Nanocellulose-based self-fusion photothermal phase change composite fiber and preparation method and application thereof

Abstract

This invention discloses a nanocellulose-based self-fusion photothermal phase change composite fiber, its preparation method, and its applications. The method includes: preparing a nanocellulose-based spinning solution; dispersing photothermal materials and phase change materials to prepare an inner and outer axial spinning solution; and coaxial wet spinning and collection. Nanocellulose, as the matrix for dispersing photothermal materials and phase change materials, effectively improves the spinnability of the spinning solution and simplifies the composite fiber preparation process. Specifically, during spinning, the nanocellulose in the inner and outer axes entangles and self-fused to form an integrated layered structure. The photothermal materials and phase change materials are distributed in the fiber shell and core, respectively, allowing for synergistic functional properties. The composite fiber prepared by this invention has advantages such as high phase change material content, high photothermal conversion efficiency, good mechanical properties, and good leak-proof performance. Compared to synthetic polymers, nanocellulose has biocompatibility and biodegradability, therefore, this fiber has broad application prospects in personal thermal management, smart textiles, and other fields.

Description

Technical Field

[0001] This invention belongs to the field of functional fiber technology, and particularly relates to a nanocellulose-based self-fusion photothermal phase change composite fiber, its preparation method and application. Background Technology

[0002] Against the backdrop of the global energy crisis and environmental pollution, solar energy, as one of the oldest and most abundant clean and renewable energy sources, is receiving increasing research attention. With the development of energy and materials science, combining photothermal conversion and phase change material energy storage technologies offers a solution for the effective collection and storage of solar energy. To achieve this technological goal, functional composite materials are often required, and one-dimensional fiber materials, with their unique flexibility and weavability, can be applied to many cutting-edge fields such as personal thermal management and smart textiles.

[0003] Introducing phase change materials (PCMs) into the fiber matrix is ​​a direct way to endow fibers with energy storage capabilities. Existing methods mainly include: first encapsulating PCMs in microcapsules and then blending and spinning them; or spinning fibers first and then filling or impregnating them with PCMs. However, these methods require two intermittent operations, are cumbersome, and result in uneven distribution of PCMs within the fibers. During the material's service life, molten PCMs are prone to leaking from the fiber surface. To overcome these problems, novel coaxial spinning technology uses PCMs as an inner axial fluid, directly encapsulating them within the fiber's outer axial structure. However, to ensure the continuity and morphological regularity of the fiber encapsulation, synthetic polymers are generally used as the fiber's outer axial support and encapsulation, which exacerbates the consumption of fossil resources and is detrimental to sustainable development. Furthermore, to improve the photothermal conversion efficiency of PCM fibers, photothermal materials need to be introduced into the fiber matrix. However, photothermal materials are mostly inorganic nanoparticles, which have poor compatibility with general polymer substrates and are difficult to disperse, hindering the full utilization of their photothermal properties in composite materials. On the other hand, phase change materials themselves lack mechanical strength, and when used directly as the inner axis of a fiber, there is a lack of effective interfacial bonding between them and the outer axis material (usually a polymer). Therefore, the coaxial phase change fibers currently under research have poor mechanical properties and low tensile strength, which is not conducive to subsequent processing and widespread application.

[0004] Compared to synthetic polymers, nanocellulose originates from the Earth's most abundant and renewable biomass resources. Through wet spinning technology, it can be assembled from the bottom up into macroscopic fibers with specific multi-level structures and excellent mechanical properties. Furthermore, thanks to its chemical composition and surface group distribution, nanocellulose can not only assist in the stable dispersion of various inorganic nanoparticles in water, but also act as a Pickering emulsifier to stabilize paraffin-based phase change materials. Therefore, using nanocellulose as a fiber matrix to replace synthetic polymers holds promise for developing high-performance and environmentally friendly photothermal phase change composite fibers. Summary of the Invention

[0005] To address the problems in current research, this invention provides a nanocellulose-based self-fusion photothermal phase change composite fiber, its preparation method, and its application.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] In a first aspect, the present invention provides a method for preparing nanocellulose-based self-fusion photothermal phase change composite fibers, comprising the following steps:

[0008] (1) Plant fiber raw materials or industrial pulp are chemically pretreated and mechanically fibrillated to obtain a nanocellulose aqueous dispersion with a concentration of 0.2-10 wt%; 10,000 parts by weight of nanocellulose aqueous dispersion and 0-10,000 parts by weight of high molecular weight polysaccharide solution with a concentration of 1-20 wt% are mixed to obtain nanocellulose-based spinning solution.

[0009] (2) Add 1 to 100 parts by weight of photothermal material to 10,000 parts by weight of the nanocellulose-based spinning solution prepared in step (1), and obtain an outer shaft spinning solution by shearing.

[0010] (3) Add 100-2000 parts by weight of the melted phase change material and 0-100 parts by weight of the surfactant to 10000 parts by weight of the nanocellulose-based spinning solution prepared in step (1), and obtain the inner shaft spinning solution by emulsification.

[0011] (4) The outer shaft spinning solution prepared in step (2) and the inner shaft spinning solution prepared in step (3) are degassed. The degassed outer shaft spinning solution is injected into the outer shaft of the coaxial needle, and the degassed inner shaft spinning solution is injected into the inner shaft of the coaxial needle. At the same time, the spinneret is extruded into the coagulation bath at a spinneret speed of 0.02 to 2 m / s. The spinneret is allowed to stand for 1 to 20 minutes to form nascent fibers. The fibers are collected by a winding device and dried to obtain nanocellulose-based self-fusion photothermal phase change composite fibers.

[0012] Further, the polymeric polysaccharide solution is a solution of carboxymethyl cellulose, hydroxypropyl cellulose, cellulose acetate, cellulose xanthate, cellulose phosphate, cellulose quaternary ammonium salt, dextran, chitosan, cyclodextrin, starch, sodium alginate, pectin, hemicellulose, or hyaluronic acid.

[0013] Further, the polymeric polysaccharide solution is a solution of carboxymethyl cellulose, hydroxypropyl cellulose, cellulose acetate, cellulose xanthate, cellulose phosphate, cellulose quaternary ammonium salt, dextran, chitosan, cyclodextrin, starch, sodium alginate, pectin, hemicellulose, or hyaluronic acid.

[0014] Furthermore, the phase change material is polyethylene glycol, paraffin, or C. 14 ~C 28A mixture of one or more of aliphatic alkanes, fatty acids, and fatty alcohols in any proportion.

[0015] Furthermore, the shearing process is performed by using a mixer, cell disruptor, homogenizer, ultrasonic machine, or cell disruptor for 1 to 30 minutes.

[0016] Furthermore, the emulsification process involves treating the cells with a homogenizer, sonicator, or cell disruptor for 1–30 minutes until an emulsion system is formed.

[0017] Furthermore, the coagulation bath is one or more of methanol, ethanol, acetone, ethylene glycol, isopropanol, propylene glycol, and their aqueous solutions in any proportion, and the concentration of the aqueous solution is not less than 60 vol.

[0018] Furthermore, the drying method is room temperature drying, infrared lamp drying, high temperature drying, or microwave drying.

[0019] Secondly, this method provides a nanocellulose-based self-fusion photothermal phase change composite fiber, which includes an inner layer and an outer layer; the inner layer is a porous network structure formed by nanocellulose, and the pores of the porous network structure are filled with phase change material; the outer layer is a dense shell formed by nanocellulose, and photothermal material is embedded therein; the substrate supporting and connecting the inner and outer layers is nanocellulose.

