A flexible porous solid-solid phase change fiber and its preparation method

Abstract

This invention discloses a flexible porous solid-solid phase change fiber and its preparation method. The preparation method combines core-sheath structure encapsulation, chemical crosslinking, and emulsion template pore formation. A reactive phase change emulsion is used as the core spinning solution, and a flexible polymer solution is used as the sheath spinning solution. A nascent fiber with a core-sheath structure is constructed through coaxial wet spinning. The reactive phase change emulsion in the core layer of the nascent fiber is polymerized, and the solvent and pore-forming agent are removed to obtain the flexible porous solid-solid phase change fiber. The flexible polymer in the sheath layer and the solid-solid phase change material in the core layer prevent leakage of the phase change material. The porous structure improves the inherent rigidity and brittleness of the solid-solid phase change material, further enhancing the flexibility of the solid-solid phase change fiber. Therefore, the flexible porous solid-solid phase change fiber prepared by this invention has a high heat capacity, good flexibility at room temperature, high stability, reusability, and no leakage problems.

Description

Technical Field

[0001] This invention relates to the field of phase change fiber technology, specifically to a flexible porous solid-solid phase change fiber and its preparation method. Background Technology

[0002] Phase change fibers are a type of smart wearable thermal management material embedded with phase change materials. They can autonomously sense changes in the external environment and maintain the comfort of the human body's microclimate. They can buffer against sudden changes in ambient temperature, giving the body more time to adapt. The phase change material within the fiber undergoes a change in its phase / crystal structure at a specific temperature or temperature range (phase change temperature), absorbing or releasing a large amount of latent heat of phase change, thereby achieving energy storage and release. They have broad applications in temperature regulation, thermal energy storage, and smart thermal management textiles.

[0003] Currently, the research and preparation of phase change fibers generally utilize solid-liquid and solid-solid phase change materials, with most phase change materials being based on solid-liquid phase change materials. However, liquid flow and leakage in solid-liquid phase change materials can reduce the phase change enthalpy of the fibers and potentially pollute the environment. In recent years, researchers have mainly used methods such as hollow fiber impregnation, coaxial wet spinning, emulsion spinning, and microencapsulation spinning to encapsulate phase change materials to prevent leakage. For example, CN 116856077A describes the preparation of an elastic solid-liquid phase change fiber using an elastic polymer as the sheath spinning solution and an oil-in-oil phase change emulsion as the core spinning solution via coaxial wet spinning. The elastic polymers in both the core and sheath layers can limit the leakage of the liquid phase change material. However, under long-term use or extreme conditions, these solid-liquid phase change materials may still face leakage problems.

[0004] Solid-solid phase change fibers (SSPCs) are increasingly attracting research attention due to their lack of leakage issues. Currently, research on SSPCs is relatively limited. Most SSPC preparations utilize crystalline polymers (such as polyhexadecanyl acrylate, polyethylene glycol, and their derivatives) as phase change materials, obtained through surface modification, in-situ grafting, or grafting followed by spinning. For example, the paper (Gong X, Dang G, Guo J, et al. Sodium alginate / featherkeratin-g-allyloxy polyethylene glycol composite phase change fiber. Int JBiol Macromol, 2019, 131: 192-200) prepared shape-stable SSPCs by grafting sodium alginate with allyl polyethylene glycol followed by wet spinning. Another paper (Bao D, Liu L, Sun T, et al. Solid solid phase change (SSPC) chitosan-g-mPEG fiber with improved mechanical performance via in-situ wet spinning process. Carbohydr) (Polym, 2020, 240:116313) Solid-solid phase change chitosan fibers were prepared by in-situ grafting polyethylene glycol monomethyl ether onto a chitosan backbone using wet spinning and Schiff base reaction. These solid-solid phase change fibers did not exhibit phase separation or leakage during melting and crystallization, but all showed low phase change enthalpies, ranging from only 5.9 to 49.0 J / g.

[0005] Compared to grafting, crosslinking can introduce a large amount of phase change material, thereby increasing the phase change enthalpy of solid-solid phase change fibers. However, the three-dimensional network structure formed by crosslinking usually reduces the flexibility and mechanical properties of the fiber. Therefore, when such solid-solid phase change fibers are subjected to tension, although the flexible outer layer of the fiber does not break, the core solid-solid phase change material is easily broken, forming a bead-like structure, which is not conducive to the practical application of solid-solid phase change fibers. Summary of the Invention

[0006] To address the technical problems of low phase transition enthalpy in existing solid-solid phase change fibers and poor mechanical properties and lack of flexibility in solid-solid phase change fibers prepared by crosslinking methods, the present invention aims to provide a flexible porous solid-solid phase change fiber and its preparation method.

