Super-hydrophobic flexible aerogel heat insulation film as well as preparation method and application thereof

Abstract

The invention relates to the technical field of aerogel, and provides a super-hydrophobic flexible aerogel heat insulation film as well as a preparation method and application thereof. The aerogel film comprises aerogel particles subjected to hydrophobic modification treatment and an in-situ fiberized fiber binder, the aerogel particles subjected to hydrophobic modification treatment are wound and anchored by a three-dimensional network structure formed by the in-situ fiberized fiber binder. The aerogel particles subjected to hydrophobic modification treatment and the fiber binder are used as raw materials, a specific process is adopted for processing, a fiber three-dimensional network anchored aerogel particle composite structure is constructed, the problem of aerogel brittleness and the process problem of uniform fibrosis of the fiber binder are solved, and the fiber three-dimensional network anchored aerogel particle composite structure is obtained. The preparation of the aerogel film with excellent comprehensive performance is realized.

Description

Technical Field

[0001] This invention relates to the field of technology, and in particular to a superhydrophobic flexible aerogel insulating film, its preparation method, and its application. Background Technology

[0002] The demand for high-efficiency thermal insulation materials is becoming increasingly urgent in fields such as thermal protection systems for aerospace vehicles, thermal insulation and flame retardancy of new energy power battery packs, thermal management of precision electronic components, thermal insulation materials for special clothing, and building energy conservation. Ideal thermal insulation materials need to have excellent thermal insulation performance (low thermal conductivity), good flexibility, lightweight, and environmental stability (hydrophobicity).

[0003] Therefore, this invention is proposed. Summary of the Invention

[0004] Aerogel materials possess technological advantages such as lightweight and low thermal conductivity due to their extremely high porosity (typically >90%) and nanoporous structure. However, inorganic oxide aerogels (such as silica aerogels) suffer from brittleness, poor toughness, and dust generation, limiting their direct application in scenarios requiring bending, vibration, or external force. Fiber binders are high-performance polymer materials with excellent chemical stability, a wide operating temperature range, and extremely low friction coefficient. More importantly, fiber binders undergo in-situ fibrosis under high temperatures and shear forces, forming an interwoven three-dimensional fiber network structure. This characteristic allows them to be used to construct porous membrane materials that combine flexibility and toughness. However, in the process of combining aerogel materials with fiber binders to prepare flexible films, it has been found that the interfacial bonding between inorganic aerogels and fiber binders is weak, easily separating under stress. Furthermore, the nanoporous structure or pores of the aerogel are easily blocked by the fiber binder, leading to an increase in thermal conductivity and negatively impacting the hydrophobicity of the aerogel material.

[0005] Based on this, the present invention provides a superhydrophobic flexible aerogel insulation film, its preparation method and application. By using hydrophobically modified aerogel particles and in-situ fibrous fiber binders to be composited under a specific ball milling process, it is possible to prepare an aerogel film that has excellent thermal insulation performance (low thermal conductivity), good flexibility and strength, lightweight and environmental stability (hydrophobicity).

[0006] Specifically, in a first aspect, the present invention provides an aerogel film comprising: hydrophobically modified aerogel particles and an in-situ fibrous binder; wherein the in-situ fibrous binder entangles and anchors the hydrophobically modified aerogel particles during the formation of a three-dimensional network structure.

[0007] According to the aerogel film provided by the present invention, the water contact angle of the hydrophobically modified aerogel particles is greater than or equal to 140°. Preferably, the hydrophobic groups of the hydrophobic modified aerogel particles include one or more of silanylmethyl, silanylethyl, and silanylpropyl groups.

[0008] According to the aerogel film provided by the present invention, the particle size of the aerogel particles is at the micro-nano scale; Preferably, the D of the aerogel particles 50 The surface area is 10~100μm, and the specific surface area is 600~1500m². 2 / g; More preferably, the aerogel particles are selected from one or more of the following: silica aerogel particles, alumina aerogel particles, zirconia aerogel particles, titanium dioxide aerogel particles, silica-alumina aerogel particles, silica-titanium dioxide aerogel particles, graphene aerogel particles, and carbon aerogel particles.

[0009] According to the aerogel film provided by the present invention, the hydrophobically modified aerogel particles are obtained by modifying aerogel particles with a hydrophobic modifier; the hydrophobic modifier is selected from hexamethyldisilazane (HMDS), trimethylchlorosilane (TMCS), dimethyldichlorosilane (DMDCS) and methyltrimethoxysilane (MTMS).

