Layered heterojunction filler modified polyimide coating material as well as preparation method and application thereof

Abstract

The invention provides a layered heterojunction filler modified polyimide coating material as well as a preparation method and application thereof, and belongs to the technical field of anti-corrosion and wear-resistant coatings. Graphite phase carbon nitride, Bi salt and Cl salt are adopted to construct a BiOCl (at) g-C3N4 heterojunction composite material, then the BiOCl (at) g-C3N4 heterojunction composite material is compounded with polyimide to obtain a polyimide coating material, and the self-lubrication and wear resistance of the polyimide composite coating can be improved through construction of the bismuth oxychloride and the graphite phase carbon nitride layered heterojunction BiOCl (at) g-C3N4. Meanwhile, due to the construction of a heterostructure, the ion transmission path can be increased, and the corrosion resistance of the polyimide coating is further improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of corrosion and wear resistant coating, in particular to a layered heterojunction filler modified polyimide coating material and a preparation method and application thereof. BACKGROUND

[0002] Polymer-based composite coatings play an important role in modern industrial applications, especially in corrosion, low friction and oil-free environments, with excellent performance. Polyimide (PI) is widely used in the preparation of wear-resistant and corrosion-resistant composite coatings due to its good thermal stability, self-lubricating properties and chemical corrosion resistance.

[0003] However, although PI coating has shown excellent performance in many industrial applications, it still faces several challenges in the technical field. The inherent low friction coefficient and good chemical corrosion resistance of PI make it advantageous in the fields of self-lubrication and corrosion protection, but its mechanical properties are relatively poor, especially its insufficient wear resistance, which affects the service life and reliability of the overall material. Therefore, it is necessary to modify it to improve the wear resistance and corrosion resistance of the polyimide composite coating and prolong its service life. Adding fibers or nanofillers to the matrix is an effective means to improve the wear resistance and corrosion resistance of the polyimide composite coating. However, the required content of fibers in the modification process is high, resulting in increased modification cost. Although a small amount of nanofiller can significantly improve the wear resistance and corrosion resistance of the polyimide composite coating, the agglomeration of nanofillers in the polymer matrix limits the improvement of the performance of the polyimide composite coating. SUMMARY

[0004] The purpose of the present application is to provide a layered heterojunction filler modified polyimide coating material and a preparation method and application thereof. By constructing a heterostructure nanocomposite, the agglomeration of nanomaterials can be significantly improved, and the wear resistance and corrosion resistance of the polyimide coating can be improved.

[0005] In order to achieve the above-mentioned purpose of the application, the present application provides the following technical solutions: The present application provides a preparation method of a layered heterojunction filler modified polyimide coating material, comprising the following steps: Melamine is calcined to obtain g-C3N4; The g-C3N4 is mixed with Bi salt, organic solvent and Cl-containing salt solution to perform solvothermal reaction to obtain BiOCl@g-C3N4; The BiOCl@g-C3N4 is mixed with polyimide to obtain a layered heterojunction filler modified polyimide coating material.

[0006] Preferably, the calcination temperature is 520-560℃, and the holding time is 1-2h.

[0007] Preferably, the Bi salt comprises bismuth nitrate, bismuth carbonate or bismuth phosphate; the molar ratio of g-C3N4 to Bi salt is 1:0.5~2.

[0008] Preferably, the Cl salt in the Cl salt solution comprises NaCl, KCl or CaCl2; the molar ratio of Bi salt to Cl salt is 1:1~2.

[0009] Preferably, the organic solvent comprises ethylene glycol and acetic acid; the volume ratio of ethylene glycol to acetic acid is 1:1~2.

[0010] Preferably, the temperature of the solvothermal reaction is 100~150℃, and the time is 3~6h.

[0011] Preferably, the mass ratio of BiOCl@g-C3N4 to polyimide is 0.005~0.2:1.

[0012] Preferably, the raw materials for preparing the polyimide comprise diamine and dianhydride; the diamine comprises p-phenylenediamine (PDA) or 4,4'-diamino diphenyl ether (ODA), and the dianhydride comprises hexafluoro dianhydride (6FDA) or 4,4'-diphenyl ether dianhydride; the molar ratio of diamine to dianhydride is 1:1~2.

[0013] The application provides a layered heterojunction filler modified polyimide coating material prepared by the preparation method.

[0014] The application provides an application of the layered heterojunction filler modified polyimide coating material in the fields of self-lubrication and corrosion prevention.

