CN117659320A - Ablation-resistant phenolic aerogel and preparation method thereof - Google Patents
Ablation-resistant phenolic aerogel and preparation method thereof Download PDFInfo
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- CN117659320A CN117659320A CN202311521304.8A CN202311521304A CN117659320A CN 117659320 A CN117659320 A CN 117659320A CN 202311521304 A CN202311521304 A CN 202311521304A CN 117659320 A CN117659320 A CN 117659320A
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- ISWSIDIOOBJBQZ-UHFFFAOYSA-N phenol group Chemical group C1(=CC=CC=C1)O ISWSIDIOOBJBQZ-UHFFFAOYSA-N 0.000 title claims abstract description 119
- 239000004964 aerogel Substances 0.000 title claims abstract description 70
- 238000002679 ablation Methods 0.000 title claims abstract description 40
- 238000002360 preparation method Methods 0.000 title claims abstract description 18
- WSFSSNUMVMOOMR-UHFFFAOYSA-N Formaldehyde Chemical compound O=C WSFSSNUMVMOOMR-UHFFFAOYSA-N 0.000 claims abstract description 63
- MUBZPKHOEPUJKR-UHFFFAOYSA-N Oxalic acid Chemical compound OC(=O)C(O)=O MUBZPKHOEPUJKR-UHFFFAOYSA-N 0.000 claims abstract description 48
- KXGFMDJXCMQABM-UHFFFAOYSA-N 2-methoxy-6-methylphenol Chemical compound [CH]OC1=CC=CC([CH])=C1O KXGFMDJXCMQABM-UHFFFAOYSA-N 0.000 claims abstract description 35
- 229930185605 Bisphenol Natural products 0.000 claims abstract description 34
- IISBACLAFKSPIT-UHFFFAOYSA-N bisphenol A Chemical compound C=1C=C(O)C=CC=1C(C)(C)C1=CC=C(O)C=C1 IISBACLAFKSPIT-UHFFFAOYSA-N 0.000 claims abstract description 34
- 229920001568 phenolic resin Polymers 0.000 claims abstract description 34
- 239000005011 phenolic resin Substances 0.000 claims abstract description 34
- VKYKSIONXSXAKP-UHFFFAOYSA-N hexamethylenetetramine Chemical compound C1N(C2)CN3CN1CN2C3 VKYKSIONXSXAKP-UHFFFAOYSA-N 0.000 claims abstract description 32
- 238000006243 chemical reaction Methods 0.000 claims abstract description 26
- 238000000034 method Methods 0.000 claims abstract description 25
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims abstract description 22
- 239000002904 solvent Substances 0.000 claims abstract description 21
- 239000011240 wet gel Substances 0.000 claims abstract description 20
- 239000004312 hexamethylene tetramine Substances 0.000 claims abstract description 16
- 235000010299 hexamethylene tetramine Nutrition 0.000 claims abstract description 16
- 235000006408 oxalic acid Nutrition 0.000 claims abstract description 16
- 239000003431 cross linking reagent Substances 0.000 claims abstract description 15
- 238000001035 drying Methods 0.000 claims abstract description 13
- 239000000499 gel Substances 0.000 claims abstract description 13
- 239000003054 catalyst Substances 0.000 claims abstract description 10
- 238000006068 polycondensation reaction Methods 0.000 claims abstract description 9
- XEKOWRVHYACXOJ-UHFFFAOYSA-N Ethyl acetate Chemical compound CCOC(C)=O XEKOWRVHYACXOJ-UHFFFAOYSA-N 0.000 claims description 21
- 239000007787 solid Substances 0.000 claims description 14
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 claims description 9
- 125000000524 functional group Chemical group 0.000 claims description 8
- 238000010438 heat treatment Methods 0.000 claims description 8
- 238000003756 stirring Methods 0.000 claims description 8
- 239000007810 chemical reaction solvent Substances 0.000 claims description 7
- 238000002156 mixing Methods 0.000 claims description 7
- 230000032683 aging Effects 0.000 claims description 6
- 238000001816 cooling Methods 0.000 claims description 6
- 238000001879 gelation Methods 0.000 claims description 6
- 229920003986 novolac Polymers 0.000 claims description 5
- ZWEHNKRNPOVVGH-UHFFFAOYSA-N 2-Butanone Chemical compound CCC(C)=O ZWEHNKRNPOVVGH-UHFFFAOYSA-N 0.000 claims description 4
- KFZMGEQAYNKOFK-UHFFFAOYSA-N Isopropanol Chemical compound CC(C)O KFZMGEQAYNKOFK-UHFFFAOYSA-N 0.000 claims description 4
- AMQJEAYHLZJPGS-UHFFFAOYSA-N N-Pentanol Chemical compound CCCCCO AMQJEAYHLZJPGS-UHFFFAOYSA-N 0.000 claims description 4
- BDERNNFJNOPAEC-UHFFFAOYSA-N propan-1-ol Chemical compound CCCO BDERNNFJNOPAEC-UHFFFAOYSA-N 0.000 claims description 4
- PHTQWCKDNZKARW-UHFFFAOYSA-N isoamylol Chemical compound CC(C)CCO PHTQWCKDNZKARW-UHFFFAOYSA-N 0.000 claims description 3
