Preparation method and application of core-sheath type intelligent fiber with composite functions of elastic strain induction and temperature regulation

Abstract

The invention relates to a core-sheath type intelligent fiber with an elastic strain sensing and temperature adjusting composite function and a preparation method and application thereof.The intelligent fiber is prepared through a one-step coaxial wet spinning technology and comprises an elastomer sheath layer and a core layer formed by evenly mixing an elastomer with conductive filler and phase change filler, the conductive filler is a carbon material or a metal material, and the phase change temperature of the phase change filler is 20-40 DEG C; the conductive filler accounts for 1%-5% of the mass of the core layer, and the advancing speed ratio of the sheath layer to the core layer is (0.5-3): 1. The prepared fiber has an obvious core-sheath structure and good elasticity, conductivity and temperature adjustment performance, and by weaving the fiber into textiles or embedding the fiber into clothes, not only can health signals of a human body be monitored, but also the ambient temperature around the human body is adjusted, so that the fiber is more comfortable to wear.

Description

Technical Field

[0001] The present invention relates to the technical field of intelligent fibers, and in particular to a preparation method and application of a core-sheath type elastic strain sensing temperature regulating fiber. Background Art

[0002] Smart fibers include four major directions: energy-harvesting smart fibers, energy-harvesting / storage fibers, smart luminous fibers, and fiber-type smart sensors. Smart fibers are widely used in motion sensing, personal health monitoring, smart robots, and human-computer interaction. However, there are still many difficulties to be overcome in the product stability and industrial production of smart fibers.

[0003] Thermostatic fiber belongs to a type of intelligent fiber that collects and releases energy. The fiber mainly loads phase change material in a certain way, and uses the phase change material to absorb and release latent heat during the phase change process to adjust the temperature. Embedding or weaving thermostatic fiber into textiles can improve the wearing comfort of textiles. However, due to the different ways of loading phase change materials and the differences in fiber preparation processes, thermostatic fiber generally has the problem of leakage of phase change materials, resulting in poor durability of phase change thermostatic materials. In order to solve the problem of leakage of phase change materials, the invention patent application with publication number CN 113235299A discloses a method of preparing porous polyurethane fibers by freeze drying, and then filling the phase change material into the porous structure by vacuum impregnation, which effectively prevents the leakage of phase change materials. However, this method is complicated, not easy to industrialize, and has a single function.

[0004] Another type of sensor-type smart fiber, the improvement of smart fibers is mainly focused on how to give fibers conductive properties to achieve response and transmission of electrical signals. Sensor-type smart fibers generally monitor various physiological signals of the human body through weak electrical signals, realizing personal health status monitoring, especially in the field of biomedicine, and have gradually shifted from basic medical care monitoring to clinical evaluation of diseases. For example, the invention patent application with publication number CN 106705829A discloses a fiber with a spiral double-coated structure obtained by spirally winding the fiber on the core yarn, and then coating the fiber with a conductive layer to obtain a flexible wearable conductive fiber sensor, which has a complex structure, cumbersome preparation process, and poor wearing comfort. For example, the invention patent application with publication number CN 113174755A discloses a method of preparing polyurethane fibers by wet spinning, then making holes on the fibers by freeze drying, and then loading phase change materials in the pore structure to obtain polyurethane fibers containing phase change materials; then the conductive liquid is coated on the surface of the above-mentioned fiber to obtain an elastic fiber with both temperature sensing and electrothermal effects. Although this method solves the leakage problem of phase change materials and gives the fiber multifunctionality, the coated conductive layer has poor washability and reduces the flexibility of the fiber. The process is complicated and it is difficult to use directly as a wearable flexible sensor for the human body.

[0005] It can be seen that the existing methods for preparing composite fibers with intelligent sensing functions mostly use post-finishing methods to give fibers temperature regulating properties and conductive properties. This post-finishing method has high requirements on equipment in the preparation process, and the prepared fibers have problems of instability and poor durability. Summary of the invention

[0006] Based on the deficiencies of existing technologies and materials, the present invention successfully prepares smart fibers with core-sheath type elastic strain sensing and temperature regulation composite functions through a "one-step" coaxial wet spinning process. The preparation process is simple and easy to industrialize. The fiber can effectively avoid the leakage problem of phase change materials. At the same time, the fiber has excellent conductive properties and a long service life, and is suitable for application in the fields of smart wearables and biomedical materials.

[0007] The idea of ​​the present invention is to provide a core-sheath type elastic strain sensing temperature regulating composite functional intelligent fiber, which includes a core layer and a sheath layer structure, wherein a conductive filler is added to the core layer to give the fiber high conductivity, and a phase change filler is also added to the core layer, so that the fiber has a temperature regulating function and can effectively regulate the body temperature; in addition, an elastomer is creatively added to the core layer material, and the elastomer can evenly disperse the phase change material while ensuring the dispersion of the conductive material, so that the fiber can exhibit excellent and durable conductive properties.

