inevitably shrink after leaving the machine. To solve this problem, the present invention adds an overfeeding wheel in the process before double wrapping. The overfeeding wheel can be used to overfeed the yarn during the spinning process. When the machine is started, the elastic spandex yarn is overfed into the front roller jaws. When the core yarn is subjected to tension during the wrapping process, the spandex will not be deformed due to the overfeeding of the elastic spandex yarn under tension. Therefore, the yarn will not shrink after leaving the machine, avoiding affecting subsequent use. There are various overfeeding wheel mechanisms. The overfeeding wheel of the present invention is combined by the inventor according to the use requirements. The overfeeding wheel is composed of an active roller, a passive roller and a holding roller. The above mechanism is connected and driven by a connecting shaft; after the active roller is started, the passive roller is driven, and finally the passive roller rotates the holding roller. After the yarn passes through the holding wheel, an overfeeding effect is generated and enters the next mechanism. The overfeeding mechanism of the present invention has the advantages of simple structure, convenient installation, easy adjustment, stable output, etc. The speed of the active roller of the present invention is 65~80r / min.

[0014] As the preferred technical solution:

[0015] In the method for preparing a forward and reverse double-wrapped helical strain sensing composite yarn as described above, the mass fraction of the carbon nanotube dispersion in step (1) is 2-5wt%, and the content of carbon nanotubes in the conductive yarn is 1-10mg / tex.

[0016] In the method for preparing a forward and reverse double-wrapped spiral strain sensing composite yarn as described above, the yarn in step (1) is cotton yarn, tencel yarn or nylon yarn, and the fineness of the yarn is 30tex.

[0017] In the method for preparing the forward and reverse double-wrapped spiral strain sensing composite yarn as described above, the drying temperature in step (1) is 60-80° C. and the drying time is 0.5-1 h.

[0018] In the method for preparing a forward and reverse double-wrapped spiral strain sensing composite yarn as described above, the flexible fiber in step (2) is cotton fiber, wool fiber or Tencel fiber, preferably Tencel fiber, and the fineness of the flexible core-wrapped conductive yarn is 30-120 tex.

[0019] According to the method for preparing a forward and reverse double-wrapped spiral strain sensing composite yarn as described above, the specific preparation process of the flexible core-wrapped conductive yarn in step (2) is as follows: winding the conductive yarn onto a bobbin and placing it on a bobbin support frame of a friction spinning machine, unwinding the conductive yarn from the bobbin and feeding it axially through an adaptive yarn tension device into two friction rollers rotating in the same direction on the friction spinning machine, and at the same time feeding the flexible fiber roving into the roller drafting mechanism of the friction spinning machine; the flexible fiber roving is combed into a flexible fiber flow by the combing roller of the friction spinning machine, and the flexible fiber roving is combed into a flexible fiber flow by the combing roller of the friction spinning machine. The flexible fiber flow enters the wedge-shaped area between two friction rollers rotating in the same direction (the area between the two friction rollers is called the wedge-shaped area, which is common knowledge in the art), and condenses on the surface of the friction roller in the wedge-shaped area to form condensed whiskers. The two friction rollers rotating in the same direction apply upward and downward friction forces to the condensed whiskers respectively, forming a rotational force opposite to the twisting direction of the composite yarn core, reversely twisting the condensed whiskers and wrapping them around the surface of the conductive yarn, forming a flexible core-wrapped conductive yarn with a conductive yarn as the core and a flexible fiber reversely twisted and wrapped as the shell.

[0020] In the method for preparing a forward and reverse double-wrapped spiral strain sensing composite yarn as described above, the process parameters of friction spinning in step (2) are: combing roller speed 3000~5000r / min, friction roller speed 4000~5000r / min, flexible fiber roving feeding speed 0.1~1.0m / min, conductive yarn winding speed 5~8m / min (the core yarn in the friction spinning machine relies on the winding speed to control its feeding speed).

[0021] In the method for preparing a forward and reverse double-wrapped spiral strain sensing composite yarn as described above, the fineness of the elastic spandex yarn in step (3) is 100D, 150D or 200D.

[0022] The present invention also provides a forward and reverse double-wrapped spiral strain sensing composite yarn prepared by the method described in any one of the above items, wherein the twist of the forward and reverse double-wrapped spiral strain sensing composite yarn is 300-800T / 10cm;

[0023] The reverse double-wrapped spiral strain sensing composite yarn has a wide strain sensing range (strain sensing range is 0~130%), short response time (sensing stretch response time is 30~51ms and recovery time is 26~46ms at a strain of 110%), and high stability (the electrical signal remains unchanged after 12,000 stretches at 110% strain, indicating that its sensing performance remains stable); in addition, the forward and reverse double-wrapped spiral strain sensing composite yarn can accurately monitor various human gestures.

[0024] The present invention also provides an application of the forward and reverse double-wrapped spiral strain sensing composite yarn as described above in smart wearables.

[0025] Beneficial effects:

[0026] (1) The present invention discloses a method for preparing a positive and negative double-wrapped spiral strain sensing composite yarn, which realizes a layered structure of a flexible core-wrapped conductive yarn by using a friction spinning layered twisting process. Since the warp twist distribution of the yarn gradually decreases from the yarn core to the outer layer, the structure is tight inside and loose outside. The inner layer yarn core has a high twist, which significantly improves the bonding strength between the fiber and the active conductive material, ensuring that the conductive path is complete and stable. At the same time, the tight structure prevents the active material from falling off under severe deformation. Moreover, the loose outer layer of the flexible core-wrapped conductive yarn prepared by friction spinning is conducive to improving the change of electrical signals during the stretching and recovery process. The outer layer has less twist, the yarn is plump and fluffy, the surface coverage is strong and uniform and clean, and the soft and skin-friendly outer layer structure also improves the hand feel and wearing fit performance, and has broad application prospects in the field of smart wearables.

[0027] (2) The present invention provides a method for preparing a forward and reverse double-wrapped spiral strain sensing composite yarn. Through the bidirectional wrapping and twisting technology, the two flexible core-wrapped conductive yarns wrapped on the surface of the elastic spandex yarn present a forward and reverse twisted spiral structure, which exhibits more excellent stretch recovery performance while improving the stability of the spiral structure. It solves the problem that the structure of the strand-type capacitive sensor is not easily damaged and loosened after long-term stretching, ensures excellent strain-capacitive sensing performance and more stable signal output during cyclic stretching deformation, and has excellent adaptability, structural stability and durability.

[0028] (3) A method for preparing a positive and negative double-wrapped spiral strain sensing composite yarn of the present invention, wherein the core yarn first passes through an adaptive yarn tension device, which ensures that the yarn tension is stable while stabilizing the drafting speed, and the resulting core-wrapped conductive yarn has uniform fiber distribution and excellent yarn evenness;

[0029] (4) A method for preparing a forward and reverse double-wrapped spiral strain sensing composite yarn of the present invention has a simple and efficient preparation process and can achieve low-cost, large-scale industrial production;

[0030] (5) The forward and reverse double-wrapped spiral strain sensing composite yarn of the present invention has excellent properties such as light weight, super elasticity, high tensile stability, softness, skin-friendliness and comfort;

[0031] (6) The application of a positive and negative double-wrapped spiral strain sensing composite yarn in the present invention in smart wearables has been successfully applied to motion monitoring in various scenarios such as monitoring small movements and large strains, as well as integrated gesture recognition gloves. It has a wide range of applications and is suitable for a variety of scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a schematic diagram of the adaptive yarn tension device of the present invention;

[0033] Figure 2The present invention is a flow chart of preparing a forward and reverse double-wrapped spiral strain sensing composite yarn when the yarn is a Tencel yarn;

[0034] Figure 3 Schematic diagram of core-spun conductive yarns with different coating thicknesses in Examples 1 to 4 of the present invention; wherein 80 tex is Example 1, 46 tex is Example 2, 64 tex is Example 3, and 99 tex is Example 4;

[0035] Figure 4 Schematic diagram of the forward and reverse double-wrapped spiral strain sensing composite yarn wrapped with core-wrapped conductive yarns of different thicknesses in Examples 1 to 4 of the present invention; wherein 80 tex is Example 1, 46 tex is Example 2, 64 tex is Example 3, and 99 tex is Example 4;