[0010] Preferably, the hydrophobically modified aerogel particles are obtained by modifying aerogel particles with a hydrophobic modifier using a liquid-phase method or a gas-phase modification method.

[0011] According to the aerogel film provided by the present invention, the fiber binder is selected from one or more of the following: polytetrafluoroethylene, ethylene-tetrafluoroethylene copolymer, hexafluoropropylene-tetrafluoroethylene copolymer, fluorinated ethylene propylene copolymer, and tetrafluoroethylene-perfluoromethyl vinyl ether copolymer. Preferably, the fiber binder is subjected to in-situ fiberization to form the three-dimensional network structure by mixing, ball milling, and hot pressing.

[0012] According to the aerogel film provided by the present invention, the mass ratio of hydrophobically modified aerogel particles to fiber binder is 70:30 to 97:3.

[0013] In a second aspect, the present invention also provides a method for preparing the aerogel film as described above, comprising: mixing and ball-milling hydrophobically modified aerogel particles and hydrophobic fiber binder particles, followed by hot pressing. The hydrophobic fiber binder particles undergo in-situ fiberization during the mixing and ball milling process, and the in-situ fiber binder extends to form the three-dimensional network structure during the hot pressing process. The ball milling speed of the mixed ball mill is 550~2000 rpm, and the ball milling time is 1~8 min.

[0014] More preferably, the ball milling speed is 1000 rpm and the ball milling time is 2 min.

[0015] According to the preparation method of the aerogel film provided by the present invention, the mixing ball milling uses zirconia grinding beads; preferably, the diameter of the zirconia grinding beads is 3~10mm; more preferably, the diameter of the zirconia grinding beads is 5mm.

[0016] Preferably, the D of the fiber binder particles 50 It is 200~300nm.

[0017] According to the method for preparing the aerogel film provided by the present invention, the hot pressing includes placing the mixed ball-milled product into a two-roll hot press for rolling. Preferably, the roller temperature of the double-roller hot press is 50~130℃, the rolling speed is 0.5~2m / min, and the number of rolling cycles is 1~8.

[0018] Thirdly, the present invention also provides a flexible thermal insulation material, including the aerogel film as described above and the aerogel film prepared by the preparation method as described above; Preferably, the thermal conductivity of the aerogel film is less than or equal to 0.04 W / (m·K). Preferably, the water contact angle of the aerogel film is greater than or equal to 130°; Preferably, the density of the aerogel film is less than or equal to 0.30 g / cm³. 3 And greater than or equal to 0.1 g / cm 3 ; Preferably, the tensile strength of the aerogel film is greater than or equal to 0.5 MPa; Preferably, the aerogel film has a curling angle of 150° or more.

[0019] More preferably, the thermal conductivity of the aerogel film is less than or equal to 0.036 W / (m·K). Water contact angle greater than or equal to 145°; density less than or equal to 0.15 g / cm³ 3 Tensile strength greater than or equal to 0.5 MPa; curling angle greater than or equal to 360°.

[0020] This invention provides a superhydrophobic flexible aerogel insulation film, its preparation method, and its applications. Using hydrophobically modified aerogel particles and a fiber binder as raw materials, and employing a specific process, a composite structure of "fiber three-dimensional network anchoring aerogel particles" is constructed. This solves the problems of aerogel brittleness and the process challenges of uniform fiberization of the fiber binder, achieving the preparation of an aerogel film with excellent comprehensive performance. It achieves extremely low thermal conductivity (0.0296 W / (m·K)), superhydrophobicity (contact angle of 154.92°), good flexibility, and lightweight (ρ=0.1 g / cm³). 3 And tensile strength (>0.6MPa).

[0021] The method of this invention is simple and environmentally friendly. The entire preparation process is a dry process, requiring no solvents and producing no wastewater, thus saving energy and protecting the environment. The process flow is short, the equipment requirements are simple, and it is easy to achieve large-scale production.

[0022] The method and product of this invention have broad application prospects, such as thermal protection systems for aerospace vehicles, heat insulation and flame retardancy of new energy power battery packs, thermal management of precision electronic components, thermal insulation materials for special clothing, and building energy conservation, especially with great advantages in extreme cold, heat or high humidity environments. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0024] Figure 1 This is a surface SEM image of the aerogel film obtained in Example 1.