[0015] The application provides a preparation method of a layered heterojunction filler modified polyimide coating material, wherein the construction of the layered heterojunction BiOCl@g-C3N4 of bismuth oxychloride and graphite phase carbon nitride can improve the self-lubrication and wear resistance of the polyimide composite coating. The layers are connected by weak van der Waals forces, which has good lubricating effect in the friction process. In the process of relative sliding between the metal friction pair and the polymer matrix, a large number of positive charges are easily accumulated on the surface of the metal friction pair, so that the electronegative substances are easily adsorbed by the metal friction pair. The BiOCl with the layered structure of cation and anion is easily adsorbed on the surface of the metal friction pair, and helps to improve the stability of the transfer film and the wear resistance of the polymer composite. In the present application, the heterojunction BiOCl@g-C3N4 is constructed, on the one hand, g-C3N4 and BiOCl synergistically promote the formation of the transfer film, and then improve the wear resistance of the PI composite material. On the other hand, BiOCl can effectively inhibit the three-body wear of g-C3N4 to the PI composite material. At the same time, the heterojunction BiOCl@g-C3N4 can further improve the corrosion resistance of the polyimide coating. The g-C3N4 with good chemical inertness can improve the corrosion of the polyimide. The g-C3N4 two-dimensional material can prolong the migration path of corrosion ions such as chloride ions in the polyimide matrix, and then improve the corrosion resistance of the polyimide composite coating. The heterostructure can further prolong the migration path of chloride ions, so as to further improve the corrosion resistance of the polyimide composite coating. Therefore, the heterojunction BiOCl@g-C3N4 can improve the wear resistance and corrosion resistance of the polyimide composite coating at the same time.

[0016] The present application can improve the wear resistance of the polyimide coating by controllable preparation of the layered heterostructure. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 The scanning electron microscope images of g-C3N4 in Example 1, BiOCl in Comparative Example 2 and different BiOCl@g-C3N4 composite materials in Examples 1-3 are shown in (a) BiOCl, (b) g-C3N4, (c) 2B1C in Example 1, (d) 1B1C in Example 2, (e) 1B2C in Example 3. Figure 2 The average friction coefficient and wear rate of the polyimide coating in Examples 1-3 and Comparative Examples 1-3 are shown in the figure. DETAILED DESCRIPTION

[0018] In the present application, the required raw materials or reagents are commercially available unless otherwise specified.

[0019] The present application provides a preparation method of a layered heterojunction filler modified polyimide coating material, comprising the following steps: Melamine is calcined to obtain g-C3N4; The g-C3N4 is mixed with Bi salt, organic solvent and Cl-containing salt solution to carry out solvothermal reaction to obtain BiOCl@g-C3N4. The BiOCl@g-C3N4 is mixed with the polyimide to obtain a layered heterojunction filler modified polyimide coating material.

[0020] In the present application, the calcination temperature is preferably 520-560℃, more preferably 530-550℃, the holding time is preferably 1-2h, more preferably 1.5-2h; the temperature rising rate to the calcination temperature is preferably 5℃ / min.

[0021] In the present application, the Bi salt includes bismuth nitrate, bismuth carbonate or bismuth phosphate; the molar ratio of g-C3N4 to Bi salt is preferably 1:0.5-2, more preferably 1:1-1.5.

[0022] In the present application, the Cl salt in the Cl salt solution preferably includes NaCl, KCl or CaCl2; the molar ratio of Bi salt to Cl salt is preferably 1:1-2, more preferably 1:1-1.5.

[0023] In the present application, 0.5-2mmol of Cl salt is dissolved in a mixture of 5mL deionized water and 5mL ethanol to obtain a Cl salt solution.

[0024] In the present application, the organic solvent includes ethylene glycol and acetic acid; the volume ratio of ethylene glycol to acetic acid is preferably 1:1-2, more preferably 1:1-1.5. The present application does not have special limitation on the amount of the organic solvent, which can be adjusted according to the requirement.

[0025] In the present application, g-C3N4 and Bi salt are dissolved in the organic solvent, stirred at room temperature for 0.5-2h (more preferably 0.5-1h), the Cl salt solution is added dropwise, stirred for 0.5h, poured into a high-pressure reaction kettle with a polytetrafluoroethylene liner, and subjected to a solvothermal reaction.

