Phthalonitrile aerogel as well as preparation method and application thereof

Abstract

The invention discloses a phthalonitrile aerogel as well as a preparation method and application thereof. The phthalonitrile aerogel is prepared from phthalonitrile resin through a sol-gel method and normal-pressure drying; a three-dimensional network structure formed by an addition polymerization reaction of a phthalonitrile monomer under the action of heating or a curing agent can resist the action of surface tension when a solvent is volatilized, so that the problems of shrinkage, collapse, cracking and the like caused by the aerogel in a normal-pressure drying process are effectively relieved, and the aerogel can show an extremely low shrinkage rate; on the basis of maintaining low thermal conductivity and good high temperature resistance, the mechanical strength and processability of the phthalonitrile aerogel material are improved. The preparation method of the phthalonitrile aerogel is simple, the shrinkage rate is low, the mechanical strength is high, and the requirements of future aircrafts for novel aerogel can be met.

Description

Technical Field

[0001] The invention belongs to the technical field of aerogels and relates to a novel aerogel material, in particular to a phthalonitrile aerogel and a preparation method and application thereof. Background Art

[0002] Aerogel was first discovered by KISTLER in the United States in 1931. It is blue in appearance, so it is also called "blue smoke" or "frozen smoke". Due to the unique structure and properties of aerogel, it has broad application prospects in the field of thermal insulation. Compared with other traditional thermal insulation materials, aerogel has more outstanding thermal insulation performance. It can effectively reduce heat conduction and thus improve the thermal insulation effect. In addition, the low density of aerogel makes it lightweight, which is conducive to reducing the weight of the overall structure to improve the flexibility of engineering design. Therefore, it is widely used in thermal insulation, sound insulation, aerospace, biomedicine and other fields.

[0003] Generally, the process of preparing aerogels by sol-gel method and normal pressure drying is as follows: First, the precursor disperses colloidal particles in the solvent, and then the colloidal particles are connected to each other to form a wet gel with a three-dimensional network structure. During the drying process, the solvent is removed from the wet gel and the colloidal network structure is retained, and finally the aerogel material is obtained. However, traditional aerogels have the following two defects when applied: one is the high shrinkage rate during the drying process, and the other is the relatively low mechanical strength. Therefore, its application development is limited.

[0004] In order to solve the above problems, the current research direction is mainly focused on optimizing the preparation process and improving the material properties. For example, by adjusting the drying conditions, exploring new surface modification methods and introducing reinforcing materials, the shrinkage of aerogels can be effectively reduced and their mechanical strength can be improved, thereby expanding their application in different fields. In view of the low maintenance and reusable requirements of future spacecraft, it is particularly important to develop lightweight, durable, and high temperature resistant insulation materials. Summary of the invention

[0005] In order to improve the above technical problems, the present invention provides a phthalonitrile aerogel and a preparation method and application thereof, so as to solve the problem that in the process of preparing organic aerogel by normal pressure drying in the prior art, the brittleness and shrinkage rate caused by highly cross-linked molecular chains cannot meet the requirements of aircraft for mechanical properties, heat resistance and thermal insulation properties.

[0006] In order to achieve the above-mentioned object of the invention, the present invention adopts the following technical solutions:

[0007] The present invention provides a method for preparing phthalonitrile aerogel, comprising the following steps:

[0008] (1) mixing phthalonitrile monomer and ionic liquid to obtain a first mixed solution;

[0009] (2) adding a curing agent to the first mixed solution to obtain a second mixed solution;

[0010] (3) solidifying the second mixed liquid to obtain a wet gel;

[0011] (4) The wet gel is taken out and placed in a low-boiling point solvent for solvent replacement, and after drying, phthalonitrile aerogel is obtained.

[0012] According to an embodiment of the present invention, in step (1), the mixing is specifically, for example, stirring at a certain temperature (e.g., 100-140°C, specifically, for example, 100°C, 110°C, 120°C, 130°C or 140°C) for a certain time (e.g., 10-60 min) until the phthalonitrile is completely dissolved.

[0013] According to an embodiment of the present invention, in step (1), the mass fraction of the first mixed liquid is 20%-40%.

