A method for preparing a flexible coating layer using terbium-carbon nanotube co-doped cyanate ester

Abstract

This invention discloses a method for preparing a flexurally resistant coating using terbium-carbon nanotube co-doped cyanate, comprising the following steps: (1) dissolving terbium salt in anhydrous ethanol, and then adding an organic compatibilizer to prepare a modified terbium solution; (2) adding electrochemically de-zipped carbon nanotubes (uCNTs) to the modified terbium solution for ultrasonic dispersion, and drying to obtain Tb 3+ -uCNTs nanofillers; (3) Tb nanofillers 3+ -uCNTs are added to the cyanate ester resin matrix and mechanically stirred until homogeneous to obtain Tb. 3+ A terbium-modified cyanate ester resin-based coating is uniformly coated onto tinplate and cured at temperature gradients of 100℃ / 130℃ / 150℃ / 180℃ / 210℃. This invention involves the reaction of terbium salts with unzipped carbon nanotubes under the action of a compatibilizer. This effectively transfers some surface energy, preventing the unzipped carbon nanotubes from agglomerating into bundles, strengthening the interfacial bonding between the carbon nanotubes and the substrate, and thus improving the flexural resistance of the composite coating.

Description

Technical Field

[0001] This invention belongs to the field of interface modification of composite materials, specifically involving unzipped carbon nanotubes (uCNTs) and Tb 3+ Preparation method of -uCNTs modified cyanate ester resin-based nanocomposite coating. Background Technology

[0002] Cyanate ester resins (CERs) are widely used in adhesives, building materials, composite materials, laminates, and coatings due to their excellent mechanical properties, heat resistance, ease of processing, good adhesion to many substrates, and good chemical resistance. However, the high brittleness, poor flexibility, and poor fatigue resistance of their cured products greatly limit their further applications. To overcome these shortcomings, cyanate ester resins need to be modified.

[0003] In recent years, numerous scholars at home and abroad have conducted extensive research. Among them, carbon nanotubes, as a novel nanomaterial, have excellent properties such as low density, large aspect ratio, high strength and high toughness. Even with a small amount of addition, they can significantly improve the mechanical properties of cyanate ester resins. Therefore, carbon nanotubes are considered an ideal reinforcement for composite materials and are expected to be used to strengthen polymer matrices and thus improve their performance.

[0004] Rare earth (RE) elements are hailed as strategic elements of the 21st century and have attracted widespread attention in the field of photoluminescence. RE atoms possess more electron orbitals, and their inner protons have a stronger attraction to electrons, thus attracting outer electrons from carbon nanotubes to form stable coordination bonds. Introducing these bonds into carbon nanotubes can effectively reduce their surface energy, improve their dispersion in cyanate ester resin matrices, and form stronger interfacial bonds, thereby enhancing the mechanical properties of composite coatings. This method shows great potential in the field of interfacial bonding of composite materials. However, to date, many problems in this area remain unsolved. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a method for preparing a flexurally resistant coating using terbium-carbon nanotube co-doped cyanate ester.

[0006] To achieve the objective, the technical solution provided by this invention is as follows:

[0007] A method for preparing a flexurally resistant coating using terbium-carbon nanotube co-doped cyanate, the method comprising the following specific steps:

[0008] (1) Dispersible terbium modifier obtained by mixing terbium salt and cosolvent: Prepare the first cosolvent, add the terbium salt solution and the second cosolvent to it in sequence; adjust the pH value to about 6-7 with dilute ammonia water, stir thoroughly, and obtain Tb 3+-(First co-solvent) n (Second co-solvent) m A ternary modified terbium solution, wherein n,m=1,2,3;

[0009] (2) Disperse uCNTs in a suitable solvent, add modified terbium solution, add dilute ammonia to adjust the pH to about 6-7, stir thoroughly, filter and wash with a large amount of solvent, dry and collect to obtain Tb. 3+ -uCNTs;

[0010] (3) Prepare Tb 3+ -uCNTs were dispersed in a suitable solvent, and an appropriate amount of cyanate ester resin was added and mechanically stirred. The mixture was then coated onto a planar substrate and placed in an oven to cure under a specific temperature gradient for a set time, thus obtaining a nanocomposite coating Tb. 3+ -uCNTs / CER.

