Method for preparing electrically conductive high wear-resistant carbon nanotube film

Abstract

This invention relates to the field of conductive, wear-resistant, and superhydrophobic materials, particularly a method for preparing conductive and highly wear-resistant carbon nanotube films. The invention involves first coating a pretreated carbon nanotube film with an epoxy resin layer for pre-curing, then spraying an HD / KH570 / SiO2 solution onto the surface of the pre-cured epoxy resin layer. After curing the coating, a conductive and highly wear-resistant carbon nanotube film is formed. The carbon nanotube film prepared by this method retains the conductivity of the original film while simultaneously increasing its hydrophobic and wear-resistant properties.

Description

Technical Field

[0001] This invention relates to the field of superhydrophobicity, and in particular to a method for preparing mechanically stable superhydrophobic carbon nanotube films with conductive hydrophobic effects. Background Technology

[0002] To adapt to the rapidly developing flexible and wearable electronic products or devices, materials with novel and outstanding properties such as lightweight, waterproof, and self-cleaning are constantly being developed. Electronic devices such as mobile phones and telecommunications cabinets are already widely used outdoors. Therefore, it is necessary to improve the protection of these devices from electrochemical corrosion or electrical short circuits caused by moisture (water vapor) and liquid water. Constructing superhydrophobic coatings on carbon nanotube films is an important way to obtain waterproof surfaces. However, due to the weak adhesion between the coating and the substrate, the superhydrophobicity of the coating is easily lost under mechanical loads. CN202310731885.1 describes a method for preparing a durable superhydrophobic carbon nanotube film composite material, in which a PDMS prefabricated layer is inserted between a carbon nanotube film substrate and a superhydrophobic coating to prepare a superhydrophobic coating based on PDMS and SiO2 nanoparticles. In the thermosetting crosslinking reaction, the SiO2 nanoparticles encapsulated by PDMS are partially embedded in the incompletely cured PDMS prepreg. The abrasion resistance of the PDMS prepreg can only guarantee about 30 wear cycles at most. After more than 30 cycles, its surface integrity is damaged, and it is difficult to guarantee the mechanical stability of the surface hydrophobic effect.

[0003] This invention proposes a method for preparing a composite material with excellent mechanical stability while maintaining the conductivity of carbon nanotube films. An epoxy resin layer is inserted between the carbon nanotube film treated with air plasma and a coating to improve the mechanical bonding strength between the superhydrophobic layer and the carbon nanotube film. Then, an HD / KH570 / SiO2 solution is sprayed onto the surface to achieve superhydrophobicity. The sprayed coating is embedded in the epoxy resin layer, and after complete curing, a conductive and wear-resistant carbon nanotube film is formed. The carbon nanotube film prepared by this method retains the conductivity of the original film while increasing its hydrophobicity and abrasion resistance, thus broadening the application fields of carbon nanotube films. Summary of the Invention

[0004] The purpose of this invention is to expand the application of carbon nanotube films in the field of waterproofing, and to improve the mechanical stability of the surface hydrophobic effect while maintaining the excellent conductivity of the carbon nanotube film itself.

[0005] This invention prepares a conductive and durable superhydrophobic carbon nanotube thin film material, comprising the following steps:

[0006] Step 1: Perform plasma cleaning pretreatment on the carbon nanotube film substrate;

[0007] Step 2: Dissolve the epoxy resin and its curing agent in hexane at a mass ratio of 4:1, and then sonicate to form a viscous solution. The epoxy resin used is E-51; the curing agent used is T-31.

[0008] Step 3: Weigh out nano-SiO2 particles and dissolve them in a beaker containing anhydrous ethanol. Stir the mixture ultrasonically for 30 minutes to obtain solution A. The concentration of solution A is 0.01 g / L.

[0009] Step 4: Add 1-9 wt% of silane coupling agent KH-570 to a beaker of deionized water, and sonicate for 30 minutes to allow it to fully hydrolyze, thus obtaining solution B.

