A two-step plasma treatment method for enhancing the surface adhesion properties of polytetrafluoroethylene materials

Abstract

The application discloses a two-step plasma treatment method for enhancing the surface bonding performance of polytetrafluoroethylene material, and the treatment method comprises the following steps: (1) adopting a first plasma to perform surface treatment on polytetrafluoroethylene, wherein the discharge gas of the first plasma is argon or a mixed gas containing argon; (2) adopting a second plasma to bombard the surface of the polytetrafluoroethylene material after the surface treatment in step (1), so as to form a carbon-nitrogen cross-linked layer on the surface of the polytetrafluoroethylene, and obtain polytetrafluoroethylene with high bonding performance, wherein the discharge gas of the second plasma is a mixed gas of argon, methane and ammonia. The polytetrafluoroethylene sample treated by the above method has good hydrophilic performance and extremely strong bonding performance, the sample surface always maintains good hydrophilic performance in air for three months without any treatment, and the bonding strength between the treated polytetrafluoroethylene and special glue is as high as 77 N / 10 mm ‑1 .

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high polymer material modification, and particularly relates to a two-step plasma treatment method for enhancing the surface bonding performance of polytetrafluoroethylene material. BACKGROUND

[0002] With the continuous iteration of communication networks, signal high frequency has become an inevitable trend in the communication industry, and 5G network is a typical representative of high frequency communication. However, the traditional communication materials are difficult to meet the requirements of high frequency communication. From the technical point of view, electronic materials need to have precise and stable dielectric constant and smaller dielectric loss, so as to effectively solve the problem of signal transmission loss. As one of the high polymer materials with low dielectric constant, the integrity of signal transmission in polytetrafluoroethylene (PTFE) is better than that in other materials, and it is the only choice for 5G base station construction materials. In addition, PTFE, as a polymer containing only carbon and fluorine, not only has the advantage of good dielectric property, but also has the excellent properties of high temperature resistance, wear resistance, strong acid and strong alkali resistance and insolubility in organic solvents, and therefore, it is widely used in medical, aerospace, electronic and other industries. However, this material is polymerized from CF2 monomer, and its carbon chain is covered with a dense layer of fluorine atoms, which leads to poor hydrophilicity and bonding performance of the material, so that PTFE cannot be well bonded with other materials, which is one of the difficulties of PTFE in practical application.

[0003] At present, people usually adopt sodium-naphthalene complex chemical treatment method to treat PTFE material, corrode PTFE surface by using naphthalene sodium solution, change its chemical structure, and thus improve its surface hydrophilicity and bonding performance. However, this method also has many shortcomings: first, the corrosion liquid such as tetrahydrofuran not only causes harm to the body of the staff, but also causes great pollution to the environment; second, it is difficult to treat one side, and usually only two sides can be treated; third, it can cause the PTFE surface to be colored. In addition, in recent years, there are studies on surface treatment of polytetrafluoroethylene material by plasma technology, the C-F bond on the surface of PTFE is destroyed by relatively high-energy plasma, and a large specific surface area is generated on the surface, so as to improve the bonding performance of PTFE, but the bonding strength of PTFE treated by the method is insufficient, and the bonding performance of the PTFE surface is greatly reduced with the extension of the air contact time. In order to further improve the bonding performance of PTFE treated by plasma, patent CN112980039A discloses a high-bonding-performance polytetrafluoroethylene film and a preparation method and application thereof, and a polymer monomer is grafted onto the surface of PTFE treated by plasma by hydrothermal self-polymerization, but in the method, the PTFE treated by plasma is easy to be passivated after contacting with air, which seriously affects the force between the polymer modified layer and the PTFE, and the above method has problems of difficult performance control and low efficiency, and thus does not have industrial practical value. SUMMARY

[0004] The technical problem to be solved by the present application is to provide a two-step plasma treatment method for enhancing the surface bonding performance of polytetrafluoroethylene material.

