KR100691837B1 - Composites of carbon nanofibers and polyimide, and production method thereof - Google Patents

Abstract

Provided are a carbon nanofiber and polyimide composite which is excellent in electrical property and thermal stability and is reduced in manufacturing cost, and its preparation method. The carbon nanofiber and polyimide composite comprises 1-10 parts by weight of a vapor grown carbon nanofiber; and 100 parts by weight of a polyimide produced from the poly(amic acid) which is prepared in the presence of the vapor grown carbon nanofiber. Preferably, the poly(amic acid) is prepared from an acid anhydride and a diamine compound by identical molar ratio in the presence of the vapor grown carbon nanofiber. Preferably, the vapor grown carbon nanofiber has a diameter of 10-500 nm and a length of 1-100 micrometers.

Description

Carbon nanofibers and polyimide composites and its manufacturing method {Composites of carbon nanofibers and polyimide, and production method

1 shows infrared transmission spectrum results of polyamic acid and polyimide as precursors of polyimide.

Figure 2 shows the volume resistivity value for the content of carbon nanofibers in the carbon nanofibers and polyimide composite of the present invention.

Figure 3 shows the thermal stability according to the change in the content of the carbon nanofibers in the carbon nanofibers and polyimide composite of the present invention.

The present invention relates to carbon nanofibers and polyimide composites and methods of making the same.

In general, a method of filling or dispersing a filler in a polymer matrix to improve physical properties of the polymer matrix is known.

It is known that the properties of the polymer composite formed by filling or dispersing the filler in the polymer matrix are determined not only by the inherent physical properties of the filler and the polymer matrix used, but also by the degree of dispersion of the filler.

As a method of filling or dispersing the filler in the polymer matrix, a physical method and a method using ultrasonic waves are known, but such a conventional method may cause a problem of aggregation of the filler depending on the filler used. And when the agglomeration phenomenon of the filler occurs in this way the properties of the obtained polymer composite is low heat.

Carbon black or metal powder is known as a filler used to improve the electrical properties of the polymer matrix. However, in order for the polymer composite formed by filling or dispersing carbon black or metal powder in the polymer matrix to achieve sufficient conductivity, a large amount of carbon black or metal powder had to be used. Therefore, when carbon black or metal powder is used as a filler, economy becomes a problem.

On the other hand, carbon nanofibers are widely used in many industries, such as aerospace, automotive, industrial and architectural structural materials and leisure sports.

Carbon nanofibers may be used as a filler for a polymer matrix, and thus a polymer composite formed by using carbon nanofibers as a filler for a polymer matrix adds excellent physical properties to the polymer matrix. Such polymer composites can be used in many fields, such as the fuselage of space shuttles, heat-resistant water components for aerospace, and semiconductor manufacturing processes.

In order to solve the above technical problem, the present invention is to provide a carbon nanofiber and polyimide composite having excellent physical properties such as excellent electrical properties and thermal stability.

In addition, the present invention is to provide a method for producing a carbon nanofiber and polyimide composite having excellent physical properties such as excellent electrical properties and thermal stability.

In order to solve the above technical problem, the carbon nanofibers and the polyimide composite according to one feature of the present invention are synthesized with polyamic acid in the presence of 1 to 10 parts by weight of vapor-grown carbon nanofibers, and vapor-grown carbon nanofibers. And 100 parts by weight of polyimide produced from the polyamic acid.

According to another aspect of the present invention, a method of preparing a carbon nanofiber and a polyimide composite may include reacting a solution including gaseous growth carbon nanofibers, an acid anhydride, and a diamine compound to synthesize a polyamic acid solution, and gaseous growth carbon nanofibers. In the polyamic acid solution comprising a, by converting the polyamic acid into a polyimide by thermal imidization.

The carbon nanofibers and polyimide composites according to the present invention are formed by in-situ polymerization in which polyamic acid is synthesized in the presence of carbon nanofibers and converts polyamic acid to polyimide.

The carbon nanofibers used in the present invention are preferably carbon nanofibers (hereinafter, referred to as 'weather grown carbon nanofibers') grown by thermal chemical vapor deposition. The vapor-grown carbon nanofibers have a high aspect ratio, and have a structure in which carbon atoms are arranged in a ring shape around the carbon nanofibers, and thus are very chemically stable.