[0008] Specifically, the elastomer can act as a binder to tightly connect and fix the conductive filler and the phase change filler. At the same time, the elastomer can prevent the leakage of the phase change material on the one hand, and evenly disperse the conductive fibers on the other hand, thereby achieving the purpose of giving the fibers conductive properties. Finally, the elastomer material can also be adapted to the "one-step" coaxial wet spinning process, thereby reducing the gap in the core layer of the smart fiber, thereby giving the fiber good strain sensing properties.

[0009] The core-sheath elastic strain sensing and temperature regulation composite functional intelligent fiber of the present invention can be used as a flexible wearable strain sensor, and has excellent performance in various aspects such as conductive temperature regulation function, strain sensitivity, cycle stability and wearing comfort, and has broad application prospects in human thermal management and health monitoring.

[0010] To achieve the above-mentioned object, the present invention provides a core-sheath type elastic strain sensing temperature regulating composite functional intelligent fiber, the intelligent fiber core layer and sheath layer structure, wherein the core layer is a conductive temperature regulating core layer, and the sheath layer is an elastomeric sheath layer;

[0011] The conductive temperature-adjusting core layer at least comprises a core layer of conductive filler and phase-change filler;

[0012] In some embodiments, the conductive filler accounts for 1% to 5% of the core layer mass, preferably 2% to 4%;

[0013] It should be noted that the core layer here refers to the core layer in the finished product of the core-sheath type elastic strain sensing temperature regulating composite functional intelligent fiber, and does not refer to the spinning solution that forms the core layer, or the weight of the raw materials. There is still a solvent in the spinning solution, but the solvent will be removed during the fiber forming process, and the fiber will be solidified and formed. The core layer related to the smart fiber in the application document of this invention refers to the core layer of the fiber in the finished product.

[0014] The conductive filler is a carbon material or a metal material;

[0015] The carbon material is one or more of carbon nanotubes, graphene, and graphite; the metal material is one or more of liquid metal, metal powder, and metal wire;

[0016] The preferred conductive filler is a carbon material, and the more preferred carbon material is a multi-walled carbon nanotube;

[0017] Furthermore, the multi-walled carbon nanotubes have a diameter of 20 nm to 40 nm and a length of 10 μm to 20 μm.

[0018] The present invention finds that when the mass percentage of the conductive filler is lower than 1%, it is easy to fail to form a conductive network, showing no conductivity or poor conductivity (large resistance, obvious fiber heating), but it is also found that when the amount of the conductive filler is higher than 5%, the viscosity of the spinning solution will be greatly affected, and the viscosity of the spinning solution is not conducive to spinning; and because the conductive filler is powdery and small in size, excessive conductive filler is prone to agglomeration during the mixing process, resulting in an adverse effect on dispersion. Although the use of conductive fillers is increased, the purpose of increasing the conductivity is not achieved, and the conductivity may even be reduced. Through continuous adjustment, the present invention finds that when the mass percentage of the conductive filler used in this scheme is in the range of 2% to 4%, the fiber has high conductivity and good spinnability.

[0019] In some embodiments, the phase change filler accounts for 60% to 65% of the mass of the core layer;

[0020] The phase change filler is a fatty alcohol, a fatty hydrocarbon, a fatty acid, or polyethylene glycol, and the preferred phase change filler is a fatty hydrocarbon;

[0021] Furthermore, the phase change temperature of the phase change filler is 20°C to 40°C;

[0022] Furthermore, the phase change filler accounts for 60% to 65% of the mass of the core layer;

[0023] When the mass percentage of phase change filler is less than 60%, the temperature adjustment effect is not obvious, and when it is more than 65%, the conductivity of the fiber is affected.

[0024] The conductive temperature regulating core layer may also include an elastomer;

[0025] Furthermore, the elastomer accounts for 35%-60% of the mass of the core layer;

[0026] The present invention finds that in the conductive temperature regulating core layer, if only phase change material and conductive filler are included, the finally prepared smart fiber is difficult to ensure conductive performance or the conductive performance is unstable, that is, the filament fiber will partially not have conductive performance or the resistivity is too high; it is also found that during long-term use, leakage of phase change material is difficult to avoid; by creatively adding elastomers to the core layer, the conductive filler and the phase change filler are tightly connected, the core layer elastomer is consistent with the sheath layer elastomer, the compatibility of the core layer and the sheath layer is improved, and the strain sensing performance of the fiber is improved; when no elastomer is added to the core layer, a hollow structure may appear in the core layer, and the fiber core layer is prone to leakage. Although the fiber is conductive, its conductivity is unstable or non-conductive after deformation; when the elastomer accounts for 35%-40% in the core layer, the fiber core layer is tightly connected, no hollow structure will appear, the fiber is still conductive after multiple deformations, and the fiber core layer does not leak.

[0027] The elastomer material is a thermoplastic elastomer material;

[0028] Further, the elastomeric material is one of styrene-butadiene-styrene block copolymer (SBS), hydrogenated styrene-butadiene-styrene block copolymer (SEBS), styrene-isoprene-styrene block copolymer (SIS), hydrogenated styrene-isoprene-styrene block copolymer (SEPS), and polyurethane (PU), and the preferred elastomeric material is SBS;

[0029] Thermoplastic elastomer SBS has excellent tensile strength, good low temperature performance, excellent electrical properties, good processing performance and other characteristics.

