CN106189066B

CN106189066B - Phenolic resin/silicon dioxide composite aerogel material and preparation method thereof

Info

Publication number: CN106189066B
Application number: CN201610523335.0A
Authority: CN
Inventors: 俞书宏; 于志龙; 杨宁
Original assignee: University of Science and Technology of China USTC
Current assignee: University of Science and Technology of China USTC
Priority date: 2016-07-04
Filing date: 2016-07-04
Publication date: 2020-08-25
Anticipated expiration: 2036-07-04
Also published as: CN106189066A

Abstract

The invention provides a phenolic resin/silicon dioxide composite aerogel material and a preparation method thereof, wherein the phenolic resin/silicon dioxide composite aerogel material has a nano-network structure formed by mutually intertwining a silicon dioxide phase and a resin phase; the organic silicon/chitosan composite material is prepared from materials including an organic silicon precursor, a phenolic compound, an aldehyde compound and chitosan by a sol-gel method and supercritical carbon dioxide drying. In the composite aerogel material provided by the invention, the organic phase and the inorganic phase are respectively continuous nanoscale entangled networks, and the composite aerogel material has the mechanical property of organic aerogel and the heat-insulating and fireproof capacity of silicon dioxide aerogel. The material with the thickness of 1cm can resist flame impact for more than 30min under the flame of a blast lamp at 1300 ℃ without causing inorganic phase shedding and separation, and can ensure that the temperature of a protected side does not exceed 300 ℃. The invention has simple operation and safe and reliable reaction, and can regulate and control the heat insulation and fire resistance of the obtained material through simple material ratio change.

Description

Phenolic resin/silicon dioxide composite aerogel material and preparation method thereof

Technical Field

The invention relates to the technical field of aerogel materials, in particular to a phenolic resin/silicon dioxide composite aerogel material and a preparation method thereof.

Background

Aerogel materials, a material with a three-dimensional network structure and ultra-low density, were first produced by Kistler, the american scientist, in 1931. Due to the unique three-dimensional structure and physical properties of aerogel, the aerogel is widely applied to the fields of building, aerospace and other high-tech fields as a fireproof and heat-insulating material. The currently reported aerogels with application prospects mainly comprise two types: 1. inorganic aerogel materials constructed from inorganic nanocells represented by silica aerogel, graphene oxide aerogel, and the like; 2. organic aerogel materials represented by polyurethane aerogel, phenol resin aerogel, and epoxy resin aerogel. However, the fire-retardant performance of common organic aerogels does not reach the fire-retardant level of inorganic aerogels; the application of common inorganic aerogel materials is limited by the extremely brittle mechanical properties, and the application puts new and higher requirements on material preparation and the like for researchers.

The rigid inorganic phase and the flexible organic phase are compounded, which provides a method with development prospect for improving the performance of materials such as aerogel and the like. For example, Journal of the American chemical society, 2014, 136 nd, 16066, reported that an ordered mesoporous structure is obtained by the co-assembly of an inorganic precursor and a block copolymer, and then an organic substance is polymerized in situ to obtain a porous organic-inorganic hybrid composite material rich in organic substance-containing microphase; U.S. Journal of Polymer Science (Journal of Polymer Science Part A: Polymer chemistry, 2003, 41 st, 905) reports the preparation of nanocomposites of phenolic thermoplastic resins with silica by the sol-gel method.

However, the above processes all have a significant problem in that phase separation between the organic and inorganic phases of the material cannot be avoided. In the continuous combustion process, along with the ablation of the organic phase, the inorganic phase can rapidly fall off due to the mesoscopic or macroscopic phase separation process between the two phases, so that the material cannot continuously maintain the heat-insulating and fireproof performance.

Disclosure of Invention

In view of the above, the present application provides a phenolic resin/silica composite aerogel material and a preparation method thereof, and the aerogel material provided by the present invention has excellent heat insulation and fire protection properties.

The invention provides a phenolic resin/silicon dioxide composite aerogel material, which is prepared by drying materials comprising an organic silicon precursor, a phenolic compound, an aldehyde compound and chitosan by a sol-gel method and supercritical carbon dioxide;

the phenolic resin/silica composite aerogel material has a nano-network structure in which a silica phase and a resin phase are entangled with each other.

Preferably, the phenolic resin/silica composite aerogelThe density of the material is 27-48 mg/cm³。

Preferably, the phenolic resin/silica composite aerogel material has a porosity of 97% or greater.

Preferably, the mass content of the silica in the phenolic resin/silica composite aerogel material is 20-90%.

