A method for preparing a thermal self-bonding fiber aerogel and applications thereof

Abstract

The application discloses a preparation method of a thermal self-adhesion fiber aerogel and application thereof, and the preparation method comprises the following steps: (1) an outer layer polymer solution and an inner layer polymer solution are respectively filled into syringes, the syringes are connected with coaxial spinning devices, the syringes are pushed to make the spinning solutions pass through the coaxial spinning devices and push into a receiving device of a low-temperature alcohol solution, and then the skin-core structure heterogeneous fibers are collected, drawn, cleaned, dried and obtained; (2) the skin-core structure heterogeneous fibers are dispersed in a solution system to obtain a fiber homogeneous dispersion liquid; and (3) the fiber homogeneous dispersion liquid is sequentially subjected to cold molding, freeze drying, thermal pretreatment and polydimethylsiloxane treatment to obtain the fiber aerogel. The fibers are connected by self-adhesion, and the influence of an adhesive on the micro-morphology and physical and chemical properties of the fibers is avoided. The compression mechanical properties of the aerogel are excellent, the micro-macro structure of the aerogel is controllable, and the overall structure and performance of the aerogel are stable.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of fiber aerogel, and particularly relates to a preparation method of a thermal self-bonding fiber aerogel and application thereof. BACKGROUND

[0002] Aerogel is known as "blue smoke" or "solid smoke", which is a super-light, porous new type of nanomaterial, and has excellent properties such as high specific surface area, high porosity, low density, super-high thermal insulation performance, ultra-low dielectric constant and low refractive index, and has broad application prospects in thermal insulation, energy saving and environmental protection, petroleum chemical industry, drug release, aerospace and other fields. The current market aerogel gradually moves out of the military, and matures in the industrial and civil markets, and its product application forms are also diverse, including aerogel particles, aerogel felt, aerogel cloth, aerogel film, aerogel coating, aerogel fiber and aerogel board.

[0003] The material made of aerogel usually has problems such as poor mechanical properties, easy to be brittle, and easy to collapse of the structure of aerogel in the application process. The preparation process of the aerogel reported at present usually uses a bonding agent to enhance the compression mechanical properties of the aerogel, and has the following disadvantages: (1) different aerogels have specific requirements for the type of bonding agent; (2) the use amount of the bonding agent is required to be relatively strict in the preparation of the aerogel, the use amount of the bonding agent is large, and the bonding agent is easy to cover the surface of the fiber, changing the micro-morphology and physical and chemical properties of the fiber surface.

[0004] In view of the rapid development of the aerogel material and the preparation technology at present, it is urgent to research a preparation method of a fiber aerogel, so that the prepared aerogel can overcome the defects of unstable structure and poor mechanical properties of the existing aerogel. SUMMARY

[0005] The technical problem to be solved by the present application is to provide a thermal self-bonding fiber aerogel preparation and application, and the aerogel forming process does not add a bonding agent, the microstructure / macromolecular structure of the aerogel is controllable, the compression mechanical properties of the aerogel are excellent, and the overall structure is stable.

[0006] Therefore, the present application provides a thermal self-bonding fiber aerogel preparation method, which comprises the following steps:

[0007] (1) The outer layer polymer solution and the inner layer polymer solution are respectively filled into syringes, the syringes are connected with a coaxial spinning device, the syringes are pushed to make the spinning solution pass through the coaxial spinning device and push into a receiving device of a low-temperature alcohol solution, and then the skin-core structure heterogeneous fiber is obtained through collection, drawing, cleaning and drying;

[0008] (2) The skin-core structure heterogeneous fiber is dispersed in a solution to obtain a fiber homogeneous dispersion liquid;

[0009] (3) the fiber homogeneous dispersion liquid is successively freeze formed, freeze dried, heat pretreated and treated by polydimethylsiloxane (PDMS) to obtain the fiber aerogel.

[0010] Preferably, in the step (1), the polymer comprises at least one of polysulfonamide, polyhydroxyalkanoate, polylactic acid, polyurethane and polysulfone.

[0011] Preferably, in the step (1), the mass fraction of the outer polymer solution of the coaxial spinning is greater than or equal to 15.0%, and the mass fraction of the core polymer solution is less than 15.0%.