[0030] In some embodiments, the sheath layer of the smart fiber is a thermoplastic elastomer material;

[0031] The thermoplastic elastomer material is one of styrene-butadiene-styrene block copolymer (SBS), hydrogenated styrene-butadiene-styrene block copolymer (SEBS), styrene-isoprene-styrene block copolymer (SIS), hydrogenated styrene-isoprene-styrene block copolymer (SEPS), and polyurethane (PU);

[0032] A preferred elastomeric material is styrene-butadiene-styrene block copolymer (SBS).

[0033] The SBS sheath exhibits excellent mechanical elasticity, giving the fiber strain sensor high stability and durability, while ensuring that the core layer filler does not leak, the fiber sensor has good safety, and the SBS sheath surface is smooth and fits human skin, which improves the wearing comfort of the fiber sensor; however, the present invention is not limited to SBS, and any elastomer with good mechanical properties after spinning is feasible.

[0034] On the other hand, the present disclosure also provides a method for preparing a core-sheath type elastic strain sensing temperature regulating composite functional smart fiber, wherein the smart fiber is prepared by a coaxial wet spinning process;

[0035] Furthermore, the core-sheath type elastic strain sensing temperature regulating composite functional intelligent fiber is prepared by extrusion coagulation molding through a coaxial spinning structure device;

[0036] The coaxial spinning structure used in the present invention is connected to at least two groups of spinning containers to spray and extrude the core layer and sheath layer spinning raw materials.

[0037] Furthermore, the elastic sheath layer spinning solution and the conductive temperature-regulating core layer spinning solution are respectively placed in a spinning container and transported to the coaxial spinneret by extrusion;

[0038] Furthermore, the extrusion ratio of the elastomer sheath layer spinning solution to the conductive temperature-regulating core layer spinning solution is 0.5 to 3:1, preferably 1 to 2:1;

[0039] When the extrusion rate ratio of the sheath layer to the core layer spinning solution is lower than 0.5:1, the fiber is not easy to form and there is a risk of core layer leakage. When the extrusion rate of the sheath layer to the core layer is higher than 3:1, the fiber core layer coating amount is low and the fiber's conductive temperature regulating performance decreases. When the extrusion rate ratio of the sheath layer to the core layer is between 1 and 2:1, the fiber is easy to form and can exhibit excellent conductive temperature regulating performance, and the fiber's durability is even better.

[0040] Furthermore, the nascent fibers extruded from the coaxial spinneret holes enter a coagulation bath to be coagulated and formed;

[0041] The coagulation bath is composed of ethanol and / or water, and the preferred coagulation bath is ethanol;

[0042] Furthermore, the solidified fibers are stretched and wound to obtain core-sheath type elastic strain sensing temperature regulating composite functional intelligent fibers.

[0043] In some embodiments, the method for preparing the core-sheath type elastic strain sensing temperature regulating composite functional intelligent fiber disclosed in the present invention also includes the preparation of a spinning solution.

[0044] Furthermore, the operation of the conductive temperature-regulating core layer spinning solution is to dissolve the conductive filler, the phase-change filler and the elastomer in a solvent, and stir to obtain the conductive temperature-regulating core layer spinning solution;

[0045] In order to ensure the uniform dispersion of the core layer spinning solution, mechanical stirring or auxiliary means such as ultrasound can be used to improve the uniform dispersion of the materials in the spinning solution.

[0046] The total amount of the conductive temperature regulating core layer filler accounts for 32% to 55% of the mass of the core layer spinning solution, preferably 40% to 45%;

[0047] It should be noted that the conductive temperature regulating core layer filler refers to the conductive filler, phase change filler and thermoplastic elastomer in the spinning solution forming the conductive temperature regulating core layer, and the above substances account for 32% to 55% of the spinning solution mass, preferably 40% to 45%.

[0048] Furthermore, the operation of the sheath spinning solution is to dissolve the elastomer in a certain amount of solvent, mechanically stir for a period of time, and then ultrasonically stand to obtain the sheath spinning solution;

[0049] Furthermore, the elastomer accounts for 10% to 50% of the mass of the sheath spinning solution, preferably 30% to 40%.

[0050] When the mass percentage of the elastomer is less than 10%, the fiber sheath cannot be solidified and formed; when the mass percentage of the elastomer is higher than 50%, the viscosity of the sheath spinning solution is too high and the fiber cannot be extruded and formed; when the mass percentage of the elastomer is between 30% and 40%, the fiber is easy to form and solidifies faster;

[0051] Further, the solvent is toluene, dichloromethane, chloroform, N,N-dimethylformamide, and the preferred solvent is dichloromethane;

[0052] The core-sheath elastic strain sensing temperature regulating composite functional intelligent fiber has excellent electrical conductivity (470S·m -1 ), strain sensitivity, temperature regulation performance (5℃~10℃), good flexibility (3MPa~11MPa, 0.9~1.25×10 4 %) and cyclic stability; the phase transition temperature of the core-sheath type elastic strain sensing temperature regulating composite functional intelligent fiber is 20°C to 40°C.

