Preparation method of surface conductive self-repairing coating of aluminum shielding tape

Abstract

The application discloses a preparation method of an aluminum shielding tape surface conductive self-repairing coating. First, a clean aluminum shielding tape surface is obtained through an in-situ reduction / etching pretreatment method based on an aluminum salt / fluoride salt compound solution; second, a conductive / self-repairing dual-effect enhancer is prepared and introduced into a conductive / self-repairing coating synthesized by polyether amine, diisocyanate, a multiple active amine compound, p-xylene glycol and aniline; finally, the solid content of the coating is adjusted and sprayed on the clean aluminum shielding tape surface to obtain the conductive self-repairing coating. The application converts the Al2O3 film on the aluminum surface into a new substance Al, simultaneously constructs a regular porous structure, increases the bonding strength of the film layer, improves the adaptability and self-repairing efficiency of the coating in cable manufacturing and subsequent operation through the construction of a coating with multiple dynamic hydrogen bonds and imine bond synergistic effect, and realizes good conductive enhancement effect and rapid thermal self-repairing purpose of the coating by using isocyanate modified carbon nanotubes as the enhancer.

Description

Technical Field

[0001] The invention belongs to the field of cable shielding tape protection, specifically relating to a method for preparing a conductive self-healing coating on the surface of an aluminum shielding tape. Background Technology

[0002] Shielding tape plays a crucial role in the structure of medium and low voltage cables. It evenly distributes the electric field within the cable, preventing electric field concentration within the insulation layer and thus reducing the risk of partial discharge. Simultaneously, the shielding tape effectively shields against external electromagnetic interference, preventing electromagnetic radiation from the cable's interior from interfering with external equipment and the environment, ensuring the normal operation of the cable and its surrounding equipment. Furthermore, the shielding tape increases the cable's mechanical strength and structural stability, preventing damage from external forces during laying and use, and improving the cable's durability and reliability.

[0003] Currently, commonly used cable shielding tape materials include copper foil shielding tape, aluminum foil shielding tape, tin-plated copper shielding tape, and silver-plated copper shielding tape, among which copper-based materials are more widely used in cable shielding applications. Replacing copper in cable structures with aluminum-based materials is an urgent and necessary measure.

[0004] While aluminum cable shielding tape can further meet the demand for lightweight cables, aluminum is a reactive metal that rapidly forms a dense oxide film of 0.01–0.1 micrometers thickness with oxygen in the air. This film is amorphous, porous, and has drawbacks such as poor insulation and corrosion resistance. Directly using aluminum shielding tape in cable manufacturing will inevitably cause problems such as overheating during cable operation, increased contact resistance, and reduced corrosion resistance, seriously affecting the cable's shielding performance and service life. Therefore, modifying the micro-nano structure and properties of aluminum shielding tape is a key factor in expanding its market share in the cable manufacturing field.

[0005] Chinese patent "A Conductive and Anti-corrosion Coating Process for Aluminum Flow Field Plates" (Application No.: 201710470033.6, Publication No.: CN 107425209 A, Publication Date: 2017.12.01) describes a conductive and anti-corrosion coating obtained by immersing pretreated aluminum plates in an aqueous solution of graphene oxide containing tetrahydroxyaluminate ions, followed by immersion in a sodium hypophosphite solution, washing with water, and drying at room temperature. This coating meets the requirements of high corrosion resistance, high conductivity, and low contact resistance for aluminum flow field plates in fuel cell environments. While the immersion method is simple to implement, it poses significant environmental risks. The immersion method easily generates chemical waste, increasing subsequent treatment processes and process costs. Furthermore, the coating prepared by chemical immersion in aqueous solution is relatively thin, resulting in a significant reduction in wear resistance and service life in practical applications.

[0006] Chinese patent "Conductive Anticorrosion Coating and Preparation Method and Application" (Application No.: CN202210702259.5, Application Date: 2017.12.01) can effectively improve the corrosion resistance and conductivity of the coating by combining organic titanium polymer, polyphenolic resin, toughening agent, conductive agent and curing agent. However, the filler content is relatively high in the coating, which greatly increases the cost of conductive anticorrosion coating and reduces the coating adhesion.