The invention also provides a preparation method of the phenolic resin/silicon dioxide composite aerogel material, which comprises the following steps:

a) dispersing an organic silicon precursor and a phenolic compound in an aqueous solution in the presence of acid to hydrolyze the organic silicon precursor to obtain a mixed solution;

b) mixing the mixed solution with chitosan, an aldehyde compound and water to form sol, and then carrying out hydrothermal reaction to obtain phenolic resin/silicon dioxide composite hydrogel;

c) and (3) performing supercritical carbon dioxide drying on the phenolic resin/silicon dioxide composite hydrogel to obtain the phenolic resin/silicon dioxide composite aerogel material.

Preferably, in the step a), the acid is selected from one or more of formic acid, acetic acid and oxalic acid;

the organosilicon precursor is selected from at least one of tetraethyl orthosilicate and methyl orthosilicate.

Preferably, in the step a), the ratio of the volume of the acid, the volume of the organosilicon precursor, the amount of the phenolic compound to the volume of the aqueous solution is (0.2-0.8) mL: (1-8) mL: (0.01-0.02) mol: 30 mL.

Preferably, in the step a), the hydrolysis is performed at room temperature, and the hydrolysis time is 4-24 hours.

Preferably, the step c) is specifically:

and (3) carrying out solvent replacement on the phenolic resin/silicon dioxide composite hydrogel, and then carrying out supercritical carbon dioxide drying to obtain the phenolic resin/silicon dioxide composite aerogel material.

Preferably, the method further comprises the following steps:

d) and compressing the phenolic resin/silicon dioxide composite aerogel material to obtain the compressed phenolic resin/silicon dioxide composite aerogel material.

Compared with the prior art, the phenolic resin/silicon dioxide composite aerogel material provided by the invention has a nano network structure in which a silicon dioxide phase and a resin phase are mutually entangled, and is prepared from materials comprising an organic silicon precursor, a phenolic compound, an aldehyde compound and chitosan by a sol-gel method and supercritical carbon dioxide drying. In the composite aerogel material provided by the invention, the organic phase and the inorganic phase are respectively continuous nanoscale entangled networks, and the composite aerogel material has the mechanical property of organic aerogel and the heat-insulating and fireproof capacity of silicon dioxide aerogel. In the invention, the material with the thickness of 1cm can resist flame impact for more than 30min under the flame of a torch at 1300 ℃ without causing inorganic phase shedding and separation, and meanwhile, the temperature of the protected side can be ensured not to exceed 300 ℃, and the heat insulation and fire prevention performance is excellent.

Furthermore, the method is simple to operate, safe and reliable in reaction, capable of regulating and controlling the heat insulation and fire resistance of the obtained material through simple material proportion change, and suitable for large-scale industrial popularization.

Drawings

FIG. 1 is a photograph of a phenolic resin/silica double-network composite hydrogel prepared in example 1 of the present invention;

FIG. 2 is a photograph of a phenolic resin/silica dual network aerogel prepared in example 1 of the present invention;

FIG. 3 is a scanning electron micrograph of the phenolic resin/silica dual-network aerogel prepared in example 1 of the present invention;

FIG. 4 is a transmission electron micrograph of the phenolic resin/silica dual-network aerogel prepared in example 1 of the present invention;

FIG. 5 is a high-resolution transmission electron micrograph of the phenolic carbon/silica dual-network aerogel prepared in example 1 of the present invention;

FIG. 6 is a photograph showing resorcinol-formaldehyde resin/silica double-network composite hydrogel and aerogel prepared in example 2 of the present invention;

FIG. 7 is a scanning electron micrograph of the phenolic resin/silica dual-network aerogel prepared in example 3 of the present invention;

FIG. 8 is a transmission electron micrograph of the phenolic carbon/silica dual network aerogel prepared in example 3 of the present invention;

FIG. 9 is a scanning electron micrograph of the phenolic resin/silica dual-network aerogel prepared in example 4 of the present invention;

FIG. 10 is a TEM image of a phenolic carbon/silica dual-network aerogel prepared in example 4 of the present invention;

FIG. 11 is a scanning electron micrograph of the phenolic resin/silica dual-network aerogel prepared in example 5 of the present invention;

FIG. 12 is a TEM image of a phenolic carbon/silica dual-network aerogel prepared in example 5 of the present invention;

FIG. 13 is a graph of density variation data for phenolic resin/silica dual network aerogels of varying silicon content prepared according to examples of the present invention;

FIG. 14 is a thermogravimetric analysis of phenolic resin/silica dual network aerogels of different silicon content prepared according to examples of the present invention;

FIG. 15 is a graph of the mechanical compressive stress strain of phenolic resin/silica dual network aerogels of different silicon content prepared according to examples of the present invention;

