High-efficiency carbon fiber surface treatment method, product and application thereof

Abstract

The application discloses a high-efficiency carbon fiber surface treatment method and products and application thereof, and belongs to the technical field of carbon fibers for carbon paper. The application is used for solving the technical problems of large energy consumption and poor treatment effect of the existing carbon fiber surface treatment method. The application utilizes a high-frequency pulse power source to perform pulse oxidation treatment on the surface of the carbon fiber by adjusting a duty cycle parameter. Single pulse current or superposition treatment of the pulse current and fixed direct current is used to realize high-efficiency treatment of electrochemical modification of the surface of the carbon fiber. The method is time-saving, efficient, small in energy consumption and obvious in modification effect. The method can be popularized in industrial production of the carbon fiber and has a great promoting effect on industrial upgrading. The obtained carbon fiber can be used for preparing carbon paper for fuel cells and for preparing fiber resin composite materials.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of carbon fiber for carbon paper, and particularly relates to a high-efficiency carbon fiber surface treatment method, a product thereof and application. BACKGROUND

[0002] The specific strength and specific modulus of carbon fiber are more than two orders of magnitude of steel, and one of the main uses is to be compounded with resin to form carbon fiber composite material. Carbon fiber and carbon fiber composite material are widely used in high-tech fields such as aviation, aerospace and nuclear industry due to excellent mechanical and electrical properties such as high strength, high modulus, high temperature resistance, corrosion resistance, fatigue resistance, creep resistance, electrical conductivity, heat conduction and small density. With the expansion of its production scale and the reduction of its cost, carbon fiber is increasingly widely used. However, the surface of carbon fiber is inert, and if it is directly used without surface treatment, the affinity between carbon fiber and matrix material in the composite material will be weak, and the load cannot be effectively transmitted between the matrix material and the carbon fiber, so that high-performance composite material cannot be obtained. Therefore, in order to fully exert the characteristics of carbon fiber, it is necessary to perform necessary surface treatment on carbon fiber.

[0003] The surface treatment methods of carbon fiber include: (1) oxidation method, which can be further divided into gas phase oxidation method, liquid phase oxidation method and electrochemical oxidation method; (2) coating method; (3) electrochemical polymerization or grafting method; (4) plasma etching method, etc. The electrochemical oxidation method is practically applied in industry. This is because the electrochemical oxidation method has mild reaction, the reaction degree is easy to control, and the treatment effect is remarkable. In order to obtain better interface characteristics, a higher current density (20 mA / cm 2 The electrochemical treatment with high current density is beneficial to improving the interface performance of the composite material, but when the surface oxidation is performed with fixed current density, a thick diffusion layer is formed at the interface between the anode and the solution, which limits the oxidation speed. Using a larger current density not only cannot improve the oxidation speed, but also increases the oxygen evolution amount on the anode, reduces the current efficiency, causes corrosion, and then causes serious loss of the strength of the carbon fiber, so that the comprehensive mechanical properties of the composite material are not fully exerted. At the same time, the electrochemical oxidation method has problems of large energy consumption, large amount of waste liquid and large environmental pollution, so it is of great significance to develop a high-efficiency surface treatment method with small loss of carbon fiber strength and high interfacial bonding strength of resin for the production of carbon fiber and its composite material. SUMMARY

[0004] In order to overcome the shortcomings of the prior art, the present application provides a high-efficiency carbon fiber surface treatment method, a product thereof and application.

[0005] The purpose of the present application is achieved by the following technical solutions:

[0006] One of the purposes of the present application is to provide a high-efficiency carbon fiber surface treatment method, which is:

[0007] The carbon fiber surface is subjected to pulse oxidation treatment by adjusting the duty cycle and current density using a high-frequency pulse power supply.

[0008] Further limited, the duty cycle is 30-80%.

[0009] Further limited, the duty cycle is 50%.

[0010] Further limited, the pulse peak current density is 1.5-2 mA / cm 2 .

[0011] Further limited, the pulse valley current density is 0-1.0 mA / cm 2 .

[0012] Further limited, the pulse valley current density is 0.3 mA / cm 2 .

[0013] The second purpose of the present application is to provide a carbon fiber obtained by the above-mentioned surface treatment method, which has a low carboxyl content on the surface.

[0014] The third purpose of the present application is to provide the use of the carbon fiber obtained by the above-mentioned surface treatment method in the preparation of carbon paper.

[0015] The fourth purpose of the present application is to provide the use of the above-mentioned carbon paper in the field of fuel cells.

[0016] The fifth purpose of the present application is to provide the use of the carbon fiber obtained by the above-mentioned surface treatment method in the preparation of fiber composites.

[0017] The present application has the following significant effects compared with the prior art:

[0018] The present application provides a method for treating the surface of carbon fiber by pulse oxidation, which realizes high-efficiency treatment of electrochemical modification of the surface of carbon fiber by single pulse current or superposition of pulse current and fixed direct current, and has the following specific advantages:

[0019] (1) The method of the present application is time-saving, efficient, low in energy consumption, and has obvious modification effect.

[0020] (2) During the pulse oxidation surface treatment of the present invention, due to the off-time, the consumed electrolyte is used to diffuse and replenish the vicinity of the anode during this time. When the next conduction time arrives, the ion concentration near the anode is restored, reducing the concentration polarization near the anode, thus increasing the uniformity of carbon fiber treatment. In addition, during this method, the peak current of pulse oxidation can be higher than the average current, so the carbon fiber surface can be treated at a high current density in a short time.

[0021] (3) The carbon fiber surface treated by the method of the present invention has a high content of hydroxyl and carbonyl groups and a low content of carboxyl groups, which avoids the delamination of carbon layers and solves the problem of reduced interlaminar shear strength of carbon fiber resin composites caused by carbon layer delamination. However, the modified carboxyl content is not necessarily better the lower it is, but should be controlled within a suitable range. If it is too low, it will also lead to a decrease in interlaminar shear strength of carbon fiber resin composites because it cannot form chemical bonds with epoxy resin.

[0022] (4) The peak current of pulse oxidation can be much higher than the average current. By adjusting the duty cycle, the oxidation time can be adjusted. While achieving the expected effect of surface treatment, excessive oxidation of the carbon fiber surface caused by long-term high current density can be avoided.

[0023] (5) By reasonably setting parameters such as current density and pulse duty cycle, the content of functional groups (carbonyl, carboxyl, hydroxyl) on the surface of carbon fiber can be controlled to achieve the design purpose and ultimately improve the overall performance of carbon fiber.

[0024] (6) This invention does not require major modifications to the production line. It only requires replacing the DC power supply with a high-frequency pulse power supply or an auxiliary pulse power supply. Under the premise of achieving the same processing effect, the duty cycle can be reasonably set to greatly save energy consumption and processing time. It can be promoted in the carbon fiber industry and has a great role in promoting industrial upgrading.

[0025] (7) The high-frequency pulse power supply in this invention not only reduces conversion losses in terms of electrical energy conversion, but also improves the surface oxidation rate, shortens the oxidation time, reduces power consumption, and improves the quality of anodizing treatment from an electrochemical perspective. Using a high-frequency pulse power supply can achieve energy saving in both the power supply equipment and the anodizing process. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0027] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the materials, reagents, methods, and instruments used are all conventional materials, reagents, methods, and instruments in the art, and can be obtained commercially by those skilled in the art.

[0028] The terms “comprising,” “including,” “having,” “containing,” or any other variations thereof, as used in the following embodiments, are intended to cover a non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that includes the listed elements is not necessarily limited to those elements, but may include other elements not expressly listed or elements inherent to such a composition, step, method, article, or apparatus.

[0029] When a quantity, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pair of any upper or preferred value with any lower or preferred value, regardless of whether the range is disclosed individually. For example, when the range “1 to 5” is disclosed, the described range should be interpreted as including ranges “1 to 4”, “1 to 3”, “1 to 2”, “1 to 2 and 4 to 5”, “1 to 3 and 5”, etc. When numerical ranges are described herein, unless otherwise stated, the range is intended to include its endpoints and all integers and fractions within that range. In this specification and claims, range definitions may be combined and / or interchanged, unless otherwise stated, these ranges include all subranges contained therein.

[0030] The indefinite articles “a” and “an” preceding an element or component of this invention do not impose any limitation on the quantity (i.e., number of times) of the element or component. Therefore, “an” or “a” should be interpreted as including one or at least one, and the singular form of an element or component also includes the plural form, unless the quantity clearly refers only to the singular form.

[0031] In this invention, "an embodiment" or "embodiment" refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that excludes other embodiments.

[0032] The endpoints and any values ​​of the ranges disclosed in this invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0033] Example 1

[0034] The high-efficiency carbon fiber surface treatment method in this embodiment is performed according to the following steps:

[0035] Using a high-frequency pulse power supply, carbon fiber (70cm) is subjected to pulse oxidation. 2 The surface is treated with a pulse oxidation process as follows: duty cycle set to 80%, valley current density to 0, peak current to 105 mA, and peak current density to 1.5 mA / cm². 2 At this point, energy consumption is reduced by 20% while achieving the same processing effect.

[0036] Example 2

[0037] The high-efficiency carbon fiber surface treatment method in this embodiment is performed according to the following steps:

[0038] Using a high-frequency pulse power supply, carbon fiber (70cm) is subjected to pulse oxidation. 2 The surface is treated with a pulse oxidation process as follows: duty cycle set to 50%, valley current to 21mA, and valley current density to 0.3mA / cm². 2 The peak current is 105 mA, and the peak current density is 1.5 mA / cm². 2 The average current density is 0.9 mA / cm². 2 At this point, energy consumption is reduced by 40% while achieving the same processing effect.

[0039] Example 3

[0040] The high-efficiency carbon fiber surface treatment method in this embodiment is performed according to the following steps:

[0041] Using a high-frequency pulse power supply, carbon fiber (70cm) is subjected to pulse oxidation. 2 The surface is treated with a pulse oxidation process as follows: duty cycle set to 30%, valley current to 70mA, and valley current density to 1.0mA / cm². 2 The peak current is 140mA, and the peak current density is 2.0mA / cm³. 2 The average current density is 1.3 mA / cm². 2 At this point, energy consumption is reduced by 35% while achieving the same treatment effect.

[0042] The above description is merely a preferred embodiment of the present invention. These specific embodiments are different implementations based on the overall concept of the present invention, and the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A high-efficiency carbon fiber surface treatment method, characterized by, The carbon fiber surface is subjected to pulse oxidation treatment by adjusting the duty cycle and current density with a high-frequency pulse power source to realize electrochemical modification of the carbon fiber surface, the duty cycle is 30-80%, the pulse peak current density is 1.5-2 mA / cm 2 , and the pulse valley current density is 0-1.0 mA / cm 2 .

2. The method of claim 1, wherein, The duty cycle is 50%.

3. The method of claim 1, wherein, The pulse valley current density is 0.3 mA / cm 2 .

4. Carbon fibers obtained by the process according to any one of claims 1 to 3.

5. Use of the carbon fibers according to claim 4 for the production of carbon paper.

6. Use of the carbon paper produced according to claim 5 in the field of fuel cells.

7. Use of the carbon fibers according to claim 4 for the production of fiber composites.