CN113388152A - Preparation method for preventing monolithic aerogel glass from being cracked - Google Patents
Preparation method for preventing monolithic aerogel glass from being cracked Download PDFInfo
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- CN113388152A CN113388152A CN202110916150.7A CN202110916150A CN113388152A CN 113388152 A CN113388152 A CN 113388152A CN 202110916150 A CN202110916150 A CN 202110916150A CN 113388152 A CN113388152 A CN 113388152A
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- polyvinyl alcohol
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- aerogel glass
- silica sol
- dimethyl sulfoxide
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- 239000004964 aerogel Substances 0.000 title claims abstract description 50
- 239000011521 glass Substances 0.000 title claims abstract description 45
- 238000002360 preparation method Methods 0.000 title claims abstract description 6
- 239000004372 Polyvinyl alcohol Substances 0.000 claims abstract description 80
- 229920002451 polyvinyl alcohol Polymers 0.000 claims abstract description 80
- IAZDPXIOMUYVGZ-UHFFFAOYSA-N Dimethylsulphoxide Chemical compound CS(C)=O IAZDPXIOMUYVGZ-UHFFFAOYSA-N 0.000 claims abstract description 60
- 238000005303 weighing Methods 0.000 claims abstract description 29
- RMAQACBXLXPBSY-UHFFFAOYSA-N silicic acid Chemical compound O[Si](O)(O)O RMAQACBXLXPBSY-UHFFFAOYSA-N 0.000 claims abstract description 24
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 22
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims abstract description 18
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 claims abstract description 14
- 235000011114 ammonium hydroxide Nutrition 0.000 claims abstract description 14
- 239000008367 deionised water Substances 0.000 claims abstract description 13
- 229910021641 deionized water Inorganic materials 0.000 claims abstract description 13
- 238000000352 supercritical drying Methods 0.000 claims abstract description 13
- 238000007710 freezing Methods 0.000 claims abstract description 12
- 230000008014 freezing Effects 0.000 claims abstract description 12
- 238000004108 freeze drying Methods 0.000 claims abstract description 9
- 238000001035 drying Methods 0.000 claims abstract description 8
- 238000013467 fragmentation Methods 0.000 claims abstract description 8
- 238000006062 fragmentation reaction Methods 0.000 claims abstract description 8
- 239000000203 mixture Substances 0.000 claims abstract description 8
- 238000010438 heat treatment Methods 0.000 claims abstract description 7
- 238000003756 stirring Methods 0.000 claims abstract description 7
- 239000003960 organic solvent Substances 0.000 claims abstract description 6
- -1 orthosilicate ester Chemical class 0.000 claims abstract 2
- 239000007788 liquid Substances 0.000 claims description 36
- 238000000034 method Methods 0.000 claims description 31
- 238000002156 mixing Methods 0.000 claims description 30
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 claims description 24
- 239000002243 precursor Substances 0.000 claims description 24
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 16
- 230000008569 process Effects 0.000 claims description 13
- 238000007789 sealing Methods 0.000 claims description 10
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 claims description 4
- BOTDANWDWHJENH-UHFFFAOYSA-N Tetraethyl orthosilicate Chemical compound CCO[Si](OCC)(OCC)OCC BOTDANWDWHJENH-UHFFFAOYSA-N 0.000 claims description 4
- LFQCEHFDDXELDD-UHFFFAOYSA-N tetramethyl orthosilicate Chemical group CO[Si](OC)(OC)OC LFQCEHFDDXELDD-UHFFFAOYSA-N 0.000 claims description 4
- BPQQTUXANYXVAA-UHFFFAOYSA-N Orthosilicate Chemical compound [O-][Si]([O-])([O-])[O-] BPQQTUXANYXVAA-UHFFFAOYSA-N 0.000 claims description 3
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 abstract description 6
- 239000003054 catalyst Substances 0.000 abstract description 2
- 239000000377 silicon dioxide Substances 0.000 abstract 2
- 235000012239 silicon dioxide Nutrition 0.000 abstract 2
- 239000007864 aqueous solution Substances 0.000 abstract 1
- 238000001816 cooling Methods 0.000 abstract 1
- 239000006185 dispersion Substances 0.000 abstract 1
- 238000003780 insertion Methods 0.000 abstract 1
- 230000037431 insertion Effects 0.000 abstract 1
- 239000002994 raw material Substances 0.000 abstract 1
- 239000000499 gel Substances 0.000 description 6
- 238000005054 agglomeration Methods 0.000 description 4
- 230000002776 aggregation Effects 0.000 description 4
- 238000005336 cracking Methods 0.000 description 4
- 239000002270 dispersing agent Substances 0.000 description 4
- 238000004090 dissolution Methods 0.000 description 4
- 238000011049 filling Methods 0.000 description 3
- 239000011229 interlayer Substances 0.000 description 3
- 238000004321 preservation Methods 0.000 description 3
