CN116003097A - Polyimide-based composite carbon aerogel and preparation method and application thereof - Google Patents
Polyimide-based composite carbon aerogel and preparation method and application thereof Download PDFInfo
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Abstract
The invention provides polyimide-based composite carbon aerogel, which is formed by compounding polyimide-based carbon aerogel and carbon nano filler; the polyimide-based carbon aerogel is formed by carbonizing polyimide aerogel, and the carbon nano filler is a multi-wall carbon nano tube, an amino multi-wall carbon nano tube or a carbon nano fiber. According to the invention, the carbon nano filler is introduced into the polyimide carbon aerogel, so that the carbonization shrinkage, density and heat conductivity of the polyimide-based carbon aerogel are reduced, and the polyimide-based carbon aerogel has a wide application prospect in important fields such as aerospace, weaponry and the like as a lightweight heat insulation protective material.
Description
Technical Field
The invention belongs to the field of high polymer materials, and particularly relates to polyimide-based composite carbon aerogel and a preparation method and application thereof.
Background
With the continuous development of aerospace technology, the service environment of an aerospace vehicle is more severe, and when the structure of the aerospace vehicle faces severe pneumatic heating, effective heat protection needs to be provided for the aerospace vehicle, so that the flight safety of the aerospace vehicle in an extreme environment is ensured. The use of low thermal conductivity insulating materials prevents heat transfer to the interior of the aircraft, and avoiding internal structure damage is a key means to achieve effective thermal protection.
Aerogel is a material having a three-dimensional network skeleton formed by the mutual polymerization of nano-sized particles or polymer monomers, and has the remarkable advantages of low density, high surface area and porosity, low thermal conductivity, light weight and high efficiency, compared with other heat insulation materials, and has been receiving more and more attention in recent years.
Polyimide (PI) aerogel is an organic aerogel with excellent high temperature resistance and mechanical property, which is prepared by polymerizing diamine and dianhydride to generate polyamide acid (PAA) precursor, and performing gel, aging, drying and imidization treatment. However, the PI aerogel has the problem of larger system shrinkage rate in the preparation process, and the density of the aerogel is increased and the thermal conductivity is increased due to the larger shrinkage rate. In recent years, research shows that the introduction of one-dimensional nano materials such as carbon nano tubes and two-dimensional nano materials such as graphene and transition metal carbonitride (MXene) can inhibit the contraction of PI aerogel and improve the heat insulation performance of PI aerogel (Zhang Ling, wang Xue, li Gujiang, and the like.) the synthesis and performance [ J ] of carbon nano fiber reinforced polyimide composite aerogel is achieved by material engineering 2022,50 (1): 125-131.DOI:10.11868/J. Issn.1001-4381.2021.000166.
The carbon aerogel is an important branch of aerogel, and is a novel nano porous carbon material obtained by taking organic aerogel as a precursor and performing high-temperature pyrolysis in an inert gas atmosphere. The carbon aerogel has the characteristics of high specific surface area, low density, low thermal conductivity and the like given by the extremely high porosity of the aerogel, and also has the characteristics of heat resistance, acid and alkali resistance, high conductivity and the like of the carbon material, so that the application of the aerogel in heat insulation protective materials is further widened, and the carbon aerogel has wide application in the fields of catalysis, energy storage, absorbents and the like.
However, on the one hand, most of the prior carbon aerogels are prepared from phenolic prepolymers as main precursor raw materials, for example, linear phenolic oligomers catalyzed by acids by acid-base two-step catalysis methods, such as Zhang, through base-catalyzed cross-linking polymerization, and further prepared into carbon aerogels having a thermal conductivity of 0.809W/(m·k) under an argon atmosphere at 2000 ℃ and 0.1MPa (Zhang Z, zhao S, chen G, et al, influence of acid-base catalysis on the textural and thermal properties of carbon aerogel monoliths [ J ] Microporous and Mesoporous Materials,2020, 296:109997.). Its insulation properties are still to be further improved. However, polyimide-based carbon aerogel prepared by carbonization is still reported recently based on polyimide aerogel.
