Polyimide composite aerogel with light heating and electric heating functions and application thereof

Abstract

The invention belongs to the technical field of high polymer materials, and particularly relates to polyimide composite aerogel with light heating and electric heating functions and application of the polyimide composite aerogel. The preparation method comprises the following steps: adding 5-norbornene-2, 3-dicarboxylic anhydride, 3, 3 ', 4, 4'-benzophenonetetracarboxylic dianhydride, pyromellitic dianhydride, 4, 4 ', 4'-tetracarboxylic dianhydride, 2, 3 ', 4, 4'-tetracarboxylic dianhydride, 4, 4 The preparation method comprises the following steps: reacting one or more of 3, 3 ', 4, 4'-diphenyl ether dianhydride or 3, 3 ', 4, 4'-biphenyl tetracid dianhydride with 3, 5-diaminobenzoic acid in N, N-dimethylacetamide to form an anhydride-terminated polyamide acid solution, adding triethylamine to regulate the reaction, precipitating PAA salt through acetone, washing, filtering, drying, then preparing a polyamide aqueous solution from the PAA salt and a multi-walled carbon nanotube, and finally preparing the multi-walled carbon nanotube / polyamide aqueous solution. The end-capped cross-linked polyimide composite aerogel is obtained through freeze drying and thermal imidization, and the prepared polyimide composite aerogel has low density and high mechanical property and compression performance and has wide application prospects in the field of photoelectric heating.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer materials, and in particular relates to a polyimide composite aerogel with optical heating and electrical heating functions and application thereof. Background Art

[0002] In recent years, with the development of science and technology and the advancement of technology, single-function aerogel materials can no longer meet the needs of specific environmental applications. Therefore, the development of multifunctional aerogel materials has broad prospects.

[0003] Organic aerogels such as polyvinyl alcohol aerogel and cellulose aerogel have been widely used in exterior wall insulation, oil-water separation, energy collection, etc. due to their ultra-low density, high porosity, and outstanding thermal insulation. In extreme environments, most organic aerogels have poor performance. Polyimide aerogels retain the excellent thermal stability and good mechanical properties of polyimide.

[0004] Currently, most of the polyimide aerogels reported are used in the fields of aerospace, strain sensing, microwave absorption or seawater desalination. The applications focus on the single function of polyimide composite aerogels, while there are few reports on the application of polyimide composite aerogels in the field of photoelectric conversion to heat. Summary of the invention

[0005] The invention provides a polyimide composite aerogel with optical heating and electric heating functions. The composite aerogel is prepared by reacting one or more of 5-norbornene-2,3-dicarboxylic anhydride, 3,3',4,4'-dibenzophenone tetracarboxylic anhydride, pyromellitic anhydride, 4,4'-biphenyl ether anhydride or 3,3',4,4'-biphenyl tetracarboxylic anhydride with 3,5-diaminobenzoic acid in N,N-dimethylacetamide to form an anhydride-terminated polyamic acid solution, adding triethylamine to adjust the reaction, precipitating polyamic acid salt with acetone, and then configuring the polyamic acid solution with multi-walled carbon nanotubes to form a polyamide aqueous solution, and freeze-drying and thermal imidization to obtain the end-capped cross-linked polyimide composite aerogel.

[0006] Taking 3,3',4,4'-benzophenone tetracarboxylic dianhydride as an example, the preparation method of polyamic acid salt is as follows: add dehydrated DMAc to a three-necked flask, add 3,5-diaminobenzoic acid (DABA), and stir until it is completely dissolved. Add dianhydride monomer 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BTDA) in small amounts and multiple times (5 times) to ensure that the molecular chain end is amino-terminated, observe the viscosity, and after 8 hours of reaction, add the end-capping agent 5-norbornene-2,,3-dicarboxylic anhydride (NA), reduce the speed, and add 4ml of triethylamine (TEA) to continue the reaction for 3 hours. Collect the anhydride-terminated product polyamic acid PAA solution. Nitrogen replacement is performed three times after each addition to exclude air in the reaction device. The above product is poured into acetone with vigorous stirring (speed 200) at a constant speed to precipitate filamentous PAA salt. After stirring overnight, it is filtered, dried to a constant temperature, and crushed to obtain the target product.

[0007] Among them, triethylamine mainly plays the role of catalyst: promoting the formation of polymer and adjusting the molecular weight, molecular weight distribution and properties of polyamic acid. The amount of triethylamine added is 3-4 times the molar amount of (-COOH). Vigorous magnetic stirring is required when pouring acetone.

