CN115466518B - Organic-inorganic in-situ hybridization aerogel heat insulation material and preparation method thereof - Google Patents
Organic-inorganic in-situ hybridization aerogel heat insulation material and preparation method thereof Download PDFInfo
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Abstract
The invention discloses an organic-inorganic in-situ hybridization aerogel heat insulation material and a preparation method thereof, and relates to the technical field of heat insulation materials. The preparation method of the organic-inorganic in-situ hybridization aerogel heat insulation material comprises the following steps: (1) preparing sol; (2) a gel; (3) drying to prepare aerogel. The method disclosed by the invention is simple in process, short in production period and free of an acid-base catalyst, and the obtained organic-inorganic in-situ hybridization aerogel heat insulation material has high strength, excellent compression retraction elastic energy and heat insulation performance and good temperature resistance, and has a wide application prospect in the heat insulation field.
Description
Technical Field
The invention relates to the technical field of heat insulation materials, in particular to an organic-inorganic in-situ hybridization aerogel heat insulation material and a preparation method thereof.
Background
Aerogel is the solid material with the lowest known density in the world at present and has a typical three-dimensional nano porous network structure, so that the unique structure endows the aerogel with the characteristics of low density, high specific surface area, large porosity and the like, and therefore, the aerogel has excellent performances in the aspects of adsorption, filtration, catalysis, heat insulation, noise reduction and the like. Aerogel materials are of a wide variety, and different types of aerogels can be prepared from different precursors, such as inorganic oxide aerogels, polymer aerogels, biomass aerogels, carbon aerogels, carbide aerogels, semiconductor aerogels, metal aerogels, and the like. Wherein SiO is 2 Aerogel is a novel super heat insulation material which has earliest research and highest application potential, has the normal temperature heat conductivity as low as 0.012W/(m.K), and has huge application potential in the aspects of heat protection of weaponry, thermal management of petrochemical engineering heating pipelines and new energy automobile batteries, heat preservation and heat insulation in logistics transportation and building industries and the like.
SiO 2 Precursor of aerogel is conventionally prepared from organic silicon source such as ethyl orthosilicate and methyl orthosilicate or inorganic silicon source such as sodium silicate and water glass, the precursor forms pearl chain-shaped nano skeleton structure formed by stacking secondary particles connected by chemical bonds formed by inter-particle Van der Waals force and hydroxyl polycondensation through sol-gel reaction, and solvent among the skeleton is removed through drying process to obtain low-density SiO 2 An aerogel. Due to the small contact area between the secondary nanoparticles and the rigid connection of Si-O-Si bonds, siO is caused 2 The nano skeleton structure of the aerogel has lower strength, large brittleness in a macroscopic sense, poor toughness, easy powder and slag falling, and greatly limits SiO 2 Practical application of aerogel. The invention patent with the publication number of CN104402395A discloses a fiber reinforced flexible SiO 2 Aerogel heat insulation material and preparation method thereof, and fiber reinforced flexible SiO is prepared by adopting fiber felt pad as reinforcement 2 The aerogel heat insulation material overcomes the defects of poor mechanical strength, large brittleness and the like of pure aerogel, and can be used as an independent block composite material in practical engineering. However, the method is thatWhereas, micron-sized reinforcement fibers and nanoscale matrix SiO 2 The interfaces between aerogels are generally mismatched, poorly compatible, and fiber reinforcement does not substantially improve SiO 2 The inherent brittleness of aerogel can still be a problem of powder and slag falling.