[0007] The above-mentioned objective of the present invention is achieved through the following technical solution:

[0008] A method for preparing flexible porous solid-solid phase change fibers includes the following steps:

[0009] (1) Dissolve the flexible polymer in a solvent to obtain a flexible polymer solution;

[0010] (2) The dispersed phase is added to the continuous phase to obtain a reactive phase change emulsion; the dispersed phase is an oily porogen, which is selected from one or more of n-hexane, cyclohexane, dichloromethane and toluene; the continuous phase is obtained by mixing the reactive phase change material, emulsion stabilizer, initiator and solvent; the reactive phase change material is polyethylene glycol and its derivatives with acrylate groups or methacrylate groups having a molecular weight of 4000 to 20000.

[0011] (3) The flexible polymer solution obtained in step (1) is used as the skin spinning solution and the reactive phase change emulsion obtained in step (2) is used as the core spinning solution for coaxial wet spinning to obtain nascent fibers with a skin-core structure.

[0012] (4) Initiate the polymerization reaction of the reactive phase change material in the nascent fiber obtained in step (3), remove the solvent and oily pore-forming agent, and obtain the flexible porous solid-solid phase change fiber.

[0013] This invention employs a combination of core-sheath encapsulation, chemical crosslinking, and emulsion template pore formation. Based on a crosslinking reaction strategy, it prepares solid-solid phase change materials (SPCs). A reactive SPC emulsion is used as the core spinning solution, and a flexible polymer solution is used as the sheath spinning solution. Primary fibers with a flexible polymer sheath and a reactive SPC emulsion core are constructed through coaxial wet spinning. Further polymerization of the reactive SPC emulsion within the primary fibers is initiated, and solvents and oily pore-forming agents are removed, resulting in flexible solid-solid SPC fibers with a core-sheath structure and a porous structure. The presence of the flexible polymer in the sheath serves two purposes: firstly, it encapsulates the core SPC material to prevent leakage; secondly, it provides good flexibility to the SPC fibers. The core solid-solid SPC material provides a second layer of leakage protection. The porous structure improves the inherent rigidity and brittleness of solid-solid SPCs, further enhancing the flexibility of the solid-solid SPC fibers. Because the core-sheath structure and porous structure provide sufficient crystallization space for the phase change material, the solid-solid phase change fiber prepared by this invention has both excellent flexibility and high phase change enthalpy, and can be reused without leakage problems.

[0014] Further, in step (1), the flexible polymer is a thermoplastic polyurethane elastomer, polyvinylidene fluoride-hexafluoropropylene-tetrafluoroethylene, hydrogenated polystyrene-intercalated-polybutadiene-intercalated-polystyrene, or polyvinyl alcohol.

[0015] Further, in step (1), the content of flexible polymer in the flexible polymer solution is 16wt% to 26wt%.

[0016] Further, in step (1), the solvent is selected from one or more of water, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, methyl ethyl ketone, acetone, tetrahydrofuran, ethyl acetate, dichloromethane, toluene, and methanol.

[0017] Further, in step (2), the volume percentage of the dispersed phase in the reactive phase change emulsion is 10% to 90%, preferably 10% to 50%, and more preferably 30% to 40%.

[0018] Further, in step (2), the reactive phase change material is preferably polyethylene glycol diacrylate and / or polyethylene glycol dimethacrylate.

[0019] Further, in step (2), the molecular weight of the reactive phase change material is preferably 4000-10000, more preferably 8000-10000.

[0020] Furthermore, in step (2), the content of reactive phase change material in the continuous phase is 10wt% to 50wt%.

[0021] Further, in step (2), the emulsion stabilizer is selected from one or more of Pluronic F127, Pluronic F127 diacrylate and Pluronic F127 dimethacrylate; the content of the emulsion stabilizer in the continuous phase is 0.1wt% to 5wt%.

[0022] Further, in step (2), the initiator is selected from one or more of ammonium persulfate, azobisisobutyronitrile, 2-hydroxy-2-methyl-1-phenylpropanone, 1-hydroxycyclohexylphenyl ketone, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, and 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylpropanone; the mass ratio of the initiator to the reactive phase change material is (0.5-4):100.

