CN115710823B - Flexible ablation heat protection composite material and preparation method thereof - Google Patents
Flexible ablation heat protection composite material and preparation method thereof Download PDFInfo
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Abstract
The invention relates to the technical field of composite materials, and provides a flexible ablation heat protection composite material and a preparation method thereof, wherein the preparation method comprises the following steps: uniformly mixing a surfactant, an accelerator, a solvent and organosilane to obtain a mixed solution; adding the phenolic resin prepolymer and the curing agent into the mixed solution for uniform mixing to obtain a phenolic aerogel precursor; and impregnating the fiber fabric through the phenolic aerogel precursor, and then curing to obtain the flexible ablation heat protection composite material. The flexible ablation thermal protection composite material prepared by the invention has excellent flexibility and ablation resistance.
Description
Technical Field
The invention relates to the technical field of composite materials, in particular to a flexible ablation heat protection composite material and a preparation method thereof.
Background
Phenolic resin is a low-flammability material with excellent temperature resistance, and has the advantages of low fuming rate and low toxicity in a high-temperature environment. Phenolic aerogel thermal insulation materials have early development and wide application, and are widely used as thermal insulation materials in the aerospace field due to their relatively low thermal conductivity.
At present, researches on phenolic aerogel and composite materials thereof are mainly focused on traditional rigid aerogel and carbon aerogel generated by carbonization of the traditional rigid aerogel, and the problems of low adaptation degree to a cold structure, low strain failure, difficulty in preparing large-size special-shaped pieces, filling of assembly gaps, difficulty in meeting folding requirements and the like exist in aerospace, nuclear industry, ship manufacturing and other fields, so that the phenolic aerogel is difficult to adapt to special-shaped or deformable thermal protection scenes. However, the research of the flexible aerogel material is mainly oriented to the middle-low temperature field, and the existence of the flexible chain segment severely limits the high-temperature force thermal stability of the material, so that the heat-resistant requirement of aerospace scenes such as aircrafts and the like cannot be met.
Disclosure of Invention
The invention provides a flexible ablation heat protection composite material and a preparation method thereof, and the prepared flexible ablation heat protection composite material has excellent flexibility and ablation resistance, and can be applied to special-shaped or deformable heat protection scenes in the fields of aerospace, nuclear industry, ship manufacturing and the like.
In a first aspect, the present invention provides a method of preparing a flexible ablative thermal protection composite, the method comprising the steps of:
uniformly mixing a surfactant, an accelerator, a solvent and organosilane to obtain a mixed solution;
adding the phenolic resin prepolymer and the curing agent into the mixed solution for uniform mixing to obtain a phenolic aerogel precursor;
and impregnating the fiber fabric through the phenolic aerogel precursor, and then curing to obtain the flexible ablation heat protection composite material.
Preferably, the surfactant is at least one of cetyltrimethylammonium bromide, cetyltrimethylammonium chloride, octadecyldimethylbenzyl ammonium chloride, sodium dodecyl sulfonate and sodium dodecyl sulfate;
the promoter is at least one of ammonia water, glacial acetic acid, oxalic acid, hydrochloric acid, sulfuric acid and formic acid;
the solvent is at least one of deionized water, ethanol and ethylene glycol.
Preferably, the organosilane is an organosiloxane.
More preferably, the organosilane is at least one of dimethyldimethoxysilane, dimethyldiethoxysilane, and vinylmethyldimethoxysilane.
Preferably, the phenolic resin prepolymer is at least one of a pre-polymerized phenolic resin and a monomer mixed solution of a phenolic compound and an aldehyde compound;
the curing agent is at least one of hexamethylenetetramine, p-toluenesulfonic acid and paraformaldehyde.
Preferably, the step of uniformly mixing the surfactant, the accelerator, the solvent and the organosilane to obtain a mixed solution comprises the following steps:
uniformly mixing the surfactant, the accelerator and the solvent to obtain a premix;
and adding the organosilane into the premix solution and uniformly mixing to obtain a mixed solution.
Preferably, the mass ratio of the surfactant to the solvent is (1-3.2): 60;
the mass ratio of the accelerator to the solvent is 1 (500-4000);
the mass ratio of the organosilane to the solvent is 1 (3-10).