When vapor-grown carbon nanofibers are used as fillers for polymers, they are superior to other metals in terms of specific strength, thermal expansion, maze, and corrosion resistance. In addition, vapor-grown carbon nanofibers are more advantageous than carbon nanotubes produced by other methods in terms of economical aspects.

The content of the vapor-grown carbon nanofibers in the present invention is preferably used in 1 to 10 parts by weight based on 100 parts by weight of polyimide.

If the content of the gaseous growth carbon nanofibers is less than 1 part by weight with respect to 100 parts by weight of polyimide, the content of the gaseous growth carbon nanofibers is too small to achieve desired electrical properties and the like. On the other hand, when the content of the gaseous growth carbon nanofibers exceeds 10 parts by weight with respect to 100 parts by weight of polyimide, it is difficult to uniformly disperse the gaseous growth carbon nanofibers inside the polyimide, resulting in a higher viscosity of the resulting composite film There is a problem that is difficult to manufacture.

In the present invention, the vapor-grown carbon nanofibers preferably have an average diameter of 10 to 500 nm and a length of 1 to 100 m.

The in-situ polymerization of the carbon nanofibers and the polyimide composite according to the present invention will be described in detail as follows.

The polyamic acid is synthesized by reacting an acid anhydride and a diamine compound in a solvent in the presence of vapor-grown carbon nanofibers, and thermally imidizing the polyamic acid by drying and heat-curing the polyamic acid including the thus-formed vapor-grown carbon nanofibers. To produce carbon nanofibers and polyimide composites. The carbon nanofibers and the polyimide composite thus prepared are uniformly dispersed or filled with vapor-grown carbon nanofibers inside the polyimide to simultaneously improve electrical properties and thermal stability.

Acid anhydrides that can be used to synthesize the polyamic acid in the present invention are 3,3,4,4-benzophenonetetracarboxylic dianhydride (hereinafter referred to as 'BTDA'), pyromellitic dianhydride ( pyromellitic dianhydride), diphenyl ether-3,3 ', 4,4'-tetracarboxylic dianhydride, 4,4'-oxydiphthalic anhydride and the like are preferably used.

Diamine compounds that can be used to synthesize the polyamic acid in the present invention is 4,4-oxydianiline (hereinafter referred to as 'ODA'), 4,4'-diaminodiphenyl ether, 2,6-bis ( 3-aminophenoxy) phenozonitrile and the like are preferably used.

Acid anhydrides and diamine compounds in the present invention are preferably used in the same molar content.

In the present invention, in addition to carbon nanofibers, nickel powder, gold powder, copper powder, metal alloy powder, carbon powder, graphite powder, carbon black, etc. may be used as the filler. However, those having an average diameter of 10 to 500 nm and having a length of 1 to 100 μm are preferably used for vapor-grown carbon nanofibers, having an average diameter of 100 to 200 nm, and having a length of 10 to 20 μm and a tensile strength of Vapor-grown carbon nanofibers having 1 to 3 GPa are most preferably used.

The solvent for dissolving the diamine compound and the acid anhydride in the present invention is N, N-dimethylformimide (DMF), N, N-dimethylacetimide (DMAC), dimethyl sulfoxide (DMSO), and N-methyl-1 -Pyrrolidinone (NMP) or the like is preferably used. However, NMP having high solubility of BTDA and ODA at room temperature is most preferably used.

The polyamic acid solution, which is a precursor of the polyimide in the present invention, is synthesized by condensation polymerization of a diamine compound and an acid anhydride in the presence of gaseous growth carbon nanofibers.

The polyamic acid solution thus synthesized is adjusted to 1 to 50% by weight depending on the molecular weight and viscosity of the produced polyamic acid to facilitate casting. Here, solid mass content means the mass content of a polyamic-acid component. If the solid mass fraction in the polyamic acid solution exceeds 1 to 50% by weight or less, a problem arises that it is not easy to control during casting.