- WSFSSNUMVMOOMR-NJFSPNSNSA-N methanone Chemical compound O=[14CH2] WSFSSNUMVMOOMR-NJFSPNSNSA-N 0.000 claims description 2
- 125000002496 methyl group Chemical group [H]C([H])([H])* 0.000 claims description 2
- 125000001997 phenyl group Chemical group [H]C1=C([H])C([H])=C(*)C([H])=C1[H] 0.000 claims description 2
- 230000001476 alcoholic effect Effects 0.000 claims 1
- 238000004108 freeze drying Methods 0.000 abstract description 4
- 238000000352 supercritical drying Methods 0.000 abstract description 2
- 125000002887 hydroxy group Chemical group [H]O* 0.000 description 10
- 229920005989 resin Polymers 0.000 description 7
- 239000011347 resin Substances 0.000 description 7
- 238000011056 performance test Methods 0.000 description 6
- 125000003178 carboxy group Chemical group [H]OC(*)=O 0.000 description 5
- 239000000463 material Substances 0.000 description 5
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 4
- 238000009413 insulation Methods 0.000 description 4
- 239000011159 matrix material Substances 0.000 description 4
- 230000004048 modification Effects 0.000 description 4
- 238000012986 modification Methods 0.000 description 4
- 229920000642 polymer Polymers 0.000 description 4
- 239000002131 composite material Substances 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 230000002265 prevention Effects 0.000 description 3
- 230000035484 reaction time Effects 0.000 description 3
- 238000012360 testing method Methods 0.000 description 3
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical group [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 2
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 description 2
- -1 aging Substances 0.000 description 2
- 230000000052 comparative effect Effects 0.000 description 2
- 238000000354 decomposition reaction Methods 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 239000007789 gas Substances 0.000 description 2
- 239000003779 heat-resistant material Substances 0.000 description 2
- 239000011810 insulating material Substances 0.000 description 2
- 229910052757 nitrogen Inorganic materials 0.000 description 2
- 238000000197 pyrolysis Methods 0.000 description 2
- 238000011160 research Methods 0.000 description 2
- 238000006467 substitution reaction Methods 0.000 description 2
- 241001391944 Commicarpus scandens Species 0.000 description 1
- XDTMQSROBMDMFD-UHFFFAOYSA-N Cyclohexane Chemical compound C1CCCCC1 XDTMQSROBMDMFD-UHFFFAOYSA-N 0.000 description 1
- 229910018557 Si O Inorganic materials 0.000 description 1
- DKGAVHZHDRPRBM-UHFFFAOYSA-N Tert-Butanol Chemical compound CC(C)(C)O DKGAVHZHDRPRBM-UHFFFAOYSA-N 0.000 description 1
- OBNDGIHQAIXEAO-UHFFFAOYSA-N [O].[Si] Chemical compound [O].[Si] OBNDGIHQAIXEAO-UHFFFAOYSA-N 0.000 description 1
- 150000001298 alcohols Chemical class 0.000 description 1
- RQPZNWPYLFFXCP-UHFFFAOYSA-L barium dihydroxide Chemical compound [OH-].[OH-].[Ba+2] RQPZNWPYLFFXCP-UHFFFAOYSA-L 0.000 description 1
- 229910001863 barium hydroxide Inorganic materials 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 238000006555 catalytic reaction Methods 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000018044 dehydration Effects 0.000 description 1
- 238000006297 dehydration reaction Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000018109 developmental process Effects 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 238000005886 esterification reaction Methods 0.000 description 1
- 239000000835 fiber Substances 0.000 description 1
- 238000011010 flushing procedure Methods 0.000 description 1
- 125000002485 formyl group Chemical class [H]C(*)=O 0.000 description 1
- 239000012774 insulation material Substances 0.000 description 1
- 125000000325 methylidene group Chemical group [H]C([H])=* 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 239000002086 nanomaterial Substances 0.000 description 1
- 239000012071 phase Substances 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 230000002787 reinforcement Effects 0.000 description 1
- 238000002390 rotary evaporation Methods 0.000 description 1
- 238000007789 sealing Methods 0.000 description 1
- LIVNPJMFVYWSIS-UHFFFAOYSA-N silicon monoxide Inorganic materials [Si-]#[O+] LIVNPJMFVYWSIS-UHFFFAOYSA-N 0.000 description 1