[0005] To solve the above technical problems, the present application provides the following technical solutions:

[0006] The present application provides a two-step plasma treatment method for enhancing the surface bonding performance of polytetrafluoroethylene material, comprising the following steps:

[0007] S1: treating the surface of polytetrafluoroethylene by using a first plasma, wherein the discharge gas of the first plasma is argon or a mixed gas containing argon;

[0008] S2: bombarding the surface of the polytetrafluoroethylene material treated in step (1) by using a second plasma, forming a carbon-nitrogen crosslinked layer on the surface of the polytetrafluoroethylene, and obtaining a polytetrafluoroethylene surface with high bonding performance, wherein the discharge gas of the second plasma is a mixed gas of argon, methane and ammonia.

[0009] Further, in S1, the mixed gas containing argon is a mixed gas of argon and hydrogen.

[0010] The first step plasma treatment mainly acts on destroying the stable fluorocarbon structure on the surface, and roughening the surface of the PTFE to increase the specific surface area, so that the subsequent carbon-nitrogen cross-linking layer can be connected more closely with the surface of the PTFE.

[0011] Further, in S1, the ion energy of the first plasma is 100-600eV, and the surface treatment time is 1-10min.

[0012] Further, in S2, the total flow rate of the methane and the ammonia in the discharge gas accounts for 1-30%.

[0013] Further, in S2, the flow rate ratio of the methane to the ammonia in the discharge gas is 1:0.2-5.

[0014] Further, the flow rate ratio of the methane to the ammonia in the discharge gas is preferably 3:1.

[0015] Further, in S2, the ion energy of the second plasma is 100-600eV, and the surface treatment time is 1-10min.

[0016] Further, in S2, the thickness of the carbon-nitrogen cross-linking layer is 1-20nm.

[0017] The first step plasma treatment forms a fluorine-poor surface on the surface of the PTFE after the first step plasma treatment through plasma chemical reaction, and roughens the surface or forms a surface with a larger specific surface area through strong ion bombardment; after the second step plasma treatment, a nanoscale carbon-nitrogen thin layer is formed on the surface of the PTFE, and in addition, the ion energy in the second step plasma also forms a strong bonding force between the carbon-nitrogen cross-linking layer and the PTFE. Since the carbon-nitrogen cross-linking layer has a stable structure and a rich cross-linking structure, the treated PTFE can maintain good hydrophilic performance and strong adhesive performance for a long time in the air; however, the carbon-nitrogen cross-linking layer should not be too thick, and a long time of the second step plasma treatment of the PTFE surface to obtain a too thick carbon-nitrogen cross-linking layer will affect the bonding force with the PTFE, so the thickness of the carbon-nitrogen cross-linking layer needs to be controlled within a suitable range, i.e. 1-20nm.

[0018] Further, the plasma is a capacitive coupling plasma or an inductive coupling plasma.

[0019] Further, the above two-step plasma treatment is continuously performed by switching the discharge gas.

[0020] The present application realizes seamless connection of the two-step plasma treatment by switching the discharge gas, without the need to remove the PTFE sample from the cavity, thus avoiding the problem of surface passivation and even aging caused by the contact of the PTFE material with air during removal, and continuous operation is conducive to enhancing the bonding force of the carbon-nitrogen cross-linking layer with the PTFE.

[0021] The present application has the advantages of:

[0022] 1. The present application solves the problem of insufficient bonding strength of PTFE by modifying the surface of PTFE through a two-step plasma treatment method; wherein the first step of plasma treatment defluorinates the surface of PTFE while increasing the specific surface area of PTFE, and then the second step of plasma treatment is achieved by simply switching the discharge gas, and a carbon-nitrogen crosslinking layer is formed on the surface of PTFE through plasma chemical reaction, which has stable structure and no aging problem, and the existence of the crosslinking layer effectively suppresses the rearrangement of surface atoms on one hand, and on the other hand, it also blocks the direct contact between the inner PTFE and air, avoiding reaction with air; the PTFE treated by the two-step plasma treatment method of the present application maintains good hydrophilic performance on its surface for three months in air, and due to the rich crosslinking structure of the carbon-nitrogen crosslinking layer on the surface of PTFE, the bonding performance of PTFE and adhesive is greatly improved, reaching up to 77 N / 10 mm, far exceeding the bonding performance index (50 N / 10 mm) of the industrial standard material treated by the sodium naphthalene solution method.