[0007] Chinese patent "A Method for Preparing a Conductive and Corrosion-Resistant Coating on the Surface of a Micro-arc Oxidation Layer of Magnesium Alloy" (Application No.: 202210506015.X, Application Date: 2022.05.11) reports a method for obtaining a PPy conductive material or a PPy / graphene conductive composite coating on a micro-arc oxidation surface, exhibiting good corrosion resistance and conductivity; however, its preparation steps are relatively complex. Furthermore, spin coating can only prepare coatings on simple planar sample surfaces and cannot meet the conductive protection requirements of complex structural components.

[0008] Zhang Yan et al. (Zhang Yan, Kang Hailan, Fang Qinghong. Preparation of conductive anti-corrosion coatings and their properties using eucommia gum / carbon nanotube modified epoxy resin [J]. Synthetic Rubber Industry, 2022, 45(01): 54-59) prepared conductive anti-corrosion coatings using eucommia gum (EUG) and epoxy resin (E-51) as the coating matrix and carbon nanotubes as the conductive filler. While the introduction of eucommia gum and carbon nanotubes improved the brittleness and poor conductivity of the epoxy coating to some extent, carbon nanotubes, as one-dimensional nanomaterials, do not have an advantage in corrosion resistance. Carbon nanotubes are prone to agglomeration, which not only fails to provide the barrier function expected of a coating filler but also affects the original properties of the coating due to their dispersibility. Summary of the Invention

[0009] To overcome the aforementioned problems, this invention provides a method for preparing a conductive self-healing coating on the surface of an aluminum shielding tape. This method not only solves the problems of high energy consumption and significant pollution associated with traditional coating methods for preparing protective films on shielding tapes, but also addresses the issues of reduced conductivity and poor corrosion resistance caused by the existing oxide film on the surface of aluminum shielding tapes. Furthermore, through an in-situ reduction / etching synergistic process, the original dense Al2O3 film on the aluminum surface is rationally transformed and utilized, forming a new type of aluminum on its surface, reducing the surface resistivity of the shielding tape. Additionally, etching creates pores to increase the surface roughness of the shielding tape, which is beneficial for subsequent film coating and further improves the adhesion between the film and the substrate. Based on the in-situ treatment of the aluminum shielding tape substrate surface, this invention introduces conductive structural units and dynamic chemical bonds into the coating system, synergistically enhancing the conductive grounding function of the aluminum shielding tape and endowing the coating with self-healing properties. This allows the coating to repair scratches caused by the overlapping and friction of shielding tapes during actual cable wrapping production.

[0010] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0011] A method for preparing a conductive self-healing coating on the surface of an aluminum shielding strip is implemented according to the following steps:

[0012] Step 1, In-situ reduction / etching pretreatment of aluminum material:

[0013] A mixed solution of aluminum fluoride and sodium fluoride was added to a container, and the pH of the mixed solution was adjusted. An aluminum shielding tape was used as the cathode, and a graphite sheet was used as the anode. The aluminum shielding tape was immersed in the mixed solution with a suitable distance between them. The temperature of the mixed solution and the current density of the external power supply were controlled. Under the above conditions, a reduction etching was performed for a certain period of time to obtain a clean aluminum shielding tape that had undergone in-situ reduction / etching pretreatment.

[0014] Step 2, Preparation of a dual-effect enhancer for conductivity and repair:

[0015] A suspension composed of carboxylated carbon nanotubes and dimethylacetamide was added to a three-necked flask, N2 gas was introduced and the mixture was stirred continuously. Then, excess isocyanate, dibutyltin dilaurate and an appropriate amount of dimethylacetamide were added dropwise to obtain a mixed solution. After the addition was completed, the mixed solution was stirred and reacted at 60℃~80℃ for 6~10h. After filtration and washing, a dual-effect enhancer for conductivity and repair was obtained.

[0016] Step 3, Prepare conductive / self-healing coating:

[0017] Weigh the conductive / repairing dual-effect reinforcing agent, diisocyanate, polyetheramine, and dimethylacetamide, and prepolymerize them under N2 atmosphere for a certain time; then add a compound solvent composed of aniline, adipic dihydrazide, diamine compound, terephthalaldehyde, and dimethylacetamide dropwise, and continue the polymerization reaction under N2 atmosphere for a certain time; finally, add defoamer and leveling agent to obtain conductive / self-repairing coating.