To improve SiO at the molecular level 2 Intrinsic brittleness of aerogel, some alkoxysilanes containing organic groups are used as novel precursors to prepare organic-inorganic in-situ aerogels, which have improved toughness and even better compression set resilience due to the realization of in-situ crosslinking of organic and inorganic units at the molecular level. The invention patent with the publication number of CN106749378A discloses a mechanical reinforced polysilsesquioxane aerogel, which is characterized in that at least one ureido group capable of forming hydrogen bonds is contained in selected copolymer molecules. The invention patent with the publication number of CN102372851A discloses a bridged polysilsesquioxane aerogel and a preparation method thereof, wherein the bridged polysilsesquioxane aerogel is obtained by carrying out hydrolysis-condensation reaction under an acid catalyst to obtain the bridged polysilsesquioxane sol, and then carrying out gelation, aging and washing, and then extracting by supercritical carbon dioxide to obtain the bridged polysilsesquioxane aerogel. Guoqing Zu et al adopts a free radical polymerization/hydrolysis copolycondensation strategy, and prepares the flexible three-network aerogel based on polyethylene-poly (dimethylsiloxane)/polymethylsilsesquioxane by drying under normal pressure, and the flexible three-network aerogel has high specific surface area, superhydrophobicity, superelasticity, good flexibility and super heat insulation performance [ Chemistry of Materials,2020,32 (4): 1595 ]. However, these methods generally require acid catalysts to promote hydrolysis of the silicon source (e.g., hydrochloric acid, nitric acid, etc.), alkali catalysts to promote polycondensation of the gel (e.g., sodium hydroxide, sodium carbonate, ammonia, etc.), and acid-base catalysts inevitably cause corrosion damage to equipment, and additionally alkoxideThe organic groups in the silane base endow the aerogel with good flexibility, meanwhile, the reactivity of the aerogel is reduced, the sol-gel time is long, the aging modification, solvent replacement and other process steps are generally needed, the process period is long, 6-10 days are needed, a large amount of organic solvents are consumed, and the process is complex.
Therefore, there is still a need for a preparation method with simple process and high efficiency to synthesize organic-inorganic hybrid aerogel with excellent comprehensive properties, which promotes the further application of aerogel in the field of heat insulation.
Disclosure of Invention
Aiming at the problems of complex process, long production period, and particularly the corrosion-prone production equipment of acid-base catalysts and the like in the prior art, the invention provides an organic-inorganic in-situ hybridization aerogel heat insulation material with excellent mechanical properties and heat insulation performance, and a method for preparing the organic-inorganic in-situ hybridization aerogel heat insulation material, which has the advantages of simple process, high efficiency and no need of acid-base catalysts.
In order to achieve the above object, the present invention provides the following solutions:
the invention provides an organic-inorganic in-situ hybridization aerogel heat insulation material, the density of aerogel is 0.08-0.30 g/cm 3 The specific surface area is 210.2-720.8 m 2 The compression strength at 10% strain is 0.4-3.1 MPa, and the thermal conductivity at normal temperature and normal pressure is 0.018-0.029W/(m.K).
The preparation method of the organic-inorganic in-situ hybridization aerogel heat insulation material comprises the following steps:
(1) Preparing sol
Firstly, fully and uniformly stirring an organic solvent and amino bridged siloxane, then adding water (preferably dropwise adding deionized water), and continuously stirring until the mixture is uniform to obtain sol;
(2) Gel
Sealing the sol in the step (1), and standing to obtain gel;
(3) Drying to prepare aerogel
And (3) drying the gel in the step (2) to obtain the organic-inorganic in-situ hybridization aerogel heat insulation material.
According to the preparation method of the organic-inorganic in-situ hybridization aerogel heat insulation material, amino bridged siloxane is used as a silicon source, and the organic-inorganic in-situ hybridization aerogel is prepared through an autocatalysis gel process and a drying process, so that the organic-inorganic in-situ hybridization aerogel material which has a nano porous network skeleton structure and can be compressed and rebounded and contains C-C, C-N, C-Si and Si-O bonds is obtained, and the preparation method has potential application prospects in the heat insulation field.
Further, in the step (1), the organic solvent is one or more of ethanol, methanol, acetone, n-heptane and n-hexane.
Further, in step (1), the amino-bridged siloxane is one or both of bis (3-trimethoxysilylpropyl) amine or bis (3-triethoxysilylpropyl) amine.
Further, in the step (1), the molar ratio of the organic solvent to the amino-bridged siloxane is 6-80, and the molar ratio of the water to the amino-bridged siloxane is 6-15.
Further, in the step (2), the temperature at the time of standing is 30 to 60℃for 0.1 to 24 hours, and the standing in an oven is preferable.
Further, in the step (3), drying means supercritical fluid drying with carbon dioxide, supercritical fluid drying with ethanol or vacuum freeze drying.
Further, the carbon dioxide supercritical fluid drying is to replace the solvent in the gel with ethanol, then place the gel in carbon dioxide supercritical fluid drying equipment, and dry the carbon dioxide supercritical fluid for 12 to 96 hours under the conditions of the pressure of 10 to 20MPa and the temperature of 35 to 55 ℃ after the pressure is increased and the temperature is increased.