Preferably, the mass ratio of the phenolic resin prepolymer to the solvent is 1 (3-6);
the mass ratio of the curing agent to the phenolic resin prepolymer is 1 (15-25).
Preferably, the fiber fabric is at least one of quartz fiber, glass fiber, carbon fiber, mullite fiber, alumina fiber and phenolic fiber.
Preferably, the fiber fabric is at least one of needled felt, 2D woven cloth, 2.5D fabric and 3D fabric.
Preferably, the temperature of the curing treatment is 150-180 ℃ and the curing time is 3-12 h.
Preferably, the curing treatment is performed in a closed environment.
More preferably, the impregnation is vacuum impregnation.
Preferably, the method further comprises: washing treatment and drying treatment are sequentially carried out after the curing treatment;
the solvent adopted in the washing treatment is deionized water and/or ethanol; the temperature of the washing treatment is 23-80 ℃ and the washing time is 2-8 h;
the temperature of the drying treatment is 60-100 ℃.
More preferably, the drying time of the drying process is such that the flexible ablative thermal protection composite maintains a constant weight.
In a second aspect, the present invention provides a flexible ablative thermal protection composite prepared by the method of preparation described in the first aspect above.
Compared with the prior art, the invention has at least the following beneficial effects:
(1) The invention uses the organosilicon silanol after the organosilicon hydrolysis with intrinsic flexibility to carry out grafting modification synchronously with solidification on phenolic molecules; the organosilicon alcohol increases the linear chain length of the phenolic aldehyde so as to increase the deformation freedom degree of molecules while improving the oxidation and ablation resistance, thereby enhancing the flexibility of the phenolic aerogel; and the fiber fabric is used for being compounded together with the flexible phenolic aerogel to obtain the flexible ablation heat protection composite material with deformability.
(2) The reaction system of the flexible ablation thermal protection composite material is environment-friendly, the preparation process is simple, the preparation efficiency is high, a water-based reaction system or a solvent system with mild alcohols is selected, the use of other harmful solvents is avoided, and the environmental friendliness and the production safety of the preparation process are greatly improved.
(3) The flexible ablation thermal protection composite material is prepared by adopting a one-pot cogel molding process and normal-pressure drying, so that the complexity of the traditional composite aerogel preparation process is greatly reduced, the preparation process of the fiber reinforced flexible phenolic aerogel composite material is simplified, the preparation period is shortened, the large-scale efficient production is facilitated, and the composite material has a wide market prospect and application value.
(4) The flexible ablation heat protection composite material has excellent flexibility and can repeatedly perform recoverable deformation in the forms of bending, compression and the like. Meanwhile, the composite material has the characteristics of low density, good heat resistance, low heat conductivity, oxidization resistance, ablation resistance and the like. As an ablative heat protection material, the material is particularly suitable for an aircraft heat protection system in the aerospace field; the material can also be used as a deformable heat insulation material in the fields of aviation, building heat insulation, nuclear industry, ship manufacturing and the like. In addition, the composite material has the characteristics of high porosity, large specific surface area, oleophilic and hydrophobic properties, and can be used in the fields of air purification, liquid filtration and the like under the high-temperature condition.
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 required in the embodiments or the description of the prior art will be briefly described, and it is obvious that the drawings in the following description are 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 flow chart of a method of preparing a flexible ablative thermal protection composite provided by the present invention;
FIG. 2 is a physical view of the flexible ablative thermal protection composite provided in example 1 of the present invention after ablation;
FIG. 3 is a cyclic compression curve of the flexible ablative thermal protection composite provided by example 2 of this invention;
FIG. 4 is a photograph of a rolling hydrophobicity test of the flexible ablative thermal protection composite provided in example 3 of the present invention;
FIG. 5 is a pictorial representation of the flexible ablative thermal protection composite provided in example 4 of the present invention, and a pictorial representation after bending;
fig. 6-9 are electron microscopic views of a flexible ablative thermal protection composite provided in example 5 of the present invention.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments, and all other embodiments obtained by those skilled in the art without making any inventive effort based on the embodiments of the present invention are within the scope of protection of the present invention.