[0053] Beneficial effects of the present invention:

[0054] (1) The present invention successfully prepares an intelligent fiber with a core-sheath structure through a "one-step" wet spinning process. The manufacturing process is simple and easy to industrialize. The conductive filler and the phase change filler are well coated in the sheath elastomer, which can not only well protect the core filler from leakage, but also play an insulating effect on the sheath. Therefore, the fiber can be directly used as a strain sensor in the human body.

[0055] (2) The smart fiber produced by the present invention has good electrical conductivity, strain sensitivity, temperature regulation, elasticity, cyclic stability and strain sensitivity. It can monitor various deformation signals in real time through resistance changes. When the external temperature suddenly changes, it can buffer the impact of temperature changes on human physiological activities and provide a comfortable wearing experience for the human body.

[0056] (3) The smart fiber obtained by the present invention has excellent electrical conductivity (470S·m -1 ), temperature regulation performance (5℃~10℃), good flexibility (3MPa~11MPa, 0.9~1.25×10 4 %) and cycle stability (>100 cycles); the fiber is easy to be woven into textiles or embedded in clothing, and has the potential for large-scale production. In summary, the core-sheath type elastic strain sensing temperature regulation composite functional intelligent fiber has a wide range of applications and good market prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] The present invention will be further described in detail below in conjunction with the accompanying drawings and preferred embodiments, but those skilled in the art will appreciate that these drawings are only drawn for the purpose of explaining the preferred embodiments and therefore should not be taken as limiting the scope of the present disclosure.

[0058] Figure 1 : Schematic diagram of coaxial wet spinning process;

[0059] Figure 2 : Morphology of smart fibers: (a) Example 1, (b) Example 2, (c) Example 3, (d) Example 4, (e) Comparative Example 1, (f) Comparative Example 2, (g) Comparative Example 3, (h) Comparative Example 4, (i) Comparative Example 5;

[0060] Figure 3 : Dimensional parameters of smart fibers, wherein (a) embodiment, (b) comparative example;

[0061] Figure 4 : Electrical conductivity of smart fibers;

[0062] Figure 5 : Strain sensing performance of wearable strain sensors based on smart fibers, including (a) fatigue durability of the smart fiber sensor under bending angle of 60°. (b) Photograph of the smart fiber sensor during bending;

[0063] Figure 6 : Strain sensing performance of wearable strain sensors based on smart fibers, including (a) fatigue durability of the smart fiber sensor at 100% strain; (d) stretching photos of the smart fiber sensor during the experiment;

[0064] Figure 7 : DSC curve of smart fiber;

[0065] Figure 8 : Temperature regulation performance of smart fiber: (a) Thermal imaging image of smart fiber, (b) Curve of temperature change of smart fiber over time;

[0066] Fig. 9 : Stress-strain curves of smart fibers;

[0067] Fig.10 : DSC heating and cooling curves of Example 1 when the number of cycles is 10, 30 and 50 times. DETAILED DESCRIPTION

[0068] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0069] The present invention discloses a method for preparing a core-sheath type elastic strain sensing temperature regulating composite functional intelligent fiber, wherein the method is prepared by a coaxial wet spinning process;

[0070] Specifically, the coaxial wet spinning process is shown in Figure 1 The core layer spinning solution and the sheath layer spinning solution are squeezed into the coaxial spinning nozzle through two basic mechanisms respectively, and coagulated and formed in a coagulation bath, and then drawn and wound to obtain core-sheath fibers.

[0071] Furthermore, the core-sheath type elastic strain sensing temperature regulating composite functional intelligent fiber is prepared by extrusion coagulation molding through a coaxial spinning structure device;

[0072] Furthermore, the coaxial spinning structure is connected to at least two groups of spinning containers;

[0073] By setting up two groups of spinning containers, the extrusion speeds of the two groups of spinning solutions can be controlled respectively, so that the spinning solutions in the two containers can be extruded independently using extrusion equipment to control the extrusion amount of the two components, thereby ensuring the successful preparation of the fiber. In addition, the extrusion amount can also control the thickness of the core layer and the sheath layer to prevent leakage of the core layer.

[0074] Of course, the extrusion amounts set in the present invention are set according to the performance of the sheath layer and the core layer. Different core layer materials and different sheath layer materials, due to the differences in compatibility and coagulation between the core layer materials and the sheath layer materials, not all theoretical materials can form fibers, and not all materials prepared by the equipment of the present invention can prevent leakage of the core layer.

[0075] Furthermore, the elastic sheath layer raw material and the conductive temperature-regulating core layer raw material are transported to the coaxial spinneret hole by extrusion;

[0076] Furthermore, the extrusion volume ratio of the elastomeric sheath layer spinning solution and the conductive temperature regulating core layer spinning solution is 0.5 to 3:1; preferably 1 to 2:1, and the extrusion volume ratio of the elastomeric sheath layer spinning solution and the conductive temperature regulating core layer spinning solution can specifically be 0.7:1, 0.9:1, 1:1, 1.5:1, 2.5:1.