[0018] Step 4: Prepare a conductive / self-healing coating on the surface of the aluminum shielding strip:

[0019] First, add an appropriate amount of dimethylacetamide solvent to the conductive / self-healing coating obtained in step 3 to adjust the solid content of the coating system; then, spray the coating onto the surface of the aluminum shielding strip obtained in step 1 by atomization, and finally dry to complete the preparation of the conductive self-healing coating on the surface of the aluminum shielding strip.

[0020] Further, in step 1, the mass fraction of aluminum fluoride and sodium fluoride is 5-12%, the mass ratio of aluminum fluoride to sodium fluoride is 2:0.5-1.5, the pH range is 4.5-6, the temperature of the mixed solution is controlled at 30-60℃, and the applied power supply current density is 5-25 mA / cm². 2 The reduction etching reaction time is 5 to 20 minutes.

[0021] Furthermore, in step 2, the amount of carboxylated carbon nanotubes added is 0.5–1 g, the amount of dimethylacetamide is 100 mL, the isocyanate is hexamethylene diisocyanate, the amount of isocyanate added is 6–12 g, and the amount of dibutyltin dilaurate added is 0.1–0.2 g.

[0022] Further, in step 3, the mass of the conductive / repair dual-effect reinforcing agent is 1-5 parts, the mass of diisocyanate is 16-28 parts, the mass of polyetheramine is 30-60 parts, the mass of dimethylacetamide is 107-153 parts, and the total mass of the prepolymer solvent is 200 parts; in the compound solvent, the mass of aniline is 7-9 parts, the mass of adipic acid dihydrazide is 4-8 parts, the mass of the diamine compound is 5-10 parts, the mass of terephthalaldehyde is 1-3 parts, and the mass of dimethylacetamide is 30 parts; diisocyanate... The ester is one or more of isophorone diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, and trimethylhexane diisocyanate; the diamine compound is one or more of isophorone diamine, diethyltoluene diamine, 2,2'-(ethylenedioxy)bis(ethylamine), 1,6-hexanediamine, and 4,4'-dithiodiphenylamine; 0.5 to 1 part of defoamer and 0.5 to 1 part of leveling agent are added.

[0023] Furthermore, in step 3, the prepolymerization reaction time is 1–6 h, the prepolymerization reaction temperature is 25–60 °C, the polymerization time is 0.5–2.5 h, and the polymerization reaction temperature is 60–80 °C.

[0024] Furthermore, the feature is that, in step 4, the solid content of the coating system is adjusted to a range of 15% to 28%.

[0025] Compared with the prior art, the beneficial effects of the present invention are:

[0026] This invention provides a method for preparing a conductive self-healing coating on the surface of an aluminum shielding strip, enabling the formation of such a coating. Firstly, existing techniques such as mechanical grinding, chemical cleaning, and traditional electrochemical cleaning all have certain problems, leading to uneven aluminum strip thickness, reduced mechanical properties, and the formation of an Al2O3 film covering the reduced aluminum, all of which affect subsequent wrapping processing and conductivity of the aluminum shielding strip. This invention combines an electrochemical in-situ reduction method with ion etching technology to etch and create pores in the naturally formed dense Al2O3 film on the surface of the aluminum shielding strip, while simultaneously removing Al from the reaction system... 3+New Al is formed by reduction and enrichment on the surface of aluminum strips, and the surface roughness is improved by ion etching, forming a large number of regularly distributed concave pore structures, laying the foundation for further improving the adhesion between the coating and the aluminum substrate. Secondly, multiple dynamic hydrogen bonds and imine bonds are introduced into the conductive coating system. Through the synergistic effect of dynamic hydrogen bonds and imine bonds with different activity levels, the adaptability and repair efficiency of the coating are improved. Furthermore, considering the operating conditions of the cable (full load 90℃ and half load 60℃), this invention uses isocyanate-modified carboxylated carbon nanotubes to obtain a dual-effect conductive / repairing enhancer (NCO-CNTs). The enhancer is embedded into the conductive coating backbone in a bonded form through the isocyanate group (-NCO) to increase the bonding performance. Based on the electrical conductivity and heat transfer effect of CNTs, it exhibits both conductivity and self-repair promoting enhancement under both cable operating conditions (90℃ or 60℃). Attached Figure Description

[0027] Figure 1 This is a flowchart and morphological diagram of a method for preparing a conductive self-healing coating on the surface of an aluminum shielding strip according to the present invention. Detailed Implementation

[0028] The present invention will now be described in detail with reference to specific embodiments and accompanying drawings.