Further, the ethanol supercritical fluid drying is to replace the solvent in the gel with ethanol, then place the gel in ethanol supercritical fluid drying equipment, and dry the carbon dioxide supercritical fluid for 12 to 72 hours under the conditions of the pressure of 7 to 10MPa and the temperature of 245 to 265 ℃ after the pressure is increased and the temperature is increased.
Further, the vacuum freeze drying is to replace the organic solvent in the gel with deionized water, pre-freeze the gel at the temperature of-80 to-40 ℃, and then vacuum freeze-dry the gel for 24 to 96 hours at the vacuum degree of 5 to 15Pa and the temperature of-60 to-20 ℃.
In step (1), autocatalytic hydrolysis and polycondensation of the silicon source can be achieved by using an amine-bridged siloxane as the silicon source. The amido in the amido-bridged siloxane has strong electron-withdrawing property, deionized water is added after attack to generate hydroxyl ions, the hydroxyl ions in turn promote the hydrolysis and polycondensation of alkoxy in the amido-bridged siloxane, and the autocatalytic gel is completed under the condition of no acid-base catalyst.
In the step (2), the self-catalytic hydrolysis and polycondensation reaction of the silicon source is rapidly carried out by heat preservation in an oven, the crosslinking of the nano particles is accelerated to form a three-dimensional nano network skeleton structure, the formation of gel is promoted, the sol-gel reaction time is shortened, the reaction degree of siloxane groups is improved by the increase of the temperature, the skeleton structure strength is enhanced, and the prepared organic-inorganic in-situ hybrid aerogel has excellent mechanical properties.
In the step (3), carbon dioxide supercritical fluid drying and ethanol supercritical fluid drying are adopted, so that the influence of capillary force on the nano-skeleton structure in the drying process can be completely eliminated, the material is basically not shrunk, the aerogel structure of the three-dimensional nano-network skeleton can be well maintained, but compared with a vacuum freeze drying process, the cost is higher, and the high-temperature high-pressure dangerous coefficient is large. The vacuum freeze-drying process can lead the solidified deionized water to be sublimated into a gas state directly, and the problem that the pore structure is damaged by capillary force is solved by changing a gas-liquid interface into a gas-solid interface at low temperature and low pressure, however, the deionized water can generate certain volume expansion in the solidification process, and can generate certain damage to the skeleton structure of the organic-inorganic in-situ hybrid aerogel, so that the strength of the aerogel is reduced, and the microscopic aperture of the organic-inorganic in-situ hybrid aerogel prepared by vacuum freeze-drying is generally in a micron level.
Compared with the prior art, the invention has the following advantages:
1. the preparation method of the organic-inorganic in-situ hybridization aerogel heat insulation material provided by the invention adopts amino bridged siloxane as a silicon source, has high reaction activity, can self-catalyze gel without adding an acid-base catalyst, has short production period, simple process and high production efficiency, and solves the problem that equipment is easy to corrode caused by the acid-base catalyst in the traditional process. Compared with the traditional preparation method with the production period as long as 6-10 days, the preparation method provided by the invention has the period of 1-5 days.
2. According to the preparation method of the organic-inorganic in-situ hybridization aerogel heat insulation material, amino bridged siloxane is used as a silicon source, so that in-situ hybridization crosslinking of organic groups and inorganic groups is realized. The flexible chain segment of the organic group endows the prepared organic-inorganic in-situ hybrid aerogel with good compression retraction elastic energy, and the compression rebound strain can reach 20%. In-situ hybridization of inorganic groups ensures that the prepared organic-inorganic in-situ hybridization aerogel has better temperature resistance and basically keeps stable below 400 ℃.
3. The density of the organic-inorganic in-situ hybridization aerogel heat insulation material provided by the invention is 0.08-0.30 g/cm 3 The specific surface area is 210.2-720.8 m 2 The compression strength under 10% strain is 0.4-3.1 MPa, the thermal conductivity at normal temperature and normal pressure is 0.018-0.029W/(m.K), and the heat insulation performance is good.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are needed in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic process flow diagram of a preparation method of an organic-inorganic in-situ hybridization aerogel heat insulation material provided by the invention.
