Down-like fractal structure heat-preserving aerogel and preparation method thereof

Abstract

The invention relates to the technical field of fiber materials, in particular to down-like fractal structure heat preservation aerogel and a preparation method thereof. The preparation method of the down-like fractal structure heat-preserving aerogel comprises the following steps: step 1, mixing supporting fibers and functional fibers, carrying out chemical treatment, and then carrying out drum-type hot air drying and mixing to obtain a blending system; step 2, dispersing the blending system in a solution containing a dispersing agent and a dispersing aid, and stirring to obtain a suspension; and carrying out freeze drying and heat setting on the suspension to obtain the down-like fractal structure heat-preserving thermal gel. According to the invention, a'trunk-down silk-down branchlet 'multistage fractal structure of natural down is simulated on a microscopic / mesoscopic scale. According to the structure, the specific surface area and the number of pores can be increased to the maximum extent, so that static air is efficiently stored, convection and conduction heat transfer are remarkably reduced, and the extreme heat insulation and heat preservation effect is achieved.

Description

Technical Field

[0001] This invention relates to the field of fiber materials technology, and in particular to a down-like fractal structure thermal insulation aerogel and its preparation method. Background Technology

[0002] Natural down exhibits excellent warmth retention due to its composite structure of "feather-support resilience and down-core-filament multi-level fractal air storage." However, its inherent defects, such as the susceptibility of its protein matrix to microbial growth and high processing energy consumption, hinder its large-scale application. To address this, existing down-like materials only simulate air storage through mixing and winding, failing to replicate the "support-insulation" composite characteristics and fractal structure. In the field of thermal insulation, aerogels are widely used due to their unique porosity, but they suffer from problems such as lack of pore gradient, poor resilience, and high brittleness. Neither of these two types of materials has overcome the synergistic bottleneck of "high thermal insulation, high resilience, lightweight, and processability." Therefore, there is an urgent need to develop a down-like fractal structure thermal aerogel to achieve optimized structure with high porosity and pore distribution, as well as core properties such as low thermal conductivity and high compression resilience, overcoming the shortcomings of existing materials from both structural design and performance control perspectives. Summary of the Invention

[0003] To address the shortcomings of existing technologies, the present invention aims to provide a down-like fractal structure thermal aerogel and its preparation method.

[0004] To achieve the above objectives, the present invention provides the following solution: One of the technical solutions of this invention is a method for preparing a down-like fractal structure thermal insulation aerogel, comprising the following steps: Step 1: Mix the supporting fiber and functional fiber and chemically treat them, then dry them with hot air in a drum and mix them to obtain a blend system (a basic fiber raw material with high porosity and low density). Step 2: Disperse the blended system in a solution containing a dispersant and a dispersing aid, stir to obtain a suspension; freeze-dry and heat-set the suspension to obtain the down-like fractal structure thermal aerogel.

[0005] The second technical solution of the present invention is a down-like fractal structure thermal aerogel prepared according to the above preparation method.

[0006] The third technical solution of this invention is the application of the above-mentioned down-like fractal structure thermal insulation aerogel in the preparation of thermal insulation materials.

[0007] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a down-insulating fractal structure aerogel with high thermal insulation performance. The method of this invention further enhances the thermal insulation efficiency of the prepared aerogel. Through the synergistic effect of multi-fiber, it mimics the multi-level fractal structure of natural down at the micro / mesoscale, resembling the 'trunk-filament-branch' structure. This structure maximizes the specific surface area and pore number, thereby efficiently storing static air and significantly reducing convective and conductive heat transfer, achieving an ultimate thermal insulation effect. The properties of the composite fibers and aerogel give it high mechanical resilience, extreme lightweight, and strong processability, ensuring a certain degree of uniform pore density and efficient static air storage capacity, making this material demonstrate significant application value in the field of thermal insulation. Attached Figure Description

[0008] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0009] Figure 1 This is an optical photograph of the down-like fractal structure thermal aerogel in Example 1.

