CN106633169A - Carbon-black-filled polyimide-based compound aerogel material and preparation method thereof - Google Patents

Abstract

The invention belongs to the technical field of composite airgel, in particular to a polyimide-based composite airgel material filled with carbon black and a preparation method thereof. The composition of the composite airgel of the present invention comprises: one or more water-soluble polyimide precursors - polyamic acid, and one or more carbon blacks. The preparation method comprises: preparation of oxidized carbon black dispersion; preparation of polyamic acid-oxidized carbon black hydrogel by sol-gel process; preparation of polyamic acid-oxidized carbon black aerogel by freeze-drying; Synthesis of polyimide-carbon black composite airgel. The cost of raw materials for preparing polyimide composite airgel in the invention is low, the method is simple and easy, and the prepared composite airgel has uniform microscopic appearance. In addition, the prepared polyimide-based composite airgel has excellent mechanical strength, heat resistance, and low dielectric constant, making it an ideal high-temperature dielectric material.

Description

A kind of polyimide-based composite airgel material filled with carbon black and preparation method thereof

technical field

The invention belongs to the technical field of composite airgel, and in particular relates to a polyimide-based composite airgel material filled with carbon black and a preparation method thereof.

Background technique

Polymer airgel is a kind of porous gel material based on natural or synthetic polymers, which has the characteristics of easy molding, high porosity, high specific surface area, low density, and low thermal conductivity. Therefore, polymer airgel is gradually used as a matrix material in heat insulation, sound insulation and dielectric materials. However, polymer aerogels generally have problems such as poor mechanical properties, poor thermal stability, and flammability. The reason is mainly caused by the poor mechanical properties of the polymer matrix and the low thermal decomposition temperature.

As an engineering plastic, polyimide has good mechanical properties and thermal stability, and is an ideal polymer airgel matrix material. Compared with other polymer-based aerogels, polyimide-based airgel not only has the above advantages, but also has the characteristics of high mechanical strength and good thermal stability, and is an ideal high-performance aerospace application material. Generally, polyimide aerogels need to use cross-linking agents during the preparation process to reduce the shrinkage of the aerogels. However, most of the crosslinking agents currently used in the preparation of polyimide airgel are expensive and have not been commercialized, which limits their large-scale use. Therefore, a method with a wide range of sources and low cost is needed to solve the shrinkage problem of polyimide airgel during the preparation process. Among them, nanoparticles are widely used to reinforce composite materials because of their unique properties. However, nanoparticles are easy to agglomerate and difficult to disperse in the polymer matrix, resulting in insignificant performance improvement of composite materials.

Contents of the invention

The present invention aims at the problem that the cross-linking agent used in the preparation process of polyimide airgel is expensive and limited in use, and proposes a method of using carbon black as the cross-linking agent and improving the carbon density by preparing oxidized carbon black. Dispersibility of black, method for preparing carbon black-filled polyimide composite aerogels.

The invention provides a method for preparing a carbon black-filled polyimide composite airgel material, the raw material composition of which comprises one or more water-soluble polyimide precursors-polyamic acid, one or more carbon Black, one or more graphene oxides, wherein the mass ratio of polyamic acid to carbon black is 100: 0.2-100: 10, the specific steps of preparation are:

(1) Mix carbon black and sodium nitrate and stir, then add concentrated sulfuric acid, and continue stirring to obtain a mixture of carbon black-sodium nitrate-sulfuric acid;

(2) Slowly add potassium permanganate into the mixed solution of carbon black-sodium nitrate-sulfuric acid, and stir to obtain the mixed solution of carbon black;

(3) Slowly add deionized water into the mixed solution of carbon black, and add hydrogen peroxide to obtain a dispersion of oxidized carbon black;

(4) Filtrate the oxidized carbon black dispersion, and wash with hydrochloric acid until no sulfate ions are detected to obtain an oxidized carbon black filter cake;

(5) drying the oxidized carbon black filter cake to obtain oxidized carbon black solid;