[0014] According to an embodiment of the present invention, in step (1), the phthalonitrile monomer is selected from compounds having a structure shown in formula (1) or formula (2):

[0015]

[0016] Wherein, R is selected from any one of the following structures:

[0017]

[0018] Among them, R 1 , R 2 , R 3 The same or different, each independently selected from -H, -CH 3 、-CH 2 CH 3 、-CH(CH 3 ) 2 , -OH, -F, -CF 3 etc.; For example, R 1 , R 2 , R 3 Same, selected from -H;

[0019] n is selected from integers of 0-20, preferably from integers of 0-10.

[0020] Preferably, R is selected from any one of the following structures:

[0021]

[0022] Exemplarily, R is selected from any one of the following structures:

[0023]

[0024] Illustratively, in step (1), the phthalonitrile monomer is selected from compounds having structures represented by formula (3), formula (4) or formula (5):

[0025]

[0026]

[0027] Wherein: n is selected from an integer of 0-20, preferably an integer of 0-10.

[0028] According to an embodiment of the present invention, in step (1), the ionic liquid is one or a mixture of 1-butyl-3-methylimidazolium tetrafluoroborate, 1-butyl-3-methylimidazolium chloride, 1-ethyl-3-methylimidazolium trifluoromethanesulfonate and 1,3-dimethylimidazolium tetrafluoroborate.

[0029] According to an embodiment of the present invention, in step (1), the mass ratio of the phthalonitrile monomer to the ionic liquid is (15-70):100, exemplified by 15:100, 25:100 (1:4), 33.3:100 (1:3), 43:100 (3:7), 54:100 (7:13), and 67:100 (2:3).

[0030] According to an embodiment of the present invention, step (2) specifically comprises: adding a curing agent to the first mixed liquid, stirring and dissolving the curing agent, and obtaining a second mixed liquid.

[0031] According to an embodiment of the present invention, in step (2), the curing agent is selected from one or a mixture of zinc chloride, cupric chloride, 4,4'-diaminodiphenyl sulfone and 4,4'-bis(3-aminophenoxy)diphenyl sulfone, preferably 4,4'-bis(3-aminophenoxy)diphenyl sulfone.

[0032] According to an embodiment of the present invention, in step (2), the molar ratio of the phthalonitrile monomer to the curing agent is 10:(0.1-2), exemplified by 10:0.1, 10:0.5, 10:1, 10:2.

[0033] According to an embodiment of the present invention, in step (3), the curing is performed at 250-325° C. under closed conditions, for example.

[0034] According to an embodiment of the present invention, in step (3), the curing is carried out by a gradient heating method. For example, the gradient heating process includes a first stage heating and a second stage heating. Preferably, the first stage is heated to a curing temperature of 150-250°C, exemplarily 200°C, and the first stage curing time is 1 to 24h, exemplarily 12h; the second stage is heated to a curing temperature of 250-325°C, exemplarily 250°C, and the second stage curing time is 1 to 10h, exemplarily 4h.

[0035] According to an embodiment of the present invention, in step (4), the low boiling point solvent is one or more of anhydrous ethanol, ethylene glycol, n-butanol, and n-heptane.

[0036] The present invention also provides a phthalonitrile aerogel prepared by the phthalonitrile aerogel preparation method.

[0037] The present invention also provides applications of the phthalonitrile aerogel in the fields of thermal insulation, sound insulation, aerospace (such as spacecraft), biomedicine, etc.

[0038] The present invention also provides a thermal insulation material, which contains the above-mentioned phthalonitrile aerogel or is prepared from the above-mentioned phthalonitrile aerogel.

[0039] Beneficial effects of the present invention:

[0040] (1) The phthalonitrile aerogel of the present invention is formed by addition polymerization of phthalonitrile monomer under heating or curing agent. During the whole heat curing process, the formation of resin is not accompanied by the release of small molecules, so the obtained phthalonitrile aerogel has a complete structure and few defects. After curing, the rigid benzene ring is converted into a polymer containing triazine rings and aromatic heterocycles such as phthalocyanine, thereby giving the phthalonitrile aerogel material excellent heat resistance, flame retardancy and mechanical properties.

