Preparation method and application of packaged electric heating phase change fiber with axial orientation conductive network

Abstract

The invention discloses a preparation method of a packaged electric heating phase change fiber with an axial orientation conductive network, which comprises the following steps: dissolving carbon black in water, dispersing, and adding methyl cellulose to prepare a carbon black / methyl cellulose spinning solution; extruding into a cold source through a spinning needle on an injection pump, enabling the spinning solution to enter the cold source to be gradually frozen, and collecting frozen fibers to prepare carbon black / methyl cellulose aerogel fibers with conductive network structures in different orientations; immersing the carbon black / methyl cellulose aerogel fiber into a molten phase change material, and cooling after vacuum impregnation to obtain an electric heating phase change fiber; and coating the electrothermal phase change fiber with a polymer solution through a dip-coating method, and volatilizing the solvent to prepare and complete shell packaging, thereby obtaining the packaged electrothermal phase change fiber. The packaged electrothermal phase change fiber prepared by the method has high conductivity, high energy storage density, high electrothermal conversion efficiency, excellent flexibility and stability, and excellent thermal management capability.

Description

Technical Field

[0001] The present invention relates to the technical field of conductive fiber materials composite with phase change materials, and particularly relates to a preparation method and application of encapsulated electrothermal phase change fibers with an axially oriented conductive network. Background Art

[0002] In recent years, many advanced personal thermal management textiles have emerged and received extensive attention and research in the industrial and academic fields. These intelligent thermal management textiles maintain human thermal comfort by regulating heat radiation, heat conduction, humidity, etc. For example, the warm fabric Omni-heat developed by Columbia has a high infrared reflectivity material on the inner layer, which can improve the warmth retention effect by suppressing human heat radiation; the polyester hollow fiber (Thermolite) developed by DuPont in the United States can capture air and limit heat conduction and heat convection, thus enhancing the heat insulation ability of clothing. In addition, there are also some personal thermal management textiles that utilize external input energy, such as through electrothermal and thermoelectric effects, to achieve active heating or cooling effects.

[0003] Among various personal thermal management textiles, textiles composite with phase change materials (PCMs) can store or release thermal energy through reversible phase change processes, mitigate the adverse effects of environmental temperature fluctuations on the human body, and possess stronger temperature regulation capabilities in environments with drastic environmental temperature changes. Benefits of phase change materials: Phase change materials are advanced functional materials that can absorb or release a large amount of latent heat through reversible melting or crystallization processes within a relatively narrow phase change temperature range. For example, some solid-liquid phase change materials can absorb or release approximately 200 - 300 J / g of latent heat during the phase change process. The phase change energy storage characteristics of phase change materials endow them with great application potential in the field of personal thermal management. As early as the 1970s, NASA had already applied phase change materials in the research and development of spacesuits and spacecraft to ensure that personnel and equipment were not damaged in the extreme temperature environments in space. The phase change materials commonly used in phase change textiles are solid-liquid phase change materials, such as organic phase change materials like paraffin, hydrated inorganic salts, and polyvinyl alcohol, whose phase change temperatures match the human thermal comfort temperature range, approximately between 15 °C and 35 °C, thus ensuring that the textiles can bring higher thermal comfort when worn by humans. Working mechanism of phase change fabrics: When the external environmental temperature rises, the phase change materials in the phase change textiles will undergo a phase change from solid to liquid and absorb heat. Since the heat is absorbed by the phase change materials and stored as phase change energy, the overall temperature of the textiles will not rise immediately. Therefore, this phase change energy storage mechanism can ensure that the textiles play a cooling role when the external temperature is high, alleviating the hot feeling on the body surface. When the external temperature drops, the phase change materials change from liquid to solid, and the phase change energy is converted into thermal energy and released to maintain the constant temperature of the textiles. Therefore, phase change textiles can input heat to the human body in cold environments to prevent hypothermia and frostbite.

[0004] Although phase change textiles possess excellent thermal management capabilities, relying solely on the phase change constant temperature mechanism is difficult to meet the human thermal management requirements for long service life, wide application range, and active thermal regulation of advanced textiles. There is an urgent need to develop electrothermal phase change textiles with phase change constant temperature, active heating, and energy storage functions. Preparation methods of electrothermal phase change fabrics: Since the commonly used phase change materials are electrically insulating, it is necessary to additionally add conductive fillers in the electrothermal phase change textiles to construct a conductive network in order to achieve electrothermal conversion. Commonly used conductive fillers include metal materials and their alloys (such as silver, gold, etc.); carbon-based conductive materials (such as graphene, carbon nanotubes, graphite foam, conductive carbon black, and biomass carbon, etc.); conductive polymers (such as polypyrrole, polyaniline, etc.); two-dimensional transition metal carbides / nitrides MXene (such as Ti 3 C 2 Tx). In the existing technology, electrothermal phase change fibers are generally obtained by blending conductive materials, phase change materials, and polymer materials and then spinning through techniques such as melt spinning and wet spinning, or are prepared by coating conductive materials on the surface of phase change textiles.

[0005] For example, the Chinese patent with the publication number CN 108587571 A prepares graphene aerogel fibers through wet spinning and chemical reduction, and then combines the graphene aerogel fibers with an organic phase change material by an immersion method, and coats the fibers with a hydrophobic coating to obtain graphene aerogel intelligent phase change fibers; in the Chinese patent with the publication number CN 113583634 A, a modified graphene aerogel composite masterbatch is blended with a fiber-forming polymer and then melt-spun to prepare graphene aerogel composite fibers, and then a phase change material is wrapped outside the fibers, and finally a hydrophobic coating is uniformly coated on the fiber surface to obtain graphene intelligent temperature-sensing phase change fibers; in the Chinese patent with the publication number CN 115045043 B, a base layer thermoplastic elastomer nanofiber membrane is first prepared by electrospinning technology; then a phase change layer hybrid fiber membrane is prepared on the base layer by adding a phase change material to the spinning solution; finally, a thermoplastic elastomer nanofiber membrane is electrospun on the phase change layer, and a conductive material dispersion is coated on the obtained thin film to obtain a conductive layer.

[0006] Although the above patents have successfully prepared electrothermal phase change fibers, there are still some deficiencies. First, since these spinning technologies cannot control the dispersion and orientation degree of conductive fillers in the fibers and lack the design of the conductive network structure, an excessive amount of conductive fillers often needs to be added to ensure effective electrothermal conversion of textiles. However, too many conductive fillers will reduce the loading amount of the phase change material, resulting in a decrease in the energy storage density; while reducing the content of conductive fillers will lead to insufficient conductivity and electrothermal performance and a decrease in the electrothermal conversion efficiency. In addition, electrothermal phase change fibers also face the problems of leakage of liquid phase change materials and insufficient flexibility. How to design and manufacture electrothermal phase change textiles with excellent heat storage and electrothermal performance and with the phase change material not easily leaking is still a challenge. Summary of the Invention

[0007] The purpose of the present invention is to provide a preparation method of encapsulated electrothermal phase change fibers with an axially oriented conductive network. The prepared encapsulated electrothermal phase change fibers have both high conductivity, high energy storage density, high electrothermal conversion efficiency, excellent flexibility and stability, and excellent heat management capabilities, and the preparation method is simple, low-cost, and has a short production cycle.