[0023] Further, in step (2), the solvent is selected from one or more of water, N,N-dimethylformamide, N,N-dimethylacetamide and dimethyl sulfoxide.

[0024] Further, in step (3), the conditions for coaxial wet spinning are: water or ethanol as the coagulation bath, spinning temperature of 20-40°C, and flow rate ratio of the skin spinning solution to the core spinning solution of 1:(0.5-1.5).

[0025] Further, in step (4), the polymerization reaction of the reactive phase change emulsion in the nascent fiber obtained in step (3) is initiated by thermal initiation or photoinitiation. The thermal initiation temperature is 30-80°C and the thermal initiation time is 6-12h. The photoinitiation is carried out by ultraviolet light irradiation. The photoinitiation temperature is 5-40°C and the photoinitiation time is 10-300s, preferably 20-80s, and more preferably 50-70s.

[0026] Furthermore, in step (4), the wavelength of the ultraviolet light is 250–420 nm.

[0027] Furthermore, in step (4), the solvent and oily pore-forming agent are removed by drying treatment. The thermally initiated drying treatment is carried out simultaneously during the initiation process, and the photo-initiated drying treatment is freeze-drying at -80 to -30°C for 24 to 48 hours.

[0028] This invention also protects the flexible porous solid-solid phase change fiber prepared by the above preparation method, wherein the flexible porous solid-solid phase change fiber has a core-shell porous structure, the skin layer is a flexible polymer, and the core layer is a porous solid-solid phase change material.

[0029] The beneficial effects of this invention are:

[0030] This invention employs a combination of core-sheath encapsulation, chemical crosslinking, and emulsion template pore formation. Based on a crosslinking reaction strategy, it prepares solid-solid phase change materials (SPCs). A reactive SPC emulsion is used as the core spinning solution, and a flexible polymer solution is used as the sheath spinning solution. Primary fibers with a flexible polymer sheath and a reactive SPC emulsion core are constructed through coaxial wet spinning. Further polymerization of the reactive SPC emulsion within the primary fibers is initiated, and solvents and oily pore-forming agents are removed, resulting in flexible solid-solid SPC fibers with a core-sheath structure and a porous structure. The presence of the flexible polymer in the sheath serves two purposes: firstly, it encapsulates the core SPC material to prevent leakage; secondly, it provides good flexibility to the SPC fibers. The core solid-solid SPC material provides a second layer of leakage protection. The porous structure improves the inherent rigidity and brittleness of solid-solid SPCs, further enhancing the flexibility of the solid-solid SPC fibers.

[0031] The flexible porous solid-solid phase change fiber prepared by this invention has a high heat capacity (phase change enthalpy of 80-140 J / g), good flexibility at room temperature (it can be easily stretched, woven, bent and knotted, with fracture stress and fracture strain reaching 4.7 MPa and 338.4%, respectively), high stability after 100 heating-cooling cycles and reusability, and no leakage problem. Attached Figure Description

[0032] Figure 1The figures shown are the mechanical property test results of the flexible porous solid-solid phase change fiber prepared in Example 1 of the present invention; wherein, (a) is a tensile diagram, (b) is a weaving diagram, (c) and (d) are knotting diagrams, and (e) is a load-bearing diagram.

[0033] Figure 2 This is a scanning electron microscope image of the flexible porous solid-solid phase change fiber prepared in Example 1 of the present invention.

[0034] Figure 3 This is a tensile test image of the flexible porous solid-solid phase change fiber prepared in Example 1 of the present invention.

[0035] Figure 4 This is a thermogravimetric diagram of the flexible porous solid-solid phase change fiber prepared in Example 1 of the present invention.

[0036] Figure 5 These are heating and cooling exothermic diagrams and heating and cooling exothermic cycle diagrams of the flexible porous solid-solid phase change fiber prepared in Example 1 of this invention.

[0037] Figure 6 The graph shows the test results of the heat storage capacity of the flexible porous solid-solid phase change fibers prepared in Examples 1 to 5 of this invention. Detailed Implementation

[0038] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0039] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0040] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, and the materials and reagents used are commercially available.