- 229910000029 sodium carbonate Inorganic materials 0.000 description 1
- 239000007790 solid phase Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Classifications
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G8/00—Condensation polymers of aldehydes or ketones with phenols only
- C08G8/04—Condensation polymers of aldehydes or ketones with phenols only of aldehydes
- C08G8/08—Condensation polymers of aldehydes or ketones with phenols only of aldehydes of formaldehyde, e.g. of formaldehyde formed in situ
- C08G8/24—Condensation polymers of aldehydes or ketones with phenols only of aldehydes of formaldehyde, e.g. of formaldehyde formed in situ with mixtures of two or more phenols which are not covered by only one of the groups C08G8/10 - C08G8/20
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G8/00—Condensation polymers of aldehydes or ketones with phenols only
- C08G8/04—Condensation polymers of aldehydes or ketones with phenols only of aldehydes
- C08G8/08—Condensation polymers of aldehydes or ketones with phenols only of aldehydes of formaldehyde, e.g. of formaldehyde formed in situ
- C08G8/20—Condensation polymers of aldehydes or ketones with phenols only of aldehydes of formaldehyde, e.g. of formaldehyde formed in situ with polyhydric phenols
-
- 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
- C08J2201/05—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
- C08J2205/00—Foams characterised by their properties
- C08J2205/02—Foams characterised by their properties the finished foam itself being a gel or a gel being temporarily formed when processing the foamable composition
- C08J2205/026—Aerogel, i.e. a supercritically dried gel
-
- 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
- C08J2361/00—Characterised by the use of condensation polymers of aldehydes or ketones; Derivatives of such polymers
- C08J2361/04—Condensation polymers of aldehydes or ketones with phenols only
- C08J2361/06—Condensation polymers of aldehydes or ketones with phenols only of aldehydes with phenols
-
- 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
- C08J2361/00—Characterised by the use of condensation polymers of aldehydes or ketones; Derivatives of such polymers
- C08J2361/04—Condensation polymers of aldehydes or ketones with phenols only
- C08J2361/06—Condensation polymers of aldehydes or ketones with phenols only of aldehydes with phenols
- C08J2361/12—Condensation polymers of aldehydes or ketones with phenols only of aldehydes with phenols with polyhydric phenols
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- Chemical & Material Sciences (AREA)
- Health & Medical Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Medicinal Chemistry (AREA)
- Polymers & Plastics (AREA)
- Organic Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Phenolic Resins Or Amino Resins (AREA)
Abstract
The invention relates to an ablation-resistant phenolic aerogel and a preparation method thereof, and belongs to the technical field of aerogel preparation. The method comprises the following steps: bisphenol POSS, phenol and formaldehyde are utilized, oxalic acid is used as a catalyst for polycondensation reaction, and linear phenolic resin with a main chain containing a POSS structure is generated; carrying out sol-gel reaction by using linear phenolic resin with a main chain containing a POSS structure and an alcohol solvent and using hexamethylenetetramine as a cross-linking agent to obtain phenolic wet gel with the main chain containing the POSS structure; and (3) drying the phenolic wet gel at normal pressure to obtain the phenolic aerogel with the main chain containing the POSS structure. The invention can prepare the ablation-resistant phenolic aerogel with a nanoscale multi-stage microstructure and a POSS structure in a main chain without using high-cost preparation processes such as solvent replacement, supercritical drying, freeze drying and the like, and has the characteristics of wide applicability, simple reaction process, low process cost and the like.
Description
Technical Field
The invention relates to an ablation-resistant phenolic aerogel and a preparation method thereof, and belongs to the technical field of aerogel preparation.