[0020] Thirdly, the present invention provides an application of nanocellulose-based self-fusion photothermal phase change composite fiber in wearable devices, medical devices, electronic product packaging, or building thermal management.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows: by using nanocellulose as the matrix to disperse photothermal materials and phase change materials separately, and preparing external and internal axial spinning solutions, it is possible to first ensure that the functional components are uniformly dispersed in advance, and then continuously prepare composite fibers with unique layered structures through coaxial spinning technology; in the internal axial spinning solution, the phase change material is wrapped in the nanocellulose network in the form of emulsion particles, which restricts its sedimentation or aggregation, and after spinning extrusion and drying, the nanocellulose wrapped with the phase change material directly forms a porous network structure with the emulsion as a template, and the phase change material fills its pores as a dispersed phase; in the external axial spinning solution, the nanocellulose is sheared by the needle wall and oriented to form a dense cellulose shell, in which photothermal materials are embedded; the high aspect ratio nanocellulose serves as the common substrate for the inner and outer layers of the fiber, and the mutual entanglement plays a role in supporting and connecting the inner and outer layers. This structural design not only successfully integrates photothermal and phase change functions onto a single fiber, but also promotes the synergistic effect of these functions. The outer layer of the fiber provides excellent mechanical properties and, together with the porous network in the inner layer, provides a double leak-proof encapsulation of the phase change material. The photothermal material distributed in the outer layer effectively absorbs external light, while the tight entanglement of nanocellulose between the inner and outer layers ensures that the heat converted by the outer photothermal layer can be rapidly conducted to the inner phase change material. Finally, this preparation method is not only simple in process but also does not involve corrosive organic solvents and does not require the introduction of other encapsulation materials to encapsulate the phase change material, making it more environmentally friendly. Attached Figure Description

[0022] Figure 1 The graph shows the temperature change curves of plain cloth and commercial black cotton cloth woven from the nanocellulose-based self-fusion photothermal phase change composite fiber prepared in Example 1 under simulated sunlight irradiation.

[0023] Figure 2 A scanning electron microscope image of the cross-sectional structure of the nanocellulose-based self-fused photothermal phase change composite fiber prepared in Example 1;

[0024] Figure 3 This is a diagram illustrating the nanocellulose-based self-fused photothermal phase change composite fiber prepared in Example 1. Figure 3 (a) is a diagram illustrating the coiling, twisting, and knotting of the nanocellulose-based self-fusion photothermal phase change composite fiber prepared in Example 1. Figure 3 (b) is a diagram showing the plain cloth obtained by weaving the nanocellulose-based self-fusion photothermal phase change composite fiber prepared in Example 1;

[0025] Figure 4 The graph shows the recorded curves obtained by differential scanning calorimetry (DSC) at different cycle numbers for the nanocellulose-based self-fused photothermal phase change composite fiber prepared in Example 1. Figure 4(a) is a graph showing the recorded number of iterations for the first iteration. Figure 4 (b) is a graph showing the record at the 50th iteration. Figure 4 (c) is a graph showing the record at the 100th iteration. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without inventive effort are within the scope of protection of this invention.

[0027] Unless otherwise specified, the experimental methods described in the following examples are conventional methods; the reagents and materials described are commercially available unless otherwise specified.

[0028] This invention provides a nanocellulose-based self-fusion photothermal phase change composite fiber. Nanocellulose replaces traditional polymers as the fiber matrix and serves as the dispersion matrix for both photothermal and phase change materials. The composite fiber is prepared by coaxial wet spinning, with the inner layer loaded with phase change material and the outer layer loaded with photothermal material, thus giving it excellent mechanical properties, photothermal conversion performance, heat storage performance, and encapsulation performance.

[0029] In a first aspect, the present invention provides a method for preparing nanocellulose-based self-fusion photothermal phase change composite fibers, comprising the following steps:

[0030] (1) A nanocellulose aqueous dispersion with a concentration of 0.2 to 10 wt% is obtained by chemical pretreatment and mechanical fibrillation of plant fiber raw materials or industrial pulp; 10,000 parts by weight of nanocellulose aqueous dispersion and 0 to 10,000 parts by weight of high molecular weight polysaccharide solution with a concentration of 1 to 20 wt% are mixed to obtain nanocellulose-based spinning solution.

[0031] The high molecular weight polysaccharide solution is a solution of carboxymethyl cellulose, hydroxypropyl cellulose, cellulose acetate, cellulose xanthate, cellulose phosphate, cellulose quaternary ammonium salt, dextran, chitosan, cyclodextrin, starch, sodium alginate, pectin, hemicellulose, or hyaluronic acid.

[0032] In a preferred embodiment of the present invention, the concentration of the nanocellulose aqueous dispersion is 0.4–1.0 wt%.

[0033] (2) Add 1 to 100 parts by weight of photothermal material to 10,000 parts by weight of the nanocellulose-based spinning solution prepared in step (1), and obtain an outer shaft spinning solution by shearing.

[0034] The photothermal material is polydopamine, polypyrrole, gold nanoparticles, silver nanoparticles, aluminum nanoparticles, MXene, carbon black, graphite, graphene oxide, carbon nanotubes, molybdenum disulfide, black phosphorus, boronene, iron oxide, iron tetroxide, titanium dioxide, titanium trioxide, or cesium tungsten oxide.

[0035] The shearing process is performed by using a mixer, cell disruptor, homogenizer, ultrasonic machine, or cell disruptor for 1 to 30 minutes.

[0036] (3) Add 100-2000 parts by weight of the melted phase change material and 0-100 parts by weight of the surfactant to 10000 parts by weight of the nanocellulose-based spinning solution prepared in step (1), and obtain the inner shaft spinning solution by emulsification.

[0037] The phase change material is polyethylene glycol, paraffin, and C. 14 ~C 28 It is a mixture of one or more aliphatic alkanes, fatty acids, and fatty alcohols in any proportion; depending on the needs of a specific application scenario, phase change materials with specific phase change temperatures can be selectively used.

[0038] The surfactant is sodium dodecyl sulfate, sodium dodecylbenzene sulfate, hexadecyltrimethylammonium bromide, or alkylphenol polyoxyethylene ether.

[0039] The emulsification process involves treating the cells with a homogenizer, sonicator, or cell disruptor for 1–30 minutes until an emulsion system is formed.

[0040] (4) The outer shaft spinning solution prepared in step (2) and the inner shaft spinning solution prepared in step (3) are degassed. The degassed outer shaft spinning solution is injected into the outer shaft of the coaxial needle, and the degassed inner shaft spinning solution is injected into the inner shaft of the coaxial needle. At the same time, the spinneret is extruded into the coagulation bath at a spinneret speed of 0.02 to 2 m / s. The spinneret is allowed to stand for 1 to 20 minutes to form nascent fibers. The fibers are collected by a winding device and dried to obtain nanocellulose-based self-fusion photothermal phase change composite fibers.

[0041] The coagulation bath is one or more of methanol, ethanol, acetone, ethylene glycol, isopropanol, propylene glycol, and their aqueous solutions in any proportion, and the concentration of the aqueous solution is not less than 60 vol.

[0042] The drying method is room temperature drying, infrared lamp drying, high temperature drying, or microwave drying.

[0043] In a specific embodiment of the present invention, the nascent fibers after wet spinning can form a porous network structure by direct drying, without the need for freeze drying or other methods.

[0044] In specific embodiments of the present invention, the plant fiber raw materials include, but are not limited to, coniferous wood, broadleaf wood, straw, potatoes, rice straw, beetroot, or bamboo. The industrial pulp includes, but is not limited to, wood pulp, bamboo pulp, or bamboo pulp.