As shown in fig. 1, the invention provides a preparation method of a flexible ablation heat protection composite material, which comprises the following steps:
step (1), uniformly mixing a surfactant, an accelerator, a solvent and organosilane to obtain a mixed solution;
step (2), adding the phenolic resin prepolymer and the curing agent into the mixed solution for uniform mixing to obtain a phenolic aerogel precursor;
and (3) impregnating the fiber fabric through the phenolic aerogel precursor, and then curing to obtain the flexible ablation heat protection composite material.
In the invention, the organosilicon silanol after the hydrolysis of the organosilicon with intrinsic flexibility is utilized to carry out grafting modification synchronously to phenolic molecules during curing; the organosilicon alcohol increases the linear chain length of the phenolic aldehyde so that the molecule has the deformation degree of freedom, thereby enhancing the flexibility of the phenolic aldehyde aerogel; and the fiber fabric is used for being compounded together with the flexible phenolic aerogel to obtain the flexible ablation heat protection composite material with deformability.
According to some preferred embodiments, the surfactant is at least one of cetyltrimethylammonium bromide, cetyltrimethylammonium chloride, octadecyldimethylbenzyl ammonium chloride, sodium dodecyl sulfonate, sodium dodecyl sulfate;
the promoter is at least one of ammonia water, glacial acetic acid, oxalic acid, hydrochloric acid, sulfuric acid and formic acid;
the solvent is at least one of deionized water, ethanol and ethylene glycol.
At least one kind is a mixture of any one or any plurality of kinds mixed in any proportion.
According to some preferred embodiments, the organosilane is an organosiloxane.
According to some more preferred embodiments, the organosilane is an organosiloxane having two alkoxy groups.
According to some more preferred embodiments, the organosilane is at least one of dimethyldimethoxysilane, dimethyldiethoxysilane, vinylmethyldimethoxysilane.
In the invention, organosilane with double functional groups is adopted, namely, the organosilane with two hydroxyl groups is obtained after hydrolysis, in the process of modifying the phenolic aerogel, molecular grafting can be realized microscopically, the linear chain length of molecules can be prolonged, and the flexibility and the thermal stability of the phenolic aerogel can be improved macroscopically. In contrast, highly crosslinked network structures derived from hydrolytic polycondensation of tetraethoxysilane or methyltrimethoxysilane having polyalkoxy functional groups limit the degree of freedom of molecular deformation while containing no or only a small amount of flexible alkyl side chains, and are therefore not suitable for improving the flexibility of phenolic aerogels.
According to some preferred embodiments, the mixing of the surfactant, the accelerator, the solvent and the organosilane to obtain a mixed solution comprises:
uniformly mixing the surfactant, the accelerator and the solvent to obtain a premix;
and adding the organosilane into the premix solution and uniformly mixing to obtain a mixed solution.
After the organosilane was hydrolyzed, a transparent mixed solution was obtained.
In the invention, the organosilane is added into the premix liquid comprising the surfactant, the accelerator and the solvent, so that the organosilane is hydrolyzed into the organosilicon alcohol, the mixed solution containing the organosilicon alcohol is uniformly mixed with the phenolic resin prepolymer, and the surfactant further improves the compatibility of the mixed solution and the phenolic resin prepolymer.
According to some preferred embodiments, the mass ratio of the surfactant to the solvent is (1-3.2): 60 (e.g., may be 1:60, 1.2:60, 1.5:60, 1.8:60, 2:60, 2.2:60, 2.5:60, 2.8:60, 3:60, or 3.2:60);
the mass ratio of the accelerator to the solvent is 1 (500-4000) (e.g., may be 1:500, 1:600, 1:700, 1:800, 1:900, 1:1000, 1:1500, 1:2000, 1:2500, 1:3000, 1:3500, or 1:4000);
the mass ratio of the organosilane to the solvent is 1 (3-10) (e.g., may be 1:3, 1:3.5, 1:4, 1:4.5, 1:5, 1:5.5, 1:6, 1:6.5, 1:7, 1:7.5, 1:8, 1:8.5, 1:9, 1:9.5, or 1:10).
