CN104988592B - Polyvinyl alcohol/graphene composite nano fiber material and preparation method thereof - Google Patents

Abstract

The invention discloses a polyvinyl alcohol/graphene composite nano fiber material and a preparation method thereof. A modified Hummers method is adopted to prepare oxidized graphite, then a uniform polyvinyl alcohol/graphene oxide mixed solution is prepared, the mixed solution is subjected to high-energy ionizing radiation to in-situ reduce the oxidized graphene into graphene, and finally a static spinning technology is adopted to prepare the polyvinyl alcohol/graphene composite nano fiber material. The provided preparation method has the advantages that (1) a strong reducing agent is not introduced into the system; (2) graphene is evenly dispersed in the composite material, and the graphene content is higher; (3) the performance of the prepared composite nano fiber material is more uniform and the mechanical properties and electro-conductive performance are stronger; (4) the operation of the preparation method is convenient, and the preparation method is environment-friendly.

Description

Polyvinyl alcohol/graphene composite nanofiber material and preparation method thereof

technical field

The invention belongs to the field of organic polymer/inorganic composite materials, and in particular relates to polyvinyl alcohol/graphene composite nanofiber materials and a preparation method thereof.

Background technique

Graphene is a planar film composed of carbon atoms in a hexagonal honeycomb lattice with sp ² hybrid orbitals. It is a two-dimensional material with a thickness of only one carbon atom. It is a new type of single-layer sheet structure composed of carbon atoms. Materials, which have excellent electrical, thermal and mechanical properties, thus become ideal nanofillers for the preparation of functional polymer composites.

At present, the preparation of polymer/graphene composite materials mainly adopts the blending method, that is, directly mixing graphene with polymer or polymer solution, and preparing it by precipitation or hot pressing, but because the surface of graphene is inert state, the interaction with other media is extremely weak, and there is a strong van der Waals force between graphene sheets and sheets, it is easy to agglomerate, it is difficult to disperse evenly in the polymer or its solution, and the excellent properties of graphene cannot be realized. This is well reflected in composite materials, manifested by low graphene content in the composite and inhomogeneous properties of the material.

In addition, the oxidation-reduction method is currently one of the main methods for preparing graphene. This method converts graphite into graphite oxide, and then reduces and exfoliates graphite oxide into graphene. Traditional methods generally use chemical reduction to reduce graphite oxide into graphene. , but the use of strong reducing agents (such as: hydrazine hydrate) is more harmful to the environment, and it is difficult to remove in the post-treatment process, which will affect the composite material.

Based on the above-mentioned situation of prior art, the present inventor studies the preparation method of polymer/graphene composite material, and purpose is to provide the preparation of polymer/graphene composite material that avoids using reducing agent, graphene is uniformly dispersed and easy to operate The method is specifically a polyvinyl alcohol/graphene composite nanofiber material and a preparation method thereof.

Contents of the invention

In order to overcome the above-mentioned problems, the present inventor has carried out diligent research to the preparation method of polymer/graphene composite material, the result finds: can prepare the homogeneous mixture liquid of polyvinyl alcohol/graphene oxide earlier, then under the high-energy ionizing radiation The graphene oxide is reduced to graphene in situ, and the polyvinyl alcohol/graphene composite nanofiber material is prepared by electrospinning technology, avoiding the introduction of a strong reducing agent, and the graphene is uniformly dispersed in the composite material with a higher content, and the obtained The performance of the composite nanofiber material is more uniform, and the method is easy to operate and environmentally friendly.

The object of the present invention is to provide the following aspects:

(1) The preparation method of polyvinyl alcohol/graphene composite nanofiber material, the uniform mixed solution of graphene oxide and polyvinyl alcohol is under high-energy ionizing radiation, graphene oxide is reduced to graphene in situ, and then utilizes electrospinning technology Preparation of polyvinyl alcohol/graphene composite nanofiber materials.

(2) Polyvinyl alcohol/graphene composite nanofiber material, which is prepared according to the preparation method described in (1) above.

The present invention is described in detail below.

According to the first aspect of the present invention, the preparation method of polyvinyl alcohol/graphene composite nanofiber material is provided, and the uniform mixed solution of graphene oxide and polyvinyl alcohol is under high-energy ionizing radiation, and graphene oxide is reduced to graphene in situ, Then, polyvinyl alcohol/graphene composite nanofiber materials were prepared by electrospinning technology.

