CN108250728A - A kind of polymer/graphene aeroge composite foam material and preparation method thereof - Google Patents

Abstract

The invention provides a kind of polymer/graphene airgel composite foam material, is made up of graphene airgel and thermoplastic polymer, takes graphene airgel as skeleton, and thermoplastic polymer is attached to the graphene airgel In terms of the three-dimensional network structure, the thermoplastic polymer has cells with a closed-cell structure, the composite foam material has an interconnected three-dimensional network structure, and the content of graphene airgel in the composite foam material is 0.5% to 10%. The invention also provides a preparation method of the composite foam material. The invention provides a new idea for solving the problem of agglomeration of graphene in polymer matrix materials.

Description

A kind of polymer/graphene airgel composite foam material and preparation method thereof

technical field

The invention belongs to the field of polymer composite foam materials, and relates to a polymer/graphene airgel composite foam material and a preparation method thereof.

Background technique

Polymer foam has excellent properties such as low density, sound absorption, shock absorption, and heat preservation, and has attracted extensive attention from the scientific and industrial circles. Foaming using supercritical fluid is a newly developed foaming technology. This technology is green and environmentally friendly. Its most important advantage is that it can reduce the weight of foam materials without losing its mechanical properties. In the process of preparing polymer foam materials, adding inorganic nanoparticles as a heterogeneous nucleating agent is an important means to reduce the cell size, increase the cell density and improve the cell structure of the material.

Graphene is one of the ideal fillers for improving polymer foams due to its unique structure and excellent physicochemical properties. When preparing polymer foam materials, using graphene as a heterogeneous nucleating agent, blending graphene with the polymer matrix and then foaming can not only optimize the cell size and cell structure, but also improve the electrical properties of the polymer matrix . The dispersion of graphene in polymers is crucial to the formation of conductive networks. The biggest problem at present is that graphene is very easy to agglomerate in polymers. Graphene agglomeration will not only hinder the formation of conductive networks, but also cause foaming When the cell quality is not good, such as uneven cell distribution and cell merging, and cell merging will lead to a wider cell size distribution, which will easily lead to uneven stress and stress concentration on the foam during use. phenomena are destroyed. Aiming at the problem of graphene agglomeration, a common improvement method in the prior art is to functionalize graphene. However, functionalization will cause damage to the lattice structure of graphene to a certain extent and affect the performance of polymer syntactic foams. Therefore, how to realize the uniform dispersion of graphene in polymers is still an important research direction in the field of polymer/graphene composite foams. According to the existing idea of preparing polymer/graphene composite foam materials, the graphene and polymer matrix are blended and then foamed to form composite foam materials. Due to the formation of cells in the foaming process, graphene The relative position will keep changing, and it is actually difficult to effectively control the position of graphene to form a complete graphene network. Therefore, even if the dispersion of graphene in the blend is improved, it may not guarantee the formation of graphene in the polymer. Highly connected three-dimensional conductive network.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies in the prior art, to provide a polymer/graphene airgel composite foam, to form a three-dimensional graphene network with high connectivity in the polymer composite foam, effectively improve composite foam The electrical and mechanical properties of the material provide a new idea different from the existing technology for solving the problem of agglomeration of graphene in polymer matrix materials.

The polymer/graphene airgel composite foam material provided by the invention is composed of graphene airgel and thermoplastic polymer, with graphene airgel as the skeleton, and the thermoplastic polymer is attached to the three-dimensional network of graphene airgel Structurally, the thermoplastic polymer has closed cells, and the composite foam has an interconnected three-dimensional network structure, and the content of graphene airgel in the composite foam is 0.5wt%-10wt%.

The pore size of the three-dimensional network structure of the above-mentioned polymer/graphene airgel composite foam material is 10～120 μ m, and the cell aperture of the closed-cell structure on the thermoplastic polymer attached to the three-dimensional network structure of the graphene airgel is 5~30μm.

In the above-mentioned polymer/graphene airgel composite foam material, said thermoplastic polymer is preferably polystyrene, polylactic acid, polypropylene or thermoplastic polyurethane etc., preferably, the content of graphene airgel in this composite foam material It is 2wt%～6wt%.

According to the needs of practical applications, by adjusting the content of graphene airgel in the polymer/graphene airgel composite foam and its three-dimensional network structure, the electrical conductivity of the composite foam can be adjusted, and thermoplastic polyurethane is selected as the polymer When used, the electrical conductivity of the composite foam material can be adjusted within the range of 0.12-0.6 S/cm.

