Multi-phase-change-point composite phase change fiber as well as preparation method and application thereof

Abstract

The invention relates to a multi-phase-change-point composite phase change fiber and a preparation method and application thereof, phase change materials with different phase change temperatures and a shell polymer solution capable of forming fiber are respectively injected through a multi-channel micro-fluidic chip, so that each phase fluid forms a laminar flow state in the chip; applying a high-voltage electrostatic field between an inlet and an outlet of the micro-fluidic chip, and performing directional stretching on the multiphase fluid by utilizing an electrostatic spinning process to form a composite liquid line with a multi-cavity core-shell structure; technological parameters such as fluid injection rate, electric field voltage, receiving distance and environment temperature and humidity are regulated and controlled, so that stable distribution of various core phase change materials in the fiber is ensured; the composite liquid line is cured to form phase change fibers, the phase change fibers are collected by a collecting device and subjected to post-treatment, and the functional phase change fibers with the multiple phase change temperature zones and the stable structure are obtained.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of functional thermal regulation material preparation, and particularly relates to a composite functional fiber with spatially ordered encapsulation of multi-component phase change materials and a preparation method thereof, which is achieved by using microfluidic technology combined with an electric field-induced forming mechanism, and is suitable for scenarios such as intelligent temperature control textiles, flexible thermal management systems, and phase change energy storage materials. BACKGROUND

[0002] Phase change materials have been widely used in the fields of building energy saving, electronic device heat dissipation, intelligent textiles, and wearable devices for thermal management, due to their ability to store and release heat approximately isothermally during the heat absorption and release process, high energy density, good thermal responsiveness, and compact structure. Among various application forms of phase change materials, phase change fibers, as an advanced material system that integrates thermal regulation functions into a flexible carrier, have become a hot research direction in functional fibers due to their strong flexibility, good wearability, and high thermal regulation efficiency.

[0003] Currently, mainstream phase change fibers usually use materials with a single phase change temperature point as the core, and common phase change materials include paraffin, fatty acids, alcohols, and their compounds. These materials release or absorb latent heat when the temperature rises or falls to a specific point, and undergo a phase change. However, due to their fixed phase change temperature, they can only regulate heat within a narrow temperature window, making it difficult to adapt to the thermal management needs of complex environments with "multiple time periods and multiple temperature zones", severely limiting the breadth and depth of their practical applications. In addition, common organic phase change materials are mostly solid-liquid types, which are prone to material leakage, migration, or interface instability during the phase change process, leading to decreased thermal regulation performance and poor structural durability of the fibers.

[0004] The current main preparation method for phase change fibers is electrospinning technology, which involves stretching a high polymer solution into nanoscale fibers through a high-voltage electrostatic field to preliminarily achieve the encapsulation of phase change materials. However, this method has many limitations, such as single fiber structure, poor size consistency, low encapsulation efficiency of phase change materials, easy leakage, high sensitivity to process parameters, and poor repeatability, making it difficult to achieve precise construction of multi-cavity and multi-core structures, and unable to meet the needs of highly complex and multi-functional phase change structures.

[0005] In recent years, microfluidic technology has been widely used in the development of high-throughput and multi-structure functional fibers due to its excellent controllability of multi-phase fluids at the microscale. By adjusting the flow rate, pressure, and interface behavior of different channels in the microfluidic chip, the construction of core-shell structure, coaxial structure, or multi-chamber structure can be achieved, effectively improving the complexity of the internal structure of the fiber and the encapsulation stability of the phase change material. Compared with electrospinning, the microfluidic method has the advantages of strong controllability of the forming process, good uniformity of fiber size, high repeatability, and suitability for a variety of material systems, making it suitable for the preparation of composite phase change fibers with precise structure and high functional integration.

[0006] Further, as a non-contact micro-scale regulation means, the electric field regulation technology has been introduced into the microfluidic field in recent years and can be used to regulate the flow interface, fluid boundary and component interface morphology of multi-phase fluid. The application of electric field between the inlet and outlet of the microfluidic chip can significantly improve the interface stability and distribution accuracy between fluid phases, thereby facilitating the formation and directional arrangement of multi-cavity structure and improving the overall formation quality and stability of the composite phase change fiber structure.