[0041] Example 1

[0042] A method for preparing flexible porous solid-solid phase change fibers includes the following steps:

[0043] (1) Dissolve 4g of thermoplastic polyurethane elastomer in 16g of N,N-dimethylformamide and stir magnetically at room temperature for 24h. After mixing evenly, a thermoplastic polyurethane elastomer solution with a content of 20wt% is obtained.

[0044] (2) 5g of polyethylene glycol diacrylate with a molecular weight of 10000, 0.3g of Pluronic F127 diacrylate, 0.2g of 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone and 6.5g of water were stirred for 24h to obtain a continuous phase; 3mL of cyclohexane was added dropwise to 7mL of the above continuous phase and mixed evenly to obtain an oil-in-water reactive phase change emulsion.

[0045] (3) The thermoplastic polyurethane elastomer solution was used as the skin spinning solution and the water-in-oil reactive phase change emulsion was used as the core spinning solution. The solutions were transferred into the syringe and injected into the outer and inner layers of the coaxial spinning needle. Water was used as the coagulation bath and coaxial wet spinning was carried out at room temperature. The flow rate ratio of the skin spinning solution to the core spinning solution was 1:1 to obtain nascent fibers.

[0046] (4) The nascent fiber was placed under ultraviolet light with a wavelength of 365nm at room temperature for 60s to polymerize the reactive phase change material in the core layer. After freeze-drying at -80℃ for 48h, the flexible porous solid-solid phase change fiber was obtained.

[0047] Figure 1 The figures shown are the mechanical property test results of the flexible porous solid-solid phase change fiber prepared in Example 1 of the present invention; wherein, (a) is a tensile diagram, (b) is a weaving diagram, (c) and (d) are knotting diagrams, and (e) is a load-bearing diagram. Figure 1 This indicates that the prepared flexible porous solid-solid phase change fiber possesses good flexibility and can be easily stretched, woven, bent, and knotted. Furthermore, 1g of flexible porous solid-solid phase change fiber can withstand a weight of 200g without breaking.

[0048] Figure 2 This is a scanning electron microscope (SEM) image of the flexible porous solid-solid phase change fiber prepared in Example 1 of this invention. Figure 2 As can be seen, the cross-section of the flexible porous solid-solid phase change fiber exhibits obvious core-skin separation. The skin layer has a porous structure extending from the inner and outer surfaces towards the center, while the inner and outer walls are relatively smooth. The core layer size is significantly smaller than the diameter of the coaxial needle core layer. This is mainly because the core layer forms a hydrogel after cross-linking polymerization and undergoes significant shrinkage after freeze-drying, thus separating from the skin layer. With the addition of a porogen, a microporous structure appears in the fiber core layer. This is attributed to the emulsion template porogen effect: the porogen acts as a dispersed phase uniformly dispersed within the emulsion, forming an ice crystal template at low temperatures and sublimating during drying, thereby forming the porous structure of the fiber core layer.

[0049] Figure 3This is a tensile test image of the flexible porous solid-solid phase change fiber prepared in Example 1 of this invention. Since the initial modulus of the core layer is much higher than that of the sheath layer, the tensile properties of this flexible porous solid-solid phase change fiber mainly depend on the core layer. It exhibits two fractures during the tensile process, corresponding to the fractures of the sheath layer and the core layer, respectively. It can be seen that its fracture stress and fracture strain reach 4.7 MPa and 338.4%, respectively.

[0050] Figure 4 This is a thermogravimetric curve of the flexible porous solid-solid phase change fiber prepared in Example 1 of this invention. The thermogravimetric curve of the flexible porous solid-solid phase change fiber shows two weight loss stages, and its thermogravimetric temperature is significantly higher than the melting temperature of the core phase change material, indicating that it has thermal stability during the heat absorption and release process.

[0051] Figure 5 The diagrams show the heating and cooling exothermic curves and the heating and cooling exothermic cycle diagrams of the flexible porous solid-solid phase change fiber prepared in Example 1 of this invention. After 10, 20, 50, and 100 cycles of heat absorption and exothermic reaction, the phase change enthalpy of the flexible porous solid-solid phase change fiber does not change significantly, indicating that it has good reusability.

[0052] Example 2

[0053] A method for preparing a flexible porous solid-solid phase change fiber is basically the same as the preparation method in Example 1, except that in step (2), 1 mL of cyclohexane is added dropwise to 9 mL of the above continuous phase and mixed evenly to obtain an oil-in-water reactive phase change emulsion.