[0008] The technical solution adopted by the present invention to achieve the above purpose is as follows: A preparation method of encapsulated electrothermal phase change fibers with an axially oriented conductive network, the method comprising the following steps: 1) First, dissolve carbon black in water, disperse it, and then add methyl cellulose to prepare a carbon black / methyl cellulose spinning solution; 2) The carbon black / methyl cellulose spinning solution obtained in step 1) is extruded into a cold source through a spinning needle on an injection pump. The spinning solution enters the cold source and is gradually frozen. The frozen fibers are collected to prepare carbon black / methyl cellulose aerogel fibers with different oriented conductive network structures. 3) The carbon black / methyl cellulose aerogel fibers obtained in step 2) are immersed in a molten phase change material, taken out after vacuum impregnation, and placed at room temperature to cool to obtain electrothermal phase change fibers. 4) The electrothermal phase change fibers obtained in step 3) are coated with a polymer solution by dip coating, and the solvent is volatilized by heating to complete the shell encapsulation to obtain encapsulated electrothermal phase change fibers.

[0009] The technical concept of the present invention lies in that: as a super-light material with a three-dimensional interconnected porous network structure, aerogel can adsorb phase change materials through capillary force, and its extremely high porosity provides sufficient space for the loading of functional materials; in addition, by introducing an oriented conductive network structure into the aerogel, the conductivity can be enhanced under the condition of a low content of conductive fillers, realizing effective electrothermal conversion; by preparing aerogel fibers with an oriented conductive network structure, and then compounding the phase change material with the fibers, electrothermal phase change fibers are prepared; encapsulating the fibers can improve the stability of the fibers, and fixing the phase change material in the fiber core layer through encapsulation is expected to avoid the leakage of the phase change material in practical applications.

[0010] In the present invention, the structure of methyl cellulose contains methyl (–CH 3 ) groups, which makes it have good solubility and low hydrophilicity in water; the hydrophobic property of the methyl group helps carbon black particles disperse better in methyl cellulose. Therefore, this good dispersibility enables carbon black particles to form a conductive network more effectively through the fibers, thereby improving the conductivity. Compared with methyl cellulose, polymers containing polar groups such as carboxymethyl cellulose have stronger hydrophilicity due to the presence of intrinsically dissociable functional groups such as carboxyl (–COOH) in their structures. This kind of cellulose has better solubility in water, but its interaction with carbon black is stronger, resulting in more difficult uniform dispersion of carbon black particles, affecting the formation of the conductive network and leading to poor final conductivity.

[0011] In step 1), the mass ratio of the carbon black to methyl cellulose is 0.8 - 1.6:1.

[0012] In step 1), the mass ratio of the carbon black to methyl cellulose is 1 - 1.6:1, which can further improve the conductivity of the electrothermal phase change fibers.

[0013] In step 2), the cold source is a semiconductor ring cold source device, the temperature of the semiconductor ring cold source device is -10~-50 °C, and the extrusion speed of carbon black / methyl cellulose fiber is set to 1~4 ml / h.

[0014] Preferably, the temperature of the semiconductor ring cold source device is -10~-30 °C.

[0015] During the freeze spinning process, due to the temperature gradient between the cold source and the interior of the fiber, ice crystals will grow directionally along the temperature gradient, and solute molecules will precipitate during the solvent crystallization process. By controlling the cold source temperature, the precipitation rate of solute molecules can be changed to form different fiber morphologies. Therefore, by regulating the freezing temperature, the microstructure of carbon black / methyl cellulose aerogel fibers can be effectively controlled, thereby constructing aerogel fibers with different pore structures. Regulating the pore structure of the aerogel fibers will affect the conductivity of the fibers. This is because according to the percolation theory, without changing the content of the conductive filler, optimizing the conductive pathway can improve the conductivity of the material. Therefore, by increasing the degree of orientation of the conductive network of the aerogel fibers along the axial direction, the conductivity can be improved without changing the content of the conductive filler.

[0016] In step 2), the carbon black / methyl cellulose aerogel fiber has a three-dimensional porous network structure composed of macropores with a pore diameter of 20~170 μm, the porosity is 75~85%, the specific surface area is 10~30 m 2 / g, and the conductivity is 40~140 S / m.

[0017] The higher the porosity of the aerogel fiber, the more phase change material can be accommodated. Therefore, a higher porosity will increase the amount of phase change material that can be loaded in the aerogel. If the porosity is low, there will be less pore space in the aerogel, and the loading amount of the phase change material will naturally decrease. The phase change enthalpy is the heat absorbed or released by the phase change material during the phase change process (such as from solid to liquid). Since the high-porosity aerogel can accommodate more phase change material, the phase change enthalpy will also increase. A higher loading amount means more.

[0018] In step 3), the phase change material is selected from any one of polyethylene glycol, paraffin, polyol, erythritol or polyolefin.

[0019] Preferably, the phase change material is selected from polyethylene glycol or paraffin.

[0020] In step 4), the polymer solution for coating is selected from a polyurethane solution or a polytetramethylsiloxane solution. The polyurethane solution is a polyurethane / N,N-dimethylformamide solution with a concentration of 10 w / v%. The polytetramethylsiloxane solution is a solution in which polytetramethylsiloxane resin and a curing agent are mixed in a ratio of 10:1 and cured in an oven at 50 °C for 15 min.

[0021] In step 4), the electrothermal phase change fibers are immersed in the polymer solution for 30 s. After taking them out, a customized sieve plate with a pore size of 800 - 1000 μm is used to scrape off the excess solution. Then, the fibers are placed 5 cm above an 80 °C heater and heated for 10 min. The number of times of repeated impregnation and drying is 1 - 6 times.

[0022] In step 4), the content of the graphene / methylcellulose fiber network encapsulating the electrothermal phase change fibers is 10 - 25 wt%, the content of the phase change material is 55 - 85 wt%, and the rest is the polymer shell layer.

[0023] In step 4), the content of the graphene / methylcellulose fiber network encapsulating the electrothermal phase change fibers is 11 - 18 wt%, the content of the phase change material is 68 - 82 wt%, and the rest is the polymer shell layer.

[0024] Preferably, the content of the graphene / methylcellulose fiber network encapsulating the electrothermal phase change fibers is 16 - 18 wt%, the content of the phase change material is 77 - 79 wt%, and the rest is the polymer shell layer.

[0025] In step 4), the phase change enthalpy of the electrothermal phase change fibers prepared is 85 - 200 J / g.

[0026] The graphene / methylcellulose fiber network prepared by the present invention has a relatively high porosity, so the loading amount of the phase change material can be increased (a higher loading amount means that more phase change materials can undergo phase changes when the temperature changes, thereby absorbing or releasing more heat); the phase change enthalpy is the heat absorbed or released by the phase change material during the phase change process (such as from solid state to liquid state); since the high-porosity aerogel prepared by the present invention can accommodate more phase change materials, the phase change enthalpy will also increase.

[0027] The present invention also provides an application of the electrothermal phase change fibers encapsulated by the above preparation method in personal thermal management warm fabrics.

[0028] The encapsulated electrothermal phase change fiber endows the fabric with properties such as phase change constant temperature, electrothermal heating, and energy storage, enabling it to regulate the temperature of the microenvironment on the human body surface and mitigate the adverse effects on the human body caused by extreme environments, temperature fluctuations, etc. The encapsulated electrothermal phase change fiber of the present invention, using conventional or unconventional processing techniques, can not only be blended with natural fibers or chemical fibers, but also be directly woven onto commercial textiles to be processed into electrothermal phase change textiles, showing great application potential in fields such as daily clothing and special protective clothing. When the encapsulated electrothermal phase change fiber is used for personal thermal management, after applying electrical energy to it, its oriented conductive network converts the electrical energy into heat energy, and the heat energy then conducts to the phase change material filled between the conductive networks. The phase change material stores heat energy through solid-liquid phase change and releases heat energy through liquid-solid phase change when the ambient temperature decreases. Moreover, for the encapsulated electrothermal phase change fiber of the present invention, the phase change material is confined in the fiber core layer by the shell layer, is not easily leaked from the inside of the fiber, and has high stability. The encapsulated electrothermal phase change fiber of the present invention has rapid electrothermal responsiveness, can quickly complete the charging of the phase change material through electric heating, its relatively high phase change enthalpy enables it to maintain long-term thermal comfort on the body surface through phase change heat release, and its excellent mechanical stability and structural stability enable it to be applicable to various extreme environments. Therefore, the encapsulated electrothermal phase change fiber of the present invention is an ideal material for personal thermal management.