[0029] like Figure 1 As shown, a method for preparing a conductive self-healing coating on the surface of an aluminum shielding strip is implemented according to the following steps:

[0030] Step 1, In-situ reduction / etching pretreatment of aluminum material:

[0031] Add a mixed solution of aluminum fluoride and sodium fluoride to a container. The mass fraction of aluminum fluoride to sodium fluoride is 5-12%, and the mass ratio of aluminum fluoride to sodium fluoride is 2:0.5-1.5. Adjust the pH of the mixed solution to 4.5-6 using dilute hydrochloric acid. Use an aluminum shielding strip as the cathode and a graphite sheet as the anode, immersing them in the mixed solution at a suitable distance. Control the temperature of the mixed solution to 30-60℃ and the current density of the external power supply to 5-25 mA / cm². 2 Under the above conditions, a clean aluminum shielding tape with in-situ reduction / etching pretreatment is obtained by reduction etching for 5-20 minutes.

[0032] Step 2, Preparation of a dual-effect enhancer for conductivity and repair:

[0033] A suspension consisting of 0.5–1 g of carboxylated carbon nanotubes and 100 mL of dimethylacetamide was added to a three-necked flask, and N2 gas was introduced while stirring continuously. Then, 6–12 g of hexamethylene diisocyanate, 0.1–0.2 g of dibutyltin dilaurate, and an appropriate amount of dimethylacetamide (DMAc) were added dropwise to obtain a mixed solution. After the addition was completed, the mixed solution was stirred and reacted at 60–80 °C for 6–10 h. After filtration and washing, the repair / conductivity enhancer was obtained.

[0034] Step 3, Prepare conductive / self-healing coating:

[0035] The prepolymer solvent consists of 1-5 parts by weight of conductive / repairing dual-effect reinforcing agent, 16-28 parts by weight of diisocyanate, 30-60 parts by weight of polyetheramine, and 107-153 parts by weight of dimethylacetamide (DMAc), with a total mass of 200 parts. The prepolymerization reaction is carried out under a nitrogen atmosphere for a certain time, with a reaction time of 1-6 hours and a reaction temperature of 25-60°C. Then, a compound solvent consisting of 7-9 parts by weight of aniline, 4-8 parts by weight of adipic dihydrazide, 5-10 parts by weight of diamine compound, 1-3 parts by weight of terephthalaldehyde, and 30 parts by weight of dimethylacetamide is added dropwise. The polymerization reaction continues under a nitrogen atmosphere for 0.5-2.5 hours at a temperature of 60-80°C. Finally, 0.5-1 parts by weight of defoamer and 0.5-1 parts by weight of leveling agent are added to obtain a conductive / self-healing coating.

[0036] The diisocyanate is selected from one or more mixtures of isophorone diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate, hexamethylene diisocyanate and trimethylhexane diisocyanate;

[0037] The diamine compound is one or more of isophorone diamine, diethyltoluene diamine, 2,2'-(ethylenedioxy)bis(ethylamine), 1,6-hexanediol and 4,4'-dithiodiphenylamine;

[0038] Step 4: Prepare a conductive / self-healing coating on the surface of the aluminum shielding strip:

[0039] First, add an appropriate amount of dimethylacetamide solvent to the conductive / self-healing coating obtained in step 3, and adjust the solid content of the coating system to a range of 15-28%; then, spray the coating onto the surface of the aluminum shielding strip obtained in step 1 by atomization, and finally dry to complete the preparation of the conductive self-healing coating on the surface of the aluminum shielding strip.

[0040] Example 1

[0041] First, a 5% (w / w) mixed solution of aluminum fluoride and sodium fluoride was added to the container, with the ratio of aluminum fluoride to sodium fluoride being 2:1. The pH was adjusted to 5.0 using dilute hydrochloric acid. An aluminum shielding strip was used as the cathode, and a graphite sheet was immersed in the solution at a suitable distance from the anode. The applied current density was adjusted to 15 mA / cm². 2 The temperature of the mixed solution was maintained at 30°C, and the reduction etching was performed for 18 minutes under the above conditions to obtain a clean aluminum shielding strip that had undergone in-situ / etching pretreatment.