[0054] Example 3

[0055] A method for preparing a flexible porous solid-solid phase change fiber is basically the same as the preparation method in Example 1, except that in step (2), 2 mL of cyclohexane is added dropwise to 8 mL of the above continuous phase and mixed evenly to obtain an oil-in-water reactive phase change emulsion.

[0056] Example 4

[0057] A method for preparing a flexible porous solid-solid phase change fiber is basically the same as the preparation method in Example 1, except that in step (2), 4 mL of cyclohexane is added dropwise to 6 mL of the above continuous phase and mixed evenly to obtain an oil-in-water reactive phase change emulsion.

[0058] Example 5

[0059] A method for preparing a flexible porous solid-solid phase change fiber is basically the same as the preparation method in Example 1, except that in step (2), 5 mL of cyclohexane is added dropwise to 5 mL of the above continuous phase and mixed evenly to obtain an oil-in-water reactive phase change emulsion.

[0060] Figure 6 The graph shows the test results of the heat storage capacity of the flexible porous solid-solid phase change fibers prepared in Examples 1 to 5 of this invention.

[0061] Example 6

[0062] A method for preparing flexible porous solid-solid phase change fibers includes the following steps:

[0063] (1) Dissolve 4g of thermoplastic polyurethane elastomer in 16g of N,N-dimethylformamide and stir magnetically at room temperature for 24h. After mixing evenly, a thermoplastic polyurethane elastomer solution with a content of 20wt% is obtained.

[0064] (2) 5g of polyethylene glycol diacrylate with a molecular weight of 8000, 0.3g of Pluronic F127 diacrylate, 0.2g of 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone and 6.5g of water were stirred for 24h to obtain a continuous phase; 3mL of cyclohexane was added dropwise to 7mL of the above continuous phase and mixed evenly to obtain an oil-in-water reactive phase change emulsion.

[0065] (3) The thermoplastic polyurethane elastomer solution was used as the skin spinning solution and the water-in-oil reactive phase change emulsion was used as the core spinning solution. The solutions were transferred into the syringe and injected into the outer and inner layers of the coaxial spinning needle. Water was used as the coagulation bath and coaxial wet spinning was carried out at room temperature. The flow rate ratio of the skin spinning solution to the core spinning solution was 1:1 to obtain nascent fibers.

[0066] (4) The nascent fiber was placed under ultraviolet light with a wavelength of 365nm at room temperature for 30s to polymerize the reactive phase change material in the core layer. After freeze-drying at -30℃ for 48h, the flexible porous solid-solid phase change fiber was obtained.

[0067] Example 7

[0068] A method for preparing a flexible porous solid-solid phase change fiber is basically the same as the preparation method in Example 6, except that in step (2), the molecular weight of polyethylene glycol diacrylate is 6000.

[0069] Example 8

[0070] A method for preparing a flexible porous solid-solid phase change fiber is basically the same as the preparation method in Example 6, except that in step (2), the molecular weight of polyethylene glycol diacrylate is 4000.

[0071] Example 9

[0072] A method for preparing flexible porous solid-solid phase change fibers includes the following steps:

[0073] (1) Dissolve 4g of thermoplastic polyurethane elastomer in 16g of N,N-dimethylformamide and stir magnetically at room temperature for 24h. After mixing evenly, a thermoplastic polyurethane elastomer solution with a content of 20wt% is obtained.

[0074] (2) 5g of polyethylene glycol diacrylate with a molecular weight of 20000, 0.3g of Pluronic F127 diacrylate, 0.2g of 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone and 6.5g of water were stirred for 24h to obtain a continuous phase; 3mL of cyclohexane was added dropwise to 7mL of the above continuous phase and mixed evenly to obtain an oil-in-water reactive phase change emulsion.

[0075] (3) The thermoplastic polyurethane elastomer solution was used as the skin spinning solution and the water-in-oil reactive phase change emulsion was used as the core spinning solution. The solutions were transferred into the syringe and injected into the outer and inner layers of the coaxial spinning needle. Water was used as the coagulation bath and coaxial wet spinning was carried out at room temperature. The flow rate ratio of the skin spinning solution to the core spinning solution was 1:1 to obtain nascent fibers.

[0076] (4) The nascent fiber was placed under ultraviolet light with a wavelength of 365nm at room temperature for 300s to polymerize the reactive phase change material in the core layer. After freeze-drying at -80℃ for 48h, the flexible porous solid-solid phase change fiber was obtained.