[0025] Figure 2 This is a photograph of the water contact angle test of the aerogel film obtained in Example 1.

[0026] Figure 3 The tensile properties data are for the aerogel film obtained in Example 1.

[0027] Figure 4 The value represents the thermal conductivity of the aerogel film obtained in Example 1.

[0028] Figure 5 This is a photograph demonstrating the flexibility of the aerogel film obtained in Example 1.

[0029] Figure 6 The images show a comparison of the folding of the aerogel films obtained in Example 1 and Comparative Example 1.

[0030] Figure 7 This is an optical image of the flocculent material obtained after ball milling in Comparative Example 3.

[0031] Figure 8 This is an optical image of the flocculent material obtained after ball milling in Comparative Example 4. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0033] In a specific embodiment of the present invention, an aerogel film is first provided, comprising: hydrophobically modified aerogel particles and an in-situ fibrous binder; the in-situ fibrous binder wraps and anchors the hydrophobically modified aerogel particles during the formation of a three-dimensional network structure.

[0034] In some specific embodiments of the present invention, the water contact angle of the hydrophobically modified aerogel particles is greater than or equal to 140°; for example, it can be any value or a range of values ​​among 140°, 145°, 150°, 155°, and 160°.

[0035] In some specific embodiments of the present invention, the hydrophobic groups of the hydrophobic modified aerogel particles include one or more combinations of silanylmethyl, silanylethyl, and silanylpropyl groups.

[0036] In some specific embodiments of the present invention, the particle size of the aerogel particles is at the micro-nano scale; In some specific embodiments of the present invention, the D of the aerogel particles 50 The surface area is 10~100μm, and the specific surface area is 600~1500m². 2 / g.

[0037] The D of the aerogel particles 50 For example, it can be any value or a range of values ​​from 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, and 100 μm.

[0038] The specific surface area of ​​the aerogel particles can be, for example, 600 m². 2 / g、650m 2 / g、700m 2 / g、750m2 / g、800m 2 / g、900m 2 / g, 1000m 2 / g、1100m 2 / g、1200m 2 / g、1300m 2 / g, 1400m 2 / g, 1500m 2 Any value in / g or a range of data consisting of any values.

[0039] When preparing aerogel films using hot roll forming, the size of the aerogel particles affects the forming effect; the smaller the size, the more difficult the forming process. When combining particles of different sizes, such as D... 50 When using 10μm, 20μm, and 50μm aerogel particles in parallel comparisons for this invention, it was found that when 10μm was used as the raw material, multiple folds were required during the preparation process and powder shedding occurred. When 20~50μm was used as the raw material, the preparation process also required 2~3 folds. When 100μm was used as the raw material, the molding effect was the best, and one-time molding could be achieved.

[0040] In some specific embodiments of the present invention, the aerogel particles are selected from one or more combinations of silica aerogel particles, alumina aerogel particles, zirconia aerogel particles, titanium dioxide aerogel particles, silica-alumina aerogel particles, silica-titanium dioxide aerogel particles, graphene aerogel particles, and carbon aerogel particles.

[0041] To achieve better thermal stability and insulation performance, silica aerogel particles are preferred. The study also found that the silanol groups on the surface of silica aerogel have better reactivity and compatibility with hydrophobic modifiers. Furthermore, silica aerogel is chemically highly inert, compatible with the PTFE preparation environment, and does not introduce side reactions, making it more conducive to obtaining aerogel films with good mechanical properties and hydrophobicity through hot roll forming.

[0042] In some specific embodiments of the present invention, the hydrophobically modified aerogel particles are obtained by modifying aerogel particles with a hydrophobic modifier; the hydrophobic modifier is selected from hexamethyldisilazane (HMDS), trimethylchlorosilane (TMCS), dimethyldichlorosilane (DMDCS) and methyltrimethoxysilane (MTMS).

[0043] Considering that the reaction byproduct of HMDS is ammonia, which is non-corrosive, and that a superhydrophobic aerogel can be obtained without complex washing steps; while chlorosilane modifiers such as TMCS may cause material corrosion due to residual chloride ions, hexamethyldisilazane (HMDS) is preferred in this invention. However, research has found that the surface of the aerogel modified with HMDS is grafted with trimethylsiloxane groups, which have extremely low surface energy. In addition to giving the aerogel superhydrophobicity (contact angle > 150°), this also facilitates the formation of aerogel films with good mechanical properties and hydrophobicity through hot roll forming and composite with fibrous binders.