In the present invention, the accelerator is used to provide acidic or basic conditions to the organosilane for hydrolysis of the organosilane. By limiting the amount of the organosilane, the solvent and the accelerator, the hydrolysis speed of the organosilane can be ensured, and the organosilane is not gelled; meanwhile, the use amount of the solvent is controlled, the subsequent polymerization of the hydrolysate and the resin is facilitated, the solvent can be kept in the composite material in the curing process, a porous structure is formed, and the heat insulation performance of the prepared composite material is further improved.
According to some preferred embodiments, the phenolic resin prepolymer is at least one of a pre-polymerized phenolic resin, a monomer mixed solution of a phenolic compound and an aldehyde compound;
the curing agent is at least one of hexamethylenetetramine, p-toluenesulfonic acid and paraformaldehyde.
The pre-polymerized phenolic resin is commercial phenolic resin, namely phenolic resin with lower molecular weight and certain polymerization degree; the monomer mixed solution of the phenolic compound and the aldehyde compound can be used for polymerizing to obtain a mixed solution of monomers of the phenolic resin, for example, the phenolic compound can be at least one of phenol, cresol, nonylphenol, aralkylphenol, octylphenol, bisphenol A, xylenol and cardanol; the aldehyde compound is at least one of formaldehyde, acetaldehyde and furfural.
According to some preferred embodiments, the mass ratio of the phenolic resin prepolymer to the solvent is 1 (3-6) (e.g., may be 1:3, 1:3.5, 1:4, 1:4.5, 1:5, 1:5.5, or 1:6);
the mass ratio of the curing agent to the phenolic resin prepolymer is 1 (15-25) (e.g., may be 1:15, 1:16, 1:18, 1:20, 1:22, 1:23, or 1:25).
In the invention, the dosages of the phenolic resin and the organosilane are indirectly limited by limiting the dosages of the phenolic resin prepolymer and the solvent, so that the situation that the prepared flexible ablation thermal protection composite material has excellent flexibility but the ablation resistance is reduced when the dosage of the organosilane is too high is avoided, and the problem that the prepared composite material has poor flexibility when the dosage of the organosilane is too low is also avoided, so that the prepared flexible ablation thermal protection composite material has excellent flexibility and ablation resistance through the limitation.
According to some preferred embodiments, the fiber fabric is at least one of quartz fiber, glass fiber, carbon fiber, mullite fiber, alumina fiber, phenolic fiber.
According to some preferred embodiments, the fibrous fabric is at least one of needled felt, 2D woven cloth, 2.5D fabric, 3D fabric.
In the invention, the fiber fabric adopts layered fiber fabric, and the flexible ablation thermal protection composite material with excellent flexibility is prepared by means of the flexibility of the layered fiber fabric which is easy to slip between layers and the cooperation of flexible phenolic aerogel.
According to some more preferred embodiments, the density of the fibrous web is from 0.07 to 0.12g/cm 3 (e.g., may be 0.07 g/cm) 3 、0.08g/cm 3 、0.09g/cm 3 、0.1g/cm 3 、0.11g/cm 3 Or 0.12g/cm 3 )。
The density of the fiber fabric used in the present invention includes, but is not limited to, 0.07 to 0.12g/cm 3 . When the density of the fiber fabric is 0.07-0.12 g/cm 3 When the content of the phenolic aerogel in the prepared flexible ablation heat protection composite material is relatively high, the flexibility is better.
According to some preferred embodiments, the curing process is at a temperature of 150-180 ℃ (e.g., may be 150 ℃, 155 ℃, 160 ℃, 165 ℃, 170 ℃, 175 ℃, or 180 ℃), and the curing time is 3-12 hours (e.g., may be 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, or 12 hours).
According to some preferred embodiments, the curing treatment is performed in a closed environment.
In the invention, in the curing process, hydrolyzed organosilane in the phenolic aerogel precursor is embedded into a crosslinked phenolic network through condensation with phenolic molecules, so that the phenolic resin is subjected to grafting modification synchronous with curing, and the phenolic aerogel precursor becomes flexible phenolic aerogel. More importantly, the curing process is performed in a closed environment, so that the solvent is reserved on the composite material after evaporation to form a porous structure, and the composite material has a high specific surface area, so that the heat insulation performance of the composite material is improved.