[0023] 2. The two-step plasma treatment method of the present application is simple and easy to operate, and the process is controllable, and there is no aging problem in the prior art plasma treatment, which has industrial practical value, and the treated PTFE has excellent bonding performance while not affecting its own strength, dielectric constant and other properties, and can be widely used in medical, aerospace, electronic and other industries. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 It is a schematic diagram of a capacitive coupling plasma device for treating the surface of PTFE material;

[0025] Figure 2 It is a schematic diagram of an inductive coupling plasma device for treating the surface of PTFE material;

[0026] Figure 3 It is a surface morphology diagram of PTFE film before and after capacitive coupling plasma treatment: (a) untreated sample, (b) sample after plasma treatment;

[0027] Figure 4 It is an XPS full spectrum diagram of PTFE film before and after capacitive coupling plasma treatment: (a) untreated sample, (b) sample after plasma treatment;

[0028] Figure 5 It is a surface morphology diagram of PTFE film before and after inductive coupling plasma treatment: (a) untreated sample, (b) sample after plasma treatment. DETAILED DESCRIPTION

[0029] The present application will be further described with reference to the drawings and specific examples, so that those skilled in the art can better understand the present application and implement it, but the examples are not intended to limit the present application.

[0030] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present application. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0031] Example 1

[0032] This embodiment relates to a capacitive coupling plasma discharge device which can realize two-step plasma processing, and a device schematic diagram is shown in Figure 1 The device includes a gas control system, a chamber, a power supply system and a pumping system. The gas control system includes an argon storage tank 1, an ammonia storage tank 2 and a methane storage tank 3. Each gas storage tank is connected to the gas inlet channel of the chamber 5 through a gas flow controller 4. The gas flow controller controls the flow of different gases into the chamber. The chamber is provided with an upper electrode plate 9 and a lower electrode plate 6 which is insulated from the chamber. The lower electrode plate is connected to a radio frequency power supply 8 through a radio frequency matching device 7. When the lower electrode plate is connected to the power supply, capacitive coupling plasma is generated. The chamber is provided with a vacuum environment by a pumping system composed of a molecular pump 11 and a mechanical pump 12. The vacuum degree in the chamber is controlled by a vacuum gauge 10 arranged between the chamber and the molecular pump. The two-step plasma processing method is realized by controlling the gas, the gas pressure in the chamber, the power of the radio frequency power supply and the processing time.

[0033] Example 2

[0034] This embodiment relates to an inductive coupling plasma discharge device which can realize two-step plasma processing, and a device schematic diagram is shown in Figure 2As shown, including gas control system, chamber, power system and pumping system, the gas control system includes argon storage tank 1, ammonia storage tank 2 and methane storage tank 3, each gas storage tank is connected with the gas inlet channel of the chamber 5 through a gas flow controller 4, the gas flow controller controls the gas with different flow rate to be introduced into the chamber, the lower plate 6 insulated from the chamber is arranged in the chamber, the lower plate is connected with the radio frequency power supply 8 through the radio frequency matching device 7, the lower plate is connected with the power supply, and the capacitive coupled plasma is generated, the top of the chamber is covered with a certain thickness of quartz plate 11 to maintain high vacuum, and a disc type coil is fixed on the quartz plate, the disc type coil is connected with the radio frequency power supply 10 through the radio frequency matching device 9; The vacuum environment of the chamber is completed by the pumping system composed of the molecular pump 13 and the mechanical pump 14, and the vacuum degree in the chamber is regulated by the vacuum gauge 12 arranged between the chamber and the molecular pump. The two-step plasma treatment method is realized by regulating the introduced gas, the gas pressure of the chamber, the power of the radio frequency power supply and the processing time.

[0035] Example 3

[0036] In this embodiment, the capacitive coupled plasma discharge device described in embodiment 1 is used to perform two-step plasma treatment on PTFE film with a thickness of 0.2 mm and a size of 50*50 mm and PTFE plate with a thickness of 3 mm and a size of 140*140 mm, and the specific operation is as follows:

[0037] (1) Place the sample on the lower plate in the chamber, use the mechanical pump and the molecular pump to pump the chamber to 1*10 - 3 Pa, open the argon cylinder, adjust the flow rate to 80 sccm, adjust the chamber pressure to 5 Pa, turn on the radio frequency power supply with a frequency of 13.56 MHz, adjust the power to 150 W, the chamber will generate light purple plasma, and the processing time is 8 min;

[0038] (2) Introduce mixed gas with a flow rate ratio of Ar:NH3:CH4=60:15:5, the total flow rate is 80 sccm, the chamber pressure is still adjusted to 5 Pa, the radio frequency power supply is turned on, the power is adjusted to 150 W, and the work is 5 min, the two-step plasma treatment is completed, and the surface treated PTFE film and PTFE plate are obtained.