On the other hand, in addition to shrinkage of the polyimide aerogel itself during the preparation process, the polyimide aerogel also shrinks during carbonization, so that the density is increased, and the thermal conductivity is affected. The influence of the filler such as the carbon nano material on the carbonization performance of the polyimide aerogel and the influence of the filler on the density and the heat insulation performance of the carbon aerogel are still to be further explored.
Disclosure of Invention
The invention aims to provide polyimide-based composite carbon aerogel, and a preparation method and application thereof.
The invention provides a composite carbon aerogel, which is formed by compounding polyimide-based carbon aerogel and carbon nano filler.
Further, the polyimide-based carbon aerogel is formed by carbonizing polyimide aerogel; the polyimide aerogel is obtained by freeze drying gel obtained by cross-linking, solidifying and imidizing a polyamic acid solution;
the mass of the carbon nano filler is 2% -20% of the mass of the polyamide acid; preferably 10%;
preferably, the carbon nanofiller is a multi-walled carbon nanotube, an aminated multi-walled carbon nanotube or a carbon nanofiber; more preferably aminated multiwall carbon nanotubes.
Further, the solid content of the polyamic acid solution is 3 to 5 weight percent, and the polymerization degree of the polyamic acid is 20 to 40; preferably, the polyamic acid solution has a solid content of 3wt% and the polyamic acid has a degree of polymerization of 40.
Further, the crosslinking curing is a reaction with a crosslinking agent, which is a polyamine; preferably a triamine, more preferably 1,3, 5-tris (4-aminophenoxy) benzene.
Still further, the above-mentioned polyamic acid is an acid anhydride-terminated polyamic acid, and the acid anhydride group of the polyamic acid and the amino group of the crosslinking agent are in equimolar ratio.
Further, the acid anhydride end-capped polyamide acid is polymerized by diamine and dicarboxylic anhydride, wherein the molar ratio of the diamine to the dicarboxylic anhydride is n (n+1), and n is the polymerization degree of the polyamide acid;
preferably, the diamine is 4,4' -diamino-2, 2' -dimethyl-1, 1' -biphenyl and the dianhydride is biphenyl tetracarboxylic dianhydride.
Further, the imidization is carried out under the action of a dehydrating agent and a catalyst; preferably, the dehydrating agent is acetic anhydride and the catalyst is pyridine;
preferably, the molar ratio of the dehydrating agent to the dibasic acid anhydride is (6-10): 1, preferably 8:1; the dehydrating agent and the catalyst are in equimolar ratio.
Further, the solvent of the polyamic acid solution is an organic solvent, preferably DMAc.
The invention also provides a preparation method of the composite carbon aerogel, which comprises the following steps: carbonizing polyimide aerogel for 1-3 hours at 800-900 ℃ in inert atmosphere;
preferably, the polyimide aerogel is prepared according to the following steps:
(1) Adding the carbon nano filler into the polyamic acid solution, uniformly mixing, adding the cross-linking agent, and performing cross-linking curing reaction at room temperature for 30-50 min;
(2) Adding a dehydrating agent and a catalyst, imidizing at room temperature for 3-10 min, and standing to obtain gel;
(3) Aging the gel for 20-30 h at room temperature, sequentially replacing the gel with a tertiary butanol solution and tertiary butanol with volume fractions of 25%, 50% and 75%, and then freeze-drying to obtain the gel; the solvent of the tertiary butanol solution is the solvent of the polyamic acid solution.
The invention also provides application of the composite carbon aerogel in heat insulation protective materials.
The invention has the beneficial effects that: the polyimide aerogel is creatively adopted as a precursor of the carbon aerogel, the carbon nano filler is introduced, and the polyimide-based composite carbon aerogel prepared by carbonization has low carbonization shrinkage, low density and low thermal conductivity, is used as a lightweight heat insulation protective material, and has wide application prospect in important fields such as aerospace, weaponry and the like.