FIG. 16 is a photograph of a physical comparison of an uncompressed aerogel material prepared in example 1 and a compressed phenolic resin/silica dual network aerogel of example 7;

FIG. 17 is a schematic view of a fire resistance testing apparatus according to an embodiment of the present invention;

FIG. 18 is a photograph of a fire resistance test of an aerogel material according to an embodiment of the present invention;

FIG. 19 is a graph of temperature versus time for the backfire side of an uncompressed aerogel material of example 1;

FIG. 20 is a graph of temperature versus time for the backfire side of an aerogel material after compression in example 7;

FIG. 21 is a photograph of an ablated comparison of an uncompressed aerogel material of example 1 and a compressed aerogel of example 7;

FIG. 22 shows the ablation of the phenolic aerogel prepared in the comparative example.

Detailed Description

The technical solutions in the embodiments of the present invention are clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and 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 invention provides a phenolic resin/silicon dioxide composite aerogel material, which is prepared by drying materials comprising an organic silicon precursor, a phenolic compound, an aldehyde compound and chitosan by a sol-gel method and supercritical carbon dioxide; the phenolic resin/silica composite aerogel material has a nano-network structure in which a silica phase and a resin phase are entangled with each other.

The phenolic resin/silicon dioxide composite aerogel material provided by the invention has both ultralow density and excellent heat-insulating, fireproof and ablation-resistant performances, and is beneficial to application.

The phenolic resin/silicon dioxide composite aerogel material provided by the invention has a nano-network structure in which a silicon dioxide phase and a resin phase are mutually entangled, namely, an organic phase and an inorganic phase are respectively continuous nano-scale entangled networks, and the microscopic nano-double-network structure is unique and novel. The material is phenolic resin/silicon dioxide double-network aerogel, the silicon dioxide network and the resin network are entangled with each other, and the material has the mechanical property of organic aerogel and the heat-insulating and fireproof capacity of the silicon dioxide aerogel. In the double-network aerogel with different proportions, the content of silicon dioxide is different, and the more the organic silicon precursor is added, the higher the content of the silicon dioxide network in the obtained double-network aerogel is. In the phenolic resin/silicon dioxide composite aerogel material, the mass content of silicon dioxide is preferably 20-90%, and more preferably 22-85%. According to the embodiment of the invention, the content of silicon dioxide in the obtained material can be basically controlled to be 22.9-82.5% through different proportions.

In bookIn some embodiments of the invention, the network fiber thickness of the double-network aerogel is 10nm to 20 nm. In some embodiments of the invention, the phenolic resin/silica composite aerogel material has a density of 27-48 mg/cm³Preferably 30 to 40mg/cm³. The porosity of the phenolic resin/silica composite aerogel material is preferably above 97%, such as 97.1%, 97.8%, 98%, etc. In some embodiments of the invention, the specific surface area of the phenolic resin/silicon dioxide composite aerogel material can be 155-450 m²/g。

In the invention, the phenolic resin/silicon dioxide composite aerogel material is prepared from materials including an organic silicon precursor, a phenolic compound, an aldehyde compound and chitosan by a sol-gel method and supercritical carbon dioxide drying. Wherein the organosilicon precursor is preferably at least one selected from tetraethyl orthosilicate and methyl orthosilicate. The phenolic compound is preferably one or more of phenol, resorcinol and phloroglucinol in any proportion, and is more preferably phenol or resorcinol. The aldehyde compound is preferably one or more selected from formaldehyde, paraformaldehyde and acetaldehyde, and more preferably formaldehyde. In an embodiment of the present invention, the chitosan may be a commercially available product of Shanghai pharmaceutical group.

According to the phenolic resin/silica double-network aerogel provided by the invention, due to the introduction of two mutually entangled nano-network structures of an organic phase and an inorganic phase, the problem of brittle fracture of the traditional silica aerogel in the compression process is effectively improved, and meanwhile, the fireproof capacity of the traditional organic aerogel is greatly enhanced. In the double-network aerogel, the phase separation process between the organic phase and the inorganic phase is in a nano scale and has stronger interaction, so that the inorganic phase cannot be peeled off due to the sintering loss of the organic phase in the ablation process of high-temperature flame, the service life of the material is prolonged, and the application range of the material is greatly expanded. The novel aerogel can be pre-compressed to improve the mechanical property of the material, reduce the occupied volume and the use volume of the material in the transportation process, and simultaneously can further enhance the ablation resistance of the material.