Background
Phenolic resin has become the most commonly used resin matrix of ablation heat-resistant composite materials due to its excellent properties such as high temperature resistance, high carbon residue, flame retardance, etc. With the rapid development of the aerospace technology, the deep space exploration aircraft has the requirements of light weight and high-efficiency heat prevention and insulation on the ablation heat prevention composite material, and the sol-gel technology is adopted to prepare the phenolic resin into aerogel while the density of the fiber reinforcement is reduced, so that the method is an important way for reducing the density of a resin matrix and improving the heat insulation performance. The phenolic aerogel is a gel material with a three-dimensional network space structure, has a nano porous structure, and limits gas phase heat conduction and solid phase heat conduction of heat, so that the material has good heat insulation performance, in addition, pyrolysis gas generates a thermal choking effect, and a carbon layer formed by pyrolysis can reversely radiate and dissipate heat, so that the phenolic aerogel also has an ablation heat prevention effect.
However, a large amount of phenolic hydroxyl groups and methylene in the molecular structure of the phenolic aerogel are easily oxidized and decomposed under the high-temperature condition, the ablation resistance is poor when the phenolic aerogel is used for a long time under the aerobic condition, the porous structure of the aerogel is collapsed, the heat insulation performance is seriously reduced, meanwhile, once the phenolic aerogel is completely ablated, the mechanical performance of the aerogel composite material is greatly reduced, and under the condition of high airflow flushing, the aerogel heat insulation material is damaged and loses efficacy. Therefore, ablation-resistant modification is required to be carried out on the phenolic aerogel, so that the phenolic aerogel is ensured to maintain higher residual weight rate in the use process, and the heat-proof and insulating material is ensured to maintain better structural strength.
POSS is a collective name of oligomeric silsesquioxane with a cage structure, and consists of silicon-oxygen frameworks alternately connected by Si-O, wherein the three-dimensional size of the POSS is between 1 and 3 nm. The outside of each POSS molecule can be designed into active or inert functional groups, so that the POSS material can be copolymerized or grafted in a macromolecular network of the polymer, which solves the problem of poor compatibility of the traditional nano material and a polymer system. The POSS can inhibit the chain segment movement of the polymer and improve the thermal performance and mechanical property of the resin due to the nano size similar to the chain segment of the polymer. The POSS modified phenolic aerogel is expected to greatly improve the ablation resistance of the phenolic aerogel, and greatly widens the upper limit of the service of the pneumatic thermal environment of the traditional phenolic aerogel heat-proof and insulating material.
In the "preparation and performance research of special hybrid phenolic aerogel" of the university of Beijing chemical industry, shuoshi research institute, a method for grafting POSS modified phenolic aerogel is disclosed: (1) preparation of octacarboxyl POSS grafted modified phenolic aerogel: firstly, taking m-diphenol and formaldehyde as raw materials, taking water as a reaction solvent and sodium carbonate as a catalyst, and obtaining a uniform and transparent solution through a prepolymerization process at 45 ℃. And adding a certain amount of octacarboxyl POSS, performing esterification reaction on carboxyl and hydroxyl of the phenolic prepolymer to enable the POSS to be grafted to a side chain of the phenolic prepolymer, and finally, performing gel, aging, ethanol and cyclohexane solvent replacement and normal-pressure drying to obtain octacarboxyl POSS grafted modified phenolic aerogel. (2) Preparing hydroxyl POSS grafted modified phenolic aerogel: firstly, in an ethyl acetate solution of hydroxyl POSS and a methanol solution of formaldehyde and barium hydroxide, heating for prepolymerization, and removing the solvent by rotary evaporation to obtain a hydroxyl POSS grafted phenolic solution. Finally, the hydroxyl POSS grafted modified phenolic aerogel is obtained through gel, aging, ethanol and tertiary butanol solvent replacement and freeze drying. Although the POSS structure is successfully introduced into the phenolic aerogel, the POSS is grafted on a phenolic molecular side chain, but is not in a phenolic molecular main chain, so that the density of the modified phenolic aerogel is obviously increased; and because of the reasons of reaction steric hindrance, only a small part of the reactive functional groups (eg, carboxyl and hydroxyl) on the POSS are used for grafting reaction, the utilization rate is low, and the thermal stability of the reactive functional groups (eg, carboxyl and hydroxyl) is poor, so that the ablation resistance improving effect of a part of the introduced POSS structure on the phenolic resin aerogel is counteracted; the method requires multiple solvent replacement, even uses freeze drying, has low modification efficiency and does not have economy. How to improve the ablation resistance and the economy of POSS modified phenolic resin aerogel is a technical problem to be solved in the field at present.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides an ablation-resistant phenolic aerogel with a molecular main chain containing a POSS structure and a preparation method thereof.