[0041] (2) The present invention uses phthalonitrile resin as the base resin. The three-dimensional network structure formed during the curing process of phthalonitrile can resist the effect of surface tension when the solvent evaporates, thereby effectively alleviating the shrinkage, collapse and cracking problems caused by the aerogel during the normal pressure drying process, and thus can show an extremely low shrinkage rate.

[0042] (3) The phthalonitrile aerogel prepared by the present invention using phthalonitrile resin through a sol-gel method and normal pressure drying not only greatly reduces the shrinkage rate, but also improves the mechanical strength and processing performance of the phthalonitrile aerogel material while maintaining low thermal conductivity and good high temperature resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1This is a macroscopic morphology of the phthalonitrile aerogel prepared in Example 1;

[0044] Figure 2 This is a microscopic morphology of the phthalonitrile aerogel prepared in Example 1. DETAILED DESCRIPTION

[0045] The technical scheme of the present invention will be further described in detail below in conjunction with specific embodiments. It should be understood that the following embodiments are only exemplary descriptions and explanations of the present invention and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are included in the scope that the present invention is intended to protect.

[0046] Unless otherwise specified, the raw materials and reagents used in the following examples are commercially available or can be prepared by known methods.

[0047] Example 1

[0048] A method for preparing phthalonitrile aerogel comprises the following steps:

[0049] Step 1: mixing phthalonitrile of the structure shown in formula (3) and 1-butyl-3-methylimidazole chloride at a mass ratio of 1:4 at 120° C., stirring for 30 minutes until completely dissolved, to obtain a phthalonitrile solution of the structure shown in formula (3) with a mass fraction of 20%; adding 4,4'-bis(3-aminophenoxy)diphenyl sulfone to the phthalonitrile solution of the structure shown in formula (3), wherein the molar ratio of 4,4'-bis(3-aminophenoxy)diphenyl sulfone to the phthalonitrile of the structure shown in formula (3) is 1:10, and stirring until completely dissolved;

[0050]

[0051] Step 2: After curing at 200°C for 12 hours under closed conditions, continue curing at 250°C for 4 hours to obtain a wet gel; take out the wet gel and place it in anhydrous ethanol solvent for replacement at room temperature for 24 hours. After the wet gel is taken out and dried at room temperature for 24 hours, phthalonitrile aerogel is obtained.

[0052] Figure 1 and Figure 2The macroscopic and microscopic morphology of the phthalonitrile aerogel prepared in Example 1 are shown respectively. It can be seen from the figure that the aerogel has a complete structure, a smooth surface, and no obvious macroscopic defects. Its color is dark green or black block, and the aerogel is very light. The flower can stably support the aerogel with only a slight deformation. It can be seen from the microscopic photo of the aerogel that the molecules inside the aerogel are interconnected to form a three-dimensional network. The skeleton and pores have a bicontinuous structure. The pores of the aerogel are almost the same as its particle size. The continuous skeleton provides structural strength for the aerogel as a whole, and the connected pores give the aerogel the characteristics of light weight, high porosity, and low skeleton density.

[0053] Example 2

[0054] A method for preparing phthalonitrile aerogel comprises the following steps:

[0055] Step 1: mixing phthalonitrile of the structure shown in formula (3) and 1-butyl-3-methylimidazole chloride at a mass ratio of 1:3 at 120° C., stirring for 30 minutes until completely dissolved, to obtain a phthalonitrile solution of the structure shown in formula (3) with a mass fraction of 25%; adding 4,4'-bis(3-aminophenoxy)diphenyl sulfone to the phthalonitrile solution of the structure shown in formula (3), wherein the molar ratio of 4,4'-bis(3-aminophenoxy)diphenyl sulfone to the phthalonitrile of the structure shown in formula (3) is 1:10, and stirring until completely dissolved;

[0056]

[0057] Step 2: After curing at 200°C for 12 hours under closed conditions, continue curing at 250°C for 4 hours to obtain a wet gel; take out the wet gel and place it in anhydrous ethanol solvent for replacement at room temperature for 24 hours. After the wet gel is taken out and dried at room temperature for 24 hours, phthalonitrile aerogel is obtained.