[0077] Example 10

[0078] A method for preparing flexible porous solid-solid phase change fibers includes the following steps:

[0079] (1) Dissolve 4g of thermoplastic polyurethane elastomer in 16g of N,N-dimethylformamide and stir magnetically at room temperature for 24h. After mixing evenly, a thermoplastic polyurethane elastomer solution with a content of 20wt% is obtained.

[0080] (2) 5g of polyethylene glycol diacrylate with a molecular weight of 10000, 0.3g of Prönnick F127 diacrylate, 0.05g of ammonium persulfate and 6.65g of N,N-dimethylformamide were stirred for 24h to obtain a continuous phase; 3mL of n-hexane was added dropwise to 7mL of the above continuous phase and mixed evenly to obtain an oil-in-oil reactive phase change emulsion.

[0081] (3) The thermoplastic polyurethane elastomer solution was used as the skin spinning solution and the oil-in-oil reactive phase change emulsion was used as the core spinning solution. The solutions were transferred into the syringe and injected into the outer and inner layers of the coaxial spinning needle. Water was used as the coagulation bath and coaxial wet spinning was carried out at room temperature. The flow rate ratio of the skin spinning solution to the core spinning solution was 1:1 to obtain nascent fibers.

[0082] (4) The nascent fiber is placed at room temperature and 70°C to allow the core reactive phase change material to undergo a polymerization reaction and then dried for 12 hours to obtain the flexible porous solid-solid phase change fiber.

[0083] Example 11

[0084] A method for preparing flexible porous solid-solid phase change fibers includes the following steps:

[0085] (1) Dissolve 4g of polyvinylidene fluoride-hexafluoropropylene-tetrafluoroethylene in 16g of N,N-dimethylformamide and stir magnetically at room temperature for 24h. After mixing evenly, a polyvinylidene fluoride-hexafluoropropylene-tetrafluoroethylene solution with a content of 20wt% is obtained.

[0086] (2) 5g of polyethylene glycol dimethacrylate with a molecular weight of 10000, 0.3g of Pluronic F127 dimethacrylate, 0.2g of 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone and 6.5g of water were stirred for 24h to obtain a continuous phase; 3mL of n-hexane was added dropwise to 7mL of the above continuous phase and mixed evenly to obtain an oil-in-water reactive phase change emulsion.

[0087] (3) Polyvinylidene fluoride-hexafluoropropylene-tetrafluoroethylene solution was used as the skin spinning solution and oil-in-water reactive phase change emulsion was used as the core spinning solution. The solutions were transferred into a syringe and injected into the outer and inner layers of the coaxial spinning needle. Water was used as the coagulation bath and coaxial wet spinning was carried out at room temperature. The flow rate ratio of the skin spinning solution to the core spinning solution was 1:1 to obtain nascent fibers.

[0088] (4) The nascent fiber was placed under ultraviolet light with a wavelength of 365nm at room temperature for 60s to polymerize the reactive phase change material in the core layer. After freeze-drying at -80℃ for 48h, the flexible porous solid-solid phase change fiber was obtained.

[0089] Example 12

[0090] A method for preparing flexible porous solid-solid phase change fibers includes the following steps:

[0091] (1) Dissolve 4g of hydrogenated polystyrene-intercalated polybutadiene-intercalated polystyrene in 16g of N,N-dimethylformamide and stir magnetically for 24h at room temperature. After mixing evenly, a hydrogenated polystyrene-intercalated polybutadiene-intercalated polystyrene solution with a content of 20wt% is obtained.

[0092] (2) 5g of polyethylene glycol dimethacrylate with a molecular weight of 10000, 0.3g of Pluronic F127 dimethacrylate, 0.2g of 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone and 6.5g of water were stirred for 24h to obtain a continuous phase; 3mL of n-hexane was added dropwise to 7mL of the above continuous phase and mixed evenly to obtain an oil-in-water reactive phase change emulsion.

[0093] (3) Hydrogenated polystyrene-intercalated polybutadiene-intercalated polystyrene solution was used as the skin spinning solution and water-in-oil reactive phase change emulsion was used as the core spinning solution. The solutions were transferred into the syringe and injected into the outer and inner layers of the coaxial spinning needle. Water was used as the coagulation bath and coaxial wet spinning was carried out at room temperature. The flow rate ratio of the skin spinning solution to the core spinning solution was 1:1 to obtain nascent fibers.