In order to achieve the above purpose, the technical scheme adopted by the invention is as follows:
the preparation method of the ablation-resistant phenolic aerogel comprises the following steps:
bisphenol POSS, phenol and formaldehyde are utilized, oxalic acid is used as a catalyst for polycondensation reaction, and linear phenolic resin with a main chain containing a POSS structure is generated;
carrying out sol-gel reaction by using linear phenolic resin with a main chain containing a POSS structure and an alcohol solvent and using hexamethylenetetramine as a cross-linking agent to obtain phenolic wet gel with the main chain containing the POSS structure;
and (3) drying the phenolic wet gel at normal pressure to obtain the phenolic aerogel with the main chain containing the POSS structure.
Further, the polycondensation reaction is performed by using bisphenol POSS, phenol and formaldehyde and oxalic acid as a catalyst to generate the linear phenolic resin with a main chain containing a POSS structure, and the method comprises the following steps: bisphenol POSS, phenol and formaldehyde are mixed in a reaction solvent to obtain a uniform solution, oxalic acid solution is dropwise added under stirring and heating conditions, the reaction is carried out for a period of time at constant temperature, the temperature is reduced (preferably to 60-80 ℃), vacuum dehydration and solvent are carried out, and a yellow transparent solid is generated, namely the linear phenolic resin with a POSS structure in the main chain.
Further, the phenolic wet gel with the main chain containing the POSS structure is obtained by performing sol-gel reaction by using the linear phenolic resin with the main chain containing the POSS structure and an alcohol solvent and using hexamethylenetetramine as a cross-linking agent, and comprises the following steps: uniformly mixing the linear phenolic resin with the main chain containing the POSS structure with a proper amount of alcohol solvent to obtain a linear phenolic resin solution with the main chain containing the POSS structure; and adding a certain amount of hexamethylenetetramine as a cross-linking agent into the linear phenolic resin solution with the POSS structure in the main chain under stirring at room temperature, adding the solution into a mould after the hexamethylenetetramine is completely dissolved, heating to carry out gelation reaction and aging to obtain the phenolic wet gel with the POSS structure in the main chain.
Further, the molecular structure of the bisphenol POSS is shown as follows, R 1 Is one of methyl (Me) or phenyl (Ph), R 2 Functional groups containing phenol structures, e.g. R 2-1 、R 2-2 、R 2-3 The structure shown. The molecular structure contains two R 2 So called bisphenol POSS.
Further, in the bisphenol POSS, phenol and formaldehyde, the molar ratio of the bisphenol POSS and phenol added (bisphenol POSS+phenol) to formaldehyde is 100: 50-90, bisphenol POSS and phenol with a mole ratio of 1-100: 99 to 0. The adding amount of the catalyst oxalic acid is 1-3% of the sum of bisphenol POSS and phenol. The amount of oxalic acid added as a catalyst is too low, resulting in insufficient polycondensation reaction. The addition of the catalyst oxalic acid is too high, so that the polycondensation reaction is severe, the molecular weight uniformity is poor, the molecular weight distribution is too wide, and the quality stability of the linear phenolic resin is poor.
Further, the reaction solvent is one or a mixture of more of butanone and ethyl acetate in any proportion. The adding amount of the reaction solvent is 1-3 times of the mass sum of bisphenol POSS, phenol and formaldehyde.
Further, the constant temperature reaction temperature is 75-100 ℃ and the reaction time is 6-10h.
Further, the alcohol solvent is one or more of methanol, ethanol, n-propanol, isopropanol, n-amyl alcohol and isoamyl alcohol in any proportion.
Further, the solid content of the linear phenolic resin solution with the main chain containing the POSS structure is 8-50%. If the solid content is too high, the prepared aerogel has larger density and loses the advantage of low density; if the solid content is too low, the resulting wet gel has poor strength, is prone to cracking when dried at normal pressure, and is severely shrunk.
Further, the addition amount of the crosslinking agent hexamethylenetetramine is 10-20% of the mass of the linear phenolic resin with the main chain containing the POSS structure. If the adding amount of the cross-linking agent is too high, unreacted cross-linking agent remains, so that the thermal stability of the aerogel is reduced; if the amount of the crosslinking agent is too low, the obtained wet gel has poor strength, is easy to crack when being dried under normal pressure, and is severely shrunk.