The method includes the following steps:

Step 1), using flake graphite as raw material, under the action of concentrated sulfuric acid, concentrated phosphoric acid, potassium permanganate and hydrogen peroxide, to obtain graphite oxide.

In a preferred embodiment according to the present invention, the improved Hummers method is used to prepare graphite oxide, specifically: flake graphite is added to the mixed solution of concentrated sulfuric acid and concentrated phosphoric acid under ice-salt bath conditions, potassium permanganate is added under stirring, Keep the reaction temperature below 5°C and stir for 1.5-4 hours, heat the reaction system to 30-35°C and stir for 20-30 hours, then add deionized water and hydrogen peroxide, continue stirring for 24-30 hours, filter and use deionized The precipitate was washed with water to obtain the graphite oxide.

Wherein, preferred mass concentration is the concentrated sulfuric acid of 98%, the concentrated phosphoric acid of 85%, the hydrogen peroxide of 25～35%; 1g described flake graphite is mixed with 4～6mL concentrated sulfuric acid, the weight ratio of described flake graphite and potassium permanganate It is 1:7～1:8; The volume ratio of described concentrated phosphoric acid and concentrated sulfuric acid is 1:8～1:10, and the volume ratio of described concentrated sulfuric acid and deionized water is 1:4～1:6, and described The volume ratio of hydrogen peroxide to concentrated sulfuric acid is 1:1-1:3; the stirring speed is 270-300 rpm.

The improved Hummers method includes two stages of low-temperature reaction (below 5°C) and medium-temperature reaction (30-35°C). In the low-temperature reaction stage, sulfuric acid molecules are mainly intercalated between graphite sheets. The deep oxidation of graphite and the hydrolysis reaction of interlayer compounds occur. The improved Hummers method provided by the present invention has sufficient low-temperature reaction intercalation, complete deep oxidation and complete hydrolysis of medium-temperature reaction, and the prepared graphite oxide has a larger interlayer distance and is easy to be stripped into Single-layer or double-layer graphene oxide lays the foundation for the preparation of single-layer or double-layer graphene oxide by ultrasonic and stirring dispersion in subsequent steps, and saves the high-temperature reaction (generally 85-95°C) stage in conventional methods , reduces energy consumption, improves safety, and is more suitable for large-scale industrial production.

In a preferred embodiment according to the present invention, the improved Hummers method provided by the invention adopts concentrated phosphoric acid to replace sodium nitrate in the conventional method, which can enhance the acidity of the system and improve oxidation efficiency. The improved Hummers method does not produce toxic gas, and the reaction system The temperature is easy to control and can be used for large-scale production of graphene oxide.

Step 2), dissolving polyvinyl alcohol in deionized water, adding the graphite oxide prepared in step 1), ultrasonically stirring and dispersing to obtain a uniform mixed solution of polyvinyl alcohol/graphene oxide.

In a preferred embodiment of the present invention, the polyvinyl alcohol has a degree of polymerization of 1700-1800 and is soluble in polar solvents such as water and ethanol.

The mass concentration of the polyvinyl alcohol in its deionized aqueous solution is 8 to 10%, the weight ratio of the graphite oxide to the polyvinyl alcohol is 1:20 to 1:250, and the graphene oxide is in the polyvinyl alcohol/ The mass concentration in the uniform mixed solution of graphene oxide is 4.0-50.0‰.

Under ultrasound and stirring, the graphite oxide is exfoliated into single-layer or double-layer graphene oxide, and the carbonyl, carboxyl, epoxy groups and other groups of graphene oxide make it have strong hydrophilicity. It has better dispersibility in water or polar solvents, so it can be uniformly dispersed in the aqueous solution of polyvinyl alcohol. During the preparation process, the addition of graphene oxide can be increased to obtain polyvinyl alcohol/polyvinyl alcohol with higher graphene content. The graphene composite nanofiber material can better improve various properties of the composite material, and because the graphene and polyvinyl alcohol are mixed more uniformly, the uniformity and stability of the performance of the composite material are improved.

Step 3), adding an oxidative radical scavenger to the mixed solution prepared in step 2), stirring and reacting under high-energy ionizing radiation, to obtain a uniform mixed solution of polyvinyl alcohol/graphene.

In a preferred embodiment according to the present invention, the high-energy ionizing radiation source is α-ray, β-ray, γ-ray, X-ray or high-speed electron flow, etc., preferably γ-ray, and the dose of the high-energy ionizing radiation is 20-80Gy /min, and the radiation time is 4 to 8 hours.