[0039] The PTFE film before and after surface treatment is characterized by SEM, and the results are shown in Figure 3 The surface of the PTFE film without surface treatment is Figure 3 a) smooth and flat, and the surface of the PTFE film after two plasma treatments is Figure 3b) The surface is covered with needle-like protrusions, greatly increasing its surface roughness. Further, the surface chemical structure of the PTFE membrane before and after surface treatment was detected by XPS, and the full spectrum is shown in FIG. 2. After two-step plasma treatment, the proportion of F element on the material surface decreased from 80.31% to 7.47%, F element was replaced by C and N, and a carbon-nitrogen cross-linked layer was formed on the material surface. Figure 4 As shown in FIG. 2, after two-step plasma treatment, the proportion of F element on the material surface decreased from 80.31% to 7.47%, F element was replaced by C and N, and a carbon-nitrogen cross-linked layer was formed on the material surface.

[0040] In addition, the tensile test was performed on the plate after two-step plasma treatment, and the specific operation was as follows: the treated PTFE was cut into a long strip with a length of 140 mm and a width of 30 mm, and was bonded with a cast iron (the surface was treated with borax of 80 mesh) of the same size. The cast iron was attached to the PTFE by special glue, the length of the bonding part was 100 mm, and the both ends were left out for 40 mm, and was clamped between the upper and lower clamps. After baking at 10 MPa pressure and 180°C for one hour, the sample was taken out and fixed on the instrument, and the upper and lower clamps were separated at a speed of 100±10 mm / min, and the average bonding strength was 77 N·10 mm -1 Therefore, the PTFE surface treated by two-step plasma treatment has good bonding performance, which can meet the needs of industrial applications.

[0041] Example 4

[0042] In this example, the inductively coupled plasma discharge device described in Example 2 was used to treat PTFE membranes with a thickness of 0.2 mm and a size of 50*50 mm and PTFE plates with a thickness of 3 mm and a size of 140*140 mm by two-step plasma treatment, and the specific operation was as follows:

[0043] (1) First, connect the lower electrode plate to a 13.56 MHz radio frequency power source, and the coil to a 13.56 MHz radio frequency power source. Fix the sample on the lower electrode plate, seal the chamber, and then open the mechanical pump and molecular pump in sequence to reduce the chamber base pressure to 1*10 -3 Pa. Introduce argon gas, control the flow rate at 80 sccm, adjust the gas pressure to 5 Pa, turn on the two radio frequency power switches respectively, adjust the power so that the coil power is 150 W and the power input into the lower electrode plate is 100 W, and complete the power matching. Observe that the chamber emits purple light, which indicates that the discharge has started. Turn off the power after 6 minutes of discharge;

[0044] (2) Introduce CH4 and NH3, with a flow ratio of Ar:NH3:CH4=60:15:5, and a total flow rate of 80 sccm. Still adjust the chamber pressure to 5 Pa, turn on the power of the coil and the lower electrode plate, and discharge at the same power as in the first step for 4 minutes to complete the two-step plasma treatment, and obtain the PTFE membrane and PTFE plate after surface treatment.

[0045] The PTFE films before and after surface treatment were characterized by SEM, and the results are as follows: Figure 4 As shown, the surface of the untreated PTFE membrane ( Figure 5 a) The surface of the PTFE membrane after two plasma treatments is smooth and flat. Figure 5 b) Numerous worm-like protrusions appeared, greatly increasing the specific surface area. The thickness of the carbon-nitrogen cross-linked layer on the surface was measured to be 8 nm using a profilometer. Subsequently, the surface chemical structure of the PTFE film before and after surface treatment was detected by XPS. The detection results are shown in Table 1. After two-step plasma treatment, the F / C ratio of the material surface decreased sharply from 8.49 to 0.19.