[0008] The molar ratio of 3,5-diaminobenzoic acid, 3,3',4,4'-benzophenonetetracarboxylic dianhydride and 5-norbornene-2,3-dicarboxylic anhydride is 11:10:10.

[0009] The preparation method of PAA composite aerogel is as follows: weigh the prepared PAA salt and dissolve it in a triethylamine aqueous solution, then add the conductive filler multi-walled carbon nanotubes into the solution, and freeze-dry it to obtain the PAA composite aerogel; put the obtained PAA composite aerogel into a high-temperature oven for thermal imidization reaction to obtain a polyimide composite aerogel.

[0010] The composition of the triethylamine aqueous solution in terms of mass volume ratio is: triethylamine: deionized water = 1:19.

[0011] The amount of PAA salt added is 3-9wt% of the mass of the triethylamine aqueous solution. When the amount of PAA salt is reduced, the aerogel is not formed. Although the increase in the amount of PAA salt will make the structure of the aerogel denser, it will reduce the pore structure and cannot be called the defined "aerogel".

[0012] The added amount of the multi-walled carbon nanotubes is 1-3 wt % of the mass of the triethylamine aqueous solution.

[0013] Freeze-drying conditions are: -80°C ≤ temperature ≤ -50°C, pressure ≤ 1Pa, freezing for 24 hours, and vacuum drying for 48 hours.

[0014] The process of thermal imidization in a high temperature oven is as follows: 100°C, 2 hours to remove moisture, and 200°C and 300°C for one hour each to complete the imidization.

[0015]

[0016] The polyimide composite aerogel of the invention is used in the field of photoelectric heating.

[0017] Beneficial effects:

[0018] The present invention uses diamine and dianhydride monomers to prepare a water-soluble polyamic acid precursor, and then uses anhydride to end-cap and cross-link. When the aerogel is thermally imidized, the polyimide molecular chains are cross-linked to form a three-dimensional network structure, thereby improving the mechanical properties of the aerogel. Carbon nanotubes are added during the preparation of the aerogel to give the aerogel conductivity. At the same time, the aerogel has the ability to be heated by light due to the optical absorption of the carbon nanotubes. In addition, the addition of carbon nanotubes enhances the skeleton structure of the aerogel. Under light of different intensities, the temperature of the aerogel can be raised to 133°C, and it has excellent light-to-heat conversion capabilities. It can be used for deicing and melting, as well as rapid heating in harsh environments, and has broad application prospects in the fields of light and electric heating.

[0019] In addition, the conductive composite aerogel prepared by the present invention has a low density and a black conductive network formed by multi-walled carbon nanotubes inside the material, which can realize the conversion of light energy and electrical energy into thermal energy under the irradiation of ultraviolet lamp simulating sunlight and an external voltage. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 These are the TGA and DTG spectra of the polyimide composite aerogel synthesized in Example 1.

[0021] Figure 2 This is the infrared spectrum of the polyimide composite aerogel synthesized in Example 1.

[0022] Figure 3 The temperature variation curve of the polyimide composite aerogel prepared in Example 1 under different voltages.

[0023] Figure 4 This is the temperature variation curve of the polyimide composite aerogel prepared in Example 1 under different light intensities. DETAILED DESCRIPTION

[0024] In order to explain the present invention more clearly, the present invention is further described below in conjunction with embodiments. It should be understood by those skilled in the art that the content specifically described below is illustrative rather than restrictive, and should not be used to limit the scope of protection of the present invention.

[0025] Unless otherwise specified, the experimental methods used in the following examples are all conventional methods. The experimental materials, reagents, etc. used in the following experimental examples can be obtained through commercial channels or known experimental methods.

[0026] Example 1

[0027] (1) Solvent removal

[0028] Pour 55 ml of DMAc into a 100 ml single-necked flask, add a magnetic bar and 0.5 g of CaH2, seal the flask with a balloon, stir magnetically at room temperature for 24 hours to allow for sufficient reaction, then perform vacuum distillation to separate the front and back fractions, collect the rest and seal them. Yield: 85%.

[0029] (2) Preparation of polyamide salt

[0030] Add 45 ml of dehydrated DMAc and 3,5-diaminobenzoic acid (DABA) (1.6736 g, 11 mmol) to a three-necked flask and stir until it is completely dissolved. Add the dianhydride monomer 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BTDA) (3.2223 g, 10 mmol) in small amounts and multiple times (5 times) to ensure that the molecular chain ends are amino-terminated. Observe the viscosity until it slowly drips along the wall of the flask. After 8 hours of reaction, add the end-capping agent 5-norbornene-2,3-dicarboxylic anhydride (NA) (1.6416 g, 10 mmol), reduce the speed, and add 4 ml of triethylamine (TEA) to continue the reaction for 3 hours. Collect the anhydride-terminated product polyamic acid solution.