(6) Disperse oxidized carbon black in deionized water and ultrasonically obtain a stable dispersed oxidized carbon black dispersion;

(7) Dissolving the water-soluble polyamic acid in the oxidized carbon black dispersion to obtain a polyamic acid-oxidized carbon black solution;

(8) Place the polyamic acid-oxidized carbon black solution for a period of time, and obtain a polyamic acid-oxidized carbon black hydrogel through a sol-gel process;

(9) Precool the polyamic acid-oxidized carbon black hydrogel for a period of time, then transfer it to a refrigerator or liquid nitrogen to freeze it into a solid, and then freeze-dry it in a freeze dryer to obtain polyamic acid-oxidized carbon black Aerogel;

(10) Thermal imidization of polyamic acid-oxidized carbon black aerogels was carried out in a nitrogen atmosphere to prepare polyimide-carbon black aerogels.

Further, the carbon black in step (1) is selected from carbon black for coloring, carbon black for rubber, conductive carbon black and special carbon black.

Further, the mass ratio of carbon black to sodium nitrate in step (1) is 1.5:1-1.2:1.

Further, the mass ratio of concentrated sulfuric acid to carbon black in step (1) is 60: 1-45: 1.

Further, in step (2), the mass ratio of potassium permanganate to carbon black is 5:1-3:1, and the stirring time is 10-30h.

Further, the amount of deionization in step (3) is 400-600 mL.

Further, the concentration of hydrogen peroxide in step (3) is 10-30%, and the dosage is 30-90 mL.

Further, the concentration of hydrochloric acid in step (4) is 5-10%.

Further, the drying temperature in step (5) is 50-80°C.

Further, the concentration of the oxidized carbon black dispersion in step (6) is 0.1-10 mg/mL.

Further, the mass fraction of polyamic acid in step (7) is 4-15%.

Further, the standing time in step (8) is 2-24 h.

Further, the pre-cooling time in step (9) is 5-24 h, the pre-cooling temperature is 1-5°C, and the drying time in a freeze dryer is 24-72 h.

Further, the thermal imidization process described in step (10) is as follows: the obtained polyamic acid-based composite airgel is placed in a tube furnace and heated to 290-300°C in a nitrogen atmosphere, and kept for 0.5 -6 h.

Further, the temperature raising process is to gradually raise the temperature to 90-100 °C, 190-200 °C and 290-300 °C, and keep warm for 0.5-1.5 h respectively.

The raw material cost of the polyimide composite airgel prepared by the invention is low, the method is simple and easy, and the prepared composite airgel has a uniform microscopic appearance. In addition, the prepared polyimide-based composite airgel has excellent mechanical strength, heat resistance, and low dielectric constant, making it an ideal high-temperature dielectric material.

Description of drawings

Fig. 1 is the infrared spectrum of oxidized carbon black and untreated carbon black in the present invention.

Fig. 2 is a scanning electron micrograph of polyimide airgel PI in the present invention.

Figure 3 is a scanning electron micrograph of the polyimide-based composite airgel PI/CB _2% in the present invention.

Fig. 4 is a scanning electron microscope image of polyimide-based composite airgel PI/CB _4% in the present invention.

Fig. 5 is a scanning electron microscope image of polyimide-based composite airgel PI/CB _6% in the present invention.

detailed description

The present invention will be described in further detail below in conjunction with specific examples. It should be understood that these examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the teachings of the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of the present application.

Example 1

This embodiment includes the following steps:

Using N,N -dimethylacetamide as a solvent, 4,4'-diaminodiphenyl ether and pyromellitic anhydride as monomers, condensation polymerization is carried out in an ice-water bath to prepare polyamic acid filaments. The specific process is as follows: at room temperature, firstly, 8 g (0.04 mol) of 4,4′-diaminodiphenyl ether was fully dissolved in 95 g of N,N -dimethylacetamide, and the solution was clear with no particles. Then 8.85 g (0.046 mol) pyromellitic anhydride was added slowly, and then the reaction was moved to an ice-water bath and stirred for 2 h. Then add 0.04 mol triethylamine, continue to stir and react for about 2 h, and prepare a polyamic acid solution with a solid content of 15%. The prepared polyamic acid solution is sealed and stored, and after standing for two days, it is slowly poured into ice water, washed, frozen, and dried to obtain a water-soluble polyamic acid filament for use.