- 238000002834 transmittance Methods 0.000 description 3
- 238000000576 coating method Methods 0.000 description 2
- 238000004134 energy conservation Methods 0.000 description 2
- 238000009413 insulation Methods 0.000 description 2
- 239000002245 particle Substances 0.000 description 2
- 239000000843 powder Substances 0.000 description 2
- 239000000741 silica gel Substances 0.000 description 2
- 229910002027 silica gel Inorganic materials 0.000 description 2
- 238000006136 alcoholysis reaction Methods 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 239000000969 carrier Substances 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000005034 decoration Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 239000012530 fluid Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000002105 nanoparticle Substances 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- 238000000746 purification Methods 0.000 description 1
- 239000011347 resin Substances 0.000 description 1
- 229920005989 resin Polymers 0.000 description 1
- 230000000241 respiratory effect Effects 0.000 description 1
- 238000002791 soaking Methods 0.000 description 1
- 239000011343 solid material Substances 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 239000000758 substrate Substances 0.000 description 1
- 239000005341 toughened glass Substances 0.000 description 1
- 239000011240 wet gel Substances 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
- C08J9/28—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof by elimination of a liquid phase from a macromolecular composition or article, e.g. drying of coagulum
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2201/00—Foams characterised by the foaming process
- C08J2201/04—Foams characterised by the foaming process characterised by the elimination of a liquid or solid component, e.g. precipitation, leaching out, evaporation
- C08J2201/048—Elimination of a frozen liquid phase
- C08J2201/0482—Elimination of a frozen liquid phase the liquid phase being organic
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2201/00—Foams characterised by the foaming process
- C08J2201/04—Foams characterised by the foaming process characterised by the elimination of a liquid or solid component, e.g. precipitation, leaching out, evaporation
- C08J2201/05—Elimination by evaporation or heat degradation of a liquid phase
- C08J2201/0502—Elimination by evaporation or heat degradation of a liquid phase the liquid phase being organic
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2329/00—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an alcohol, ether, aldehydo, ketonic, acetal, or ketal radical; Hydrolysed polymers of esters of unsaturated alcohols with saturated carboxylic acids; Derivatives of such polymer
- C08J2329/02—Homopolymers or copolymers of unsaturated alcohols
- C08J2329/04—Polyvinyl alcohol; Partially hydrolysed homopolymers or copolymers of esters of unsaturated alcohols with saturated carboxylic acids
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K3/00—Use of inorganic substances as compounding ingredients
- C08K3/34—Silicon-containing compounds
- C08K3/36—Silica
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Health & Medical Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Medicinal Chemistry (AREA)
- Polymers & Plastics (AREA)
- Organic Chemistry (AREA)
- Silicon Compounds (AREA)
Abstract
The invention provides a preparation method for preventing monolithic aerogel glass from being cracked, which is characterized in that organic solvent is added into polyvinyl alcohol for dispersion, and the mixture is completely dried at a certain temperature; weighing a proper amount of dried polyvinyl alcohol, and dissolving the polyvinyl alcohol in a dimethyl sulfoxide aqueous solution at a high temperature; taking orthosilicate ester and deionized water as raw materials, taking concentrated hydrochloric acid as a catalyst, adjusting the pH value to 1-4, and standing at constant temperature for a certain time to obtain silica sol; heating the silica sol to a higher temperature, adding the heated silica sol into the dissolved polyvinyl alcohol, uniformly stirring, and cooling to room temperature to form a prepolymer; putting the prepolymer into a low-temperature freezing chamber, freezing and unfreezing for 3-7 times, and immersing the prepolymer into dimethyl sulfoxide containing a small amount of ammonia water until the prepolymer is completely transparent; and finally, carrying out supercritical drying or freeze drying to obtain the complete non-fragmentation aerogel glass. According to the invention, the transparent polyvinyl alcohol gel and the silicon dioxide gel form a network mutual insertion structure, so that the strength of the silicon dioxide gel skeleton is enhanced, and the gel is prevented from being cracked in the drying process.