[0058] Example 3

[0059] A method for preparing phthalonitrile aerogel comprises the following steps:

[0060] Step 1: mixing phthalonitrile of the structure shown in formula (3) and 1-ethyl-3-methylimidazolium trifluoromethanesulfonate at a mass ratio of 3:7 at 120° C., stirring for 30 minutes until completely dissolved, to obtain a phthalonitrile solution of the structure shown in formula (3) with a mass fraction of 30%; adding 4,4'-bis(3-aminophenoxy)diphenyl sulfone to the phthalonitrile solution of the structure shown in formula (3), wherein the molar ratio of 4,4'-bis(3-aminophenoxy)diphenyl sulfone to the phthalonitrile resin of the structure shown in formula (3) is 1:10, and stirring until completely dissolved;

[0061]

[0062] Step 2: After curing at 200°C for 12 hours under closed conditions, continue curing at 250°C for 4 hours to obtain a wet gel; take out the wet gel and place it in anhydrous ethanol solvent for replacement at room temperature for 24 hours. After the wet gel is taken out and dried at room temperature for 24 hours, phthalonitrile aerogel is obtained.

[0063] Example 4

[0064] A method for preparing phthalonitrile aerogel comprises the following steps:

[0065] Step 1: mixing phthalonitrile of the structure shown in formula (4) and 1-ethyl-3-methylimidazolium trifluoromethanesulfonate at a mass ratio of 7:13 at 120° C., stirring for 30 minutes until completely dissolved, to obtain a phthalonitrile solution of the structure shown in formula (4) with a mass fraction of 35%; adding 4,4'-bis(3-aminophenoxy)diphenyl sulfone to the phthalonitrile solution of the structure shown in formula (4), wherein the molar ratio of 4,4'-bis(3-aminophenoxy)diphenyl sulfone to the phthalonitrile resin of the structure shown in formula (4) is 1:10, and stirring until completely dissolved;

[0066]

[0067] Step 2: After curing at 200°C for 12 hours under closed conditions, continue curing at 250°C for 4 hours to obtain a wet gel; take out the wet gel and place it in anhydrous ethanol solvent for replacement at room temperature for 24 hours. After the wet gel is taken out and dried at room temperature for 24 hours, phthalonitrile aerogel is obtained.

[0068] Example 5

[0069] A method for preparing phthalonitrile aerogel comprises the following steps:

[0070] Step 1: mixing phthalonitrile (number average molecular weight of about 650) and 1-ethyl-3-methylimidazolium trifluoromethane sulfonate at a mass ratio of 2:3 at 120° C., stirring for 30 minutes until completely dissolved, to obtain a phthalonitrile solution of the structure shown in formula (5) with a mass fraction of 40%; adding 4,4'-bis(3-aminophenoxy)diphenyl sulfone to the phthalonitrile solution of the structure shown in formula (5), wherein the molar ratio of 4,4'-bis(3-aminophenoxy)diphenyl sulfone to the phthalonitrile resin of the structure shown in formula (5) is 1:10, and stirring until completely dissolved;

[0071]

[0072] Step 2: After curing at 200°C for 12 hours under closed conditions, continue curing at 250°C for 4 hours to obtain a wet gel; take out the wet gel and place it in anhydrous ethanol solvent for replacement at room temperature for 24 hours. After the wet gel is taken out and dried at room temperature for 24 hours, phthalonitrile aerogel is obtained.

[0073] Example 6

[0074] A method for preparing phthalonitrile aerogel comprises the following steps:

[0075] Step 1: mixing a phthalonitrile resin (number average molecular weight of about 650) having a structure represented by formula (5) and 1-ethyl-3-methylimidazolium trifluoromethanesulfonate at a mass ratio of 3:7 at 120° C., stirring for 30 minutes until completely dissolved, to obtain a phthalonitrile solution having a mass fraction of 30% of the structure represented by formula (5);

[0076]

[0077]

[0078] Step 2: After curing at 200°C for 12 hours under closed conditions, continue curing at 250°C for 4 hours to obtain a wet gel; take out the wet gel and place it in anhydrous ethanol solvent for replacement at room temperature for 24 hours. After the wet gel is taken out and dried at room temperature for 24 hours, phthalonitrile aerogel is obtained.