[0010] Step 5: Add solutions A, B, and HDTMS sequentially into the flask, then place the flask in a magnetically stirred constant temperature bath at 70°C and 800 rpm for 4 hours to obtain a hydrophobic HD / KH570 / SiO2 solution, named solution C.

[0011] Step Six: Coat the carbon nanotube film with the viscous epoxy resin solution formed in Step Two for pre-curing. Adjust the pre-curing temperature to 80℃ and the pre-curing time to 10–30 min. A further preferred pre-curing time is 10–20 min.

[0012] Step 7: Take out the pre-cured carbon nanotube film, spray solution C onto the carbon nanotube film containing the epoxy resin layer, and put it into an oven for curing. The curing temperature is 80℃ and the curing time is 6 hours. After curing, a conductive, wear-resistant, superhydrophobic carbon nanotube film is obtained.

[0013] Further, solution B was prepared by adding 1-9 wt% of silane coupling agent KH-570 to a beaker containing 30 mL of deionized water per 6 mL of water and then sonicating it thoroughly to obtain solution B; the concentration of HDTMS was 1-6 wt%; and the volume ratio of solution A, solution B and HDTMS was 10:10:1.

[0014] Furthermore, in step six, the amount of epoxy resin viscous solution used on the carbon nanotube film is: 1-2 ml of epoxy resin viscous solution is applied to every 5*5 cm carbon nanotube film.

[0015] Furthermore, the relative amount of C solution used in the pre-cured carbon nanotube film is: 3 ml of C solution is coated on the surface of each 5*5 cm carbon nanotube film.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention selects epoxy resin as the intermediate adhesive layer, and through the adjustment of each component, the adhesion between the coating and the substrate can be greatly improved, ensuring the mechanical stability of the hydrophobic effect of the surface. Even under high long-term wear intensity, it can still maintain good hydrophobic performance and surface integrity. Attached Figure Description

[0017] Figure 1 A photograph of the conductive, wear-resistant, superhydrophobic carbon nanotube thin film composite material prepared according to the present invention.

[0018] Figure 2 The contact angle of the conductive, wear-resistant, superhydrophobic carbon nanotube thin film composite material prepared in this invention;

[0019] Figure 3 The water repellency test results are shown for the conductive, wear-resistant, superhydrophobic carbon nanotube film composite material prepared in this invention.

[0020] Figure 4 Water droplet adhesion test of the conductive, wear-resistant, superhydrophobic carbon nanotube thin film composite material prepared in this invention;

[0021] Figure 5 SEM image of the conductive, wear-resistant, superhydrophobic carbon nanotube thin film composite material prepared in this invention;

[0022] Figure 6 Figure 1 shows the wear resistance test data of the conductive, wear-resistant, superhydrophobic carbon nanotube thin film composite material prepared in this invention with different mesh sizes.

[0023] Figure 7 The conductive, wear-resistant, superhydrophobic carbon nanotube thin film composite material prepared in this invention is shown in the experimental diagram of conductivity.

[0024] Figure 8 The images show five groups of epoxy resin layers prepared at different pre-curing times for the conductive, wear-resistant, superhydrophobic carbon nanotube thin film composite material prepared in this invention.

[0025] Figure 9 The contact angle trend of the conductive, wear-resistant, superhydrophobic carbon nanotube thin film composite material prepared in this invention under friction test;

[0026] Figure 10 The contact angle trend of the conductive, wear-resistant, superhydrophobic carbon nanotube film composite material prepared in this invention under stronger wear-resistant cycling is shown in the figure.

[0027] Figure 11 A comparison of the wear resistance of the original conductive wear-resistant superhydrophobic carbon nanotube thin film composite material prepared for this invention without an epoxy resin layer and with an epoxy resin layer.

[0028] Figure 12 The graph shows the changes in contact angle at different KH570 concentrations.

[0029] Figure 13 The graph shows the change in contact angle under different HDTMS concentrations. Detailed Implementation

[0030] The present invention will be further described in detail below with reference to specific embodiments, but the scope of protection of the present invention is not limited to the content described.