The "polymerization degree of polyamic acid" of the present invention is the theoretical polymerization degree of polyamic acid. Namely, the diamine and dianhydride molar ratio of the synthesized polyamide acid is converted to obtain the following components: (n+1)/n=n Dibasic anhydride /n A diamine, a diamine compound, and a diamine compound, where N refers to the degree of polymerization and N represents the amount of material.
The solid content of the polyamic acid solution is the mass fraction of the polyamic acid in the polyamic acid solution.
The term "room temperature" in the present invention means a temperature range of 20 to 30 ℃.
The term "DMAc" as used herein refers to N, N-dimethylacetamide.
The "inert atmosphere" in the present invention refers to the inert gas protection environment conditions such as nitrogen, argon, etc.
It should be apparent that, in light of the foregoing, various modifications, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims.
The above-described aspects of the present invention will be described in further detail below with reference to specific embodiments in the form of examples. It should not be understood that the scope of the above subject matter of the present invention is limited to the following examples only. All techniques implemented based on the above description of the invention are within the scope of the invention.
Drawings
Fig. 1 is a scanning electron micrograph of a polyimide-based carbon aerogel (comparative example 1).
FIG. 2 is a scanning electron micrograph of a polyimide-based composite carbon aerogel of the present invention (example 2).
Detailed Description
The raw materials and equipment used in the invention are all known products and are obtained by purchasing commercial products.
EXAMPLE 1 preparation of polyimide-based composite carbon aerogel according to the invention
1. Preparation of nanofiller dispersion: dissolving 0.31g of a carbon nanotube dispersing agent TNNDIS (the mass ratio of the TNNDIS to the filler is 0.6:1) in 120mL of DMAc solvent, then adding 0.51g of multi-wall carbon nanotubes (MWCNTs), stirring to completely infiltrate the mixture into the solvent, and ultrasonically dispersing the dispersion liquid by using a cell crusher for 60min to obtain DMAc dispersion liquid of the MWCNTs.
2. Preparation of polyamic acid (PAA): first, 4' -diamino-2, 2' -dimethyl-1, 1' -biphenyl (DMBZ) (2.1229 g,10.0 mmol) was added to 40mL of N, N-dimethylacetamide (DMAc) and stirred for 20min under nitrogen as a protective gas to allow the diamine to be sufficiently dissolved. Then, biphenyl tetracarboxylic dianhydride (BPDA) (3.0158 g,10.25 mmol) and 9ml ldmac were added and reacted at room temperature for 3 hours to obtain a polyamic acid (PAA) solution, the PAA polymerization degree n=40.
3. Preparation of Polyimide (PI) composite aerogel: and mixing the DMAc dispersion liquid of the MWCNTs with the PAA solution, and mechanically stirring for 30min to uniformly disperse the mixture, thereby obtaining the PAA/MWCNTs dispersion liquid with the solid content of 3wt% and the relative PAA content of 10 phr.
8mL of DMAc solution containing 1,3, 5-tris (4-aminophenoxy) benzene (TAB) (0.0799 g,0.2 mmol) as a crosslinking agent was taken and added to the PAA solution to react for 40min at room temperature, acetic anhydride (7.75 mL,82 mmol) and pyridine (6.61 mL,82 mmol) were added to continue the reaction for 4min, and after pouring the solution into a 100mL small beaker, standing, and aging at room temperature for 24h after the solution formed a gel. The wet gel was then removed and placed in a t-butanol solution containing 75% dmac at a volume ratio of solution to wet gel of 4:1 and solvent displacement was performed in a 40 ℃ water bath for 24h. Subsequently, the reaction mixture was replaced in a tert-butanol solution having a DMAc content of 50% and 25% for 24 hours, respectively, and finally replaced 5 times in a pure tert-butanol solution. And after the replacement is finished, the wet gel is placed in a freeze dryer for freeze-drying for 48 hours, and the polyimide composite aerogel is obtained.