According to some more preferred embodiments, the impregnation is vacuum impregnation.
The fiber fabric is impregnated by vacuum impregnation, so that the phenolic aerogel precursor is fully immersed in the fiber fabric, and the impregnation efficiency is improved.
According to some preferred embodiments, the method further comprises: washing treatment and drying treatment are sequentially carried out after the curing treatment;
the solvent adopted in the washing treatment is deionized water and/or ethanol; the temperature of the washing treatment is 23 to 80 ℃ (for example, 23 ℃, 25 ℃, 30 ℃, 35 ℃, 40 ℃, 45 ℃, 50 ℃, 55 ℃, 60 ℃, 65 ℃, 70 ℃, 75 ℃ or 80 ℃), and the washing time is 2 to 8 hours (for example, 2 hours, 2.5 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours or 8 hours);
the drying treatment temperature is 60 to 100 ℃ (for example, 60 ℃, 65 ℃, 70 ℃, 75 ℃, 80 ℃, 85 ℃, 90 ℃, 95 ℃ or 100 ℃).
In the washing treatment, the washing solvent is generally replaced 3 to 5 times to sufficiently remove the surfactant. The drying treatment is normal pressure drying.
According to some more preferred embodiments, the drying time of the drying process is based on maintaining the flexible ablative thermal protection composite at a constant weight.
The invention also provides a flexible ablation heat protection composite material, which is prepared by adopting the preparation method provided by the invention.
In order to more clearly illustrate the technical solution and advantages of the present invention, a flexible ablative thermal protection composite and a method of making the same are described in detail below by way of several examples.
In the following examples, the pre-polymerized phenolic resin was a phenolic resin for insulation material purchased from the company of Santa Clay, inc.; and the phenolic resin obtained by curing the pre-polymerized phenolic resin in examples 1 to 9 was a bulk phenolic resin.
Example 1
(1) Preparing a phenolic aerogel precursor: (1) mixing, stirring and dissolving 0.8g of cetyltrimethylammonium bromide and 30mL of acidic deionized water solution with glacial acetic acid concentration of 5mM until the solution is clear and transparent, and obtaining a premix; (2) adding 6mL of dimethyl dimethoxy silane into the premix, and stirring for 30min to obtain a mixed solution; (3) continuously adding 7g of pre-polymerized phenolic resin and 0.4g of hexamethylenetetramine into the mixed solution, and stirring until the mixture is clear and transparent to obtain a phenolic aerogel precursor;
(2) Preparation of a flexible ablative thermal protection composite: will be of the size ofThe quartz fiber needled felt of the step (1) is put into a phenolic aerogel precursor, then the precursor is fully filled with the quartz fiber needled felt through vacuum impregnation for 15min, the quartz fiber needled felt filled with the phenolic aerogel precursor is transferred into a closed container, the wet gel is prepared after closed solidification for 12h at 170 ℃, and then the wet gel is washed by deionized water for 3 times, each time is washed for 2h to remove a surfactant, and then the soft ablation thermal protection composite material is prepared after drying to constant weight at 100 ℃.
Example 2
(1) Preparing a phenolic aerogel precursor: (1) 1.6g of cetyltrimethylammonium bromide and 30mL of acid deionized water solution with oxalic acid concentration of 5mM are mixed, stirred and dissolved until the solution is clear and transparent, and a premix solution is obtained; (2) adding 6mL of dimethyl dimethoxy silane into the premix, and stirring for 30min to obtain a mixed solution; (3) continuously adding 10g of pre-polymerized phenolic resin and 0.5g of hexamethylenetetramine into the mixed solution, and stirring until the mixture is clear and transparent to obtain a phenolic aerogel precursor;
(2) Preparation of a flexible ablative thermal protection composite: will be of the size ofThe carbon fiber needled felt of the step (1) is put into a phenolic aerogel precursor, then the precursor is fully filled with the carbon fiber needled felt through vacuum impregnation for 15min, the carbon fiber needled felt filled with the phenolic aerogel precursor is transferred into a closed container, the carbon fiber needled felt is cured for 12h in a closed manner at 170 ℃ to obtain wet gel, and then the wet gel is washed by deionized water for 3 times, each time is washed for 2h to remove a surfactant, and then the soft ablation thermal protection composite material is obtained after drying at 100 ℃ to constant weight.