[0029] Compared with the prior art phase change, the advantages of the present invention include: (1) The encapsulated electrothermal phase change fiber provided by the present invention breaks through the limitation that it is difficult to balance the energy storage and electrothermal performance of electrothermal phase change fibers, and has advantages such as high electrical conductivity, high energy storage density, high electrothermal conversion efficiency, excellent flexibility and stability: it is composed of carbon black / methyl cellulose aerogel fiber containing an oriented conductive network, a phase change material, and an encapsulation shell layer; the carbon black / methyl cellulose aerogel fiber, as the matrix material of the encapsulated electrothermal phase change fiber, not only has a relatively high electrical conductivity, with an electrical conductivity of 40 - 140 S / m, but also has a relatively large porosity, with a porosity of 75 - 85%, providing a large space for the loading of the phase change material. At the same time, it also has a relatively large specific surface area, with a specific surface area of 10 - 30 m 2 / g. The three-dimensional porous network with a large specific surface area promotes the conversion and storage of energy; the encapsulation shell layer structure effectively prevents the leakage of the phase change material and also improves the mechanical properties and hydrophobic properties of the fiber.

[0030] (2) The preparation method of the encapsulated electrothermal phase change fiber provided by the present invention adopts electrospinning, vacuum impregnation and dip coating techniques. The preparation process is simple, environmentally friendly, has a short production cycle, and at the same time, the raw materials have a wide source and low cost, being suitable for large-scale production, laying a foundation for the multifunctionalization of electrothermal phase change fibers and expanding their applications in the field of personal thermal management.

[0031] (3) The encapsulated electrothermal phase change fiber provided by the present invention can be used for phase change energy storage, electrothermal conversion and storage. The fabric woven from this fiber has the advantages of fast response speed, high stability, strong adaptability, good flexibility, air permeability, moisture permeability, etc., and shows broad application prospects in personal thermal management and is worthy of being widely promoted and applied. Description of the Drawings

[0032] Figure 1 Scanning electron microscope photos of the radial cross-section and axial cross-section of the carbon black / methyl cellulose aerogel fiber obtained in Example 1; Figure 2 Scanning electron microscope photos of the radial cross-section of the electrothermal phase change fiber obtained in Example 1; Figure 3 Scanning electron microscope photos of the radial cross-section of the encapsulated electrothermal phase change fiber obtained in Example 1; Figure 4 Microscopic morphology electron micrographs of the radial cross-section and axial interface of the carbon black / methyl cellulose aerogel fiber obtained in Example 2; Figure 5 Microscopic morphology electron micrographs of the radial cross-section and axial interface of the carbon black / methyl cellulose aerogel fiber obtained in Example 3; Figure 6 Microscopic morphology electron micrographs of the radial cross-section and axial interface of the carbon black / methyl cellulose aerogel fiber obtained in Example 4; Figure 7 Differential scanning calorimetry curve graph of the encapsulated phase change composite fiber obtained in Example 1; Figure 8 Infrared photo of the encapsulated phase change composite fiber obtained in Example 1 during electroheating. Detailed Description of the Invention

[0033] The following further describes the specific embodiments of the present invention.

[0034] In the present invention, unless otherwise specified, the raw materials and equipment used can be purchased from the market or are commonly used in the art. The methods in the examples, unless otherwise specified, are conventional methods in the art.

[0035] The encapsulated electrothermal phase change fiber prepared by the present invention uses carbon black / methyl cellulose aerogel fiber as the matrix material, with a phase change material filled inside the fiber and a polymer solution used for encapsulation to prepare a shell layer on the outside. The carbon black / methyl cellulose aerogel fiber provides electrical conductivity and electrothermal performance, the phase change material provides heat storage performance, and the encapsulation shell layer provides mechanical performance and prevents the phase change material from leaking.

[0036] Test Methods

[0037] Structural Characterization: The orientation and disordered pore structure of carbon black / methyl cellulose fibers and the morphology of the encapsulated electrothermal phase change fibers were observed using a scanning electron microscope (SU-3500) at an accelerating voltage of 5 kV and a sputtering time of 90 s. To observe the cross-section of the fibers, the fibers were immersed in liquid nitrogen at -196 °C. After complete freezing, the fibers were brittlely broken with tweezers to obtain the cross-section to be observed. The porosity of the carbon black / methyl cellulose fibers was measured using a mercury porosimeter (AutoPore IV 9510). The pore size of the carbon black / methyl cellulose fibers was calculated by the following formula: Structural Characterization: The orientation and disordered pore structure of carbon black / methyl cellulose fibers and the morphology of the encapsulated electrothermal phase change fibers were observed using a scanning electron microscope (SU-3500) at an accelerating voltage of 5 kV and a sputtering time of 90 s. To observe the cross-section of the fibers, the fibers were immersed in liquid nitrogen at -196 °C. After complete freezing, the fibers were brittlely broken with tweezers to obtain the cross-section to be observed. The porosity of the carbon black / methyl cellulose fibers was measured using a mercury porosimeter (AutoPore IV 9510). The pore size of the carbon black / methyl cellulose fibers was calculated by the following formula: (1) where d is the average pore size of the fiber, d length is the pore length of the fiber in the electron microscope image, d width is the pore width of the fiber in the electron microscope image.

[0038] Conductivity Test: First, the encapsulation layers at both ends of the encapsulated electrothermal phase change fibers were removed, and the copper tape was connected to the fiber sample with conductive silver paste. Subsequently, the wires of a digital multimeter (Keithley 2611B) were connected to the copper tape at both ends of the fiber to measure the resistance of the sample. The fiber conductivity ( κ ) was calculated by the following formula: κ = L / RS (2) where R is the resistance of the fiber, L is the length of the fiber, S is the cross-sectional area of the fiber.

[0039] Phase Change Property Characterization: The phase change properties of the encapsulated electrothermal phase change fibers were analyzed using a differential scanning calorimeter (TA-Q200) Test of electrothermal conversion efficiency: Copper tape was pasted at both ends of the encapsulated electrothermal phase change fiber. The sample was connected to a power supply and a DC voltage was applied, and the current data was recorded in real time. The temperature on the surface of the encapsulated phase change composite fiber was measured using an infrared thermal imager. The distance between the sample and the lens of the infrared thermal imager was maintained at 30 cm. The phase change time of the encapsulated electrothermal phase change fiber during electric heating was counted by the infrared thermal imager, and the electrothermal conversion efficiency was calculated by the following formula: (3) Where η is the electrothermal conversion efficiency, m is the mass of the encapsulated electrothermal phase change fiber, ΔH m is the phase change enthalpy of the encapsulated electrothermal phase change fiber, U is the voltage applied to the fiber, I is the current passing through the fiber, t is the time experienced during the phase change process of the fiber.