Take 30 mL of deionized water, add 2 g of polyamic acid filaments and 1 g of triethylamine, sonicate for 1 h, and stir for 0.5 h to dissolve and disperse the polyamic acid evenly to obtain an aqueous solution of polyamic acid. Triethylamine can be coated on the terminal carboxyl functional group of polyamic acid, so that polyamic acid is easily soluble in deionized water. Then it was transferred to a mold and ultrasonicated for 0.5 h, then the mold was transferred to a refrigerator at about 4°C for 5 h, and then put into liquid nitrogen to freeze it into a solid quickly, and then placed in a vacuum of 10 ~ 20 Pa Freeze-dried for 48 h to obtain polyamic acid airgel.

The obtained polyamic acid airgel was placed in a tube furnace, and the heating program was controlled in a nitrogen atmosphere, that is, the temperature was raised from room temperature to 100 °C for 30 min, and the temperature was kept for 1 h; h; from 200°C to 300°C, heat up for 30 minutes and hold for 1 hour to obtain polyimide airgel, denoted as PI.

Example 2

This embodiment includes the following steps:

The steps for preparing water-soluble polyamic acid are the same as in Example 1.

The steps of preparing oxidized carbon black are as follows:

Take acetylene black (specific surface area 75 m ² /g, apparent density 90-120 g/L) as an example to prepare oxidized carbon black. Add 5 g of carbon black to a 1000 mL beaker, add 3.75 g of sodium nitrate, and stir for 10 min; then add 150 mL of concentrated sulfuric acid, and stir for 0.5 h; slowly add 20 g of potassium permanganate, after 0.5 h, stir for 20 h ; Slowly add 500 mL of deionized water, add 50 mL of 30% hydrogen peroxide after cooling, and stir for 1 h; filter the mixture with suction and wash with 10% hydrochloric acid until no sulfate ion is detected to obtain oxidized carbon black Wet filter cake; then dried at 70°C for 5 h to obtain oxidized carbon black solid.

The steps of preparing polyimide-carbon black composite airgel are as follows:

Take 40 mg of oxidized carbon black and add it to 30 mL of deionized water, and sonicate for 0.5 h to disperse the oxidized carbon black evenly. Add 2 g of polyamic acid and 1 g of triethylamine to the obtained oxidized carbon black dispersion, ultrasonicate for 1 h, and stir for 0.5 h to disperse the polyamic acid evenly, and obtain a polyamic acid-oxidized carbon black aqueous solution. All the other steps are the same as in Example 2. The obtained polyimide-carbon black composite airgel is denoted as PI/CB _2% .

Example 3

This embodiment includes the following steps:

The steps for preparing water-soluble polyamic acid are the same as in Example 1, and the steps for preparing oxidized carbon black are the same as in Example 2.

The steps of preparing polyimide-carbon black composite airgel are as follows:

Take 80 mg of oxidized carbon black and add it into 30 mL of deionized water, and sonicate for 0.5 h to make the oxidized carbon black disperse evenly. All the other are with embodiment 3. The obtained polyimide-carbon black composite airgel is recorded as PI/CB _4% .

Example 4

This embodiment includes the following steps:

The steps for preparing water-soluble polyamic acid are the same as in Example 1, and the steps for preparing oxidized carbon black are the same as in Example 2.

The steps of preparing polyimide-carbon black composite airgel are as follows:

Take 120 mg of oxidized carbon black and add it to 30 mL of deionized water, and sonicate for 0.5 h to make the oxidized carbon black disperse evenly. All the other are with embodiment 3. The obtained polyimide-carbon black composite airgel is recorded as PI/CB _6% .