[0011] In the method described above, step 1) involves using an electrochemical method to de-zip the carbon nanotubes, thereby disrupting and functionalizing their surface structure. A titanium sheet is used as the electrode material, with the carbon nanotubes loaded on the anode. A DC current of 20–50V is applied to the system, and the carbon nanotubes are electrochemically treated for 2–8 hours. The purity of the titanium sheet electrode used to address the nanopore defects on the prepared carbon nanotubes is 90.00–99.99%, and the concentration of sulfuric acid in the electrolyte is 40–98%.

[0012] In the method described in step (1), the first cosolvent and the second cosolvent are selected from ethanol solutions of the following substances: PP-g-GMA (glyceryl ester grafted polypropylene), p-BBA (4-benzoylbenzoic acid), ADR (2,3-glycidyl methacrylate), DBM (dibenzoylmethane), MAA (α-methacrylic acid); with a concentration of 0.1-0.3M.

[0013] In the method described in step (2), the ratio of uCNTs to anhydrous ethanol is 5-15 mg: 10-30 ml, the concentration of dilute ammonia water used is 0.2-2 mol / L, the concentration of TbCl3·6H2O solution is 0.1-0.3 mol / L, and the molar ratio of TbCl3·6H2O to the two organic cosolvents is 0.5-2: 0.5-2: 0.5-2.

[0014] The cyanate resin in step (4) of the method is bisphenol A cyanate, bisphenol E cyanate, bisphenol f cyanate, etc.

[0015] The curing reaction in step (4) of the method is a step-by-step curing process. The curing temperature in the first stage is 90-110℃ and the time is 1-5h; the curing temperature in the second stage is 100-150℃ and the time is 1-5h; the curing temperature in the third stage is 130-180℃ and the time is 1-5h; and the curing temperature in the fourth stage is 150-230℃ and the time is 1-5h.

[0016] In the method described, in step (3), Tb 3+ The addition amount of -uCNTs in cyanate ester resin is 0.1-1 wt%.

[0017] The coating performance analysis was conducted according to GB / T 6742-86 "Bending Test of Paint Film (Cylindrical Shaft)" and GB / T 9286-1998 "Cross-cut Test of Paint Films and Varnishes" to test the flexibility and adhesion of the coating.

[0018] The present invention, after adopting the above technical solution, has the following beneficial effects: (1) The preparation method of the composite coating of terbium modified by the compatibilizer and the decosulated carbon nanotubes modified by the present invention is simple to operate and highly efficient. (2) The nano-decosulated carbon nanotubes of the present invention introduce a pore defect structure in the tube wall, which effectively improves their tendency to agglomerate into bundles and enhances the interfacial bonding force and compatibility with the cyanate resin matrix. (3) The addition of the cosolvent makes Tb 3+ Encapsulated by organic co-solvents, the polarity increases, allowing it to be uniformly dispersed on the surface of carbon nanotubes, enhancing charge interaction and making the connection more stable; (4) After being doped with modified terbium, the surface energy of carbon nanotubes is reduced, improving their dispersibility. The presence of modified terbium effectively transfers the stress applied to the cyanate ester resin matrix, improving the mechanical properties of the polymer after curing. The bending flexibility of the prepared composite coating was tested by a paint film bending tester. The ultimate bending diameter was reduced to 6-10 mm compared with pure cyanate ester resin. The adhesion grade reached 3-5B. Attached Figure Description

[0019] Figure 1 Tb of the present invention 3+ A flowchart of the preparation method of -MWCNTs modified cyanate ester resin-based nanocomposites.

[0020] Figure 2 TEM images of CNTs (a) and uCNTs (b).

[0021] Figure 3 For CNTs, uCNTs, Tb 3+ -CNTs and Tb 3+ Infrared spectrum of -uCNTs.

[0022] Figure 4 For Tb3+ -CNT(a) and Tb 3+ TEM images of Tb-CNTs(b); a, b are transmission electron micrographs of Tb-CNTs and Tb-UCNTs with added compatibilizers; c, d are transmission electron micrographs of Tb-CNTs and Tb-UCNTs without added compatibilizers.

