CN110130102A - A kind of surface modification method of carbon nanofiber - Google Patents

Abstract

The invention belongs to the field of fine chemicals, and relates to a method for modifying the surface of carbon nanofibers: (1) using low-temperature plasma to treat the carbon nanofibers; (2) using polydopamine to coat the carbon nanofibers treated in step (1) on the surface; (3) modifying the carbon nanofibers treated in step (2) with a coupling agent. The surface modification method of carbon nanofibers of the present invention enables the surface of carbon nanofibers to be coated with polydopamine, and the outer layer of polydopamine is adsorbed with a coupling agent, so that carbon nanofibers can be stably dispersed in water or organic solvents, compared with the prior art , which can improve the dispersion performance of carbon nanofibers on the basis of not destroying their own structure, and has the advantages of simple operation, no toxic reagents involved, no pollution, and good dispersion effect.

Description

A kind of surface modification method of carbon nanofiber

technical field

The invention relates to the field of fine chemicals, in particular to a method for surface modification of carbon nanofibers.

Background technique

Both theoretical and experimental studies have shown that carbon nanofiber is a high-strength, high-modulus carbon material with a carbon content of more than 95%. It has the characteristics of high specific strength, ultra-high temperature resistance, fatigue resistance, and good electrical conductivity. Therefore, carbon nanofibers have great potential as a polymer matrix and modifier. However, the dispersibility of carbon nanofibers in the polymer matrix has always been a key issue hindering their high performance. Surface treatment of carbon nanofibers is an important method to improve their dispersibility. At present, the surface treatment of carbon nanofibers can be divided into physical methods and chemical methods according to the process. The former mainly includes coating method and plasma treatment method, and the latter mainly includes surface oxidation method, electrochemical method and grafting method.

However, the commonly used surface modification methods of carbon nanofibers have some defects: the use of chemical treatment methods such as surface oxidation will bend, kink, and fracture the carbon nanofibers, which will destroy the structure and reduce the performance of carbon nanofibers. At the same time, a large number of strong oxidants are used, which makes the treated waste liquid difficult to handle, and the polluting gas generated during the reaction will cause great harm to the environment. While using a single non-covalent modification method, although it will not cause damage to the structure of carbon nanofibers and has less pollution, its dispersion effect is poorer than that of covalent modification.

SUMMARY OF THE INVENTION

In order to keep the structure of carbon nanofibers from being damaged and maintain complete performance while maintaining stable dispersibility, the invention discloses a surface modification method of carbon nanofibers, which is suitable for the surface treatment of polyacrylonitrile-based carbon fibers and pitch-based carbon fibers at the same time. .

In order to achieve the above object, the present invention adopts the following technical solutions:

A method for surface modification of carbon nanofibers, comprising the following steps:

(1) The first step of pretreatment of carbon nanofibers: the untreated carbon nanofibers are processed by a low temperature plasma instrument, the processing time is 10s-90s, and the processing power is 100W-300W. After the reaction, the treated carbon nanofibers are left for the second step treatment;

(2) Coating the carbon nanofibers processed in step (1) with polydopamine: mixing tris(hydroxymethyl)aminomethane and hydrochloric acid solution uniformly, the mass ratio of hydrochloric acid in the tris(hydroxymethyl)aminomethane and hydrochloric acid solution The ratio is 10-20:1, diluted with water, and configured into a Tris buffer solution with a solid content of 0.5% to 1.5%. The carbon nanofibers and polydopamine powder treated in step (2) are added to the Tris buffer solution and stirred under magnetic force. Stir on the mixer.

The mass ratio of carbon nanofibers to polydopamine is 1:0.1-3, and the ratio of carbon nanofibers to Tris buffer solution is 50-200 mL of buffer solution per 0.1 g of carbon nanofibers. In this step, adjusting pH is realized by adjusting the ratio of tris(hydroxymethyl)aminomethane and hydrochloric acid.