Under the above-mentioned high-energy ionizing radiation, the water in the mixed solution undergoes ionization and excitation effects, and generates species such as H free radicals with strong reducibility, hydrated electrons e ^- _aq , and simultaneously generates OH free radicals with oxidative properties. base, H ₃ O ⁺ , H ₂ , H ₂ O ₂ , HO ₂ and other species, the e ^- _aq in the above species has strong reducibility, which can reduce the graphene oxide in the mixed solution to graphene in situ and keep Evenly dispersed, but due to the presence of strong oxidizing OH free radicals in the system, it is necessary to add an oxidizing free radical scavenger to remove the oxidizing free radicals in the system, so that the system as a whole maintains a strong reducing property.

The oxidative radical scavenger is alcohol, preferably isopropanol, and the volume ratio of the polyvinyl alcohol/graphene oxide mixed solution to the oxidative radical scavenger is 1:(0.05-0.4).

In step 4), an electrospinning device is used to prepare the polyvinyl alcohol/graphene composite nanofiber material by using the mixed solution prepared in step 3) as a spinning solution.

In a preferred embodiment of the present invention, the mass concentration of polyvinyl alcohol/graphene in the spinning solution is 3.5-7.0%.

In the electrostatic spinning device, the spinning voltage is 10-28 kV, and the distance between the transmitting electrode and the receiving electrode is 10-30 cm.

At room temperature, polyvinyl alcohol/graphene composite nanofibers or nanofiber membranes are prepared by using an electrospinning device, which can be used in various fields directly or after processing.

According to the second aspect of the present invention, a polyvinyl alcohol/graphene composite nanofiber material is provided, which is prepared according to the above-mentioned preparation method of the polyvinyl alcohol/graphene composite nanofiber material.

In a preferred embodiment of the present invention, the diameter of the material is 120-400 nm, and the fiber length is more than 8 cm.

Graphene is uniformly and dispersedly distributed in the composite nanofibrous material, the uniformity and stability of the performance of the composite material are improved, the mass fraction of graphene in the material is 4-50‰, and the area of the material is The density is 70-175g/m ² , the tensile strength is 20.7-23.9MPa, the elongation at break is 13-20%, the Young's modulus of elasticity is 11.0-12.0MPa, and the electrical conductivity is 190-255μS/cm.

The beneficial effects that the present invention has include:

(1) The preparation method of the polyvinyl alcohol/graphene composite nanofiber material provided by the invention adopts high-energy ionizing radiation to reduce graphene oxide to graphene at room temperature, does not introduce strong reducing agent, and avoids reducing agent residue and high temperature reduction Destruction of organic polymers, easy operation and environmental protection;

(2) The preparation method of the polyvinyl alcohol/graphene composite nanofiber material provided by the invention utilizes the characteristics that graphene oxide has good dispersibility in water, first prepares the homogeneous mixed solution of polyvinyl alcohol/graphene oxide, and then the Graphene oxide is reduced to graphene in situ, and graphene remains uniformly dispersed in the mixed solution without agglomeration, and the performance of the prepared composite nanofiber material is more uniform;

(3) The preparation method of polyvinyl alcohol/graphene composite nanofiber material provided by the invention utilizes electrospinning technology to make polyvinyl alcohol/graphene composite nanofiber or nanofiber film, keeps the performance of composite nanomaterial uniform, And easy to operate;

(4) In the polyvinyl alcohol/graphene composite nanofiber material provided by the present invention, graphene is uniformly dispersed in polyvinyl alcohol, and the material performance is more uniform and stable, and wherein the content of graphene is higher and has stronger mechanical properties and electrical conductivity.

Description of drawings

Fig. 1 shows the XRD spectrum of polyvinyl alcohol/graphene composite nanofiber material;

Fig. 2 shows the structural diagram and fiber cross-sectional diagram of polyvinyl alcohol/graphene composite nanofiber material.

detailed description

The present invention will be further described in detail through the accompanying drawings, experimental examples and embodiments below. Through these descriptions, the features and advantages of the present invention will become more apparent.