[0046] Table 1. F / C ratio and element content percentage of PTFE membrane surface before and after two-step plasma treatment.

[0047] Sample F / C ratio C F N O Before treatment 8.49 9.46 80.31 1.39 8.84 After treatment 0.19 43.51 6.50 6.79 43.20

[0048] In addition, tensile tests were performed on the plates after two-step plasma treatment. The specific operation was as follows: The treated PTFE was cut into strips 140mm long and 30mm wide, and bonded to cast iron of the same size (the surface of which had been treated with 80-mesh borax). The cast iron was then attached to the PTFE with a special adhesive, with the bonded portion being 100mm long and leaving 40mm at both ends, and clamped on upper and lower clamps. After being subjected to a pressure of 10MPa and baked at 180℃ for one hour, the sample was removed and fixed on the instrument. The testing machine was started, and the upper and lower clamps were separated at a rate of 100±10mm / min. The average bond strength was taken as 45.8N·10mm. -1 .

[0049] Example 5

[0050] This embodiment uses the capacitively coupled plasma discharge device described in Embodiment 1 to perform the following two-step plasma treatment on a PTFE sheet with a thickness of 3mm and dimensions of 140*140mm. The specific operation is as follows:

[0051] (1) Place the sample on the lower electrode plate in the chamber and use a mechanical pump and a molecular pump to evacuate the chamber pressure to 1*10. - 3 Pa, open the argon gas cylinder, adjust the flow rate to 80 sccm, adjust the chamber pressure to 5 Pa, connect the 13.56 MHz radio frequency power supply, and adjust the power to 150 W. A light purple plasma will be generated inside the chamber. The processing time is 8 minutes.

[0052] (2) mixed gas with flow ratio of Ar:NH3:CH4=60:10:10 was introduced, total flow was 80sccm, chamber pressure was still adjusted to 5Pa, radio frequency power was turned on, power was adjusted to 150W, working for 5min, two-step plasma treatment was completed, and surface-treated PTFE plate was obtained.

[0053] Tensile test was performed on the plate after the above two-step plasma treatment, the specific operation was as follows: the treated PTFE was cut into a long strip with a length of 140mm and a width of 30mm, and was bonded with cast iron (the surface was treated with 80 mesh borax) with the same size. The cast iron was attached to the PTFE by special glue, the length of the bonding part was 100mm, and 40mm was left at both ends, and was clamped between the upper and lower clamps. After baking at 10MPa pressure and 180℃ for one hour, the sample was taken out and fixed on the instrument, the upper and lower clamps were separated at a speed of 100±10mm / min, and the average bonding strength was 68.45N·10mm -1 .

[0054] Example 6

[0055] In this example, the capacitive coupling plasma discharge device described in Example 1 was used to perform two-step plasma treatment on a PTFE plate with a thickness of 3mm and a size of 140*140mm, the specific operation was as follows:

[0056] (1) the sample was placed on the lower electrode plate in the chamber, the chamber pressure was pumped to 1*10 - 3 Pa by mechanical pump and molecular pump, argon gas cylinder was opened, flow was adjusted to 80sccm, chamber pressure was adjusted to 5Pa, radio frequency power with a frequency of 13.56MHz was turned on, power was adjusted to 150W, light purple plasma was generated in the chamber, and the treatment time was 8min;

[0057] (2) mixed gas with flow ratio of Ar:NH3:CH4=65:5:10 was introduced, total flow was 80sccm, chamber pressure was still adjusted to 5Pa, radio frequency power was turned on, power was adjusted to 150W, working for 5min, two-step plasma treatment was completed, and surface-treated PTFE plate was obtained.

[0058] Tensile test was performed on the PTFE plate after the two-step plasma treatment. The specific operation is as follows: the treated PTFE was cut into a long strip with a length of 140 mm and a width of 30 mm, and was bonded with cast iron (the surface was treated with borax of 80 mesh) of the same size. The cast iron was attached to the PTFE by special glue, the length of the bonding part was 100 mm, and 40 mm was left at both ends. After baking at 180°C under a pressure of 10 MPa for one hour, the sample was taken out and fixed on the instrument. The upper and lower clamps were separated at a speed of 100±10 mm / min, and the average bonding strength was 63 N·10 mm -1 .