[0079] Example 7

[0080] A method for preparing phthalonitrile aerogel comprises the following steps:

[0081] Step 1: mixing phthalonitrile (number average molecular weight of about 650) and 1-butyl-3-methylimidazolium tetrafluoroborate at a mass ratio of 3:7 at 120° C., stirring for 30 minutes until completely dissolved, to obtain a phthalonitrile solution of the structure shown in formula (5) with a mass fraction of 30%; adding 4,4'-bis(3-aminophenoxy)diphenyl sulfone to the phthalonitrile solution of the structure shown in formula (5), the molar ratio of 4,4'-bis(3-aminophenoxy)diphenyl sulfone to the phthalonitrile of the structure shown in formula (5) being 2:10, and stirring until completely dissolved;

[0082]

[0083] Step 2: After curing at 200°C for 12 hours under closed conditions, continue curing at 250°C for 4 hours to obtain a wet gel; take out the wet gel and place it in anhydrous ethanol solvent for replacement at room temperature for 24 hours. After the wet gel is taken out and dried at room temperature for 24 hours, phthalonitrile aerogel is obtained.

[0084] Example 8

[0085] A method for preparing phthalonitrile aerogel comprises the following steps:

[0086] Step 1: mixing phthalonitrile (number average molecular weight of about 650) and 1,3-dimethylimidazolium tetrafluoroborate of the structure shown in formula (5) at a mass ratio of 3:7 at 120° C., stirring for 30 minutes until completely dissolved, to obtain a phthalonitrile solution of the structure shown in formula (5) with a mass fraction of 30%; adding 4,4'-bis(3-aminophenoxy)diphenyl sulfone to the phthalonitrile solution of the structure shown in formula (5), the molar ratio of 4,4'-bis(3-aminophenoxy)diphenyl sulfone to the phthalonitrile of the structure shown in formula (5) being 1:10, and stirring until completely dissolved;

[0087]

[0088] Step 2: After curing at 200°C for 12 hours under closed conditions, continue curing at 250°C for 4 hours to obtain a wet gel; take out the wet gel and place it in anhydrous ethanol solvent for replacement at room temperature for 24 hours. After the wet gel is taken out and dried at room temperature for 24 hours, phthalonitrile aerogel is obtained.

[0089] Example 9

[0090] A method for preparing phthalonitrile aerogel comprises the following steps:

[0091] Step 1: mixing a phthalonitrile resin (number average molecular weight of about 650) having a structure shown in formula (5) and 1-ethyl-3-methylimidazolium trifluoromethanesulfonate at a mass ratio of 3:7 at 120° C., stirring for 30 minutes until completely dissolved, to obtain a phthalonitrile solution having a mass fraction of 30% of the structure shown in formula (5); adding 4,4'-bis(3-aminophenoxy)diphenyl sulfone to the phthalonitrile solution having a structure shown in formula (5), wherein the molar ratio of 4,4'-bis(3-aminophenoxy)diphenyl sulfone to the phthalonitrile resin having a structure shown in formula (5) is 1:10, and stirring until completely dissolved;

[0092]

[0093]

[0094] Step 2: After curing at 200°C for 12 hours under closed conditions, continue curing at 250°C for 4 hours to obtain a wet gel; take out the wet gel and place it in anhydrous ethanol solvent for replacement at room temperature for 24 hours. After the wet gel is taken out and dried at room temperature for 24 hours, phthalonitrile aerogel is obtained.

[0095] The phthalonitrile aerogels prepared in Examples 1-9 were subjected to physical characterization and performance tests, respectively, and the results are shown in Table 1.

[0096] in:

[0097] Density test method: drainage method;

[0098] Porosity test method: BET test;

[0099] Shrinkage test method: GB / T 13951-2014;

[0100] Thermal decomposition temperature test method: reference standard GB / T 19267.12-2008;

[0101] Compression strength and elastic modulus test method: refer to standard GB / T 2567-2008.