The present invention also provides a kind of preparation method of above-mentioned polymer/graphene airgel composite foam material, and the steps are as follows:

(1) Preparation of graphene airgel

Add a reducing agent to the graphene oxide solution, mix well, and then reduce at 35-90°C for 1-24 hours to obtain a partially reduced graphene oxide hydrogel, soak the obtained hydrogel in water or ethanol-water solution for 2-7 days, and place in Freeze at -20~-10°C for 6~24h, then freeze dry in a freeze dryer for 36~72h, and then thermally reduce at 200~300°C for 2~3h to obtain graphene airgel; graphene oxide and reducing agent The mass ratio is 1:(1～10);

or

Add the aqueous polymer solution to the graphene oxide solution, mix well and let it stand at room temperature until the graphene oxide gels, freeze the obtained graphene oxide hydrogel at -20～-10°C for 6～24h, and then place Freeze drying in a freeze dryer for 36-72 hours, and then heat reduction at 400-1000°C for 0.2-2 hours to obtain graphene airgel; the mass ratio of graphene oxide to water-based polymer is 1:(0.1-10);

In the graphene oxide solution, the concentration of graphene oxide is 3-10 mg/mL, the carbon-to-oxygen ratio of graphene oxide is (1.4-3):1, and the size of graphene oxide is 5-30 μm.

(2) Preparation of polymer/graphene airgel composites

Vacuum the graphene airgel to fully remove the air therein, then place the vacuumized graphene airgel in a thermoplastic polymer solution with a concentration of 0.05-0.5g/mL, and let the thermoplastic polymer fully Attached to the three-dimensional network of graphene airgel, and then dried to obtain the polymer/graphene airgel composite material;

(3) Supercritical foaming

The polymer/graphene airgel composite foam material is obtained by supercritical foaming by rapid depressurization method or temperature rise method;

The rapid depressurization method is to place the polymer/graphene airgel composite material in the reactor, feed gas and heat up, pressurize to convert the gas into a supercritical fluid, and maintain the aforementioned temperature and pressure. When the supercritical fluid is compounded After the material reaches saturation, the pressure in the reactor is reduced to normal pressure by the rapid decompression method, and the product is cooled and shaped;

The heating method is to put the polymer/graphene airgel composite material in the reaction kettle, feed the gas, raise the temperature and pressurize, and maintain the aforementioned temperature and pressure. When the gas reaches saturation in the composite material, release the pressure and take out the foaming material. The green body is obtained by placing the foamed green body in an oil bath for 10-60 seconds, and then cooling and setting the shape. The temperature of the above oil bath is higher than the temperature in the reaction kettle.

In the above method, the graphene oxide solution is obtained by dispersing graphite oxide in water and mechanically stirring at a speed of 200-400 r/m or by ultrasonic oscillation with appropriate power. Graphite oxide is made from expandable graphite with a sheet size of 100-300 μm, reacted at 900-1000°C for 1-5 minutes to form expanded graphite, and then prepared by the modified Hummers method. The specific steps are as follows:

Stir the expanded graphite, sodium nitrate, and concentrated sulfuric acid in the ratio of 1g:0.5g:(30-100)mL for 5-20min under ice bath conditions, and slowly add 5-8g of potassium permanganate per 1g of expanded graphite Potassium permanganate, then react at 20-40°C for 2-5 hours, add deionized water to dilute according to the ratio of 100-300mL water per 1g of expanded graphite, and then add H ₂ O ₂ with an excess concentration of 5wt%-30wt% The solution terminates the reaction, is washed repeatedly with hydrochloric acid and deionized water, and then centrifuged. When the supernatant obtained by centrifugation becomes neutral, it is freeze-dried for 2 to 4 days to obtain graphite oxide. The carbon-oxygen molar ratio of graphite oxide can be adjusted by adjusting the ratio of expanded graphite, sodium nitrate and concentrated sulfuric acid, the amount of potassium permanganate added, reaction temperature and reaction time.

In the step (1) of the above method, when the partially reduced graphene oxide hydrogel or graphene oxide hydrogel is frozen, the size of the ice crystals formed by freezing will affect the network structure of the graphene airgel. By adjusting the freezing temperature and freezing time can adjust the growth rate of the ice crystals, and then change the size of the ice crystals. In this step, the growth rate of the ice crystals should be as slow as possible.

In step (1) of the above method, the reducing agent is ascorbic acid, ethylenediamine, sodium borohydride or hydrazine hydrate, etc., and the aqueous polymer is polyvinyl alcohol, polypyrrolidone, polyacrylamide or hydroxypropyl cellulose, etc.

In the step (2) of the above method, the thermoplastic polymer is polystyrene, polylactic acid, polypropylene or thermoplastic polyurethane.