Example

Example 1

Step 1), add 1.2g flake graphite powder into 60mL of 98% concentrated sulfuric acid, then add 6.7mL of 85% concentrated phosphoric acid, cool down to below 5°C in an ice-salt bath, start stirring slowly and add potassium permanganate, Keep the reaction temperature below 5°C and stir for 2 hours, remove the ice-salt bath, heat the reaction system to 35°C and stir for 24 hours, then add 300mL of deionized water, stir well, add 30mL of 30% hydrogen peroxide, and continue to stir for 24~ For 30 hours, filter and wash the precipitate with deionized water to obtain the graphite oxide;

Step 2), add 0.8g of polyvinyl alcohol into 9.2g of deionized water, heat at 60°C for 2 hours, then raise the temperature to 90°C for 1 hour to completely dissolve the polyvinyl alcohol, add 0.016g of Graphite oxide is dispersed by ultrasonication and stirring to obtain a uniform mixed solution of polyvinyl alcohol/graphene oxide;

Step 3), add 2mL isopropanol to the mixed solution prepared in step 2), and irradiate with a dose of 80Gy/min for 6 hours under ⁶⁰ Co gamma rays, while stirring and reacting to obtain a uniform mixed solution of polyvinyl alcohol/graphene;

Step 4), using an electrospinning device, using the mixed solution prepared in step 3) as the spinning solution, the mass concentration of polyvinyl alcohol/graphene in the spinning solution is 6.0%, and at room temperature, the spinning voltage is 18kV , spinning under the condition that the distance between the transmitting electrode and the receiving electrode is 15 cm, to obtain the polyvinyl alcohol/graphene composite nanofiber material with network structure.

Example 2

A polyvinyl alcohol/graphene composite nanofiber material with a network structure of the same size and thickness was prepared by a method similar to that of Example 1, the only difference being that 0.027 g of graphite oxide was added in step 2).

Example 3

A polyvinyl alcohol/graphene composite nanofiber material with the same size and thickness as the network structure was prepared by a method similar to that of Example 1, the only difference being that in step 3), ²⁰⁹ Poα rays were used for radiation.

Example 4

A polyvinyl alcohol/graphene composite nanofiber material with the same size and thickness as the network structure was prepared by a method similar to that of Example 1, the only difference being that ¹⁴ Cβ rays were used for irradiation in step 3).

Example 5

A polyvinyl alcohol/graphene composite nanofiber material with a network structure of the same size and thickness was prepared by a method similar to that of Example 1, the only difference being that in step 3), Cu target X-rays were used for radiation.

comparative example

Comparative example 1 solution mixing method to prepare polyvinyl alcohol/graphene composite material

Step 1), adopting the same method as Example 1 step 1) to prepare graphite oxide;

Step 2), add 0.15g of graphite oxide prepared in step 1) into 150mL of water, sonicate for 1 hour, add 0.3gKOH and 2mL of hydrazine hydrate, reflux at 98°C for 24 hours, cool to room temperature, centrifuge to separate the solid product, and water , washing with ethanol to obtain graphene;

Step 3), add 0.8g of polyvinyl alcohol into 9.2g of deionized water, heat at 60°C for 2 hours, then raise the temperature to 90°C and keep for 1 hour to completely dissolve the polyvinyl alcohol, add 0.016g of polyvinyl alcohol prepared in step 2) Graphene is dispersed by ultrasonication and stirring to obtain a mixed solution of polyvinyl alcohol/graphene;

Step 4), pour the mixed solution prepared in step 3) into the mold, take it out after standing at -25°C for 12 hours, and dry it to obtain a composite nanofiber material with the same size and thickness as the network structure in Example 1. Sheet-like polyvinyl alcohol/graphene composites.

Comparative example 2 prepares polyvinyl alcohol nanofiber material

A polyvinyl alcohol nanofiber material with the same size and thickness as the network structure was prepared by a method similar to that of Example 1, the only difference being that no graphene oxide was added.

Experimental example

Experimental example 1 X-ray diffraction experiment

Use X-ray powder crystal diffractometer (Cu target Kα ray), be 0.15406nm at λ, step width 0.02, operating voltage 40kV, test under the condition of operating current 100mA, embodiment 1 result is shown in Fig. 1, embodiment 2～ 5 The result is similar to Example 1.

Experimental Example 2 Electron Microscope Test

Adopt step 4) method, polyvinyl alcohol/graphene composite nanofiber is prepared on the receiving electrode that contains double-sided carbon conductive tape, takes off the conductive tape with above-mentioned composite nanofiber, utilizes field emission scanning electron microscope (S-4800 type ) to observe the nanofiber diameter, length, etc., the test results are shown in Figure 2.