After casting the polyamic acid solution, the solvent present is preferably removed by heating to a temperature above the boiling point of the solvent for 24 hours in a vacuum oven before curing the polyamic acid in the solution to polyimide. At this time, when the solvent is not completely removed, the solvent generates bubbles in the carbon nanofibers and polyimide composites, and these bubbles increase the volume resistance of the carbon nanofibers and the polyimide composites.

The cast polyamic acid is then heated to cause a thermal imidization reaction to yield a polyimide, wherein the temperature increase rate is preferably 0.1 to 5 ° C / min. And it is preferable to make cooling rate after reaction into 0.1-5 degreeC / min. These heating rates and cooling rates will affect the stability of the carbon nanofibers and polyimide composites and the solvent resistance, mechanical and electrical properties. Therefore, the reaction is carried out with sufficient time so that complete imidization of polyamic acid to polyimide can be achieved.

Hereinafter, the carbon nanofibers and the polyimide composite according to the present invention will be described in detail with reference to the following examples and comparative examples, but the scope of protection of the present invention is not limited to these examples.

Example 1

 1 g of vapor-grown carbon nanofibers (Showa Dnnko, diameter: 100-200 nm, length: 10-20 μm, tensile strength: 1-3 Gpa, content: 99.9%) was dried in a vacuum oven for 24 hours to remove moisture and residual solvent. Was removed.

After purging the three-necked flask with nitrogen, 6.493 g of purified 4,4-oxydianiline (ODA) and prepared vapor-grown carbon nanofibers were added, and 4,4-oxydianiline (ODA) was added at room temperature to N-methyl-. After completely dissolving in 50 ml of 1-pyrrolidinone (NMP), 10.45 g of the same mole of 3,3,4,4-benzophenonetetracarboxylic dianhydride (BTDA) was added to react for about 24 hours to completely dissolve. The polyamic acid solution to which vapor-grown carbon nanofibers were added was synthesized.

The solid mass fraction of the synthesized polyamic acid solution was adjusted to 18% by weight to facilitate casting on the glass plate.

The polyamic acid solution thus synthesized was cast on the glass plate so that the thickness of the final thin film was 50 μm, and the solvent was evaporated by heating at 80 ° C. for 24 hours.

Thereafter, the synthesized polyamic acid was cured at 110 ° C., 170 ° C., 210 ° C., and 250 ° C. for 1 hour to obtain 17.2 g of the final carbon nanofiber and polyimide composite.

Example  2

3 g of vapor-grown carbon nanofibers (Showa Dnnko, diameter: 100-200 nm, length: 10-20 μm, tensile strength: 1-3 GPa) was dried in a vacuum oven for 24 hours to remove moisture and residual solvent.

After purging the three-necked flask with nitrogen, purified 4,4-oxydianiline (ODA) and the prepared vapor-grown carbon nanofibers were added, and 4,4-oxydianiline (ODA) was added at room temperature to N-methyl-1-. After completely dissolved in pyrrolidinone (NMP), the same molar 3,3,4,4-benzophenonetetracarboxylic dianhydride (BTDA) was added and reacted for about 24 hours to completely dissolve the gaseous growth carbon. A polyamic acid solution to which nanofibers were added was synthesized.

The solid mass fraction of the synthesized polyamic acid solution was adjusted to 1 to 50% by weight to facilitate casting on the glass plate.

The polyamic acid solution thus synthesized was cast on the glass plate so that the thickness of the final thin film was 50 μm, and the solvent was evaporated by heating at 80 ° C. for 24 hours.

Thereafter, the synthesized polyamic acid was cured at 110 ° C., 170 ° C., 210 ° C., and 250 ° C. for 1 hour to obtain 19.3 g of carbon nanofibers and polyimide composites.

Example  3

5 g of vapor-grown carbon nanofibers (Showa Dnnko, diameter: 100-200 nm, length: 10-20 μm, tensile strength: 1-3 GPa) were dried in a vacuum oven for 24 hours to remove moisture and residual solvent.

After purging the three-necked flask with nitrogen, purified 4,4-oxydianiline (ODA) and the prepared vapor-grown carbon nanofibers were added, and 4,4-oxydianiline (ODA) was added at room temperature to N-methyl-1-. After completely dissolved in pyrrolidinone (NMP), the same molar 3,3,4,4-benzophenonetetracarboxylic dianhydride (BTDA) was added and reacted for about 24 hours to completely dissolve it. A polyamic acid solution to which nanofibers were added was synthesized.