[0026] In the present application, the temperature of the solvothermal reaction is preferably 100-150℃, more preferably 120-130℃, and the time is preferably 3-6h, more preferably 4-5h.

[0027] After the solvothermal reaction is completed, the obtained solution is centrifuged and washed with deionized water and ethanol, and the obtained product is placed in a 60℃ oven and dried for 15-30h (more preferably 18-24h) to obtain layered heterojunction BiOCl@g-C3N4.

[0028] The layered heterojunction BiOCl@g-C3N4 prepared in the present application uses graphite phase carbon nitride (g-C3N4) as a template and bismuth oxychloride (BiOCl) as a growth sheet material.

[0029] In the present application, the mass ratio of BiOCl@g-C3N4 to polyimide is preferably 0.005-0.2:1, more preferably 0.01-0.1:1, and further preferably 0.02-0.05:1.

[0030] In the present application, the raw materials for preparing the polyimide preferably include diamine and dianhydride; the diamine preferably includes p-phenylenediamine (PDA) or 4,4'-oxydianiline (ODA), and more preferably 4,4'-oxydianiline (ODA); the dianhydride preferably includes hexafluorodiphthalic anhydride (6FDA) or 4,4'-oxydiphthalic anhydride, and more preferably hexafluorodiphthalic anhydride (6FDA); and the molar ratio of the diamine to the dianhydride is preferably 1:1-2, and more preferably 1:1-1.5.

[0031] The present application does not have special limitations on the specific preparation method of the polyimide, and the polyimide can be prepared according to the methods well known in the art; in the embodiments of the present application, the diamine is dissolved in N-methylpyrrolidone (NMP), the dianhydride is added under a nitrogen atmosphere, and the mixture is stirred for 24 h to obtain a polyamic acid (PAA) solution; toluene is added to the PAA solution, and the mixture is stirred at 180°C for 8 h to obtain a polyimide (PI) solution; the PI solution is stirred into a filament in an ethanol solution, and the filament is dried at 120°C for 24 h to obtain a solid polyimide.

[0032] The present application does not have special limitations on the mixing conditions of the BiOCl@g-C3N4 and the polyimide, and the materials can be uniformly mixed.

[0033] The present application provides a layered heterojunction filler modified polyimide coating material prepared by the preparation method described in the above technical solution.

[0034] The present application provides an application of the layered heterojunction filler modified polyimide coating material described in the above technical solution in the fields of self-lubrication and corrosion prevention.

[0035] The present application preferably dissolves the layered heterojunction filler modified polyimide coating material in NMP, stirs the mixture at room temperature for 24 h to obtain a coating liquid, coats the coating liquid on a metal substrate to be protected, cures the coating liquid at 80°C for 24 h, cools the coating liquid to ambient temperature, and obtains a corrosion-resistant organic coating. The present application does not have special limitations on the coating amount of the coating, and the coating amount can be adjusted according to requirements.

[0036] The present application does not have special limitations on the type of the metal substrate to be protected, and the corresponding substrates well known in the art can be used, such as steel materials or metal materials such as iron, copper, and aluminum.

[0037] The specific embodiments of the present application are described in detail below, but it should be understood that the scope of protection of the present application is not limited by the specific embodiments. Based on the examples in the present application, all other examples obtained by those of ordinary skill in the art without creative labor are within the scope of protection of the present application.

[0038] The experimental methods described in the embodiments of the present application are all conventional methods unless otherwise specified; the reagents and raw materials described below are all commercially available unless otherwise specified.