[0077] One of the keys of the present invention is to adjust the relationship between the spinning solution and the core layer filler. More importantly, the core-sheath type elastic strain sensing temperature regulating composite functional intelligent fiber is prepared by adjusting the extrusion amount. Through the selection of the core layer and the sheath layer, and the control of the extrusion amount in the preparation process, the mechanical properties (including flexibility) of the fiber, as well as the durability and leakage defects of the core layer are significantly improved.

[0078] The nascent fibers extruded from the coaxial spinneret holes enter into a coagulation bath to be coagulated and formed;

[0079] The coagulation bath is ethanol and / or water, and the preferred coagulation bath is ethanol;

[0080] Furthermore, the solidified fibers are stretched and wound to obtain core-sheath type elastic strain sensing temperature regulating composite functional intelligent fibers.

[0081] Furthermore, the operation of preparing the conductive temperature-adjusting core layer spinning solution may be to blend the solvent with the conductive filler, the phase change filler and the elastomer, and then perform ultrasonic treatment after magnetic stirring for a period of time;

[0082] Furthermore, the conductive temperature-regulating core layer filler accounts for 35% to 45% of the mass of the core layer spinning solution, preferably 38% to 42%.

[0083] When preparing the sheath spinning solution, the elastomer is dissolved in a solvent, and the elastomer accounts for 10% to 50% of the mass of the sheath spinning solution, preferably 30% to 40%.

[0084] The preparation of fibers and the properties of fibers are closely related to the raw materials. In the preparation of the spinning solution, the fiber with the properties of the present invention is obtained by adjusting the ratio of the raw materials.

[0085] This study first designed Figure 1 The invention discloses a coaxial wet spinning process device, which includes four parts: forming, coagulation, drawing and collection. Firstly, the spinning container containing the spinning solution is installed on the propulsion pump and connected to the coaxial spinneret through a polytetrafluoroethylene tube. The parameters are adjusted on the propulsion pump to extrude the fiber from the coaxial spinneret into the coagulation bath. The fiber is drawn and collected by a stepper motor and a rotating drum. By adjusting the process parameters and the type and ratio of the core layer filler, smart fibers with different electrical and temperature regulation properties are obtained.

[0086] Example 1

[0087] (1) Preparation of sheath spinning solution: 15 parts of SBS (model: YH-791H, purchased from Baling Petrochemical Company) and 30 parts of dichloromethane were weighed and mixed. The mixture was stirred at 180 r / min in an electric stirrer. -1The spinning solution of the sheath layer was prepared by mechanically stirring for 5 h at a speed of 1000 r·min to completely dissolve the carbon nanotubes, and then ultrasonically defoaming for 30 min was performed to obtain the sheath spinning solution. The core spinning solution was prepared by weighing 0.3 parts of multi-walled carbon nanotube powder (purity>99%, purchased from Pioneer Nano Co., Ltd.) and 15 parts of dichloromethane, mixing them into a 50 mL conical flask, and ultrasonically dispersing them in an ultrasonic machine for 1 h. Then, 4 parts of SBS and 7 parts of octadecane (purity>99%, purchased from Shanghai Huihuo Entropy New Energy Co., Ltd.) were added, and then the mixture was stirred at 300 r·min. -1 The mixture was magnetically stirred at a speed of 4 h and finally ultrasonically defoamed for 30 min to obtain the core spinning solution.

[0088] (2) The sheath layer and core layer spinning solutions in step (1) are respectively loaded into a sheath layer container and a core layer container, and the extrusion rate is set. The spun fibers extruded from the coaxial spinneret are put into a coagulation bath for coagulation and forming, and then drawn, wound, and dried to obtain a fiber.

[0089]

[0090] In the above test results, the conductivity and enthalpy values ​​can be obtained through equipment testing. The strain sensing standard refers to the elongation of the fiber when the fiber loses its conductive properties when it is in a stretched state.

[0091] In order to determine the propulsion speed of the core layer and the sheath layer, the above five parameters were used for the test. When the propulsion speed of the sheath layer was lower than 150 μL·min -1 When the core layer is used for uniaxial spinning, the strain sensing ability of the smart fiber is poor; when the obtained fiber is stretched to 25.1%, the fiber part breaks, so we use coaxial spinning to introduce the elastomer sheath layer. Since the elastomers in the core layer and the sheath layer are the same, the two are closely connected, which reduces the gap between the core layer of the smart fiber and improves the tensile strength of the fiber. With the increase of the sheath layer flow rate, the sheath layer of the fiber gradually becomes thicker, so its tensile strength is enhanced; when the sheath layer flow rate reaches 150μL·min -1 When the smart fiber was stretched to 218.9%, the fiber did not break, but the conductivity was lost, mainly because the conductive network of the core layer was disconnected; however, when the sheath flow rate reached 200 μL·min -1 When the fiber sheath layer advances at a speed lower than 50 μL·min -1 When the sheath propulsion speed is higher than 150 μL·min -1 When the core layer is coated with relatively less, the enthalpy of the fiber is reduced, which in turn affects its temperature regulation performance. Finally, the core layer advancement speed is set to 100 μL·min -1 , the sheath propulsion speed is 150 μL·min -1, and obtain the core-sheath fiber of Example 1 for other tests.