[0036] Figure 5 The capacitance relative change diagram of the forward and reverse double-wrapped spiral Tencel strain sensing composite yarn of the core-wrapped conductive yarn with different coating thicknesses in Examples 1 to 4 of the present invention;

[0037] Figure 6 Schematic diagram of the forward and reverse double-wrapped helical Tencel strain sensing composite yarn with different twists in Examples 1 and 5 to 7 of the present invention; wherein 600T is Example 1, 400T is Example 5, 500T is Example 6, and 700T is Example 7;

[0038] Figure 7 The graph is a graph of the relative change in capacitance of the forward and reverse double-wrapped spiral strain sensing composite yarns prepared in Examples 1 and 5 to 7 of the present invention under tensile strain; wherein 600T is Example 1, 400T is Example 5, 500T is Example 6, and 700T is Example 7;

[0039] Figure 8 This is a graph showing the relative change in capacitance of the forward and reverse double-wrapped spiral strain sensing composite yarn of Example 1 of the present invention under different tensile strains;

[0040] Fig. 9 This is a graph showing the relative change in capacitance of the forward and reverse double-wrapped spiral strain sensing composite yarn at different stretching speeds according to Example 1 of the present invention;

[0041] Fig.10 Schematic diagrams of the ply-type strain sensing yarn (left) and the forward and reverse double-wrapped spiral strain sensing composite yarn of Example 1 (right) before and after stretching;

[0042] Fig.11 Cyclic stability diagrams of the ply-type strain sensing yarn (left) and the forward and reverse double-wrapped spiral strain sensing composite yarn of Example 1 (right);

[0043] Fig.12This is a response time diagram of the forward and reverse double-wrapped spiral strain sensing composite yarn of Example 1 of the present invention; wherein the left and right figures are both enlarged views of the dotted frame shown in the middle;

[0044] Fig.13 This is the real-time normalized data of the smart glove in which the forward and reverse double-wrapped spiral strain sensing composite yarn is integrated into the sensor network for digital gesture recognition according to Example 1 of the present invention; the five curves in the figure represent the five output channel curves of different fingers, which correspond to the thumb, index finger, middle finger, ring finger and little finger from bottom to top respectively;

[0045] Among them, 1-yarn, 2-yarn tension sensor, 3-fixed part, 4-servo motor, 5-spring tension wheel, 6-front pressure roller, 7-rear pressure roller. DETAILED DESCRIPTION

[0046] 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.

[0047] The test methods involved in the performance indicators of the embodiments of the present invention and the comparative examples are as follows:

[0048] Twist: Test in accordance with GB / T 2543.1-2015; specifically: remove the ply twist of the strands, cut off the excess single yarns, leaving only one of them, adjust the gauge as required, fix the sample on the clamp with the specified pre-tension, rotate the movable clamp to untwist until the analysis needle moves from the fixed clamp to the rotating clamp, record the initial length, twist direction and number of twists, repeat the above operation until the required number of tests is completed. However, if the single yarns are different, they should be tested separately. When the single yarn is a short-fiber yarn, its twist should be measured as a short-fiber single yarn; when the single yarn is a multifilament, its twist should be measured as a multifilament.

[0049] Strain-capacitive sensing: Connect both ends of the sensing yarn to the LCR bridge device (TH2830, Changzhou Tonghui Electronics Co., Ltd.), then place the sensing yarn on the flexible electronic multimodal testing system (ST600C, Suzhou Shengte Intelligent Technology Co., Ltd.) to clamp both ends of the yarn, set the stretching speed of the flexible electronic multimodal testing system (specifically, Example 1: 50 mm / min, 100 mm / min, 150 mm / min, 200 mm / min; Comparative Examples 1-3: 200 mm / min; Examples 2-7: 200 mm / min) and the stretching percentage (specifically, Example 1: 70%, 90%, 110%, 130%; Comparative Examples 1-3: 110%; Examples 2-7: 110%), start the LCR bridge device to record the changes in the electrical signals of the sensing yarn during the stretching process.

[0050] Example 1

[0051] A method for preparing a positive and negative double-wrapped spiral strain sensing composite yarn, such as Figure 2 As shown, the specific steps are as follows:

[0052] (1) After unwinding a 30 tex Tencel yarn from a yarn bobbin, the yarn was passed through an oiler soaked in a carbon nanotube dispersion to obtain a carbon nanotube-coated yarn, which was then wound on a winding machine. The winding machine was started to wind the yarn into a bobbin, which was then dried at 70°C for 0.5 h. The coating and drying processes were repeated until the resistance per unit length of the carbon nanotube-coated yarn no longer changed.

[0053] Among them, the mass fraction of the carbon nanotube dispersion is 4wt%;

[0054] (2) Passing the coated carbon nanotube yarn through an oiler soaked in PU solution and winding it on a winding machine, starting the winding machine to wind the yarn into a tube, and then drying it at 70°C for 0.5h, repeating the coating and drying process to form a PU coating on the surface of the coated carbon nanotube yarn to obtain a conductive yarn;

[0055] Among them, the mass fraction of PU solution is 5wt%, and the content of carbon nanotubes in the conductive yarn is 8mg / tex;

[0056] (3) Winding the conductive yarn obtained in step (2) onto a bobbin and placing it on a bobbin support frame of a friction spinning machine, unwinding the conductive yarn from the bobbin and feeding it axially through an adaptive yarn tension device into the space between two friction rollers rotating in the same direction on the friction spinning machine, and at the same time feeding a Tencel fiber roving with a fineness of 780 tex into a roller drafting mechanism of the friction spinning machine; the Tencel fiber roving is combed into a Tencel fiber flow by the combing roller of the friction spinning machine, and the Tencel fiber flow enters the wedge-shaped area between the two friction rollers rotating in the same direction and condenses on the surface of the friction roller in the wedge-shaped area to form a condensed strand, and the two friction rollers rotating in the same direction apply upward and downward friction forces to the condensed strand respectively, reversely twisting the condensed strand and wrapping it around the surface of the conductive yarn, thereby forming a flexible core-wrapped conductive yarn with the conductive yarn as the core and the reversely twisted Tencel fiber as the shell, such as Figure 3 As shown, the fineness of the flexible core-spun conductive yarn is 80 tex and the CV value is 16.74%;

[0057] Among them, the adaptive yarn tension device consists of a fixed part, a tension control part and a drafting roller; the fixed part includes a transverse fixed bracket and four longitudinal fixed brackets, the transverse fixed bracket is fixed in front of the friction roller of the friction spinning machine by screws, and the four longitudinal fixed brackets are recorded as the first longitudinal fixed bracket, the second longitudinal fixed bracket, the third longitudinal fixed bracket and the fourth longitudinal fixed bracket from left to right; the tension control part includes a yarn tension sensor and an automatic tensioning motor, the yarn tension sensor and the automatic tensioning motor are respectively fixed on the first longitudinal fixed bracket and the second longitudinal fixed bracket, the yarn tension sensor is in front and the automatic tensioning motor is in the back; the automatic tensioning motor assembly consists of a servo motor and a spring tension wheel; the servo motor is connected to the spring tension wheel, and both are fixed on the second longitudinal fixed bracket; the drafting roller consists of two pairs of front and rear pressure rollers, each pair of pressure rollers consists of two upper and lower rollers, and the two pairs of pressure rollers are respectively fixed on the third longitudinal fixed bracket and the fourth longitudinal fixed bracket by two support rods;

[0058] The process parameters of friction spinning are: combing roller speed 3500r / min, friction roller speed 4500r / min, Tencel fiber roving feeding speed 0.6m / min, conductive yarn winding speed 6m / min;

[0059] (4) The two flexible core-spun conductive yarns obtained in step (3) are wound once on the first tube and the second tube of the ring twisting machine through a winding machine to obtain a first core-spun conductive yarn and a second core-spun conductive yarn respectively; the elastic spandex yarn with a fineness of 150D is drawn by the front leather roller of the core yarn roller and the overfeed wheel and then output; the first core-spun conductive yarn sent out by the clockwise rotating first tube is fed to the front roller jaws through a yarn guide, merged with the output elastic spandex yarn on the central axis and wrapped around the elastic spandex yarn to form a positive single helical structure wrapped yarn, and then the second core-spun conductive yarn is reversely spirally wound by the counterclockwise rotating second tube, and each time it is wrapped, it is passed through a same-direction twister to form a secondary twist, and the twist of the ring twisting machine is set to 600T / 10cm, and finally it is wound onto a bobbin through a ring spindle with a spindle speed of 3000r / min, as shown in FIG. Figure 4 As shown, a forward and reverse double-wrapped spiral strain sensing composite yarn is obtained.