[0045] In specific embodiments of the present invention, the equipment used for the mechanical fibrillation of plant fibers includes, but is not limited to, a high-pressure homogenizer, a grinder, or a mixer.

[0046] In specific embodiments of the present invention, the means of chemical pretreatment of plant fibers include, but are not limited to, peroxyacid treatment, TEMPO oxidation treatment, esterification treatment, carboxymethylation treatment, or quaternization treatment.

[0047] The present invention also provides a nanocellulose-based self-fusion photothermal phase change composite fiber prepared by the above preparation method, wherein the nanocellulose-based self-fusion photothermal phase change composite fiber comprises an inner layer and an outer layer; the inner layer is a porous network structure formed by nanocellulose, and the pores of the porous network structure are filled with phase change material; the outer layer is a dense shell formed by nanocellulose, embedded with photothermal material; the substrate supporting and connecting the inner layer and the outer layer is nanocellulose.

[0048] The nanocellulose-based self-fusion photothermal phase change composite fiber has a tensile strength of 10–300 MPa, a phase change enthalpy of 0–250 J / g, and a photothermal conversion efficiency of 70–95%.

[0049] This invention also provides an application of nanocellulose-based self-fusion photothermal phase change composite fiber in wearable devices, medical devices, electronic product packaging, or building thermal management.

[0050] Example 1

[0051] Preparation process of a nanocellulose-based self-fusion photothermal phase change composite fiber:

[0052] (1) Preparation of nanocellulose-based spinning solution: White pine wood strips were treated with peroxyacid and stirred with 4wt% peracetic acid solution at 85℃ and 4.5 pH for 1h. The reaction was repeated until the fiber turned pure white. Then, TEMPO oxidation treatment was performed. The filter material was reacted with TEMPO reagent / sodium hypochlorite / sodium bromide reaction system at 10.5 pH for 1.5h. After washing, modified pulp fiber was obtained. It was added to a mixer and fiberized at 5000rpm. At the same time, deionized water was added until the concentration of the obtained nanocellulose aqueous dispersion was 0.4wt%. The prepared nanocellulose aqueous dispersion was directly used as nanocellulose-based spinning solution.

[0053] (2) Preparation of outer-axis spinning solution: Take 1000g of the nanocellulose-based spinning solution prepared in step (1), weigh and add 0.4g of molybdenum disulfide powder, and process it with a homogenizer at 25000rpm for 1min to obtain the outer-axis spinning solution. The outer-axis spinning solution prepared in this embodiment is a uniform and stable composite dispersion, wherein the mass ratio of nanocellulose to molybdenum disulfide is 10:1.

[0054] (3) Preparation of inner-axis spinning solution: Take another 1000g of the nanocellulose-based spinning solution prepared in step (1); weigh 16g of n-octadecane and heat it in a water bath at 40℃ until it melts; then add the melted n-octadecane to 1000g of the nanocellulose-based spinning solution prepared in step (1), and then use a homogenizer at 25000rpm for 1min until an emulsion system is formed to obtain the inner-axis spinning solution. The inner-axis spinning solution prepared in this embodiment is a uniform and stable emulsion, wherein the mass ratio of nanocellulose to n-octadecane is 1:4.

[0055] (4) Preparation of nanocellulose-based self-fusion photothermal phase change composite fiber: The outer axis spinning solution prepared in step (2) and the inner axis spinning solution prepared in step (3) were transferred to two identical syringes for degassing; a coaxial needle with a diameter of 11G-15G was selected, the coaxial needle including an outer axis and an inner axis; the degassed outer axis spinning solution was injected into the outer axis of the coaxial needle, and the degassed inner axis spinning solution was injected into the inner axis of the coaxial needle, and simultaneously extruded into the ethanol coagulation bath at a spinning linear speed of 0.1m / s; after standing in the coagulation bath for 5min, continuous nascent fibers were formed, collected by a winding device, and dried by an infrared lamp to obtain terminal fibers, namely nanocellulose-based self-fusion photothermal phase change composite fibers. The average diameter of the nanocellulose-based self-fusion photothermal phase change composite fibers obtained after infrared lamp drying was approximately 170μm.

[0056] Application of the nanocellulose-based self-fusion photothermal phase change composite fiber prepared in Example 1 in wearable devices: The nanocellulose-based self-fusion photothermal phase change composite fiber prepared in Example 1 was woven into a piece of plain cloth, the cloth was attached to a mannequin, and placed in an environment of 10°C, where it was heated by a xenon lamp at 1000W / m. 2 Simulated sunlight irradiation was applied, and the temperature change of the fabric in contact with the doll was detected using a thermocouple probe. The temperature rapidly increased from 15°C to 44°C within 5 minutes. After irradiation was stopped, the temperature remained above 20°C for approximately 20 minutes. Figure 1As shown. Under the same conditions, a comparative test was conducted using commercial black cotton fabric. Its temperature only rose from 15°C to 35°C within 5 minutes, and the temperature dropped rapidly after irradiation stopped, indicating poor heat retention. The photothermal conversion efficiency of the nanocellulose-based self-fusion photothermal phase change composite fiber prepared in Example 1 was 82.3%. Due to the excellent photothermal conversion characteristics and good dispersibility of the photothermal material distributed in the outer layer, the fiber possesses excellent light absorption capacity. The absorbed light energy is converted into heat energy and transferred to the inner phase change material for storage. When the ambient temperature is lower than the phase change temperature, the large amount of latent heat stored is released. Therefore, this fiber also has excellent heat storage and heat retention capacity, enabling it to maintain a higher body temperature for the wearer under outdoor sunlight. Thus, it can be used as a textile fiber to prepare mountaineering clothing, scientific research clothing, etc., for use in cold climates.

[0057] Example 2

[0058] Preparation process of a nanocellulose-based self-fusion photothermal phase change composite fiber:

[0059] (1) Preparation of nanocellulose-based spinning solution: Eucalyptus wood strips were treated with peroxy acid and TEMPO oxidation, and after washing, modified pulp fibers were obtained. The fibers were added to a grinding disc and ground at 200 rpm for fibrillation treatment. At the same time, deionized water was added until the concentration of the obtained nanocellulose aqueous dispersion was 0.4 wt%. The prepared nanocellulose aqueous dispersion was directly used as nanocellulose-based spinning solution.

[0060] (2) Preparation of outer-axis spinning solution: Take 1000g of the nanocellulose-based spinning solution prepared in step (1), weigh and add 0.4g of iron oxide powder, and process it with a homogenizer at 25000rpm for 3min to obtain the outer-axis spinning solution. The outer-axis spinning solution prepared in this embodiment is a uniform and stable composite dispersion, wherein the mass ratio of nanocellulose to iron oxide is 10:1.

[0061] (3) Preparation of inner-axis spinning solution: Take another 1000g of the nanocellulose-based spinning solution prepared in step (1); weigh 40g of polyethylene glycol (PEG1000) and heat it in a water bath at 45℃ until it melts; then add the melted polyethylene glycol to 1000g of the nanocellulose-based spinning solution prepared in step (1), and then use a homogenizer at 25000rpm for 3min until an emulsion system is formed to obtain the inner-axis spinning solution. The inner-axis spinning solution prepared in this embodiment is a uniform and stable emulsion, wherein the mass ratio of nanocellulose to polyethylene glycol is 1:10.