[0031] The above product was poured into acetone with vigorous stirring (speed 200) at a constant speed to precipitate filamentous PAA salt. After stirring overnight, the target product was obtained by filtering, drying to a constant temperature, and crushing.

[0032] (3) Preparation of polyamic acid composite aerogel

[0033] After preparing triethylamine aqueous solution (1.5 g TEA, 28.5 g deionized water) in a mass volume ratio of triethylamine: deionized water of 1:19, 1.5 g PAA salt was added, and magnetic stirring was performed until completely dissolved. Then, 0.6 g multi-walled carbon nanotubes were added, and after ultrasonic treatment for 30 min, the mixture was poured into a mold, frozen for 24 h (-70°C), and vacuum dried for 48 h to obtain polyamic acid composite aerogel (PAA-Aerogel).

[0034] (4) Preparation of polyimide composite aerogel

[0035] The composite aerogel obtained above was placed in a high-temperature oven at 100° C. for 2 h to dry out moisture, and imidization was completed at 200° C. and 300° C. for one hour respectively, thereby obtaining a polyimide composite aerogel (PI-Aerogel).

[0036] The infrared data of the polyimide provided by the present invention are as follows: Figure 2 As shown:

[0037] FTIR(KBr,ν,cm -1 ): 3446, 1782, 1610, 1370, 1261, 1104, 823, 726.

[0038] Figure 1 It is the TGA and DTG curve of polyimide aerogel. It can be seen from the figure that the synthesized polyimide aerogel has good thermal stability, the initial decomposition temperature is 300°C, the maximum decomposition temperature is 540°C, and the residual carbon content is 31.57%.

[0039] Figure 3 This is the temperature change curve of polyimide composite aerogel under different applied voltages. The highest temperature of aerogel can reach 211℃, which has a good electrical heating effect.

[0040] Figure 4 The temperature change curve of polyimide composite aerogel under different light intensities. Under the three light intensities, the initial temperature of the aerogel is 27.6℃. -2 After irradiation for 90 min, the aerogel temperature reached 86.7 °C. Other conditions remained unchanged, and the light intensity was changed to 0.08 W / cm -2 When the light intensity is 0.18W / cm -2 When the temperature reaches 133 °C, it indicates that the polyimide composite aerogel has excellent photothermal conversion ability.

[0041] Example 2

[0042] The difference between this embodiment and embodiment 1 is that the amount of multi-walled carbon nanotubes added in step (3) is 1 wt % of the mass of the triethylamine aqueous solution, and the other treatment methods are consistent with those in embodiment 1.

[0043] Example 3

[0044] The difference between this embodiment and embodiment 1 is that the amount of multi-walled carbon nanotubes added in step (3) is 3 wt % of the mass of the triethylamine aqueous solution, and the other treatment methods are consistent with those in embodiment 1.

[0045] Example 4

[0046] The difference between this embodiment and embodiment 1 is that the amount of PAA salt added in step (3) is 3 wt % of the mass of the triethylamine aqueous solution, and the other treatment methods are consistent with those in embodiment 1.

[0047] Example 5

[0048] The difference between this embodiment and embodiment 1 is that the amount of PAA salt added in step (3) is 4 wt % of the mass of the triethylamine aqueous solution, and the other treatment methods are consistent with those in embodiment 1.

[0049] Example 6

[0050] The difference between this embodiment and embodiment 1 is that the amount of PAA salt added in step (3) is 7 wt % of the mass of the triethylamine aqueous solution, and the other treatment methods are consistent with those in embodiment 1.

[0051] Example 7

[0052] The difference between this embodiment and embodiment 1 is that the amount of PAA salt added in step (3) is 9 wt % of the mass of the triethylamine aqueous solution, and the other treatment methods are consistent with those in embodiment 1.

[0053] Example 8

[0054] The difference between this embodiment and embodiment 1 is that the dianhydride monomer of the prepared aerogel is 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), and other processing methods are consistent with those in embodiment 1.

[0055] Example 9

[0056] The difference between this embodiment and embodiment 1 is that the dianhydride monomer of the prepared aerogel is pyromellitic dianhydride (PMDA), and other processing methods are consistent with those in embodiment 1.