[0060] The twist of the final forward and reverse double-wrapped spiral strain sensing composite yarn is 600T / 10cm, and the strain sensing range is 0~130%; the sensing stretching response time is 30ms and the recovery time is 26ms at the strain of 110%; the electrical signal remains unchanged after being stretched 12,000 times at 110% strain.

[0061] The state of the positive and negative double-wrapped helical Tencel strain sensing composite yarn (80 tex coating thickness, 600T double-wrapped helical density) of Example 1 under different tensile strains and tensile speeds was tested. The specific process was as follows: the positive and negative double-wrapped helical strain sensing composite yarn was placed between the digital slides, the two ends were connected to the LRC bridge, and cyclic stretching was performed at a speed of 200 mm / min, and the capacitance changes at different strain degrees were recorded; Figure 8 As shown, the relative change of capacitance increases with the increase of tensile strain. It can be seen that the yarn capacitance sensor exhibits accurate and continuous sensing capability.

[0062] In order to evaluate the response consistency related to the stretching speed, the applied strain speed was changed at a constant strain of 110% and the corresponding capacitance changes were recorded, as shown in Fig. 9 As shown in the figure, it can be seen that the relative change value of capacitance ΔC / C0 remains almost unchanged at different stretching speeds (50mm / min, 100mm / min, 150mm / min, 200mm / min), which highlights the strong independence of the sensor from the strain speed, which is of great significance in different application scenarios.

[0063] Mechanical durability is a key parameter for evaluating the sensing performance of the sensor. The capacitance signal change of the forward and reverse double-wrapped spiral strain sensing composite yarn under 110% cyclic strain was then tested. Fig.11As shown, it can be seen that the sensor exhibits a consistent response to cyclic strain within 12,000 cycles, and the relative capacitance remains stable; this shows that the forward and reverse double-wrapped spiral Tencel strain sensing composite yarn has stable sensing performance and excellent durability.

[0064] At the same time, the forward and reverse double-wrapped spiral strain sensing composite yarn and the strand-type strain sensing yarn were subjected to cyclic tensile stability tests. The preparation process of the strand-type strain sensing yarn is as follows: two tubes of flexible core-spun conductive yarn are respectively placed in a doubling machine, and two parallel flexible core-spun conductive yarns are formed by the doubling machine and then wound onto yarn bobbins. Then, the yarn in the yarn bobbins is fed into a twisting machine, the twist of the twisting machine is set to 600T, and the twisting machine is started to obtain the strand-type strain sensing yarn; Fig.10 As shown in the figure, the structures of the two are stable before stretching. After 12,000 cycles of stretching, it was found that the positive and negative double-wrapped helix Tencel strain sensing composite yarn can still maintain a complete yarn structure, which is conducive to the stability of sensing performance; however, the ply-type strain sensing yarn has a displacement of its ply interlacing point after 4 hours of cyclic stretching. In summary, the sensing yarn prepared by the positive and negative double-wrapped helix has a more stable yarn structure than the traditional ply-type strain sensing yarn.

[0065] Response time is one of the important indicators of flexible sensors for practical applications. The electrical signals of the forward and reverse double-wrapped spiral strain sensing composite yarn during the stretching process from 110% to the recovery process are tested. Fig.12 As shown, the response time of the forward and reverse double-wrapped helical Tencel strain sensing composite yarn during the stretching process is 30 ms, and the sensing response time during the recovery process is 26 ms; therefore, its sensing response speed is fast, which is conducive to real-time feedback of sensing signals.

[0066] Comparative Example 1

[0067] A method for preparing a forward and reverse double-wrapped helical strain sensing composite yarn is basically the same as that in Example 1, except that the operation of step (2) is omitted, that is, the surface of the yarn coated with carbon nanotubes does not contain a PU coating.

[0068] The final forward and reverse double-wrapped spiral strain sensing composite yarn has a twist of 600T / 10cm and a strain sensing range of 0~130%; the sensing stretch response time is 35ms and the recovery time is 44ms at a strain of 110%; the electrical signal remains unchanged after being stretched 10,000 times at a strain of 110%, and the electrical signal fluctuates significantly after more than 10,000 times.

[0069] Comparing Comparative Example 1 with Example 1, it can be found that the forward and reverse double-wrapped spiral strain sensing composite yarn prepared in Comparative Example 1 shows a significant deterioration trend in tensile stability, accompanied by a significant extension of the response time. The difference lies in the preparation process. Specifically, Comparative Example 1 ignores the key step of PU coating the yarn coated with carbon nanotubes in the preparation process; therefore, when the forward and reverse double-wrapped spiral strain sensing composite yarn undergoes continuous stretching cycles, the conductive fibers inside it will experience repeated stress and friction, causing the carbon nanotubes originally attached to the fiber surface to fall off; the shedding of carbon nanotubes then destroys the conductive network constructed inside the yarn, and this structural damage inevitably weakens the conductive properties of the composite yarn. In summary, the sample of Comparative Example 1 lacking PU coating is inferior to Example 1 in both tensile stability and response speed, specifically manifested in significantly reduced tensile stability and significantly extended response time.

[0070] Comparative Example 2

[0071] A method for preparing a forward and reverse double-wrapped spiral strain sensing composite yarn is basically the same as that in Example 1, except that in step (3), the conductive yarn is omitted from passing through an adaptive yarn tension device and is directly fed between two friction rollers rotating in the same direction on a friction spinning machine.

[0072] The final forward and reverse double-wrapped spiral strain sensing composite yarn has a twist of 600T / 10cm and a strain sensing range of 0~130%; the sensing stretch response time is 47ms and the recovery time is 49ms at a strain of 110%; the electrical signal remains unchanged after 9000 times of stretching at 110% strain, and the electrical signal fluctuates significantly after more than 9000 times.

[0073] Since Comparative Example 2 did not undergo an adaptive yarn tension device during the preparation process, the CV value of the flexible core-spun conductive yarn prepared therefrom was 20.14%. Compared with the CV value of 16.74% of the flexible core-spun conductive yarn prepared in Example 1, the yarn uniformity decreased. This is because during the friction spinning process, the core yarn is subjected to a reverse rotational force during the fiber flow coating process, which affects the tension on the core yarn and causes uneven drawing speed. Uneven drawing speed of the core yarn affects the coating thickness of the outer fiber flow, making the yarn uneven.

[0074] Comparing Comparative Example 2 with Example 1, it can be found that the tensile stability of the forward and reverse double-wrapped spiral strain sensing composite yarn prepared in Comparative Example 2 is significantly reduced. This is because the flexible core-wrapped conductive yarn prepared without step (3) is uneven, which makes the interweaving points of the two flexible core-wrapped conductive yarns differ greatly. After continuous stretching and recovery cycles, due to the instability of the interweaving points, these interweaving points are difficult to accurately reset to the initial state, thereby causing the initial value of the electrical signal output of the forward and reverse double-wrapped spiral strain sensing composite yarn to fluctuate; in addition, due to the unevenness of the flexible core-wrapped conductive yarn, during the stretching and recovery process, the yarns are prone to slight relative displacement, and this slight displacement deformation further aggravates the extension of the sensing response time. In summary, due to the lack of preparation step (3), the tensile stability of the forward and reverse double-wrapped spiral strain sensing composite yarn prepared in Comparative Example 2 is significantly reduced and the sensing response time is correspondingly extended.

[0075] Comparative Example 3

[0076] A method for preparing a forward and reverse double-wrapped spiral strain sensing composite yarn is basically the same as that in Example 1, except that the operation of passing the elastic spandex yarn through an overfeeding wheel is omitted in step (4).