[0062] (4) Preparation of nanocellulose-based self-fusion photothermal phase change composite fiber: The outer axis spinning solution prepared in step (2) and the inner axis spinning solution prepared in step (3) were transferred to two identical syringes for degassing; a coaxial needle with a diameter specification of 10G-13G was selected, the coaxial needle including an outer axis and an inner axis; the degassed outer axis spinning solution was injected into the outer axis of the coaxial needle, and the degassed inner axis spinning solution was injected into the inner axis of the coaxial needle, and simultaneously extruded into the acetone coagulation bath at a spinning linear speed of 0.1m / s; after standing in the coagulation bath for 5min, continuous nascent fibers were formed, collected by a winding device, and dried to obtain nanocellulose-based self-fusion photothermal phase change composite fiber. The average diameter of the nanocellulose-based self-fusion photothermal phase change composite fiber obtained after drying was approximately 220μm.

[0063] Application of the nanocellulose-based self-fusion photothermal phase change composite fiber prepared in Example 2 in wearable devices: The nanocellulose-based self-fusion photothermal phase change composite fiber prepared in Example 2 was woven into a piece of plain cloth, the cloth was attached to a mannequin, and placed in an environment of 10°C, where it was heated by a xenon lamp at 1000W / m. 2 Simulated sunlight irradiation was applied, and the temperature change of the fabric in contact with the doll was detected using a thermocouple probe. The temperature rapidly increased from 15°C to 43°C within 5 minutes. After irradiation was stopped, the temperature remained above 25°C for approximately 20 minutes. Figure 1 As shown. Under the same conditions, a comparative test was conducted using commercial black cotton fabric. Its temperature only rose from 15°C to 35°C within 5 minutes, and the temperature dropped rapidly after irradiation stopped, indicating poor heat retention. The photothermal conversion efficiency of the nanocellulose-based self-fusion photothermal phase change composite fiber prepared in Example 2 was 79.8%. Because the photothermal material distributed on the outer layer has excellent photothermal conversion characteristics and good dispersibility, it endows the fiber with excellent light absorption capacity. The absorbed light energy is converted into heat energy and transferred to the inner phase change material for storage. When the ambient temperature is lower than the phase change temperature, the large amount of latent heat stored is released. Therefore, this fiber also has excellent heat storage and heat retention capacity, enabling it to maintain a higher body temperature for the wearer under outdoor sunlight. Thus, it can be used as a textile fiber to prepare mountaineering clothing, scientific research clothing, etc., for use in cold climates.

[0064] Example 3

[0065] Preparation process of a nanocellulose-based self-fusion photothermal phase change composite fiber:

[0066] (1) Preparation of nanocellulose-based spinning solution: Pulp fibers prepared by industrial sulfate method were subjected to TEMPO oxidation treatment, washed to obtain modified pulp fibers, added to a mixer, and subjected to fibrillation treatment at 5000 rpm. At the same time, deionized water was added until the concentration of the obtained nanocellulose aqueous dispersion was 1.0 wt%. 1000 g of carboxymethyl cellulose solution with a concentration of 1.0 wt% was added to 1000 g of the prepared nanocellulose aqueous dispersion and mixed to obtain nanocellulose-based spinning solution.

[0067] (2) Preparation of external axial spinning solution: Take 1000g of the nanocellulose-based spinning solution prepared in step (1), weigh and add 5g of carbon black powder, and process with a stirrer at 5000rpm for 10min to obtain the external axial spinning solution. The external axial spinning solution prepared in this embodiment is a uniform and stable composite dispersion, wherein the mass ratio of nanocellulose to carbon black is 1:1.

[0068] (3) Preparation of inner-axis spinning solution: Take another 1000g of the nanocellulose-based spinning solution prepared in step (1); weigh 50g of n-eicosane and heat it in a water bath at 45℃ until it melts; then add the melted n-eicosane to 1000g of the nanocellulose-based spinning solution prepared in step (1), add 5g of sodium dodecyl sulfate, and then use a homogenizer at 25000rpm for 3min until an emulsion system is formed to obtain the inner-axis spinning solution. The inner-axis spinning solution prepared in this embodiment is a uniform and stable emulsion, wherein the mass ratio of nanocellulose to n-eicosane is 1:10.

[0069] (4) Preparation of nanocellulose-based self-fusion photothermal phase change composite fiber: The outer axis spinning solution prepared in step (2) and the inner axis spinning solution prepared in step (3) were transferred to two identical syringes for degassing; a coaxial needle with a diameter of 11G-15G was selected, the coaxial needle including an outer axis and an inner axis; the degassed outer axis spinning solution was injected into the outer axis of the coaxial needle, and the degassed inner axis spinning solution was injected into the inner axis of the coaxial needle, and simultaneously extruded into the ethylene glycol coagulation bath at a spinning linear velocity of 0.02m / s; after standing in the coagulation bath for 5min, continuous nascent fibers were formed, collected by a winding device, and dried by an infrared lamp to obtain nanocellulose-based self-fusion photothermal phase change composite fiber. The average diameter of the nanocellulose-based self-fusion photothermal phase change composite fiber obtained after infrared lamp drying was approximately 170μm.

[0070] Application of the nanocellulose-based self-fusion photothermal phase change composite fiber prepared in Example 3 in wearable devices: The nanocellulose-based self-fusion photothermal phase change composite fiber prepared in Example 3 was woven into a piece of plain cloth, the cloth was attached to a mannequin, and placed in an environment of 10°C, where it was heated by a xenon lamp at 1000W / m. 2Simulated sunlight irradiation was applied, and the temperature change of the fabric in contact with the doll was detected using a thermocouple probe. The temperature rapidly increased from 15°C to 41°C within 5 minutes. After irradiation was stopped, the temperature remained above 30°C for approximately 20 minutes. Figure 1 As shown. Under the same conditions, a comparative test was conducted using commercial black cotton fabric. Its temperature only rose from 15°C to 35°C within 5 minutes, and the temperature dropped rapidly after irradiation stopped, indicating poor heat retention. The photothermal conversion efficiency of the nanocellulose-based self-fusion photothermal phase change composite fiber prepared in Example 2 was 76.8%. Because the photothermal material distributed on the outer layer has excellent photothermal conversion characteristics and good dispersibility, it endows the fiber with excellent light absorption capacity. The absorbed light energy is converted into heat energy and transferred to the inner phase change material for storage. When the ambient temperature is lower than the phase change temperature, the large amount of latent heat stored is released. Therefore, this fiber also has excellent heat storage and heat retention capacity, enabling it to maintain a higher body temperature for the wearer under outdoor sunlight. Thus, it can be used as a textile fiber to prepare mountaineering clothing, scientific research clothing, etc., for use in cold climates.

[0071] Example 4

[0072] Preparation process of a nanocellulose-based self-fusion photothermal phase change composite fiber:

[0073] (1) Preparation of nanocellulose-based spinning solution: larch wood strips were treated with peroxy acid, washed to obtain modified pulp fibers, added to a mixer, and fiberized at 5000 rpm. At the same time, deionized water was added until the concentration of the obtained nanocellulose aqueous dispersion was 1.0 wt%. 400 g of 5 wt% cellulose acetate solution was added to 1600 g of the prepared nanocellulose aqueous dispersion and mixed to obtain nanocellulose-based spinning solution.

[0074] (2) Preparation of outer-axis spinning solution: Take 1000g of the nanocellulose-based spinning solution prepared in step (1), weigh and add a dispersion containing 0.4g of single-walled carbon nanotubes, and treat with a homogenizer at 20000rpm for 10min to obtain the outer-axis spinning solution. The outer-axis spinning solution prepared in this embodiment is a uniform and stable composite dispersion, wherein the mass ratio of nanocellulose to single-walled carbon nanotubes is 20:1.