[0010] Figure 2 This is a scanning electron microscope image of the down-like fractal structure thermal aerogel in Example 1.

[0011] Figure 3 The compression cycle curve (1000 cycles) of the down-like fractal structure thermal aerogel in Example 1 is shown.

[0012] Figure 4 This is an infrared imaging effect of the down-like fractal structure thermal aerogel in Example 1. Detailed Implementation

[0013] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0014] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0015] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0016] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0017] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0018] The down-like fractal structure thermal aerogel of this invention uses multi-component composite fibers as the base material, combining the structure of natural down with the high-efficiency thermal insulation advantages of aerogel. By constructing a three-level fractal network of "supporting fibers (main trunk, simulating the supporting function of feathers), functional fibers (branch, replicating the fluffy effect of down), and ultrafine fibers (micro-branch, surface fibrillation, enhancing air storage capacity)," it achieves a structure with high porosity and optimized pore distribution, as well as core performance characteristics of low thermal conductivity and high compression resilience. It overcomes the shortcomings of existing materials from the dual dimensions of structural design and performance control, providing an efficient solution for thermal insulation needs in multiple scenarios.

[0019] The first aspect of this invention provides a method for preparing a down-like fractal structure thermal aerogel, comprising the following steps: Step 1: Mix the supporting fibers and functional fibers and chemically treat them, then dry them with hot air in a drum and mix them to obtain a fiber system (a basic fiber raw material with high porosity and low density). Step 2: Disperse the blended system in a solution containing a dispersant and a dispersing aid, stir to obtain a suspension; freeze-dry and heat-set the suspension to obtain the down-like fractal structure thermal aerogel.

[0020] In a preferred embodiment of the present invention, in step 1, the supporting fiber is an ES fiber with an average diameter of 8~20μm; the functional fiber is at least one of polyester / nylon island fiber, polyester / polyester island fiber, and polyester fiber.

[0021] The supporting fiber is a fiber with certain thermal bonding properties, with ES fiber being the optimal choice. More preferably, the ES fiber is PE / PET or PE / PP fiber.

[0022] In a preferred embodiment of the present invention, the functional fiber is a mixture of polyester / polyester island-island fibers with island phase diameters of 5-6 μm and polyester / polyester island-island fibers with island phase diameters of 2-3 μm in a mass ratio of 1:(1-9). The mass ratio of the functional fibers is determined based on the following reasons: the construction of the fractal structure requires a balance between the integrity of the fractal hierarchy and the stability of the network. Fibers with island phase diameters of 5-6 μm mainly form primary branch structures, providing network continuity and structural support; fibers with island phase diameters of 2-3 μm have smaller diameters and mainly form secondary branches or micro-branch structures, significantly increasing the specific surface area and the number of micropores. When the mass ratio of the two fibers is controlled within the range of 1:(1-9), a fractal network structure with clear primary and secondary branches and gradual transitions can be formed on a spatial scale, thereby simultaneously ensuring the number of pores, pore size gradient, and overall structural stability. When this ratio is lower than 1:1, the number of secondary branches is insufficient, the network is dominated by coarse fiber entanglement, the pore size is too large, the pore hierarchy is simple, the static air storage capacity decreases, the thermal insulation performance is significantly weakened, the fractal structure is incomplete, and it is difficult to reflect the characteristics of a down-like structure. When the ratio is higher than 1:9, the proportion of microfiber is too large, and excessive entanglement or local aggregation of fibers is likely to occur, resulting in a decrease in network continuity and structural support capacity. During freeze-drying and compression, pore wall collapse is likely to occur, and the resilience and structural durability will be reduced.