[0077] The final forward and reverse double-wrapped spiral strain sensing composite yarn has a twist of 600T / 10cm and a strain sensing range of 0~110%; the sensing stretch response time is 31ms and the recovery time is 35ms at a strain of 110%; the electrical signal remains unchanged after being stretched 10,000 times at a strain of 110%, and the electrical signal fluctuates significantly after more than 10,000 times.

[0078] By comparing Comparative Example 3 with Example 1, it can be found that the strain sensing range and stability of the forward and reverse double-wrapped spiral strain sensing composite yarn prepared in Comparative Example 3 are significantly reduced. This is because during the reverse double-wrapping process, tension is generated on the middle core yarn during the forward and reverse wrapping process, causing the yarn to deform, and the double-wrapped yarn will inevitably shrink after leaving the machine. Comparative Example 3 omits the operation of the overfeeding wheel, and the shrinkage problem cannot be avoided. After the shrinkage, the flexible core-wrapped conductive yarn on the outer layer of the forward and reverse double-wrapped spiral strain sensing composite yarn slips, making it difficult for the two core-wrapped conductive yarns to fit tightly on the spandex surface, thereby limiting its strain sensing range and sensing stability.

[0079] Example 2

[0080] A method for preparing a forward and reverse double-wrapped spiral strain sensing composite yarn, the specific steps are as follows:

[0081] (1) After unwinding a 30 tex Tencel yarn from a yarn bobbin, the yarn was passed through an oiler soaked in a carbon nanotube dispersion to obtain a carbon nanotube-coated yarn, which was then wound on a winding machine. The winding machine was started to wind the yarn into a bobbin, which was then dried at 70°C for 0.5 h. The coating and drying processes were repeated until the resistance per unit length of the carbon nanotube-coated yarn no longer changed.

[0082] Among them, the mass fraction of the carbon nanotube dispersion is 4wt%;

[0083] (2) Passing the coated carbon nanotube yarn through an oiler soaked in PU solution and winding it on a winding machine, starting the winding machine to wind the yarn into a tube, and then drying it at 70°C for 0.5h, repeating the coating and drying process to form a PU coating on the surface of the coated carbon nanotube yarn to obtain a conductive yarn;

[0084] Among them, the mass fraction of PU solution is 5wt%, and the content of carbon nanotubes in the conductive yarn is 8mg / tex;

[0085] (3) Winding the conductive yarn obtained in step (2) onto a bobbin and placing it on a bobbin support frame of a friction spinning machine, unwinding the conductive yarn from the bobbin and feeding it axially through an adaptive yarn tension device into the space between two friction rollers rotating in the same direction on the friction spinning machine, and at the same time feeding a Tencel fiber roving with a fineness of 780 tex into a roller drafting mechanism of the friction spinning machine; the Tencel fiber roving is combed into a Tencel fiber flow by the combing roller of the friction spinning machine, and the Tencel fiber flow enters the wedge-shaped area between the two friction rollers rotating in the same direction and condenses on the surface of the friction roller in the wedge-shaped area to form a condensed strand, and the two friction rollers rotating in the same direction apply upward and downward friction forces to the condensed strand respectively, reversely twisting the condensed strand and wrapping it around the surface of the conductive yarn, thereby forming a flexible core-wrapped conductive yarn with the conductive yarn as the core and the reversely twisted Tencel fiber as the shell, such as Figure 3 As shown, the fineness of the flexible core-spun conductive yarn is 46 tex and the CV value is 16.24%;

[0086] like Figure 1As shown, the adaptive yarn tension device consists of a fixed part 3, a tension control part and a drafting roller; the fixed part 3 includes a transverse fixed bracket and four longitudinal fixed brackets, the transverse fixed bracket is fixed in front of the friction roller of the friction spinning machine by screws, and the four longitudinal fixed brackets are sequentially recorded as the first longitudinal fixed bracket, the second longitudinal fixed bracket, the third longitudinal fixed bracket and the fourth longitudinal fixed bracket from left to right; the tension control part has the function of monitoring and regulating the tension of the yarn 1, and the tension control part includes a yarn tension sensor 2 and an automatic tensioning motor, the yarn tension sensor 2 and the automatic tensioning motor are respectively fixed on the first longitudinal fixed bracket and the second longitudinal fixed bracket, the yarn tension sensor is in front and the automatic tensioning motor is in the back; the automatic tensioning motor assembly consists of a servo motor 4 and a spring tension wheel 5; the servo motor 4 is connected to the spring tension wheel 5, and both are fixed on the second longitudinal fixed bracket; the drafting roller consists of two pairs of front and rear pressure rollers, namely the front pressure roller 6 and the rear pressure roller 7, wherein each pair of pressure rollers consists of two upper and lower rollers, and the two pairs of pressure rollers are respectively fixed on the third longitudinal fixed bracket and the fourth longitudinal fixed bracket by two support rods;

[0087] The process parameters of friction spinning are: combing roller speed 3500r / min, friction roller speed 4500r / min, Tencel fiber roving feeding speed 0.2m / min, conductive yarn winding speed 6m / min;

[0088] (4) The two flexible core-spun conductive yarns obtained in step (3) are wound once on the first tube and the second tube of the ring twisting machine through a winding machine to obtain a first core-spun conductive yarn and a second core-spun conductive yarn respectively; the elastic spandex yarn with a fineness of 150D is drawn by the front leather roller of the core yarn roller and the overfeed wheel and then output; the first core-spun conductive yarn sent out by the clockwise rotating first tube is fed to the front roller jaws through a yarn guide, merged with the output elastic spandex yarn on the central axis and wrapped around the elastic spandex yarn to form a positive single helical structure wrapped yarn, and then the second core-spun conductive yarn is reversely spirally wound by the counterclockwise rotating second tube, and each time after wrapping, it is passed through a same-direction twister to form a secondary twist, and the twist of the ring twisting machine is set to 400T / 10cm, and finally wound onto a bobbin through a ring spindle with a spindle speed of 3000r / min, as shown in FIG. Figure 4 As shown, a 400T / 10cm forward and reverse double-wrapped spiral strain sensing composite yarn was obtained.

[0089] The final forward and reverse double-wrapped spiral strain sensing composite yarn has a twist of 400T / 10cm and a strain sensing range of 0~130%; the sensing stretching response time is 37ms and the recovery time is 35ms at a strain of 110%; the electrical signal remains unchanged after being stretched 12,000 times at a strain of 110%.

[0090] Example 3

[0091] A method for preparing a forward and reverse double-wrapped spiral strain sensing composite yarn, the specific steps are as follows:

[0092] (1) After unwinding a 30 tex Tencel yarn from a yarn bobbin, the yarn was passed through an oiler soaked in a carbon nanotube dispersion to obtain a carbon nanotube-coated yarn, which was then wound on a winding machine. The winding machine was started to wind the yarn into a bobbin, which was then dried at 70°C for 0.5 h. The coating and drying processes were repeated until the resistance per unit length of the carbon nanotube-coated yarn no longer changed.