[0007] Therefore, it is urgent to develop a multi-phase change point composite phase change fiber that combines the precise construction capability of microfluidics and the electric field regulation mechanism, so as to realize the collaborative packaging and ordered distribution of multiple materials with different phase change temperatures, expand the effective temperature regulation range of the fiber, enhance the thermal stability and functional adaptability thereof, and meet the diversified needs of intelligent textiles, complex wearable systems and extreme environment thermal management applications. SUMMARY

[0008] The technical problem to be solved: In order to solve the technical problems of narrow temperature control response range, poor packaging stability and lack of controllability in the preparation process of existing phase change fibers, the present application provides a multi-phase change point composite phase change fiber combining the fluid structure construction capability of microfluidic chip and the electric field regulation mechanism, as well as a preparation method and application thereof. The method realizes the spatial ordered distribution and efficient packaging of multi-component phase change materials in the fiber by constructing a multi-chamber core-shell structure, significantly improves the temperature response width and structural stability of the fiber, and can meet the thermal management and intelligent temperature regulation needs under complex environment and extreme climate conditions.

[0009] Technical scheme: A preparation method of a multi-phase change point composite phase change fiber, comprising the following steps: (1) injecting phase change materials with different phase change temperatures and shell polymer solutions capable of forming fibers through a multi-channel microfluidic chip respectively, so that each phase fluid forms a laminar flow state in the chip; (2) applying a high-voltage electrostatic field between the inlet and outlet of the microfluidic chip, and using the electrospinning process to directionally stretch the multi-phase fluid to form a composite liquid line containing a multi-chamber core-shell structure; (3) adjusting the process parameters of fluid injection rate, electric field voltage, receiving distance and environmental temperature and humidity to ensure the stable distribution of multiple core phase change materials in the fiber; (4) the composite liquid line is solidified to form a phase change fiber, which is collected by a collection device and subjected to post-processing to obtain a structural stable functional phase change fiber with multiple phase change temperature zones.

[0010] In step (1), the phase change materials are at least two of organic or inorganic phase change materials, and the materials are selected from: p-hydroxybenzoyloxyhexadecyl acetate, p-octadecyl benzoate, paraffin, palmitic acid, decane, pentaerythritol and sodium chloride hydrate.

[0011] The phase change temperature of the phase change material covers multiple temperature zones, including but not limited to 0-10℃, 10-25℃, 25-40℃, 40-60℃ and 60-80℃, and the phase change material covers at least two or more temperature zones.

[0012] The shell layer polymer solution is selected from polyvinyl alcohol (PVA), polylactic acid (PLA), polyacrylonitrile (PAN), polycaprolactone (PCL), chitosan or a blended solution system thereof.

[0013] The multi-channel microfluidic chip comprises at least two multi-axially arranged inner phase flow channels, each of which injects a different kind of phase change material, for constructing a multi-chamber core-shell structure.

[0014] The voltage range in steps (2) and (3) is 10-30 kV, the distance between the collection device and the nozzle is 10-20 cm, and the injection flow rate of the inner phase and the outer phase is controlled between 0.1-1.0 mL / h. The outer phase fluid corresponds to the shell layer, and the inner phase fluid corresponds to the inner core, i.e. the phase change material.

[0015] The collection device is a rotating drum or a flat plate with temperature control function, which is used to guide the directional arrangement and efficient collection of fibers.

[0016] The composite liquid line is solidified by physical solidification or chemical cross-linking before or during collection, and the solidification method includes ultraviolet light curing, thermal curing, solvent evaporation curing or cross-linking agent induced reaction curing, so as to realize the morphology shaping of the composite phase change fiber and the encapsulation and stabilization of the phase change core material; the post-processing process includes vacuum drying, heat setting or surface hydrophobic modification.

[0017] The multi-phase change point composite phase change fiber prepared by the method has a multi-chamber partition structure, and the phase change materials in each chamber are spatially separated.