[0102] Table 1 Properties of phthalonitrile aerogel

[0103]

[0104] As can be seen from the results in Table 1, the polymer network density increases (solid content high means that more polymer molecules or monomers are present in the unit volume), which will cause the polymer network formed to be tighter. Simultaneously, along with the increase of the polymer network density, because there are more solid materials to occupy the potential pore space, the pore structure formed may become smaller. Thereby finally affecting the physical properties (comprising its porosity, pore size and density) of the phthalonitrile aerogel. Among the present invention, the phthalonitrile monomer is cross-linked, further enhancing the cross-linking skeleton strength, effectively alleviating the shrinkage, collapse and cracking problems caused by the wet gel in the normal pressure drying process, ensuring that the shrinkage of the aerogel obtained is below 5%. The phthalonitrile aerogel prepared by embodiments of the present invention 1-9 has excellent mechanical properties. The phthalonitrile aerogel prepared by cross-linking the phthalonitrile monomer in a high temperature environment has a high thermal decomposition temperature and a very high residual carbon rate, so a thermal carbonization layer is generated during pyrolysis, accompanied by the release of gas. The aerogel of the present invention can be used as a matrix of an excellent anti-ablation composite material, and mass ejection is generated by injecting pyrolysis gas into the boundary layer in a high temperature environment, thereby playing an anti-ablation and heat insulation role.

[0105] The above is an explanation of the embodiments of the present invention. However, the present invention is not limited to the above embodiments. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing phthalonitrile aerogel, characterized in that: The steps include: (1) mixing phthalonitrile monomer and ionic liquid to obtain a first mixed solution; (2) adding a curing agent to the first mixed solution to obtain a second mixed solution; (3) solidifying the second mixed liquid to obtain a wet gel; (4) The wet gel is taken out and placed in a low-boiling point solvent for solvent replacement, and after drying, phthalonitrile aerogel is obtained.

2. The preparation method according to claim 1, characterized in that The phthalonitrile monomer is selected from compounds having a structure as shown in formula (1) or formula (2): Wherein, R is selected from any one of the following structures: Wherein, R1, R2, and R3 are the same or different, and are independently selected from -H, -CH3, -CH2CH3, -CH(CH3)2, -OH, -F, -CF3, etc.; n is selected from an integer of 0-20.

3. The preparation method according to claim 1 or 2, characterized in that: The phthalonitrile monomer is selected from the compounds represented by formula (3), formula (4) or formula (5): Wherein, n is selected from an integer of 0-20, preferably an integer of 0-10.

4. The preparation method according to any one of claims 1 to 3, characterized in that: The ionic liquid is one or a mixture of 1-butyl-3-methylimidazolium tetrafluoroborate, 1-butyl-3-methylimidazolium chloride, 1-ethyl-3-methylimidazolium trifluoromethanesulfonate and 1,3-dimethylimidazolium tetrafluoroborate; Preferably, the curing agent is selected from zinc chloride, cupric chloride, 4,4'-diaminodiphenyl sulfone and 4,4'-bis(3-aminophenoxy)diphenyl sulfone, or a mixture of several thereof.

5. The preparation method according to any one of claims 1 to 4, characterized in that: The mass ratio of the phthalonitrile monomer to the ionic liquid is (15-70):

100.

6. The preparation method according to any one of claims 1 to 5, characterized in that: The molar ratio of the phthalonitrile monomer to the curing agent is 10:(0.1-2).

7. The preparation method according to any one of claims 1 to 6, characterized in that: The curing adopts a gradient temperature increase method; For example, the gradient heating process includes a first stage heating and a second stage heating. Preferably, the first stage heating to a curing temperature of 150-250°C, the first stage curing time is 1-24 hours; the second stage heating to a curing temperature of 250-325°C, the second stage curing time is 1-10 hours; Preferably, the low boiling point solvent is one or more of anhydrous ethanol, ethylene glycol, n-butanol and n-heptane.

8. A phthalonitrile aerogel prepared by the method for preparing a phthalonitrile aerogel according to any one of claims 1 to 7.

9. Use of the phthalonitrile aerogel according to claim 8 in the fields of thermal insulation, sound insulation, aerospace or biomedicine.

10. A thermal insulation material, comprising the phthalonitrile aerogel according to claim 8 or prepared from the phthalonitrile aerogel according to claim 8.

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