Description
Technical Field
The invention relates to the field of aerogel preparation methods, in particular to a preparation method for preventing monolithic aerogel glass from being cracked.
Background
The aerogel is a three-dimensional network porous solid material with the porosity of more than 90 percent and formed by clustering nano particles. The aerogel has the characteristics of low density, low heat conduction, high specific surface area and the like, and has great application prospects in the fields of heat preservation and insulation, catalyst carriers, environmental purification and the like.
The aerogel glass is aerogel with higher visible light transmittance, low sun shading coefficient and low heat transfer coefficient, can be used for indoor lighting and building energy conservation and heat preservation, and is applied to indoor decoration.
Chinese patent publication No. CN212053366U discloses a method for installing a respiratory aerogel glass curtain wall, wherein aerogel glass is prepared by filling aerogel powder in a glass interlayer, so that energy conservation and heat preservation are realized; chinese patent publication nos. CN109987861A, CN108060874A, CN109989507A, etc. disclose a scheme for preparing aerogel glass by filling aerogel powder or particles in a hollow glass interlayer and encapsulating, but the aerogel glass prepared by the method has the defects of low light transmittance, high thermal conductivity due to pores between particles, and the like. Patent publication No. CN109502997A divides the whole cover plate into several small units by using parting strips, then fills the wet gel blocks, and then covers the cover plate and presses and dries, and the heat-insulating aerogel glass with high transparency is prepared. Chinese patent publication No. CN108059357A discloses that aerogel glass with good light transmittance is prepared by preparing a mixed gel compounded with resin by an aerogel coating process, and then coating the mixed gel on a toughened glass substrate. There are three main types of aerogel glass currently being produced: a particulate or powdered aerogel filled glass interlayer, aerogel coated glass, and monolithic aerogel glass. The aerogel filling glass and the aerogel coated glass have relatively poor light transmission, heat insulation and other properties. The whole aerogel glass has the best performance, but the structure has poor mechanical property, and is easy to crack and generate cracks.
Disclosure of Invention
In order to solve the above problems, an object of the present invention is to provide a method for preparing monolithic aerogel glass with shatter resistance, in which silica gel and transparent polyvinyl alcohol gel form a three-dimensional network structure with intercalated structures, so as to enhance the skeleton strength of the silica gel, thereby solving the technical problem of the monolithic aerogel glass that is easily broken.
The specific technical scheme is as follows:
a method for preparing monolithic aerogel glass in an anti-fragmentation manner comprises the following steps:
s1, weighing polyvinyl alcohol (PVA) and an organic solvent according to a weight ratio of 1 (1-100), uniformly mixing, and then putting into an oven to completely dry the PVA.
S2, weighing deionized water and dimethyl sulfoxide according to the weight, and uniformly mixing to obtain a solution; the mass fraction of the dimethyl sulfoxide in the solution is 30-100%.
S3, weighing the dried polyvinyl alcohol in the S1 according to the weight, uniformly mixing the dried polyvinyl alcohol with the solution obtained in the S2 to form turbid liquid, sealing the turbid liquid, and then placing the turbid liquid at a high temperature to dissolve the turbid liquid into transparent polyvinyl alcohol liquid; the mass fraction of the polyvinyl alcohol in the turbid liquid is 5-25%.
S4, measuring and uniformly mixing the orthosilicate and the deionized water according to the volume ratio of 1 (1-5), adding a proper amount of concentrated hydrochloric acid, stirring to enable the pH value to be 1-4, and standing at constant temperature for a plurality of hours to obtain the silica sol.
S5, weighing silica sol according to the weight, heating the silica sol to a certain temperature, uniformly mixing the silica sol with the transparent polyvinyl alcohol liquid, and then placing the mixture at room temperature to cool the mixture to form a prepolymer; the weight ratio of the polyvinyl alcohol transparent liquid to the silica sol is 1 (0.5-5).