In the step (2) of above-mentioned method, the content of polymer in polymer/graphene airgel composite depends on the attachment amount of polymer in graphene airgel three-dimensional network structure in this step, and polymer is in graphite The amount of attachment on the graphene airgel mainly depends on the three-dimensional network structure of the graphene airgel skeleton, especially the pore size of the graphene three-dimensional network structure, while the vacuum degree of this step and the standing time in the vacuum environment and thermoplasticity. The concentration of the polymer solution also affects the amount of polymer attached in the graphene aerogel. This is also one of the key points of step (3) whether supercritical foaming can form effective cells in the polymer attached to the three-dimensional network structure of the graphene airgel.

In the step (2) of the above method, the graphene airgel is placed in a closed environment, evacuated to -0.1 ~ -0.08MPa and kept in the vacuum environment for 1 ~ 5min to fully remove the air therein, and then placed in a thermoplastic Place the polymer solution in a closed environment, evacuate to -0.1~-0.08MPa and keep it in this vacuum environment for 0.5~3h, and then stand at normal pressure for 0.5~2h to make the thermoplastic polymer fully adhere to the graphene gas. In the three-dimensional network of the gel, the polymer/graphene airgel composite is finally obtained by drying.

In step (2) of the above method, the electrical conductivity of the polymer/graphene airgel composite foam material finally obtained can be adjusted by changing the concentration of the thermoplastic polymer solution.

In the step (3) of the above method, the gas passed into the reactor is carbon dioxide, nitrogen, air or water vapor; when adopting the rapid depressurization method, the temperature of the control reactor is 35 ~ 160 ° C, and the pressure is 8 ~ 25MPa, The depressurization rate is 50-80MPa/s; when using the heating method, the temperature of the reactor is controlled to be 35-50°C, the pressure is 8-12MPa, the pressure relief rate is 4-8MPa/s, and the temperature of the oil bath is 80-150°C .

In the above method, the volume fraction of ethanol in the ethanol-water solution described in step (1) is 10% to 20%; in step (1), after adding the aqueous polymer solution to the graphene oxide solution and mixing, the resulting mixed solution is ultrasonically After removing the air bubbles therein, it was left to stand at room temperature until the graphene oxide gelled.

Compared with prior art, the present invention has produced following beneficial technical effect:

1. The polymer/graphene airgel composite foam material provided by the present invention is a novel composite foam material different from existing polymer/graphene composite foam material in structure, and this composite foam material is based on graphene airgel As a skeleton, a thermoplastic polymer is attached to the three-dimensional network structure of the graphene airgel, the thermoplastic polymer has cells with a closed-cell structure, and the composite foam material has an interconnected three-dimensional network structure. Since it is formed on the basis of a complete and highly connected graphene airgel network, it effectively avoids the problems of graphene agglomeration and uneven dispersion, and because graphene airgel itself has light weight and resilience Good, high mechanical strength, good electrical conductivity, etc., this makes the electrical properties, mechanical properties and adsorption properties of the polymer/graphene airgel composite material provided by the invention all better than existing polymers with graphene as filler / Graphene syntactic foam. Therefore, the composite material prepared by the present invention has the characteristics of graphene airgel and porous polymer foam material at the same time, and the composite foam material provided by the present invention has potential application value in the fields of adsorption materials, electronic devices and the like.

2. The present invention also provides a kind of preparation method of polymer/graphene airgel composite foam material, first prepare graphene airgel, then prepare polymer/graphene airgel based on graphene airgel The composite material is then supercritically foamed on the basis of this, so that the polymer attached to the three-dimensional network structure of the graphene airgel forms small cells with a closed-cell structure. The composite foam material of the present invention is prepared by using the graphene airgel with a stable and highly connected three-dimensional network structure as the skeleton, which effectively overcomes the graphene agglomeration that occurs after the foaming of graphene and polymers in the prior art Problems and the difficulty of forming a highly connected graphene conductive network make the electrical properties, mechanical properties and adsorption properties of the final polymer/graphene airgel composites better than those of polymer foams prepared by traditional methods, It provides a new idea different from the existing technology to solve the problem of agglomeration of graphene in polymer matrix materials.

3. due to the selection of the graphene oxide sheet size and the coordination and control of the process parameters in the method of the present invention, the pore size of the three-dimensional network structure of the prepared graphene airgel is reasonable, which is the successful polymerization of the present invention. One of the key of object/graphene airgel composite foam material, in addition the preparation of follow-up polymer/graphene airgel composite material and the technology of follow-up supercritical foaming cooperate properly, make the composite foam material prepared by the present invention have good The three-dimensional network structure and cell structure play an important role in the improvement of the electrical properties, adsorption properties and mechanical properties of syntactic foams.

4. The method of the present invention has simple operation and good process controllability, and production can be realized by using existing equipment, and has the characteristics of being easy to popularize and apply.

Description of drawings

Fig. 1 is the SEM picture of graphene airgel, thermoplastic polyurethane/graphene airgel composite material and thermoplastic polyurethane/graphene airgel composite foam material prepared in embodiment 1.