[0012] Preferably, in the step (1), the core layer of the cross-section of the skin-core structure heterogeneous fiber is a fiber network structure composed of nanofibers, and the skin layer is a solid structure or a discontinuous hole structure.

[0013] Preferably, in the step (1), the diameter of the skin-core structure heterogeneous fiber is 0.5 μm-350 μm.

[0014] Preferably, in the step (1), the mass fraction of the low-temperature alcohol solution is 50%-100%; the low-temperature alcohol solution comprises an ethanol solution, a glycol solution and / or a methanol solution; and the temperature of the low-temperature alcohol solution is less than or equal to 10℃.

[0015] Preferably, in the step (2), the solution comprises at least two of water, an alcohol solution and a thermochromic powder.

[0016] Preferably, in the step (2), the alcohol solution in the solution is tert-butyl alcohol; the thermochromic powder has a temperature change range of 30-80℃, and the mass fraction of the thermochromic powder is 1%-20%.

[0017] Preferably, in the step (3), the freeze forming process parameters are: a freeze temperature of-50℃ to-5℃ and a freeze time of 15min-120min; the freeze drying process parameters are: a freeze dryer temperature of-20℃ to-50℃, a freeze drying time of 12h-72h, and a vacuum degree of 0.5Pa-10Pa; the heat treatment temperature is 80-180℃, the heat treatment time is 5min-60min; the polydimethylsiloxane treatment time is 5min-120min, and the treatment temperature is 50-100℃.

[0018] The application also provides applications of the fiber aerogel in the fields of thermal insulation, filtration and separation, biomedical treatment, sound absorption and the like.

[0019] Compared with the prior art, the application has the following advantages and positive effects:

[0020] The preparation process of the thermal self-adhesive fiber aerogel of the present application does not use adhesive, saves a large amount of raw material cost, simplifies the steps of dissolving, blending and the like in the raw material preparation stage, and also omits the solvent replacement and the like before the aerogel is freeze-dried and formed; the fibers are connected by self-adhesion, avoiding the influence of the adhesive on the micro-morphology and physicochemical properties of the fibers. The aerogel prepared by the present application has excellent compression mechanical properties, controllable micro / macro structure, stable overall structure and stable performance.

[0021] Other features and advantages of the present application will become more apparent after reading the specific embodiments of the present application in combination with the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 is the SEM image of the core-skin heterogeneous polyurethane fiber of Example 1 of the present application;

[0023] Figure 2 is the cyclic compression performance curve of the aerogel of Example 1 of the present application;

[0024] Figure 3 is the longitudinal cross-sectional morphology and transverse cross-sectional morphology of the core-skin heterogeneous fiber of Example 2 of the present application;

[0025] Figure 4 is the longitudinal cross-sectional morphology and transverse cross-sectional morphology of the solid fiber of Comparative Example 1 of the present application;

[0026] Figure 5 is the tensile stress curve of the core-skin heterogeneous fiber of Example 2 of the present application and the solid fiber of Comparative Example 1. DETAILED DESCRIPTION

[0027] The present application will be further described below in combination with specific examples. These examples are only used to illustrate the present application and not used to limit the scope of the present application. Meanwhile, after reading the content of the present application, those skilled in the art can make various modifications or changes to the present application, and these equivalent forms also fall within the scope defined by the appended claims of the present application.

[0028] The preparation method of the thermal self-adhesive fiber aerogel of the present application comprises the following steps:

[0029] (1) The outer layer polymer solution and the inner layer polymer solution are respectively loaded into syringes, the syringes are connected with the coaxial spinning device, the syringes are pushed to make the spinning solutions pass through the coaxial spinning device and push into the receiving device of the low-temperature alcohol solution, and then the core-skin structure heterogeneous fibers are collected, drawn, washed and dried;

[0030] The polymer includes at least one of polysulfone amide, polyhydroxyalkanoate, polylactic acid, polyurethane and polysulfone.