[0044] In some specific embodiments of the present invention, the hydrophobically modified aerogel particles are obtained by modifying aerogel particles with a hydrophobic modifier using a liquid-phase method or a gas-phase modification method.

[0045] As an example, the process of modifying silica aerogel powder with hexamethyldisilazane (HMDS) using the aforementioned gas-phase modification method includes: (1) Deeply dry the silica aerogel powder to completely remove the physically adsorbed moisture on the surface. The specific process is as follows: spread the powder evenly in a metal tray, ensuring that the layer thickness does not exceed 1 cm; place the tray in a drying oven; set the drying program: heat from room temperature to 120°C at a rate of 3°C / min, and keep the temperature constant for 3 hours; cool to room temperature after drying.

[0046] (2) Place the deeply dried aerogel powder into the first container, and put the HMDS liquid (purity ≥98.5%) into the second container. Place the first and second containers side by side into the vacuum drying oven. Turn on the vacuum pump to evacuate to -0.08MPa, close the vacuum valve, and introduce high-purity nitrogen (purity 99.999%) until the oven returns to normal pressure. Repeat the evacuation-nitrogen filling process 3 times to ensure that the oxygen and moisture content in the oven atmosphere is reduced to extremely low levels. After the atmosphere replacement is completed, raise the temperature to 150℃ at a rate of 3℃ / min and keep the temperature constant for 4 hours. HMDS will quickly vaporize and fill the oven, penetrating into the aerogel powder.

[0047] (3) After the reaction is complete, turn off the heating and let the drying oven cool naturally. When the temperature inside the oven is below 60°C, slowly open the exhaust valve to let the gas inside the oven be discharged into the tail gas absorption device. When the pressure inside the oven is balanced with the atmospheric pressure, open the oven door and take out the hydrophobic modified aerogel powder, which is recorded as hydrophobic modified aerogel particles.

[0048] In some specific embodiments of the present invention, the fiber binder is selected from one or more combinations of polytetrafluoroethylene, ethylene-tetrafluoroethylene copolymer, hexafluoropropylene-tetrafluoroethylene copolymer, fluorinated ethylene propylene copolymer, and tetrafluoroethylene-perfluoromethyl vinyl ether copolymer.

[0049] Studies have found that while fibrous binders possess the ability to stretch and extend under shear force, forming an interwoven fiber network, this specificity is closely related to the molecular chain structure of the polymer. In the in-situ fibrosis process described in this invention, polytetrafluoroethylene (PTFE) exhibits good interfacial compatibility with the hydrophobic modifier, which is more conducive to obtaining aerogel films with good mechanical properties and hydrophobicity. Therefore, PTFE is preferred.

[0050] In some specific embodiments of the present invention, the fiber binder is subjected to in-situ fiberization to form the three-dimensional network structure by a mixed ball milling followed by hot pressing.

[0051] In some specific embodiments of the present invention, the mass ratio of hydrophobically modified aerogel particles to fiber binder is 70:30 to 97:3. For example, it can be any value or a data range consisting of any values.

[0052] Because aerogel powder has an extremely low bulk density and fiber binder has a relatively high bulk density, in this invention, the higher the proportion of fiber binder, the higher the overall density of the resulting aerogel film. High density will lead to a decrease in the thermal insulation performance of the material, an increase in thermal conductivity, and improvements in tensile strength and tensile strain.

[0053] In a specific embodiment of the present invention, a method for preparing the aerogel film as described above is also provided, comprising: mixing and ball-milling hydrophobically modified aerogel particles and hydrophobic fiber binder particles, followed by hot pressing. The hydrophobic fiber binder particles undergo in-situ fiberization during the mixing and ball milling process, and the in-situ fiber binder extends to form the three-dimensional network structure during the hot pressing process. The ball milling speed of the mixed ball mill is 550~2000 rpm, for example, it can be any value or a data range composed of any values ​​from 550 rpm, 600 rpm, 700 rpm, 800 rpm, 900 rpm, 1000 rpm, 1100 rpm, 1200 rpm, 1300 rpm, 1400 rpm, 1500 rpm, 1600 rpm, 1700 rpm, 1800 rpm, 1900 rpm, and 2000 rpm.