(3) Coupling and modifying the carbon nanofibers treated in step (2) with a coupling agent: dissolving the coupling agent in absolute ethanol, and each liter of absolute ethanol contains 0.025-0.15 g of the coupling agent, Stir well, after the stirring time of step (2) is 12-60h, add ethanol solution containing coupling agent, continue to stir for 1-12h, use deionized water to filter and wash until neutral, and then dry in a vacuum drying box.

The mass ratio of the carbon nanofibers to the coupling agent is 100:0.5-3, and the volume ratio of ethanol to water is 10%-90%.

After the step (2) is stirred for a period of time, the coupling agent is added for further improvement. If the step (2) is dried and then modified, the drying process will cause loss of the activity of the raw material.

Preferably, the mass ratio of tris(hydroxymethylaminomethane) to hydrochloric acid in the above step (2) is 13-15:1, diluted with water, and configured into a Tris buffer solution with a solid content of 0.5%-1%. Adjusting the ratio is to adjust the pH, which affects the formation of polydopamine.

Preferably, the coupling agent in the above step (3) is a silane coupling agent KH550, KH560, KH570 or A171. A171 is preferred; while the silane coupling agent A171 can improve the compatibility, the double bonds in it can participate in the vulcanization of methyl vinyl silicone rubber, improve the degree of cross-linking, and further improve the performance of the material.

In the present invention, plasma treatment is performed first to facilitate the subsequent combination with polydopamine, and on the other hand, by improving the binding ability between carbon fibers and polydopamine, the decomposition temperature of polydopamine is increased, and polydopamine is avoided during high-temperature processing. The degradation of the properties caused by the decomposition of carbon fiber; the introduction of hydroxyl groups on the surface of carbon fibers after plasma treatment is also conducive to the adsorption of coupling agents. There is a synergistic relationship with each other.

The present invention adopts the composite modification method of plasma treatment, polymer coating and coupling agent treatment for surface treatment of carbon nanofibers, which is pollution-free, safe and simple to operate compared with commonly used methods such as mixed acid treatment. Carbon fibers can be stably dispersed in solvents and have improved compatibility with polymers.

Description of drawings

Fig. 1 is the infrared spectrogram of the carbon nanofiber that untreated carbon nanofiber and embodiment 4 make;

In the figure, A is the infrared spectrum of the untreated carbon nanofibers, and B is the infrared spectrum of the surface-modified carbon nanofibers finally prepared in Example 4. After the comparison in the figure, it is found that the functional group changes, indicating that the surface of the modified carbon nanofibers is successfully coated and coupled.

Fig. 2 is the infrared spectrogram of untreated carbon nanofibers and the carbon nanofibers obtained in Example 5;

In the figure, a is the infrared spectrum of the untreated carbon nanofibers, and b is the infrared spectrum of the surface-modified carbon nanofibers finally prepared in Example 5. After the comparison in the figure, it is found that the functional group changes, indicating that the surface of the modified carbon nanofibers is successfully coated and coupled.

Detailed ways

The present invention is described in further detail below in conjunction with embodiment:

Example 1:

(1) The first step of pretreatment of carbon nanofibers: the untreated carbon nanofibers are processed by a low-temperature plasma instrument, the processing time is 10s, and the processing power is 100W. After the reaction, the carbon nanofibers obtained after the treatment are left for the second step treatment;

(2) Coat the carbon nanofibers treated in step (1) with polydopamine: mix 0.788 g of tris and 14.7 ml of hydrochloric acid solution with a concentration of 0.1000 mol/L, add water to dilute to 100 ml , configured into a Tris buffer solution, add 0.1g of carbon nanofibers and 0.1g of polydopamine powder into the Tris buffer solution, and stir on a magnetic stirrer;

(3) Coupling and modifying the carbon nanofibers treated in step (2) with a coupling agent: Dissolve 0.001g of silane coupling agent KH550 in 20ml of absolute ethanol, stir evenly, and wait for the stirring time of step (2) after 12h , add the ethanol solution containing the coupling agent, continue to stir for 12h, use deionized water to filter and wash to neutrality, and then dry in a vacuum drying oven.