[0018] The multi-phase change point composite phase change fiber is used in the preparation of intelligent temperature control textiles, flexible thermal management systems or phase change energy storage materials.

[0019] Beneficial effects: 1. The forming efficiency and structural stability are significantly improved: by introducing an adjustable intensity and distribution electric field, the microfluidic interface liquid line is precisely induced and controlled, so that the multi-phase change material and the shell layer solution maintain a stable laminar flow state during the flow process, effectively inhibiting the breakage phenomenon caused by liquid line disturbance, Rayleigh-Taylor instability and capillary fluctuation. This method can significantly improve the continuity and stability of the fiber forming process, reduce the generation rate of broken fibers and defects, and improve the encapsulation integrity and filling density of the phase change material, thereby obtaining composite phase change fibers with high size uniformity and few structural defects.

[0020] 2. Multi-point phase change coordination and spatial precise packaging: The flow and interface position of the multi-channel microfluidic system are accurately controllable, and the synchronous injection and spatial directional arrangement of different phase change temperature materials are realized by combining the electric field regulation, so that the multi-temperature zone segmented packaging structure of the multi-phase change material is formed in a single fiber. The design can realize the continuous phase change heat absorption and release process in a wide temperature range, avoid the problem of narrow temperature control area and discontinuous temperature adjustment of traditional single phase change point material, and greatly improve the thermal management ability and energy utilization efficiency of the fiber.

[0021] 3. Excellent thermal response performance and strong environmental adaptability: The prepared composite phase change fiber has a highly uniform outer diameter and core structure at the microscale, and exhibits multi-temperature zone synchronous or staged response thermal regulation characteristics. The fiber can realize rapid, reversible and sustainable heat regulation according to the change of environmental temperature. The fiber is not only suitable for comfortable temperature control of normal temperature clothing, but also can be applied to protective fabrics and functional equipment in high-altitude low-pressure, desert high-temperature, extremely cold and other extreme environments. At the same time, its weavability and composite property make it have broad industrialization prospects in the fields of intelligent wearable devices, thermal control textiles, energy storage materials and aerospace thermal management. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 is a schematic diagram of the multi-channel microfluidic chip structure used in the embodiment of the present application.

[0023] Figure 2 is a schematic diagram of the multi-channel microfluidic chip structure used in the embodiment of the present application.

[0024] Figure 3 is a schematic diagram of the multi-channel microfluidic chip structure used in the embodiment of the present application.

[0025] Figure 4 is a schematic diagram of the multi-channel microfluidic chip structure used in the embodiment of the present application. Figure 4 (a) is a single phase change point phase change fiber in Example 1, Figure 4 (b) is a double phase change point phase change fiber in Example 2.

[0026] Figure 5 is a DSC curve of the phase change fiber obtained in the embodiment of the present application.

[0027] In the figure, 1 is a glass slide, 2 is a dispensing needle, 3 is an inner core capillary, 4 is a shell capillary, 5 is a metal capillary, 6 is a syringe pump, 7 is a high-voltage power supply, 8 is a collection plate, 9 is a composite phase change fiber, 10 is an inner core, and 11 is a shell. DETAILED DESCRIPTION

[0028] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative effort belong to the scope of protection of the present application.

[0029] To more clearly illustrate the present application, a microfluidic electric field synergistic regulation multiphase transition point composite phase change fiber preparation method is described in detail below in combination with a specific embodiment.