4. Preparation of composite carbon aerogel: and (3) polishing the sample regularly, then placing the sample in a tube furnace, heating to 800 ℃ at a heating rate of 5 ℃/min under flowing inert atmosphere, preserving heat for 1h, naturally cooling to room temperature, and then opening the furnace to take out the sample, thereby obtaining the polyimide-based carbon aerogel with the filler of the multiwall carbon nanotube.
EXAMPLE 2 preparation of polyimide-based composite carbon aerogel according to the invention
Referring to the preparation method of example 1, only the multi-walled carbon nanotubes therein were replaced with aminated multi-walled carbon nanotubes (MWCNTs-NH) 2 ) And in the step 3, the mechanical stirring time for mixing with the PAA solution is prolonged to 2 hours, and the rest conditions are unchanged, so that the polyimide-based carbon aerogel with the filler of the amino multi-wall carbon nano tube is prepared.
EXAMPLE 3 preparation of polyimide-based composite carbon aerogel according to the invention
Referring to the preparation method of example 1, only the multi-wall carbon nanotubes therein were replaced with Carbon Nanofibers (CNFs), and the remaining conditions were unchanged, to prepare polyimide-based carbon aerogel with carbon nanofibers as the filler.
Comparative example 1 preparation of polyimide-based carbon aerogel
Referring to the preparation method of example 1, the polyimide-based carbon aerogel was prepared without adding a filler and the remaining conditions were unchanged.
The following experiments prove the beneficial effects of the invention.
Experimental example 1 polyimide matrix screening of composite carbon aerogel of the present invention
1. Experimental method
Referring to the preparation method of comparative example 1, a series of PAA solutions with different polymerization degrees and solid contents were prepared, and specific parameters are shown in Table 1. A series of pure polyimide-based carbon aerogels (correspondingly designated as carbon aerogels 1 to 5, wherein carbon aerogel 3 is the carbon aerogel of comparative example 1 of the present invention) were prepared accordingly. The parameters in the preparation process meet the following conditions: the diamine and dianhydride are present in a molar ratio of n+1, where n represents the number of repeat units of the anhydride-terminated PAA oligomer. Since the anhydride-terminated PAA oligomer contains two reactive anhydride groups and each TAB molecule contains three amine groups that can be reacted with it, the molar ratio of TAB to PAA oligomer is 2:3. The molar ratio of acetic anhydride to BPDA was 8:1 and the molar ratio of pyridine to acetic anhydride was 1:1.
Table 1 parameter table of polyimide aerogel precursor
The properties of the series of pure polyimide-based carbon aerogels were then characterized by reference to the characterization methods of experimental examples 2 and 3, respectively.
2. Experimental results
The effect of polymerization degree and solid content on carbonization shrinkage, density and thermal conductivity of polyimide-based carbon aerogel is shown in table 2. It can be seen that the carbon aerogel of comparative example 1 of the present invention has the lowest carbonization shrinkage, the lowest density and the lowest thermal conductivity; and it was tested for compression properties (test specimens were processed to 10X 10mm according to standard JB/T8133.8-1999 using an electronic Universal Material tester) 3 The test speed was 1mm/min. The maximum compressive stress on the stress-strain curve was used as the compressive strength of the sample, and the compressive modulus was calculated from the slope of the stress-strain line at the elastic deformation stage), and good mechanical properties (compressive modulus 102.73MPa, compressive strength 4.51 MPa) were also reflected.
Thus, the present invention selects the preparation of polyimide matrix with a precursor solution having a degree of polymerization of 40 and a solid content of 3wt% and further compounding with filler.
TABLE 2 Properties of polyimide-based carbon aerogel
Experimental example 2, microstructure of polyimide-based composite carbon aerogel according to the invention
1. Experimental method
Taking the polyimide-based carbon aerogel prepared in the comparative example 1 and the polyimide composite carbon aerogel prepared in the example 2, and observing the microscopic morphology and the pore structure of the polyimide-based carbon aerogel by using a scanning electron microscope.