[0054] The ball milling time for the mixed ball mill is 1 to 8 minutes. For example, it can be any value or a range of values ​​from 1 min, 2 min, 3 min, 4 min, 5 min, 6 min, 7 min, and 8 min.

[0055] This invention constructs a dual hydrophobic system of hydrophobically modified aerogel particles and hydrophobic fiber binder particles. Since both are hydrophobic interfaces, and in particular, the silane groups on the surface of the aerogel particles and the surface groups of the fiber binder have weak interactions, the compatibility of the inorganic-organic interface is improved, resulting in better interfacial bonding. Based on this, the ball milling parameters of the mixing ball mill are further optimized. It is found that when a high-speed, short-time strategy is used for mixing ball milling, the fiber binder can be in-situ fiberized to form a three-dimensional network structure. This allows the hydrophobically modified aerogel particles to be wrapped and anchored while avoiding the blockage of the nanoporous structure or pores of the aerogel by the fiber binder and the reduction of hydrophobicity. As a result, the aerogel film has excellent thermal insulation performance (low thermal conductivity), lightweight, good flexibility and strength, and environmental stability (superhydrophobicity).

[0056] In this invention, the nanopores of the aerogel itself and the micron-sized pores formed by the fiber network of the fiber binder constitute a micro-nano hierarchical structure. At the same time, the fiber binder itself is a low surface energy material, and the surface energy of the aerogel after hydrophobic modification is also extremely low. The special microstructure after the combination of the two avoids the coating of the fiber binder and exhibits superhydrophobic properties.

[0057] In some specific embodiments of the present invention, the ball milling speed of the mixed ball mill is 800~1200 rpm, and the ball milling time is 1~3 min. More preferably, the ball milling speed of the mixed ball mill is 1000 rpm, and the ball milling time is 2 min.

[0058] In some specific embodiments of the present invention, the mixing ball mill uses zirconia grinding balls; preferably, the diameter of the zirconia grinding balls is 3-10 mm; for example, it can be any value or a range of any values ​​from 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, to 10 mm. More preferably, the diameter of the zirconia grinding balls is 5 mm.

[0059] In some specific embodiments of the present invention, the D of the fiber binder particles 50 The range is 200~300nm. For example, it can be any value or a range of values ​​from 200 nm, 210 nm, 220 nm, 230 nm, 240 nm, 250 nm, 260 nm, 270 nm, 280 nm, 290 nm, and 300nm.

[0060] In some specific embodiments of the present invention, the hot pressing includes placing the mixed ball-milled product into a two-roll hot press for rolling; In some specific embodiments of the present invention, the roller temperature of the double-roller hot press is 50~130℃, the rolling speed is 0.5~2m / min, and the number of rolling cycles is 1~8.

[0061] The roller temperature of the twin-roll hot press can be any value or a range of values, such as 50 ℃, 100 ℃, or 130 ℃.

[0062] The rolling speed of the twin-roll hot press can be any value or a range of values ​​from 0.5 m / min, 0.6 m / min, 0.7 m / min, 0.8 m / min, 0.9 m / min, 1.0 m / min, 1.1 m / min, 1.2 m / min, 1.3 m / min, 1.4 m / min, 1.5 m / min, 1.6 m / min, 1.7 m / min, 1.8 m / min, 1.9 m / min, and 2.0 m / min.

[0063] The number of rolls of the double-roll hot press can be any value or a range of values, such as 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10.

[0064] This invention utilizes a hot roller press to further extend, fuse, and strengthen the initially formed fibers under the combined action of heat and shear force, creating a robust and resilient three-dimensional framework. This framework, like a "bird's nest," encapsulates and anchors the fragile aerogel particles, providing the composite material with excellent mechanical strength and flexibility while maximizing the protection of the aerogel's nanoporous structure, thus preserving its ultra-low thermal conductivity.

[0065] Research has shown that by using aerogel particles and fiber binder particles, both with hydrophobic interfaces, this invention can achieve aerogel film thicknesses of 0.1–5 mm in a single roll forming process. In contrast, aerogel particles without hydrophobic modification cannot achieve this single roll forming.

[0066] The thickness of the aerogel film can be any value or a range of values ​​from 0.1 mm, 0.6 mm, 1.1 mm, 1.6 mm, 2.1 mm, 2.6 mm, 3.1 mm, 3.6 mm, 4.1 mm, 4.6 mm, and 5.0 mm.