Detailed ways

The polymer/graphene airgel composite foam material provided by the present invention and the preparation method thereof are further described through examples below. It is necessary to point out that the following examples are only used to further illustrate the present invention, and cannot be interpreted as limiting the protection scope of the present invention. Those skilled in the art make some non-essential improvements and adjustments to the present invention according to the above-mentioned content of the invention and carry out specific implementation. Still belong to the scope of invention protection.

Example 1

(1) Preparation of graphite oxide

Using expandable graphite with a sheet size of about 200 μm as raw material, react at 900°C for 5 minutes to obtain expanded graphite, and prepare graphite oxide by modifying the Hummers method: mix expanded graphite, sodium nitrate, and concentrated sulfuric acid at a ratio of 1g:0.5g:100mL in Stir in an ice bath for 10 minutes, slowly add potassium permanganate according to the ratio of 8g potassium permanganate per 1g of expanded graphite, after adding potassium permanganate, react at 35°C for 2.5h, and then add 8g of potassium permanganate per 1g of expanded graphite The ratio of 200mL water was diluted with _deionized water, and 120mL of _H2O2 solution with a concentration of 5wt% was added to terminate the reaction. After repeated washing with hydrochloric acid and deionized water, centrifugation was carried out. When the supernatant obtained by centrifugation was neutral, Freeze-dry for 48 hours to obtain graphite oxide. The carbon-to-oxygen molar ratio of the graphite oxide prepared in this step was measured, and the result was 1.5:1.

(2) Preparation of graphene airgel

Graphite oxide was added into deionized water, and mechanically stirred at a speed of 200 r/m for 2 h to obtain a 10 mg/mL graphene oxide solution, wherein the sheet size of graphene oxide was 10-25 μm. Add 10mL, 50mg/mL polyvinyl alcohol solution to 10mL, 10mg/mL graphene oxide solution, stir mechanically at 200r/m for 2h and mix evenly, then ultrasonically remove air bubbles with 400W power for 20min, and let it stand at room temperature Until the graphene oxide is gelled, the resulting graphene oxide hydrogel is frozen at -18°C for 12 hours, then placed in a freeze dryer and freeze-dried for 48 hours under a pressure not exceeding 20 Pa, and then transferred to a tubular resistance furnace In the process, the temperature was raised to 1000° C. at a heating rate of 10° C./min and kept at this temperature for 15 minutes to obtain graphene airgel.

(3) Preparation of thermoplastic polyurethane/graphene airgel composites

The polyether thermoplastic polyurethane was vacuum-dried at 80°C for 12h, then 10g of the dried polyether thermoplastic polyurethane was dissolved in 50mL of N-N dimethylformamide to obtain a thermoplastic polyurethane solution, and the graphene prepared in step (2) was Air condensation is placed in a vacuum drying oven, vacuumed to -0.1 ~ -0.08MPa and kept at this vacuum for 5 minutes to fully remove the air in the graphene airgel, and then the graphene airgel after vacuuming Immerse in the thermoplastic polyurethane solution, evacuate to -0.1～-0.08MPa and keep it under the vacuum for 1h, then let it stand at normal pressure for 2h, so that the thermoplastic polyurethane can fully enter the three-dimensional network of graphene airgel, and then The thermoplastic polyurethane/graphene airgel composite material is obtained by drying under normal pressure.

(4) Supercritical foaming

Put the thermoplastic polyurethane/graphene airgel composite material in a high-pressure reactor, feed carbon dioxide and raise the temperature to 105 ° C, pressurize to 12 MPa to convert carbon dioxide into a supercritical fluid, and keep it under the aforementioned temperature and pressure conditions for 2 hours. The critical fluid reaches a saturated state in the composite material, and the pressure in the high-pressure reactor is reduced to normal pressure at a rate of about 80MPa/s by the rapid decompression method to make the composite material foam, and then to the cooling water system of the high-pressure reactor Add tap water to the medium to cool and shape the foamed product to obtain a thermoplastic polyurethane/graphene airgel composite foam material.

Fig. 1 is the SEM figure of graphene airgel, thermoplastic polyurethane/graphene airgel composite material and thermoplastic polyurethane/graphene airgel composite foam material prepared in this embodiment, wherein, Fig. a1～a3 is graphene airgel SEM images of the gel at different magnifications. Figures b1 to b3 are SEM images of thermoplastic polyurethane/graphene airgel composites at different magnifications. Figures c1 to c3 are thermoplastic polyurethane/graphene airgel composite foams SEM images of the material at different magnifications. It can be seen from Figure 1 that graphene airgel has a uniform connected three-dimensional network structure. After compounding with thermoplastic polyurethane, the three-dimensional network structure of graphene airgel still exists, and thermoplastic polyurethane is attached to the surface of the graphene airgel pore wall. After foaming by supercritical carbon dioxide, the three-dimensional network structure of the composite material is not destroyed, and the polymer in the composite material forms a microporous structure. After testing, the pore size of the three-dimensional network structure of the composite foam material is 10-120 μm, the pore size of the closed-cell structure on the thermoplastic polyurethane is 5-30 μm, and the graphene airgel content in the composite foam material is 5.47 % by weight, the electrical conductivity of the syntactic foam is 0.58 S/cm.