[0039] Example 1

[0040] 1) Synthesis of layered heterojunction BiOCl@g-C3N4: 1.1) Synthesis of template g-C3N4: weigh 3 g of melamine and place it in a ceramic crucible, with a temperature rise rate of 5 ℃ / min, heat at a temperature of 550 ℃ for 2 h to obtain g-C3N4; 1.2) Synthesis of layered heterojunction BiOCl@g-C3N4: Dissolve 1 mmol of NaCl in 5 mL of deionized water and 5 mL of ethanol to obtain a NaCl solution; Dissolve 0.5 mmol of g-C3N4 and 1 mmol of Bi(NO3)3·5H2O in a mixed solution of 5 mL of ethylene glycol and 5 mL of acetic acid, stir at room temperature for 0.5 h, add the NaCl solution to the above mixed solution, stir for 0.5 h, pour into a polytetrafluoroethylene-lined high-pressure reaction kettle, and heat at 120 ℃ for 6 h. After the reaction is completed, the obtained solution is centrifuged and washed with deionized water and ethanol. The obtained product is placed in an oven at 60 ℃ and dried for 24 h to obtain a BiOCl@g-C3N4 heterojunction composite, which is named 2B1C; 2) Synthesis of polyimide matrix: dissolve 10.01 g of 4,4'-diamino diphenyl ether (ODA) in 235 mL of N-methyl pyrrolidone (NMP), then add 22.16 g of hexafluoro dianhydride (6FDA) under a nitrogen atmosphere, stir for 24 h to form a polyamic acid (PAA) solution, add 80 mL of toluene to the PAA solution, and stir at 180 ℃ for 8 h to obtain a polyimide (PI) solution. Stir the PI solution into a filament in an ethanol solution and dry at 120 ℃ for 24 h to obtain a solid PI; 3) Preparation of layered heterojunction polyimide coating: dissolve 0.01 g of BiOCl@g-C3N4 and 1 g of polyimide in 8 g of NMP, stir at room temperature for 24 h to obtain a coating solution.

[0041] The 2 mL coating solution was coated on a commercially available GCr15 steel circular substrate with a diameter of 4.5 cm, cured at 80 °C for 24 h, cooled to ambient temperature to obtain a layered heterojunction filler modified polyimide coating, named 2B1C / PI.

[0042] Example 2

[0043] The difference from Example 1 is only that in step 1.2), the amount of g-C3N4 added is 1 mmol, The obtained BiOCl@g-C3N4 heterojunction composite material is named 1B1C; The obtained layered heterojunction filler modified polyimide coating is named 1B1C / PI.

[0044] Example 3

[0045] The difference from Example 1 is only that in step 1.2), the amount of g-C3N4 added is 2 mmol, and the obtained BiOCl@g-C3N4 heterojunction composite material is named 1B2C; The obtained layered heterojunction filler modified polyimide coating is named 1B2C / PI.

[0046] Comparative Example 1

[0047] The difference from Example 1 is only that BiOCl@g-C3N4 is not added, and only polyimide is used, and the obtained polyimide coating is named PI.

[0048] Comparative Example 2

[0049] The difference from Example 1 is only that in step 1.2), g-C3N4 is not added, BiOCl is prepared according to the method of Example 1, and only BiOCl and polyimide are used, and the obtained polyimide coating is named BiOCl / PI.

[0050] Comparative Example 3

[0051] The difference from Example 1 is only that BiOCl is not prepared, and only g-C3N4 is mixed with polyimide, and the obtained polyimide coating is named g-C3N4 / PI.

[0052] Characterization and performance test

[0053] 1) Figure 1 The scanning electron microscope images of g-C3N4 in Example 1, BiOCl in Comparative Example 2, and different BiOCl@g-C3N4 composite materials in Examples 1-3, (a) is BiOCl, (b) is g-C3N4, (c) is 2B1C in Example 1, (d) is 1B1C in Example 2, and (e) is 1B2C in Example 3. From the images, it can be seen that the BiOCl is a hexagonal flake structure, the g-C3N4 is a sheet structure, and the BiOCl@g-C3N4 composite material is a layered structure. Figure 1It can be seen that (a) shows that the grain size of BiOCl nanosheet is about 200 nm, and the thickness is about 50 nm. (b) shows that the grain size of g-C3N4 is above 1 μm. In (c-e), BiOCl grows on g-C3N4 and constitutes BiOCl@ g-C3N4 micro-nano structure composite material, and with the increase of the amount of substance of BiOCl, the area covered on g-C3N4 is larger.

[0054] 2) The tribological properties of polyimide and its composite coating were tested by ball-on-disc rotary friction method, the load was set to 500 g, the rotation speed was 200 rpm, and the friction radius was 10 mm, and the results are shown in Figure 2 .

[0055] Figure 2 The average friction coefficient and wear rate of the polyimide coating in Examples 1-3 and Comparative Examples 1-3 are shown in the graph; from Figure 2 It can be seen that compared with pure PI, the wear rate of g-C3N4 / PI composite material is reduced by 48.1%, and the friction coefficient is increased by 6.5%. The increase in friction coefficient may be due to the strong hydrogen bond between the graphite phase carbon nitride layers, which is not easy to slip between the layers during friction21. Compared with pure PI, the friction coefficient and wear rate of BiOCl / PI composite material are reduced by 7% and 70% respectively. In the process of constructing BiOCl@g-C3N4 composite material, the friction coefficient and wear rate of PI composite material gradually decrease with the increase of BiOCl content. Among them, the tribological properties of 1B2C / PI composite material are the best. Compared with pure PI, the friction coefficient and wear rate of 1B2C / PI composite material are reduced by 12.3% and 90.3% respectively.