S6, the prepolymer is placed into a low-temperature refrigerating chamber for freezing, and a plurality of freezing-unfreezing circulation processes are completed to obtain a precursor.
S7, immersing the precursor into a dimethyl sulfoxide solution containing ammonia water until the precursor is completely transparent; the volume ratio of ammonia water to dimethyl sulfoxide in the dimethyl sulfoxide solution is 1 (5-50).
And S8, performing supercritical drying or freeze drying on the precursor processed in the step S7 for a period of time to obtain the monolithic anti-fragmentation aerogel glass.
Further, in step S1, the polyvinyl alcohol is one or two of 1788, 1799, 2488 and 2499, and the organic solvent is one of methanol, ethanol and acetone.
Further, in step S1, the temperature of the oven is set to 40 ℃ to 100 ℃.
Further, in step S3, the high temperature is constant at 70-95 ℃.
Further, in step S4, the orthosilicate is methyl orthosilicate or ethyl orthosilicate.
Further, in step S4, the concentration of the concentrated hydrochloric acid is 37wt%, the constant temperature is 30-70 ℃, and the constant temperature is kept for 0.5-5 h.
Further, in step S5, the silica sol is heated to 70-90 ℃ before being mixed with the transparent liquid of polyvinyl alcohol.
Further, in step S6, the freezing temperature in the low-temperature refrigerating chamber is-40 ℃ to-15 ℃, and the freezing time is 5-24 h; the unfreezing time is 2-10 h; the number of freeze-thaw cycles is 3-8.
Further, in step S8, the supercritical drying is CO2Supercritical drying, setting parameters as follows: the pressure is 8-15MPa, the temperature is 32-60 ℃, and the drying time is 2-10 h; the vacuum degree of the freeze drying is 5Pa-15Pa, the temperature is-50 ℃ to-25 ℃, and the freeze drying is carried out for 5h-24 h.
The polyvinyl alcohol is dispersed in the organic solvent and then dried, so that the polyvinyl alcohol is prevented from being agglomerated and incompletely dissolved in the dissolving process; polyvinyl alcohol with alcoholysis of 88 and 99 is selected to be more easily crosslinked, and the formed gel strength is higher; the water is used as a solvent for preparing the silica sol, so that the formed aerogel glass is more transparent; the polyvinyl alcohol gel strength is higher by adopting the circulating freezing-unfreezing for more than 3 times; the dimethyl sulfoxide solution of ammonia water is used as soaking solution to make the gel more transparent, and dimethyl sulfoxide is easily dissolved in CO2And (4) drying the aerogel glass more completely by using the supercritical fluid.
Detailed Description
The following description of the embodiments of the present invention is provided for illustrative purposes, and other advantages and effects of the present invention will become apparent to those skilled in the art from the present disclosure. The described embodiments are only some embodiments of the invention, not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The first embodiment is as follows: a method for preparing monolithic aerogel glass in an anti-fragmentation manner comprises the following steps:
s1, weighing 20g of polyvinyl alcohol (PVA)1788 and 40g of methanol according to the weight, uniformly mixing, and then putting into a 60 ℃ oven to completely dry the PVA. Methanol is used as an organic dispersant, and after the methanol is uniformly mixed with polyvinyl alcohol (PVA) and heated, dried and volatilized, the polyvinyl alcohol (PVA) can be dispersed, and the agglomeration and incomplete dissolution of the polyvinyl alcohol in the dissolving process are prevented.
S2, weighing 10g of deionized water and 40g of dimethyl sulfoxide according to the weight, and uniformly mixing to obtain a solution for later use.
S3, weighing 10g of polyvinyl alcohol dried in the S1 and 40g of solution obtained in the S2 according to the weight, uniformly mixing the polyvinyl alcohol and the solution to form turbid liquid, sealing the turbid liquid, and then placing the turbid liquid in a constant-temperature water area of 75 ℃ for dissolving for 3 hours to form transparent polyvinyl alcohol liquid.