Example 2

In this implementation, the preparation of thermoplastic polyurethane/graphene airgel composite foam material, the steps are as follows:

(1) Preparation of graphite oxide

Using expandable graphite with a sheet size of about 300 μm as raw material, graphite oxide was prepared according to the method in step (1) of Example 1.

(2) Preparation of graphene airgel

Disperse graphite oxide in water, and mechanically stir at 200 r/m for 1 h to obtain a 5 mg/mL graphene oxide solution. The sheet size of graphene oxide is 20-30 μm. Add 100mg of ascorbic acid to 10mL, 5mg/mL graphene oxide solution, stir mechanically at a speed of 200r/m for 15min and mix well, and then place it in an oil bath at 90°C under airtight conditions for heating and reduction for 3h to obtain partially reduced oxidized Graphene hydrogel, soak the obtained hydrogel in deionized water for 7 days, replace it with new deionized water every 24 hours, then freeze it at -10°C for 24 hours, place it in a freeze dryer under pressure Freeze-drying for 36 hours under the condition of no more than 20Pa, and then heat reduction at 200°C for 3 hours to obtain graphene airgel.

(3) Preparation of thermoplastic polyurethane/graphene airgel composites

The polyether thermoplastic polyurethane was vacuum-dried at 80°C for 12h, then 10g of the dried polyether thermoplastic polyurethane was dissolved in 50mL of tetrahydrofuran to obtain a thermoplastic polyurethane solution, and the graphene gas prepared in step (2) was placed in a vacuum In the drying oven, vacuumize to -0.1～-0.08MPa and keep it under the vacuum for 2 minutes to fully remove the air in the graphene airgel, and then immerse the vacuumized graphene airgel in the thermoplastic polyurethane solution In the process, vacuumize to -0.1～-0.08MPa and keep it under the vacuum degree for 0.5h, then let it stand at normal pressure for 1.5h, so that the thermoplastic polyurethane can fully enter the three-dimensional network of graphene airgel, and then under normal pressure After drying, the thermoplastic polyurethane/graphene airgel composite material is obtained.

(4) Supercritical foaming

Put the thermoplastic polyurethane/graphene airgel composite material in a high-pressure reactor, feed carbon dioxide and raise the temperature, pressurize to 140°C and 10MPa to convert carbon dioxide into a supercritical fluid, and keep it under the aforementioned temperature and pressure conditions for 3h. The critical fluid reaches saturation in the composite material, and the pressure in the high-pressure reactor is reduced to normal pressure at a rate of about 60MPa/s by the rapid depressurization method to make the composite material foam, and then to the cooling water system of the high-pressure reactor Add tap water to the medium to cool and shape the foamed product to obtain a thermoplastic polyurethane/graphene airgel composite foam material. The content of graphene airgel in the composite foam material is 2.45wt%, and the electrical conductivity of the composite foam material is 0.12S/cm.

Example 3

In this implementation, the preparation of polystyrene/graphene airgel composite foam material, the steps are as follows:

(1) Preparation of graphite oxide

Graphite oxide was prepared according to the method in Example 1 step (1).

(2) Preparation of graphene airgel

Disperse graphite oxide in water, and ultrasonically stir at a speed of 200 r/m for 0.5 h to obtain a 3 mg/mL graphene oxide solution. The sheet size of graphene oxide is 10-25 μm. Add 120mg of ethylenediamine to 10mL, 3mg/mL graphene oxide solution, stir mechanically at a speed of 200r/m for 15min to mix evenly, then place it in an oven under airtight conditions and heat reduction at 80°C for 1h to obtain partially reduced Graphene oxide hydrogel, soaking the obtained hydrogel with ethanol-water solution with ethanol volume percentage of 20% for 2 days, during which a new ethanol water solution was replaced every 12 hours, and then placed under the condition of -20°C for 6 hours, placed Freeze-dry in a freeze dryer for 72 hours under the condition that the pressure does not exceed 20 Pa, and then thermally reduce at 300° C. for 2 hours to obtain graphene airgel.