[0057] Comparative Example 1

[0058] The difference between this embodiment and embodiment 1 is that the filler added to the prepared aerogel is 2% polyaniline, and the other treatment methods are consistent with those in embodiment 1. Preparation of PAA composite aerogel:

[0059] After preparing triethylamine aqueous solution (1.5 g TEA, 28.5 g deionized water) in a ratio of triethylamine: deionized water = 1:19, 1.5 g PAA salt was added, and after magnetic stirring until completely dissolved, 0.6 g polyaniline (PAn) was added. After ultrasonic treatment for 30 minutes, the mixture was poured into a mold, frozen in a cold well (-70°C) for 24 hours, and then vacuum-dried for 48 hours to obtain PAA composite aerogel.

[0060] The aerogel prepared in the example was tested, and the test results are shown in Table 1 and Table 2:

[0061] Table 1

[0062]

[0063] Table 2

[0064] Sample No. PAAs solid content wt% Electric heating temperature ℃ Light heating temperature℃ Example 1 5 211 133 Example 2 5 107 69 Example 3 5 279 105 Example 4 3 112 49 Example 5 4 189 55 Example 6 7 192 121 Example 7 9 183 118 Example 8 5 198 103 Example 9 5 187 97 Comparative Example 1 5 153 58

[0065] The above is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technician familiar with the present invention can make some changes or modify the technical contents suggested above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the solution of the present invention.

Claims

1. A polyimide composite aerogel with optical heating and electrical heating functions, characterized in that: The composite aerogel is prepared by reacting 5-norbornene-2,3-dicarboxylic anhydride, dianhydride monomer and 3,5-diaminobenzoic acid in a solvent to form an anhydride-terminated polyamic acid solution, adding triethylamine to adjust the reaction, precipitating polyamic acid salt with acetone, adding the polyamic acid salt and multi-walled carbon nanotubes into a triethylamine aqueous solution, and obtaining a cross-linked polyimide composite aerogel through freeze drying and thermal imidization.

2. The polyimide composite aerogel with optical heating and electrical heating functions according to claim 1, characterized in that: The dianhydride monomer is one or more of 3,3',4,4'-diphenyl phenone tetracarboxylic dianhydride, pyromellitic dianhydride, 4,4'-biphenyl ether dianhydride, or 3,3',4,4'-biphenyl tetracarboxylic dianhydride.

3. The polyimide composite aerogel with optical heating and electrical heating functions according to claim 1, characterized in that: The steps of preparing the polyamic acid salt are as follows: (1) adding dianhydride monomer, 3,5-diaminobenzoic acid, and 5-norbornene-2,3-dicarboxylic anhydride to a purified NN dimethylacetamide solvent, and then adding triethylamine for catalytic reaction to obtain a polyimide precursor polyamic acid solution; (2) Pour the polyamic acid solution obtained in step (1) into acetone to precipitate filamentous PAA salt.

4. The polyimide composite aerogel with optical heating and electrical heating functions according to claim 3, characterized in that: The molar ratio of the 3,5-diaminobenzoic acid, the dianhydride monomer and the 5-norbornene-2,3-dicarboxylic anhydride is 11:10:

10.

5. The polyimide composite aerogel with optical heating and electrical heating functions according to claim 3, characterized in that: The amount of triethylamine added is 3-4 times the molar amount of (-COOH), and vigorous magnetic stirring is required when pouring acetone.

6. The polyimide composite aerogel with optical heating and electrical heating functions according to claim 1, characterized in that: The steps of preparing the polyimide composite aerogel are as follows: (1) dissolving PAA salt in a triethylamine aqueous solution, then adding multi-walled carbon nanotubes to obtain a mixed solution, and then freeze-drying the mixed solution to obtain a PAA composite aerogel; (2) placing the composite aerogel obtained in step (1) into a high-temperature oven for thermal imidization reaction to obtain a polyimide composite aerogel.

7. The polyimide composite aerogel with optical heating and electrical heating functions according to claim 6, characterized in that: The polyamic acid salt is added in an amount of 3-9 wt % of the triethylamine aqueous solution, and the multi-walled carbon nanotube is added in an amount of 1-3 wt % of the triethylamine aqueous solution.

8. The polyimide composite aerogel with optical heating and electrical heating functions according to claim 6, characterized in that: In the triethylamine aqueous solution, the mass volume ratio of triethylamine to deionized water is 1:

19.

9. The polyimide composite aerogel with optical heating and electrical heating functions according to claim 6, characterized in that: The freeze-drying conditions are: -80°C≤temperature≤-50°C, pressure≤1Pa, freezing for 24 hours, and vacuum drying for 48 hours; the thermal imidization process in the high-temperature oven is: 100°C, 2 hours to remove moisture, and 200°C and 300°C for one hour each to complete the imidization.

10. An application of the polyimide composite aerogel with light heating and electric heating functions according to any one of claims 1 to 9, characterized in that: The composite aerogel is used as a photovoltaic heating material.

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