[0031] By differentiating the mass fraction of the outer layer polymer solution and the mass fraction of the core layer polymer solution in the coaxial spinning, the speed of solvent volatilization from the inside of the fiber can be obviously different, so that the fiber cross-section structure can be made heterogeneous, that is, the skin layer of the fiber is solid or discontinuous hole structure, and the core layer structure of the fiber is three-dimensional network fiberization, and then a stable performance of the skin-core structure heterogeneous fiber can be obtained.

[0032] Specifically, the mass fraction of the outer layer polymer solution is higher than 15.0%, the mass fraction of the core layer polymer solution is lower than 15.0%, and the difference between the mass fraction of the outer layer polymer solution and the mass fraction of the core layer polymer solution is greater than or equal to 10%, which can ensure that a stable performance of the skin-core structure heterogeneous fiber can be obtained.

[0033] The cross-section of the skin-core structure heterogeneous fiber is a fiber network structure composed of nanofibers, and the skin layer is a solid structure or a discontinuous hole structure. The internal structure of the fiber is a porous / nano network structure, which can make the fiber super light. The aerogel prepared by the fiber has a super light volume density compared with the solid fiber of the same diameter.

[0034] Compared with the traditional solid fiber, the skin-core structure heterogeneous fiber used for preparing the fiber aerogel has the following advantages in terms of mechanical properties and structure of the prepared aerogel: the tensile mechanical properties of the hollow fiber are better than those of the traditional solid fiber, and under the condition of the same linear density of single fiber, the skin-core structure heterogeneous fiber used for preparing the fiber aerogel helps to improve the comprehensive mechanical properties of the aerogel. At the same time, the internal pore structure of the fiber and the pore structure between the fibers together improve the porosity of the aerogel, thereby realizing the super lightness of the aerogel while maintaining the stability of the structure of the aerogel.

[0035] The diameter of the skin-core structure heterogeneous fiber is 0.5-350 μm, preferably 0.5-200 μm. The small fiber diameter helps to improve the dispersion uniformity of the fiber in the dispersion liquid when preparing a homogeneous fiber dispersion liquid. The small fiber diameter increases the number of fibers in the aerogel of the same volume, which can improve the comprehensive mechanical properties of the aerogel.

[0036] The low-temperature alcohol solution has a mass fraction of 50% to 100%, and the low-temperature alcohol solution includes an ethanol solution, a glycol solution, and / or a methanol solution; the low-temperature alcohol solution has a temperature of ≤10°C. By controlling the temperature and mass fraction of the alcohol solution, the coagulation speed of the fiber surface can be controlled, the fiber can be quickly shaped, and the fiber surface can be rapidly coagulated, so that a large amount of spinning solvent in the fiber cannot be volatilized out of the fiber in time, the volatilization speed of the solvent from the core layer to the skin layer presents a gradient change, the fiber cross-section structure heterogenization can be realized, that is, the skin layer of the fiber has a solid structure or a discontinuous connected hole structure, and the core layer structure of the fiber is three-dimensional network fiberization, so that a stable performance skin-core structure heterogenization fiber can be obtained.

[0037] (2) dispersing the skin-core structure heterogenization fiber in a solution system to obtain a fiber homogeneous dispersion liquid;

[0038] The solution system includes a water / alcohol solution / thermochromic powder mixed solution, the alcohol solution is t-butanol, the thermochromic powder has a temperature change range of 30-80°C, and the mass fraction of the thermochromic powder is 1%-20%. The solution system can improve the uniform dispersion of the fiber therein, wherein the t-butanol can provide a large amount of H + and OH - , which are combined with the fiber surface to improve the hydrophilicity of the fiber surface, and then the dispersion of the fiber in the solution can be improved; secondly, the thermochromic powder can react with the fiber surface, such as chemical grafting, and after subsequent aerogel forming, the aerogel can present different colors in response to changes in the external environment temperature, which has the function of a temperature sensor. The skin-core structure heterogenization fiber can be uniformly dispersed in the water / alcohol solution / thermochromic powder solution system to obtain a fiber homogeneous dispersion liquid, and then the fiber aerogel can be prepared by freeze forming, freeze drying, and the like, which is beneficial to the formation of a stable structure aerogel.