The preparation method provided by the invention can be used for preparing the phenolic resin/silicon dioxide dual-network aerogel material with excellent heat insulation, fire prevention and ablation resistance, is simple and reliable, has the advantages of easily available raw materials, low price and less time consumption, and is suitable for large-scale industrial popularization and application.

According to the embodiment of the invention, the water-containing solution, the phenolic compound, the organic silicon precursor and the acid can be added into the reactor for hydrolysis, and after the hydrolysis is finished, a mixed solution is obtained and is marked as solution A. The reactor can be a beaker commonly used in the field, and the organic silicon precursor is hydrolyzed by sealing and stirring after being added; the present invention is also not particularly limited with respect to the order of addition.

In the present invention, the organosilicon precursor is preferably at least one selected from tetraethyl orthosilicate and methyl orthosilicate. The phenolic compound is preferably one or more of phenol, resorcinol and phloroglucinol in any proportion, and is more preferably phenol or resorcinol. The acid is preferably selected from one or more of formic acid, acetic acid and oxalic acid, more preferably acetic acid (glacial acetic acid).

In the embodiment of the invention, the acid, the organic silicon precursor and the phenolic compound can be dispersed in the aqueous solution, and are stirred to generate hydrolysis reaction, so that hydrogen bond action is generated between the inorganic monomer and the organic monomer, and prepolymerization is promoted. The aqueous solution is preferably water or a mixed solution of water/absolute ethanol, more preferably a mixed solution of water and absolute ethanol. In a preferred embodiment of the present invention, the volume fraction of the absolute ethyl alcohol in the water/absolute ethyl alcohol mixed solution may be 1/3-3/4, and is preferably 1/2-3/4. In some embodiments of the present invention, the ratio of the volume of the acid, the volume of the silicone precursor, the amount of the phenolic compound, and the volume of the aqueous solution is preferably (0.2-0.8) mL: (1-8) mL: (0.01-0.02) mol: 30mL, more preferably (0.6-0.8) mL: (4-6) mL: (0.01-0.02) mol: 30 mL.

In the present invention, the time for hydrolysis of the organosilicon precursor is preferably 4 to 24 hours, more preferably 8 to 24 hours, and most preferably 16 to 24 hours. The hydrolysis process of the organic silicon precursor can be carried out at room temperature, and is not specially limited, nor is special temperature regulation and control required; in general, the room temperature range is understood to be 15 to 30 ℃.

After the mixed solution (solution a) is obtained, the mixed solution is mixed with chitosan, aldehyde compound and water, and after uniform stirring, sol is formed. The invention preferably mixes the solution A and the chitosan solution, adds the aldehyde compound into the mixture, and stirs the mixture vigorously for a certain time to form sol.

Wherein the chitosan solution can be obtained by dispersing chitosan in water and stirring uniformly, and can be marked as solution B. In an embodiment of the present invention, the chitosan may be a commercially available product of Shanghai pharmaceutical group. The chitosan sol network is used as a template to support organic monomers and inorganic monomers to promote gelling. In the solution B, the ratio of the mass of the chitosan to the volume of water is preferably (0.1-0.5) g: 15mL, more preferably (03-0.5) g: 15 mL. .

The invention preferably pours the solution A into the solution B quickly, stirs, then adds the aldehyde compound solution, stirs vigorously for 10min, forms the mixed sol. The aldehyde compound is preferably one or more selected from formaldehyde, paraformaldehyde and acetaldehyde, and more preferably formaldehyde. In some embodiments of the invention, a 37 wt% formaldehyde solution may be used. In the embodiment of the present invention, the aldehyde compound is preferably used in an amount of 0.02 to 0.04 mol.

After the sol is obtained, the sol is put into a hydrothermal reaction kettle and placed in a drying oven for hydrothermal reaction to obtain the phenolic resin/silicon dioxide composite hydrogel. Wherein, the hydrothermal reaction kettle is preferably a reaction kettle with a polytetrafluoroethylene lining. The invention adopts a hydrothermal synthesis method to directly copolymerize organic matters and inorganic matters on a chitosan gel frame to obtain the composite hydrogel. The temperature of the hydrothermal reaction is preferably 100-200 ℃, and more preferably 100-160 ℃; the time for the hydrothermal reaction is preferably 8 to 24 hours, and more preferably 10 to 16 hours.

After obtaining the composite hydrogel, the inventive example passed it through supercritical carbon dioxide (CO)₂) The drying method comprises the steps of replacement drying, effective removal of the solvent in the hydrogel, and reservation of the gel network structure, so as to obtain the organic-inorganic hybrid double-network aerogel, namely the phenolic resin/silicon dioxide composite aerogel material. The essence of the supercritical carbon dioxide drying technology is that the solvent in the hydrogel is replaced by supercritical carbon dioxide to achieve the aim of drying the gel; under the conditions that the temperature is higher than the critical temperature and the pressure is higher than the critical pressure, the supercritical carbon dioxide can be obtained, and the material is dried.

