KR20030049703A - Manufacturing process of nickel-plated carbon fibers by electroplating method - Google Patents

Abstract

PURPOSE: A method of preparing nickel-plated carbon fiber by electroplating is provided to make the carbon fiber exert higher surface energy, and when added to a resin matrix, be well adhered to the matrix with improved interlaminar shear strength, impact strength and ductility. CONSTITUTION: In a method of preparing nickel-plated carbon fiber, carbon fiber is disposed between nickel anode and cathode bar in a nickel plating electrolytic solution, and current is applied to between the nickel anode and the cathode bar. The nickel plating electrolytic solution contains 30-210g/l of NiSO4, 30-100g/l of NiCl2, and 30-40g/l of H3BO3. The current application is made at current density of 5-80A/m2 for 10-60 seconds.

Description

MANUFACTURING PROCESS OF NICKEL-PLATED CARBON FIBERS BY ELECTROPLATING METHOD}

The present invention relates to a high-strength carbon fiber electrolytic nickel-plated surface treatment on a general carbon fiber in order to increase the interfacial bonding force between the fiber and the matrix in the polymer composite material using the carbon fiber, and a method for producing the high-strength carbon fiber produced thereby.

Carbon fiber-reinforced composites, which began to develop rapidly with the development of the aviation and aerospace industry, are used today in various fields such as electric and electronic materials, civil engineering and building materials, automobiles, ships, military equipment, and sporting goods as well as in the aerospace and aerospace industry. It is one of the high-tech materials.

Carbon fiber as a reinforcing material is divided by the final heat treatment temperature. In general, as the heat treatment temperature increases, the interfacial bond strength tends to decrease. As the heat treatment temperature increases, the crystal structure becomes perfect and the surface energy decreases. Because. In addition, high-strength carbon fibers carbonized by heating to a temperature of 1000 to 1500 ° C. generally have basic functional groups such as chromene and pyrone, or carbon atom bodies are known to have Lewis basicity. . Thus, the interfacial bonding strength of carbon fibers can be improved by increasing the surface area of the fibers to provide more contact points or by increasing the physicochemical interaction between the fibers and the resin.

In order to improve such interfacial bonding force, carbon fiber surface treatment methods have been studied in the past. The surface treatment of carbon fiber can be classified into gas phase oxidation, liquid phase oxidation, and electrochemical oxidation. Gas phase oxidation (plasma treatment) has been widely used in recent years. Although the surface treatment method is performed (see paper A. Bismarck et al, J. Colloid Interface Sci. 210 , 60 (1999)), there is a disadvantage of high cost. On the other hand, the liquid oxidation method is less effective than the gas phase treatment (etching) effect and effective in improving the interfacial bonding force (see SJ Park et al, J. Colloid Interface Sci. 228 , 287 (2000)), The electrochemical treatment method is a commercially preferred process because the continuous process is possible by electrochemically oxidizing the fiber surface in an acidic or basic aqueous solution (see Korean Patent Application No. 1999-17131 by the Korea Research Institute of Chemical Research).

Conventionally, carbon fibers have been surface treated mainly by electrochemical oxidation or vapor phase oxidation using acid and basic electrolytic solutions. In this case, the carbon fiber surface itself is damaged, thereby causing a problem in that the interfacial bonding force with the matrix resin is reduced.

Accordingly, an object of the present invention is to provide a high-performance carbon fiber excellent in interfacial bonding force with the matrix resin by introducing not only oxygen functional groups but also metal nickel onto the fiber surface by performing electrolytic nickel plating treatment, which is a non-oxidative method, without using an oxidized surface treatment method. The present invention has been accomplished by knowing that such an object can be achieved by electrolytic nickel plating by applying a relatively low current density using a nickel plating solution.

1 is a view showing a surface treatment apparatus of carbon fiber by the electrolytic nickel plating method according to the present invention,

2 is a diagram showing the interlaminar shear strength of the electrolytic nickel plated carbon fiber / epoxy composite material according to Examples 1, 2, 3, and 4 of the present invention in comparison with the case of untreated carbon fiber / epoxy composite material,

3 is a diagram showing the interlaminar shear strength of the electrolytic nickel plated carbon fiber / epoxy composite material according to Examples 5, 6, and 7 of the present invention in comparison with that of the untreated carbon fiber / epoxy composite material.