[0031] Example 1

[0032] Step 1: Pre-treat the carbon nanotube film substrate. Place the long strip of carbon nanotube film on a stainless steel plate and press it down with a copper sheet to prevent it from being sucked in during vacuuming. Place it in a plasma cleaning chamber with a plasma cleaning power of 100W and a time of 100s.

[0033] Step 2: Dissolve 0.3g of epoxy resin (purchased from Shandong Yousuo Chemical Technology Co., Ltd., model E-51) and curing agent T-31 in 12ml of n-hexane at a mass ratio of 4:1, and then sonicate to form a viscous solution.

[0034] Step 3: Weigh 0.3g of nano-SiO2 particles and dissolve them in a beaker containing 30mL of anhydrous ethanol. Stir ultrasonically for 30min to obtain solution A. Take 6ml of 7wt% silane coupling agent KH-570 and add it to a beaker containing 30mL of deionized water. Stir ultrasonically for 30min to allow it to fully hydrolyze and obtain solution B.

[0035] Step 4: Add 10 mL of solution A, 10 mL of solution B, and 1 mL of HDTMS (concentration of 3 wt%) to a 150 mL flask in sequence. Then place the flask in a magnetically stirred constant temperature bath at 70 °C and 800 rpm for 4 h to obtain a hydrophobic HD / KH570 / SiO2 solution, named solution C.

[0036] Step 5: Apply an epoxy resin layer to the carbon nanotube film for pre-curing. Adjust the pre-curing temperature to 80℃ and the pre-curing time to 20 minutes. Remove the pre-cured carbon nanotube film and spray solution C onto the carbon nanotube film containing the epoxy resin layer. Place it in an oven for curing at 80℃ for 6 hours. After curing, a conductive, wear-resistant, superhydrophobic carbon nanotube film is obtained.

[0037] Figure 1 In Figure 1, a is the original carbon nanotube film, b is the sample of Example 1 after pre-curing with an epoxy resin coating, and c is the actual conductive and durable carbon nanotube film prepared in Example 1.

[0038] Figure 2 The left image shows the contact angle of the original carbon nanotube film, and the right image shows the contact angle of the conductive, wear-resistant, and superhydrophobic carbon nanotube film of Example 1. It can be seen that the surface contact angle has been greatly improved, from 105° to 158°, achieving a superhydrophobic state.

[0039] Figure 3 It can be seen that the conductive and durable carbon nanotube film prepared in Example 1 has good water repellency, and water droplets can easily bounce and roll off the sample surface.

[0040] Figure 4 Under the contact angle tester, the process of water droplets adhering to and being pulled up on the surface, and the "contact-pull-away" adhesion of a 10μL water droplet, demonstrates that the sample surface has good hydrophobicity.

[0041] Figure 5 The image shows the surface of the conductive and durable carbon nanotube film prepared in Example 1. The surface is composed of SiO2 aggregates, exhibiting large clumps of particles, which provides high roughness.

[0042] Figure 6 To illustrate the wear resistance data of the conductive and durable carbon nanotube film prepared in Example 1 at different mesh sizes, a group of samples was selected and subjected to friction cycles at 800 / 1000 / 1200 mesh. These samples maintained a high contact angle and preserved the superhydrophobic properties of the surface. Specifically, a friction cycle was defined as a 30cm friction length on sandpaper. The samples were rubbed with 800 / 1000 / 1200 mesh sandpaper, with a 200g weight attached to the surface. Changes in the contact angle after each friction cycle were measured. Figure 6 It can be seen that after 30 friction cycles, the samples at all three mesh sizes still maintained a high contact angle, and the difference in contact angle between mesh sizes and sample surfaces was relatively small. Without an epoxy resin pre-curing layer, directly spraying a hydrophobic HD / KH570 / SiO2 solution onto the carbon nanotube film would not sustain a single friction cycle, and the superhydrophobic layer on the surface would peel off. Figure 11 The image shows a comparison of the wear resistance of the original film without an epoxy resin layer and the film with an epoxy resin layer. The left image shows the original film with an epoxy resin layer in the middle, which still maintains its surface integrity after friction cycles. The right image shows the original film without an epoxy resin layer, where the hydrophobic layer on the surface is almost completely removed after friction.