The solid mass fraction of the synthesized polyamic acid solution was adjusted to 1 to 50% by weight to facilitate casting on the glass plate.

The polyamic acid solution thus synthesized was cast on a glass plate such that the thickness of the final thin film was 50 μm, and then evaporated by heating at 80 ° C. for 24 hours.

Thereafter, the synthesized polyamic acid was cured at 110 ° C., 170 ° C., 210 ° C., and 250 ° C. for 1 hour to obtain 21.1 g of the final carbon nanofibers and polyimide composite.

Example  4

10 g of vapor-grown carbon nanofibers (Showa Dnnko, diameter: 100-200 nm, length: 10-20 μm, tensile strength: 1-3 GPa) was dried in a vacuum oven for 24 hours to remove moisture and residual solvent.

After purging the three-necked flask with nitrogen, purified 4,4-oxydianiline (ODA) and the prepared vapor-grown carbon nanofibers were added, and 4,4-oxydianiline (ODA) was added at room temperature to N-methyl-1-. After completely dissolving in pyrrolidinone (NMP), the same molar 3,3,4,4-benzophenonetetracarboxylic dianhydride (BTDA) is reacted for about 24 hours to completely dissolve and vapor-grown carbon nanofibers. The polyamic acid solution added was synthesized.

The solid mass fraction of the synthesized polyamic acid solution was adjusted to 1 to 50% by weight to facilitate casting on the glass plate.

The polyamic acid solution thus synthesized was cast on the glass plate so that the thickness of the final thin film was 50 μm, and the solvent was evaporated by heating at 80 ° C. for 24 hours.

Thereafter, the synthesized polyamic acid was cured at 110 ° C., 170 ° C., 210 ° C., and 250 ° C. for 1 hour, respectively, to obtain 26.4 g of the final carbon nanofiber and polyimide composite.

Comparative example  One

After purging the three-necked flask with nitrogen, purified 4,4-oxydianiline (ODA) was completely purified at room temperature with 4,4-oxydianiline (ODA) in N-methyl-1-pyrrolidinone (NMP). After dissolution, the same mole of 3,3,4,4-benzophenonetetracarboxylic dianhydride (BTDA) was reacted for about 24 hours to completely dissolve to synthesize polyamic acid.

The whole polymerization process was performed in nitrogen atmosphere. The solid mass fraction of the synthesized polyamic acid solution was adjusted to 1 to 50% by weight to facilitate casting on the glass plate.

The properties of the carbon nanofibers and polyimide composites synthesized in Examples and Comparative Examples of the present invention were measured by the following method.

1. Measurement of the degree of imidization of carbon nanofiber and polyimide composite film

In the present invention, Comparative Example 1 was measured using a polyamic acid solution and a polyimide film for the results of clear ring measurement of polyimidization of polyamic acid.

Specifically, the polyamic acid solution of the Comparative Example 1 and the polyimide film in the infrared spectrum spectrum FT-IR (MIDAC corporation, M-2000) spectrum through the spectroscopic analysis method in the wave number (wave number) 4000 to 400 cm ^-1 range 4 The number of scans was 16 at cm ^-1 resolution.

Figure 1 shows the results of the infrared transmission spectrum of the polyamic acid solution and cured polyimide film of Comparative Example 1.

As can be seen in Figure 1, polyamic acid, a precursor of polyimide, observed N-H and O-H peaks, while polyimide disappeared its peaks and C = O and C-N peaks.

2. Measurement of electrical characteristics

The electrical characteristics were measured using a volume resistor (MITSUBISHI Chemical Co., MCP-T610). The volume resistivity is measured by cutting the specimen into 10Ⅹ50Ⅹ2 mm ^3, and then placing the four-pin electrode on the specimen in a straight line by the four probe method. It was obtained.

3. Thermal stability measurement

In order to measure the thermal stability of carbon nanofibers and polyimide composites, a thermogravimetric analyzer (TA Instruments, TGA Q500) was used to increase the temperature from 5 ° C./min to 850 ° C. under a nitrogen atmosphere. It was.