[0092] Example 2

[0093] The operation was the same as that of Example 1, except that the phase change filler was eicosane (purity > 99%, purchased from Shanghai MacLean Biochemical Technology Co., Ltd.), and the sheath propulsion speed was determined to be 150 μL·min -1 , the core layer advancement speed is 100μL·min -1 .

[0094] According to DSC test, the enthalpy value of the core-sheath elastic strain sensing temperature regulation composite functional intelligent fiber is 31.23 J·part -1 The phase transition temperature is 22.9℃; the conductivity is 210S·m -1 .

[0095] At the same time, this group of examples also experiments on the phase change core material components to verify the influence of different core layers on fiber properties. The specific process parts are shown in the following table:

[0096]

[0097]

[0098] In order to determine the types and contents of conductive fillers, phase change fillers and elastomers, the above 12 formulations were used for experiments. When the conductive filler accounts for 3%, the conductivity of the fiber is the highest; when the conductive filler accounts for 5%, the increase in the conductive filler causes the viscosity of the core layer spinning solution to increase, which easily causes the core layer structure to be uneven or the core layer to be disconnected during the spinning process, so the conductivity of the fiber decreases to a certain extent; when there is no elastomer in the fiber core layer, although the fiber has a certain conductive temperature regulating function, the phase change filler in the core layer will be disconnected after stretching, and it cannot be used as a strain sensor; and when there is no elastomer in the core layer, the core layer and the shell layer of the smart fiber cannot be tightly connected, and the external stress on the fiber will cause the phase change material to be squeezed out of the fiber. When the fiber works at a higher temperature, the phase change material will also melt and flow out, shortening the service life of the smart fiber.

[0099] When the elastomer content in the fiber core layer is too high, such as 60%, the conductivity and enthalpy of the fiber will decrease. This is because the elastomer is an insulating material, and a high content will affect the conductivity of the fiber. When the elastomer content in the fiber core layer is 30%-40%, the fiber has a higher conductivity and enthalpy, and it is still conductive within the range of 200% tensile strain. Multi-walled carbon nanotubes have higher conductivity than liquid metal and graphite, and nano-scale materials are easier to disperse in elastic bodies. When the phase change filler is tetradecanol and paraffin, it will hinder the dispersion of carbon nanotubes, resulting in too low conductivity. When the phase change filler is aliphatic hydrocarbons, the dispersion effect of carbon tubes is better.

[0100] Example 3

[0101] The same as Example 1, except that the multi-walled carbon nanotubes are 0.1 parts.

[0102] According to DSC test, the enthalpy value of the core-sheath elastic strain sensing temperature regulation composite functional intelligent fiber is 39.52 J·part -1 The phase transition temperature is 25.1℃; the conductivity is 100S·m -1 .

[0103] Example 4

[0104] Same as Example 1, except that the fibers were not drawn.

[0105] According to DSC test, the enthalpy value of the core-sheath elastic strain sensing temperature regulation composite functional intelligent fiber is 44.60 J·part -1 The phase transition temperature is 27.1℃; the conductivity is 60S·m -1 .

[0106] Comparative Example 1

[0107] The same as Example 3, except that the core layer solution is H2O, the drying temperature is 50°C, and the drying time is 12h. According to DSC test, the core-sheath elastic strain sensing thermostatic composite functional intelligent fiber has no phase transition temperature and enthalpy value; and according to the digital multimeter test, it has no conductivity.

[0108] Comparative Example 2

[0109] The same as comparative example 1, except that: the core layer conductive filler is an aqueous carbon tube slurry with a solid content of 6.5wt% (purchased from Shenzhen Hongdachang Evolution Technology Co., Ltd.), and there is no phase change material.

[0110] According to DSC test, the core-sheath elastic strain sensing temperature regulation composite functional intelligent fiber has no phase change temperature and enthalpy value; the conductivity is 400S·m -1 .

[0111] Comparative Example 3

[0112] The same as comparative example 1, except that: the core layer solution is phase change filler polyethylene glycol (purity> 99%, purchased from Sinopharm Chemical Reagent Co., Ltd.), polyethylene glycol = 4 parts, dichloromethane = 4 parts, and no conductive filler.

[0113] According to DSC test, the enthalpy value of the core-sheath elastic strain sensing temperature regulation composite functional intelligent fiber is 159.6 J·part -1 The phase change temperature is 37.8℃; tested by a digital multimeter, it has no conductivity.

[0114] Comparative Example 4

[0115] The same as comparative example 1, except that the mass ratio of polyethylene glycol in the core layer solution to the aqueous carbon tube slurry is 7:3.