[0023] In a preferred embodiment of the present invention, the mass ratio of the supporting fiber to the functional fiber is 1:1 to 2.33. The core objective of this ratio is to establish a synergistic relationship between "structural support" and "fractal construction." The supporting fiber (ES fiber) constitutes the "main skeleton," determining resilience and structural stability; the functional fiber constitutes "branches and micro-branches," determining the number of pores and thermal insulation performance. When the ratio of supporting fiber to functional fiber is less than 1:2.33, the adverse effects are insufficient supporting skeleton force, and the fiber network after freeze-drying mainly relies on fine fiber entanglement for maintenance; irreversible collapse is prone to occur during compression or multiple cyclic loading, and the stress retention rate decreases significantly. When the supporting fiber ratio is greater than 1:1, the proportion of supporting fiber is too high, the number of fractal branches is insufficient, the network structure tends to be dense, the number of pores and specific surface area decrease significantly, and the static air storage capacity decreases.

[0024] In a preferred embodiment of the present invention, the chemical treatment conditions are set independently as follows: the mixed fibers are immersed in a NaOH solution (water as solvent) with a concentration of 7-150 g / L for 5 min to 1 h, the immersion temperature is 25-96 °C, and the liquor ratio is 1:50-200 (the mass ratio of the mixed fibers to the NaOH solution is 1:50-200). The liquor ratio has a significant impact on the uniformity and structural stability of the functional fibers after chemical treatment. If the liquor ratio is too small, the fibers will agglomerate and become entangled and agglomerated after chemical treatment, which will seriously affect the pore uniformity of the subsequent materials; while under the condition of a larger liquor ratio, it is possible to ensure that the alkali solution fully contacts the fibers while avoiding excessive local alkali concentration that could lead to excessive fiber reaction, thereby facilitating the formation of a structurally uniform fractal fiber network. Therefore, the liquor ratio setting here is not problematic.

[0025] In step 1, blending by manual carding and / or mechanical opening is a conventional technique in the field and is not the focus of this invention's patent protection; therefore, it will not be elaborated upon here.

[0026] In step 1, the drying time is 24-48 hours. The drying method is drum-type hot air drying (temperature 60-100℃) or natural air drying. Finally, the diameter of the functional fibers after alkali treatment is 1-10 μm.

[0027] In a preferred embodiment of the present invention, the dispersant comprises at least one of bacterial cellulose nanofibers, Tween-80, sodium dodecylbenzenesulfonate, fatty alcohol polyoxyethylene ether, hexadecyltrimethylammonium bromide, polyethylene glycol (molecular weight 2000~200000), and sodium polyacrylate; the dispersing aid comprises at least one of tert-butanol, isopropanol, methanol, and glycerol. The concentration of the dispersant in the solution is 0.05wt%~0.1wt%, and the concentration of the dispersing aid is 5wt%~20wt%. If the dispersant concentration is too low, it cannot effectively break the hydrogen bonds and van der Waals forces between fibers, and effective dispersion cannot be achieved. If the dispersant concentration is too high, it affects the subsequent freeze-drying process and directly affects the final pore formation. A concentration of 0.05wt%~0.1wt% is a balanced range that can fully disperse the fibers while avoiding excessive surface-active substances from affecting the structural characteristics of the fibers themselves. The main function of the dispersant is to regulate the polarity of the dispersion system, construct a dispersion environment with a polarity similar to that of the blended fibers, and effectively promote the dispersion and deagglomeration of the fibers. The determination of the concentration range of 5wt%~20wt% is based on two principles: (1) The addition of the dispersant can effectively optimize the dispersion performance of the blended fibers, thereby obtaining a thermal aerogel with a uniform microstructure; (2) The addition of the dispersant should not significantly change the critical temperature and critical pressure of the dispersion medium. Otherwise, the dispersion medium will not sublimate sufficiently during the freeze-drying process, and the pore structure will easily collapse, affecting the thermal insulation performance of the final material. The solvent of the solution containing the dispersant and the dispersant aid is water.

[0028] In a preferred embodiment of the present invention, the solid content of the fiber (blended system + dispersant (when the dispersant is fiber)) in the suspension is 0.05%~0.8%.