4. Determination of Crystallization Structure and Dispersion of Carbon Nanofibers and Polyimide Composites

X-ray diffraction (XRD) was measured on the carbon nanofibers and the polyimide composite according to the content of the carbon nanofibers to determine the crystallization structure of the carbon nanofibers and the polyimide composite. 2θ was performed from 3 to 60 degrees using a Rigaku D / MAX-2200V X-ray diffractometer with an X-ray diffractometer (XRD) for X-ray diffraction measurement.

In addition, it was measured at a magnification of 10000 times using a scanning electron microscope (SEM, Hitachi) to measure the dispersion degree of carbon nanofibers and polyimide composite.

Using the carbon nanofibers and polyimide composite prepared according to Examples 1 to 4, and the polyimide prepared according to Comparative Example 1, the volume resistivity according to the change in the content of carbon nanofibers was measured according to the electrical property measurement method. 2 and Table 1 below.

As can be seen in Figure 2 and Table 1, the volume resistivity values of the carbon nanofibers and polyimide composites of Examples 1 to 4 is 10 ^-2 to 10 ⁷ Ωcm, all of them have electrical properties compared to the polyimide of the comparative example Significantly improved.

In addition, from the volume resistivity values of the carbon nanofibers and polyimide composites of Examples 1 to 4, it was confirmed that as the content of the carbon nanofibers in the carbon nanofibers and polyimide composites increased, the volume resistivity value was significantly lowered to significantly improve the electrical properties. It was.

Using the carbon nanofibers and polyimide composite prepared according to Examples 1 to 4 and the polyimide prepared according to Comparative Example 1, the thermal stability according to the change of the content of carbon nanofibers was measured according to the thermal stability measurement method. As shown.

As can be seen in Figure 3, the carbon nanofibers and polyimide composite is the temperature at which the maximum weight loss occurs more than 500 ℃, it was confirmed that the thermal stability increases as the content of the carbon nanofibers increases.

Carbon nanofibers and polyimide composites according to the content change of the carbon nanofibers by measuring the X-ray diffraction of the carbon nanofibers and polyimide composites prepared according to Examples 1 to 4 and the polyimide prepared according to Comparative Example 1 The change in crystallization structure is shown in FIG. 4.

As can be seen in Figure 4, in the case of Examples 1 to 4, unlike the comparative example, it can be seen that it has a crystalline peak near 26 degrees corresponding to the carbon nanofibers. From FIG. 4, it can be seen that the peak size increases in the order of Example 4 in Example 1 having a high content of carbon nanofibers. That is, it can be seen that the degree of crystallization increases as the carbon nanofiber content increases in the carbon nanofiber and polyimide composite.

In addition, the photograph of the scanning electron microscope (SEM) of the carbon nanofibers and the polyimide composite of Comparative Example, Example 2 and Example 3 is shown in FIG.

As can be seen in Figure 5, in the case of Example 2, the content of the carbon nanofibers is 3 parts by weight, as shown in the central region of the photo, the carbon nanofibers are not present locally, but only the region of the matrix polymer is observed, carbon nano In the case of Example 3 having a fiber content of 5 parts by weight, it was confirmed that the carbon nanofibers were evenly distributed throughout. That is, when the content of the carbon nanofibers is properly contained, it can be seen that the degree of dispersion in the polyimide matrix of the carbon nanofibers is optimized. As the carbon nanofibers, which are charge transfer channels, are properly dispersed, the electrical properties of the carbon nanofibers and the polyimide composite are excellent.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and various modifications and changes can be made within the scope of the claims and the detailed description of the invention and the accompanying drawings. Naturally, it belongs to

As described above, the carbon nanofibers and polyimide composites prepared according to the present invention achieved excellent electrical properties and thermal stability even when a small amount of carbon nanofibers were added as a filler.

In particular, the present invention uses the same container polymerization method of preparing a polyamic acid, which is a precursor of polyimide in the presence of carbon nanofibers, to produce polyimide therefrom, whereby the degree of dispersion of the carbon nanofibers in the formed polyimide It was superior to other methods such as the method used, and excellent mixing of the carbon nanofibers and the polyimide resin was achieved.