[0043] Figure 7 This is a schematic diagram of the conductivity of the conductive and durable carbon nanotube film prepared in Example 1. A small light bulb and the prepared conductive and durable carbon nanotube film are connected by a 3V direct power supply. The light bulb has normal brightness, indicating that the sample can still maintain good conductivity after the surface is bonded with epoxy resin and is superhydrophobic.

[0044] Example 2

[0045] Example 2 investigated the effect of the pre-curing time of the epoxy resin layer coated on the carbon nanotube film in step five on the wear resistance. Specifically, the pre-curing time of the epoxy resin was adjusted to 0 min, 10 min, 15 min, 20 min, and 30 min, respectively, while other conditions were the same as in Example 1.

[0046] like Figure 8 The five sets of samples shown below underwent friction testing. 1000-grit sandpaper was used, and a 100g weight was applied, with each cycle lasting 30cm. The surface contact angle was measured after five cycles.

[0047] from Figure 9 It can be seen that the uncured sample, i.e., the sample with a pre-curing time of 0 min, cannot achieve a superhydrophobic surface and therefore does not meet the requirements for superhydrophobicity. This demonstrates the crucial role of the epoxy resin layer in constructing the superhydrophobic surface. For the sample with a pre-curing time of 10 min, the contact angle, as shown in the figure, generally ranges from 156°±2°, remaining relatively constant. For the sample with a pre-curing time of 15 min, the contact angle is similar to that of the 10-min pre-curing sample, remaining relatively constant. For the sample with a pre-curing time of 20 min, the contact angle is similar to that of the 10-min and 15-min pre-curing samples, showing a trend towards stability and remaining relatively constant. For the sample with a pre-curing time of 30 min, the contact angle is best before the friction test, reaching 158°±2°. However, after the friction test, the surface contact angle decreases sharply, indicating a deterioration in the mechanical stability of the hydrophobic effect.

[0048] Under more stringent abrasion resistance cycles, i.e., friction tests, the sample was subjected to friction under 800-grit sandpaper, with a friction length of 30cm per cycle. A 200g weight was added to the surface for further friction. The sample was then subjected to 100 cycles, and the results are shown below. Figure 10 Further research was conducted on the effects of epoxy resin pre-curing for 10 min, 15 min, and 20 min on wear resistance. Samples pre-cured at 80℃ for 20 min maintained a good contact angle and had higher surface integrity. Therefore, samples prepared at 80℃ for 20 min showed the best performance and were the optimal parameters for epoxy resin layer as an intermediate layer.

[0049] Example 3

[0050] Example 3 investigated the effect of KH570 concentration on hydrophobic properties in step three, specifically by adjusting the KH570 concentration to 1-9 wt%, with other conditions being the same as in Example 1.

[0051] Figure 12 This graph shows the change in contact angle at different KH-570 concentrations. The right image shows actual surface contact angles at 1wt%, 3wt%, 5wt%, 7wt%, and 9wt% in sequence. As the KH-570 concentration increases (from 1wt% to 9wt%), the water contact angle initially increases and then decreases. The main reason is that when the KH-570 concentration is relatively low, a small portion of SiO2 is hydrophobically modified, and its self-agglomeration plays a dominant role. The sol particle size reaches over 200nm, resulting in poor dispersibility and only increasing surface roughness. Less low surface energy material is introduced. When the KH-570 concentration is 7wt%, the sol particle size is the smallest, and the monodispersity is best, resulting in the best hydrophobic effect. However, as the concentration further increases, excess KH-570 polymerizes, causing the nano-SiO2 particles to agglomerate. After agglomeration, some HDTMS adhering to the surface due to dehydration condensation are encapsulated, leading to a decrease in hydrophobic effect.

[0052] Example 4

[0053] Example 4 investigated the effect of HDTMS concentration on hydrophobic properties in step 3, specifically by adjusting the HDTMS concentration to 1-6 wt%, with other conditions being the same as in Example 1.