[0094] (4) The nascent fiber was placed under ultraviolet light with a wavelength of 365nm at room temperature for 60s to polymerize the reactive phase change material in the core layer. After freeze-drying at -80℃ for 48h, the flexible porous solid-solid phase change fiber was obtained.

[0095] Example 13

[0096] A method for preparing flexible porous solid-solid phase change fibers includes the following steps:

[0097] (1) Dissolve 4g of polyvinyl alcohol in 16g of water and stir magnetically at room temperature for 24h. After mixing evenly, a polyvinyl alcohol solution with a content of 20wt% is obtained.

[0098] (2) 5g of polyethylene glycol dimethacrylate with a molecular weight of 10000, 0.3g of Pluronic F127 dimethacrylate, 0.2g of 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone and 6.5g of water were stirred for 24h to obtain a continuous phase; 3mL of n-hexane was added dropwise to 7mL of the above continuous phase and mixed evenly to obtain an oil-in-water reactive phase change emulsion.

[0099] (3) Polyvinyl alcohol solution was used as the skin spinning solution and oil-in-water reactive phase change emulsion was used as the core spinning solution. The solutions were transferred into a syringe and injected into the outer and inner layers of the coaxial spinning needle. Water was used as the coagulation bath and coaxial wet spinning was carried out at room temperature. The flow rate ratio of the skin spinning solution to the core spinning solution was 1:1 to obtain nascent fibers.

[0100] (4) The nascent fiber was placed under ultraviolet light with a wavelength of 365nm at room temperature for 60s to polymerize the reactive phase change material in the core layer. After freeze-drying at -80℃ for 48h, the flexible porous solid-solid phase change fiber was obtained.

[0101] Comparative Example 1

[0102] A method for preparing a solid-solid phase change fiber is basically the same as the preparation method in Example 1, except that in step (2), cyclohexane is replaced with paraffin.

[0103] The solid-solid phase change fiber prepared in Comparative Example 1 had a paraffin removal rate of only about 50%, and the porous structure of the solid-solid phase change fiber core was uneven.

[0104] Comparative Example 2

[0105] A method for preparing a solid-solid phase change fiber is basically the same as the preparation method in Example 1, except that in step (2), the molecular weight of polyethylene glycol diacrylate is 1000.

[0106] Because polyethylene glycol diacrylate has a low molecular weight, the resulting solid-solid phase change fiber has a low phase change enthalpy, and the fiber is relatively brittle and hard, with poor fiber flexibility and mechanical properties.

[0107] Comparative Example 3

[0108] A method for preparing a solid-solid phase change fiber is basically the same as the preparation method in Example 1, except that in step (2), the molecular weight of polyethylene glycol diacrylate is 100,000.

[0109] Because the molecular weight of polyethylene glycol diacrylate is too high, it is insufficient to support the porous structure, resulting in poor flexibility and mechanical properties of the solid-solid phase change fiber.

[0110] Test case

[0111] The heat storage capacity of the flexible porous solid-solid phase change fibers prepared in Examples 1-13 and the solid-solid phase change fibers prepared in Comparative Examples 1-3 was tested using differential scanning calorimetry. The test results are shown in Table 1.

[0112] Table 1

[0113]

[0114]

[0115] In Example 1, the volume percentage of the dispersed phase to the reactive phase change emulsion was 30%. Compared to Example 1, the volume percentages of the dispersed phase to the reactive phase change emulsion in Examples 2, 3, 4, and 5 were 10%, 20%, 40%, and 50%, respectively. With increasing content of the oily porogen dispersed phase, the enthalpy of phase change in the flexible porous solid-solid phase change fiber showed a trend of first increasing and then decreasing. This is because the increased porogen content leads to an increase in the number of micropores in the core layer, providing sufficient crystallization space, and thus increasing the enthalpy of phase change. Example 1, with a core layer dispersed phase content of 30%, had the highest enthalpy of phase change at 141.7 J / g. As the dispersed phase content further increased, the content of phase change material in the fiber became too low, and the enthalpy of phase change began to decrease. It can be seen that appropriately increasing the dispersed phase content can construct a porous structure in the fiber core layer, providing sufficient crystallization space for the phase change material, thereby improving the heat storage capacity of the phase change fiber.