[0030] The present application provides a device for a multiphase transition point composite phase change fiber preparation method, as shown in Figure 1 The device includes: (1) a microfluidic chip: a glass slide 1 is provided with a coaxial nested sleeve structure, three glass capillaries with conical nozzles formed by heat drawing are used as inner phase channels (inner core capillary 3), and a glass capillary with a larger outer diameter is coaxially nested (shell capillary 4), forming a multi-chamber flow channel structure. Each inner phase channel is independent of each other and maintains a gap with the inner wall of the outer tube to ensure the uniform flow and stable coating of the outer shell fluid. In addition, by flexibly configuring the activation mode of the three inner phase channels, phase change fibers with single phase transition point, double phase transition point or triple phase transition point can be generated respectively; (2) a fluid driving unit: the inner phase and the outer phase fluids are respectively driven by a precision syringe pump 6, the flow rate can be independently controlled to ensure the formation of the core-shell composite liquid line; (3) an electric field regulation unit: the outlet end of the microfluidic chip is embedded in a metal capillary 5 as a grounding electrode, and the inlet end is a metal needle (dispensing needle 2) as a high-voltage anode. The two poles are respectively connected to the positive and negative poles of a direct current high-voltage power supply 7, and the voltage range is 0-30 kV, and the electric field strength can be adjusted according to the process requirements; (4) a collection unit: the chip outlet and the grounded collection plate 8 maintain a set distance, the fiber is deposited on the plate surface under the action of the electric field, and the continuous collection of the composite phase change fiber 9 is completed; (5) a post-processing unit: including natural drying and constant temperature drying box heat treatment links, for solvent evaporation, shell layer solidification and structure stability enhancement.

[0031] Example 1: Preparation of a single phase transition point composite phase change fiber (control sample)

[0032] (1) Inner core material: n-tetradecane (C 14 H 30 , melting point about 6 ℃) is selected as the phase change component, 0.5 wt.% non-ionic surfactant Span 80 is added, and stirring is carried out for 30 min in the molten state to obtain a uniform and stable liquid inner core.

[0033] (2) Shell material: Polycaprolactone (PCL), 10 wt.%; Solvent system: dichloromethane (DCM) and dimethylformamide (DMF) mixed solvent, volume ratio 7:3; Magnetic stirring at room temperature for 12 h, forming a transparent and uniform solution.

[0034] (3) Process conditions: (a) Core flow rate: 0.4 mL / h; (b) Shell flow rate: 1.6 mL / h; (c) Chip outlet to collection plate distance: 18 cm; (d) Voltage: 20 kV.

[0035] (4) Post-processing: The obtained fiber was placed at room temperature for 24 h, and then transferred to a 45 °C drying box for 3 h to complete the solidification and reinforcement.

[0036] (5) Test results: (a) Scanning electron microscope (SEM) showed that the fiber surface was smooth, the shell was dense, and the core-shell interface was clear; (b) The differential scanning calorimetry (DSC) curve showed a single melting peak at about 6 °C, and the total melting latent heat was about 108.3 J / g, which represented the thermal response characteristics of single phase change temperature; (c) After 100 thermal cycles, the melting enthalpy retention rate was greater than 90%, the fiber structure was complete, and no obvious leakage was observed.

[0037] Example 2: Preparation of double-phase-change-point composite phase change fiber (preferred scheme)

[0038] Core material:

[0039] (1) Core 1: n-Tetradecane (melting point about 6 °C), adding 0.5 wt.% Span 80;

[0040] (2) Core 2: Paraffin (C16-C20 mixture, melting point about 28-32 °C), adding 0.5 wt.% Span 80; Two kinds of materials were respectively injected into the independent inner phase channels of the microfluidic chip. Shell material: same as Example 1.

[0041] (3) Process conditions: (a) Core 1 flow rate: 0.4 mL / h; (b) Core 2 flow rate: 0.4 mL / h; (c) Shell flow rate: 1.6 mL / h; (d) Chip outlet to collection plate distance: 18 cm; (e) Voltage: 20 kV.

[0042] (4) Post-processing: Same as Example 1.

[0043] (5) Test results: (a) SEM shows that the fiber cross-section has a double-core structure, the core-shell interface is clear, the shell layer is continuous and dense, and there is no obvious crack. (b) The DSC test results show two obvious melting peaks, corresponding to phase transition temperatures of about 6 ℃ and 30 ℃, respectively, and the total melting latent heat is 228.6 J / g, which is significantly higher than that of single-phase samples. (c) The double-peak structure shows that the fiber can play a heat buffering and heat storage role in a wider temperature range. (d) After 100 thermal cycles, the melting enthalpy retention rate is still higher than 90%, showing good thermal cycle stability.