(3) Preparation of polystyrene/graphene airgel composites

Dissolve 10g of polystyrene in 100mL of N-N dimethylformamide to obtain a polystyrene solution, place the graphene gas condensation prepared in step (2) in a vacuum drying oven, and evacuate to -0.1～-0.08MPa And keep it under the vacuum for 2 minutes to fully remove the air in the graphene airgel, then immerse the vacuumized graphene airgel in the polystyrene solution, vacuumize to -0.1～-0.08MPa and Keep it under the vacuum degree for 1.5h, and then stand at normal pressure for 2h to make polystyrene fully enter the three-dimensional network of graphene airgel, and then dry it under normal pressure to obtain polystyrene/graphene airgel composite Material.

(4) Supercritical foaming

The polystyrene/graphene airgel composite material is placed in a high-pressure reactor, and carbon dioxide is introduced and heated, pressurized to 80°C and 22MPa to convert carbon dioxide into a supercritical fluid, and maintained under the aforementioned temperature and pressure conditions for 3h, The supercritical fluid reaches a saturated state in the composite material, and the pressure in the high-pressure reactor is reduced to normal pressure at a rate of about 50MPa/s by the rapid depressurization method to make the composite material foam, and then the cooling water of the high-pressure reactor Tap water is fed into the system to cool and shape the foamed product to obtain a polystyrene/graphene airgel composite foam material, and the graphene airgel content in the composite foam material is 4.47wt%.

Example 4

In this implementation, the preparation of polylactic acid/graphene airgel composite foam material, the steps are as follows:

(1) Preparation of graphite oxide

Using expandable graphite with a sheet size of about 100 μm as raw material, graphite oxide was prepared according to the method in step (1) of Example 1.

(2) Preparation of graphene airgel

Disperse the graphite oxide prepared in step (1) into water, and ultrasonically stir for 4 hours at a speed of 400 r/m to obtain a 5 mg/mL graphene oxide solution, and the sheet size of the graphene oxide is 5-10 μm. Add 10mL, 5mg/mL polyvinyl alcohol solution to 10mL, 5mg/mL graphene oxide solution, stir mechanically at a speed of 400r/m for 2h and mix evenly, then use 400W power to ultrasonic for 20min to remove air bubbles, and stand at room temperature until Graphene oxide is gelled, and the resulting graphene oxide hydrogel is frozen at -18°C for 12 hours, then placed in a freeze dryer and freeze-dried for 48 hours under a pressure not exceeding 20 Pa, and then transferred to a tubular resistance furnace , the temperature was raised to 1000° C. at a heating rate of 10° C./min and kept at this temperature for 25 minutes to obtain graphene airgel.

(3) Preparation of polylactic acid/graphene airgel composites

Dissolve 10g of polylactic acid in 50mL of chloroform to obtain a polylactic acid solution, place the graphene gas condensation prepared in step (2) in a vacuum drying oven, evacuate to -0.1～-0.08MPa and in this vacuum degree Keep it for 1min to fully remove the air in the graphene airgel, then immerse the vacuumized graphene airgel in the polylactic acid solution, vacuumize to -0.1～-0.08MPa and keep it under the vacuum degree 3h, and then stand at normal pressure for 0.5h, so that the polylactic acid can fully enter the three-dimensional network of the graphene airgel, and then dry under normal pressure to obtain the polylactic acid/graphene airgel composite material.

(4) Supercritical foaming

Place the polylactic acid/graphene airgel composite material in a high-pressure reactor, feed nitrogen and raise the temperature, pressurize to 130°C and 14MPa to convert nitrogen into a supercritical fluid, and keep it under the aforementioned temperature and pressure conditions for 4h. The critical fluid reaches a saturated state in the composite material, and the pressure in the high-pressure reactor is reduced to normal pressure at a rate of about 80MPa/s by the rapid decompression method to make the composite material foam, and then to the cooling water system of the high-pressure reactor Feed tap water into the middle to make the foamed product cool and shape to obtain polylactic acid/graphene airgel composite foam material, the content of graphene airgel in this composite foam material is 2.23wt%.

Example 5

In this implementation, the preparation of polypropylene/graphene airgel composite foam material, the steps are as follows:

(1) Preparation of graphite oxide

Graphite oxide was prepared according to the method in Example 1 step (1).

(2) Preparation of graphene airgel

Disperse the graphite oxide prepared in step (1) into water, and ultrasonically stir for 4 hours at a speed of 200 r/m to obtain a 10 mg/mL graphene oxide solution, and the sheet size of the graphene oxide is 10-25 μm. Add 10 mL, 1 mg/mL hydroxypropyl cellulose solution to 10 mL, 10 mg/mL graphene oxide solution, stir mechanically at a speed of 200 r/m for 2 h to mix evenly, then use 400 W power for 20 min to remove air bubbles, and statically Put the graphene oxide gel until the graphene oxide is gelled, freeze the obtained graphene oxide hydrogel at -18°C for 12 hours, and then freeze-dry it in a freeze dryer for 48 hours under the condition that the pressure does not exceed 20Pa, and then transfer it to the tube resistor In the furnace, the temperature was raised to 400° C. at a heating rate of 10° C./min and kept at this temperature for 2 hours to obtain graphene airgel.