Table 1 Components and properties of polyimide-based composite airgel

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Claims (10)

1. a kind of preparation method of the polyimide-based composite airgel material filled with carbon black, is characterized in that, raw material comprises: one or more water-soluble polyimide precursors-polyamic acid, one or A variety of carbon blacks, wherein the mass ratio of polyamic acid to carbon black is 100: 0.2-100: 10, and the specific steps of preparation are: (1) Mix carbon black and sodium nitrate and stir, then add concentrated sulfuric acid, and continue stirring to obtain a mixture of carbon black-sodium nitrate-sulfuric acid; (2) Slowly add potassium permanganate into the mixed solution of carbon black-sodium nitrate-sulfuric acid, and stir to obtain the mixed solution of carbon black; (3) Slowly add deionized water into the black dispersion, and add hydrogen peroxide to obtain the oxidized carbon black dispersion; (4) Filtrate the oxidized carbon black dispersion and wash it with hydrochloric acid until no sulfate ions are detected to obtain an oxidized carbon black filter cake; (5) drying the oxidized carbon black filter cake to obtain oxidized carbon black solid; (6) Disperse the oxidized carbon black in deionized water, and ultrasonically obtain a stable dispersed oxidized carbon black dispersion; (7) Dissolving the water-soluble polyamic acid in the oxidized carbon black dispersion to obtain a polyamic acid-oxidized carbon black solution; (8) Place the polyamic acid-oxidized carbon black solution for a period of time, and obtain a polyamic acid-oxidized carbon black hydrogel through a sol-gel process; (9) Precool the polyamic acid-oxidized carbon black hydrogel for a period of time, then transfer it to a refrigerator or liquid nitrogen to freeze it into a solid, and then freeze-dry it in a freeze dryer to obtain polyamic acid-oxidized carbon black Aerogel; (10) Thermal imidization of polyamic acid-oxidized carbon black aerogels was carried out in a nitrogen atmosphere to prepare polyimide-carbon black aerogels. 2. The preparation method according to claim 1, wherein the carbon black in step (1) is selected from carbon black for coloring, carbon black for rubber, conductive carbon black and special carbon black; carbon black and sodium nitrate The mass ratio of concentrated sulfuric acid and carbon black is 60: 1-45: 1. 3. The preparation method according to claim 1 or 2, characterized in that, the mass ratio of potassium permanganate and carbon black described in step (2) is 5: 1-3: 1, and the stirring time is 10-30 h. 4. The preparation method according to claim 3, characterized in that, in step (3), the amount of deionization is 400-600 mL; the concentration of hydrogen peroxide is 10-30%, and the amount is 30-90 mL. 5. The preparation method according to claim 1, 2 or 4, characterized in that the concentration of hydrochloric acid in step (4) is 5-10%; the drying temperature in step (5) is 50-80 °C. 6. The preparation method according to claim 5, wherein the concentration of the oxidized carbon black dispersion in step (6) is 0.1-10 mg/mL; the mass fraction of polyamic acid in step (7) is 4- 15%. 7. The preparation method according to claim 1, 2, 4 or 6, characterized in that the standing time in step (8) is 2-24h. 8. The preparation method according to claim 7, characterized in that the pre-cooling time in step (9) is 5-24 hours, the pre-cooling temperature is 1-5°C, and the drying time in the freeze dryer is 24 hours -72 h. 9. The preparation method according to claim 1, 2, 4, 6 or 8, characterized in that, the thermal imidization process described in step (10) is: the obtained polyamic acid-based composite gas condensation The glue is placed in a tube furnace and heated to 290-300°C in a nitrogen atmosphere, and kept for 0.5-6 h. 10. A carbon black-filled polyimide-based composite airgel material prepared by the preparation method according to any one of claims 1-9.