S4, weighing 30ml of methyl orthosilicate and 30ml of deionized water according to the volume, uniformly mixing, then adding 0.5ml of 37wt% concentrated hydrochloric acid, stirring to enable the pH value to be 3, and standing in a 55 ℃ constant-temperature water bath for 4 hours after sealing to obtain the silica sol.
S5, weighing 50g of silica sol according to the weight, heating to 80 ℃, uniformly mixing with the polyvinyl alcohol transparent liquid, and then placing at room temperature to cool to form a prepolymer.
S6, the prepolymer is placed in a refrigerating chamber at the low temperature of-20 ℃ for freezing for 7 hours, then unfreezing is carried out for 3 hours, and a precursor is obtained through 5 freezing-unfreezing circulation processes.
S7, immersing the precursor into 100ml of dimethyl sulfoxide solution containing a small amount of ammonia water until the precursor is completely transparent; the ammonia water in the dimethyl sulfoxide solution is 5ml, and the dimethyl sulfoxide is 95 ml.
S8, passing the precursor processed in the step S7 through CO2And carrying out supercritical drying to obtain the monolithic anti-cracking aerogel glass with certain strength. Wherein the supercritical drying parameters are set as follows: the pressure is 14MPa, the temperature is 50 ℃, and the drying time is 4 h.
Example two: a method for preparing monolithic aerogel glass in an anti-fragmentation manner comprises the following steps:
s1, weighing 20g of polyvinyl alcohol (PVA)1799 and 60g of ethanol according to the weight, uniformly mixing, and then putting the mixture into a 60 ℃ oven to completely dry the PVA. The ethanol is used as an organic dispersant, and after the ethanol is uniformly mixed with polyvinyl alcohol (PVA) and heated, dried and volatilized, the polyvinyl alcohol (PVA) can be dispersed, and the agglomeration and incomplete dissolution of the polyvinyl alcohol in the dissolving process are prevented.
S2, weighing 10g of deionized water and 40g of dimethyl sulfoxide according to the weight, and uniformly mixing to obtain a solution for later use.
S3, weighing 10g of polyvinyl alcohol dried in the S1 and 40g of solution obtained in the S2 according to the weight, uniformly mixing the polyvinyl alcohol and the solution to form turbid liquid, sealing the turbid liquid, and then placing the turbid liquid in a water area with a constant temperature of 90 ℃ for dissolving for 3 hours to form transparent polyvinyl alcohol liquid.
S4, weighing 30ml of methyl orthosilicate and 30ml of deionized water in volume, uniformly mixing, adding 0.5ml of 37wt% concentrated hydrochloric acid, stirring to enable the pH value to be 4, sealing, and standing in a constant-temperature water bath at 55 ℃ for 4 hours to obtain silica sol.
S5, weighing 50g of silica sol according to the weight, heating to 80 ℃, uniformly mixing with the polyvinyl alcohol transparent liquid, and then placing at room temperature to cool to form a prepolymer.
S6, the prepolymer is placed in a refrigerating chamber at the low temperature of-20 ℃ for freezing for 7 hours, then unfreezing is carried out for 3 hours, and a precursor is obtained through 5 freezing-unfreezing circulation processes.
S7, immersing the precursor into 100ml of dimethyl sulfoxide solution containing a small amount of ammonia water until the precursor is completely transparent; the ammonia water in the dimethyl sulfoxide solution is 5ml, and the dimethyl sulfoxide is 95 ml.
S8, passing the precursor processed in the step S7 through CO2And carrying out supercritical drying to obtain the monolithic anti-cracking aerogel glass with certain strength. Wherein the supercritical drying parameters are set as follows: the pressure is 14MPa, the temperature is 50 ℃, and the drying time is 4 h.
Example three: a method for preparing monolithic aerogel glass in an anti-fragmentation manner comprises the following steps:
s1, weighing 20g of polyvinyl alcohol (PVA)2488 and 60g of methanol according to the weight, uniformly mixing, and then putting the mixture into an oven at 80 ℃ to completely dry the PVA. Methanol is used as an organic dispersant, and after the methanol is uniformly mixed with polyvinyl alcohol (PVA) and heated, dried and volatilized, the polyvinyl alcohol (PVA) can be dispersed, and the agglomeration and incomplete dissolution of the polyvinyl alcohol in the dissolving process are prevented.