[0040] Example 1 The preparation method of the encapsulated electrothermal phase change fiber in this example includes the following steps: 1) First, 10 g of carbon black was dissolved in 100 ml of water, and ultrasonic treatment was performed for 20 min using an ultrasonic cell disrupter to prepare a nano - monomer dispersion in which carbon black was stably present. Then, 10 g of methyl cellulose was added, and the mixture was stirred at a rotation speed of 800 rpm for 1 hour to prepare a carbon black / methyl cellulose spinning solution with a carbon black concentration and a methyl cellulose concentration of 1:1; 2) The carbon black / methyl cellulose spinning solution obtained in step 1) was extruded into a semiconductor copper ring cold source at a temperature of - 30 °C through a spinning needle on an injection pump at an extrusion speed of 3 ml / h. The extrusion diameter of the fiber was controlled to be 700 μm. The spinning solution entered the cold source and was gradually frozen. The frozen fiber was collected using a take - up reel, and then the collected fiber was freeze - dried at - 60 °C and 0.05 mbar for 24 h, thus obtaining a carbon black / methyl cellulose aerogel fiber with an average pore diameter of 102 μm, a porosity of 83%, a specific surface area of 24 m 2 / g, and a conductivity of 129.9 S / m; 3) The carbon black / methyl cellulose aerogel fiber obtained in step 2) was immersed in molten polyethylene glycol and placed in a vacuum oven at 60 °C for vacuum impregnation for 5 min. Then, the fiber was taken out and cooled to room temperature to obtain an electrothermal phase change fiber; 4) Dissolve 10 g of thermoplastic polyurethane particles in 100 ml of N,N-dimethylformamide, stir at a rotation speed of 500 rpm for 24 hours to obtain a 10 w / v% polyurethane encapsulation solution. Immerse the electrothermal phase change fiber obtained in step 3) in the polyurethane solution for 30 s, use a sieve plate with a pore size of 800 μm to scrape off the excess solution, and heat it through an 80 °C heater to volatilize the solvent to complete the shell encapsulation. Then place the fiber 5 cm above the 80 °C heater and heat it for 10 min, and impregnate and dry it repeatedly 2 times to obtain the encapsulated electrothermal phase change fiber.

[0041] The scanning electron microscope photos of the radial cross-section and axial cross-section of the carbon black / methyl cellulose aerogel fiber obtained in this example are as Figure 1 shown in a of Figure 1 and b of Figure 2 shown; the scanning electron microscope photo of the radial cross-section of the obtained electrothermal phase change fiber is as Figure 3 shown; the scanning electron microscope photo of the radial cross-section of the obtained encapsulated electrothermal phase change fiber is as Figure 7 shown, and its differential scanning calorimetry curve is as Figure 8 shown, and its infrared photo during electric heating is as

[0042] In the present invention, carbon black / methyl cellulose aerogel fibers are prepared by adopting a freeze-spinning technique, then polyethylene glycol is impregnated through vacuum, and the fibers are dip-coated with a polyurethane solution to obtain fibers having advantages such as high conductivity, high energy storage density, high electrothermal conversion efficiency, excellent flexibility and stability.

[0043] For the encapsulated electrothermal phase change fiber produced by the preparation method of the present invention, a carbon black / methyl cellulose aerogel fiber containing an oriented conductive network is used as the substrate. The oriented conductive network structure improves the charge transfer efficiency of the fiber. The conductivity of the aerogel fiber is 102 S / m, and it has the characteristics of a high porosity of 83% and a large specific surface area of 24 m 2 / g. With a small amount of conductive material, excellent electrothermal performance is achieved, enabling more phase change materials to be filled inside the fiber, thereby ensuring that the fiber has a high energy storage density. The carbon black / methyl cellulose content of the encapsulated electrothermal phase change fiber is 16 wt%, the phase change material content is 79 wt%, the conductivity is 80 S / m, the phase change enthalpy is 124.5 J / g, and the electrothermal conversion efficiency under 20 V voltage heating is 96%. In addition, the three-dimensional porous structure of the conductive network helps to quickly conduct heat to the phase change material and the heat can be evenly dispersed in the entire phase change material matrix, avoiding local accumulation of heat in the phase change material and significantly improving the electrothermal conversion efficiency. The electrothermal conversion efficiency of the encapsulated electrothermal phase change fiber for converting electrical energy into phase change energy can reach up to 96% at most.

[0044] After undergoing 50 phase change cycles and electrothermal heating-cooling cycles, the encapsulated electrothermal phase change fiber of the present invention still maintains stable phase change properties because polyethylene glycol has stable phase change characteristics. The encapsulated electrothermal phase change fiber of the present invention can still maintain stable conductive and electrothermal properties when bent or knotted, and no phase change material leakage will occur in high-temperature and high-pressure environments because the encapsulation layer significantly improves the mechanical properties and structural stability of the encapsulated electrothermal phase change fiber. When the fiber of the present invention is woven into a fabric, it can quickly complete phase change energy charging and maintain a constant temperature for a long time. By detecting its hydrophobic and moisture permeability, it is known that the initial water contact angle of the fabric is 100°, and the moisture permeability is 83.8 g m −2 h −1 , with good hydrophobicity and transmittance, and excellent wearable comfort. Finally, the obtained fiber has excellent heat storage and electrothermal properties, has long-term use stability, and is very suitable for personal thermal management.

[0045] Example 2 1) First, dissolve 10 g of carbon black in 100 ml of water, and prepare a nano-monomer dispersion in which carbon black is stably present by ultrasonic treatment with an ultrasonic cell disruptor for 20 min. Then add 10 g of methyl cellulose and stir at a speed of 800 rpm for 1 hour to prepare a carbon black / methyl cellulose spinning solution with a carbon black concentration and a methyl cellulose concentration of 10 wt%; 2) Extrude the carbon black / methyl cellulose spinning solution obtained in step 1) into a semiconductor copper ring cold source with a temperature of -10 °C through a spinning needle on an injection pump at an extrusion speed of 1 ml / h. The extrusion diameter of the fiber is controlled to be 700 μm. The spinning solution enters the cold source and is gradually frozen. Use a take-up reel to collect the frozen fiber, and then freeze-dry the collected fiber at -60 °C and 0.05 mbar for 24 h to obtain a carbon black / methyl cellulose aerogel fiber with an average pore diameter of 135 μm, a porosity of 80%, a specific surface area of 12 m 2 / g, and a conductivity of 140 S / m; 3) Immerse the carbon black / methyl cellulose aerogel fiber obtained in step 2) in molten polyethylene glycol, place it in a vacuum oven at 60 °C for vacuum impregnation for 5 min, and then take out the fiber and cool it to room temperature to obtain an electrothermal phase change fiber; 4) Dissolve 10 g of thermoplastic polyurethane particles in 100 ml of N,N-dimethylformamide, stir at a speed of 500 rpm for 24 hours to obtain a 10 w / v% polyurethane encapsulation solution. Immerse the electrothermal phase change fiber obtained in step 3) in the polyurethane solution for 30 s, use a sieve plate with a pore size of 800 μm to scrape off the excess solution, and heat it through an 80 °C heater to volatilize the solvent to complete the shell encapsulation. Then place the fiber 5 cm above the 80 °C heater and heat for 10 min, impregnate and dry repeatedly 2 times to obtain the encapsulated electrothermal phase change fiber.

[0046] The scanning electron microscope photos of the radial cross-section and axial cross-section of the carbon black / methyl cellulose aerogel fiber obtained in this example are as Figure 4 shown in a of Figure 4 and b of

[0047] The carbon black / methyl cellulose content of the encapsulated electrothermal phase change fiber prepared in this example is 17 wt%, the phase change material content is 78 wt%, the conductivity is 86.8 S / m, the phase change enthalpy is 122.8 J / g, and the electrothermal conversion efficiency under 20 V voltage heating is 98%.