[0059] Example 7

[0060] In this example, the capacitive coupling plasma discharge device described in Example 1 was used to perform two-step plasma treatment on a PTFE plate with a thickness of 3 mm and a size of 140*140 mm. The specific operation is as follows:

[0061] (1) The sample was placed on the lower electrode plate in the chamber, and the chamber pressure was pumped to 1*10 - 3 Pa using a mechanical pump and a molecular pump. The argon gas cylinder was opened, the flow rate was adjusted to 80 sccm, the chamber pressure was adjusted to 5 Pa, the radio frequency power supply with a frequency of 13.56 MHz was turned on, the power was adjusted to 150 W, a light purple plasma was generated inside the chamber, and the treatment time was 8 min.

[0062] (2) The mixed gas with a flow rate ratio of Ar:NH3:CH4=65:10:5 was introduced, the total flow rate was 80 sccm, the chamber pressure was still adjusted to 5 Pa, the radio frequency power supply was turned on, the power was adjusted to 150 W, and the work was 5 min. The two-step plasma treatment was completed, and the surface-treated PTFE plate was obtained.

[0063] Tensile test was performed on the PTFE plate after the two-step plasma treatment. The specific operation is as follows: the treated PTFE was cut into a long strip with a length of 140 mm and a width of 30 mm, and was bonded with cast iron (the surface was treated with borax of 80 mesh) of the same size. The cast iron was attached to the PTFE by special glue, the length of the bonding part was 100 mm, and 40 mm was left at both ends. After baking at 180°C under a pressure of 10 MPa for one hour, the sample was taken out and fixed on the instrument. The upper and lower clamps were separated at a speed of 100±10 mm / min, and the average bonding strength was 63 N·10 mm -1 .

[0064] Comparative Example 1

[0065] The comparative example adopts the capacitive coupling plasma discharge device described in Example 1, and replaces the methane or ammonia storage tank with an oxygen storage tank. A PTFE plate with a thickness of 3 mm and a size of 140*140 mm is subjected to two-step plasma treatment, and the specific operation is as follows:

[0066] (1) Place the sample on the lower plate in the chamber, and use a mechanical pump and a molecular pump to reduce the chamber pressure to 1*10 - 3 Pa, open the argon gas cylinder, adjust the flow rate to 80 sccm, adjust the chamber pressure to 5 Pa, turn on the radio frequency power supply with a frequency of 13.56 MHz, adjust the power to 150 W, and a light purple plasma will be generated inside the chamber. The treatment time is 8 min.

[0067] (2) Introduce a mixed gas with a flow rate ratio of Ar:O2=60:20, the total flow rate is 80 sccm, and the chamber pressure is still adjusted to 5 Pa. Turn on the radio frequency power supply, adjust the power to 150 W, and work for 5 min to complete the two-step plasma treatment, and obtain the surface-treated PTFE plate.

[0068] The plate subjected to the above two-step plasma treatment is subjected to a tensile test, and the specific operation is as follows: cut the treated PTFE into a long strip with a length of 140 mm and a width of 30 mm, and adhere it to a cast iron (the surface has been treated with 80 mesh borax) with the same size. Attach the cast iron to the PTFE by using special glue, the length of the adhesive part is 100 mm, and the two ends are left out by 40 mm, and clamp it between the upper and lower clamps. After baking at a pressure of 10 MPa and a temperature of 180℃ for one hour, take out the sample, fix it on the instrument, start the testing machine, and separate the upper and lower clamps at a speed of 100±10 mm / min, and the average adhesive strength is 35 N·10 mm -1 .

[0069] Comparative Example 2

[0070] The comparative example adopts the capacitive coupling plasma discharge device described in Example 1, and only one-step plasma treatment is performed on a PTFE plate with a thickness of 3 mm and a size of 140*140 mm, and the specific operation is as follows:

[0071] Place the sample on the lower plate in the chamber, and use a mechanical pump and a molecular pump to reduce the chamber pressure to 1*10 -3 Pa, open the argon gas cylinder, adjust the flow rate to 80 sccm, adjust the chamber pressure to 5 Pa, turn on the radio frequency power supply with a frequency of 13.56 MHz, adjust the power to 150 W, and a light purple plasma will be generated inside the chamber. The treatment time is 8 min, and the surface-treated PTFE plate is obtained.