[0044] Comparative analysis:

[0045] From the test data of Example 1 and Example 2, it can be seen that the single-phase transition point fiber only shows phase change heat absorption and release characteristics in the low temperature zone (about 6 ℃), while the double-phase transition point fiber has significant phase change peaks at 6 ℃ and 30 ℃, indicating that it can realize energy storage and release in a wider temperature range. The total latent heat value of the double-phase fiber is significantly higher than that of the single-phase, and the thermal response ability is enhanced; the SEM results show that the double-phase fiber still maintains the complete core-shell structure and does not appear material leakage, verifying the technical effect of the present application of realizing wide temperature range thermal management through multi-phase transition point composite packaging.

[0046] Although embodiments of the present application have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and alterations can be made thereto without departing from the principles and spirit of the present application, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a multi-phase phase change composite phase change fiber, characterized in that, The method comprises the following steps: (1) injecting phase change materials with different phase transition temperatures and shell polymer solutions capable of forming fibers into a multi-channel microfluidic chip to form a laminar flow state of each phase fluid in the chip; (2) applying a high-voltage electrostatic field between the inlet and outlet of the microfluidic chip to directionally stretch the multi-phase fluid by an electrospinning process to form a composite liquid line containing a multi-chamber core-shell structure; (3) adjusting the process parameters of fluid injection rate, electric field voltage, receiving distance, and environmental temperature and humidity to ensure the stable distribution of the multi-core phase change materials in the fiber; (4) solidifying the composite liquid line to form a phase change fiber, collecting the fiber by a collecting device, and performing post-processing to obtain a stable functional phase change fiber with multiple phase transition temperature zones.

2. The method of claim 1, wherein, The phase change materials in step (1) are at least two of organic or inorganic phase change materials selected from the group consisting of p-hydroxybenzoyloxyacetic acid hexadecyl ester, p-octadecyl benzoate, paraffin, palmitic acid, decane, pentaerythritol, and sodium chloride hydrate.

3. The method of claim 1, wherein, The phase change temperatures of the phase change materials cover multiple temperature zones, including but not limited to 0-10℃, 10-25℃, 25-40℃, 40-60℃, and 60-80℃, and the used phase change materials cover at least two or more temperature zones.

4. The method of claim 1, wherein, The shell polymer solution is selected from the group consisting of polyvinyl alcohol (PVA), polylactic acid (PLA), polyacrylonitrile (PAN), polycaprolactone (PCL), chitosan, or a blended solution system thereof.

5. The method of claim 1, wherein, The multi-channel microfluidic chip comprises at least two multi-axis arranged inner phase flow channels, each of which injects a different kind of phase change material for constructing a multi-chamber core-shell structure.

6. The method of claim 1, wherein, The voltage range in steps (2) and (3) is 10-30 kV, the distance between the collecting device and the nozzle is 10-20 cm, and the injection flow rate of the inner phase and the outer phase is controlled between 0.1-1.0 mL / h.

7. The method of claim 1, wherein, The collecting device is a rotating drum or a flat plate with temperature control function for guiding the directional arrangement and efficient collection of fibers.

8. The method of claim 1, wherein, The composite liquid line is solidified by physical solidification or chemical crosslinking before or during collection, and the solidification methods include ultraviolet light curing, thermal curing, solvent evaporation curing, or crosslinking agent induced reaction curing to realize the morphology shaping and phase change core material encapsulation stabilization of the composite phase change fiber; the post-processing process includes vacuum drying, heat setting, or surface hydrophobic modification.

9. The multi-phase phase change composite phase change fiber prepared by the method of any one of claims 1-8, characterized in that, The composite phase change fiber has a multi-chamber partition structure, and the phase change materials in each chamber are spatially separated.

10. The use of the multi-phase transition point composite phase change fiber of claim 9 in the preparation of intelligent temperature control textiles, flexible thermal management systems, or phase change energy storage materials.

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