[0048] Example 3 1) First, take 10 g of carbon black and dissolve it in 100 ml of water, and prepare a nano-monomer dispersion in which carbon black is stably present by ultrasonic treatment with an ultrasonic cell disruptor for 20 min. Then add 10 g of methyl cellulose and stir at a speed of 800 rpm for 1 hour to prepare a carbon black / methyl cellulose spinning solution with a carbon black concentration and a methyl cellulose concentration of 10 wt% each; 2) Extrude the carbon black / methyl cellulose spinning solution obtained in step 1) into a semiconductor copper ring cold source with a temperature of -50 °C through a spinning needle on an injection pump at an extrusion speed of 4 ml / h. Control the extrusion diameter of the fiber to be 700 μm. The spinning solution enters the cold source and is gradually frozen. Use a take-up reel to collect the frozen fiber, and then freeze-dry the collected fiber under the conditions of -60 °C and 0.05 mbar for 24 h to obtain a carbon black / methyl cellulose aerogel fiber with an average pore size of 78 μm, a porosity of 81%, a specific surface area of 25 m 2 / g, and a conductivity of 103 S / m; 3) Immerse the carbon black / methyl cellulose aerogel fiber obtained in step 2) in molten polyethylene glycol, place it in a 60 °C vacuum oven for vacuum impregnation for 5 min, then take out the fiber and cool it at room temperature to obtain an electrothermal phase change fiber; 4) Dissolve 10 g of thermoplastic polyurethane particles in 100 ml of N,N-dimethylformamide, stir at a speed of 500 rpm for 24 hours to obtain a 10 w / v% polyurethane encapsulation solution. Immerse the electrothermal phase change fibers obtained in step 3) in the polyurethane solution for 30 s, scrape off the excess solution using a sieve plate with a pore size of 800 μm, and heat through an 80 °C heater to volatilize the solvent to complete the shell encapsulation. Then place the fibers 5 cm above the 80 °C heater and heat for 10 min, impregnate and dry repeatedly 2 times to obtain encapsulated electrothermal phase change fibers.

[0049] The scanning electron microscope photos of the radial cross-section and axial cross-section of the carbon black / methyl cellulose aerogel fibers obtained in this example are as Figure 5 shown in a of Figure 5 and b of

[0050] The carbon black / methyl cellulose content of the encapsulated electrothermal phase change fibers prepared in this example is 17 wt%, the phase change material content is 78 wt%, the conductivity is 64.2 S / m, the phase change enthalpy is 122.7 J / g, and the electrothermal conversion efficiency under a heating voltage of 20 V is 93%.

[0051] Example 4 1) First, dissolve 8 g of carbon black in 100 ml of water, and prepare a nano-monomer dispersion solution in which carbon black is stably present through ultrasonic treatment with an ultrasonic cell disruptor for 20 min. Then add 8 g of methyl cellulose and stir at a speed of 800 rpm for 1 hour to prepare a carbon black / methyl cellulose spinning solution with a carbon black concentration of 8 wt% and a methyl cellulose concentration of 10 wt%; 2) Extrude the carbon black / methyl cellulose spinning solution obtained in step 1) into a semiconductor copper ring cold source with a temperature of -30 °C through a spinning needle on an injection pump at an extrusion speed of 3 ml / h. Control the extrusion diameter of the fiber to be 700 μm. The spinning solution enters the cold source and is gradually frozen. Use a take-up reel to collect the frozen fibers, and then freeze-dry the collected fibers at -60 °C and 0.05 mbar for 24 h to obtain carbon black / methyl cellulose aerogel fibers with an average pore size of 175 μm, a porosity of 84%, a specific surface area of 25 m 2 / g, and a conductivity of 98.2 S / m; 3) Immerse the carbon black / methyl cellulose aerogel fibers obtained in step 2) in molten polyethylene glycol, place them in a 60 °C vacuum oven for vacuum impregnation for 5 min, then take out the fibers and cool them at room temperature to obtain electrothermal phase change fibers; 4) Dissolve 10 g of thermoplastic polyurethane particles in 100 ml of N,N-dimethylformamide, stir for 24 hours at a rotation speed of 500 rpm to obtain a 10 w / v% polyurethane encapsulation solution. Immerse the electrothermal phase change fibers obtained in step 3) in the polyurethane solution for 30 s, use a sieve plate with a pore size of 800 μm to scrape off the excess solution, and heat through an 80 °C heater to volatilize the solvent to complete the shell encapsulation. Then place the fibers 5 cm above the 80 °C heater and heat for 10 min, impregnate and dry repeatedly 2 times to obtain encapsulated electrothermal phase change fibers.

[0052] The carbon black / methyl cellulose content of the encapsulated electrothermal phase change fibers prepared in this example is 15 wt%, the phase change material content is 80 wt%, the conductivity is 61.8 S / m, the phase change enthalpy is 126.1 J / g, and the electrothermal conversion efficiency under 20 V voltage heating is 81%.

[0053] Example 5 1) First, dissolve 12 g of carbon black in 100 ml of water, and ultrasonically treat for 20 min with an ultrasonic cell disrupter to prepare a nano-monomer dispersion in which carbon black is stably present. Then add 8 g of methyl cellulose and stir for 1 hour at a rotation speed of 800 rpm to prepare a carbon black / methyl cellulose spinning solution with a carbon black concentration of 12 wt% and a methyl cellulose concentration of 10 wt%. 2) Extrude the carbon black / methyl cellulose spinning solution obtained in step 1) into a -30 °C semiconductor copper ring cold source through a spinning needle on an injection pump at an extrusion speed of 3 ml / h. Control the extrusion diameter of the fiber to be 700 μm. The spinning solution enters the cold source and is gradually frozen. Use a take-up reel to collect the frozen fibers, and then freeze-dry the collected fibers for 24 h under the conditions of -60 °C and 0.05 mbar to obtain carbon black / methyl cellulose aerogel fibers with an average pore size of 98 μm, a porosity of 79%, a specific surface area of 21 m 2 / g, and a conductivity of 135 S / m. 3) Immerse the carbon black / methyl cellulose aerogel fibers obtained in step 2) in molten polyethylene glycol, place them in a 60 °C vacuum oven for vacuum impregnation for 5 min, then take out the fibers and cool them to room temperature to obtain electrothermal phase change fibers. 4) Dissolve 10 g of thermoplastic polyurethane particles in 100 ml of N,N-dimethylformamide, stir at a speed of 500 rpm for 24 hours to obtain a 10 w / v% polyurethane encapsulation solution. Immerse the electrothermal phase change fibers obtained in step 3) in the polyurethane solution for 30 s, use a sieve plate with a pore size of 800 μm to scrape off the excess solution, and heat through an 80 °C heater to volatilize the solvent to complete the shell encapsulation. Then place the fibers 5 cm above the 80 °C heater and heat for 10 min, and repeat the impregnation and drying 2 times to obtain encapsulated electrothermal phase change fibers.

[0054] The carbon black / methyl cellulose content of the encapsulated electrothermal phase change fibers prepared in this example is 17 wt%, the phase change material content is 78 wt%, the conductivity is 83.1 S / m, the phase change enthalpy is 123.5 J / g, and the electrothermal conversion efficiency under 20 V voltage heating is 98%.

[0055] Example 6 The difference from Example 4 is that the carbon black concentration is 14 wt%.

[0056] The carbon black / methyl cellulose aerogel fibers prepared in this example have an average pore size of 92 μm, a porosity of 79%, a specific surface area of 29 m 2 / g, and a conductivity of 138.5 S / m.