[0023] Figure 5 For Tb 3+ -CNTs / CER and Tb 3+ - Bending diameter curve of uCNTs / CER composite coating. Detailed Implementation

[0024] The present invention will be described in detail below with reference to specific embodiments.

[0025] Example 1: Preparation of unzipped carbon nanotubes (uCNTs):

[0026] Weigh 1000 mg of carbon nanotubes with an outer diameter of 20–30 nm, an inner diameter of 8–15 nm, and a length of 10–30 μm. Spread these evenly on a 10 cm × 10 cm titanium sheet with a purity of 90%. Cover the titanium sheet with a PTFE film. Then, overlap another 10 cm × 10 cm 90% pure titanium sheet with the carbon nanotube-loaded sheet. Place 30 ml of distilled water in a 250 ml glass beaker, and slowly add 70 ml of 98% sulfuric acid while stirring to prepare approximately 100 ml of a 70% sulfuric acid solution. After the 70% sulfuric acid has cooled, pour it into a 15 cm diameter petri dish, and then immerse the overlapped titanium sheet completely. Connect the positive terminal of a power supply to the titanium sheet with the carbon nanotubes and the negative terminal to the other titanium sheet. Apply a 15 V DC current to the entire circuit and maintain this voltage for 4 hours. The treated carbon nanotubes were washed with distilled water until pH=7, then filtered, and vacuum dried at 80℃ for 12h to obtain uCNTs. Figure 2 The images are TEM images of CNT(a) and uCNT(b). It can be seen that after the electrochemical unzipping treatment, the surface of uCNT becomes very rough, and more defects are generated.

[0027] Example 2: Tb 3+ -CNTs and Tb 3+ Preparation of -uCNTs:

[0028] (1) Add 2 ml of 0.1 mol / L ADR (2,3-methacrylate glycidyl ester) ethanol solution to an Erlenmeyer flask and stir for 2 h. Then add 2 ml of 0.1 M TbCl3·6H2O ethanol solution and 2 ml of 0.3 M p-BBA ethanol solution in sequence. After stirring for 10 min, adjust the pH value to about 6-7 with 1 mol / L dilute ammonia water and stir thoroughly for 5 h to prepare a modified terbium solution.

[0029] (2) Disperse 0.01g of CNTs and uCNTs separately in 20ml of anhydrous ethanol, sonicate until uniform, add 6ml of the modified terbium solution prepared in (1), and stir for 5h. Wash and filter with a large amount of anhydrous ethanol, dry and collect Tb. 3+ -CNTs and Tb 3+ -uCNTs. Figure 3 Display CNTs, uCNTs, Tb 3+ -CNTs and Tb 3+ The infrared spectrum of -uCNTs shows that Tb 3+ -CNTs and Tb 3+ Tb was found in -uCNTs 3+ The bond with O appears at 800 cm. -1 The presence of terbium nearby indicates that the combination of modified terbium and CNTs generates a novel nano-hybrid material. Figure 4 Tb 3+ -CNTs and Tb 3+ HRTEM images of -uCNTs show that the modified terbium has an irregular spherical structure and is successfully linked to the sidewalls of CNTs.

[0030] Tb prepared in Example 2 3+ -uCNTs solid powder was used in the preparation of the following Examples 3-7:

[0031] Example 3:

[0032] Take 0.10g Tb 3+ -uCNTs were dispersed in DMF solvent, and 10g of bisphenol E cyanate resin was added and mechanically stirred. The mixture was then coated onto tinplate and placed in an oven for curing at a temperature gradient of 100℃ for 2 hours, 130℃ for 1 hour, 150℃ for 1 hour, 180℃ for 1 hour, and 210℃ for 1 hour to obtain Tb. 3+ -uCNTs / CER@1.0%.