Experimental example 3

Under the condition of 25°C and relative air humidity of 25-40%, the mechanical properties and electrical conductivity of the polyvinyl alcohol/graphene composite material were measured, and the results are shown in Table 1.

Table 1. Performance measurement results of polyvinyl alcohol/graphene composites

The present invention has been described in detail above with reference to preferred embodiments and illustrative examples. However, it should be declared that these specific embodiments are only illustrative explanations of the present invention, and do not constitute any limitation to the protection scope of the present invention. Without departing from the spirit and protection scope of the present invention, various improvements, equivalent replacements or modifications can be made to the technical contents and implementation methods of the present invention, all of which fall within the protection scope of the present invention. The protection scope of the present invention shall be determined by the appended claims.

Claims (5)

1. the preparation method of polyvinyl alcohol/graphene composite nanofiber material is characterized in that, the method comprises: Step 1), adding flake graphite into the mixture of concentrated sulfuric acid and concentrated phosphoric acid under ice-salt bath conditions, adding potassium permanganate under stirring, maintaining the reaction temperature below 5°C and stirring for 1.5 to 4 hours, heating the reaction system to Stir and react at 30-35°C for 20-30 hours, then add deionized water and hydrogen peroxide, continue to stir and react for 24-30 hours, filter and wash the precipitate to obtain graphite oxide; Step 2), dissolve polyvinyl alcohol in deionized water, add the graphite oxide prepared in step 1), ultrasonically stir and disperse to obtain a uniform mixed solution of polyvinyl alcohol/graphene oxide, and the polyvinyl alcohol is deionized The mass concentration in the ionic aqueous solution is 8-10%, the weight ratio of the graphite oxide to polyvinyl alcohol is 1:20-1:250, and the graphene oxide is in the uniform mixed solution of polyvinyl alcohol/graphene oxide The mass concentration is 4.0～50.0‰; Step 3), adding an oxidizing free radical scavenger to the mixed solution prepared in step 2), stirring and reacting under high-energy ionizing radiation, to obtain a uniform mixed solution of polyvinyl alcohol/graphene; Step 4), using an electrospinning device, using the mixed solution prepared in step 3) as a spinning solution, the mass concentration of polyvinyl alcohol/graphene in the spinning solution is 3.5 to 7.0%, and the electrospinning In the silk device, the spinning voltage is 10-28kV, the distance between the emitting electrode and the receiving electrode is 10-30cm, and the polyvinyl alcohol/graphene composite nanofiber material is obtained, and the diameter of the material is 120-400nm , the fiber length is more than 8cm, graphene is uniformly and dispersedly distributed in the composite nanofibrous material, the mass fraction of graphene in the material is 4-50‰, and the area density of the material is 70-175g/ m ² , the tensile strength is 20.7-23.9 MPa, the elongation at break is 13-20%, the Young's modulus of elasticity is 11.0-12.0 MPa, and the electrical conductivity is 190-255 μS/cm. 2. preparation method according to claim 1, is characterized in that, in step 1), Select mass concentration as 98% concentrated sulfuric acid, 85% concentrated phosphoric acid, 25-35% hydrogen peroxide, and/or 1g of the graphite flakes is mixed with 4-6mL of concentrated sulfuric acid, the weight ratio of the graphite flakes to potassium permanganate is 1:7-1:8, and/or The volume ratio of the concentrated phosphoric acid to the concentrated sulfuric acid is 1:8 to 1:10, the volume ratio of the concentrated sulfuric acid to the deionized water is 1:4 to 1:6, and the volume ratio of the hydrogen peroxide to the concentrated sulfuric acid is 1 :1～1:3, and/or The stirring speed is 270-300 rpm. 3. The preparation method according to claim 1, characterized in that, in step 2), the degree of polymerization of the polyvinyl alcohol is 1700-1800. 4. preparation method according to claim 1 is characterized in that, in step 3), The oxidative free radical scavenger is an alcohol, and/or The volume ratio of the polyvinyl alcohol/graphene oxide mixed solution to the oxidative radical scavenger is 1:(0.05～0.4), and/or The high-energy ionizing radiation source is α-ray, β-ray, γ-ray, X-ray or high-speed electron stream, and/or The dose of the high-energy ionizing radiation is 20-80Gy/min, and the radiation time is 4-8 hours. 5. The preparation method according to claim 4, characterized in that, in step 3), The oxidizing radical scavenger is isopropanol, and/or The high-energy ionizing radiation source is gamma rays.