[0075] (3) Preparation of inner-axis spinning solution: Take another 1000g of the nanocellulose-based spinning solution prepared in step (1); weigh 32g of n-hexadecyl alcohol and heat it in a water bath at 60℃ until it melts; then add the melted n-hexadecyl alcohol to 1000g of the nanocellulose-based spinning solution prepared in step (1), add 3g of sodium dodecylbenzene sulfate, and then treat it with an ultrasonic machine for 30min until an emulsion system is formed to obtain the inner-axis spinning solution. The inner-axis spinning solution prepared in this embodiment is a uniform and stable emulsion, wherein the mass ratio of nanocellulose to n-hexadecyl alcohol is 1:4.

[0076] (4) Preparation of nanocellulose-based self-fusion photothermal phase change composite fiber: The outer axis spinning solution prepared in step (2) and the inner axis spinning solution prepared in step (3) were transferred to two identical syringes for degassing; a coaxial needle with a diameter of 11G-15G was selected, the coaxial needle including an outer axis and an inner axis; the degassed outer axis spinning solution was injected into the outer axis of the coaxial needle, and the degassed inner axis spinning solution was injected into the inner axis of the coaxial needle, and both were sprayed into the hydrochloric acid coagulation bath at a spinneret speed of 0.1m / s; after standing in the coagulation bath for 5min, continuous nascent fibers were formed, collected by a winding device, and dried to obtain nanocellulose-based self-fusion photothermal phase change composite fiber. The average diameter of the nanocellulose-based self-fusion photothermal phase change composite fiber obtained after drying was approximately 170μm.

[0077] Application of the nanocellulose-based self-fusion photothermal phase change composite fiber prepared in Example 4 in the medical field: The nanocellulose-based self-fusion photothermal phase change composite fiber prepared in Example 4 was woven into a plain cloth, and the cloth was applied to the knee. An infrared lamp with a power of 1000W / m was used to apply the fabric. 2 Under irradiation at room temperature, the surface temperature of the fabric rapidly increased from 23°C to 75°C within 10 minutes. After irradiation was stopped, the temperature remained above 45°C for more than 15 minutes. The photothermal conversion efficiency of the nanocellulose-based self-fusion photothermal phase change composite fiber prepared in Example 4 reached 79.6%. Because photothermal materials with excellent photothermal properties can rapidly absorb near-infrared radiation, causing the fiber to heat up to a high temperature, and different phase change materials are selected in the inner layer as temperature control media to effectively control the fiber's heat release temperature and duration, and the phase change materials in the inner layer are encapsulated by the outer shell to prevent leakage, while the nanocellulose as the fiber matrix also has good biocompatibility, this fiber has the potential to be applied to infrared thermotherapy and can be used to prepare thermotherapy masks, nose strips, knee pads, headbands, etc., for use in the biomedical field.

[0078] Example 5

[0079] Preparation process of a nanocellulose-based self-fusion photothermal phase change composite fiber:

[0080] (1) Preparation of nanocellulose-based spinning solution: Bamboo powder was esterified with acetic anhydride, washed to obtain modified pulp fiber, added to a mixer, and fiberized at 5000 rpm. At the same time, deionized water was added until the concentration of the obtained nanocellulose aqueous dispersion was 0.8 wt%. 1000 g of chitosan solution with a concentration of 1 wt% was added to 1000 g of the prepared nanocellulose aqueous dispersion and mixed to obtain nanocellulose-based spinning solution.

[0081] (2) Preparation of external axial spinning solution: Take 1000g of the nanocellulose-based spinning solution prepared in step (1), weigh and add 0.4g of cesium tungsten oxide powder, and process it with a wall-breaking machine at 5000rpm for 10min to obtain the external axial spinning solution. The external axial spinning solution prepared in this embodiment is a uniform and stable composite dispersion, wherein the mass ratio of nanocellulose to cesium tungsten oxide is 10:1.

[0082] (3) Preparation of inner-axis spinning solution: Take another 1000g of the nanocellulose-based spinning solution prepared in step (1); weigh 16g of paraffin wax and heat it in a water bath at 60℃ until it melts; then add the melted paraffin wax to 1000g of the nanocellulose-based spinning solution prepared in step (1), add 1g of hexadecyltrimethylammonium bromide, and then treat it with a cell disruptor for 20min until an emulsion system is formed to obtain the inner-axis spinning solution. The inner-axis spinning solution prepared in this embodiment is a uniform and stable emulsion, wherein the mass ratio of nanocellulose to paraffin wax is 1:4.

[0083] (4) Preparation of nanocellulose-based self-fusion photothermal phase change composite fiber: The outer axis spinning solution prepared in step (2) and the inner axis spinning solution prepared in step (3) were transferred to two identical syringes for degassing; a coaxial needle with a diameter of 11G-15G was selected, the coaxial needle including an outer axis and an inner axis; the degassed outer axis spinning solution was injected into the outer axis of the coaxial needle, and the degassed inner axis spinning solution was injected into the inner axis of the coaxial needle, and simultaneously extruded into the ethanol coagulation bath at a spinning linear speed of 0.1m / s; after standing in the coagulation bath for 5min, continuous nascent fibers were formed, collected by a winding device, and dried at room temperature to obtain nanocellulose-based self-fusion photothermal phase change composite fiber. The average diameter of the nanocellulose-based self-fusion photothermal phase change composite fiber obtained after drying at room temperature was approximately 170μm.

[0084] Application of the nanocellulose-based self-fusion photothermal phase change composite fiber prepared in Example 5 in the medical field: The nanocellulose-based self-fusion photothermal phase change composite fiber prepared in Example 5 was woven into a plain cloth, and the cloth was applied to the knee. An infrared lamp with a power of 1000W / m was used to apply the fabric. 2Under irradiation at room temperature, the surface temperature of the fabric rapidly increased from 23°C to 78°C within 10 minutes. After irradiation was stopped, the temperature remained above 50°C for more than 15 minutes. The photothermal conversion efficiency of the nanocellulose-based self-fusion photothermal phase change composite fiber prepared in Example 4 reached 84.6%. Because photothermal materials with excellent photothermal properties can rapidly absorb near-infrared radiation, allowing the fiber to heat up to a high temperature, and different phase change materials selected in the inner layer as temperature control media effectively control the fiber's heat release temperature and duration, and because the phase change materials in the inner layer are encapsulated in the outer shell to prevent leakage, and because nanocellulose, as the fiber matrix, also has good biocompatibility, this fiber has the potential to be applied to infrared thermotherapy and can be used to prepare thermotherapy masks, nose strips, knee pads, headbands, and other applications in the biomedical field.

[0085] Example 6

[0086] Preparation process of a nanocellulose-based self-fusion photothermal phase change composite fiber:

[0087] (1) Preparation of nanocellulose-based spinning solution: Straw was carboxymethylated and washed to obtain modified pulp fibers. The fibers were added to a mixer and fiberized at 5000 rpm. At the same time, deionized water was added until the concentration of the obtained nanocellulose aqueous dispersion was 0.8 wt%. 1000 g of sodium alginate solution with a concentration of 1 wt% was added to 1000 g of the prepared nanocellulose aqueous dispersion and mixed to obtain nanocellulose-based spinning solution.