[0056] 3) The anticorrosion performance of the coating was evaluated by potentiodynamic polarization test. The experiment used a three-electrode flat cell system: bare GCr15 steel and polymer coated GCr15 steel as working electrode (WE), platinum sheet with a surface area of 2×2 cm 2 as counter electrode (CE), and saturated calomel electrode (SCE) as reference electrode (RE). The electrolyte for all electrochemical tests was 3.5 wt% sodium chloride (NaCl) aqueous solution. In all tests, the exposed area of the working electrode was kept constant (9.6 cm 2 ). And the sample was immersed in the electrolyte for 60 minutes before testing to achieve a stable open circuit potential (OCP). The results of potentiodynamic polarization test are shown in Table 1.

[0057] Table 1 Corrosion potential and corrosion current density of polyimide composite coating in Examples 1-3 and Comparative Examples 1-3

[0058] As shown in Table 1, the composite coating has significant corrosion resistance in 3.5% NaCl solution; the addition of modified filler BiOCl@g-C3N4 can improve the corrosion potential of the polyimide composite coating and reduce the corrosion current density, thereby improving the corrosion resistance of the composite coating. Among them, the corrosion resistance of example 2 (1B1C / PI) is the best.

[0059] The polyimide coating of example 2 of the present application is compared with other composite coatings of the prior art, and the results are shown in Table 2.

[0060] Table 2 Comparison of corrosion potential and corrosion current density of example 2 and other composite coatings

[0061] As shown in Table 2, compared with other composite coatings, the 1B1C / PI coating in example 2 of the present application has a low corrosion potential and a low corrosion current density, indicating that it has better corrosion resistance.

[0062] The above is only the preferred embodiment of the present application, and it should be pointed out that for ordinary skilled in the art, without departing from the principles of the present application, a number of improvements and refinements can be made, and these improvements and refinements should be considered as the protection scope of the present application.

Claims

1. A method for preparing a layered heterojunction filler-modified polyimide coating material, characterized in that, Includes the following steps: Melamine was calcined to obtain g-C3N4; The g-C3N4 was mixed with Bi salt, organic solvent and Cl salt solution and subjected to solvothermal reaction to obtain BiOCl@g-C3N4; The BiOCl@g-C3N4 was mixed with polyimide to obtain a layered heterojunction filler-modified polyimide coating material.

2. The preparation method according to claim 1, characterized in that, The calcination temperature is 520~560℃, and the holding time is 1~2h.

3. The preparation method according to claim 1, characterized in that, The Bi salt includes bismuth nitrate, bismuth carbonate, or bismuth phosphate; the molar ratio of g-C3N4 to Bi salt is 1:0.5~2.

4. The preparation method according to claim 1 or 3, characterized in that, The Cl salt in the Cl-containing solution includes NaCl, KCl, or CaCl2; the molar ratio of Bi salt to Cl salt is 1:1~2.

5. The preparation method according to claim 1, characterized in that, The organic solvent includes ethylene glycol and acetic acid; the volume ratio of ethylene glycol to acetic acid is 1:1~2.

6. The preparation method according to claim 1, characterized in that, The solvothermal reaction is carried out at a temperature of 100-150°C for 3-6 hours.

7. The preparation method according to claim 1, characterized in that, The mass ratio of BiOCl@g-C3N4 to polyimide is 0.005~0.2:

1.

8. The preparation method according to claim 1 or 7, characterized in that, The raw materials for preparing the polyimide include diamine and dianhydride; the diamine includes p-phenylenediamine or 4,4'-diaminodiphenyl ether, and the dianhydride includes hexafluorodianhydride or 4,4'-biphenyl ether dianhydride; the molar ratio of the diamine to the dianhydride is 1:1~2.

9. The layered heterojunction filler-modified polyimide coating material prepared by the preparation method according to any one of claims 1 to 8.

10. The application of the layered heterojunction filler-modified polyimide coating material according to claim 9 in the fields of self-lubrication and corrosion protection.

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