[0067] In some specific embodiments of the present invention, a flexible thermal insulation material is also provided, including the aerogel film as described above and the aerogel film prepared by the preparation method as described above; In some specific embodiments of the present invention, the thermal conductivity of the aerogel film is less than or equal to 0.04 W / (m·K). In some specific embodiments of the present invention, the water contact angle of the aerogel film is greater than or equal to 130°; In some specific embodiments of the present invention, the density of the aerogel film is less than or equal to 0.30 g / cm³. 3 And greater than or equal to 0.1 g / cm 3 ; In some specific embodiments of the present invention, the tensile strength of the aerogel film is greater than or equal to 0.5 MPa; In some specific embodiments of the present invention, the curling angle of the aerogel film is 150° or more.

[0068] The products and methods of the present invention will be illustrated below with some specific implementation examples.

[0069] Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in this field, or in accordance with the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased through legitimate channels. The specific surface area of ​​the silica aerogel powder, zirconia aerogel powder, and titanium dioxide aerogel powder involved in the embodiments of this invention is 600~1500 m². 2 Within the range of / g.

[0070] Example 1 This embodiment provides a method for preparing an aerogel film, the steps of which are as follows: (1) Preparation of hydrophobically modified aerogel particles Silica aerogel powder with an average particle size of 100 μm was placed in an HMDS atmosphere and reacted at 150 °C for 6 h to obtain hydrophobically modified aerogel particles. The water contact angle of the hydrophobically modified aerogel particles was about 160°.

[0071] (2) Premixed 97g of the hydrophobic modified aerogel particles obtained in step (1) were mixed with 3g of PTFE powder with an average particle size of 200nm to obtain a mixture.

[0072] (3) Ball milling The mixture obtained in step (2) was placed into a ball mill jar, zirconia grinding beads were added, and the mixture was milled at 1000 rpm for 2 minutes. After the milling was completed, a fluffy flocculent material was obtained.

[0073] (4) Hot pressing The fluffy material obtained in step (3) was placed on the conveyor belt of a two-roller hot press. The roller temperature was set to 130°C and the roller speed to 1 m / min. The press was repeated once. Finally, a uniform and flexible white film with a thickness of about 1 mm was obtained.

[0074] Example 2 The results are basically the same as in Example 1, except for steps (1) to (2), as follows: (1) Preparation of hydrophobically modified aerogel particles Silica aerogel powder with an average particle size of 100 μm was placed in a TMCS atmosphere and reacted at 150 °C for 6 h to obtain hydrophobically modified aerogel particles. The water contact angle of the hydrophobically modified aerogel particles was about 155°.

[0075] (2) Premixed 95g of the hydrophobically modified aerogel particles obtained in step (1) were mixed with 5g of ethylene-tetrafluoroethylene copolymer powder with an average particle size of 200nm to obtain a mixture.

[0076] Example 3 This embodiment provides a method for preparing an aerogel film, the steps of which are as follows: (1) Preparation of hydrophobically modified aerogel particles Zirconia aerogel powder with an average particle size of 50 μm was placed in an HMDS atmosphere and reacted at 150 °C for 6 h to obtain hydrophobically modified aerogel particles. The water contact angle of the hydrophobically modified aerogel particles was about 150°.

[0077] (2) Premixed 90g of the hydrophobically modified aerogel particles obtained in step (1) were mixed with 10g of PTFE powder with an average particle size of 200nm to obtain a mixture.

[0078] (3) Ball milling The mixture obtained in step (2) was placed into a ball mill jar, zirconia grinding beads were added, and the mixture was milled at 1000 rpm for 2 minutes. After the milling was completed, a fluffy flocculent material was obtained.

[0079] (4) Hot pressing The fluffy material obtained in step (3) was placed on the conveyor belt of a two-roller hot press. The roller temperature was set to 100℃ and the roller speed to 1m / min. The press was repeated 3 times. Finally, a uniform and flexible white film with a thickness of about 1mm was obtained.

[0080] Example 4 This embodiment provides a method for preparing an aerogel film, the steps of which are as follows: (1) Preparation of hydrophobically modified aerogel particles Titanium dioxide aerogel powder with an average particle size of 30 μm was placed in a DMDCS atmosphere and reacted at 150 °C for 6 h to obtain hydrophobically modified aerogel particles. The water contact angle of the hydrophobically modified aerogel particles was about 140°.