Further, the temperature of the gelation reaction is 70-150 ℃ and the time is 12-48 h. If the reaction temperature is too low, the wet gel reaction degree is insufficient, the obtained gel has poor strength, is easy to crack when being dried under normal pressure, and is severely shrunk. If the reaction temperature is too high, the vapor pressure of the solvent is high, so that the sealing performance of the die is more challenging, and potential safety hazards exist. If the reaction time is too short, the wet gel reaction degree is insufficient, the obtained gel has poor strength, is easy to break after being dried under normal pressure, and is severely shrunk. If the reaction time is too long, the efficiency of gel curing is affected.
Further, the condition of normal pressure drying is that the drying is carried out for 24 to 72 hours at room temperature, and then the temperature is kept for 12 to 24 hours at 100 to 120 ℃.
The ablation-resistant phenolic aerogel with the molecular main chain containing the POSS structure is prepared by the method.
Compared with the prior art, the invention has the beneficial effects that:
(1) According to the preparation method of the ablation-resistant phenolic aerogel, bisphenol POSS, phenol and aldehyde are subjected to polycondensation reaction under the catalysis of oxalic acid to synthesize linear phenolic resin with a main chain containing a POSS structure, alcohols are used as solvents, hexamethylenetetramine is used as a cross-linking agent, and the ablation-resistant phenolic aerogel with the main chain containing the POSS structure is successfully prepared through sol-gel reaction and normal-pressure drying. The POSS structure is introduced through the main chain, and on the premise that the density of the phenolic aerogel is not increased without grafting POSS, the duty ratio of the POSS structure is greatly improved, and the problem that the density of the modified phenolic aerogel is obviously increased due to the fact that the POSS is grafted on a phenolic molecular side chain is solved; bisphenol POSS bisphenol all participates in polycondensation reaction, and compared with octa-reaction functional groups (eg, carboxyl, hydroxyl), the utilization rate of the reaction functional groups is high, the problem that the thermal stability of residual reaction functional groups (eg, carboxyl, hydroxyl) is poor is solved, and the problem of improving the ablation resistance of a part of introduced POSS structure to phenolic resin aerogel is counteracted.
(2) The invention can prepare the ablation-resistant phenolic aerogel with a nanoscale multi-stage microstructure and a POSS structure in a main chain without using high-cost preparation processes such as solvent replacement, supercritical drying, freeze drying and the like, and has the characteristics of wide applicability, simple reaction process, low process cost and the like.
(3) Compared with the common phenolic aerogel, the ablation-resistant phenolic aerogel with the main chain containing the POSS structure has higher initial decomposition temperature and higher residual weight rate in the nitrogen and air atmosphere, greatly improves the ablation resistance of the phenolic aerogel, can be used as a resin matrix of an outer heat-resistant material of an aerospace vehicle, and greatly improves the heat-resistant and heat-insulating properties of the outer heat-resistant material.
Detailed Description
For the purpose of making the technical scheme of the present invention more understandable, specific examples are described below in detail with reference to the accompanying tables.
Example 1
The preparation method is realized by the following steps:
1) According to the mole ratio of (bisphenol POSS+phenol) to formaldehyde of 100:70, bisphenol POSS, phenol molar ratio 50:50, dissolving bisphenol POSS, phenol and formaldehyde in ethyl acetate (the mass of the bisphenol POSS, the mass of the phenol and the mass of the formaldehyde is 2 times of the sum of the bisphenol POSS, the phenol and the formaldehyde), mixing to obtain a uniform solution, dropwise adding oxalic acid solution (the mass of oxalic acid is 2 percent of the mass sum of the bisphenol POSS and the phenol, the concentration is 10 percent, the solvent is ethyl acetate) under the conditions of stirring and 80 ℃, reacting for 8 hours at 80 ℃, cooling to 70 ℃, vacuum dehydrating and cooling to obtain yellow transparent solid, namely the linear phenolic resin with the main chain containing the POSS structure, adding a proper amount of ethanol according to the solid content of 30 percent, and uniformly mixing to obtain the linear phenolic resin solution (the solid content of 30 percent) with the main chain containing the POSS structure;
2) Adding a cross-linking agent hexamethylenetetramine with the mass which is 15% of the mass of the linear phenolic resin with the main chain containing the POSS structure into the linear phenolic resin solution with the main chain containing the POSS structure under the condition of stirring at room temperature, putting the solution into a mould after the hexamethylenetetramine is completely dissolved, heating to carry out gelation reaction and ageing, and obtaining the phenolic wet gel with the main chain containing the POSS structure at the temperature of 90 ℃ for 6h,120 ℃ for 8h and 150 ℃ for 8h.