[0093] Among them, the mass fraction of the carbon nanotube dispersion is 4wt%;

[0094] (2) Passing the coated carbon nanotube yarn through an oiler soaked in PU solution and winding it on a winding machine, starting the winding machine to wind the yarn into a tube, and then drying it at 70°C for 0.5h, repeating the coating and drying process to form a PU coating on the surface of the coated carbon nanotube yarn to obtain a conductive yarn;

[0095] Among them, the mass fraction of PU solution is 5wt%, and the content of carbon nanotubes in the conductive yarn is 8mg / tex;

[0096] (3) Winding the conductive yarn obtained in step (2) onto a bobbin and placing it on a bobbin support frame of a friction spinning machine, unwinding the conductive yarn from the bobbin and feeding it axially through an adaptive yarn tension device into the space between two friction rollers rotating in the same direction on the friction spinning machine, and at the same time feeding a Tencel fiber roving with a fineness of 780 tex into a roller drafting mechanism of the friction spinning machine; the Tencel fiber roving is combed into a Tencel fiber flow by the combing roller of the friction spinning machine, and the Tencel fiber flow enters the wedge-shaped area between the two friction rollers rotating in the same direction and condenses on the surface of the friction roller in the wedge-shaped area to form a condensed strand, and the two friction rollers rotating in the same direction apply upward and downward friction forces to the condensed strand respectively, reversely twisting the condensed strand and wrapping it around the surface of the conductive yarn, thereby forming a flexible core-wrapped conductive yarn with the conductive yarn as the core and the reversely twisted Tencel fiber as the shell, such as Figure 3 As shown, the fineness of the flexible core-spun conductive yarn is 64tex and the CV value is 16.8%;

[0097] The adaptive yarn tension device consists of a fixed part, a tension control part and a drafting roller; the fixed part includes a transverse fixed bracket and four longitudinal fixed brackets, the transverse fixed bracket is fixed in front of the friction roller of the friction spinning machine by screws, and the four longitudinal fixed brackets are respectively recorded as the first longitudinal fixed bracket, the second longitudinal fixed bracket, the third longitudinal fixed bracket and the fourth longitudinal fixed bracket from left to right; the tension control part includes a yarn tension sensor and an automatic tensioning motor, the yarn tension sensor and the automatic tensioning motor are respectively fixed on the first longitudinal fixed bracket and the second longitudinal fixed bracket, the yarn tension sensor is in front and the automatic tensioning motor is in the back; the automatic tensioning motor assembly consists of a servo motor and a spring tension wheel; the servo motor is connected to the spring tension wheel, and both are fixed on the second longitudinal fixed bracket; the drafting roller consists of two pairs of front and rear pressure rollers, each pair of pressure rollers consists of two upper and lower rollers, and the two pairs of pressure rollers are respectively fixed on the third longitudinal fixed bracket and the fourth longitudinal fixed bracket by two support rods;

[0098] The process parameters of friction spinning are: combing roller speed 3500r / min, friction roller speed 4500r / min, Tencel fiber roving feeding speed 0.4m / min, conductive yarn winding speed 6m / min;

[0099] (4) The two flexible core-spun conductive yarns obtained in step (3) are wound once on the first tube and the second tube of the ring twisting machine through a winding machine to obtain a first core-spun conductive yarn and a second core-spun conductive yarn respectively; the elastic spandex yarn with a fineness of 150D is drawn by the front leather roller of the core yarn roller and the overfeed wheel and then output; the first core-spun conductive yarn sent out by the clockwise rotating first tube is fed to the front roller jaws through a yarn guide, merged with the output elastic spandex yarn on the central axis and wrapped around the elastic spandex yarn to form a positive single helical structure wrapped yarn, and then the second core-spun conductive yarn is reversely spirally wound by the counterclockwise rotating second tube, and each time it is wrapped, it is passed through a same-direction twister to form a secondary twist, and the twist of the ring twisting machine is set to 500T / 10cm, and finally it is wound onto a bobbin through a ring spindle with a spindle speed of 3000r / min, as shown in FIG. Figure 4 As shown, a forward and reverse double-wrapped spiral strain sensing composite yarn is obtained.

[0100] The final forward and reverse double-wrapped spiral strain sensing composite yarn has a twist of 500T / 10cm and a strain sensing range of 0~130%; the sensing stretching response time is 42ms and the recovery time is 46ms at a strain of 110%; the electrical signal remains unchanged after being stretched 12,000 times at a strain of 110%.

[0101] Example 4

[0102] A method for preparing a forward and reverse double-wrapped spiral strain sensing composite yarn, the specific steps are as follows:

[0103] (1) After unwinding a 30 tex Tencel yarn from a yarn bobbin, the yarn was passed through an oiler soaked in a carbon nanotube dispersion to obtain a carbon nanotube-coated yarn, which was then wound on a winding machine. The winding machine was started to wind the yarn into a bobbin, which was then dried at 70°C for 0.5 h. The coating and drying processes were repeated until the resistance per unit length of the carbon nanotube-coated yarn no longer changed.

[0104] Among them, the mass fraction of the carbon nanotube dispersion is 4wt%;

[0105] (2) Passing the coated carbon nanotube yarn through an oiler soaked in PU solution and winding it on a winding machine, starting the winding machine to wind the yarn into a tube, and then drying it at 70°C for 0.5h, repeating the coating and drying process to form a PU coating on the surface of the coated carbon nanotube yarn to obtain a conductive yarn;

[0106] Among them, the mass fraction of PU solution is 5wt%, and the content of carbon nanotubes in the conductive yarn is 8mg / tex;

[0107] (3) Winding the conductive yarn obtained in step (2) onto a bobbin and placing it on a bobbin support frame of a friction spinning machine, unwinding the conductive yarn from the bobbin and feeding it axially through an adaptive yarn tension device into a space between two friction rollers rotating in the same direction on the friction spinning machine, and at the same time feeding a Tencel fiber roving with a fineness of 780 tex into a roller drafting mechanism of the friction spinning machine; the Tencel fiber roving is combed into a Tencel fiber flow by the combing roller of the friction spinning machine, and the Tencel fiber flow enters a wedge-shaped area between the two friction rollers rotating in the same direction and condenses on the surface of the friction roller in the wedge-shaped area to form a condensed whisker, and the two friction rollers rotating in the same direction apply upward and downward friction forces to the condensed whisker respectively, reversely twisting the condensed whisker and wrapping it around the surface of the conductive yarn, thereby forming a flexible core-wrapped conductive yarn with the conductive yarn as the core and the Tencel fiber reversely twisted and wrapped as the shell, the fineness of the flexible core-wrapped conductive yarn is 99 tex, and the CV value is 16.56%;

[0108] The adaptive yarn tension device consists of a fixed part, a tension control part and a drafting roller; the fixed part includes a transverse fixed bracket and four longitudinal fixed brackets, the transverse fixed bracket is fixed in front of the friction roller of the friction spinning machine by screws, and the four longitudinal fixed brackets are respectively recorded as the first longitudinal fixed bracket, the second longitudinal fixed bracket, the third longitudinal fixed bracket and the fourth longitudinal fixed bracket from left to right; the tension control part includes a yarn tension sensor and an automatic tensioning motor, the yarn tension sensor and the automatic tensioning motor are respectively fixed on the first longitudinal fixed bracket and the second longitudinal fixed bracket, the yarn tension sensor is in front and the automatic tensioning motor is in the back; the automatic tensioning motor assembly consists of a servo motor and a spring tension wheel; the servo motor is connected to the spring tension wheel, and both are fixed on the second longitudinal fixed bracket; the drafting roller consists of two pairs of front and rear pressure rollers, each pair of pressure rollers consists of two upper and lower rollers, and the two pairs of pressure rollers are respectively fixed on the third longitudinal fixed bracket and the fourth longitudinal fixed bracket by two support rods;

[0109] The process parameters of friction spinning are: combing roller speed 3500r / min, friction roller speed 4500r / min, Tencel fiber roving feeding speed 0.8m / min, conductive yarn winding speed 6m / min;

[0110] (4) The two flexible core-spun conductive yarns obtained in step (3) are wound once on the first tube and the second tube of the ring twisting machine through a winding machine to obtain a first core-spun conductive yarn and a second core-spun conductive yarn respectively; the elastic spandex yarn with a fineness of 150D is stretched by the front leather roller of the core yarn roller and the overfeed wheel and then output; the first core-spun conductive yarn sent out by the clockwise rotating first tube is fed to the front roller jaws through a yarn guide, merged with the output elastic spandex yarn on the central axis and wrapped around the elastic spandex yarn to form a positive single helical structure wrapped yarn, and then the second core-spun conductive yarn is reversely helically wound by the counterclockwise rotating second tube, and after each wrapping, it is passed through a same-direction twister to form a secondary twist, and the twist of the ring twisting machine is set to 700T / 10cm. Finally, it is wound onto a bobbin through a ring spindle with a spindle speed of 3000r / min to obtain a positive and reverse double-wrapped helical strain sensing composite yarn.

[0111] The final forward and reverse double-wrapped spiral strain sensing composite yarn has a twist of 700T / 10cm and a strain sensing range of 0~130%; the sensing stretching response time is 51ms and the recovery time is 43ms at a strain of 110%; the electrical signal remains unchanged after being stretched 12,000 times at a strain of 110%.