FIG. 2 is a TG-DTG curve of an organic-inorganic in-situ hybridization aerogel thermal insulation material prepared in example 1 of the present invention.
FIG. 3 is a compressive strain-stress curve of the organic-inorganic in situ hybrid aerogel insulation material prepared in example 1 of the present invention.
FIG. 4 is an infrared spectrum of an organic-inorganic in-situ hybridization aerogel thermal insulation material prepared in example 1 of the present invention.
Detailed Description
Various exemplary embodiments of the invention will now be described in detail, which should not be considered as limiting the invention, but rather as more detailed descriptions of certain aspects, features and embodiments of the invention.
It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. In addition, for numerical ranges in this disclosure, it is understood that each intermediate value between the upper and lower limits of the ranges is also specifically disclosed. Every smaller range between any stated value or stated range, and any other stated value or intermediate value within the stated range, is also encompassed within the invention. The upper and lower limits of these smaller ranges may independently be included or excluded in the range.
Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference for the purpose of disclosing and describing the methods and/or materials associated with the documents. In case of conflict with any incorporated document, the present specification will control.
It will be apparent to those skilled in the art that various modifications and variations can be made in the specific embodiments of the invention described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from consideration of the specification of the present invention. The specification and examples of the present invention are exemplary only.
As used herein, the terms "comprising," "including," "having," "containing," and the like are intended to be inclusive and mean an inclusion, but not limited to.
Example 1
The preparation method of the organic-inorganic in-situ hybridization aerogel heat insulation material is shown in a process flow chart as shown in fig. 1, and specifically comprises the following steps:
(1) Preparing sol
Firstly, fully and uniformly stirring ethanol and bis (3-trimethoxysilylpropyl) amine, then dropwise adding deionized water, and continuously stirring until the mixture is uniform to obtain sol, wherein the raw materials are in the following molar ratio: ethanol: bis (3-trimethoxysilylpropyl) amine=40; deionized water: bis (3-trimethoxysilylpropyl) amine=8;
(2) Gel
Sealing the sol prepared in the step (1), then placing the sol into an oven for standing for 12 hours, taking out the sol, and cooling the sol to obtain gel;
(3) Drying to prepare aerogel
And (3) carrying out carbon dioxide supercritical fluid drying treatment on the gel prepared in the step (2) to prepare the organic-inorganic in-situ hybrid aerogel, wherein the carbon dioxide supercritical fluid drying is carried out by replacing a solvent in the gel with ethanol, then placing the ethanol in carbon dioxide supercritical fluid drying equipment, and carrying out carbon dioxide supercritical fluid drying under the conditions of 10MPa pressure and 45 ℃ for 48 hours after boosting and heating.
The density of the organic-inorganic in-situ hybridization aerogel heat insulation material prepared in the embodiment is 0.18g/cm 3 A specific surface area of 525.8m 2 The compressive strength at 10% strain was 0.8MPa, and the thermal conductivity at ordinary temperature and ordinary pressure was 0.025W/(mK).
The TG-DTG curve of the organic-inorganic in-situ hybridization aerogel heat insulation material prepared by the embodiment is shown in figure 2, which shows that the organic-inorganic in-situ hybridization aerogel heat insulation material has good temperature resistance and basically keeps stable below 400 ℃; the compressive strain-stress curve of the organic-inorganic in-situ hybridization aerogel heat insulation material prepared by the embodiment is shown in fig. 3, which shows that the organic-inorganic in-situ hybridization aerogel heat insulation material has excellent compression retraction elastic energy, and the compressive rebound strain can reach 20%; the infrared spectrum of the organic-inorganic in-situ hybridization aerogel heat insulation material prepared in the embodiment is shown in fig. 4, which shows that the organic-inorganic in-situ hybridization aerogel heat insulation material contains chemical bonds such as C-C, C-N, C-Si and Si-O.