[0088] (2) Preparation of outer-axis spinning solution: Take 1000g of the nanocellulose-based spinning solution prepared in step (1), weigh and add 0.4g of titanium dioxide powder, and process it with a homogenizer at 20000rpm for 10min to obtain the outer-axis spinning solution. The outer-axis spinning solution prepared in this embodiment is a uniform and stable composite dispersion, wherein the mass ratio of nanocellulose to titanium dioxide is 10:1.

[0089] (3) Preparation of inner-axis spinning solution: Take another 1000g of the nanocellulose-based spinning solution prepared in step (1); weigh 40g of n-octadecane and heat it in a water bath at 40℃ until it melts; then add the melted n-octadecane to 1000g of the nanocellulose-based spinning solution prepared in step (1), add 4g of alkylphenol polyoxyethylene ether, and then treat it with an ultrasonic machine for 30min until an emulsion system is formed to obtain the inner-axis spinning solution. The inner-axis spinning solution prepared in this embodiment is a uniform and stable emulsion, wherein the mass ratio of nanocellulose to n-octadecane is 1:10.

[0090] (4) Preparation of nanocellulose-based self-fusion photothermal phase change composite fiber: The outer axis spinning solution prepared in step (2) and the inner axis spinning solution prepared in step (3) were transferred to two identical syringes for degassing; a coaxial needle with a diameter specification of 21G-27G was selected, the coaxial needle including an outer axis and an inner axis; the degassed outer axis spinning solution was injected into the outer axis of the coaxial needle, and the degassed inner axis spinning solution was injected into the inner axis of the coaxial needle, and simultaneously extruded into the methanol coagulation bath at a spinning linear speed of 0.1m / s; after standing in the coagulation bath for 5min, continuous nascent fibers were formed, collected by a winding device, and dried at room temperature to obtain nanocellulose-based self-fusion photothermal phase change composite fiber. The average diameter of the nanocellulose-based self-fusion photothermal phase change composite fiber obtained after drying at room temperature was about 50μm.

[0091] Application of the nanocellulose-based self-fusion photothermal phase change composite fiber prepared in Example 6 as a textile for building thermal management: The nanocellulose-based self-fusion photothermal phase change composite fiber prepared in Example 6 has good flexibility and tensile strength. It can be processed into short fibers by cutting, and its phase change temperature (28°C) is close to the human body's comfortable temperature range. Therefore, by selecting a suitable phase change material so that the fiber's phase change temperature is within the range of the indoor design temperature or the air conditioning system control temperature, it can be used to prepare home furnishing products such as curtains, blankets, cushions, and bedding, as well as their filling materials, thereby maintaining a comfortable indoor temperature, alleviating diurnal temperature variation, and reducing building energy consumption.

[0092] Example 7

[0093] Preparation process of a nanocellulose-based self-fusion photothermal phase change composite fiber:

[0094] (1) Preparation of nanocellulose-based spinning solution: Poplar wood strips were treated with peroxy acid and quaternization, and after washing, modified pulp fibers were obtained. The fibers were added to a mixer and fiberized at 5000 rpm. At the same time, deionized water was added until the concentration of the obtained nanocellulose aqueous dispersion was 0.8 wt%. 1000 g of 1 wt% hyaluronic acid solution was added to 1000 g of the prepared nanocellulose aqueous dispersion and mixed to obtain nanocellulose-based spinning solution.

[0095] (2) Preparation of outer-axis spinning solution: Take 1000g of the nanocellulose-based spinning solution prepared in step (1), weigh and add 0.4g of Mxene, and treat with an ultrasonic machine for 20min to obtain the outer-axis spinning solution. The outer-axis spinning solution prepared in this embodiment is a uniform and stable composite dispersion, wherein the mass ratio of nanocellulose to Mxene is 10:1.

[0096] (3) Preparation of inner-axis spinning solution: Take another 1000g of the nanocellulose-based spinning solution prepared in step (1); weigh 16g of dodecanoic acid and 16g of tetradecyl alcohol and mix them, then heat them in a water bath at 50℃ until they melt to obtain the molten dodecanoic acid-tetradecyl alcohol mixed phase change material; then add the molten dodecanoic acid-tetradecyl alcohol mixed phase change material to 1000g of the nanocellulose-based spinning solution prepared in step (1), and then treat it with an ultrasonic machine for 20min until an emulsion system is formed to obtain the inner-axis spinning solution. The inner-axis spinning solution prepared in this embodiment is a uniform and stable emulsion, wherein the mass ratio of nanocellulose, dodecanoic acid and tetradecyl alcohol is 1:4:4.

[0097] (4) Preparation of nanocellulose-based self-fusion photothermal phase change composite fiber: The outer axis spinning solution prepared in step (2) and the inner axis spinning solution prepared in step (3) were transferred to two identical syringes for degassing; a coaxial needle with a diameter specification of 21G-27G was selected, the coaxial needle including an outer axis and an inner axis; the degassed outer axis spinning solution was injected into the outer axis of the coaxial needle, and the degassed inner axis spinning solution was injected into the inner axis of the coaxial needle, and simultaneously extruded into the ethanol coagulation bath at a spinning linear speed of 0.1m / s; after standing in the coagulation bath for 5min, continuous nascent fibers were formed, collected by a winding device, and dried at high temperature through a heating sleeve to obtain nanocellulose-based self-fusion photothermal phase change composite fiber. The average diameter of the nanocellulose-based self-fusion photothermal phase change composite fiber obtained after high temperature drying is about 50μm.

[0098] Application of the nanocellulose-based self-fusion photothermal phase change composite fiber prepared in Example 7 as a textile for building thermal management: The nanocellulose-based self-fusion photothermal phase change composite fiber prepared in Example 7 has good flexibility and tensile strength. It can be processed into short fibers by cutting, and its phase change temperature (26°C) is close to the human body's comfortable temperature range. Therefore, by selecting a suitable phase change material so that the fiber's phase change temperature is within the range of the indoor design temperature or the air conditioning system control temperature, it can be used to prepare home furnishing products such as curtains, blankets, cushions, and bedding, as well as their filling materials, thereby maintaining a comfortable indoor temperature, alleviating diurnal temperature variation, and reducing building energy consumption.

[0099] Example 8

[0100] Preparation process of a nanocellulose-based self-fusion photothermal phase change composite fiber:

[0101] (1) Preparation of nanocellulose-based spinning solution: Beetroot was treated with peroxy acid, washed to obtain modified pulp fiber, added to a mixer, and fiberized at 5000 rpm. At the same time, deionized water was added until the concentration of the obtained nanocellulose aqueous dispersion was 0.8 wt%. 1000 g of 1 wt% cyclodextrin solution was added to 1000 g of the prepared nanocellulose aqueous dispersion and mixed to obtain nanocellulose-based spinning solution.

[0102] (2) Preparation of outer-axis spinning solution: Take 1000g of the nanocellulose-based spinning solution prepared in step (1), weigh and add 0.4g of polydopamine particles, and treat with a cell disruptor for 10min to obtain the outer-axis spinning solution. The outer-axis spinning solution prepared in this embodiment is a uniform and stable composite dispersion, wherein the mass ratio of nanocellulose to polydopamine particles is 10:1.

[0103] (3) Preparation of inner-axis spinning solution: Take another 1000g of the nanocellulose-based spinning solution prepared in step (1); weigh 24g of n-octadecane and heat it in a water bath at 40℃ until it melts; then add the melted n-octadecane to 1000g of the nanocellulose-based spinning solution prepared in step (1), and then treat it with an ultrasonic machine for 30min until an emulsion system is formed to obtain the inner-axis spinning solution. The inner-axis spinning solution prepared in this embodiment is a uniform and stable emulsion, wherein the mass ratio of nanocellulose to n-octadecane is 1:6.