* Explanation of the symbols of the main parts of the drawings

1: carbon fiber 2: nickel plating bath 3: washing bath

4: cathode roller 5: anode nickel plate 6: dryer

7: take-up motor

In order to achieve the above object, the present invention includes placing a carbon fiber between the nickel anode and the cathode rod in the nickel plating electrolyte solution, and plating the carbon fiber with nickel by applying a current between the nickel anode and the cathode rod, Provided is a method for producing nickel plated carbon fibers.

The present invention also provides a nickel plated carbon fiber produced by the above method.

Hereinafter, the present invention will be described in detail.

A feature of the method of the present invention is that the carbon fiber is nickel plated by surface treatment by a non-oxidation method, which is effective in improving the interfacial bonding force with the matrix resin with almost no etching of the carbon fiber surface and is continuous as anodization. It is a process that can be commercially useful because it is possible.

The method of the present invention improves the physical properties of the composite material by improving the bonding strength with the resin matrix by introducing carbon into the surface of the carbon fiber by electroplating the carbon fiber by placing the carbon fiber in a nickel electroplating bath and applying a voltage. It is a high performance carbon fiber manufacturing method.

The method of the present invention is performed as in the process shown in FIG. 1 using an external power source, a nickel plating bath, and a nickel plate.

In the nickel plating bath according to the present invention, the electrolytic nickel plating solution that can be used preferably contains nickel sulfate (NiSO ₄ ), nickel chloride (NiCl ₂ ) and boric acid (H ₃ BO ₃ ) as main components.

The role of nickel sulfate in the plating solution is to supply nickel ions in the bath. Although nickel chloride may be used as a source of nickel ions, it is preferable to use nickel sulfate as the main source of nickel ions because chloride increases internal stress of nickel plating. The concentration of nickel sulfate is preferably 30 to 210 g / l. The higher the nickel ion concentration in the plating bath, the higher the current density can be used, and the lower the reverse. Too high a concentration, however, will make the bath more viscous and prone to pits.

The purpose of adding nickel chloride to the electrolytic nickel plating solution used in the present invention is to supply chlorine ions in the bath and at the same time nickel ions are also supplied. The concentration of nickel chloride is preferably 30 to 100 g / l. Chlorine ions are an indispensable component for the anode dissolution of nickel, and too low a concentration does not prevent the nickel of the anode from passivating and insolubilizing, and too high a concentration increases the internal stress of the plating film, which is not preferable.

Boric acid also plays an important role as a pH buffer in nickel plating solutions. The reaction of the cathode is mainly nickel plating, but the cathode current efficiency is not 100%, but the generation of hydrogen is more or less, and consequently the hydrogen is consumed at high current density, and the pH in the cathode membrane approaching the cathode is high. Exceeding certain limits results in precipitation of nickel hydroxide. Since it is vaccinated with nickel, plating shows the phenomenon of burnout, and a normal precipitate cannot be obtained already. This phenomenon occurs when the current density exceeds a certain threshold, from which the current efficiency rapidly decreases. However, in a bath to which a typical weak acid boric acid is added, boric acid is supplied with H ⁺ even if the pH in the negative electrode film is increased, thereby preventing the increase in pH and increasing the limit current density. As such, the increase in pH in the cathode membrane is suppressed, and the pH variation of the entire bath is buffered by the presence of boric acid. Therefore, the concentration of boric acid is preferably 30 to 40 g / l. Too low a concentration will not play a pH buffer and at a concentration above 40 g / l it is not desirable because it is present as a precipitate.