[0072] Tensile test was performed on the PTFE plate after the above one-step plasma treatment. The specific operation is as follows: the treated PTFE is cut into a long strip with a length of 140 mm and a width of 30 mm, and is bonded with cast iron (the surface is treated with borax of 80 mesh) of the same size. The cast iron is attached to the PTFE by special glue, the length of the bonding part is 100 mm, and 40 mm is left at both ends. After baking at 10 MPa pressure and 180℃ for one hour, the sample is taken out and fixed on the instrument. The upper and lower clamps are separated at a speed of 100±10 mm / min, and the average bonding strength is 37 N·10 mm -1 .

[0073] Comparative Example 3

[0074] In this comparative example, the capacitive coupled plasma discharge device described in Example 1 is used. The storage tank of methane or ammonia is replaced with an oxygen storage tank. Only one-step plasma treatment is performed on a PTFE plate with a thickness of 3 mm and a size of 140*140 mm. The specific operation is as follows:

[0075] The sample is placed on the lower electrode plate in the chamber. The chamber pressure is pumped to 1*10 -3 Pa using a mechanical pump and a molecular pump. The mixed gas with a flow ratio of Ar:O2=60:20 is introduced, the total flow is adjusted to 80 sccm, the chamber pressure is adjusted to 5 Pa, the radio frequency power supply with a frequency of 13.56 MHz is turned on, the power is adjusted to 150 W, a light purple plasma is generated in the chamber, the treatment time is 8 min, and the surface treated PTFE plate is obtained.

[0076] Tensile test was performed on the PTFE plate after the above one-step plasma treatment. The specific operation is as follows: the treated PTFE is cut into a long strip with a length of 140 mm and a width of 30 mm, and is bonded with cast iron (the surface is treated with borax of 80 mesh) of the same size. The cast iron is attached to the PTFE by special glue, the length of the bonding part is 100 mm, and 40 mm is left at both ends. After baking at 10 MPa pressure and 180℃ for one hour, the sample is taken out and fixed on the instrument. The upper and lower clamps are separated at a speed of 100±10 mm / min, and the average bonding strength is 37 N·10 mm -1 .

[0077] Comparative Example 4

[0078] In this comparative example, the capacitive coupled plasma discharge device described in Example 1 is used. Only one-step plasma treatment is performed on a PTFE plate with a thickness of 3 mm and a size of 140*140 mm. The specific operation is as follows:

[0079] The sample was placed on the lower electrode plate in the chamber, and the chamber pressure was pumped to 1*10 -3 Pa, the mixed gas with a flow ratio of Ar:NH3=60:20 was introduced, the total flow was adjusted to 80 sccm, the chamber pressure was adjusted to 5 Pa, the radio frequency power supply with a frequency of 13.56 MHz was turned on, the power was adjusted to 150 W, a light purple plasma was generated in the chamber, the treatment time was 8 min, and the PTFE plate after surface treatment was obtained.

[0080] The plate after the above step of plasma treatment was subjected to tensile test, and the specific operation was as follows: the treated PTFE was cut into a long strip with a length of 140 mm and a width of 30 mm, and was bonded with a cast iron (the surface was treated with 80 mesh borax) with the same size. The cast iron piece was attached to the PTFE by special glue, the length of the bonding part was 100 mm, and 40 mm was left at both ends, and was clamped on the upper and lower clamps. After baking at a pressure of 10 MPa and 180°C for one hour, the sample was taken out and fixed on the instrument, the upper and lower clamps were separated at a speed of 100±10 mm / min, and the average bonding strength was 30.1 N·10mm -1 .