According to the invention, the phenolic resin/silicon dioxide composite hydrogel is preferably subjected to solvent replacement and then supercritical carbon dioxide drying to obtain the phenolic resin/silicon dioxide composite aerogel material. Specifically, in the embodiment of the invention, the phenolic resin/carbon dioxide double-network composite hydrogel is soaked in an organic solvent for multiple replacement operations, the solvent in the double-network composite hydrogel is replaced, the material is taken, and supercritical drying is performed to obtain the phenolic resin/carbon dioxide double-network aerogel. Wherein, the organic solvent is preferably acetone or absolute ethyl alcohol. The replacement times and time are different according to materials and experimental conditions, the completion standard of changing the color of the replaceable organic solvent from reddish brown or brownish yellow to colorless is adopted, the supercritical carbon dioxide drying technology is not particularly limited, the used temperature can be 55 ℃, and the pressure is 100 atm.

The present invention preferably further comprises: and compressing the phenolic resin/silicon dioxide composite aerogel material to obtain the compressed phenolic resin/silicon dioxide composite aerogel material.

The invention can further reduce the size of the internal voids of the aerogel by a compression method, and the method can not only achieve the purpose of enhancing the strength of the aerogel framework, but also further enhance the heat-insulating, fireproof and ablation-resistant capabilities of the material, and also reduce the occupied volume and the use volume of the material in the transportation process. The compression rate of the compression is preferably 1-5 mm/min, and more preferably 2-5 mm/min.

After the phenolic resin/silicon dioxide composite aerogel material is obtained, the performance of the phenolic resin/silicon dioxide composite aerogel material is tested by the invention. Through tests, the density of the phenolic resin/silicon dioxide double-network aerogel prepared by the method is only 27-48 mg/cm³Has thermal conductivity lower than that of air and excellent fire resistance. When the original double-network aerogel with the thickness of 2cm is compressed to the thickness of 1cm, the material is still well preserved, the shock resistance can be over 30min under the flame of a torch at 1300 ℃, the temperature of the protected side can be ensured not to exceed 300 ℃, and the basic standard of aerospace materials can be met.

The invention has simple operation and safe and reliable reaction, can be prepared in large quantities, and can regulate and control the heat insulation and fire resistance of the obtained material through simple material proportion change; the material prepared by the invention has excellent heat insulation and fire resistance, can reduce the transportation and use volume through pre-compression, improves the ablation resistance, and has wider application prospect compared with the traditional aerogel material.

For further understanding of the present application, the phenolic resin/silica composite aerogel materials provided herein and methods for making the same are specifically described below with reference to the examples.

In the following examples, the raw materials are generally commercially available; the supercritical carbon dioxide dryer is Speed-ed SFE-helix, drying temperature is 55 deg.C, and pressure is 100 atm.

Example 1

The phenolic resin/silica double-network aerogel of the embodiment is prepared by the following steps:

a. adding 15mL of water and 15mL of absolute ethyl alcohol into a beaker with the volume of 50mL, adding 1.882g of phenol, 6mL of tetraethyl orthosilicate and 0.6mL of glacial acetic acid, sealing, stirring at room temperature for 24h, and hydrolyzing, wherein the obtained mixed solution is marked as solution A;

b. in another beaker, 0.45g of chitosan (Shanghai pharmaceutical group, CAS number: 9012-76-4) was dispersed in 15mL of water, and the resulting chitosan solution was designated as solution B;

rapidly pouring the solution A into the solution B, adding 3mL of formaldehyde solution (37 wt% formaldehyde), and continuously and violently stirring for 10min to form sol;

and (3) putting the sol into a 50mL hydrothermal reaction kettle with a polytetrafluoroethylene lining, putting the hydrothermal reaction kettle into a drying oven at 160 ℃, and carrying out hydrothermal reaction for 10h to obtain yellow phenolic resin/silicon dioxide double-network composite hydrogel (hybrid gel).

c. And immersing the hybrid gel in acetone for three days, replacing new acetone every day until the acetone is colorless, then taking out the replaced hybrid gel, and drying by supercritical carbon dioxide to obtain the phenolic resin/silicon dioxide double-network aerogel.