In the present invention, the plating current density in the plating bath using the plating solution is preferably 5 to 80 A / m ² . If it is less than 5 A / m ² mothamyeo the concentration of the nickel ion is oxidized from the electron and the positive electrode that are emitted from the cathode not preferable because there is little metal nickel amount is generated in the carbon fiber surface with a lower relationship, exceeds 80 A / m ² Nickel ions that have been dissociated in large amounts are undesirable because they cause a decrease in interfacial bonding force with the matrix resin due to pits on the carbon fiber surface.

In the electroplating according to the present invention, the current is preferably applied for 10 to 60 seconds. Less than 10 seconds is not preferable because the amount of nickel generated on the surface of the carbon fiber is low due to the low concentration of nickel ions oxidized at the cathode and the electron emitted from the cathode, and a large amount of dissociated nickel after 60 seconds It is undesirable because the ions generate a pit on the surface of the carbon fiber, which leads to a decrease in the interfacial bonding force with the matrix resin.

Nickel-plated carbon fibers according to the present invention preferably have an amount of nickel on the fiber ranging from about 3 to about 50 mg / g.

The following examples of the present invention are intended to more clearly understand the present invention and are for illustrative purposes only and are not intended to limit the scope of the invention.

Example 1

1) Surface treatment of carbon fiber

High strength PAN-based carbon fiber TZ-307 of Korea Taekwang Industrial Co., Ltd. is used as a reinforcing material for resin, and NiSO ₄ · 6H ₂ O 50 g / l, NiCl ₂ · 6H ₂ O 40 g / l as nickel plating solution , By using a 30 g / l plating solution of H ₃ BO ₃ , electrolytic nickel plating surface treatment of the carbon fiber product at a current density of 5 A / m ² for 60 seconds according to the process shown in Figure 1, Carbon fibers were obtained.

2) Test for Composite Material

The carbon fibers surface-treated as in 1) were washed with acetone for 2 hours using a Soxhlet apparatus and dried. Subsequently, a mixture of diglycidyl ether (DGEBA, YD-128) epoxy resin of Bisphenol A of Kukdo Chemical Co., Ltd. as a resin matrix and diaminodiphenylmethane (DDM), a product of the same company as a curing agent, was used. The fibers were mixed. At this time, the epoxy resin was diluted with ethyl methyl ketone (MEK) so as to facilitate the operation of the unidirectional prepreg and the resin to be impregnated into the carbon fiber. One-way prepreg was laminated, and the resin mixture was molded by pressure and heat under vacuum atmosphere using the laminated prepreg using a thermocompressor. At this time, the curing conditions were cured for 2 hours and 30 minutes at 150 ℃ while applying a pressure of 7.35 MPa, the fiber volume% of the final cured product was adjusted to 50% (± 2%).

The chemical composition ratio of the carbon fiber surface obtained as described above is shown in Table 1, and the mechanical properties of the composite material are shown in FIG.

Example 2

The same process as in Example 1 was carried out, except that an electrolytic nickel plating solution containing 150 g / l NiSO ₄ · 6H ₂ O, 40 g / l NiCl ₂ · 6H ₂ O, and 30 g / l H ₃ BO _{3 was} prepared. The carbon fiber was subjected to electrolytic nickel plating surface treatment at a current density of 10 A / m ² for 60 seconds.

The chemical composition ratio of the carbon fiber surface thus obtained is shown in Table 1, and the mechanical properties of the composite material are shown in FIG.

Example 3

The same process as in Example 1 was conducted, except that an electrolytic nickel plating solution containing 250 g / l NiSO ₄ · 6H ₂ O, 40 g / l NiCl ₂ · 6H ₂ O, and 30 g / l H ₃ BO _{3 was} prepared. The carbon fiber was subjected to electrolytic nickel plating surface treatment at a current density of 20 A / m ² for 40 seconds.

The chemical composition ratio of the carbon fiber surface thus obtained is shown in Table 1, and the mechanical properties of the composite material are shown in FIG.

Example 4

The same process as in Example 1 was carried out, except that an electrolytic nickel plating solution comprising 350 g / l NiSO ₄ · 6H ₂ O, 40 g / l NiCl ₂ · 6H ₂ O, and 30 g / l H ₃ BO _{3 was} prepared. The carbon fiber was subjected to electrolytic nickel plating surface treatment at a current density of 40 A / m ² for 40 seconds.