[0029] In a preferred embodiment of the present invention, the stirring conditions are set as follows: stirring at 380W power for 0 to 30 minutes, and the stirring time is not 0.

[0030] In a preferred embodiment of the present invention, the freeze-drying conditions are set as follows: temperature -60℃, pressure 1 Pa, time 48 h; the heat-setting temperature is 130℃, and the time is 10 min to 1 h. The main purpose of heat setting is to utilize the melting of ES fibers for fiber bonding and structural shaping. Therefore, the temperature is set to 130℃, which is slightly higher than the melting point of the ES fiber sheath (PE) but lower than the melting point of the core layer (PP), to promote controlled local melting of the ES fiber sheath and functional fibers at the fiber intersections and form a thermal bond, thereby achieving stable shaping of the fiber network. If the temperature is too low (<130℃), the temperature during the shaping process will be insufficient, and the thermal bonding between fibers cannot be fully activated, resulting in weak bonding between fibers. This makes them prone to deformation or breakage during subsequent use, thereby affecting the stability of the pore structure and ultimately affecting the thermal insulation effect of the aerogel. However, excessively high temperatures (>130℃) can easily trigger excessive melting or degradation of fiber materials, causing the fiber structure to lose its fractal properties, resulting in the collapse of the pore structure and affecting the mechanical strength of the fiber and the final aerogel properties.

[0031] The second aspect of this invention provides a down-like fractal structure thermal insulation aerogel prepared according to the above-described preparation method. This down-like fractal structure thermal insulation aerogel possesses a triple fractal network of "main trunk-branch-small branches," mimicking the porous fractal network formed by down, effectively inhibiting heat conduction. Compared to thermal insulation materials prepared by existing technologies (such as CN120680790A and CN116100873A), which exhibit microstructural characteristics due to fibers of varying fineness, it possesses high mechanical resilience, extreme lightweight, and strong processability. It ensures a certain degree of uniform density of pores and efficient storage of static air, thereby effectively meeting the application needs in the field of thermal insulation.

[0032] The third aspect of this invention provides the application of the above-mentioned down-like fractal structure thermal insulation aerogel in the preparation of thermal insulation materials.

[0033] The mechanism of this invention is as follows: This invention prepares a lightweight, warm, and porous down-like fractal aerogel, requiring two conditions to be met: First, the rational design of the mixed system components and the precise control of the optimal ratio between each component. Supporting fibers (ES fibers) are selected as the structural skeleton, utilizing their thermal melting properties to achieve molten bonding between fibers at a specific temperature. This further enhances the fractal structural stability based on physical entanglement, thereby effectively improving the material's mechanical properties. Introducing functional fibers of different diameters and treating them with alkaline solutions to form ultrafine fibers of different diameters or to induce fibrillation on the fiber surface promotes interweaving and entanglement between fibers, significantly increasing the number of pores and creating a hierarchical structure based on the existing porous structure. The final component ratio needs to be synergistically optimized for bulkiness and entanglement density, thereby maximizing the control of the material's porosity and pore size distribution. Second, the precise control of the uniformity of the fiber suspension before freeze-drying is crucial. Primary fiber dispersion is achieved by introducing a dispersant, followed by further enhancement of dispersion quality using dispersing aids. These aids weaken hydrogen bonds and van der Waals forces between fibers, promoting the deagglomeration of fiber clusters. Simultaneously, due to their high freezing point and the ability to form fine needle-like crystals during freezing, they can construct micro-ice crystal templates during subsequent freeze-drying, inhibiting the formation of large ice crystals and thus avoiding mechanical damage to the fiber network structure, ensuring uniform fiber distribution in three-dimensional space. Finally, the synergistic effect of mechanical stirring achieves a highly uniform fiber distribution in the suspension. Insufficient suspension uniformity will lead to disruption of fiber distribution continuity, increased local density differences, and consequently, non-uniformity of heat conduction paths, ultimately impairing the overall thermal insulation performance and heat retention stability of the aerogel.