Example 2
The preparation method of the organic-inorganic in-situ hybridization aerogel heat insulation material is shown in a process flow chart as shown in fig. 1, and specifically comprises the following steps:
(1) Preparing sol
Firstly, fully and uniformly stirring acetone and bis (3-triethoxysilylpropyl) amine, then dropwise adding deionized water, and continuously stirring until the mixture is uniform to obtain sol, wherein the raw materials are in the following molar ratio: acetone: bis (3-triethoxysilylpropyl) amine = 60; deionized water: bis (3-triethoxysilylpropyl) amine = 10;
(2) Gel
Sealing the sol prepared in the step (1), then placing the sealed sol into an oven, standing for 24 hours, taking out the sealed sol, and cooling the sealed sol to obtain gel;
(3) Drying to prepare aerogel
And (3) carrying out ethanol supercritical fluid drying treatment on the gel prepared in the step (2) to prepare the organic-inorganic in-situ hybrid aerogel, wherein the ethanol supercritical fluid drying is carried out by replacing a solvent in the gel with ethanol, then placing the solvent in ethanol supercritical fluid drying equipment, and carrying out carbon dioxide supercritical fluid drying under the conditions of 8MPa pressure and 255 ℃ for 60 hours after boosting and heating.
The density of the organic-inorganic in-situ hybridization aerogel heat insulation material prepared in the embodiment is 0.15g/cm 3 Specific surface area of 660.1m 2 The compressive strength at 10% strain was 0.6MPa, and the thermal conductivity at ordinary temperature and pressure was 0.024W/(mK).
Example 3
The preparation method of the organic-inorganic in-situ hybridization aerogel heat insulation material is shown in a process flow chart as shown in fig. 1, and specifically comprises the following steps:
(1) Preparing sol
Firstly, fully and uniformly stirring n-heptane and bis (3-triethoxysilylpropyl) amine, then dropwise adding deionized water, and continuously stirring until the mixture is uniform to obtain sol, wherein the raw materials are in the following molar ratio: n-heptane: bis (3-triethoxysilylpropyl) amine=80; deionized water: bis (3-triethoxysilylpropyl) amine = 6;
(2) Gel
Sealing the sol prepared in the step (1), then placing the sealed sol into an oven, standing for 24 hours, taking out the sealed sol at the oven temperature of 60 ℃, and cooling to obtain gel;
(3) Drying to prepare aerogel
And (3) carrying out carbon dioxide supercritical fluid drying treatment on the gel prepared in the step (2) to prepare the organic-inorganic in-situ hybrid aerogel, wherein the carbon dioxide supercritical fluid drying is carried out by replacing a solvent in the gel with ethanol, then placing the ethanol in carbon dioxide supercritical fluid drying equipment, and carrying out carbon dioxide supercritical fluid drying under the conditions of 12MPa pressure and 45 ℃ for 96 hours after boosting and heating to obtain the organic-inorganic in-situ hybrid aerogel.
The density of the organic-inorganic in-situ hybridization aerogel heat insulation material prepared in the embodiment is 0.08g/cm 3 Specific surface area of 516.7m 2 The compression strength at 10% strain is 0.4MPa, and the thermal conductivity at normal temperature and normal pressure is 0.021W/(m.K).
Example 4
The preparation method of the organic-inorganic in-situ hybridization aerogel heat insulation material is shown in a process flow chart as shown in fig. 1, and specifically comprises the following steps:
(1) Preparing sol
Firstly, fully and uniformly stirring ethanol and bis (3-trimethoxysilylpropyl) amine, then dropwise adding deionized water, and continuously stirring until the mixture is uniform to obtain sol, wherein the raw materials are in the following molar ratio: ethanol: bis (3-trimethoxysilylpropyl) amine=6; deionized water: bis (3-trimethoxysilylpropyl) amine=15;
(2) Gel
Sealing the sol prepared in the step (1), then placing the sol into an oven for standing for 10 hours, taking out the sol, and cooling the sol to obtain gel;
(3) Drying to prepare aerogel
And (3) carrying out ethanol supercritical fluid drying treatment on the gel prepared in the step (2) to prepare the organic-inorganic in-situ hybrid aerogel, wherein the ethanol supercritical fluid drying is carried out by replacing a solvent in the gel with ethanol, then placing the solvent in ethanol supercritical fluid drying equipment, and carrying out carbon dioxide supercritical fluid drying under the conditions of 8MPa pressure and 255 ℃ for 60 hours after boosting and heating.
The density of the organic-inorganic in-situ hybridization aerogel heat insulation material prepared in the embodiment is 0.30g/cm 3 Specific surface area of 253.4m 2 The compression strength at 10% strain was 3.0MPa, and the thermal conductivity at ordinary temperature and ordinary pressure was 0.029W/(mK).