[0039] (3) sequentially freeze forming, freeze drying, heat pretreatment, and polydimethylsiloxane (PDMS) treatment of the fiber homogeneous dispersion liquid to obtain the fiber aerogel.

[0040] The freeze forming process parameters are: a freeze temperature of -50°C to -5°C and a freeze time of 15 min to 120 min; the freeze drying process parameters are: a freeze dryer temperature of -20°C to -50°C, a freeze drying time of 12 h to 72 h, and a vacuum degree of 0.5 Pa to 10 Pa;

[0041] The heat treatment temperature is 80-180°C, and the heat treatment time is 5 min to 60 min; the selected range of the heat treatment temperature and time enables the fiber to change from a glass state to a high-elasticity state in a short time, the macromolecular chain movement of the fiber surface is accelerated, the surface chain adhesion between the fibers occurs during the heat treatment process, the combination points are generated, the connection between the fibers in the aerogel is improved, and thus the comprehensive mechanical properties of the aerogel can be improved.

[0042] Treatment with polydimethylsiloxane for 5-120 minutes at 50-100℃ can improve the hydrophobic properties of aerogel surfaces. Due to its excellent water resistance and adhesion, polydimethylsiloxane treatment of fibers not only enhances the hydrophobicity of the aerogel surface but also strengthens the bonds between fibers, thereby improving the overall mechanical properties and structural stability of the aerogel.

[0043] The fiber aerogel prepared by the method of the present invention has excellent mechanical properties and stable structure, and can be widely used in fields such as heat insulation, filtration and separation, biomedicine, and sound absorption and insulation. Example 1

[0044] The preparation method of the thermally self-adhesive fiber aerogel in this embodiment includes the following steps:

[0045] (1) Weigh a certain amount of polyurethane masterbatch and dissolve it to prepare polyurethane spinning solutions with mass fractions of 25% and 10%, respectively. Connect the syringe containing the polyurethane spinning solution with a mass fraction of 25% to the outer layer of the coaxial spinning device, and connect the syringe containing the polyurethane spinning solution with a mass fraction of 10% to the inner layer of the coaxial spinning device. Use a 75% ethanol coagulation bath at a temperature of 0°C to perform coaxial spinning and obtain heterogeneous polyurethane fibers with a core-sheath structure.

[0046] The morphology of the core-sheath heterogeneous polyurethane fiber is as follows: Figure 1 As shown, by Figure 1 It can be seen that the fiber cortex has a dense structure, and the core structure is composed of nanofibers with a fiber diameter of about 80 μm.

[0047] (2) Cut the polyurethane fibers into short pieces and disperse them in a mixed solution of water / tert-butanol / thermochromic powder to obtain a fiber dispersion.

[0048] (3) The fiber dispersion was frozen at -20℃ for 120 min, then freeze-dried in a freeze dryer, then heat-treated at 150℃ for 30 min, and treated with polydimethylsiloxane at 50℃ for 30 min to obtain a structurally stable aerogel.

[0049] The compressive mechanical properties curve of the aerogel after 100 cycles of compression is shown in the figure. Figure 2 As shown, by Figure 2 It can be seen that when the compressive strain is 60%, the cyclic compressive stress of the aerogel does not decrease significantly, which indicates that the internal structure of the aerogel remains stable. Example 2

[0050] The preparation method of the thermally self-adhesive fiber aerogel in this embodiment includes the following steps:

[0051] (1) Take a certain amount of polyurethane, polyether sulfone master batch, the mass ratio of polyurethane, polyether sulfone master batch is 7:3, prepare a polyurethane / polyether sulfone spinning solution with a mass fraction of 25%, and load it into the spinning device and connect the outer layer of the coaxial spinning device; take a certain amount of polyurethane and prepare a polyurethane spinning solution with a mass fraction of 10%, and load it into the spinning device and connect the inner layer of the coaxial spinning device. A 75% ethanol coagulation bath with a coagulation bath temperature of 0°C is used for coaxial spinning to prepare a skin-core heterogeneous fiber, and the fiber tensile stress exceeds 200 MPa.

[0052] (2) Cut the polyurethane fiber into short and disperse it in a water / tert-butyl alcohol / thermochromic powder mixed solution to obtain a fiber dispersion solution.