Example 2

(1) The first step of pretreatment of carbon nanofibers: the untreated carbon nanofibers are processed by a low-temperature plasma instrument, the processing time is 20s, and the processing power is 300W. After the reaction, the carbon nanofibers obtained after the treatment are left for the second step treatment;

(2) Coat the carbon nanofibers treated in step (1) with polydopamine: mix 0.788 g of tris and 15.3 ml of hydrochloric acid solution with a concentration of 0.1000 mol/L, add water and dilute to 100 ml , configure Tris buffer solution, add 0.1g of carbon nanofibers and 0.07g of polydopamine powder into the Tris buffer solution, and stir on a magnetic stirrer;

(3) Coupling and modifying the carbon nanofibers treated in step (2) with a coupling agent: Dissolve 0.002g of silane coupling agent KH560 in 20ml of absolute ethanol, stir evenly, and wait for the stirring time of step (2) after 12h , add the ethanol solution containing the coupling agent, continue to stir for 12h, use deionized water to filter and wash to neutrality, and then dry in a vacuum drying oven.

Example 3

(1) The first step of pretreatment of carbon nanofibers: the untreated carbon nanofibers are processed by a low temperature plasma instrument, the processing time is 70s, and the processing power is 100W. After the reaction, the carbon nanofibers obtained after the treatment are left for the second step treatment;

(2) Coating the carbon nanofibers treated in step (1) with polydopamine: Mix 0.788g of tris(hydroxymethylaminomethane) and 16.7ml of hydrochloric acid solution with a concentration of 0.1000mol/L, and add water to dilute to 100ml , configure Tris buffer solution, add 0.1g of carbon nanofibers and 0.04g of polydopamine powder into the Tris buffer solution, and stir on a magnetic stirrer;

(3) Coupling and modifying the carbon nanofibers treated in step (2) with a coupling agent: Dissolve 0.002g of silane coupling agent KH570 in 20ml of absolute ethanol, stir evenly, and wait for the stirring time of step (2) after 24h , add the ethanol solution containing the coupling agent, continue to stir for 12h, use deionized water to filter and wash to neutrality, and then dry in a vacuum drying oven.

Example 4

(1) The first step of pretreatment of carbon nanofibers: the untreated carbon nanofibers are processed by a low temperature plasma instrument, the processing time is 40s, and the processing power is 200W. After the reaction, the carbon nanofibers obtained after the treatment are left for the second step treatment;

(2) Coat the carbon nanofibers treated in step (1) with polydopamine: mix 0.788 g of tris and 14.7 ml of hydrochloric acid solution with a concentration of 0.1000 mol/L, add water to dilute to 100 ml , configure Tris buffer solution, add 0.1g of carbon nanofibers and 0.01g of polydopamine powder into the Tris buffer solution, and stir on a magnetic stirrer;

(3) Coupling and modifying the carbon nanofibers treated in step (2) with a coupling agent: Dissolve 0.001 g of silane coupling agent A171 in 20 ml of absolute ethanol, stir evenly, and wait for the stirring time of step (2) after 36h , add the ethanol solution containing the coupling agent, continue to stir for 12h, use deionized water to filter and wash to neutrality, and then dry in a vacuum drying box.