Fig. 1 and 2 show the photos of the phenolic resin/silica double-network composite hydrogel and the aerogel obtained in this example, where fig. 1 is the photo of the phenolic resin/silica double-network composite hydrogel prepared in example 1 of the present invention, and fig. 2 is the photo of the phenolic resin/silica double-network aerogel prepared in example 1 of the present invention.

The phenolic resin/silica double-network aerogel prepared in example 1 is denoted as PS-6, a scanning electron micrograph of the phenolic resin/silica double-network aerogel is shown in fig. 3, and fig. 3 is a scanning electron micrograph of the phenolic resin/silica double-network aerogel prepared in example 1 of the present invention. The transmission electron microscope photo is shown in fig. 4, and fig. 4 is the transmission electron microscope photo of the phenolic resin/silica double-network aerogel prepared in example 1 of the present invention.

In order to facilitate observation and testing, the dual-network aerogel is subjected to high-temperature carbonization in the embodiment, and the carbonization conditions are as follows: raising the temperature to 800 ℃ at the speed of 5 ℃/min under the protection of nitrogen atmosphere, and carbonizing for 2h at the temperature of 800 ℃. The carbonized dual-network aerogel is observed by a high-resolution transmission electron microscope, and as shown in fig. 5, fig. 5 is a high-resolution transmission electron microscope photograph of the phenolic resin carbon/silica dual-network aerogel prepared in example 1 of the present invention. As can be seen from FIG. 5, the network fiber thickness of the double-network aerogel prepared in this example is 10nm to 20nm, and the silica network and the resin carbon network are entangled with each other.

Example 2

The same preparation method as in example 1 was used:

a. adding 10mL of water and 20mL of absolute ethyl alcohol into a beaker with the volume of 50mL, adding 2.202g of resorcinol, 6mL of methyl orthosilicate and 0.6mL of glacial acetic acid, sealing, stirring at room temperature for 24h, and hydrolyzing, wherein the obtained mixed solution is marked as solution A;

and (3) putting the sol into a 50mL hydrothermal reaction kettle with a polytetrafluoroethylene lining, putting the hydrothermal reaction kettle into a drying oven at 100 ℃, and carrying out hydrothermal reaction for 10h to obtain the resorcinol-formaldehyde resin/silicon dioxide double-network composite hydrogel (hybrid gel).

c. Immersing the hybrid gel in acetone for three days, replacing new acetone every day until the acetone is colorless, then taking out the replaced hybrid gel, and drying by supercritical carbon dioxide to obtain the resorcinol-formaldehyde resin/silicon dioxide double-network aerogel.

Fig. 6 is a photograph showing an example of the resorcinol-formalin resin/silica double-network composite hydrogel and aerogel obtained in this example, and fig. 6 is a photograph showing an example of the resorcinol-formalin resin/silica double-network composite hydrogel and aerogel prepared in example 2 of the present invention.

Examples 3 to 5

Using the same preparation method as in example 1, 2mL, 4mL and 8mL of tetraethyl orthosilicate were added in step a, respectively; the obtained phenolic resin/silicon dioxide double-network aerogel is respectively marked as PS-2, PS-4 and PS-8.

Scanning electron micrographs and transmission electron micrographs of the resulting aerogel materials are shown in figures 7 to 12, respectively, FIG. 7 is a scanning electron micrograph of the phenolic resin/silica dual-network aerogel prepared in example 3 of the present invention, FIG. 8 is a transmission electron micrograph of the phenolic resin carbon/silica dual-network aerogel prepared in example 3 of the present invention, FIG. 9 is a scanning electron micrograph of the phenolic resin/silica dual-network aerogel prepared in example 4 of the present invention, FIG. 10 is a TEM image of a phenolic resin carbon/silica double-network aerogel prepared in example 4 of the present invention, FIG. 11 is a scanning electron micrograph of the phenolic resin/silica dual-network aerogel prepared in example 5 of the present invention, FIG. 12 is a TEM image of a phenolic carbon/silica dual-network aerogel prepared in example 5 of the present invention.

Example 6

1. The specific surface areas (S) of the following materials were measured by nitrogen adsorption analysis, BET specific surface area test method_BET) Pore volume (V)_pore) Average void width (APW) and porosity. The results are shown in table 1, where table 1 shows the porosity and the like of the phenolic resin carbon/silica dual-network aerogel prepared in examples 1 and 3 to 5.

TABLE 1 porosity, etc. of phenolic carbon/silica dual network aerogels prepared in examples 1 and 3-5

Sample numbering	PS-2	PS-4	PS-6	PS-8
					S_BET(m²/g)	157.6	408.9	400	399
V_pore(cm³/g)	0.903	0.74	0.72	0.67
					APW(nm)	22.9	9.2	10.1	9.02
Porosity (%)	98	97.9	97.8	97.1

As is clear from the above data in Table 1, the sample having the largest specific surface area is PS-4, which is 408.9m²(ii)/g; the sample with the highest porosity was PS-2, 98%; meanwhile, the porosity of all samples is more than 97%, which shows that the aerogel material synthesized by the invention has very high porosity.