2. Experimental results
SEM pictures of the carbon aerogel are shown in fig. 1 and 2, and comparison shows that the two pore structures have no obvious difference, and are all coral-shaped 3D porous structures. The pore wall shape of the composite aerogel (fig. 2) added with the carbon nanotubes becomes relatively irregular, and the carbon aerogel skeleton becomes thin, compared with the smooth pore wall of the pure carbon aerogel (fig. 1). Further examination of FIG. 2 shows that a large number of carbon nanotubes are exposed on the surface of the carbon aerogel framework, which is related to the high aspect ratio characteristics of the carbon aerogel framework itself.
Experimental example 3 polyimide-based composite carbon aerogel of the present invention physical Properties
1. Experimental method
The diameter and height of the beaker mold and the cylindrical sample were measured using a vernier caliper, and the mass of the sample was measured using an analytical balance. Shrinkage of the aerogel during the gel phase was obtained by dividing the difference between the beaker diameter and the diameter of the sample after gel by the beaker diameter. Shrinkage in the carbonization stage was obtained by dividing the difference in diameter of the sample before and after carbonization by the diameter of the sample before carbonization. The density of the carbon aerogel is obtained by dividing the mass of the sample by the volume. The calculation results are shown in Table 3.
2. Experimental results
Shrinkage and density data before and after carbonization for aerogel samples with different types of fillers added at each stage are shown in table 3.The shrinkage of the composite carbon aerogel mainly occurs in the gel and carbonization stages, and the three fillers can inhibit the shrinkage of the PI aerogel in the gel stage, wherein MWCNTs-NH is added 2 The inhibition effect of (2) is most obvious. In the carbonization stage, the addition of the three fillers still plays a role in reinforcing the matrix skeleton, the carbonization shrinkage and the density of the composite carbon aerogel are greatly reduced compared with the pure carbon aerogel, and when 10phr of MWCNTs-NH is added 2 When the density of the composite carbon aerogel is as low as 0.154 g.cm -3 About a 40% drop compared to pure carbon aerogel.
TABLE 3 physical Properties of polyimide-based composite carbon aerogel according to the invention
In general, the carbon aerogel of the composite carbon nanomaterial of the present invention has low carbonization shrinkage and low density, is superior to pure carbon aerogel, and wherein the filler MWCNTs-NH 2 Most preferably.
Experimental example 4 thermal conductivity of polyimide-based composite carbon aerogel of the present invention
1. Experimental method
The carbon aerogels prepared in examples 1 to 3 and comparative example 1 were taken and the thermal conductivity of the samples was measured using HOT DISK thermal conductivity meter (TPS 2500, sweden), i.e. transient planar thermal source method.
2. Experimental results
As can be seen from table 4, the introduction of the filler shows a significant effect of reducing the thermal conductivity compared to the pure carbon aerogel of comparative example 1, since the addition of the filler effectively reduces the carbonization shrinkage and density of the carbon aerogel, thereby reducing the solid thermal conductivity of the material.
TABLE 4 thermal conductivity of polyimide-based composite carbon aerogels of the present invention
In general, the present invention is complexThe thermal conductivity of the carbon-containing aerogel is not more than 0.1 W.m -1 ·k -1 At least 0.084 W.m -1 ·k -1 The method comprises the steps of carrying out a first treatment on the surface of the Has the potential of being used as a heat insulation protective material.
In summary, the polyimide-based composite carbon aerogel provided by the invention has low carbonization shrinkage, low density and low thermal conductivity, is used as a lightweight heat insulation protective material, and has wide application prospects in important fields such as aerospace, weaponry and the like.
Claims (10)
1. A composite carbon aerogel is characterized by being formed by compounding polyimide-based carbon aerogel and carbon nano-filler.