[0053] (3) Freeze the fiber dispersion solution at -20°C for 120 min, then place it in a freeze dryer for freeze drying, then heat treat it at 150°C for 30 min and at 50°C for 30 min with polydimethylsiloxane to obtain a structure-stable aerogel. Example 3

[0054] The preparation method of the thermally self-bonding fiber aerogel of this example includes the following steps:

[0055] (1) Take a certain amount of polyurethane, polyether sulfone master batch, and mix them in a mass ratio of 5:5, prepare a polyurethane / polyether sulfone spinning solution with a mass fraction of 20%, load it into the spinning device and connect the outer layer of the coaxial spinning device; take a certain amount of polyurethane and prepare a polyurethane spinning solution with a mass fraction of 8%, load it into the spinning device and connect the inner layer of the coaxial spinning device. A 100% ethanol coagulation bath with a coagulation bath temperature of -10°C is used for coaxial spinning to prepare a skin-core heterogeneous fiber.

[0056] (2) Cut the polyurethane fiber into short and disperse it in a water / tert-butyl alcohol / thermochromic powder mixed solution to obtain a fiber dispersion solution.

[0057] (3) Freeze the fiber dispersion solution at -20°C for 120 min, then place it in a freeze dryer for freeze drying, then heat treat it at 140°C for 60 min and at 50°C for 30 min with polydimethylsiloxane to obtain a structure-stable aerogel.

[0058] Comparative Example 1

[0059] The preparation method of the thermally self-bonding fiber aerogel of this example includes the following steps:

[0060] (1) A certain amount of polyurethane and polyether sulfone master batch was weighed, the mass ratio of polyurethane and polyether sulfone master batch was 7:3, a polyurethane / polylactic acid spinning solution with a mass fraction of 25% was prepared, and was loaded into a spinning device and connected with the outer layer and the inner layer of the coaxial spinning device. A 75% ethanol coagulation bath was used, the coagulation bath temperature was 0°C, coaxial spinning was carried out, and a solid fiber was obtained.

[0061] (2) The fiber was cut and dispersed in a water / tert-butyl alcohol mixed solution to obtain a fiber dispersion solution.

[0062] (3) The fiber dispersion solution was frozen at -20°C for 120 min, then placed in a freeze dryer for freeze drying, and then heat treated at 150°C for 30 min to obtain an aerogel.

[0063] The fiber prepared in Comparative Example 1 was a solid fiber, and the aerogel of Example 2 and the aerogel of Comparative Example 1 were tested for performance. It was found that the compressive stress of the aerogel prepared in Example 2 was 15-17.5 kPa (when the strain was 80%), and the compressive stress of the aerogel prepared in Comparative Example 1 was 1.52 kPa (when the strain was 80%).

[0064] The surface contact angle of the aerogel prepared in Example 2 reached 140°, and the surface contact angle of the aerogel prepared in Comparative Example 1 was 128°. It can be seen that the aerogel prepared in Example 2 has excellent mechanical properties, stable structure and good hydrophobicity.

[0065] Figure 3 FIG. 1 is a cross-sectional morphology diagram of the core-sheath heterogeneous fiber (hollow fiber) of Example 2, Figure 4 FIG. 2 is a cross-sectional morphology diagram of the solid fiber of Comparative Example 1. The cross section of the hollow fiber of Example 2 has a clear core-sheath structure, and the cross section of the solid fiber of Comparative Example 1 has good uniformity. The average diameter of the fiber obtained under the condition of a 75% ethanol coagulation bath is 74.61 μm. On the longitudinal cross-sectional structure, the hollow structure fiber surface has many grooves, and the solid fiber surface has many grooves formed during the spinning process. On the transverse cross-sectional structure, the core-sheath structure fiber has a clear division between the sheath layer and the core layer, and the holes in the core layer are caused by the fact that the shell layer polyurethane concentration is greater than the core layer. The interface of the solid fiber is irregular.