[0034] Unless otherwise specified, the technical solutions described in this invention are all conventional solutions in the field, and the reagents or raw materials used are all purchased from commercial channels or are publicly available unless otherwise specified.

[0035] The ES fiber used in this embodiment of the invention was purchased from Hubei Botao Synthetic Fiber Co., Ltd., and is a PE / PET composite fiber with a specific heat shrinkage rate of 2%~3%. The polyester / polyester island-island fiber with an island phase diameter of 5~6μm after fiber opening was purchased from Jiangsu Jiejie Microfiber Technology Group Co., Ltd., with 16 and 24 island phases, and a sea phase to island phase mass ratio of (25~35):(65~75). The polyester / polyester island-island fiber with an island phase diameter of 2~3μm after fiber opening was purchased from Mingxin Xuteng New Material Co., Ltd., which is a typical island-island composite fiber with 37 and 19 island phases, and a sea phase to island phase mass ratio of (10~30):(70~90). The number of island phases is higher than that of the above 5~6μm island-island fiber. The bacterial cellulose nanofiber was purchased from Guilin Qihong Technology Co., Ltd., and is mainly an aqueous dispersion with a solid content of 0.8% water uniform dispersion.

[0036] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0037] Example 1 A method for preparing a down-like fractal structure thermal insulation aerogel includes the following steps: Step 1: The island-island fibers are treated with an alkali process to obtain polyester / polyester island-island fibers with island phase diameters of 2.1μm and 5.5μm. The specific process is as follows: the concentration of NaOH solution is 20g / L, the time is 1h, the temperature is 96℃, and the bath ratio is 1:100; the treated fibers are thoroughly washed with deionized water until neutral to remove residual alkali solution; after being dried by drum hot air (80℃) in sequence, the two fibers are mixed with ES fibers (diameter of 11.8μm) in a certain proportion. The mixing mass ratio is ES fiber: polyester / polyester island-island fiber with island phase diameter of 5.5μm: polyester / polyester island-island fiber with island phase diameter of 2.1μm = 3:3.5:3.5, finally obtaining a blend system composed of 11.8μm ES fiber, 5.5μm polyester and 2.1μm polyester.

[0038] Step 2: The blend system obtained in Step 1 was dispersed in an aqueous solution containing bacterial cellulose nanofibers (0.1% wt) and tert-butanol (20% wt), wherein the solid content of the blend system and bacterial cellulose nanofibers was 0.5%. The system was mixed to a uniform viscous dispersion (suspension) using a high-power mixer (380W, 10 min). The viscous dispersion was then subjected to freeze-drying (-60℃, 1 Pa, 48 h) and heat-setting (oven temperature 130℃, 1 h) to finally obtain a down-like fractal structure thermal aerogel (down-like fractal structure thermal aerogel, abbreviated as: aerogel). The aerogel density was 0.0176 g / cm³. 3 .

[0039] Figure 1 An optical photograph of the down-like fractal structure thermal aerogel prepared in Example 1; by Figure 1 It can be seen that the prepared aerogel exhibits a macroscopic morphology with uniform and regular shape, fluffy volume, complete structure, and good self-support.

[0040] Figure 2 Scanning electron microscope images of the down-like fractal structure thermal aerogel prepared in Example 1 at different magnifications; (The images are from...) Figure 2 It can be seen that the aerogel exhibits a porous structure, and the aerogel network has a "trunk-branch-small branch" structure similar to down.

[0041] Figure 3Compression cycle curve (1000 cycles) of the down-like fractal structure thermal aerogel prepared in Example 1; Figure 3 It can be seen that the aerogel exhibits good elastic recovery behavior during multiple compression cycles, and its stress-strain curve remains basically consistent during the cycle without significant attenuation.