[0112] The forward and reverse double-wrapped spiral strain sensing composite yarns with different friction-spun coating thicknesses in Examples 1 to 4 were connected to a capacitance tester, and a relative capacitance-time curve was generated according to the capacitance value detected by the capacitance tester. The yarns were stretched to 120% of their original length at a speed of 200 mm / min. The results are shown in FIG. Figure 5 As shown, it can be seen that when the coating thickness increases until the fineness of the flexible core-wrapped conductive yarn reaches 80tex, the relative change in capacitance of the forward and reverse double-wrapped spiral Tencel strain sensing composite yarn reaches a maximum value of 16%, and then the change is negligible, which has excellent strain sensing performance.

[0113] Example 5

[0114] A method for preparing a forward and reverse double-wrapped spiral strain sensing composite yarn, the specific steps are as follows:

[0115] (1) After unwinding a 30 tex Tencel yarn from a yarn bobbin, the yarn was passed through an oiler soaked in a carbon nanotube dispersion to obtain a carbon nanotube-coated yarn, which was then wound on a winding machine. The winding machine was started to wind the yarn into a bobbin, which was then dried at 70°C for 0.5 h. The coating and drying processes were repeated until the resistance per unit length of the carbon nanotube-coated yarn no longer changed.

[0116] Among them, the mass fraction of the carbon nanotube dispersion is 4wt%;

[0117] (2) Passing the coated carbon nanotube yarn through an oiler soaked in PU solution and winding it on a winding machine, starting the winding machine to wind the yarn into a tube, and then drying it at 70°C for 0.5h, repeating the coating and drying process to form a PU coating on the surface of the coated carbon nanotube yarn to obtain a conductive yarn;

[0118] Among them, the mass fraction of PU solution is 5wt%, and the content of carbon nanotubes in the conductive yarn is 8mg / tex;

[0119] (3) Winding the conductive yarn obtained in step (2) onto a bobbin and placing it on a bobbin support frame of a friction spinning machine, unwinding the conductive yarn from the bobbin and feeding it axially through an adaptive yarn tension device into a space between two friction rollers rotating in the same direction on the friction spinning machine, and at the same time feeding a Tencel fiber roving with a fineness of 780 tex into a roller drafting mechanism of the friction spinning machine; the Tencel fiber roving is combed into a Tencel fiber flow by the combing roller of the friction spinning machine, and the Tencel fiber flow enters a wedge-shaped area between the two friction rollers rotating in the same direction and condenses on the surface of the friction roller in the wedge-shaped area to form a condensed whisker, and the two friction rollers rotating in the same direction apply upward and downward friction forces to the condensed whisker respectively, reversely twisting the condensed whisker and wrapping it around the surface of the conductive yarn, thereby forming a flexible core-wrapped conductive yarn with the conductive yarn as the core and the Tencel fiber reversely twisted and wrapped as the shell, wherein the fineness of the flexible core-wrapped conductive yarn is 80 tex and the CV value is 16.47%;

[0120] Among them, the adaptive yarn tension device consists of a fixed part, a tension control part and a drafting roller; the fixed part includes a transverse fixed bracket and four longitudinal fixed brackets, the transverse fixed bracket is fixed in front of the friction roller of the friction spinning machine by screws, and the four longitudinal fixed brackets are recorded as the first longitudinal fixed bracket, the second longitudinal fixed bracket, the third longitudinal fixed bracket and the fourth longitudinal fixed bracket from left to right; the tension control part includes a yarn tension sensor and an automatic tensioning motor, the yarn tension sensor and the automatic tensioning motor are respectively fixed on the first longitudinal fixed bracket and the second longitudinal fixed bracket, the yarn tension sensor is in front and the automatic tensioning motor is in the back; the automatic tensioning motor assembly consists of a servo motor and a spring tension wheel; the servo motor is connected to the spring tension wheel, and both are fixed on the second longitudinal fixed bracket; the drafting roller consists of two pairs of front and rear pressure rollers, each pair of pressure rollers consists of two upper and lower rollers, and the two pairs of pressure rollers are respectively fixed on the third longitudinal fixed bracket and the fourth longitudinal fixed bracket by two support rods;

[0121] The process parameters of friction spinning are: combing roller speed 3500r / min, friction roller speed 4500r / min, Tencel fiber roving feeding speed 0.6m / min, conductive yarn winding speed 6m / min;

[0122] (4) The two flexible core-spun conductive yarns obtained in step (2) are wound once on the first tube and the second tube of the ring twisting machine through a winding machine to obtain a first core-spun conductive yarn and a second core-spun conductive yarn respectively; the elastic spandex yarn with a fineness of 150D is stretched by the front leather roller of the core yarn roller and the overfeed wheel and then output; the first core-spun conductive yarn sent out by the clockwise rotating first tube is fed to the front roller jaws through a yarn guide, merged with the output elastic spandex yarn on the central axis and wrapped around the elastic spandex yarn to form a positive single helical structure wrapped yarn, and then the second core-spun conductive yarn is reversely helically wound by the counterclockwise rotating second tube, and after each wrapping, it is passed through a co-directional twister to form a secondary twist, and the twist of the ring twisting machine is set to 400T / 10cm respectively, and finally wound onto a bobbin through a ring spindle with a spindle speed of 3000r / min to obtain a positive and reverse double-wrapped helical strain sensing composite yarn.

[0123] The final forward and reverse double-wrapped spiral strain sensing composite yarn has a twist of 400T / 10cm and a strain sensing range of 0~130%; the sensing stretch response time is 47ms and the recovery time is 46ms at a strain of 110%; the electrical signal remains unchanged after being stretched 12,000 times at a strain of 110%.

[0124] Example 6

[0125] A method for preparing a forward and reverse double-wrapped helical strain sensing composite yarn is basically the same as that of Example 5, except that in step (4), the twist of the ring twisting machine is set to 500T / 10cm.

[0126] The final forward and reverse double-wrapped spiral strain sensing composite yarn has a twist of 500T / 10cm and a strain sensing range of 0~130%; the sensing stretch response time is 39ms and the recovery time is 46ms at a strain of 110%; the electrical signal remains unchanged after being stretched 12,000 times at a strain of 110%.

[0127] Example 7

[0128] A method for preparing a forward and reverse double-wrapped helical strain sensing composite yarn is basically the same as that of Example 5, except that in step (4), the twist of the ring twisting machine is set to 700T / 10cm.

[0129] The final forward and reverse double-wrapped spiral strain sensing composite yarn has a twist of 700T / 10cm and a strain sensing range of 0~130%; the sensing stretch response time is 46ms and the recovery time is 49ms at a strain of 110%; the electrical signal remains unchanged after being stretched 12,000 times at a strain of 110%.

[0130] like Figure 6 As shown in the figure, four kinds of forward and reverse double-wrapped helical strain sensing composite yarns with different twists (400T / 10cm, 500T / 10cm, 600T / 10cm and 700T / 10cm) were finally prepared. The forward and reverse double-wrapped helical strain sensing composite yarns with different double-wrapped twists in Example 1 and Examples 5 to 7 were respectively connected to a capacitance tester, and a relative capacitance-time curve was generated according to the capacitance value detected by the capacitance tester. The yarns were stretched to 120% of their original length at a speed of 200mm / min. The results are shown in FIG. Figure 7 As shown, it can be seen that the relative change value of capacitance increases with the increase of double-wrap density, reaching a maximum value of 16% at 600T / 10cm, with the best sensing performance, and then the value decreases accordingly. This is because when the double-wrap twist is too low, the number of interlacing points of the flexible core conductive yarn is insufficient, resulting in a small electrical signal; when the double-wrap twist is too high, the deformation of the interlacing points is small after the yarn is stretched, resulting in a small change in the electrical signal.