S2, weighing 10g of deionized water and 40g of dimethyl sulfoxide according to the weight, and uniformly mixing to obtain a solution for later use.
S3, weighing 10g of polyvinyl alcohol dried in the S1 and 40g of solution obtained in the S2 according to the weight, uniformly mixing the polyvinyl alcohol and the solution to form turbid liquid, sealing the turbid liquid, and then placing the turbid liquid in a water area with a constant temperature of 80 ℃ for dissolving for 3 hours to form transparent polyvinyl alcohol liquid.
S4, weighing 40ml of ethyl orthosilicate and 80ml of deionized water according to the volume, uniformly mixing, then adding 0.6ml of 37wt% concentrated hydrochloric acid, stirring to enable the pH value to be 2, sealing, and standing in a constant-temperature water bath at 55 ℃ for 5 hours to obtain the silica sol.
S5, weighing 90g of silica sol according to the weight, heating to 80 ℃, uniformly mixing with the polyvinyl alcohol transparent liquid, and then placing at room temperature to cool to form the prepolymer.
S6, the prepolymer is placed in a refrigerating chamber at the low temperature of-30 ℃ for freezing for 7 hours, then unfreezing is carried out for 3 hours, and a precursor is obtained through 7 freezing-unfreezing circulation processes.
S7, immersing the precursor into 150ml of dimethyl sulfoxide solution containing a small amount of ammonia water until the precursor is completely transparent; the ammonia water in the dimethyl sulfoxide solution is 10ml, and the dimethyl sulfoxide is 140 ml.
S8, carrying out freeze drying on the precursor processed in the step S7 to obtain the monolithic anti-cracking aerogel glass with certain strength. Wherein the vacuum degree of freeze drying is 8Pa, the temperature is-40 deg.C, and drying is carried out for 24 h.
Example four: a method for preparing monolithic aerogel glass in an anti-fragmentation manner comprises the following steps:
s1, weighing and uniformly mixing 20g of polyvinyl alcohol (PVA)2499 and 60g of ethanol, and then putting the mixture into an oven at 80 ℃ to completely dry the PVA. The ethanol is used as an organic dispersant, and after the ethanol is uniformly mixed with polyvinyl alcohol (PVA) and heated, dried and volatilized, the rest polyvinyl alcohol (PVA) can be dispersed, and the agglomeration and incomplete dissolution of the polyvinyl alcohol in the dissolving process are prevented.
S2, weighing 5g of deionized water and 45g of dimethyl sulfoxide according to the weight, and uniformly mixing to obtain a solution for later use.
S3, weighing 5g of dried polyvinyl alcohol in S1 and 45g of solution obtained in S2 according to the weight, uniformly mixing to obtain turbid liquid, sealing, and then placing in a constant-temperature water area of 95 ℃ for dissolving for 3 hours to form transparent polyvinyl alcohol liquid.
S4, weighing 40ml of ethyl orthosilicate and 40ml of deionized water according to the volume, uniformly mixing, then adding 0.4ml of 37wt% concentrated hydrochloric acid, stirring to enable the pH value to be 1, and standing in a 55 ℃ constant-temperature water bath for 5 hours after sealing to obtain the silica sol.
S5, weighing 50g of silica sol according to the weight, heating to 80 ℃, uniformly mixing with the polyvinyl alcohol transparent liquid, and then placing at room temperature to cool to form a prepolymer.
S6, the prepolymer is placed in a refrigerating chamber at the low temperature of-30 ℃ for freezing for 10 hours, then unfreezing is carried out for 3 hours, and a precursor is obtained through 7 freezing-unfreezing circulation processes.
S7, immersing the precursor into 100ml of dimethyl sulfoxide solution containing a small amount of ammonia water until the precursor is completely transparent; the ammonia water in the dimethyl sulfoxide solution is 10ml, and the dimethyl sulfoxide is 90 ml.
S8, passing the precursor processed in the step S7 through CO2And carrying out supercritical drying to obtain the monolithic anti-cracking aerogel glass with certain strength. Wherein the supercritical drying parameters are set as follows: the pressure is 15MPa, the temperature is 45 ℃, and the drying time is 4 h.
It is to be noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.