[0057] The carbon black / methyl cellulose content of the encapsulated electrothermal phase change fibers prepared in this example is 17 wt%, the phase change material content is 78 wt%, the conductivity is 85.2 S / m, the phase change enthalpy is 123.0 J / g, and the electrothermal conversion efficiency under 20 V voltage heating is 98%.

[0058] Example 7 The difference from Example 4 is that the carbon black concentration is 16 wt%.

[0059] The carbon black / methyl cellulose aerogel fibers prepared in this example have an average pore size of 88 μm, a porosity of 78%, a specific surface area of 30 m 2 / g, and a conductivity of 145.1 S / m.

[0060] The carbon black / methyl cellulose content of the encapsulated electrothermal phase change fibers prepared in this example is 18 wt%, the phase change material content is 77 wt%, the conductivity is 88.7 S / m, the phase change enthalpy is 122.7 J / g, and the electrothermal conversion efficiency under 20 V voltage heating is 99%.

[0061] Example 8 1) First, dissolve 10 g of carbon black in 100 ml of water, and prepare a nanomonomer dispersion in which carbon black is stably present by ultrasonic treatment with an ultrasonic cell disrupter for 20 min. Then, add 10 g of methyl cellulose and stir at a rotation speed of 800 rpm for 1 hour to prepare a carbon black / methyl cellulose spinning solution with a carbon black concentration and a methyl cellulose concentration both of 10 wt%. 2) Extrude the carbon black / methyl cellulose spinning solution obtained in step 1) into a semiconductor copper ring cold source at a temperature of -30 °C through a spinning needle on an injection pump at an extrusion speed of 3 ml / h. Control the extrusion diameter of the fiber to be 700 μm. The spinning solution enters the cold source and is gradually frozen. Use a take-up reel to collect the frozen fiber, and then freeze-dry the collected fiber at -60 °C and 0.05 mbar for 24 h to obtain a carbon black / methyl cellulose aerogel fiber with an average pore diameter of 170 μm, a porosity of 83%, a specific surface area of 24 m 2 / g, and a conductivity of 130 S / m; 3) Immerse the carbon black / methyl cellulose aerogel fiber obtained in step 2) in a molten paraffin solution, place it in a vacuum oven at 60 °C for vacuum impregnation for 5 min, and then take out the fiber and cool it at room temperature to obtain an electrothermal phase change fiber; 4) Dissolve 10 g of thermoplastic polyurethane particles in 100 ml of N,N-dimethylformamide and stir at a rotation speed of 500 rpm for 24 hours to obtain a 10 w / v% polyurethane encapsulation solution. Immerse the electrothermal phase change fiber obtained in step 3) in the polyurethane solution for 30 s, use a sieve plate with a pore size of 800 μm to scrape off the excess solution, and heat it with an 80 °C heater to volatilize the solvent to complete the shell encapsulation. Then, place the fiber 5 cm above the 80 °C heater and heat it for 10 min, and impregnate and dry it repeatedly 2 times to obtain an encapsulated electrothermal phase change fiber.

[0062] The carbon black / methyl cellulose content of the encapsulated electrothermal phase change fiber prepared in this example is 17 wt%, the phase change material content is 77 wt%, the conductivity is 78.4 S / m, the phase change enthalpy is 193.7 J / g, and the electrothermal conversion efficiency under a heating voltage of 20 V is 94%.

[0063] Example 9 1) First, dissolve 10 g of carbon black in 100 ml of water, and prepare a nanomonomer dispersion in which carbon black is stably present by ultrasonic treatment with an ultrasonic cell disrupter for 20 min. Then, add 10 g of methyl cellulose and stir at a rotation speed of 800 rpm for 1 hour to prepare a carbon black / methyl cellulose spinning solution with a carbon black concentration and a methyl cellulose concentration both of 10 wt%. 2) The carbon black / methyl cellulose spinning solution obtained in step 1) was extruded into a semiconductor copper ring cold source at a temperature of -30 °C through a spinning needle on an injection pump at an extrusion speed of 3 ml / h. The extrusion diameter of the fiber was controlled to be 700 μm. The spinning solution entered the cold source and was gradually frozen. The frozen fiber was collected using a take-up reel, and then the collected fiber was freeze-dried at -60 °C and 0.05 mbar for 24 h, and a carbon black / methyl cellulose aerogel fiber with an average pore diameter of 170 μm, a porosity of 83%, a specific surface area of 24 m 2 / g, and a conductivity of 130 S / m was prepared by the freeze-spinning technique; 3) The carbon black / methyl cellulose aerogel fiber obtained in step 2) was immersed in a molten erythritol solution and placed in a vacuum oven at 60 °C for vacuum impregnation for 5 min. Then the fiber was taken out and cooled to room temperature to obtain an electrothermal phase change fiber; 4) 10 g of thermoplastic polyurethane particles were dissolved in 100 ml of N,N-dimethylformamide and stirred at a speed of 500 rpm for 24 hours to obtain a 10 w / v% polyurethane encapsulation solution. The electrothermal phase change fiber obtained in step 3) was soaked in the polyurethane solution for 30 s, and the excess solution was scraped off using a sieve plate with a pore size of 800 μm and the solvent was volatilized by heating with an 80 °C heater to complete the shell encapsulation. Then the fiber was placed 5 cm above the 80 °C heater and heated for 10 min, and the impregnation and drying were repeated 2 times to obtain an encapsulated electrothermal phase change fiber.

[0064] The carbon black / methyl cellulose content of the encapsulated electrothermal phase change fiber prepared in this example was 13 wt%, the phase change material content was 77 wt%, the conductivity was 78.4 S / m, the phase change enthalpy was 66.7 J / g, and the electrothermal conversion efficiency under a heating voltage of 20 V was 98%.

[0065] Example 10 1) First, 10 g of carbon black was dissolved in 100 ml of water, and a nano-monomer dispersion solution in which carbon black was stably present was prepared by ultrasonic treatment with an ultrasonic cell disruptor for 20 min. Then 10 g of methyl cellulose was added, and the mixture was stirred at a speed of 800 rpm for 1 hour to prepare a carbon black / methyl cellulose spinning solution with a carbon black concentration and a methyl cellulose concentration of 10 wt%; 2) The carbon black / methyl cellulose spinning solution obtained in step 1) is extruded into a semiconductor copper ring cold source at a temperature of -30 °C through a spinning needle on an injection pump at an extrusion speed of 3 ml / h. The extrusion diameter of the fiber is controlled to be 700 μm. The spinning solution enters the cold source and is gradually frozen. The frozen fiber is collected using a take-up reel, and then the collected fiber is freeze-dried at -60 °C and 0.05 mbar for 24 h, thus obtaining a carbon black / methyl cellulose aerogel fiber with an average pore diameter of 170 μm, a porosity of 83%, a specific surface area of 24 m 2 / g, and a conductivity of 130 S / m; 3) The carbon black / methyl cellulose aerogel fiber obtained in step 2) is immersed in molten polyethylene glycol and placed in a vacuum oven at 60 °C for vacuum impregnation for 5 min. Then the fiber is taken out and cooled at room temperature to obtain an electrothermal phase change fiber; 4) Polytetramethylsiloxane resin and a curing agent are mixed in a ratio of 10:1, and a solution cured in an oven at 50 °C for 15 min is obtained to get a polytetramethylsiloxane solution. The electrothermal phase change fiber obtained in step 3) is soaked in the polytetramethylsiloxane solution for 30 s, and the excess solution is scraped off using a sieve plate with a pore size of 800 μm and the solvent is volatilized by heating with an 80 °C heater to complete the shell encapsulation. Then the fiber is placed 5 cm above the 80 °C heater and heated for 10 min, and the impregnation and drying are repeated 2 times to obtain an encapsulated electrothermal phase change fiber.