2. The density of the phenolic resin carbon/silica dual network aerogels prepared in examples 1 and 3-5 was calculated by testing the weight and volume of the aerogel, 5 for each set of data, and the average value was calculated. The results are shown in FIG. 13, and FIG. 13 shows the present inventionFigure is a graph showing density variation data for the phenolic resin/silica dual network aerogels of different silicon content prepared in the examples. As can be seen from the aerogel density graph, as the content of the organosilicon precursor increases, the density of the obtained phenolic resin/silica double-network aerogel also increases, and basically shows a linear change. The density of the phenolic resin/silicon dioxide double-network aerogel prepared by the method is only 27-48 mg/cm³And has ultra-low density.

Thermogravimetric analysis is carried out on the phenolic resin carbon/silicon dioxide dual-network aerogel prepared in the embodiments 1 and 3-5 by adopting a thermogravimetric analyzer, and the test conditions are as follows: the combustion temperature is 800 ℃, the heating rate is 10 ℃/min, and the atmosphere is air. The results are shown in fig. 14, and fig. 14 is a thermogravimetric analysis graph of the phenolic resin/silica dual-network aerogels with different silicon contents prepared by the embodiment of the invention. According to thermogravimetric analysis graphs, the content of silicon dioxide in the double-network aerogel obtained by different proportions is different. The more the organosilicon precursor is added, the higher the content of the silicon dioxide network in the obtained double-network aerogel is; through different proportions, the content of the silicon dioxide in the obtained material can be basically controlled between 22.9% and 82.5%.

Through mechanical tester (model Instron 5565A), carry out compressive stress strain test to the phenolic resin carbon/silica dual network aerogel of

embodiment

1 and 3 ~ 5 preparation, specifically include: the sample was placed on the test platform with a compression sensor size of 500N and a compression rate of 2 mm/min. The results are shown in fig. 15, and fig. 15 is a graph of mechanical compressive stress strain of the phenolic resin/silica dual-network aerogel with different silicon contents prepared by the example of the invention. According to the compressive stress-strain curve of the aerogel material, the mechanical property of the aerogel material prepared by the embodiment of the invention shows unrecoverable plastic deformation. Meanwhile, the more the organosilicon precursor is added, the higher the compression modulus of the obtained phenolic resin/silicon dioxide double-network aerogel material is, and the stronger the rigidity of the material is.

According to the test results, due to the different amounts of the added organosilicon precursors, the obtained double-network aerogel has different densities and mechanical properties.

Example 7

The aerogel material was precompressed at a compression rate of 2mm/min and a compression strain of 50% by the same preparation method as in example 1, to prepare a compressed phenol resin/silica double-network aerogel material. A photograph of an uncompressed aerogel of example 1 and a compressed phenolic resin/silica dual network aerogel of example 7 is shown in fig. 16, and fig. 16 is a photograph of an uncompressed aerogel material prepared in example 1 and a compressed phenolic resin/silica dual network aerogel of example 7.

Example 8

In order to better simulate the practical use environment of the thermal insulation and fire prevention material and further illustrate the excellent performance of the phenolic resin/silica dual-network aerogel prepared by the invention, in this embodiment, a propane/butane torch is used to ablate the aerogel materials which are not compressed in embodiment 1 and are compressed in embodiment 7, and an infrared thermal imager is used to record the temperature change of the back fire side of the aerogel material in the ablation process in real time.

Fig. 17 is a schematic view of the entire fire resistance testing apparatus, fig. 18 is a test photograph, fig. 17 is a schematic view of the fire resistance testing apparatus according to the embodiment of the present invention, and fig. 18 is a test photograph of the fire resistance of the aerogel material according to the embodiment of the present invention. Example 1 the condition of the backfire side of an uncompressed aerogel material is shown in fig. 19, where fig. 19 is a plot of the temperature of the backfire side of an uncompressed aerogel material of example 1 as a function of time; the condition of the back fire side of the compressed aerogel material of example 7 is shown in fig. 20, and fig. 20 is a graph of the temperature of the back fire side of the compressed aerogel material of example 7 over time. A comparison photograph of an uncompressed and compressed phenolic resin/silica dual network aerogel after 30min of ablation is shown in fig. 21, and fig. 21 is a comparison photograph of an uncompressed aerogel material from example 1 and an ablated aerogel from example 7.