[0104] (4) Preparation of nanocellulose-based self-fusion photothermal phase change composite fiber: The outer axis spinning solution prepared in step (2) and the inner axis spinning solution prepared in step (3) were transferred to two identical syringes for degassing; a coaxial needle with a diameter specification of 17G-22G was selected, the coaxial needle including an outer axis and an inner axis; the degassed outer axis spinning solution was injected into the outer axis of the coaxial needle, and the degassed inner axis spinning solution was injected into the inner axis of the coaxial needle, and simultaneously extruded into the propylene glycol coagulation bath at a spinning linear speed of 0.1m / s; after standing in the coagulation bath for 5min, continuous nascent fibers were formed, collected by a winding device, and dried at high temperature through a heating sleeve to obtain nanocellulose-based self-fusion photothermal phase change composite fiber. The average diameter of the nanocellulose-based self-fusion photothermal phase change composite fiber obtained after high temperature drying is about 80μm.

[0105] Application of the nanocellulose-based self-fusion photothermal phase change composite fiber prepared in Example 8 as a textile for building thermal management: The nanocellulose-based self-fusion photothermal phase change composite fiber prepared in Example 8 has good flexibility and tensile strength. It can be processed into short fibers by cutting, and its phase change temperature (28°C) is close to the human body's comfortable temperature range. Therefore, by selecting a suitable phase change material so that the fiber's phase change temperature is within the range of the indoor design temperature or the air conditioning system control temperature, it can be used to prepare home furnishing products such as curtains, blankets, cushions, and bedding, as well as their filling materials, thereby maintaining a comfortable indoor temperature, alleviating diurnal temperature variation, and reducing building energy consumption.

[0106] Example 9

[0107] Preparation process of a nanocellulose-based self-fusion photothermal phase change composite fiber:

[0108] (1) Preparation of nanocellulose-based spinning solution: Cotton was treated with peroxy acid and TEMPO oxidation, and after washing, modified pulp fibers were obtained. The fibers were added to a high-pressure homogenizer and fiberized at 1000 rpm. At the same time, deionized water was added until the concentration of the obtained nanocellulose aqueous dispersion was 0.8 wt%. 1000 g of 1 wt% dextran solution was added to 1000 g of the prepared nanocellulose aqueous dispersion and mixed to obtain nanocellulose-based spinning solution.

[0109] (2) Preparation of outer-axis spinning solution: Take 1000g of the nanocellulose-based spinning solution prepared in step (1), weigh and add 0.4g of black phosphorus, and shear at 20000rpm for 10min using a homogenizer to obtain the outer-axis spinning solution. The outer-axis spinning solution prepared in this embodiment is a uniform and stable composite dispersion, wherein the mass ratio of nanocellulose to black phosphorus is 10:1.

[0110] (3) Preparation of inner-axis spinning solution: Take another 1000g of the nanocellulose-based spinning solution prepared in step (1); weigh 40g of n-octadecane and heat it in a water bath at 40℃ until it melts; then add the melted n-octadecane to 1000g of the nanocellulose-based spinning solution prepared in step (1), and then use a homogenizer at 20000rpm for 5min until an emulsion system is formed to obtain the inner-axis spinning solution. The inner-axis spinning solution prepared in this embodiment is a uniform and stable emulsion, wherein the mass ratio of nanocellulose to n-octadecane is 1:10.

[0111] (4) Preparation of nanocellulose-based self-fusion photothermal phase change composite fiber: The outer axis spinning solution prepared in step (2) and the inner axis spinning solution prepared in step (3) were transferred to two identical syringes for degassing; a coaxial needle with a diameter specification of 17G-22G was selected, the coaxial needle including an outer axis and an inner axis; the degassed outer axis spinning solution was injected into the outer axis of the coaxial needle, and the degassed inner axis spinning solution was injected into the inner axis of the coaxial needle, and simultaneously extruded into the propylene glycol coagulation bath at a spinning linear speed of 0.1m / s; after standing in the coagulation bath for 5min, continuous nascent fibers were formed, collected by a winding device, and microwave dried to obtain nanocellulose-based self-fusion photothermal phase change composite fiber. The average diameter of the nanocellulose-based self-fusion photothermal phase change composite fiber obtained after microwave drying was approximately 80μm.

[0112] Application of the nanocellulose-based self-fusion photothermal phase change composite fiber prepared in Example 9 as electronic product packaging: The nanocellulose-based self-fusion photothermal phase change composite fiber prepared in Example 9 has good mechanical properties. When used as a reinforcing filler in a mobile phone case, due to the fiber's photothermal and heat storage properties, the phone case can maintain a higher temperature in low ambient temperatures during winter, thus maintaining a higher operating temperature for the mobile phone battery and preventing power loss and battery capacity degradation. Therefore, this fiber can be used to prepare packaging materials for electronic products.

[0113] Example 10

[0114] Preparation process of a nanocellulose-based self-fusion photothermal phase change composite fiber:

[0115] (1) Preparation of nanocellulose-based spinning solution: Rice straw was treated with peroxy acid and TEMPO oxidation, and after washing, modified pulp fibers were obtained. The fibers were added to a high-pressure homogenizer and fiberized at 1000 rpm. At the same time, deionized water was added until the concentration of the obtained nanocellulose aqueous dispersion was 0.4 wt%. The prepared nanocellulose aqueous dispersion was directly used as nanocellulose-based spinning solution.

[0116] (2) Preparation of outer-axis spinning solution: Take 1000g of the nanocellulose-based spinning solution prepared in step (1), weigh and add 0.4g of boronene, and shear at 20000rpm for 10min using a homogenizer to obtain the outer-axis spinning solution. The outer-axis spinning solution prepared in this embodiment is a uniform and stable composite dispersion, wherein the mass ratio of nanocellulose to boronene is 10:1.

[0117] (3) Preparation of inner-axis spinning solution: Take another 1000g of the nanocellulose-based spinning solution prepared in step (1); weigh 40g of n-octadecane and heat it in a water bath at 40℃ until it melts; then add the melted n-octadecane to 1000g of the nanocellulose-based spinning solution prepared in step (1), and then use a homogenizer at 20000rpm for 5min until an emulsion system is formed to obtain the inner-axis spinning solution. The inner-axis spinning solution prepared in this embodiment is a uniform and stable emulsion, wherein the mass ratio of nanocellulose to n-octadecane is 1:10.

[0118] (4) Preparation of nanocellulose-based self-fusion photothermal phase change composite fiber: The outer axis spinning solution prepared in step (2) and the inner axis spinning solution prepared in step (3) were transferred to two identical syringes for degassing; a coaxial needle with a diameter specification of 17G-22G was selected, the coaxial needle including an outer axis and an inner axis; the degassed outer axis spinning solution was injected into the outer axis of the coaxial needle, and the degassed inner axis spinning solution was injected into the inner axis of the coaxial needle, and simultaneously extruded into the propylene glycol coagulation bath at a spinning linear speed of 0.1m / s; after standing in the coagulation bath for 5min, continuous nascent fibers were formed, collected by a winding device, and microwave dried to obtain nanocellulose-based self-fusion photothermal phase change composite fiber. The average diameter of the nanocellulose-based self-fusion photothermal phase change composite fiber obtained after microwave drying was approximately 80μm.