Example 3
(1) Preparing a phenolic aerogel precursor: (1) 1.6g of sodium dodecyl sulfate and 30mL of acid deionized water solution with glacial acetic acid concentration of 5mM are mixed, stirred and dissolved until the solution is clear and transparent, and a premix is obtained; (2) adding 6mL of dimethyl dimethoxy silane into the premix, and stirring for 30min to obtain a mixed solution; (3) continuously adding 10g of pre-polymerized phenolic resin and 0.5g of hexamethylenetetramine into the mixed solution, and stirring until the mixture is clear and transparent to obtain a phenolic aerogel precursor;
(2) Preparation of a flexible ablative thermal protection composite: will be of the size ofThe glass fiber needled felt filled with the phenolic aerogel precursor is put into the phenolic aerogel precursor in the step (1), then is subjected to vacuum impregnation for 15min to completely fill the glass fiber needled felt, the glass fiber needled felt filled with the phenolic aerogel precursor is transferred into a closed container, is subjected to closed curing for 12h at 170 ℃ to prepare wet gel, and thenAnd washing with deionized water for 3 times, washing for 2 hours each time to remove the surfactant, and drying at 100 ℃ to constant weight to obtain the flexible ablation heat protection composite material.
Example 4
(1) Preparing a phenolic aerogel precursor: (1) 1.8g of cetyltrimethylammonium bromide and 30mL of acid deionized water solution with hydrochloric acid concentration of 5mM are mixed, stirred and dissolved until the solution is clear and transparent, and a premix solution is obtained; (2) adding 6mL of dimethyl diethoxy silane into the pre-mixed solution, and stirring for 30min to obtain a mixed solution; (3) continuously adding 10g of pre-polymerized phenolic resin and 0.5g of hexamethylenetetramine into the mixed solution, and stirring until the mixture is clear and transparent to obtain a phenolic aerogel precursor;
(2) Preparation of a flexible ablative thermal protection composite: will be of the size ofThe method comprises the steps of (1) placing phenolic fiber cloth fabric in a phenolic aerogel precursor in the step, then soaking the phenolic fiber cloth fabric in vacuum for 15min to enable the precursor to be fully filled with the phenolic fiber cloth, transferring the phenolic fiber cloth filled with the phenolic aerogel precursor into a closed container, performing closed curing at 170 ℃ for 12h to obtain wet gel, washing the wet gel with deionized water for 3 times, washing the wet gel for 2h each time to remove a surfactant, and drying the wet gel at 100 ℃ to constant weight to obtain the flexible ablation thermal protection composite material.
Example 5
(1) Preparing a phenolic aerogel precursor: (1) 1.4g of cetyltrimethylammonium chloride and 30mL of acid deionized water solution with glacial acetic acid concentration of 5mM are mixed, stirred and dissolved until the solution is clear and transparent, and a premix solution is obtained; (2) adding 3mL of dimethyl diethoxy silane into the premix, and stirring for 30min to obtain a mixed solution; (3) continuously adding 7g of pre-polymerized phenolic resin and 0.4g of hexamethylenetetramine into the mixed solution, and stirring until the mixture is clear and transparent to obtain a phenolic aerogel precursor;
(2) Preparation of a flexible ablative thermal protection composite: will be of the size ofQuartz of (2)Placing the fiber needled felt into the phenolic aerogel precursor in the step (1), then soaking the phenolic aerogel precursor in vacuum for 15min to enable the precursor to be fully filled with the quartz fiber needled felt, transferring the quartz fiber needled felt filled with the phenolic aerogel precursor into a closed container, performing closed curing for 5h at 150 ℃, heating to 180 ℃ and performing closed curing for 3h to obtain wet gel, washing the wet gel with deionized water for 3 times, washing the wet gel for 2h each time to remove the surfactant, and drying the wet gel at 100 ℃ to constant weight to obtain the flexible ablation thermal protection composite material.
Example 6
Example 6 is substantially the same as example 1, except that: 7g of the prepolymerized phenolic resin and 0.46g of hexamethylenetetramine were used.