[0081] (2) Premixed 80g of the hydrophobically modified aerogel particles obtained in step (1) were mixed with 20g of hexafluoropropylene and tetrafluoroethylene copolymer powder with an average particle size of 200nm to obtain a mixture.

[0082] (3) Ball milling The mixture obtained in step (2) was placed into a ball mill jar, zirconia grinding beads were added, and the mixture was milled at 1000 rpm for 2 minutes. After the milling was completed, a fluffy flocculent material was obtained.

[0083] (4) Hot pressing The fluffy material obtained in step (3) was placed on the conveyor belt of a two-roller hot press. The roller temperature was set to 50°C and the roller speed to 1 m / min. The rollers were pressed repeatedly 5 times. Finally, a uniform and flexible white film with a thickness of about 1 mm was obtained.

[0084] Example 5 This embodiment provides a method for preparing an aerogel film, the steps of which are as follows: (1) Preparation of hydrophobically modified aerogel particles Silica aerogel powder with an average particle size of 10 μm was placed in an HMDS atmosphere and reacted at 150 °C for 6 h to obtain hydrophobically modified aerogel particles. The water contact angle of the hydrophobically modified aerogel particles was about 150°.

[0085] (2) Premixed 70g of the hydrophobic modified aerogel particles obtained in step (1) were mixed with 30g of PTFE powder with an average particle size of 200nm to obtain a mixture.

[0086] (3) Ball milling The mixture obtained in step (2) was placed into a ball mill jar, zirconia grinding beads were added, and the mixture was milled at 1000 rpm for 2 minutes. After the milling was completed, a fluffy flocculent material was obtained.

[0087] (4) Hot pressing The fluffy material obtained in step (3) was placed on the conveyor belt of a two-roller hot press. The roller temperature was set to 50°C and the roller speed to 1m / min. The rollers were pressed repeatedly 10 times. Finally, a uniform and flexible white film with a thickness of about 1mm was obtained.

[0088] Comparative Example 1 This comparative example provides a method for preparing an aerogel film, the steps of which are as follows: (1) Premixed A mixture was prepared by mixing 97g of unhydrophobically modified silica aerogel powder with an average particle size of 100μm with 3g of PTFE powder with an average particle size of 200nm.

[0089] (2) Ball mill The mixture obtained in step (1) was placed into a ball mill jar, zirconia grinding beads were added, and the mixture was milled at 1000 rpm for 2 minutes. After the milling was completed, a fluffy flocculent material was obtained.

[0090] (3) Hot pressing The fluffy material obtained in step (2) was placed on the conveyor belt of a two-roller hot press. The roller temperature was set to 130℃ and the roller speed to 1m / min. The rollers were pressed repeatedly 10 times. Finally, a white film with a thickness of about 1mm was obtained.

[0091] Comparative Example 2 It is basically the same as Example 1, except that the ball milling time in step (3) is 10 min.

[0092] Comparative Example 3 The process is basically the same as in Example 1, except that the rotation speed in step (3) is 300 rpm. However, experiments have shown that because the rotation speed is too low and the ball milling time is too short, the heat generated during the ball milling process is insufficient, and the collision between the milling beads and the particles is insufficient to fully fiberize the PTFE particles, resulting in flocculent material (such as...) obtained after ball milling. Figure 7 (As shown) cannot be further rolled.

[0093] Comparative Example 4 The process is basically the same as in Example 1, except that the rotation speed in step (3) is 600 rpm and the ball milling time is 10 min. Experiments have shown that a slower rotation speed and a longer ball milling time result in an excessively high density of flocculent material after ball milling (e.g., ...). Figure 8 As shown in the figure, the film obtained after subsequent rolling has a relatively high density.

[0094] Test case The aerogel films prepared in the examples and comparative examples were subjected to performance tests, wherein... Figures 1-6 The performance photographs of the aerogel film prepared in Example 1 are shown. Figure 1 It can be seen that in the aerogel film prepared in Example 1, there is a structure in which the PTFE fiber network covers the aerogel particles.

[0095] The bending angle test process involves rolling or kneading the material by hand until a crack appears. The folded images of the films in Example 1 and Comparative Example 1 are shown below. Figure 6 As shown.