Example 5
The preparation method of the organic-inorganic in-situ hybridization aerogel heat insulation material is shown in a process flow chart as shown in fig. 1, and specifically comprises the following steps:
(1) Preparing sol
Firstly, fully and uniformly stirring n-hexane and bis (3-trimethoxysilylpropyl) amine, then dropwise adding deionized water, and continuously stirring until the mixture is uniform to obtain sol, wherein the raw materials are in the following molar ratio: n-hexane: bis (3-trimethoxysilylpropyl) amine=6; deionized water: bis (3-trimethoxysilylpropyl) amine=15;
(2) Gel
Sealing the sol prepared in the step (1), then placing the sol into an oven for standing for 10 hours, taking out the sol, and cooling the sol to obtain gel;
(3) Drying to prepare aerogel
And (3) performing vacuum freeze drying treatment on the gel prepared in the step (2) to prepare the organic-inorganic in-situ hybrid aerogel, wherein the vacuum freeze drying is to replace normal hexane in the gel with deionized water and pre-freeze the gel at the temperature of-80 ℃, and then performing vacuum freeze drying for 96 hours at the vacuum degree of 5Pa and the temperature of-20 ℃ to obtain the organic-inorganic in-situ hybrid aerogel.
The density of the organic-inorganic in-situ hybridization aerogel heat insulation material prepared in the embodiment is 0.22g/cm 3 Specific surface area of 210.2cm 2 The compression strength at 10% strain was 1.3MPa, and the thermal conductivity at ordinary temperature and ordinary pressure was 0.029W/(mK).
Comparative example 1
The procedure is as in example 1, except that the sol prepared in step (1) is not sealed in the step (2) of gelling, and then is put into an oven at 40 ℃, and the specific procedure is as follows: and (3) sealing the sol prepared in the step (1), and standing at room temperature for 48 hours to obtain the gel.
Because the gel is not put into an oven for heat preservation, the gel time is long, and the strength of the prepared aerogel is low. The density of the organic-inorganic in-situ hybridization aerogel heat insulation material prepared in the comparative example is 0.19g/cm 3 Specific surface area of 375.1m 2 The compression strength at 10% strain was 0.5MPa, and the thermal conductivity at ordinary temperature and ordinary pressure was 0.027W/(mK).
Comparative example 2
The procedure is as in example 1, except that the aerogel is prepared by drying in step (3) at normal pressure (i.e., one atmosphere), and the specific procedure is as follows: and (3) performing normal pressure drying treatment on the gel prepared in the step (2) to prepare the organic-inorganic in-situ hybrid aerogel, wherein the normal pressure drying is to place the gel in an oven, and the organic-inorganic in-situ hybrid aerogel is finally obtained by adopting a mode of gradient heating at 30-40-50-60-70-80-90-100 ℃ and setting each temperature point for 4 hours.
The shrinkage in the gel drying process is serious due to the adoption of normal-pressure drying, the specific surface area is low, and the heat insulation performance is poor. The density of the organic-inorganic in-situ hybridization aerogel heat insulation material prepared in the comparative example is 0.38g/cm 3 Specific surface area of 83.2m 2 And/g, breaking under 4.6% strain, wherein the maximum compressive strength is 3.9MPa, and the normal temperature and normal pressure thermal conductivity is 0.047W/(m.K).
Comparative example 3
The procedure is as in example 1, except that the molar ratio of organic solvent to amino-bridged siloxane is 90 in the sol preparation in step (1), and the specific procedure is as follows: firstly, fully and uniformly stirring ethanol and bis (3-trimethoxysilylpropyl) amine, then dropwise adding deionized water, and continuously stirring until the mixture is uniform to obtain sol, wherein the raw materials are in the following molar ratio: ethanol: bis (3-trimethoxysilylpropyl) amine=90; deionized water: bis (3-trimethoxysilylpropyl) amine=8.
Due to the excessive content of organic solvent, the content of amino-bridged siloxane is too low, resulting in a prepared aerogel with very low strength. The density of the organic-inorganic in-situ hybridization aerogel heat insulation material prepared in the comparative example is 0.05g/cm 3 Specific surface area of 195.8m 2 And/g, breaking under 5.9% strain, wherein the maximum compressive strength is 0.1MPa, and the thermal conductivity at normal temperature and normal pressure is 0.031W/(m.K).