2. The composite carbon aerogel of claim 1, wherein the polyimide-based carbon aerogel is carbonized from a polyimide aerogel; the polyimide aerogel is obtained by freeze drying gel obtained by cross-linking, solidifying and imidizing a polyamic acid solution;
the mass of the carbon nano filler is 2% -20% of the mass of the polyamide acid; preferably 10%;
preferably, the carbon nanofiller is a multi-walled carbon nanotube, an aminated multi-walled carbon nanotube or a carbon nanofiber; more preferably aminated multiwall carbon nanotubes.
3. The composite carbon aerogel of claim 2, wherein the polyamic acid solution has a solid content of 3 to 5wt%, and the polyamic acid has a polymerization degree of 20 to 40; preferably, the polyamic acid solution has a solid content of 3wt% and the polyamic acid has a degree of polymerization of 40.
4. A carbon aerogel according to claim 2 or 3, wherein the cross-linking curing is by reaction with a cross-linking agent which is a polyamine; preferably a triamine, more preferably 1,3, 5-tris (4-aminophenoxy) benzene.
5. The composite carbon aerogel of claim 4, wherein the polyamic acid is an anhydride-terminated polyamic acid, and wherein the acid anhydride groups of the polyamic acid and the amino groups of the crosslinker are in equimolar ratio.
6. The composite carbon aerogel of claim 5, wherein the acid anhydride terminated polyamic acid is polymerized from diamine and dicarboxylic anhydride, the molar ratio of diamine to dicarboxylic anhydride is n (n+1), wherein n is the degree of polymerization of the polyamic acid;
preferably, the diamine is 4,4' -diamino-2, 2' -dimethyl-1, 1' -biphenyl and the dianhydride is biphenyl tetracarboxylic dianhydride.
7. The composite carbon aerogel of claim 6, wherein the imidization is a reaction under the action of a dehydrating agent and a catalyst; preferably, the dehydrating agent is acetic anhydride and the catalyst is pyridine;
preferably, the molar ratio of the dehydrating agent to the dibasic acid anhydride is (6-10): 1, preferably 8:1; the dehydrating agent and the catalyst are in equimolar ratio.
8. The composite carbon aerogel of claim 2, wherein the solvent of the amic acid solution is an organic solvent, preferably DMAc.
9. The method for preparing a composite carbon aerogel according to any one of claims 1 to 8, comprising the steps of: carbonizing polyimide aerogel for 1-3 hours at 800-900 ℃ in inert atmosphere;
preferably, the polyimide aerogel is prepared according to the following steps:
(1) Adding the carbon nano filler into the polyamic acid solution, uniformly mixing, adding the cross-linking agent, and performing cross-linking curing reaction at room temperature for 30-50 min;
(2) Adding a dehydrating agent and a catalyst, imidizing at room temperature for 3-10 min, and standing to obtain gel;
(3) Aging the gel for 20-30 h at room temperature, sequentially replacing the gel with a tertiary butanol solution and tertiary butanol with volume fractions of 25%, 50% and 75%, and then freeze-drying to obtain the gel; the solvent of the tertiary butanol solution is the solvent of the polyamic acid solution.
10. Use of the composite carbon aerogel of any of claims 1-8 in a thermal insulation protective material.
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Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20040132845A1 (en) * | 2002-07-22 | 2004-07-08 | Aspen Aerogels, Inc. | Polyimide aerogels, carbon aerogels, and metal carbide aerogels and methods of making same |
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Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20040132845A1 (en) * | 2002-07-22 | 2004-07-08 | Aspen Aerogels, Inc. | Polyimide aerogels, carbon aerogels, and metal carbide aerogels and methods of making same |
Non-Patent Citations (2)
| Title |
|---|
| BIN ZHANG ET.AL: "Morphology and properties of polyimide/multi-walled carbon nanotubes composite aerogels", HIGH PERFORMANCE POLYMERS, vol. 30, no. 3, 30 April 2018 (2018-04-30), pages 292 - 302 * |
| 刘婷等: "聚酰亚胺气凝胶材料的制备及其应用", 《工程科学学报》, vol. 42, no. 1, 31 January 2020 (2020-01-31), pages 39 - 47 * |
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