[0116] According to DSC test, the enthalpy value of the core-sheath elastic strain sensing temperature regulation composite functional intelligent fiber is 35.78 J·part -1 , the phase change temperature is 38.0℃; the conductivity is 80S·m -1 .

[0117] Comparative Example 5

[0118] Same as Example 1, except that the phase change filler is paraffin (melting point 35°C, manufacturer: Lingfeng Plastics Co., Ltd.)

[0119] According to DSC test, the enthalpy value of the core-sheath elastic strain sensing temperature regulation composite functional intelligent fiber is 26.61 J·part -1 The phase transition temperature is 25.3℃; the conductivity is 61S·m -1 .

[0120] Detection

[0121] Fiber morphology test: The surface morphology of the fibers was observed using a stereo microscope (SZ61, OLYMPUS, Japan).

[0122] Conductivity and resistance stability test: A digital multimeter (UT52, MULTIMETER, China) was used to measure the resistance of the fiber. The obtained fiber was bent by fitting it to human skin or stretched by clamping it with tweezers. The relative resistance change before and after bending and stretching of the fiber was measured by a digital multimeter to study the durability and stability of the obtained fiber as a strain sensor.

[0123] Tensile strength test: An Instron electronic universal material testing machine (68TM-10, SDL, USA) was used at 200 mm min -1The fiber sample was stretched at a tensile rate of 1 kN and a loading force of 1 kN to measure the tensile properties of the fiber.

[0124] Phase transition temperature and phase transition enthalpy measurement: The phase transition of the fiber in a nitrogen atmosphere was analyzed using a differential scanning calorimeter (DSC200F3, NETZSCH, Germany). The test temperature range was -20 °C to 80 °C, and the heating and cooling rates were both 10 °C min -1 .

[0125] Thermal imaging photos: Using a thermal imaging camera (FLIR E5424°, FLIR Systems Take a 1.5cm×1.5cm thermal conductive cloth and stick it with double-sided tape, then cut several 1.5cm coaxial fibers and stick them tightly on the thermal conductive cloth, and place them neatly on the heating table. The test temperature is 20℃~60℃.

[0126] Table 1 Test results

[0127]

[0128] Figure 2 The morphology of the smart fiber is shown. It can be seen from the figure that the undrawn fiber Example 4 is uneven in thickness and has a large fiber diameter. For the fibers of Examples 1-3, after drawing, the fibers are thinner, the fiber interface is cashew-shaped, and the mechanical properties are more excellent. At the same time, it can be seen that when the core layer filler changes, the thickness of the fiber also changes. For Comparative Examples 1-4, i.e., ef, it can also be seen that when the aqueous carbon nanotube slurry is added to the core layer, the fiber is generally in a round state and is easily hollow. Not only will the fiber core layer leak, but the mechanical properties are also poor.

[0129] Figure 3 are the morphological parameters of the smart fiber. There is no significant difference in the morphological parameters of the fiber under the drawing condition, while the morphological difference of the undrawn fiber is relatively large. In the undrawn state, such as Example 4, the tube diameter and sheath thickness are significantly increased.

[0130] Figure 4 The conductivity of the smart fiber is shown. The conductivity of the fiber in Example 1 can reach 470 S·m -1 The conductivity of the undrawn fiber in Example 4 is only 60 S·m -1 The electrical conductivity is also related to the content of the conductive filler and the type of the phase change filler. The electrical conductivity of the other embodiments and comparative examples is reduced.

[0131] Figure 5 , 6 Demonstrated the strain sensing performance of smart fibers as wearable sensors, Figure 5 The image of smart fiber changing with finger joints ( Figure 5 b) and resistance change rate ( Figure 5 a), the resistance change rate shows that the smart fiber has good cyclic stability and can detect changes in weak signals from the human body;

[0132] Figure 6 This is the 100% cycle test diagram of the smart fiber stretching in Example 1 ( Figure 6 b) and resistance change rate ( Figure 6 a), the resistance change rate shows that the smart fiber has the advantages of good tensile resistance, excellent cycle stability and long service life, and can be used as a wearable strain sensor for the human body.

[0133] Figure 7 The DSC curve of the obtained smart fiber shows that the fiber has phase transition behavior while being highly conductive. The phase transition temperature range is 20℃~40℃, which is consistent with the comfortable temperature of the human body.

[0134] Figure 8 The thermal imaging test diagram of the smart fiber and the temperature change curve over time directly show the temperature regulation performance of the obtained smart fiber. As the temperature of the hot plate increases, the temperature of the obtained smart fiber (Examples 2 and 3) is 7°C to 8°C lower than that of the pure sample fiber (Comparative Example 1). When the ambient temperature suddenly changes, the smart fiber can keep the human body surface temperature within a comfortable range.

[0135] Fig. 9 The flexibility of the smart fiber in the embodiment of the present invention is shown. It can be seen that the stress of the fiber prepared in Embodiments 1-4 is 3MPa-11MPa, and the strain is 0.9-1.25×10 4 %. Fig. 9 is the stress-strain curve of the smart fiber, which shows that Example 1 has excellent tensile properties, with a breaking strength of up to 10.87 MPa and an elongation at break of up to 12000%; while the breaking strength of the unstretched Example 4 is significantly reduced to only 3.3 MPa; therefore, the fiber obtained in this study has good elasticity, is easy to weave, and has a long service life.