As can be seen from fig. 19 and 20, the back side temperature of the uncompressed dual network aerogel of 2cm thickness was slowly raised from room temperature to about 300 ℃ and gradually approached constant temperature within 20min under continuous heating of the 1300 ℃ torch flame, and the average temperature of the back side of the material reached 310 ℃ after 20 minutes of combustion; after 50% compression of a 2cm thick dual network aerogel, the average temperature of the backside was only 260 ℃ during the 30 minute 1300 ℃ torch flame ablation process, while the backside surface was not yet carbonized. It is worth noting that as shown in fig. 21, the anti-ablation performance of the compressed double-network aerogel is further improved, and the densification of the network is caused by the compression, so that the silica on the side of the material resisting flame impact does not fall off, which also greatly improves the service life and the heat-insulating, fireproof and anti-ablation capabilities of the phenolic resin/silica double-network aerogel material.

Comparative example

In a beaker with a volume of 100mL, 0.45g of chitosan (Shanghai nationality group, CAS number: 9012-76-4) is dispersed in 30mL of water, and then 0.6mL of acetic acid is added and stirred to obtain colorless and transparent chitosan sol;

adding 9.411g of liquid phenol into the chitosan sol, fully and quickly stirring and uniformly mixing to form white emulsion, quickly adding 3mL of formaldehyde solution (37 wt% of formaldehyde), and keeping stirring quickly and uninterruptedly to obtain mixed sol;

putting the mixed sol into a 50mL hydrothermal kettle, placing the kettle in a drying oven at 160 ℃, and carrying out hydrothermal reaction for 10h to obtain phenolic resin organogel, which can be called organogel;

immersing the organogel in acetone for three days, replacing new acetone every day until acetone is colorless, taking out the replaced organogel, and performing supercritical CO₂And drying to obtain the phenolic resin aerogel.

The obtained phenolic resin aerogel is put on an alcohol lamp to be ablated, and the temperature of the alcohol lamp is 500-600 ℃. The ablation of the material is shown in fig. 22, fig. 22 is the ablation of the phenolic aerogel prepared in the comparative example, and it can be seen from fig. 22 that the phenolic aerogel is completely ablated by the alcohol burner flame within two minutes.

As can be seen from the above examples and comparative examples, the phenolic resin/silica double-network aerogel material prepared by the invention has both low density and excellent heat-insulating, fireproof and ablation-resistant properties, can be ablated for a long time under a blast lamp without being damaged, and can further improve the ablation-resistant properties of the material by a compression method on the premise of keeping the structural integrity of the material. The invention can also regulate the density, the mechanical property, the heat-insulating and fireproof performance and the like of the obtained aerogel material by regulating the relative proportion of the organic phase and the inorganic phase. The invention has simple operation and safe and reliable reaction.

The above description is only a preferred embodiment of the present invention, and it should be noted that various modifications to these embodiments can be implemented by those skilled in the art without departing from the technical principle of the present invention, and these modifications should be construed as the scope of the present invention.

Claims

1. A phenolic resin/silicon dioxide composite aerogel material is prepared by using a sol-gel method to obtain phenolic resin/silicon dioxide composite hydrogel from materials comprising an organic silicon precursor, a phenolic compound, an aldehyde compound and chitosan in the presence of acid, and drying by using supercritical carbon dioxide;

the phenolic resin/silicon dioxide composite aerogel material has a nano-network structure formed by mutually intertwining a silicon dioxide phase and a resin phase, and the density of the phenolic resin/silicon dioxide composite aerogel material is 27-48 mg/cm³。

2. The aerogel material of claim 1, wherein the phenolic resin/silica composite aerogel material has a porosity of 97% or greater.

3. The aerogel material of claim 1, wherein the phenolic resin/silica composite aerogel material comprises 20-90% silica by weight.

4. A preparation method of a phenolic resin/silicon dioxide composite aerogel material comprises the following steps:

5. The method according to claim 4, wherein in the step a), the acid is one or more selected from formic acid, acetic acid and oxalic acid;

6. The method according to claim 5, wherein in the step a), the ratio of the volume of the acid, the volume of the organosilicon precursor, the amount of the phenolic compound to the volume of the aqueous solution is (0.2 to 0.8) mL: (1-8) mL: (0.01-0.02) mol: 30 mL.

7. The method according to claim 4, wherein the hydrolysis is performed at room temperature in step a), and the hydrolysis time is 4 to 24 hours.

8. The preparation method according to claim 4, wherein the step c) is specifically:

9. The method according to any one of claims 4 to 8, further comprising: