CN110761067A - A method and device for continuous treatment of carbon fiber surface based on atmospheric pressure DBD discharge - Google Patents

Abstract

The invention discloses a carbon fiber surface continuous treatment method and device based on atmospheric pressure DBD discharge, and relates to the technical field of plasma surface engineering. The device provided by the present invention includes: a gas supply system, a plasma generation system and a carbon fiber conveying system; the gas supply system includes a gas source and a mixed gas cavity, and the plasma generation system includes an excitation power supply, a high-voltage electrode, a ground electrode, an insulating medium and Semi-sealed cavity, carbon fiber conveying system includes driving device and sending/discharging device. The carbon fiber plasma surface continuous treatment method is to continuously transport the carbon fiber through the transmission system into the DBD discharge plasma working chamber under the preset atmospheric environment medium, and perform plasma treatment to realize the surface roughening of the carbon fiber, and at the same time generate active groups on the surface, Thereby, the bonding strength of the carbon fiber inside the composite material and the resin matrix is improved.

Description

A method and device for continuous treatment of carbon fiber surface based on atmospheric pressure DBD discharge

technical field

The invention belongs to the field of surface engineering, and relates to a continuous treatment method and device for carbon fiber surface based on atmospheric pressure DBD discharge. More specifically, it relates to surface modification of reinforcing fibers in composite materials, so as to improve the bonding force between the reinforcing fibers and the matrix, and improve the strength of the composite materials.

Background technique

Composite materials have been widely used in many fields such as aerospace, automobile, energy and power due to their remarkable advantages such as high specific strength, high specific stiffness and good corrosion resistance. In the field of aerospace, composite materials are one of the four major structural materials. The amount of composite materials in military and civil aviation is gradually increasing. To a certain extent, the amount of composite materials represents the advanced level of aircraft.

As a reinforcing fiber, carbon fiber has received extensive attention in the field of composite materials due to its excellent tensile strength, fatigue strength, etc., and its light weight. The interface between the carbon fiber and the matrix is a very important stress transfer surface of the composite material, and its properties are directly related to the performance of the composite material. The surface of carbon fiber is smooth, and like a matrix such as resin, the surface is chemically inert, which leads to insufficient bonding force between carbon fiber and matrix, and even "kiss bond" (Kiss bond, only contact but no defects, geometrically meets the requirements but cannot transmit load) , Weak bond (weak bond bond strength is weak, less than 20% of the normal bond strength) and other issues, which ultimately affect the overall performance of the composite material and seriously threaten the safety of components. Therefore, it is urgent to develop carbon fiber surface treatment technology to improve its surface hydrophilicity and chemical activity, while roughening the surface and increasing its contact area with the substrate, thereby improving the bonding force between carbon fiber and the substrate, and ensuring the safe use of composite materials.

There are two main methods of carbon fiber surface modification: physical method and chemical method. Chemical modification is to introduce active groups such as amino groups, carboxyl groups, and hydroxyl groups on the fiber surface through chemical reactions, thereby improving the bonding strength between the fiber and the matrix; Through chemical bond interruption and reorganization, active groups such as hydroxyl and carbonyl are introduced, and the surface morphology of the fiber is changed at the same time, thereby improving the bonding strength. Plasma surface treatment is a kind of physical modification method.

At present, there are many ways to generate plasma, and DBD discharge, glow discharge, radio frequency inductively coupled discharge, etc. are used more in fiber surface treatment. Since carbon fiber is a conductive material, plasma treatment in an air environment is prone to surface ablation. In order to obtain a good surface state, most of the existing plasma treatment is carried out in a vacuum or a closed cavity, and the equipment requirements are relatively high. And it is difficult to achieve large-scale automated processing.

Aiming at reinforced carbon fibers for composite materials, the present invention proposes a continuous treatment method and device for carbon fiber surfaces based on atmospheric pressure DBD discharge, which can realize DBD discharge plasma treatment of carbon fibers in an atmospheric environment. The device of the invention has a simple structure and can realize carbon fiber Large-scale automatic processing, suitable for industrialization promotion. The application of the invention can greatly improve the bonding strength between the carbon fiber and the matrix, thereby increasing the service life of the composite material, and has important military value and significant economic benefit.

SUMMARY OF THE INVENTION

The purpose of the present invention is to propose a method and device for continuous treatment of carbon fiber surface based on atmospheric pressure DBD discharge, in order to solve the problem that the lack of equipment for carbon fiber surface treatment in the prior art has low efficiency, can only be carried out in a vacuum or sub-vacuum environment, and does not economic issues.

In order to achieve the above purpose, the present invention proposes a continuous treatment method for carbon fiber surface based on atmospheric pressure DBD discharge, the method comprising:

Step 1. Control the flow rate of each gas cylinder according to the preset atmosphere environment, open the corresponding gas cylinder valve, make it mix and let the mixed gas fill the entire discharge chamber to ensure that the discharge medium is a preset atmosphere environment and the pressure is high. is atmospheric pressure.

Step 2. In the atmospheric environment of atmospheric pressure obtained in step 1, the electrodes are connected to a high-frequency DC power supply, and a voltage is applied to the two poles of the medium to form a uniform and stable plasma, and the probe is used to detect the plasma at the center of the generated plasma area. Plasma density was tested.

Step 3: Set the motor speed according to the length of the discharge medium and the treatment time, so that the carbon fiber continuously passes through the plasma area obtained in the second step at a certain speed, that is, the surface treatment of the carbon fiber is completed.

The atmosphere described in step 1 is a mixed gas containing functional gas and inert gas, wherein the functional gas can be oxygen, nitrogen, nitrogen dioxide, oxygen-containing gas, etc., and the inert gas is generally helium, argon, etc. The selection and flow control of the functional gas should be determined according to the preset atmosphere environment, that is, it needs to be determined according to the expected surface active groups after the continuous treatment of the fiber surface.

In step 2, before the power is turned on to generate plasma, the plasma region is purged with a mixed gas to ensure that the entire plasma region is filled with the mixed gas when the plasma is generated; the voltage applied during plasma treatment is 10-20 kV. The probe is used to monitor and measure the plasma density at the center of the plasma region under different discharge parameters.

The carbon fiber described in step 3 should be subjected to surface degumming treatment before treatment, and the passing speed in the plasma zone should be adjustable within the range of 0-0.1 m/s.

In order to achieve the above object, the present invention also proposes a continuous treatment device for carbon fiber surface based on atmospheric pressure DBD discharge, which includes three parts: a gas supply system, a plasma generation system, a plasma testing system and a carbon fiber conveying system. The gas supply system should include a gas source and a mixed gas chamber. The gas source should include different types of inert gas, oxygen-containing gas or other gases. Each gas source includes an on-off regulating valve, a pressure gauge and a flow meter. ; The mixed gas chamber should contain multiple air inlets, at least four, to meet the mixing of different types of gases. The plasma generation system includes an excitation power source, a high-voltage electrode, a ground electrode, an insulating medium and a semi-hermetic cavity, of which the first four constitute a dielectric barrier discharge (DBD) device. The carbon fiber conveying system includes a driving device, a wire take-up machine, a crimping wheel and a pay-off machine. At least four crimping wheels are required, two of which are placed at both ends of the plasma to fix the carbon fiber position and ensure that the carbon fiber can be Smoothly pass through the plasma reaction chamber; the other two pressure rollers are used to control the carbon fiber orientation. The carbon fiber released by the pay-off machine passes through the wire press wheel, passes through the plasma reaction chamber, and is recovered by the wire take-up machine after passing through the wire press wheel. The wire take-up machine is driven by the driving device. The machine pays off the line to realize the automation of the whole process of carbon fiber plasma treatment.

Further, in the described carbon fiber surface continuous treatment device based on atmospheric pressure DBD discharge, the gas source is a gas cylinder containing different gases, and each gas cylinder is equipped with an on-off regulating valve, a pressure gauge and a Barometer.

Further, the material of the semi-closed cavity is insulating material, and the left cavity is designed with different external dimensions according to the requirements to ensure that the crimping wheel can be easily installed, and at least the front and rear sides are transparent and visible, and the left side passes through the inlet. The air port is sealed with the mixed gas cavity, and the right side of the cavity should completely contain the entire DBD device; in addition, a small hole on the left side of the cavity only needs to ensure that the carbon fiber can be exported, and the position of the small hole is flush with the carbon fiber position , make sure that the carbon fiber comes out of this small hole.

Further, there is no size limit for the crimping wheel, but the installation positions of the two crimping wheels located on both sides of the plasma reaction chamber should ensure that the carbon fiber passing through the plasma area is located at the zero potential position in the center, so as to avoid the carbon fiber The conductive surface is ablated; other crimping rollers have no clear position limit, but function to keep the carbon fiber taut at all times during processing.

Further, in the above-mentioned continuous treatment device for carbon fiber surface based on atmospheric pressure DBD discharge, the materials of the wire crimping wheel, the wire take-up machine, the wire pay-off machine and the shaft wheels thereof are all conductive materials.

Further, in the described carbon fiber surface continuous treatment device based on atmospheric pressure DBD discharge, the driving device (6) should include a programmable automation controller and a stepper/servo motor, and according to the movement rate requirements , Program the controller to achieve precise control of the stepper/servo motor.

Compared with the prior art, the beneficial effects of the present invention are mainly reflected in: by setting an air supply system, the DBD discharge can be made in a preset atmosphere environment and carried out in an air environment; by setting a fiber conveying system, carbon fiber automation can be realized Large-scale treatment; in addition, the carbon fiber surface is treated with a DBD discharge plasma treatment device, and the fiber surface is etched by plasma to generate active groups on the surface while roughening the surface, so as to improve the bonding strength of the carbon fiber and the matrix. , so as to improve the performance of composite materials. The carbon fiber surface continuous treatment device provided by the invention solves the problem that the carbon fiber DBD discharge plasma treatment can only be performed in a vacuum or sub-vacuum environment.

Description of drawings

Fig. 1 is a kind of carbon fiber surface plasma continuous treatment device based on atmospheric pressure DBD discharge of the present invention;

Fig. 2 is a DBD discharge plasma generating device of a carbon fiber surface plasma continuous processing device based on atmospheric pressure DBD discharge of the present invention.

Detailed ways

The implementation process will be described in detail according to the accompanying drawings 1-2. According to the preset plasma discharge atmosphere environment and pressure, open the corresponding gas source, adjust the switch control valve 11 according to the pressure gauge 12 and the flowmeter 13, so that the gas composition and content meet the preset atmospheric environment requirements; the opened gas enters the mixing chamber The mixed gas is mixed in the body 2 and sent to the semi-closed cavity 17 through the air inlet 3. The mixed gas is ionized by DBD discharge in the plasma reaction chamber 18 to generate plasma; the carbon fiber 10 is driven by the transmission/wire feeding system, passing through The plasma reaction chamber 18 is treated in the plasma generated by the DBD discharge for a certain period of time, so that the surface of the carbon fiber 10 is roughened, and at the same time, a large number of active groups are introduced to improve the bonding strength of the carbon fiber and the matrix, thereby improving the performance of the carbon fiber composite material.

The carbon fiber plasma treatment process is as follows:

Step 1, the carbon fiber 10 is degummed, cleaned, and dried for later use; the specific cleaning process is as follows: first, rinse the carbon fiber with deionized water, then soak the carbon fiber in acetone or alcohol solution for 24 hours, take it out, rinse it with deionized water, and dry it. Dry.

Step 2, the carbon fiber 10 is passed through the semi-closed cavity 17 and the plasma reaction chamber 18 in turn, and is placed on the crimping wheel 8 in sequence, wherein the initial fiber filament/tow is fixed on the driving wire take-up machine 7, The carbon fiber bundle is placed on the pay-off machine 9, and the take-up machine is manually adjusted to keep the carbon fiber in a taut state.

Step 3: Adjust the positions of the crimping rollers 8 on both sides of the semi-hermetic cavity 17 to keep them at the same horizontal position, and at the same time make the carbon fibers 10 placed thereon located in the center of the plasma reaction chamber 18 .

Step 4, according to the preset discharge atmosphere environment, open the corresponding gas source 1 on-off regulating valve 11, according to the monitoring of the pressure gauge 12 and the flowmeter 13, adjust the size of the gas released by the on-off regulating valve 11, and obtain a mixture that meets the requirements of the preset atmosphere environment. gas.

The mixed gas contains functional gas and inert gas, and the selection of functional gas is selected according to needs. If it is desired to generate active groups such as C=O, O-C=O, C-N, etc. on the fiber surface, turn on the corresponding gas source switch. Corresponding elements are introduced into the regulating valve 11, and the control of its content should consider the requirements of the active groups expected to be formed on the fiber surface on the one hand, and the requirements of the DBD discharge atmosphere on the other hand. When there is no need to introduce new elements, the inert gas is directly selected. In order to avoid filament discharge or other ribbon discharge that may damage the carbon fiber 10, the content of functional gas in the mixture should not be too high.

In step 5, the DC power supply 4 is turned on, so that the atmosphere between the electrodes is broken down, and then the mixed gas in the plasma reaction chamber 18 is ionized to generate plasma. At the beginning of the discharge, the plasma-related parameters are monitored by the plasma testing system 5, and then the input voltage and frequency of the power supply 4 are adjusted to obtain preset plasma processing parameters.

In step 6, the driving device 6 is turned on, the take-up machine 7 is driven to work, the pay-off machine 9 is driven, and the carbon fiber conveying direction is controlled by the crimping wheel 8, so that the carbon fiber 10 can pass through the plasma reaction chamber 18 at a certain speed.

The carbon fiber speed is realized by adjusting the driving device 6, and the speed value is determined according to the length of the electrode 15 and the preset carbon fiber processing time, so as to ensure that the carbon fiber processing time can be satisfied, and the processing time ranges from tens of seconds to ten minutes. During the discharge process, the plasma test system 5 also needs to monitor the plasma-related parameters in real time to ensure that the plasma environment for processing carbon fibers is consistent. If there is fluctuation, the input parameters of the power supply 4 should be adjusted in time.

To sum up, the plasma acts on the carbon fibers passing through the plasma reaction chamber. On the one hand, the surface of the fibers is etched and the surface of the fibers is roughened. On the other hand, a large number of charged particles in the plasma generated by the discharge irradiate the surface of the fibers. The chemical bonds on the surface of the fiber are reorganized to form new compounds, and a large number of active groups are introduced to increase the surface energy of the carbon fiber. The two aspects work together to improve the adhesion between the carbon fiber and the matrix. The invention provides a simple device for carbon fiber surface treatment based on atmospheric pressure DBD discharge, and overcomes the shortcomings of carbon fiber DBD surface treatment in a vacuum or low pressure environment, and solves the lack of atmospheric pressure DBD discharge carbon fiber surface treatment in the industry. device problem.

Claims (9)

1. A carbon fiber surface continuous treatment method based on normal-pressure DBD discharge is characterized by comprising the following steps:

opening gas cylinder valves of functional gas and inert gas according to a preset atmosphere environment, controlling the flow of corresponding gas cylinders, wherein the flow range is 0-50L/min, mixing the gas cylinders, filling the whole discharge cavity with mixed gas, ensuring that the discharge medium is in the preset atmosphere environment and the pressure is atmospheric pressure, and the functional gas can be oxygen, nitrogen dioxide and oxygen-containing gas; the inert gas is helium or argon;

step two, under the normal pressure atmosphere environment obtained in the step one, an electrode is connected with a high-frequency direct-current power supply, voltage is applied to two electrodes of a medium, the voltage is 10 kV-20 kV, a uniform and stable plasma area is formed, and mixed gas is adopted to purge the plasma area before the power supply is connected to generate plasma, so that the whole plasma is ensured to be filled with the mixed gas when the plasma is generated;

and step three, setting the motor speed according to the length of the discharge medium and the treatment time, and enabling the carbon fiber to continuously pass through the plasma zone obtained in the step two at the speed of 0.1-1.2m/min, thus finishing the treatment of the surface of the carbon fiber.

2. The method for continuously treating the surface of the carbon fiber based on the atmospheric-pressure DBD discharge as claimed in claim 1, wherein the predetermined atmosphere is determined according to the expected surface active groups of the carbon fiber after the continuous treatment.

3. The method for continuously processing the surface of the carbon fiber based on the atmospheric-pressure DBD discharge as claimed in claim 1, wherein the carbon fiber is subjected to a surface photoresist removing treatment before the processing in the step three.

4. The utility model provides a carbon fiber surface continuous processing device based on ordinary pressure DBD discharges which characterized in that: the device comprises a gas supply system, a plasma generation system and a carbon fiber conveying system, wherein the gas supply system comprises a gas source (1) and a mixed gas cavity (2), the gas source (1) comprises different types of inert gases, oxygen-containing gases or other gases, and each gas source comprises a switch regulating valve (11), a pressure gauge (12) and a flow meter (13); the gas mixture chamber (2) should contain a plurality of gas inlets, at least four, for mixing different types of gases into the chamber (2). The plasma generating system comprises an excitation power supply (4), a high-voltage electrode (14), a grounding electrode (15), an insulating medium (16) and a semi-closed cavity (17), wherein the first four of the high-voltage electrode and the grounding electrode form a Dielectric Barrier Discharge (DBD) device, the carbon fiber conveying system comprises a driving device (6), a take-up machine (7), a wire pressing wheel (8) and a paying-off machine (9), at least four wire pressing wheels are needed, two wire pressing wheels are arranged at two ends of the plasma and used for fixing the position of the carbon fiber (10) and ensuring that the carbon fiber can smoothly pass through a plasma reaction chamber (18); the other two wire pressing wheels are used for controlling the trend of carbon fibers, the carbon fibers discharged by the pay-off machine (9) pass through the wire pressing wheels (8), pass through the plasma reaction chamber (18), and are withdrawn by the take-up machine (7) after passing through the wire pressing wheels (8), wherein the take-up machine (7) is driven by the driving device (6), the driving device (6) works to drive the take-up machine (7) to work, the pay-off machine (9) is driven to pay off, and the automation of the whole process of carbon fiber plasma processing is realized.

5. The device for continuously treating the surface of the carbon fiber based on the atmospheric pressure DBD discharge, according to claim 4, is characterized in that: the gas source (1) is a gas cylinder filled with different gases, and each gas cylinder is provided with a switch regulating valve (11), a pressure gauge (12) and a gas flowmeter (13).

6. The device for continuously treating the surface of the carbon fiber based on the atmospheric pressure DBD discharge, according to claim 4, is characterized in that: the semi-closed cavity (17) is made of an insulating material, the cavity on the left side is designed into different external dimensions according to requirements, the wire pressing wheel can be conveniently installed, the front side and the rear side are transparent and visible at least, the left side is hermetically connected with the mixed gas cavity (2) through the gas inlet (3), and the right side of the cavity completely contains the whole DBD device; in addition, it only needs to ensure that the carbon fiber is led out to form a small hole on the left side of the cavity, the position of the small hole is flush with the position of the carbon fiber (10), and the carbon fiber is ensured to penetrate out of the small hole.

7. The device for continuously treating the surface of the carbon fiber based on the atmospheric pressure DBD discharge, according to claim 4, is characterized in that: the two wire pressing wheels (8) are not limited by size, but are positioned on two sides of the plasma reaction chamber (18), and the installation positions of the two wire pressing wheels (8) ensure that the carbon fiber (10) passing through the plasma area is positioned at the zero potential position of the center of the plasma area, so that the carbon fiber is prevented from being ablated on the conductive surface; other creasing rollers have no definite position limitation, but have the function of keeping the carbon fibers in a tense state all the time in the processing process.

8. The device for continuously treating the surface of the carbon fiber based on the atmospheric pressure DBD discharge, according to claim 4, is characterized in that: the material of the wire pressing wheel, the material of the wire rewinding machine, the material of the wire unwinding machine and the material of the shaft wheel are all conductive materials.

9. The device for continuously treating the surface of the carbon fiber based on the atmospheric pressure DBD discharge, according to claim 4, is characterized in that: the driving device (6) comprises a programmable automatic controller and a stepping/servo motor, and the controller is programmed according to the requirement of the movement rate to realize the accurate control of the stepping/servo motor.

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