In addition, the vapor-grown carbon nanofibers used as the filler in the present invention is economical compared to metal powder, carbon black, or carbon nanotubes, etc., which can greatly contribute to reducing the manufacturing cost and improving the performance of the polyimide composite.

Claims (18)

1 to 10 parts by weight of vapor-grown carbon nanofibers; And 100 parts by weight of polyimide synthesized from the polyamic acid in the presence of the vapor-grown carbon nanofibers; Carbon nanofibers and polyimide composites comprising a. The method of claim 1, Wherein said polyamic acid is synthesized from equimolar acid anhydride and a diamine compound in the presence of said vapor grown carbon nanofibers. The method of claim 2, The acid anhydride is 3,3,4,4-benzophenonetetracarboxylic dianhydride, pyromellitic dianhydride, diphenylether-3,3 ', 4,4'-tetracarboxylic dianhydride, and The carbon nanofiber and polyimide composite of claim 4, wherein the carbon nanofibers and polyimide composites are selected from the group consisting of 4,4'-oxydiphthalic anhydride. The method of claim 2, The diamine compound is selected from the group consisting of 4,4-oxydianiline, 4,4'-diaminodiphenyl ether, and 2,6-bis (3-aminophenoxy) phenozonitrile. Nanofiber and Polyimide Composites. The method of claim 2, Wherein said acid anhydride is 3,3,4,4-benzophenonetetracarboxylic dianhydride and said diamine compound is 4,4-oxydianiline. The method according to any one of claims 1 to 5, Wherein said vapor-grown carbon nanofibers have a diameter of 10-500 nm and a length of 1 to 100 μm. The method of claim 6, The carbon nanofiber and polyimide composite having a volume resistance value of the carbon nanofiber and polyimide composite is 10 ⁻² to 10 ⁷ Ωcm. The method of claim 6, The carbon nanofiber and polyimide composite having a temperature of at least 500 ° C. at which a maximum weight loss of the carbon nanofiber and polyimide composite occurs. Reacting a solution comprising vapor-grown carbon nanofibers, an acid anhydride and a diamine compound to synthesize a polyamic acid solution; And In the polyamic acid solution containing the vapor-grown carbon nanofibers, thermally imidating the polyamic acid to convert it to polyimide; Method of producing a carbon nanofiber and polyimide composite comprising a. The method of claim 9, Method for producing the carbon nanofibers and polyimide composite, characterized in that the vapor-grown carbon nanofibers are contained in 1 to 10 parts by weight based on 100 parts by weight of the polyimide. The method of claim 9, The acid anhydride is 3,3,4,4-benzophenonetetracarboxylic dianhydride, pyromellitic dianhydride, diphenylether-3,3 ', 4,4'-tetracarboxylic dianhydride, and A method for producing the carbon nanofibers and polyimide composites, characterized in that it is selected from the group consisting of 4,4'-oxydiphthalic anhydride. The method of claim 9, The diamine compound is selected from the group consisting of 4,4-oxydianiline, 4,4'-diaminodiphenyl ether, and 2,6-bis (3-aminophenoxy) phenozonitrile. Method of Making Nanofiber and Polyimide Composites. The method of claim 9, The acid anhydride is 3,3,4,4-benzophenonetetracarboxylic dianhydride, and the diamine compound is 4,4-oxydianiline, the method of producing the carbon nanofibers and polyimide composite. The method of claim 9, Casting the polyamic acid solution on a predetermined substrate. The method of claim 14, Method for producing the carbon nanofibers and polyimide composite, characterized in that the solid mass fraction of the polyamic acid solution is 1 to 50% by weight. The method of claim 14, Drying the solvent in the polyamic acid solution cast on the substrate to completely remove the carbon nanofiber and polyimide composite. The method according to any one of claims 9 to 16, The vapor-grown carbon nanofibers have a diameter of 10-500 nm and a length of 1 to 100 μm, wherein the carbon nanofibers and polyimide composites are produced. The method of claim 17, The vapor-grown carbon nanofibers have a diameter of 100-200 nm and a length of 10 to 20 μm, characterized in that the carbon nanofibers and polyimide composite production method.

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