3) And (3) drying the phenolic wet gel at normal pressure, wherein the normal pressure drying condition is that the phenolic wet gel is dried at room temperature for 24 hours, and then preserving the heat for 12 hours at 100 ℃ to obtain the ablation-resistant phenolic aerogel with a main chain containing a POSS structure.
The data obtained in this example for the results of the ablation resistant phenolic aerogel test with a POSS structure in the backbone is shown in table 1.
Example 2
The mole ratio of bisphenol POSS and phenol is 100: except for 0, the preparation conditions and the procedure of the ablation resistant phenolic aerogel with the main chain containing the POSS structure are the same as those of example 1, and the data of the performance test results of the ablation resistant phenolic aerogel with the main chain containing the POSS structure are shown in Table 1.
Example 3
The mole ratio of bisphenol POSS and phenol is 1: except for 99, the preparation conditions and the procedure of the ablation resistant phenolic aerogel with the main chain containing the POSS structure are the same as in example 1, and the data of the performance test results of the ablation resistant phenolic aerogel with the main chain containing the POSS structure are shown in Table 1.
Example 4
The molar ratio of the (bisphenol POSS+phenol) and formaldehyde is 100:50, the conditions and procedures for preparing the ablation resistant phenolic aerogel having a main chain containing a POSS structure are the same as those in example 1, and the data of the results of testing the ablation resistant phenolic aerogel having a main chain containing a POSS structure are shown in Table 1.
Example 5
The molar ratio of the (bisphenol POSS+phenol) and formaldehyde is 100: except for 90 degrees, the preparation conditions and the process of the ablation resistant phenolic aerogel with the main chain containing the POSS structure are the same as those of the example 1, and the performance test result data of the ablation resistant phenolic aerogel with the main chain containing the POSS structure are shown in the table 1.
Example 6
The conditions and procedures for preparing the ablation resistant phenolic aerogel having a main chain containing a POSS structure were the same as in example 1, except that the solid content of the phenolic novolak resin solution having a main chain containing a POSS structure was 8%, and the data of the results of the performance test of the ablation resistant phenolic aerogel having a main chain containing a POSS structure are shown in table 1.
Example 7
The conditions and procedures for preparing the ablation resistant phenolic aerogel having a main chain containing a POSS structure were the same as in example 1, except that the solid content of the phenolic novolak resin solution having a main chain containing a POSS structure was 50%, and the data of the results of the performance test of the ablation resistant phenolic aerogel having a main chain containing a POSS structure are shown in table 1.
Comparative example 1
1) The molar ratio of phenol to formaldehyde is 100:70, dissolving phenol and formaldehyde in ethyl acetate (the mass is equal to 2 times of the mass sum of the phenol and the formaldehyde), mixing to obtain a uniform solution, dropwise adding oxalic acid solution (the oxalic acid mass is 2% of the mass sum of bisphenol POSS and the phenol, the concentration is 10% and the solvent is ethyl acetate) under the conditions of stirring and 80 ℃, reacting for 8 hours at 80 ℃, cooling to 70 ℃, dehydrating in vacuum, cooling, and obtaining yellow transparent solid, namely the linear phenolic resin, adding a proper amount of ethanol according to the solid content of 30%, and uniformly mixing to obtain the linear phenolic resin solution (the solid content of 30%);
2) Adding a cross-linking agent hexamethylenetetramine accounting for 15% of the mass of the linear phenolic resin into the linear phenolic resin solution under stirring at room temperature, putting the solution into a mould after the hexamethylenetetramine is completely dissolved, heating to carry out gelation reaction and ageing, and obtaining the phenolic wet gel under the heating treatment conditions of 90 ℃ for 6 hours, 120 ℃ for 8 hours and 150 ℃ for 8 hours.
3) And (3) drying the phenolic wet gel at normal pressure, wherein the normal pressure drying condition is that the phenolic wet gel is dried at room temperature for 24 hours, and then preserving the heat for 12 hours at 100 ℃ to obtain the common phenolic aerogel.
The data obtained for the results of the conventional phenolic aerogel test obtained in this example are shown in Table 1.