[0096] Other test results are as follows: Table 1 The data above shows that by optimizing the structure and surface state of aerogel particles and the ball milling parameters, it is possible to achieve extremely low thermal conductivity (0.0296 W / (m·K)), superhydrophobicity (contact angle of 154.92°), good flexibility, and lightweight (ρ=0.1 g / cm³). 3 The preparation of aerogel films with tensile strength (>0.6 MPa) was carried out. Among them, the ball milling parameters played a key role. Long-term ball milling can easily lead to increased density, decreased thermal insulation performance, and decreased hydrophobicity.

[0097] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An aerogel film, characterized in that, include: Hydrophobically modified aerogel particles and in-situ fibrous binder; the in-situ fibrous binder wraps and anchors the hydrophobically modified aerogel particles during the formation of a three-dimensional network structure.

2. The aerogel film according to claim 1, characterized in that, The water contact angle of the hydrophobically modified aerogel particles is greater than or equal to 140°; Preferably, the hydrophobic groups of the hydrophobic modified aerogel particles include one or more combinations of silanylmethyl, silanylethyl, and silanylpropyl groups.

3. The aerogel film according to claim 1 or 2, characterized in that, The aerogel particles have a particle size in the micro-nano range; Preferably, the D of the aerogel particles 50 The surface area is 10~100μm, and the specific surface area is 600~1500m². 2 / g; More preferably, the aerogel particles are selected from one or more of the following: silica aerogel particles, alumina aerogel particles, zirconia aerogel particles, titanium dioxide aerogel particles, silica-alumina aerogel particles, silica-titanium dioxide aerogel particles, graphene aerogel particles, and carbon aerogel particles.

4. The aerogel film according to any one of claims 1 to 3, characterized in that, The hydrophobically modified aerogel particles are obtained by modifying aerogel particles with a hydrophobic modifier; the hydrophobic modifier is selected from hexamethyldisilazane, trimethylchlorosilane, dimethyldichlorosilane and methyltrimethoxysilane. Preferably, the hydrophobically modified aerogel particles are obtained by modifying aerogel particles with a hydrophobic modifier using a liquid-phase method or a gas-phase modification method.

5. The aerogel film according to any one of claims 1 to 4, characterized in that, The fiber binder is made of one or more of the following materials: polytetrafluoroethylene, ethylene-tetrafluoroethylene copolymer, hexafluoropropylene-tetrafluoroethylene copolymer, fluorinated ethylene-propylene copolymer, and tetrafluoroethylene-perfluoromethyl vinyl ether copolymer. Preferably, the fiber binder is subjected to in-situ fiberization to form the three-dimensional network structure by mixing, ball milling, and hot pressing.

6. The aerogel film according to any one of claims 1 to 5, characterized in that, The mass ratio of hydrophobically modified aerogel particles to fiber binder is 70:30 to 97:

3.

7. A method for preparing the aerogel film according to any one of claims 1 to 6, characterized in that, include: Hydrophobically modified aerogel particles and hydrophobic fiber binder particles are mixed, ball-milled, and then hot-pressed. The hydrophobic fiber binder particles undergo in-situ fiberization during the mixing and ball milling process, and the in-situ fiber binder extends to form the three-dimensional network structure during the hot pressing process. The ball milling speed of the mixed ball mill is 550~2000 rpm, and the ball milling time is 1~8 min.

8. The method for preparing the aerogel film according to claim 7, characterized in that, The mixing ball mill uses zirconia grinding balls; preferably, the diameter of the zirconia grinding balls is 3~10mm; Preferably, the D of the fiber binder particles 50 It is 200~300nm.

9. The method for preparing the aerogel film according to claim 7 or 8, characterized in that, The hot pressing includes placing the mixed ball-milled product into a two-roll hot press for rolling; Preferably, the roller temperature of the double-roller hot press is 50~130℃, the rolling speed is 0.5~2m / min, and the number of rolling cycles is 1~8.

10. A flexible thermal insulation material, characterized in that, Includes the aerogel film according to any one of claims 1 to 6, and the aerogel film prepared by the preparation method according to any one of claims 7 to 9; Preferably, the thermal conductivity of the aerogel film is less than or equal to 0.04 W / (m·K). Preferably, the water contact angle of the aerogel film is greater than or equal to 130°; Preferably, the density of the aerogel film is less than or equal to 0.30 g / cm³. 3 And greater than or equal to 0.1 g / cm 3 ; Preferably, the tensile strength of the aerogel film is greater than or equal to 0.5 MPa; Preferably, the aerogel film has a curling angle of 150° or more.

Images