[0042] Figure 4 The image shows the infrared imaging effect of the down-like fractal structure thermal aerogel prepared in Example 1; the infrared imager shows that the aerogel can achieve a thermal insulation temperature difference of up to 8.0℃ for human skin.

[0043] Example 2 A method for preparing a down-like fractal structure thermal insulation aerogel includes the following steps: Step 1: The island-island fibers are treated with an alkali process to obtain polyester / polyester island-island fibers with island phase diameters of 2.1μm and 5.5μm. The specific process is as follows: the concentration of NaOH solution is 20g / L, the time is 1h, the temperature is 96℃, and the bath ratio is 1:100; the treated fibers are thoroughly washed with deionized water until neutral to remove residual alkali solution; after being dried by drum hot air (80℃) in sequence, the two fibers are mixed with ES fibers (diameter of 11.8μm) in a certain proportion. The mixing mass ratio is ES fiber: polyester / polyester island-island fiber with island phase diameter of 5.5μm: polyester / polyester island-island fiber with island phase diameter of 2.1μm = 3:3.5:3.5, finally obtaining a blend system composed of 11.8μm ES fiber, 5.5μm polyester and 2.1μm polyester.

[0044] Step 2: The blend system obtained in Step 1 was dispersed in an aqueous solution containing bacterial cellulose nanofibers (0.1% wt) and tert-butanol (20% wt), wherein the solid content of the blend system and bacterial cellulose nanofibers was 0.2%. The system was mixed to a uniform viscous dispersion (suspension) using a high-power mixer (380 W, 10 min). The viscous dispersion was then subjected to freeze-drying (-60℃, 1 Pa, 48 h) and heat-setting (oven temperature 130℃, 1 h) to finally prepare a down-like fractal structure aerogel (down-like fractal structure aerogel, abbreviated as: aerogel). SEM observation revealed a down-like "trunk-branch-small branch" structure in the aerogel network prepared in this embodiment, with an aerogel density of 0.0152 g / cm³. 3 Infrared imaging revealed that aerogel can provide a temperature difference of up to 6.5°C for heat insulation of human skin.

[0045] Example 3 The only difference from Example 1 is that in step 1, the mass ratio of ES fibers: polyester / polyester island-island fibers with island phase diameters of 5-6 μm: polyester / polyester island-island fibers with island phase diameters of 2-3 μm is 3:0.7:6.3; all other steps and parameters are the same as in Example 1. SEM observation revealed that the aerogel network prepared in this example has a down-like "trunk-branch-small branch" structure, and the aerogel density is 0.0165 g / cm³. 3 Infrared imaging revealed that aerogel can provide a temperature difference of up to 6.0℃ for heat insulation of human skin.

[0046] Example 4 The only difference from Example 1 is that in step 1, the mass ratio of ES fibers: polyester / polyester island-island fibers with an island diameter of 5.5 μm: polyester / polyester island-island fibers with an island diameter of 2.1 μm is 3:2.1:4.9; all other steps and parameters are the same as in Example 1. SEM observation revealed that the aerogel network prepared in this example has a down-like "trunk-branch-small branch" structure, and the aerogel density is 0.0153 g / cm³. 3 Infrared imaging revealed that aerogel can provide a temperature difference of up to 7.1°C for heat insulation of human skin.

[0047] Comparative Example 1 The only difference from Example 1 is that the addition of polyester / polyester island-island fibers with an island diameter of 5.5 μm was omitted, and the mass ratio of ES fibers to polyester / polyester island-island fibers with an island diameter of 2.1 μm was 5:5; all other steps and parameters were the same as in Example 1. SEM revealed that the aerogel network prepared in this comparative example had a down-like "trunk-branch-small branch" structure, and the aerogel density was 0.0195 g / cm³. 3 Infrared imaging revealed that aerogel can provide thermal insulation to human skin with a temperature difference of up to 4.3°C.