[0066] The carbon black / methyl cellulose content of the encapsulated electrothermal phase change fiber prepared in this example is 16 wt%, the phase change material content is 79 wt%, the conductivity is 79.8 S / m, the phase change enthalpy is 124.6 J / g, and the electrothermal conversion efficiency under 20 V voltage heating is 96%.

[0067] Example 11 1) First, 10 g of carbon black is dissolved in 100 ml of water, and a nano monomer dispersion liquid in which carbon black is stably present is prepared by ultrasonic treatment with an ultrasonic cell disrupter for 20 min. Then 10 g of methyl cellulose is added, and the mixture is stirred at a rotation speed of 800 rpm for 1 hour to prepare a carbon black / methyl cellulose spinning solution with a carbon black concentration and a methyl cellulose concentration of 10 wt% each; 2) The carbon black / methyl cellulose spinning solution obtained in step 1) was extruded into a semiconductor copper ring cold source at a temperature of -30 °C through a spinning needle on an injection pump at an extrusion speed of 3 ml / h. The extrusion diameter of the fiber was controlled to be 700 μm. The spinning solution entered the cold source and was gradually frozen. The frozen fiber was collected using a take-up reel, and then the collected fiber was freeze-dried at -60 °C and 0.05 mbar for 24 h, thus obtaining a carbon black / methyl cellulose aerogel fiber with an average pore diameter of 170 μm, a porosity of 83%, a specific surface area of 24 m 2 / g, and a conductivity of 130 S / m; 3) The carbon black / methyl cellulose aerogel fiber obtained in step 2) was immersed in molten polyethylene glycol and placed in a vacuum oven at 60 °C for vacuum impregnation for 5 min. Then the fiber was taken out and cooled to room temperature to obtain an electrothermal phase change fiber; 4) 10 g of thermoplastic polyurethane particles were dissolved in 100 ml of N,N-dimethylformamide and stirred at a speed of 500 rpm for 24 hours to obtain a 10 w / v% polyurethane encapsulation solution. The electrothermal phase change fiber obtained in step 3) was soaked in the polyurethane solution for 30 s, and the excess solution was scraped off using a sieve plate with a pore size of 1000 μm and the solvent was volatilized by heating with an 80 °C heater to complete the shell encapsulation. Then the fiber was placed 5 cm above the 80 °C heater and heated for 10 min, and the impregnation and drying were repeated 6 times to obtain an encapsulated electrothermal phase change fiber.

[0068] The carbon black / methyl cellulose content of the encapsulated electrothermal phase change fiber prepared in this example was 11 wt%, the phase change material content was 68 wt%, the conductivity was 51.6 S / m, the phase change enthalpy was 124.6 J / g, and the electrothermal conversion efficiency under a heating voltage of 20 V was 97%.

[0069] Comparative Example 1 1) First, 10 g of carbon black was dissolved in 100 ml of water, and a nano-monomer dispersion solution in which carbon black was stably present was prepared by ultrasonic treatment with an ultrasonic cell disruptor for 20 min. Then 10 g of methyl cellulose was added, and the mixture was stirred at a speed of 800 rpm for 1 hour to prepare a carbon black / methyl cellulose spinning solution with a carbon black concentration and a methyl cellulose concentration of 10 wt% each; 2) The carbon black / methyl cellulose spinning solution obtained in step 1) was extruded into a liquid nitrogen cold source at a temperature of -196 °C through a spinning needle on an injection pump at an extrusion speed of 4 ml / h. The extrusion diameter of the fiber was controlled to be 700 μm. The spinning solution entered the cold source and was gradually frozen. The frozen fiber was collected using a take-up reel, and then the collected fiber was freeze-dried at -60 °C and 0.05 mbar for 24 h, thus obtaining a carbon black / methyl cellulose aerogel fiber with an average pore diameter of 25 μm, a porosity of 82%, a specific surface area of 30 m 2 / g, and a conductivity of 83 S / m; 3) The carbon black / methyl cellulose aerogel fiber obtained in step 2) was immersed in molten polyethylene glycol and placed in a vacuum oven at 60 °C for vacuum impregnation for 5 min. Then the fiber was taken out and cooled to room temperature to obtain an electrothermal phase change fiber; 4) 10 g of thermoplastic polyurethane particles were dissolved in 100 ml of N,N-dimethylformamide and stirred at a speed of 500 rpm for 24 hours to obtain a 10 w / v% polyurethane encapsulation solution. The electrothermal phase change fiber obtained in step 3) was soaked in the polyurethane solution for 30 s, and the excess solution was scraped off using a sieve plate with a pore size of 800 μm and the solvent was volatilized by heating with an 80 °C heater to complete the shell encapsulation. Then the fiber was placed 5 cm above the 80 °C heater and heated for 10 min, and the impregnation and drying were repeated 2 times to obtain an encapsulated electrothermal phase change fiber.

[0070] The carbon black / methyl cellulose content of the encapsulated electrothermal phase change fiber prepared in this comparative example was 16 wt%, the phase change material content was 79 wt%, the conductivity was 52.5 S / m, the phase change enthalpy was 124.2 J / g, and the electrothermal conversion efficiency under 20 V voltage heating was 80%.

[0071] Comparative Example 2 The difference from the example is that graphite powder was used to replace carbon black.

[0072] This comparative example obtained a graphite / methyl cellulose aerogel fiber with an average pore diameter of 98 μm, a porosity of 83%, a specific surface area of 24 m 2 / g, and a conductivity of 97.5 S / m.

[0073] The carbon black / methyl cellulose content of the encapsulated electrothermal phase change fiber prepared in this comparative example was 16 wt%, the phase change material content was 79 wt%, the conductivity was 59.7 S / m, the phase change enthalpy was 124.3 J / g, and the electrothermal conversion efficiency under 20 V voltage heating was 86%.

[0074] Comparative Example 3 Different from Steps 1) and 2) of Example 1: 1) Preparation of carbon black / polyurethane spinning solution: First, 10 g of carbon black was dissolved in 100 ml of N,N-dimethylformamide (the solvent for cryogenic spinning is water), and a nano-monomer dispersion with stable carbon black was prepared by ultrasonic treatment with an ultrasonic cell disruptor for 20 min. Then, 15 g of thermoplastic polyurethane particles were added, and the mixture was stirred at a speed of 500 rpm for 8 h to obtain a homogeneous spinning solution; 2) After loading the prepared carbon black / TPU spinning solution into a syringe, the spinning solution was extruded into a coagulation bath at a rate of 4 ml / h through a micro-injection pump, and absolute ethanol was used as the coagulation bath. Principle of wet spinning: Since the solubility of TPU in ethanol and DMF is different, microphase separation occurs after the spinning solution enters the coagulation bath, and thus it solidifies to obtain carbon black / TPU composite fibers. The fibers were continuously collected by a take-up shaft motor, and then dried in air at 40 °C to obtain carbon black / TPU composite aerogel fibers.

[0075] This comparative example prepared graphite / methylcellulose aerogel fibers with an average pore size of 22 μm, a porosity of 68%, a specific surface area of 33 m 2 / g, and an electrical conductivity of 63.6 S / m.

[0076] The content of graphite / methylcellulose in the encapsulated electrothermal phase change fibers prepared in this comparative example was 15 wt%, the content of the phase change material was 69 wt%, the electrical conductivity was 38.2 S / m, the phase change enthalpy was 108.8 J / g, and the electrothermal conversion efficiency under a heating voltage of 20 V was 43%.

[0077] Comparative Example 4 The difference from Example 1 is that carboxymethylcellulose was used to replace methylcellulose.