Comparative example 4
The procedure of example 1 is followed except that the sol is prepared in step (1) with a molar ratio of water to amine-bridged siloxane of 16, as follows: firstly, fully and uniformly stirring ethanol and bis (3-trimethoxysilylpropyl) amine, then dropwise adding deionized water, and continuously stirring until the mixture is uniform to obtain sol, wherein the raw materials are in the following molar ratio: ethanol: bis (3-trimethoxysilylpropyl) amine=40; deionized water: bis (3-trimethoxysilylpropyl) amine=16.
Due to the fact that the water content is too high, the amino bridged siloxane hydrolysis polycondensation reaction occurs too fast, gel is uneven, the strength of the prepared aerogel is low, and the thermal conductivity of the prepared aerogel is poor. The density of the organic-inorganic in-situ hybridization aerogel heat insulation material prepared in the comparative example is 0.21g/cm 3 Specific surface area of 427.6m 2 The compressive strength at 10% strain was 0.6MPa, and the thermal conductivity at ordinary temperature and ordinary pressure was 0.027W/(mK).
The above embodiments are only illustrative of the preferred embodiments of the present invention and are not intended to limit the scope of the present invention, and various modifications and improvements made by those skilled in the art to the technical solutions of the present invention should fall within the protection scope defined by the claims of the present invention without departing from the design spirit of the present invention.
Claims (10)
1. An organic-inorganic in-situ hybridization aerogel heat insulation material,characterized in that the density of the aerogel is 0.08-0.30 g/cm 3 The specific surface area is 210.2-720.8 m 2 The compression strength at 10% strain is 0.4-3.1 MPa, and the thermal conductivity at normal temperature and normal pressure is 0.018-0.029W/(m.K).
2. A method for preparing the organic-inorganic in-situ hybridization aerogel heat insulation material according to claim 1, which comprises the following steps:
(1) Preparing sol
Firstly, fully and uniformly stirring an organic solvent and amino bridged siloxane, then adding water, and continuously stirring until uniform to obtain sol;
(2) Gel
Sealing the sol in the step (1), and standing to obtain gel;
(3) Drying to prepare aerogel
And (3) drying the gel in the step (2) to obtain the organic-inorganic in-situ hybridization aerogel heat insulation material.
3. The method according to claim 2, wherein in the step (1), the organic solvent is one or more of ethanol, methanol, acetone, n-heptane and n-hexane.
4. The method of claim 2, wherein in step (1), the amino-bridged siloxane is one or both of bis (3-trimethoxysilylpropyl) amine or bis (3-triethoxysilylpropyl) amine.
5. The process according to claim 2, wherein in step (1), the molar ratio of the organic solvent to the amino-bridged siloxane is 6 to 80 and the molar ratio of water to the amino-bridged siloxane is 6 to 15.
6. The process according to claim 2, wherein in the step (2), the temperature at the time of standing is 30 to 60℃for 0.1 to 24 hours.
7. The method according to claim 2, wherein in the step (3), the drying means supercritical carbon dioxide fluid drying, supercritical ethanol fluid drying or vacuum freeze drying.
8. The method according to claim 7, wherein the supercritical carbon dioxide fluid drying is carried out by replacing the solvent in the gel with ethanol, placing the solution in a supercritical carbon dioxide fluid drying device, raising the pressure and temperature under 10-20 MPa and at 35-55deg.C, and drying the supercritical carbon dioxide fluid for 12-96 h.
9. The method according to claim 7, wherein the supercritical fluid drying of ethanol is carried out by replacing the solvent in the gel with ethanol, placing the gel in supercritical fluid drying equipment of ethanol, raising the pressure and temperature, and drying the supercritical fluid of carbon dioxide for 12-72 h under the conditions of pressure of 7-10 MPa and temperature of 245-265 ℃.
10. The method according to claim 7, wherein the vacuum freeze-drying is performed by replacing the organic solvent in the gel with deionized water, pre-freezing at a temperature of-80 to-40 ℃ and vacuum freeze-drying at a vacuum of 5 to 15Pa and a temperature of-60 to-20 ℃ for 24 to 96 hours.
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