TABLE 1 results of Performance test of the ablative resistant phenolic aerogels obtained in examples 1-7
As can be seen from the data in Table 1, compared with comparative example 1, the ablation-resistant phenolic aerogel provided by the invention has higher initial decomposition temperature and higher residual weight rate in nitrogen and air atmosphere, so that the ablation resistance of the phenolic aerogel is greatly improved, the phenolic aerogel is an ideal resin matrix of an outer heat-proof material of an aerospace vehicle, and the heat-proof and insulating properties of the outer heat-proof material can be greatly improved.
The invention is not described in detail in a manner known to those skilled in the art.
The foregoing is merely a preferred embodiment of the present invention, and it should be noted that modifications and substitutions can be made by those skilled in the art without departing from the technical principles of the present invention, and these modifications and substitutions should also be considered as being within the scope of the present invention.
Claims (10)
1. The preparation method of the ablation-resistant phenolic aerogel is characterized by comprising the following steps of:
bisphenol POSS, phenol and formaldehyde are utilized, oxalic acid is used as a catalyst for polycondensation reaction, and linear phenolic resin with a main chain containing a POSS structure is generated;
carrying out sol-gel reaction by using linear phenolic resin with a main chain containing a POSS structure and an alcohol solvent and using hexamethylenetetramine as a cross-linking agent to obtain phenolic wet gel with the main chain containing the POSS structure;
and (3) drying the phenolic wet gel at normal pressure to obtain the phenolic aerogel with the main chain containing the POSS structure.
2. The method of claim 1, wherein the polycondensation reaction of bisphenol POSS, phenol and formaldehyde with oxalic acid as a catalyst to produce a phenolic novolac resin having a POSS structure in the backbone comprises:
mixing bisphenol POSS, phenol and formaldehyde in a reaction solvent to obtain a uniform solution, dropwise adding oxalic acid solution under stirring and heating conditions, reacting for a period of time at constant temperature, cooling, dehydrating in vacuum, cooling with the solvent, and obtaining yellow transparent solid, namely the linear phenolic resin with a main chain containing a POSS structure.
3. The method according to claim 2, wherein the reaction solvent is one or more of butanone and ethyl acetate in any proportion, and the addition amount of the reaction solvent is 1-3 times of the mass sum of bisphenol POSS, phenol and formaldehyde;
the temperature is reduced to 60-80 ℃.
4. The method of claim 1, wherein the step of performing a sol-gel reaction using a novolac resin having a POSS structure in a main chain and an alcohol solvent, and using hexamethylenetetramine as a cross-linking agent to obtain a novolac wet gel having a POSS structure in a main chain comprises: uniformly mixing a linear phenolic resin with a main chain containing a POSS structure with a proper amount of alcohol solvent to obtain a linear phenolic resin solution with the main chain containing the POSS structure, wherein the solid content of the linear phenolic resin solution with the main chain containing the POSS structure is 8% -50%; adding a cross-linking agent hexamethylenetetramine into a linear phenolic resin solution with a main chain containing a POSS structure under stirring at room temperature, wherein the adding amount of the cross-linking agent hexamethylenetetramine is 10% -20% of the mass of the linear phenolic resin with the main chain containing the POSS structure; after hexamethylenetetramine is completely dissolved, adding the solution into a mold, heating to carry out gelation reaction and aging to obtain the phenolic wet gel with the main chain containing the POSS structure.
5. The method of claim 1, wherein the bisphenol POSS has the molecular structure of:
wherein R is 1 Is one of methyl or phenyl, R 2 Is a functional group containing a phenol structure.
6. The method of claim 5, wherein R is 2 Is one of the following:
7. the method according to claim 1, wherein the molar ratio of bisphenol POSS, phenol and formaldehyde, which are added together, is 100: 50-90; the mole ratio of bisphenol POSS and phenol is 1-100: 99 to 0;
the adding amount of the catalyst oxalic acid is 1-3% of the sum of bisphenol POSS and phenol.
8. The method according to claim 1, wherein the alcoholic solvent is one or more of methanol, ethanol, n-propanol, isopropanol, n-pentanol, and iso-pentanol in any proportion.
9. The method according to claim 1, wherein the constant temperature reaction is carried out at 75-100 ℃ for 6-10 hours; the temperature of the gelation reaction is 70-150 ℃ and the time is 12-48 h; the normal pressure drying condition is that the drying is carried out for 24 to 72 hours at room temperature, and then the heat is preserved for 12 to 24 hours at the temperature of 100 to 120 ℃.
10. An ablation resistant phenolic aerogel prepared by the method of any one of claims 1 to 9.
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