(3) Preparation of polypropylene/graphene airgel composites

Dissolve 10g of polypropylene in 20mL of toluene to obtain a polypropylene solution, place the graphene gas condensation prepared in step (2) in a vacuum drying oven, evacuate to -0.1～-0.08MPa and keep it under the vacuum degree 4min to fully remove the air in the graphene airgel, then immerse the vacuumized graphene airgel in the polypropylene solution, vacuumize to -0.1～-0.08MPa and keep it under the vacuum for 2h, Then stand at normal pressure for 2 hours, so that the polypropylene fully enters the three-dimensional network of the graphene airgel, and then dry under normal pressure to obtain the polypropylene/graphene airgel composite material.

(4) Supercritical foaming

The polypropylene/graphene airgel composite material is placed in a high-pressure reactor, and carbon dioxide is introduced to heat up, pressurize to 35°C and 12MPa to convert carbon dioxide into a supercritical fluid, and keep it under the aforementioned temperature and pressure conditions for 12h. The critical fluid reaches saturation in the composite material, and the pressure in the autoclave is reduced to normal pressure at a depressurization rate of about 4MPa/s to obtain a foamed body. The foamed body is taken out and placed in an oil bath at 140°C to maintain 50s, then take it out, cool and shape to get the polypropylene/graphene airgel composite foam material.

Example 6

In this implementation, the preparation of polystyrene/graphene airgel composite foam material, the steps are as follows:

(1) Preparation of graphite oxide

Graphite oxide was prepared according to the method in Example 1 step (1).

(2) Preparation of graphene airgel

Disperse graphite oxide in water, and ultrasonically stir at a speed of 200 r/m for 0.5 h to obtain a 4 mg/mL graphene oxide solution. The sheet size of graphene oxide is 10-25 μm. Add 360mg sodium borohydride to 10mL, 4mg/mL graphene oxide solution, stir mechanically at a speed of 200r/m for 15min and mix well, then place it in a water bath at 35°C under airtight conditions for reduction for 24h to obtain partially reduced oxide Graphene hydrogel, soaking the obtained hydrogel with ethanol-water solution with ethanol volume percentage of 100% for 4 days, during which a new ethanol water solution was replaced every 24 hours, then placed under the condition of -18°C for 12 hours, placed in Freeze drying in a freeze dryer for 48 hours under the condition that the pressure does not exceed 20 Pa, and then heat reduction at 250° C. for 2 hours to obtain graphene airgel.

(3) Preparation of polystyrene/graphene airgel composites

Dissolve 5g of polystyrene in 100mL of N-N dimethylformamide to obtain a polystyrene solution, place the graphene gas condensation prepared in step (2) in a vacuum drying oven, and evacuate to -0.1～-0.08MPa And keep it under the vacuum for 5min to fully remove the air in the graphene airgel, then immerse the vacuumized graphene airgel in the polystyrene solution, vacuumize to -0.1～-0.08MPa and Keep it under the vacuum for 3 hours, and then let it stand at normal pressure for 1 hour, so that polystyrene can fully enter the three-dimensional network of graphene airgel, and then dry it under normal pressure to obtain polystyrene/graphene airgel composite Material.

(4) Supercritical foaming

The polystyrene/graphene airgel composite material is placed in a high-pressure reactor, and carbon dioxide is introduced to heat up, pressurize to 50°C and 8MPa to convert carbon dioxide into a supercritical fluid, and keep it under the aforementioned temperature and pressure conditions for 4h, The supercritical fluid reaches a saturated state in the composite material, and the pressure in the high-pressure reactor is reduced to normal pressure at a decompression rate of about 8MPa/s to obtain a foamed body, and the foamed body is taken out and placed in an oil bath at 80°C Keep it for 10 seconds, then take it out, cool and set it to get the polystyrene/graphene airgel composite foam material.

Claims (10)