[0033] Example 4:

[0034] Take 0.08g Tb 3+-uCNTs were dispersed in acetone solvent, and 10g of bisphenol E cyanate resin was added. The mixture was then coated onto tinplate and placed in an oven for curing at a temperature gradient of 100℃ for 2 hours, 130℃ for 1 hour, 150℃ for 1 hour, 180℃ for 1 hour, and 210℃ for 1 hour. After natural cooling, Tb was obtained. 3+ -uCNTs / CER@0.8%.

[0035] Example 5:

[0036] Take 0.06g Tb 3+ -uCNTs were dispersed in DMF solvent, and 10g of cyanate ester resin was added and mechanically stirred. The mixture was then placed in an oven and cured using a temperature gradient of 100℃ for 2h, 130℃ for 1h, 150℃ for 1h, 180℃ for 1h, and 210℃ for 1h to obtain Tb. 3+ -uCNTs / CER@0.6%.

[0037] Example 6:

[0038] Take 0.04g Tb 3+ -uCNTs were dispersed in DMF solvent, and 10g of cyanate ester resin was added and mechanically stirred. The mixture was then placed in an oven and cured using a temperature gradient of 100℃ for 2h, 130℃ for 1h, 150℃ for 1h, 180℃ for 1h, and 210℃ for 1h to obtain Tb. 3+ -uCNTs / CER@0.4%.

[0039] Example 7:

[0040] Take 0.020g Tb 3+ -uCNTs were dispersed in acetone solvent, and 10g of cyanate ester resin was added and mechanically stirred. The mixture was then coated onto tinplate and placed in an oven to cure under a temperature gradient of 100℃ for 2 hours, 130℃ for 1 hour, 150℃ for 1 hour, 180℃ for 1 hour, and 210℃ for 1 hour. After natural cooling, the mixture was demolded to obtain Tb. 3+ -uCNTs / CER@0.2%. Figure 5 Tb with added cosolvent 3+ -uCNTs / CER and Tb 3+- When the filler content of CNTs / CER is 0.6 wt%, the bending diameter reaches its minimum, reaching 6 mm and 8 mm respectively. This is because the adhesion of modified terbium increases the oxygen-containing functional groups of carbon nanotubes, enhances their activity, and strengthens their connection with the resin matrix. This allows the carbon nanotubes to absorb part of the force during bending fracture of the coating, increasing the coating's bending toughness. When the filler content exceeds 0.6 wt%, the dispersion of carbon nanotubes in the matrix deteriorates, reducing the coating's bending toughness. As shown in Table 1, the impact strength reaches its maximum when the filler content is 0.6 wt%, because at this concentration, the dispersion of carbon nanotubes is best, resulting in the optimal reinforcing effect on the resin matrix.

[0041] Table 1 Tb 3+ -CNTs / CER and Tb 3+ -uCNTs / CER composite coating adhesion rating table

[0042]

[0043]

[0044] Comparative Example 1: No cosolvent Tb added 3+ -CNTs / CER composite coating:

[0045] (1) Add 2 ml of 0.1 M TbCl3·6H2O solution to the conical flask, stir for 10 min, then adjust the pH value to about 6-7 with 1 mol / L dilute ammonia water, stir thoroughly for 5 h to prepare a Tb3+ solution.

[0046] (2) Disperse 0.01g of CNTs in 20ml of anhydrous ethanol, sonicate until uniform, and add the Tb prepared in (1). 3+ The solution was stirred for 5 hours. It was then washed with a large amount of anhydrous ethanol, filtered, dried, and the Tb was collected. 3+ -CNTs.

[0047] (3) Take 0.10g, 0.02g, 0.06g, and 0.08g of Tb respectively. 3+ -CNTs were dispersed in DMF solvent, and 10g of cyanate ester resin was added and mechanically stirred. The mixture was then coated onto tinplate and placed in an oven for curing at a temperature gradient of 100℃ for 2 hours, 130℃ for 1 hour, 150℃ for 1 hour, 180℃ for 1 hour, and 210℃ for 1 hour to obtain Tb. 3+ -CNTs / CER

[0048] Comparative Example 2: No cosolvent Tb added 3+ -uCNTs / CER composite coating:

[0049] (1) Add 2 ml of 0.1 M TbCl3·6H2O solution to an Erlenmeyer flask, stir for 10 min, then adjust the pH to about 6-7 with 1 mol / L dilute ammonia solution, stir thoroughly for 5 h, and prepare TbCl3·6H2O solution. 3+ Solution.