[0081] Comparative Example 5

[0082] This comparative example used the capacitive coupling plasma discharge device described in Example 1 to perform one-step plasma treatment on a PTFE plate with a thickness of 3 mm and a size of 140*140 mm, and the specific operation was as follows:

[0083] The sample was placed on the lower electrode plate in the chamber, and the chamber pressure was pumped to 1*10 -3 Pa, the mixed gas with a flow ratio of Ar:NH3:CH4=60:10:10 was introduced, the total flow was adjusted to 80 sccm, the chamber pressure was adjusted to 5 Pa, the radio frequency power supply with a frequency of 13.56 MHz was turned on, the power was adjusted to 150 W, a light purple plasma was generated in the chamber, the treatment time was 8 min, and the PTFE plate after surface treatment was obtained.

[0084] The PTFE plate after the above-mentioned plasma treatment was subjected to a tensile test, and the specific operation was as follows: the treated PTFE was cut into a long strip with a length of 140 mm and a width of 30 mm, and was bonded with a cast iron (the surface was treated with borax of 80 mesh) of the same size. The cast iron piece was attached to the PTFE by special glue, the length of the bonding part was 100 mm, and 40 mm was left at both ends, and was clamped on the upper and lower clamps. After baking at 10 MPa pressure and 180℃ for one hour, the sample was taken out and fixed on the instrument, the upper and lower clamps were separated at a speed of 100±10 mm / min, and the average bonding strength was 29 N·10 mm -1 .

[0085] The bonding strength of the PTFE plate after the surface treatment of the above-mentioned examples 3-7 and comparative examples 1-5 is shown in Table 2 as follows:

[0086] Table 2 Bonding strength of PTFE plate after surface treatment of examples 3-7 and comparative examples 1-5

[0087]

[0088]

[0089] In the table, ① refers to the gas of the first plasma treatment, and ② refers to the gas of the second plasma treatment.

[0090] From the above Table 2, it can be seen that the two-step plasma treatment method according to the present application can significantly improve the bonding performance of PTFE, especially after treatment with a capacitive coupling plasma device, the effect is better, and the bonding strength can reach 77 N·10 mm -1 , which is much higher than the bonding performance of 50 N·10 mm -1 of the standard material treated by the sodium naphthalene solution method, and meets the industrial application requirements.

[0091] The above-mentioned examples are only preferred examples for fully illustrating the present application, and the protection scope of the present application is not limited thereto. The equivalent substitutions or transformations made by the person skilled in the art on the basis of the present application are within the protection scope of the present application. The protection scope of the present application is subject to the claims.

Claims

1. A two-step plasma treatment method for enhancing the surface adhesion properties of polytetrafluoroethylene material, characterized by, The processing method comprises: S1: adopting a first plasma to perform surface treatment on polytetrafluoroethylene material, so as to make the polytetrafluoroethylene surface defluorinate and increase the specific surface area of the polytetrafluoroethylene, wherein the discharge gas of the first plasma is argon or a mixed gas containing argon; S2: adopting a second plasma to bombard the surface of the polytetrafluoroethylene material after the surface treatment in step (1), so as to form a carbon-nitrogen crosslinked layer on the surface of the polytetrafluoroethylene material, form a strong bonding force between the carbon-nitrogen crosslinked layer and the polytetrafluoroethylene material, and obtain a polytetrafluoroethylene surface with high bonding performance, wherein the discharge gas of the second plasma is a mixed gas of argon, methane and ammonia; and the thickness of the carbon-nitrogen crosslinked layer is 1-20 nm.

2. The method of claim 1, wherein, In S1, the mixed gas containing argon is a mixed gas of argon and hydrogen.

3. The method of claim 1, wherein, In S1, the ion energy of the first plasma is 100-600 eV, and the surface treatment time is 1-10 min.

4. The method of claim 1, wherein, In S2, the total flow rate of methane and ammonia in the discharge gas accounts for 1-30%.

5. The method of claim 1, wherein, In S2, the flow rate ratio of methane to ammonia in the discharge gas is 1:0.2-5.

6. The method of claim 5, wherein, The flow rate ratio of methane to ammonia in the discharge gas is 3:

1.

7. The method of claim 1, wherein, In S2, the ion energy of the second plasma is 100-600 eV, and the surface treatment time is 1-10 min.

8. The method of claim 1, wherein, The plasma is a capacitive coupling plasma or an inductive coupling plasma.

9. The method of claim 1, wherein, The two-step plasma treatment is continuously performed by switching the discharge gas.

Images