The chemical composition ratio of the carbon fiber surface thus obtained is shown in Table 1, and the mechanical properties of the composite material are shown in FIG.

Example 5

Perform the same procedure as in Example 1, but using an electrolytic nickel plating solution containing 150 g / l NiSO ₄ · 6H ₂ O, 40 g / l NiCl ₂ · 6H ₂ O, and 30 g / l H ₃ BO ₃ The carbon fiber was subjected to electrolytic nickel plating surface treatment at a current density of 60 A / m ² for 20 seconds.

The chemical composition ratio of the carbon fiber surface thus obtained is shown in Table 1, and the mechanical properties of the composite material are shown in FIG.

Example 6

Perform the same as in Example 1, but using an electrolytic nickel plating solution containing 250 g / l NiSO ₄ · 6H ₂ O, 40 g / l NiCl ₂ · 6H ₂ O, and 30 g / l H ₃ BO ₃ The carbon fiber was subjected to electrolytic nickel plating surface treatment at a current density of 80 A / m ² for 20 seconds.

The chemical composition ratio of the carbon fiber surface thus obtained is shown in Table 1, and the mechanical properties of the composite material are shown in FIG.

Example 7

Perform the same as in Example 1, but using an electrolytic nickel plating solution containing 350 g / l NiSO ₄ · 6H ₂ O, 40 g / l NiCl ₂ · 6H ₂ O, and 30 g / l H ₃ BO ₃ The carbon fiber was subjected to electrolytic nickel plating surface treatment at a current density of 80 A / m ² for 10 seconds.

The chemical composition ratio of the carbon fiber surface thus obtained is shown in Table 1, and the mechanical properties of the composite material are shown in FIG.

division C _1s O _1s N _1s Ni _2p Eb (eV) AT (%) Eb (eV) AT (%) Eb (eV) AT (%) Eb (eV) AT (%) Untreated carbon fiber 284.7 68.8 532.6 25.8 400.7 0.8 857 0 Example 1 284.7 64.4 532.5 26.4 400.7 0.8 857 3.2 Example 2 284.7 63.1 532.5 27.1 400.6 0.8 857 3.8 Example 3 284.7 62.8 532.4 28.0 400.6 0.8 857 3.1 Example 4 284.6 62.0 532.6 27.9 400.3 0.8 857 4.7 Example 5 284.8 63.3 532.6 26.8 400.7 0.8 857 3.1 Example 6 284.8 62.5 532.6 27.6 400.7 0.8 857 3.7 Example 7 284.7 64.3 532.4 26.8 400.6 0.8 857 3.3 ^* AT: total area

As can be seen from Table 1, and FIGS. 2 and 3, the nickel-plated carbon fiber prepared by the method of the present invention has a high oxygen functional group formed on the surface of the fiber than the conventional carbon fiber, and at the same time, metal nickel is newly introduced to the surface. Free energy has been improved, thereby improving the interlayer shear strength (ILSS) of the composite material by about 14-35%.

The non-oxidative electrolytic nickel plating method used in the present invention is capable of continuous processing, stable processing and at the same time, the carbon fiber has a high surface energy by introducing nickel into the surface of the carbon fiber, and thus it adheres well to the matrix when added to the resin matrix. It can express excellent interlaminar shear strength.

Claims (5)

A method of manufacturing a nickel-plated carbon fiber comprising placing a carbon fiber between the nickel anode and the cathode rod in the electrolyte solution for nickel plating, and applying a current between the nickel anode and the cathode rod. The method of claim 1, The electrolytic solution for nickel plating comprises 30 to 210 g / l NiSO ₄ , 30 to 100 g / l NiCl ₂ and 30 to 40 g / l H ₃ BO ₃ . The method of claim 1, And applying a current at a current density of 5 to 80 A / m ² . The method of claim 1, And applying a current for 10 to 60 seconds. A nickel plated carbon fiber prepared according to the method of any one of claims 1 to 4.