The scope of the present invention is not limited to the technical solutions disclosed in the embodiments, and any modifications, equivalent substitutions, improvements, etc. made to the above embodiments according to the technical spirit of the present invention fall within the scope of the present invention.
Claims (9)
1. The preparation method for preventing monolithic aerogel glass from being cracked is characterized by comprising the following steps of:
s1, weighing polyvinyl alcohol (PVA) and an organic solvent according to a weight ratio of 1 (1-100), uniformly mixing, and then putting into an oven to completely dry the polyvinyl alcohol (PVA);
s2, weighing deionized water and dimethyl sulfoxide according to the weight, and uniformly mixing to obtain a solution; the mass fraction of the dimethyl sulfoxide in the solution is 30-100%;
s3, weighing the dried polyvinyl alcohol in the S1 according to the weight, uniformly mixing the dried polyvinyl alcohol with the solution obtained in the S2 to form turbid liquid, sealing the turbid liquid, and then placing the turbid liquid at a high temperature to dissolve the turbid liquid into transparent polyvinyl alcohol liquid; the mass fraction of polyvinyl alcohol in the turbid liquid is 5-25%;
s4, measuring and uniformly mixing orthosilicate ester and deionized water according to the volume ratio of 1 (1-5), adding a proper amount of concentrated hydrochloric acid, stirring to enable the pH value to be 1-4, and standing at constant temperature for a plurality of hours to obtain silica sol;
s5, weighing silica sol according to the weight, heating the silica sol to a certain temperature, uniformly mixing the silica sol with the transparent polyvinyl alcohol liquid, and then placing the mixture at room temperature to cool the mixture to form a prepolymer; the weight ratio of the polyvinyl alcohol transparent liquid to the silica sol is 1 (0.5-5);
s6, putting the prepolymer into a low-temperature refrigerating chamber for freezing to finish a plurality of freezing-unfreezing circulation processes to obtain a precursor;
s7, immersing the precursor into a dimethyl sulfoxide solution containing ammonia water until the precursor is completely transparent; the volume ratio of ammonia water to dimethyl sulfoxide in the dimethyl sulfoxide solution is 1 (5-50);
and S8, performing supercritical drying or freeze drying on the precursor processed in the step S7 for a period of time to obtain the monolithic anti-fragmentation aerogel glass.
2. The method of preparing monolithic aerogel glass from cracks according to claim 1, wherein: in step S1, the polyvinyl alcohol is one or two of 1788, 1799, 2488 and 2499, and the organic solvent is one of methanol, ethanol and acetone.
3. The method of preparing monolithic aerogel glass from cracks according to claim 1, wherein: in step S1, the temperature of the oven is set to 40 ℃ to 100 ℃.
4. The method of preparing monolithic aerogel glass from cracks according to claim 1, wherein: and in S3, keeping the temperature at 70-95 ℃.
5. The method of preparing monolithic aerogel glass from cracks according to claim 1, wherein: in step S4, the orthosilicate is methyl orthosilicate or ethyl orthosilicate.
6. The method of preparing monolithic aerogel glass from cracks according to claim 1, wherein: in step S4, the concentration of the concentrated hydrochloric acid is 37wt%, the constant temperature is 30-70 ℃, and the constant temperature is kept for 0.5-5 h.
7. The method of preparing monolithic aerogel glass from cracks according to claim 1, wherein: in step S5, the silica sol is heated to 70-90 ℃ before being mixed with the transparent polyvinyl alcohol liquid.
8. The method of preparing monolithic aerogel glass from cracks according to claim 1, wherein: in step S6, the freezing temperature in the low-temperature refrigerating chamber is-40 ℃ to-15 ℃, and the freezing time is 5-24 h; the unfreezing time is 2-10 h; the number of freeze-thaw cycles is 3-8.
9. The method of preparing monolithic aerogel glass from cracks according to claim 1, wherein: in step S8, the supercritical drying is CO2Supercritical drying, setting parameters as follows: the pressure is 8-15MPa, the temperature is 32-60 ℃, and the drying time is 2-10 h; the vacuum degree of the freeze drying is 5Pa-15Pa, the temperature is-50 ℃ to-25 ℃, and the freeze drying is carried out for 5h-24 h.
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