[0066] Figure 5 FIG. 3 is a mechanical property curve diagram of the core-sheath heterogeneous fiber prepared in Example 2 and the solid fiber prepared in Comparative Example 1. The stress of the two types of fibers exceeds 200 MPa, the strain exceeds 400%, and the tensile mechanical properties of the hollow fiber are better than those of the solid fiber, which is mainly due to the fact that when the internal pores of the hollow fiber are stretched, the pore structure is first deformed and pre-stretched, then the internal molecular chain structure of the fiber is oriented and stretched, and the molecular chains slip, etc., resulting in better tensile mechanical properties of the hollow fiber than those of the solid fiber.

[0067] The above examples are only used to illustrate the technical solutions of the present application, but not to limit the present application; although the present application has been described in detail with reference to the foregoing examples, the technical solutions recorded in the foregoing examples can still be modified, or some of the technical features can be replaced by equivalent features, by those skilled in the art; and these modifications or replacements do not make the corresponding technical solutions deviate from the spirit and scope of the technical solutions claimed by the present application.

Claims

1. A method of making a heat self-bonding fibrous aerogel, characterized by, comprising (1) the outer layer polymer solution and the inner layer polymer solution are respectively filled into the syringe, the syringe is connected with the coaxial spinning device, the syringe is pushed to make the spinning solution pass through the coaxial spinning device and push into the receiving device of low temperature alcohol solution, and then the skin-core structure heterogeneous fiber is collected, drawn, washed and dried; (2) the skin-core structure heterogeneous fiber is dispersed in the solution system to obtain a fiber homogeneous dispersion liquid; (3) the fiber homogeneous dispersion liquid is sequentially frozen, freeze-dried, heat pretreated and treated with polydimethylsiloxane (PDMS) to obtain a fiber aerogel; In step (1), the mass fraction of the coaxial spinning outer layer polymer solution is greater than or equal to 15.0%, and the mass fraction of the inner layer polymer solution is less than 15.0%.

2. The preparation method of the hot self-bonding fiber aerogel according to claim 1, wherein in step (1), the polymer comprises at least one of polysulfonamide, polyhydroxyalkanoate, polylactic acid, polyurethane and polysulfone.

3. The preparation method of the hot self-bonding fiber aerogel according to claim 1, wherein in step (1), the cross section of the skin-core structure heterogeneous fiber is a fiber network structure composed of nanofibers, and the skin layer is a solid structure or a discontinuous hole structure.

4. The preparation method of the hot self-bonding fiber aerogel according to claim 1, wherein in step (1), the diameter of the skin-core structure heterogeneous fiber is 0.5 μm-350 μm.

5. The preparation method of the hot self-bonding fiber aerogel according to claim 1, wherein in step (1), the mass fraction of the low temperature alcohol solution is 50%-100%; the low temperature alcohol solution comprises an ethanol solution, an ethylene glycol solution and / or a methanol solution; and the temperature of the low temperature alcohol solution is less than or equal to 10℃.

6. The preparation method of the hot self-bonding fiber aerogel according to claim 1, wherein in step (2), the solution comprises at least two of water, an alcohol solution and a thermochromic powder.

7. The preparation method of the hot self-bonding fiber aerogel according to claim 6, wherein in step (2), the alcohol solution in the solution is tert-butyl alcohol; the thermochromic powder has a temperature change range of 30-80℃, and the mass fraction of the thermochromic powder is 1%-20%.

8. The preparation method of the hot self-bonding fiber aerogel according to claim 1, wherein in step (3), the freezing molding process parameters are: a freezing temperature of-50℃ to-5℃ and a freezing time of 15min-120min; the freeze-drying process parameters are: a freeze-drying machine temperature of-20℃ to-50℃, a freeze-drying time of 12h-72h and a vacuum degree of 0.5Pa-10Pa; the heat treatment temperature is 80-180℃, and the heat treatment time is 5min-60min; the polydimethylsiloxane treatment time is 5min-120min, and the treatment temperature is 50-100℃.

9. The application of the fiber aerogel prepared by the preparation method of the hot self-bonding fiber aerogel according to claim 1 in the fields of thermal insulation, filtration and separation, biomedical treatment and sound absorption and insulation. ​ ​ ​ ​ ​ ​ ​ ​ ​

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