[0048] Comparative Example 2 The only difference from Example 1 is that the addition of polyester / polyester island-island fibers with an island diameter of 2.1 μm was omitted, and the mass ratio of ES fibers to polyester / polyester island-island fibers with an island diameter of 5.5 μm was 5:5; all other steps and parameters were the same as in Example 1. SEM revealed that the aerogel network prepared in this comparative example had a down-like "trunk-branch-small branch" structure, and the aerogel density was 0.0193 g / cm³. 3 Infrared imaging revealed that aerogel can provide a temperature difference of up to 5.6°C for heat insulation of human skin.

[0049] Comparative Example 3 The only difference from Example 1 is that the addition of polyester / polyester island-island fibers with an island diameter of 2.1 μm was omitted, and the mass ratio of ES fibers to polyester / polyester island-island fibers with an island diameter of 5.5 μm was 3:7; all other steps and parameters were the same as in Example 1. SEM revealed a down-like "trunk-branch-small branch" structure in the aerogel network prepared in this comparative example. The aerogel density was 0.0185 g / cm³, and infrared imaging showed that the aerogel provided thermal insulation to human skin with a temperature difference of up to 5.1℃.

[0050] The density, 500-cycle stress retention rate, and infrared imaging thermal insulation temperature difference (ΔT / °C) of Examples 1-4 and Comparative Examples 1-3 are shown in Table 1.

[0051] Table 1. Density, 500-cycle stress retention rate, and infrared imaging thermal insulation temperature difference (ΔT / °C) of Examples 1-4 and Comparative Examples 1-3.

[0052] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for preparing a down-like fractal structure thermal aerogel, characterized in that, Includes the following steps: Step 1: Mix the supporting fibers and functional fibers and chemically treat them, then dry them with hot air in a drum to obtain a blend system; Step 2: Disperse the blend system in a solution containing a dispersant and a dispersing aid, and stir to obtain a suspension; The suspension was freeze-dried and heat-set to obtain the down-like fractal structure thermal aerogel.

2. The preparation method according to claim 1, characterized in that, In step 1, the supporting fiber is an ES fiber with an average diameter of 8~20μm; the functional fiber is at least one of polyester / nylon island fiber, polyester / polyester island fiber, and polyester fiber.

3. The preparation method according to claim 1, characterized in that, The mass ratio of the supporting fiber to the functional fiber is 1:(1~2.5).

4. The preparation method according to claim 1, characterized in that, The chemical treatment conditions are set as follows: the mixed fibers are soaked in a NaOH solution with a concentration of 7~150g / L for 5min~1h, the soaking temperature is 25~96℃, and the bath ratio is 1:50~200; the blending is carried out by manual carding and / or mechanical opening; the drying time is 24~48h.

5. The preparation method according to claim 1, characterized in that, The dispersant includes at least one of bacterial cellulose nanofibers, Tween-80, sodium dodecylbenzenesulfonate, fatty alcohol polyoxyethylene ether, hexadecyltrimethylammonium bromide, polyethylene glycol, and sodium polyacrylate; the dispersing aid includes at least one of tert-butanol, isopropanol, methanol, and glycerol; the concentration of the dispersant in the solution is 0.05wt%~0.1wt%, and the concentration of the dispersing aid is 5wt%~20wt%.

6. The preparation method according to claim 1, characterized in that, The fiber solid content in the suspension is 0.1% to 0.8%.

7. The preparation method according to claim 1, characterized in that, The stirring conditions are set as follows: stirring at 380W power for 0~30min, excluding 0min.

8. The preparation method according to claim 1, characterized in that, The freeze-drying conditions are set as follows: temperature -60℃, pressure 1Pa, time 48h; the heat-setting temperature is 130℃, time 10min~1h.

9. A down-like fractal structure thermal aerogel prepared by the preparation method according to any one of claims 1 to 8.

10. The application of the down-like fractal structure thermal insulation aerogel as described in claim 9 in the preparation of thermal insulation materials.

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