[0136] In order to study the cyclic stability of the smart fiber, Example 1 was subjected to heating / cooling cycles in a constant temperature box from 20°C to 65°C, and the cyclic stability performance of Example 1 was studied by DSC test after 10, 30 and 50 cycles.

[0137] from Fig.10 It can be seen that the phase transition temperature of Example 1 remains almost unchanged during the heating and cooling process after 50 cycles. The initial melting enthalpy is 58.17 J·part -1 After 50 cycles, it becomes 56.72 J·part -1 , which is only about 2.5% lower than the initial value. The crystallization enthalpy is 56.15 J·part -1Slight change to 55.09 J·part -1 These results indicate that the smart fibers have good thermal cycling performance, which confirms their potential in personal thermal management applications.

[0138] From the test of the present invention, the core-sheath type elastic strain sensing and temperature regulating composite functional intelligent fiber prepared by the present invention has excellent performance, good cycle stability and long service life, and can be used as a wearable strain sensor in many aspects such as human health monitoring and thermal management.

Claims

1. A core-sheath type elastic strain sensing temperature regulating composite functional intelligent fiber, characterized in that: The fiber includes a conductive temperature-regulating core layer and an elastomeric sheath layer; The core-sheath type elastic strain sensing temperature regulating composite functional intelligent fiber is prepared by extrusion coagulation molding through a coaxial spinning structure device; The conductive temperature-adjusting core layer at least comprises a core layer of conductive filler and phase-change filler; The conductive filler accounts for 1% to 5% of the core layer mass, preferably 2% to 4%; The phase change filler accounts for 60% to 65% of the core layer mass; Alternatively, the conductive temperature-regulating core layer may further include a thermoplastic elastomer, and the thermoplastic elastomer accounts for 35%-60% of the mass of the core layer.

2. The core-sheath type elastic strain sensing temperature regulating composite functional intelligent fiber according to claim 1, characterized in that: The conductive filler is a carbon material or a metal material; The carbon material is one or more of carbon nanotubes, graphene, and graphite; The metal material is one or more of liquid metal, metal powder and metal wire.

3. The core-sheath type elastic strain sensing temperature regulating composite functional intelligent fiber according to claim 1, characterized in that: The phase change filler is one or more of fatty alcohol, fatty hydrocarbon, fatty acid, and polyethylene glycol; The phase change temperature of the phase change filler is 20°C to 40°C; The elastomeric material is a thermoplastic elastomeric material.

4. The core-sheath type elastic strain sensing temperature regulating composite functional intelligent fiber according to claim 1, characterized in that: The sheath material is a thermoplastic elastomer material.

5. The core-sheath type elastic strain sensing temperature regulating composite functional intelligent fiber according to any one of claims 1 to 4 is characterized in that: The thermoplastic elastomer material is one of styrene-butadiene-styrene block copolymer (SBS), hydrogenated styrene-butadiene-styrene block copolymer (SEBS), styrene-isoprene-styrene block copolymer (SIS), hydrogenated styrene-isoprene-styrene block copolymer (SEPS), and polyurethane (PU).

6. The core-sheath type elastic strain sensing temperature regulating composite functional intelligent fiber according to claim 5, characterized in that: The conductive filler, phase change filler and thermoplastic elastomer in the spinning solution for forming the conductive temperature regulating core layer account for 32% to 55% of the spinning solution mass, preferably 40% to 45%.

7. The core-sheath type elastic strain sensing temperature regulating composite functional intelligent fiber according to claim 1, characterized in that: The thermoplastic elastomer in the spinning solution for forming the elastomer sheath layer accounts for 10% to 50% of the mass of the spinning solution, preferably 30% to 40%.

8. The core-sheath type elastic strain sensing temperature regulating composite functional intelligent fiber according to any one of claims 6 to 7, characterized in that: The solvent in the spinning solution is one or more of toluene, dichloromethane, chloroform and N,N-dimethylformamide.

9. A method for preparing the core-sheath type elastic strain sensing temperature regulating composite functional intelligent fiber according to any one of claims 1 to 8, wherein the fiber is prepared by a coaxial wet spinning process; The core-sheath type elastic strain sensing temperature regulating composite functional intelligent fiber is prepared by extrusion coagulation molding through a coaxial spinning structure device; The coaxial spinning structure is connected to at least two groups of spinning containers; The container is used to load the elastomeric sheath layer spinning solution and the conductive temperature regulating core layer spinning solution; The elastic sheath layer spinning solution and the conductive temperature-regulating core layer spinning solution are transported to the coaxial spinneret hole by extrusion.

10. The method for preparing a core-sheath type elastic strain sensing temperature regulating composite functional intelligent fiber according to claim 9, characterized in that: The extrusion ratio of the elastic sheath layer spinning solution to the conductive temperature regulating core layer spinning solution is 0.5 to 3:1, preferably 1 to 2:1.

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