1. A polymer/graphene airgel composite foam material is characterized in that it is made up of graphene airgel and thermoplastic polymer, with graphene airgel as skeleton, and thermoplastic polymer is attached to graphene airgel The three-dimensional network structure, the thermoplastic polymer has cells of closed-cell structure, the composite foam material has an interconnected three-dimensional network structure, and the content of graphene airgel in the composite foam material is 0.5wt%-10wt%. 2. polymer/graphene airgel composite foam material according to claim 1, it is characterized in that the pore size of the three-dimensional network structure of this composite foam material is 10～120 μ m, the cell of the closed-cell structure on the thermoplastic polymer The pore size is 5-30 μm. 3. The polymer/graphene airgel composite foam material according to claim 1 or 2, wherein the thermoplastic polymer is polystyrene, polylactic acid, polypropylene or thermoplastic polyurethane or the like. 4. The polymer/graphene airgel composite foam material according to claim 3, characterized in that the graphene airgel content in the composite foam material is 2wt% to 6wt%. 5. the preparation method of polymer/graphene airgel composite foam material according to any one of claims 1 to 4, it is characterized in that the steps are as follows: (1) Preparation of graphene airgel Add a reducing agent to the graphene oxide solution, mix well, and then reduce at 35-90°C for 1-24 hours to obtain a partially reduced graphene oxide hydrogel, soak the obtained hydrogel in water or ethanol-water solution for 2-7 days, and place in Freeze at -20~-10°C for 6~24h, then freeze dry in a freeze dryer for 36~72h, and then thermally reduce at 200~300°C for 2~3h to obtain graphene airgel; graphene oxide and reducing agent The mass ratio is 1:(1～10); or Add the aqueous polymer solution to the graphene oxide solution, mix well and let it stand at room temperature until the graphene oxide gels, freeze the obtained graphene oxide hydrogel at -20～-10°C for 6～24h, and then place Freeze drying in a freeze dryer for 36-72 hours, and then heat reduction at 400-1000°C for 0.2-2 hours to obtain graphene airgel; the mass ratio of graphene oxide to water-based polymer is 1:(0.1-10); In the graphene oxide solution, the concentration of graphene oxide is 3-10 mg/mL, the carbon-to-oxygen ratio of graphene oxide is (1.4-3):1, and the size of graphene oxide is 5-30 μm. (2) Preparation of polymer/graphene airgel composites Vacuum the graphene airgel to fully remove the air therein, then place the vacuumized graphene airgel in a thermoplastic polymer solution with a concentration of 0.05-0.5g/mL, and let the thermoplastic polymer fully Attached to the three-dimensional network of graphene airgel, and then dried to obtain the polymer/graphene airgel composite material; (3) Supercritical foaming The polymer/graphene airgel composite foam material is obtained by supercritical foaming by rapid depressurization method or temperature rise method; The rapid depressurization method is to place the polymer/graphene airgel composite material in the reactor, feed gas and heat up, pressurize to convert the gas into a supercritical fluid, and maintain the aforementioned temperature and pressure. When the supercritical fluid is compounded After the material reaches saturation, the pressure in the reactor is reduced to normal pressure by the rapid decompression method, and the product is cooled and shaped; The heating method is to put the polymer/graphene airgel composite material in the reaction kettle, feed the gas, raise the temperature and pressurize, and maintain the aforementioned temperature and pressure. When the gas reaches saturation in the composite material, release the pressure and take out the foaming material. The green body is obtained by placing the foamed green body in an oil bath for 10-60 seconds, and then cooling and setting the shape. The temperature of the above oil bath is higher than the temperature in the reaction kettle. 6. according to the preparation method of the described polymer/graphene airgel composite foam material of claim 5, it is characterized in that, the reducing agent described in step (1) is ascorbic acid, ethylenediamine, sodium borohydride or hydrazine hydrate etc. 7. according to the preparation method of the described polymer/graphene airgel composite foam material of claim 5, it is characterized in that, the aqueous polymer described in step (1) is polyvinyl alcohol, polypyrrolidone, polyacrylamide or hydroxypropyl base cellulose etc. 8. according to the preparation method of the polymer/graphene airgel composite foam material according to any one of claims 5 to 7, it is characterized in that the thermoplastic polymer described in step (2) is polystyrene, polylactic acid, Polypropylene or thermoplastic polyurethane, etc. 9. according to the preparation method of the polymer/graphene airgel composite foam material according to any one of claims 5 to 7, it is characterized in that in step (2), the graphene airgel is placed in a closed environment, Vacuumize to -0.1～-0.08MPa and keep in the vacuum environment for 1～5min to fully remove the air, then place it in the solution of thermoplastic polymer, place it in a closed environment, and vacuumize to -0.1～-0.08MPa And keep it in the vacuum environment for 0.5~3h, then let it stand at normal pressure for 0.5~2h to make the thermoplastic polymer fully adhere to the three-dimensional network of graphene airgel, and finally dry to get the polymer/graphene airgel composite Material. 10. according to the preparation method of the described polymer/graphene airgel composite foam material according to any one of claims 5 to 7, it is characterized in that in step (3), the gas that passes into reactor is carbon dioxide, Nitrogen, air or water vapor; when the rapid depressurization method is used, the temperature of the reactor is controlled at 35-160°C, the pressure is 8-25MPa, and the depressurization rate is 50-80MPa/s; when the temperature-raising method is used, the temperature of the reactor is controlled at 35-50°C, pressure 8-12MPa, pressure relief rate 4-8MPa/s, oil bath temperature 80-150°C.