Example 5

(1) The first step of pretreatment of carbon nanofibers: the untreated carbon nanofibers are processed by a low temperature plasma instrument, the processing time is 70s, and the processing power is 100W. After the reaction, the carbon nanofibers obtained after the treatment are left for the second step treatment;

(2) Coat the carbon nanofibers treated in step (1) with polydopamine: mix 0.788 g of tris and 15.3 ml of hydrochloric acid solution with a concentration of 0.1000 mol/L, add water and dilute to 100 ml , configure Tris buffer solution, add 0.1g of carbon nanofibers and 0.1g of polydopamine powder into the Tris buffer solution, and stir on a magnetic stirrer;

(3) Coupling and modifying the carbon nanofibers treated in step (2) with a coupling agent: dissolve 0.002g of silane coupling agent A171 in 20ml of absolute ethanol, stir evenly, and wait for the stirring time of step (2) after 12h , add the ethanol solution containing the coupling agent, continue to stir for 12h, use deionized water to filter and wash to neutrality, and then dry in a vacuum drying oven.

Comparative Example 1

(1) Treatment of carbon nanofibers: the untreated carbon nanofibers were processed by a low-temperature plasma instrument, the processing time was 90s, and the processing power was 300W.

Comparative Example 2

(1) Coupling modification of carbon nanofibers with coupling agent: Dissolve 0.002g of silane coupling agent A171 in 20ml of absolute ethanol, stir evenly, add carbon fiber to ethanol solution containing coupling agent, and ultrasonically evaporate for 1h. Use deionized water to filter and wash to neutrality, and then dry in a vacuum drying oven.

Comparative Example 3

(1) The first step of pretreatment of carbon nanofibers: the untreated carbon nanofibers are processed by a low temperature plasma instrument, the processing time is 70s, and the processing power is 100W. After the reaction, the carbon nanofibers obtained after the treatment are left for the second step treatment;

(2) Coat the carbon nanofibers treated in step (1) with polydopamine: mix 0.788 g of tris and 15.3 ml of hydrochloric acid solution with a concentration of 0.1000 mol/L, add water and dilute to 100 ml , configure Tris buffer solution, add 0.1g of carbon nanofibers and 0.1g of polydopamine powder to Tris buffer solution, stir on a magnetic stirrer for 24 hours, use deionized water to filter and wash to neutrality, and then put in a vacuum drying box drying.

Comparative Example 4

(1) Coating the untreated carbon nanofibers with polydopamine: Mix 0.788g of Tris and 15.3ml of hydrochloric acid solution with a concentration of 0.1000mol/L, add water to dilute to 100ml, and configure Tris Buffer solution, add 0.1g carbon nanofibers and 0.1g polydopamine powder to Tris buffer solution, stir on a magnetic stirrer

(2) Coupling and modifying the carbon nanofibers treated in step (1) with a coupling agent: Dissolve 0.002g of silane coupling agent A171 in 20ml of absolute ethanol, stir evenly, and wait for 12h of stirring time in step (2). , add the ethanol solution containing the coupling agent, continue to stir for 12h, use deionized water to filter and wash to neutrality, and then dry in a vacuum drying oven.

Comparative Example 5

(1) The first step pretreatment of carbon nanofibers: mix 10ml of ferrous sulfate solution with a concentration of 1mol/L and 12ml of a hydrogen peroxide solution with a concentration of 30wt% to obtain a hydrogen peroxide solution containing a ferrous sulfate catalyst, adjust pH=3; put 0.1 g of untreated carbon nanotubes into a hydrogen peroxide solution containing a ferrous sulfate catalyst, react under ultrasonic vibration for 4 hours, separate out carbon nanotubes by centrifugation, and use deionized water to filter and wash to neutral, and then dried in a vacuum drying oven;

(2) Coat the carbon nanofibers treated in step (1) with polydopamine: mix 0.788 g of tris and 15.3 ml of hydrochloric acid solution with a concentration of 0.1000 mol/L, add water and dilute to 100 ml , configure Tris buffer solution, add 0.1g of carbon nanofibers and 0.1g of polydopamine powder into the Tris buffer solution, and stir on a magnetic stirrer;

(3) Coupling and modifying the carbon nanofibers treated in step (2) with a coupling agent: dissolve 0.002g of silane coupling agent A171 in 20ml of absolute ethanol, stir evenly, and wait for the stirring time of step (2) after 12h , add the ethanol solution containing the coupling agent, continue to stir for 12h, use deionized water to filter and wash to neutrality, and then dry in a vacuum drying oven.