Example 7
Example 7 is substantially the same as example 1, except that: 7g of the prepolymerized phenolic resin and 0.28g of hexamethylenetetramine were used.
Example 8
Example 8 is substantially the same as example 1, except that: 4mL of dimethyldimethoxysilane, 5g of pre-polymerized phenolic resin and 0.29g of hexamethylenetetramine were used.
Example 9
Example 9 is substantially the same as example 1, except that: 7g of a mixed solution composed of formaldehyde and phenol with a solids content of 45% are used.
Comparative example 1
Comparative example 1 is substantially the same as example 1 except that: in the step (1), cetyl trimethyl ammonium bromide, an acidic deionized water solution of glacial acetic acid, dimethyl dimethoxy silane, pre-polymerized phenolic resin and hexamethylenetetramine are uniformly mixed to obtain a phenolic aerogel precursor.
Comparative example 2
Comparative example 2 is substantially the same as example 1 except that: 6mL of ethyl orthosilicate was used instead of 6mL of dimethyldimethoxysilane.
Comparative example 3
Comparative example 3 is substantially the same as example 1 except that: in the step (2), the quartz fiber needled felt filled with the phenolic aerogel precursor is transferred into a non-closed container, wet gel is prepared after curing for 12 hours at 170 ℃, then the wet gel is washed with deionized water for 3 times, each time is washed for 2 hours to remove the surfactant, and then the soft ablation thermal protection composite material is prepared after drying to constant weight at 100 ℃.
Comparative example 4
Comparative example 4 is substantially the same as example 1 except that: 13mL of dimethyldimethoxysilane was used.
Comparative example 5
Comparative example 5 is substantially the same as example 1 except that: 3mL of dimethyldimethoxysilane was used.
The flexible ablative thermal protection composites obtained in examples 1 to 9 and comparative examples 1 to 5 were used as test pieces, and the thermal conductivity, residual weight, flexibility and hydrophobicity of the test pieces were respectively tested to obtain the related data shown in table 1. Wherein the thermal conductivity test is performed with reference to the ISO 22007-2 standard; ablating for 1min under butane flame at 1200 ℃ to obtain carbon residue rate data; the samples are subjected to cyclic compression curve tests under different strain conditions (20%, 40%, 60%, 80%) to obtain flexibility data; the above test pieces were subjected to a rolling hydrophobic test under an inclination angle of 6 °.
TABLE 1
As can be seen from the data in table 1, the flexible ablative thermal protection composites prepared in examples 1 to 9 of the present invention have light weight, low thermal conductivity characteristics, particularly in the Z direction in the vertical plane, and thus are light weight composites with excellent thermal insulation properties. Meanwhile, the composite material has excellent flexibility and restorability deformability, and in the ablation process, the composite material has good dimensional stability, high residual weight rate, oxidation resistance and ablation resistance, has outstanding dimension capability, and is a flexible ablation type heat protection material with high performance. Meanwhile, the material has good hydrophobicity and is suitable for long-term use in thermal protection application scenes.
FIG. 2 shows a physical image of a thin layer of the flexible ablative thermal protection composite processed to a thickness of 3mm in example 1 after butane flame ablation at 1200℃for 1 min. Fig. 3 shows the cyclic compression curve of the flexible ablative thermal protection composite prepared in example 2. FIG. 4 shows a rolling hydrophobicity test photograph of the flexible ablative thermal protection composite prepared in example 3, and it can be seen from FIG. 4 that the maximum contact angle of the composite is 148 when the tilt angle is 0; the minimum roll angle is below 6. Fig. 5 shows a physical view and a schematic representation of the flexible ablative thermal protection composite prepared in example 4 after bending. Fig. 6-9 show scanning electron microscopy images of the flexible ablative thermal protection composite prepared in example 5: fig. 6 and 7 show the composite morphology of the phenolic aerogel filled within the fiber pores, and fig. 8 and 9 show the porous morphology of the phenolic aerogel filled within the fiber pores.
As can be seen from fig. 6 to 9, the flexible ablative thermal protection composite material prepared by the invention has a micro-nano porous structure with layered characteristics, and has a uniform and controllable microstructure.