[0116] In Example 1, the molecular weight of the reactive phase change material was 10,000. Compared to Example 1, the molecular weights of the reactive phase change materials in Examples 6, 7, 8, and 9 were 8,000, 6,000, 4,000, and 20,000, respectively. As the molecular weight of the reactive phase change material increased, the phase transition temperature and enthalpy of the flexible porous solid-solid phase change fiber gradually increased. This is because the length of the molecular chain of the reactive phase change material determines its crystallinity, thus further affecting the phase transition temperature and enthalpy. However, when the molecular weight of the reactive phase change material increased to 20,000, the crystallinity decreased due to the excessively long molecular chain, and the enthalpy of the phase transition of the flexible porous solid-solid phase change fiber began to decrease. It can be seen that by controlling the molecular weight of the reactive phase change material, solid-solid phase change fibers with different phase transition temperature requirements can be prepared.

[0117] The above embodiments demonstrate that the flexible porous solid-solid phase change fiber prepared by this invention possesses excellent flexibility, allowing it to be bent, knotted, and woven; it can achieve bidirectional temperature regulation within a certain temperature range, with an absorption / release heat density reaching 141.7 J / g; and it can repeatedly absorb and release heat over a hundred times while maintaining a essentially unchanged heat density. This flexible porous solid-solid phase change fiber has broad applications in temperature regulation, thermal energy storage, and intelligent thermal management textiles.

[0118] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art should understand that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing flexible porous solid-solid phase change fibers, characterized in that, Includes the following steps: (1) Dissolve the flexible polymer in a solvent to obtain a flexible polymer solution; (2) The dispersed phase is added to the continuous phase to obtain a reactive phase change emulsion; the dispersed phase is an oily porogen selected from one or more of n-hexane, cyclohexane, dichloromethane and toluene; the continuous phase is obtained by mixing the reactive phase change material, emulsion stabilizer, initiator and solvent; the reactive phase change material is polyethylene glycol with acrylate groups or methacrylate groups and a molecular weight of 4000~20000; the volume percentage of the dispersed phase in the reactive phase change emulsion is 10%~50%; the content of the reactive phase change material in the continuous phase is 10wt%~50wt%. (3) Using the flexible polymer solution obtained in step (1) as the skin spinning solution and the reactive phase change emulsion obtained in step (2) as the core spinning solution, coaxial wet spinning is performed to obtain nascent fibers with a skin-core structure. (4) Initiate the polymerization reaction of the reactive phase change material in the nascent fiber obtained in step (3), remove the solvent and oily pore-forming agent, and obtain the flexible porous solid-solid phase change fiber.

2. The preparation method according to claim 1, characterized in that, In step (1), the flexible polymer is thermoplastic polyurethane elastomer, polyvinylidene fluoride-hexafluoropropylene-tetrafluoroethylene, hydrogenated polystyrene-intercalated-polybutadiene-intercalated-polystyrene, or polyvinyl alcohol.

3. The preparation method according to claim 1, characterized in that, In step (1), the content of flexible polymer in the flexible polymer solution is 16wt%~26wt%.

4. The preparation method according to claim 1, characterized in that, In step (2), the emulsion stabilizer is selected from one or more of Pluronic F127, Pluronic F127 diacrylate and Pluronic F127 dimethacrylate; the content of the emulsion stabilizer in the continuous phase is 0.1wt%~5wt%.

5. The preparation method according to claim 1, characterized in that, In step (2), the initiator is selected from one or more of ammonium persulfate, azobisisobutyronitrile, 2-hydroxy-2-methyl-1-phenylpropanone, 1-hydroxycyclohexylphenyl ketone, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide and 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylpropanone; the mass ratio of the initiator to the reactive phase change material is (0.5~4):

100.

6. The preparation method according to claim 1, characterized in that, In step (3), the conditions for coaxial wet spinning are: water or ethanol as the coagulation bath, spinning temperature of 20~40 ℃, and flow rate ratio of the skin spinning solution to the core spinning solution of 1:(0.5~1.5).

7. The preparation method according to claim 1, characterized in that, In step (4), the polymerization reaction of the reactive phase change emulsion in the nascent fiber obtained in step (3) is initiated by thermal initiation or photoinitiation. The temperature of thermal initiation is 30~80 ℃; the temperature of photoinitiation is 5~40 ℃.

8. Flexible porous solid-solid phase change fiber obtained by the preparation method according to any one of claims 1 to 7.

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