[0119] Application of the nanocellulose-based self-fusion photothermal phase change composite fiber prepared in Example 10 as electronic product packaging: The nanocellulose-based self-fusion photothermal phase change composite fiber prepared in Example 10 possesses excellent mechanical properties. When used as a reinforcing filler in a mobile phone case, due to the fiber's photothermal and heat storage properties, the phone case can maintain a higher temperature in lower ambient temperatures during winter, thus maintaining a higher operating temperature for the mobile phone battery and preventing power loss and capacity reduction. Therefore, this fiber can be used to prepare packaging materials for electronic products.

[0120] Test case

[0121] The mechanical properties of the nanocellulose-based self-fusion photothermal phase change composite fibers prepared in Examples 1-10 above were tested by tensile testing. Their Young's modulus, tensile strength, and elongation at break are shown in Table 1. The tensile strength of all nanocellulose-based self-fusion photothermal phase change composite fibers prepared in these examples exceeded 100 MPa, indicating that the nanocellulose-based self-fusion photothermal phase change composite fibers prepared in this invention have superior tensile properties. This is attributed to the fiber's unique layered structure design: 1) The nanocellulose in the outer layer undergoes efficient shearing by the inner wall of the needle during spinning, forming a good orientation and providing mechanical support and protection for the fiber; 2) The porous network formed by the nanocellulose in the inner layer is intertwined and tightly bonded with the nanocellulose in the outer layer, thus forming a continuous skeletal support. This greatly eliminates the influence of the difference in deformation behavior of the inner and outer layers under load on the fiber's tensile properties. Figure 2 As shown, this not only helps in the shaping of phase change materials but also endows the fibers with superior mechanical properties. Although solid-liquid phase change materials are brittle in their unmelted state, this composite fiber still exhibits good flexibility and weavability at room temperature when the phase change material is unmelted. It can be coiled, knotted, and even woven into fabric, meeting the requirements of practical applications, such as... Figure 3 As shown, this is because an emulsion template method is used to fill the nanofiber porous network of the inner layer of the fiber with the phase change material in the form of a dispersed phase, rather than a larger aggregated phase or a continuous phase, in order to prevent damage to the inherent flexibility of the fiber.

[0122] Table 1: Young's modulus, tensile strength, and elongation at break of phase change fibers in different embodiments

[0123] sample Young's modulus (GPa) Tensile strength (MPa) Elongation at break (%) Example 1 7.4 137 3.7 Example 2 6.0 118 5.5 Example 3 10.4 182 3.2 Example 4 7.0 144 4.3 Example 5 7.5 127 4.5 Example 6 10.9 198 3.6 Example 7 8.2 139 3.4 Example 8 5.5 109 5.9 Example 9 6.5 124 5.8 Example 10 6.8 132 6.4

[0124] (2) The melting enthalpy (ΔH) of the nanocellulose-based self-fusion photothermal phase change composite fibers prepared in Examples 1-10 above. m ) and enthalpy of crystallization (ΔH) c The phase change fibers prepared by this invention exhibit high latent heat of phase change, and the latent heat loss is very small after multiple cycles. The endothermic and exothermic curves essentially overlap. (Table 2 shows the results.) Figure 4 As shown, the double encapsulation structure formed by nanocellulose in the inner and outer layers of the composite fiber plays a superior encapsulation role, making it less prone to leakage of the phase change material during use and effectively meeting service requirements.

[0125] Table 2: Phase change enthalpy values ​​of phase change fibers after different cycle tests in different embodiments

[0126]

[0127]

[0128] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a nanocellulose-based self-fusion photothermal phase change composite fiber, characterized in that, Includes the following steps: (1) Obtain a nanocellulose aqueous dispersion with a concentration of 0.2~10wt% by chemical pretreatment and mechanical fibrillation treatment of plant fiber raw materials or industrial pulp; mix 10,000 parts by weight of nanocellulose aqueous dispersion with 0~10,000 parts by weight of high molecular weight polysaccharide solution with a concentration of 1~20 wt% to obtain nanocellulose-based spinning solution; (2) Add 1-100 parts by weight of photothermal material to 10,000 parts by weight of the nanocellulose-based spinning solution prepared in step (1), and obtain an outer-axis spinning solution by shearing treatment; the photothermal material is polydopamine, polypyrrole, gold nanoparticles, silver nanoparticles, aluminum nanoparticles, MXene, carbon black, graphite, graphene oxide, carbon nanotubes, molybdenum disulfide, black phosphorus, boronene, iron oxide, iron tetroxide, titanium dioxide, titanium trioxide or cesium tungsten oxide; (3) Add 100-2000 parts by weight of the melted phase change material and 0-100 parts by weight of the surfactant to 10000 parts by weight of the nanocellulose-based spinning solution prepared in step (1), and obtain the inner shaft spinning solution by emulsification treatment; the phase change material is one or more of polyethylene glycol, paraffin wax, C14-C28 aliphatic alkanes, fatty acids, and fatty alcohols in any proportion; (4) The outer shaft spinning solution prepared in step (2) and the inner shaft spinning solution prepared in step (3) are degassed. The degassed outer shaft spinning solution is injected into the outer shaft of the coaxial needle, and the degassed inner shaft spinning solution is injected into the inner shaft of the coaxial needle. At the same time, the spinneret is extruded into the coagulation bath at a spinneret speed of 0.02~2 m / s. The spinneret is allowed to stand for 1~20 min to form nascent fibers. The fibers are collected by the winding device and dried to obtain nanocellulose-based self-fusion photothermal phase change composite fibers.

2. The method for preparing a nanocellulose-based self-fusion photothermal phase change composite fiber according to claim 1, characterized in that, The high molecular weight polysaccharide solution is a solution of carboxymethyl cellulose, hydroxypropyl cellulose, cellulose acetate, cellulose xanthate, cellulose phosphate, cellulose quaternary ammonium salt, dextran, chitosan, cyclodextrin, starch, sodium alginate, pectin, hemicellulose, or hyaluronic acid.

3. The method for preparing a nanocellulose-based self-fusion photothermal phase change composite fiber according to claim 1, characterized in that, The shearing process is performed by using a mixer, cell disruptor, homogenizer, ultrasonic machine, or cell disruptor for 1-30 minutes.

4. The method for preparing a nanocellulose-based self-fusion photothermal phase change composite fiber according to claim 1, characterized in that, The emulsification process involves treating the cells with a homogenizer, sonicator, or cell disruptor for 1-30 minutes until an emulsion system is formed.

5. The method for preparing a nanocellulose-based self-fusion photothermal phase change composite fiber according to claim 1, characterized in that, The coagulation bath is one or more of methanol, ethanol, acetone, ethylene glycol, isopropanol, propylene glycol and their aqueous solutions in any proportion, and the concentration of the aqueous solution is not less than 60 vol.

6. The method for preparing a nanocellulose-based self-fusion photothermal phase change composite fiber according to claim 1, characterized in that, The drying method is room temperature drying, infrared lamp drying, high temperature drying, or microwave drying.

7. A nanocellulose-based self-fusion photothermal phase change composite fiber prepared by any one of claims 1-6, characterized in that, The nanocellulose-based self-fusion photothermal phase change composite fiber includes an inner layer and an outer layer; the inner layer is a porous network structure formed by nanocellulose, and the pores of the porous network structure are filled with phase change material; the outer layer is a dense shell formed by nanocellulose, embedded with photothermal material; the substrate supporting and connecting the inner and outer layers is nanocellulose.

8. The application of the nanocellulose-based self-fusion photothermal phase change composite fiber of claim 7 in wearable devices, medical devices, electronic product packaging, or building thermal management.

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