Performance Testing

The properties of Examples 1-5 and Comparative Examples were tested, and the results are shown in Table 1.

Table 1

The values of ID/ _IG in the table are obtained from _Raman spectroscopy, and the larger the value, the more defects on the surface of carbon nanofibers, and the more serious the damage to the carbon nanofiber structure.

The tensile strengths in Table 1 are all composite materials made of carbon nanofibers and silicone rubber in a mass ratio of 2/100. The tensile strength of silicone rubber without carbon fibers is 0.29. The compatibility of carbon nanofibers and silicone rubber is higher. Well, the higher the tensile strength of the composite.

Taking the above ideal embodiments according to the present invention as inspiration, and through the above description, relevant personnel can make various changes and modifications without departing from the technical idea of the present invention. The technical scope of the present invention is not limited to the contents in the specification, and the technical scope must be determined according to the scope of the claims.

Claims (7)

1. a carbon nanofiber surface modification method, is characterized in that: described method comprises the steps: (1) Low temperature plasma instrument treatment of carbon nanofibers: The untreated carbon nanofibers are processed by a low-temperature plasma instrument, the processing time is 10s to 90s, and the processing power is 100W to 300W. After the treatment, the treated carbon nanofibers are used for later use; (2) The carbon nanofibers processed in step (1) are covered with polydopamine: Mix the tris(hydroxymethyl)aminomethane and hydrochloric acid solution evenly, dilute with water, configure into Tris buffer solution, add the carbon nanofibers and polydopamine powder processed in step (1) into the Tris buffer solution, stir on a magnetic stirrer ; (3) Coupling and modifying the carbon nanofibers treated in step (2) with a coupling agent: After the stirring time of step (2) is 12-60h, add an ethanol solution containing a coupling agent, continue stirring for 1-12h, use deionized water to filter and wash to neutrality, and dry in a vacuum drying oven; The ethanol solution containing the coupling agent contains 0.025-0.15 g of the coupling agent per liter of anhydrous ethanol, and stirs evenly. 2. The method for modifying the surface of carbon nanofibers according to claim 1, wherein the mass ratio of the hydrochloric acid in the trihydroxymethylaminomethane and the hydrochloric acid solution in step (2) is 10 to 20:1, and the carbon nanofibers and the poly The mass ratio of dopamine is 1:0.1-3, and the ratio of the carbon nanofibers to the Tris buffer solution is 50-200 mL of the Tris buffer solution per 0.1 g of the carbon nanofibers. 3. The method for surface modification of carbon nanofibers according to claim 1, characterized in that: the mass ratio of tris(hydroxymethylaminomethane) and hydrochloric acid in step (2) is 13～15:1, and the solid state of the configured Tris buffer solution is 13～15:1. The content is 0.5% to 1%. 4. The method for surface modification of carbon nanofibers according to claim 2, wherein the mass ratio of the carbon nanofibers to polydopamine is 1:0.1～1, and the ratio of carbon nanofibers to Tris buffer solution is every 0.1 g of carbon nanofibers 50-150mL of buffer solution is required. 5 . The method for modifying the surface of carbon nanofibers according to claim 1 , wherein the step (3) contains 0.05-0.1 g of a coupling agent per liter of absolute ethanol. 6 . 6 . The method for surface modification of carbon nanofibers according to claim 1 , wherein the mass ratio of carbon nanofibers to coupling agent in step (3) is 100:1-2. 7 . 7 . The surface modification method of carbon nanofibers according to claim 1 , wherein the coupling agent in step (3) is a silane coupling agent KH550, KH560, KH570 or A171. 8 .