Based on example 1 and comparative examples 1 to 5, it was found that, since comparative example 1 directly blended all the raw materials, the organosilane was not miscible with the pre-polymerized phenolic resin, and even phase-separated, and a flexible ablative thermal protection composite could not be prepared. In comparative example 2, ethyl orthosilicate is used to replace organosilane, and because the ethyl orthosilicate is hydrolyzed and polycondensed to obtain a highly cross-linked network structure, the degree of freedom of molecular deformation is limited, and a flexible alkyl side chain is not contained, the obtained flexible ablation heat protection composite material has no rebound resilience and poor flexibility. In comparative example 3, the solvent was volatilized because the curing was not performed in a closed environment, and a porous structure could not be built in the composite material, so that an aerogel-based composite material could not be produced. From comparative examples 4 and 5, it was found that when the mass ratio of organosilane to solvent was outside the range of 1 (3 to 10), either too little or too much organosilane was used to affect the performance of the prepared flexible ablative thermal protection composite.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention, and are not limiting; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present invention. The invention is not described in detail in a manner known to those skilled in the art.
Claims (11)
1. A method of preparing a flexible ablative thermal protection composite, comprising the steps of:
uniformly mixing a surfactant, an accelerator, a solvent and organosilane to obtain a mixed solution; the organosilane is at least one of dimethyl dimethoxy silane, dimethyl diethoxy silane and vinyl methyl dimethoxy silane; the mass ratio of the surfactant to the solvent is (1-3.2) 60; the mass ratio of the accelerator to the solvent is 1 (500-4000); the mass ratio of the organosilane to the solvent is 1 (3-10);
adding the phenolic resin prepolymer and the curing agent into the mixed solution for uniform mixing to obtain a phenolic aerogel precursor;
impregnating the fiber fabric through the phenolic aerogel precursor, and then curing to obtain a flexible ablation heat protection composite material; the curing treatment is performed in a closed environment.
2. The method according to claim 1, wherein,
the surfactant is at least one of cetyl trimethyl ammonium bromide, cetyl trimethyl ammonium chloride, octadecyl dimethyl benzyl ammonium chloride, sodium dodecyl sulfonate and sodium dodecyl sulfate;
the promoter is at least one of ammonia water, glacial acetic acid, oxalic acid, hydrochloric acid, sulfuric acid and formic acid;
the solvent is at least one of deionized water, ethanol and ethylene glycol.
3. The method according to claim 1, wherein,
the phenolic resin prepolymer is at least one of a pre-polymerized phenolic resin and a monomer mixed solution of a phenolic compound and an aldehyde compound;
the curing agent is at least one of hexamethylenetetramine, p-toluenesulfonic acid and paraformaldehyde.
4. The method of claim 1, wherein the step of uniformly mixing the surfactant, the accelerator, the solvent and the organosilane to obtain a mixed solution comprises:
uniformly mixing the surfactant, the accelerator and the solvent to obtain a premix;
and adding the organosilane into the premix solution and uniformly mixing to obtain a mixed solution.
5. The method according to claim 1, wherein,
the mass ratio of the phenolic resin prepolymer to the solvent is 1 (3-6);
the mass ratio of the curing agent to the phenolic resin prepolymer is 1 (15-25).
6. The method according to claim 1, wherein,
the fiber fabric is at least one of quartz fiber, glass fiber, carbon fiber, mullite fiber, alumina fiber and phenolic fiber.
7. The method according to claim 1, wherein,
the fiber fabric is at least one of needled felt, 2D woven cloth, 2.5D fabric and 3D fabric.
8. The method according to claim 1, wherein,
the temperature of the curing treatment is 150-180 ℃, and the curing time is 3-12 h.
9. The method according to claim 1, wherein,
the impregnation is vacuum impregnation.
10. The production method according to any one of claims 1 to 9, characterized by further comprising:
washing treatment and drying treatment are sequentially carried out after the curing treatment;
the solvent adopted in the washing treatment is deionized water and/or ethanol; the temperature of the washing treatment is 23-80 ℃, and the washing time is 2-8 hours;
the temperature of the drying treatment is 60-100 ℃.
11. A flexible ablative thermal protection composite prepared by the method of any one of claims 1 to 10.
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