[0131] Example 8

[0132] A method for preparing a forward and reverse double-wrapped spiral strain sensing composite yarn, the specific steps are as follows:

[0133] (1) Cotton yarn with a fineness of 30 tex was unwound from a yarn bobbin and passed through an oiler soaked in a carbon nanotube dispersion to obtain a yarn coated with carbon nanotubes, which was then wound on a winding machine. The winding machine was started to wind the yarn into a bobbin, which was then dried at 60°C for 1 h. The coating and drying processes were repeated until the resistance per unit length of the yarn coated with carbon nanotubes no longer changed.

[0134] Among them, the mass fraction of the carbon nanotube dispersion is 2wt%;

[0135] (2) Passing the coated carbon nanotube yarn through an oiler soaked in PU solution and winding it on a winding machine, starting the winding machine to wind the yarn into a tube, and then drying it at 60°C for 1 hour, repeating the coating and drying process to form a PU coating on the surface of the coated carbon nanotube yarn to obtain a conductive yarn;

[0136] Among them, the mass fraction of PU solution is 4wt%, and the content of carbon nanotubes in the conductive yarn is 4mg / tex;

[0137] (3) Winding the conductive yarn obtained in step (2) onto a bobbin and placing it on a bobbin support frame of a friction spinning machine, unwinding the conductive yarn from the bobbin and feeding it axially through an adaptive yarn tension device into the space between two friction rollers rotating in the same direction on the friction spinning machine, and at the same time feeding a wool fiber roving with a fineness of 780 tex into a roller drafting mechanism of the friction spinning machine; the wool fiber roving is combed into a wool fiber flow by the combing roller of the friction spinning machine, and the wool fiber flow enters the wedge-shaped area between the two friction rollers rotating in the same direction and condenses on the surface of the friction roller in the wedge-shaped area to form a condensed whisker, and the two friction rollers rotating in the same direction apply upward and downward friction forces to the condensed whisker respectively, reversely twisting the condensed whisker and wrapping it around the surface of the conductive yarn, thereby forming a flexible core-wrapped conductive yarn with the conductive yarn as the core and the reversely twisted and wrapped wool fiber as the shell, the fineness of the flexible core-wrapped conductive yarn is 32 tex, and the CV value is 16.88%;

[0138] The adaptive yarn tension device consists of a fixed part, a tension control part and a drafting roller; the fixed part includes a transverse fixed bracket and four longitudinal fixed brackets, the transverse fixed bracket is fixed in front of the friction roller of the friction spinning machine by screws, and the four longitudinal fixed brackets are respectively recorded as the first longitudinal fixed bracket, the second longitudinal fixed bracket, the third longitudinal fixed bracket and the fourth longitudinal fixed bracket from left to right; the tension control part includes a yarn tension sensor and an automatic tensioning motor, the yarn tension sensor and the automatic tensioning motor are respectively fixed on the first longitudinal fixed bracket and the second longitudinal fixed bracket, the yarn tension sensor is in front and the automatic tensioning motor is in the back; the automatic tensioning motor assembly consists of a servo motor and a spring tension wheel; the servo motor is connected to the spring tension wheel, and both are fixed on the second longitudinal fixed bracket; the drafting roller consists of two pairs of front and rear pressure rollers, each pair of pressure rollers consists of two upper and lower rollers, and the two pairs of pressure rollers are respectively fixed on the third longitudinal fixed bracket and the fourth longitudinal fixed bracket by two support rods;

[0139] The process parameters of friction spinning are: combing roller speed 3000 r / min, friction roller speed 4000 r / min, wool fiber roving feeding speed 0.1 m / min, conductive yarn winding speed 5 m / min;

[0140] (4) The two flexible core-spun conductive yarns obtained in step (3) are wound once on the first tube and the second tube of the ring twisting machine through a winding machine to obtain a first core-spun conductive yarn and a second core-spun conductive yarn respectively; the elastic spandex yarn with a fineness of 100D is stretched by the front leather roller of the core yarn roller and the overfeed wheel and then output; the first core-spun conductive yarn sent out by the clockwise rotating first tube is fed to the front roller jaws through a yarn guide, merged with the output elastic spandex yarn on the central axis and wrapped around the elastic spandex yarn to form a positive single helical structure wrapped yarn, and then the second core-spun conductive yarn is reversely helically wound through the counterclockwise rotating second tube, and after each wrapping, it is passed through a same-direction twister to form a secondary twist, and the twist of the ring twisting machine is set to 300T / 10cm. Finally, it is wound onto a bobbin through a ring spindle with a spindle speed of 3000r / min to obtain a positive and reverse double-wrapped helical strain sensing composite yarn.

[0141] The twist of the final forward and reverse double-wrapped spiral strain sensing composite yarn is 300T / 10cm, and the strain sensing range is 0~120%; the sensing stretching response time is 47ms and the recovery time is 39ms at the strain of 110%; the electrical signal remains unchanged after being stretched 12,000 times at 110% strain.

[0142] Example 9

[0143] A method for preparing a forward and reverse double-wrapped spiral strain sensing composite yarn, the specific steps are as follows:

[0144] (1) After unwinding a nylon yarn with a fineness of 30 tex from a yarn bobbin, the yarn is passed through an oiler soaked in a carbon nanotube dispersion to obtain a yarn coated with carbon nanotubes, which is then wound on a winding machine. The winding machine is started to wind the yarn into a bobbin, which is then dried at 80°C for 0.5 h. The coating and drying processes are repeated until the resistance per unit length of the yarn coated with carbon nanotubes no longer changes.

[0145] Among them, the mass fraction of the carbon nanotube dispersion is 5wt%;

[0146] (2) Passing the coated carbon nanotube yarn through an oiler soaked in PU solution and winding it on a winding machine, starting the winding machine to wind the yarn into a tube, and then drying it at 80°C for 0.5h, repeating the coating and drying process to form a PU coating on the surface of the coated carbon nanotube yarn to obtain a conductive yarn;

[0147] Among them, the mass fraction of PU solution is 4wt%, and the content of carbon nanotubes in the conductive yarn is 10mg / tex;

[0148] (3) The conductive yarn obtained in step (2) is wound onto a bobbin and placed on a bobbin support frame of a friction spinning machine, so that the conductive yarn is unwound from the bobbin and fed axially through an adaptive yarn tension device into a space between two friction rollers rotating in the same direction on the friction spinning machine, and at the same time, a wool fiber roving with a fineness of 780 tex is fed into a roller drafting mechanism of the friction spinning machine; the wool fiber roving is combed into a wool fiber flow by the combing roller of the friction spinning machine, and the wool fiber flow enters a wedge-shaped area between the two friction rollers rotating in the same direction and condenses on the surface of the friction roller in the wedge-shaped area to form a condensed whisker, and the two friction rollers rotating in the same direction apply upward and downward friction forces to the condensed whisker respectively, reversely twist the condensed whisker and wrap it around the surface of the conductive yarn, thereby forming a flexible core-wrapped conductive yarn with the conductive yarn as the core and the reversely twisted and wrapped wool fiber as the shell, the fineness of the flexible core-wrapped conductive yarn is 118 tex, and the CV value is 16.13%.

[0149] The adaptive yarn tension device consists of a fixed part, a tension control part and a drafting roller; the fixed part includes a transverse fixed bracket and four longitudinal fixed brackets, the transverse fixed bracket is fixed in front of the friction roller of the friction spinning machine by screws, and the four longitudinal fixed brackets are respectively recorded as the first longitudinal fixed bracket, the second longitudinal fixed bracket, the third longitudinal fixed bracket and the fourth longitudinal fixed bracket from left to right; the tension control part includes a yarn tension sensor and an automatic tensioning motor, the yarn tension sensor and the automatic tensioning motor are respectively fixed on the first longitudinal fixed bracket and the second longitudinal fixed bracket, the yarn tension sensor is in front and the automatic tensioning motor is in the back; the automatic tensioning motor assembly consists of a servo motor and a spring tension wheel; the servo motor is connected to the spring tension wheel, and both are fixed on the second longitudinal fixed bracket; the drafting roller consists of two pairs of front and rear pressure rollers, each pair of pressure rollers consists of two upper and lower rollers, and the two pairs of pressure rollers are respectively fixed on the third longitudinal fixed bracket and the fourth longitudinal fixed bracket by two support rods;

[0150] The process parameters of friction spinning are: combing roller speed 5000r / min, friction roller speed 5000r / min, wool fiber roving feeding speed 1m / min, conductive yarn winding speed 8m / min;

[0151] (4) The two flexible core-spun conductive yarns obtained in step (3) are wound once on the first tube and the second tube of the ring twisting machine through a winding machine to obtain a first core-spun conductive yarn and a second core-spun conductive yarn respectively; the elastic spandex yarn with a fineness of 200D is stretched by the front leather roller of the core yarn roller and the overfeed wheel and then output; the first core-spun conductive yarn sent out by the clockwise rotating first tube is fed to the front roller jaws through a yarn guide, merged with the output elastic spandex yarn on the central axis and wrapped around the elastic spandex yarn to form a positive single helical structure wrapped yarn, and then the second core-spun conductive yarn is reversely helically wound by the counterclockwise rotating second tube, and after each wrapping, it is passed through a co-directional twister to form a secondary twist, and the twist of the ring twisting machine is set to 800T / 10cm. Finally, it is wound onto a bobbin through a ring spindle with a spindle speed of 3000r / min to obtain a positive and reverse double-wrapped helical strain sensing composite yarn.