[0050] (2) Disperse 0.01g uCNTs in 20ml DMF, sonicate until uniform, and add the modified Tb prepared in (1). 3+ The solution was stirred for 5 hours. After washing with a large amount of DMF and filtration, the solution was dried and Tb was collected. 3+ -uCNTs.

[0051] (3) Take 0.10g, 0.02g, 0.06g and 0.08g of Tb-uCNTs respectively and disperse them in acetone solvent. Add 10g of cyanate ester resin and stir mechanically. Then coat it on tinplate and put it in an oven to cure and form Tb-uCNTs / CER by temperature gradient reaction at 100℃ for 2h, 130℃ for 1h, 150℃ for 1h, 180℃ for 1h and 210℃ for 1h.

[0052] Comparative Example 3: Cyanate ester resin-based composite material without added CNTs:

[0053] Take 10g of cyanate ester resin, coat it onto tinplate, and place it in an oven to cure it at a temperature gradient of 100℃ for 2h, 130℃ for 1h, 150℃ for 1h, 180℃ for 1h, and 210℃ for 1h to obtain Pure CER.

[0054] It should be understood that those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A method for preparing a flexurally resistant coating using terbium-carbon nanotube co-doped cyanate, characterized in that, Includes the following steps: (1) Dispersible terbium modifier obtained by mixing terbium salt and co-solvent: Prepare the first co-solvent, add the terbium salt solution and the second co-solvent to it in sequence; adjust the pH value to 6-7 with dilute ammonia water, stir thoroughly, and obtain Tb 3+ - (First cosolvent) n (Second cosolvent) m The ternary modified terbium solution, wherein n, m = 1, 2, 3; the first co-solvent and the second co-solvent are selected from ethanol solutions of the following substances: 4-benzoylbenzoic acid (p-BBA), dibenzoylmethane (DBM), α-methacrylic acid (MAA), with a concentration of 0.1-0.3M; (2) Disperse uCNTs in a suitable solvent, add the ternary modified terbium solution, add dilute ammonia to adjust the pH to 6-7, stir thoroughly, filter and wash with a large amount of solvent, dry and collect to obtain Tb. 3+ -uCNTs; (3) Prepare Tb 3+ -uCNTs were dispersed in a suitable solvent, and an appropriate amount of cyanate ester resin was added and mechanically stirred. The mixture was then coated onto a planar substrate and placed in an oven to cure under a specific temperature gradient for a set time, thus obtaining a nanocomposite coating Tb. 3+ -uCNTs / CER;Tb 3+ The addition amount of -uCNTs in the cyanate ester resin is 0.2-0.6 wt%. The curing reaction is a stepwise curing process: the first stage curing temperature is 90-110 ℃, and the time is 1-5 h; the second stage curing temperature is 100-150 ℃, and the time is 1-5 h; the third stage curing temperature is 130-180 ℃, and the time is 1-5 h; the fourth stage curing temperature is 150-230 ℃, and the time is 1-5 h.

2. The method as described in claim 1, characterized in that, In step 2), carbon nanotubes are subjected to an electrochemical process to de-zip and disrupt and functionalize their surface structure. A titanium sheet is used as the electrode material, and the carbon nanotubes are loaded onto the anode. A DC current of 20-50V is applied to the system, and the carbon nanotubes are electrochemically treated for 2-8 hours. The purity of the titanium sheet electrode used is 90.00-99.99%, and the concentration of sulfuric acid in the electrolyte is 40-98%.

3. The method according to claim 1, characterized in that, In step (2), uCNTs are dispersed in anhydrous ethanol, and the ratio of uCNTs to anhydrous ethanol is 5-15 mg: 10-30 ml, and the concentration of dilute ammonia water used is 0.2-2 mol / L.

4. The method according to claim 1, characterized in that, The cyanate resin mentioned in step (3) is bisphenol A cyanate, bisphenol E cyanate or bisphenol f cyanate.

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