[0054] Figure 13 It can be concluded that as the concentration of HDTMS increases (from 1 wt% to 6 wt%), the water contact angle first increases and then decreases. The right figure shows the contact angles from 1 wt% to 6 wt%. This is mainly because when the concentration of HDTMS is relatively low, HDTMS can only replace some of the hydroxyl groups on KH-570. Most of the remaining hydroxyl groups will polymerize, leading to the aggregation of modified SiO2 into a three-dimensional network structure, resulting in larger sol particle size and poor dispersion. Less HDTMS is adsorbed on the surface, resulting in poor hydrophobicity. As the concentration increases, the hydroxyl groups generated after the hydrolysis of KH-570 and HDTMS undergo dehydration condensation, reducing the aggregation of modified SiO2 and improving the hydrophobic effect. When the concentration further increases, the long carbon chains in HDTMS are linked to the nano-SiO2, increasing the degree of polymerization of the modified nano-SiO2 sol, destroying the surface roughness, and worsening the hydrophobicity. In summary, the hydrophobic effect is best when the HDTMS concentration is 3 wt%.

[0055] Comparative Example 1

[0056] The durable superhydrophobic carbon nanotube thin film composite material prepared in Example 1 of CN202310731885.1 was subjected to a friction cycle test. On sandpaper, a friction length of 30 cm was defined as one friction cycle. The sample was rubbed with 800 / 1000 / 1200 grit sandpaper and a 200g weight attached to the surface. The change in contact angle after friction cycles was detected. After 30 friction cycles, the film surface was damaged and could not maintain a high contact angle for a long time, resulting in poor mechanical stability of the hydrophobic effect.

Claims

1. A method for preparing a conductive and highly wear-resistant carbon nanotube thin film, characterized in that: The preparation steps are as follows: (1) Dissolve epoxy resin and epoxy resin curing agent in solvent, perform ultrasonic treatment to form a viscous solution, coat it on carbon nanotube film for pre-curing, adjust the pre-curing temperature to 80℃, and the pre-curing time to 20min. (2) Weigh out nano-SiO2 particles and dissolve them in anhydrous ethanol, then stir ultrasonically to obtain solution A; add silane coupling agent KH-570 to a beaker of deionized water, stir ultrasonically to fully hydrolyze it, and obtain solution B; mix solution A, solution B and HDTMS, and stir the mixture at 70℃ to obtain HD / KH570 / SiO2 solution; wherein, the concentration of solution A is 0.01 g / L; solution B is obtained by adding 7 wt% silane coupling agent KH-570 to a beaker of 30 mL of deionized water per 6 mL, and then stirring ultrasonically to fully hydrolyze it; the concentration of HDTMS is 3 wt%; the volume ratio of solution A, solution B and HDTMS is 10:10:1; (3) Spray HD / KH570 / SiO2 solution onto the surface of the carbon nanotube film after pre-curing in step (1), and then send it into an oven for curing. After curing, a conductive and wear-resistant carbon nanotube film is obtained.

2. The method for preparing conductive and highly wear-resistant carbon nanotube thin films according to claim 1, characterized in that: The epoxy resin curing agent is T-31; the mass ratio of epoxy resin to curing agent is 4:

1.

3. The method for preparing conductive and highly wear-resistant carbon nanotube thin films according to claim 1, characterized in that: The amount of epoxy resin viscous solution used in carbon nanotube films is: 1-2 ml of epoxy resin viscous solution is applied to every 5*5 cm carbon nanotube film.

4. The method for preparing conductive and highly wear-resistant carbon nanotube thin films according to claim 1, characterized in that: The relative amount of HD / KH570 / SiO2 solution used in the pre-cured carbon nanotube film is: 3 ml of HD / KH570 / SiO2 solution is coated on the surface of each 5*5 cm carbon nanotube film.

5. The method for preparing conductive and highly wear-resistant carbon nanotube thin films according to claim 1, characterized in that: The curing temperature in step (3) is 80℃ and the curing time is 6h.

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