[0152] The twist of the final forward and reverse double-wrapped spiral strain sensing composite yarn is 800T / 10cm, and the strain sensing range is 0~130%; the sensing stretching response time is 48ms and the recovery time is 42ms at the strain of 110%; the electrical signal remains unchanged after being stretched 12,000 times at 110% strain.

[0153] Example 10

[0154] The application of a forward and reverse double-wrapped spiral strain sensing composite yarn in smart wearables, the specific process is as follows:

[0155] The positive and negative double-wrapped helical wire strain sensing composite yarn of Example 1 is respectively fixed on the movable joints of the five fingers corresponding to the elastic gloves, and a wearable device is formed by integrating five sensors.

[0156] Since the flexion arrangements of the five fingers are significantly different, the relative capacitance change signals caused by finger bending can be used to distinguish digits or gesture recognition in real time.

[0157] like Fig.13 The capacitive signal monitored during the gesture recognition demonstration is shown. It can be seen that different combinations of bending or stretching between the five sensors can distinguish the gestures of each letter (from A to J). The five output channel curves represent different fingers (thumb, index finger, middle finger, ring finger and pinky finger). The height of the line represents the relative capacitance change value reading under different bending degrees. Taking gesture "A" as an example, at this time, the index finger, middle finger, ring finger and pinky finger are fully bent, and the thumb is fully extended; therefore, only the thumb sensor detects an electrical signal change of 0, and the sensors of other fingers show obvious electrical signal changes.

[0158] In summary, the gesture recognition gloves integrated with positive and negative double-wrapped spiral strain sensing composite yarn have high sensitivity and accuracy.

Claims

1. A method for preparing a forward and reverse double-wrapped spiral strain sensing composite yarn, characterized in that The steps include: (1) passing the yarn through an oiler soaked in a carbon nanotube dispersion to obtain a yarn coated with carbon nanotubes, and then drying it, repeating the coating and drying process until the resistance per unit length no longer changes; then forming a PU coating on the surface of the yarn coated with carbon nanotubes according to the same method to obtain a conductive yarn; (2) Winding the conductive yarn obtained in step (1) onto a bobbin and placing it on a bobbin support frame of a friction spinning machine, unwinding the conductive yarn from the bobbin and feeding it axially through an adaptive yarn tension device into a space between two friction rollers rotating in the same direction on the friction spinning machine, and at the same time feeding the flexible fiber roving into a roller drafting mechanism of the friction spinning machine; the flexible fiber roving is combed into a flexible fiber flow by the combing roller of the friction spinning machine, and the flexible fiber flow enters a wedge-shaped area between the two friction rollers rotating in the same direction, and condenses on the surface of the friction roller in the wedge-shaped area to form a condensed strand; the two friction rollers rotating in the same direction apply upward and downward friction forces to the condensed strand respectively, reversely twisting the condensed strand and wrapping it around the surface of the conductive yarn, thereby forming a flexible core-wrapped conductive yarn with the conductive yarn as the core and the reversely twisted and wrapped flexible fiber as the shell; The adaptive yarn tension device is composed of a fixed part, a tension control part and a drafting roller; the fixed part includes a transverse fixed bracket and four longitudinal fixed brackets, the transverse fixed bracket is fixed in front of the friction roller of the friction spinning machine, and the four longitudinal fixed brackets are sequentially recorded as the first longitudinal fixed bracket, the second longitudinal fixed bracket, the third longitudinal fixed bracket and the fourth longitudinal fixed bracket; the tension control part includes a yarn tension sensor and an automatic tensioning motor, the yarn tension sensor and the automatic tensioning motor are respectively fixed on the first longitudinal fixed bracket and the second longitudinal fixed bracket; the automatic tensioning motor assembly is composed of a servo motor and a spring tension wheel; the servo motor is connected to the spring tension wheel, and both are fixed on the second longitudinal fixed bracket; the drafting roller is composed of two pairs of front and rear pressure rollers, and the two pairs of pressure rollers are respectively fixed on the third longitudinal fixed bracket and the fourth longitudinal fixed bracket by two support rods; (3) Winding the two flexible core-spun conductive yarns obtained in step (2) onto a first tube and a second tube of a ring twisting machine to obtain a first core-spun conductive yarn and a second core-spun conductive yarn, respectively; The elastic spandex yarn is drawn through the front leather roller of the core yarn roller and the overfeed wheel and then output. The first core-wrapped conductive yarn sent out by the first clockwise rotating tube is fed to the jaws of the front roller through the yarn guide, merges with the output elastic spandex yarn on the central axis and is wrapped around the elastic spandex yarn to form a forward single helical structure wrapped yarn, and then the second core-wrapped conductive yarn is reversely helically wrapped through the second counterclockwise rotating tube. After each wrapping, it passes through the same-direction twister to form a secondary twist, and finally a forward and reverse double-wrapped helical strain sensing composite yarn is obtained.

2. The method for preparing a forward and reverse double-wrapped spiral strain sensing composite yarn according to claim 1, characterized in that: The mass fraction of the carbon nanotube dispersion in step (1) is 2-5wt%, and the content of carbon nanotubes in the conductive yarn is 1-10mg / tex.

3. The method for preparing a forward and reverse double-wrapped spiral strain sensing composite yarn according to claim 1, characterized in that: In step (1), the yarn is cotton yarn, tencel yarn or nylon yarn, and the fineness of the yarn is 30tex.

4. The method for preparing a forward and reverse double-wrapped spiral strain sensing composite yarn according to claim 1, characterized in that: In step (1), the drying temperature is 60-80° C. and the drying time is 0.5-1 h.

5. The method for preparing a forward and reverse double-wrapped spiral strain sensing composite yarn according to claim 1, characterized in that: In step (2), the flexible fiber is cotton fiber, wool fiber or Tencel fiber, and the fineness of the flexible core-spun conductive yarn is 30 to 120 tex.

6. The method for preparing a forward and reverse double-wrapped spiral strain sensing composite yarn according to claim 1, characterized in that: The process parameters of friction spinning in step (2) are: combing roller speed 3000-5000 r / min, friction roller speed 4000-5000 r / min, flexible fiber roving feeding speed 0.1-1.0 m / min, conductive yarn curling speed 5-8 m / min.

7. The method for preparing a forward and reverse double-wrapped spiral strain sensing composite yarn according to claim 1, characterized in that: In step (3), the fineness of the elastic spandex yarn is 100D, 150D or 200D.

8. The forward and reverse double-wrapped spiral strain sensing composite yarn prepared by the method according to any one of claims 1 to 7, characterized in that: The twist of the forward and reverse double-wrapped helical strain sensing composite yarn is 300-800T / 10cm; The strain sensing range of the reverse double-wrapped spiral strain sensing composite yarn is 0-130%. When the strain is 110%, the sensing stretching response time is 30-51ms and the recovery time is 26-46ms. After being stretched 12,000 times at 110% strain, the electrical signal remains unchanged.

9. Application of the forward and reverse double-wrapped spiral strain sensing composite yarn as claimed in claim 8 in smart wearables.

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