[0078] This comparative example prepared carbon black / carboxymethylcellulose aerogel fibers with an average pore size of 103 μm, a porosity of 83%, a specific surface area of 25 m 2 / g, and an electrical conductivity of 57.7 S / m.

[0079] The content of carbon black / carboxymethylcellulose in the encapsulated electrothermal phase change fibers prepared in this comparative example was 16 wt%, the content of the phase change material was 79 wt%, the electrical conductivity was 37.6 S / m, the phase change enthalpy was 124.2 J / g, and the electrothermal conversion efficiency under a heating voltage of 20 V was 38%.

[0080] Comparative Example 5 1) First, dissolve 6 g of carbon black in 100 ml of water and prepare a nano - monomer dispersion in which carbon black is stably present through ultrasonic treatment with an ultrasonic cell disruptor for 20 min. Then, add 10 g of methyl cellulose and stir at a rotation speed of 800 rpm for 1 hour to prepare a carbon black / methyl cellulose spinning solution with a carbon black concentration of 6 wt% and a methyl cellulose concentration of 10 wt%. 2) Extrude the carbon black / methyl cellulose spinning solution obtained in step 1) into a semiconductor copper ring cold source at a temperature of - 30 °C through a spinning needle on an injection pump at an extrusion speed of 3 ml / h. Control the extrusion diameter of the fiber to be 700 μm. The spinning solution enters the cold source and is gradually frozen. Use a take - up reel to collect the frozen fiber, and then freeze - dry the collected fiber at - 60 °C and 0.05 mbar for 24 h to obtain a carbon black / methyl cellulose aerogel fiber with an average pore diameter of 113 μm, a porosity of 86%, a specific surface area of 26 m 2 / g, and an electrical conductivity of 39.8 S / m. 3) Immerse the carbon black / methyl cellulose aerogel fiber obtained in step 2) in molten polyethylene glycol, place it in a vacuum oven at 60 °C for vacuum impregnation for 5 min, then take out the fiber and cool it to room temperature to obtain an electrothermal phase - change fiber. 4) Dissolve 10 g of thermoplastic polyurethane particles in 100 ml of N,N - dimethylformamide and stir at a rotation speed of 500 rpm for 24 h to obtain a 10 w / v% polyurethane encapsulation solution. Immerse the electrothermal phase - change fiber obtained in step 3) in the polyurethane solution for 30 s, use a sieve plate with a pore size of 800 μm to scrape off the excess solution, and heat it with an 80 °C heater to volatilize the solvent to complete the shell encapsulation. Then, place the fiber 5 cm above the 80 °C heater and heat it for 10 min, and repeat the impregnation and drying 2 times to obtain an encapsulated electrothermal phase - change fiber.

[0081] The carbon black / methyl cellulose content of the encapsulated electrothermal phase - change fiber prepared in this comparative example is 15 wt%, the phase - change material content is 80 wt%, the electrical conductivity is 24.3 S / m, the phase - change enthalpy is 126.7 J / g, and the electrothermal conversion efficiency under a 20 V voltage heating is 36%.

[0082] Comparative Example 6 The difference from Example 1 is that the carbon black concentration is 4 wt%.

[0083] This comparative example prepared a carbon black / methyl cellulose aerogel fiber with an average pore diameter of 119 μm, a porosity of 87%, a specific surface area of 31 m 2 / g, and an electrical conductivity of 11.4 S / m.

[0084] The carbon black / methyl cellulose content of the encapsulated electrothermal phase change fiber prepared in this comparative example is 17 wt%, the phase change material content is 78 wt%, the conductivity is 85.2 S / m, the phase change enthalpy is 123.0 J / g, and the electrothermal conversion efficiency under 20 V voltage heating is 98%.

[0085] Comparative Example 7 The difference from Example 1 is that the carbon black concentration is 18 wt%.

[0086] In this comparative example, the viscosity of the spinning solution is too high to be extruded and spun into fibers.

[0087] Through the above examples and comparative examples, the encapsulated electrothermal phase change fiber obtained by the above technical solution of the present invention has high conductivity, high energy storage density, high electrothermal conversion efficiency, excellent mechanical flexibility and phase change stability, and has good applications in phase change energy storage, active electrothermal, and energy storage. Moreover, the preparation process is simple, green and environmentally friendly, with a short production cycle. At the same time, the raw materials are widely sourced and low-cost, suitable for large-scale production, and have broad application prospects in the field of personal thermal management.

[0088] The above is only a preferred embodiment of the present invention and does not impose any form of limitation on the present invention. Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art, without departing from the technical solution scope of the present invention, when making some changes or modifications using the above-disclosed technical content as equivalent change equivalent embodiments, but as long as it does not depart from the technical solution content of the present invention, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A method for preparing an encapsulated electrothermal phase change fiber having an axially oriented conductive network, characterized in that: The method comprises the following steps: 1) Firstly, dissolve carbon black in water and disperse it, then add methyl cellulose to prepare a carbon black / methyl cellulose spinning solution; 2) The carbon black / methyl cellulose spinning solution obtained in step 1) is squeezed into a cold source through a spinning needle on a syringe pump, and the spinning solution is gradually frozen when entering the cold source, and the frozen fibers are collected to obtain carbon black / methyl cellulose aerogel fibers with different oriented conductive network structures; 3) dipping the carbon black / methyl cellulose aerogel fiber obtained in step 2) into the molten phase change material, taking it out after vacuum impregnation and cooling it at room temperature to obtain an electrothermal phase change fiber; 4) The electrothermal phase change fiber obtained in step 3) is coated with a polymer solution by a dip coating method, and the shell layer packaging is completed by heating to evaporate the solvent, thereby obtaining a packaged electrothermal phase change fiber.

2. The preparation method according to claim 1, characterized in that: In step 1), the mass ratio of carbon black to methyl cellulose is 0.8-1.6:

1.

3. The preparation method according to claim 1, characterized in that: In step 1), the mass ratio of carbon black to methyl cellulose is 1.2-1.6:

1.

4. The preparation method according to claim 1, characterized in that In step 2), the cold source is a semiconductor annular cold source device, the temperature of the semiconductor annular cold source device is -10~-50 °C, and the extrusion speed of the carbon black / methyl cellulose fiber is set to 1~4 ml / h.

5. The preparation method according to claim 1, characterized in that In step 2), the carbon black / methyl cellulose aerogel fiber has a three-dimensional porous network structure composed of macroscopic pores with a pore size of 20-170 μm, a porosity of 75-85%, and a specific surface area of ​​10-30 m 2 / g, conductivity is 40~140 S / m.

6. The preparation method according to claim 1, characterized in that: In step 3), the phase change material is selected from any one of polyethylene glycol, paraffin, polyol, erythritol or polyolefin.

7. The preparation method according to claim 1, characterized in that: In step 4), the content of the graphene / methyl cellulose fiber network encapsulating the prepared electrothermal phase change fiber is 10-25wt%, the content of the phase change material is 55-85wt%, and the rest is the polymer shell layer.

8. The preparation method according to claim 1, characterized in that: In step 4), the content of the graphene / methyl cellulose fiber network of the prepared encapsulated electrothermal phase change fiber is 11-18wt%, the content of the phase change material is 68-82wt%, and the rest is the polymer shell layer.

9. The preparation method according to claim 1, characterized in that In step 4), the phase change enthalpy of the prepared encapsulated electrothermal phase change fiber is 85~200 J / g.

10. Use of the encapsulated electrothermal phase change fiber prepared by the preparation method according to any one of claims 1 to 9 in personal thermal management warm fabrics.

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