[0042] Next, a suspension composed of 0.5g of carboxylated carbon nanotubes and 100mL of dimethylacetamide (DMAc) was added to a three-necked flask, N2 gas was introduced and the mixture was stirred continuously. A solution of 6.67g of hexamethylene diisocyanate, 0.1g of dibutyltin dilaurate and 10g of DMAc was added dropwise. After the addition was completed, the mixture was stirred at 60℃ for 10h. Finally, the repair / conductivity enhancer was obtained after filtration and washing.

[0043] Then, 4 parts of conductive / repairing dual-effect reinforcing agent, 22 parts of toluene diisocyanate, 45 parts of polyetheramine D2000 and 129 parts of DMAc solvent were weighed and prepolymerized at 25°C for 4 hours under N2 atmosphere. Then, a compound solvent consisting of 7.13 parts of aniline, 4.36 parts of adipic acid dihydrazide, 8.64 parts of isophorone diamine, 1.7 parts of terephthalaldehyde and 30 parts of DMAc was added dropwise. The polymerization reaction was continued at 80°C for 0.5 hours under N2 atmosphere. Finally, 0.5 parts of defoamer and 0.5 parts of leveling agent were added to obtain conductive / self-healing coating.

[0044] Finally, 50 parts of solvent DMAc were added to the conductive / self-healing coating obtained in step 3 to adjust the solid content of the coating system to 25%. The coating was then atomized and sprayed onto the surface of the aluminum shielding strip obtained in step 1. Finally, the coating was dried to complete the preparation of the conductive self-healing coating on the surface of the aluminum shielding strip.

[0045] Example 2

[0046] First, add an 8% (w / w) mixed solution of aluminum fluoride and sodium fluoride to the container, with an aluminum fluoride to sodium fluoride ratio of 2:1.5. Adjust the pH to 5.5 using dilute hydrochloric acid. Place the aluminum shielding strip as the cathode and the graphite sheet as the anode, immersing them in the solution at a suitable distance. Adjust the applied power supply current density to 18 mA / cm². 2 The solution temperature was maintained at 40℃, and the reduction etching was performed for 12 minutes under the above conditions to obtain a clean aluminum shielding tape pretreated in situ / etching.

[0047] Next, a suspension composed of 0.5g of carboxylated carbon nanotubes and 100mL of dimethylacetamide (DMAc) was added to a three-necked flask, N2 gas was introduced and the mixture was stirred continuously. A solution of 8.41g of hexamethylene diisocyanate, 0.15g of dibutyltin dilaurate and 10g of DMAc was added dropwise. After the addition was completed, the mixture was stirred at 70℃ for 8.5h. Finally, the repair / conductivity enhancer was obtained after filtration and washing.

[0048] Then, 5 parts of conductive / repairing dual-effect reinforcing agent, 19.6 parts of isophorone diisocyanate, 34.8 parts of polyetheramine D2000 and 140.6 parts of DMAc solvent were weighed and prepolymerized at 40°C for 3 hours under N2 atmosphere. Then, a compound solvent consisting of 8.6 parts of aniline, 6.9 parts of adipate dihydrazide, 10 parts of diethyltoluene diamine, 1 part of terephthalaldehyde and 30 parts of DMAc was added dropwise. The polymerization reaction was continued at 65°C for 0.5 hours under N2 atmosphere. Finally, 0.5 parts of defoamer, 0.5 parts of leveling agent and other additives were added to obtain conductive / self-repairing coating.

[0049] Finally, 4.95 parts of solvent DMAc were added to the conductive / self-healing coating obtained in step 3 to adjust the solid content of the coating system to 27%. The coating was then atomized and sprayed onto the surface of the aluminum shielding strip obtained in step 1. Finally, the conductive self-healing coating on the surface of the aluminum shielding strip was prepared by drying.

[0050] Example 3

[0051] First, a 6% (w / w) mixed solution of aluminum fluoride and sodium fluoride was added to the container, with the ratio of aluminum fluoride to sodium fluoride being 2:0.5. The pH was adjusted to 6 using dilute hydrochloric acid. An aluminum shielding strip was used as the cathode, and a graphite sheet was immersed in the solution at a suitable distance from the anode. The applied current density was adjusted to 20 mA / cm². 2 The solution temperature was maintained at 60℃, and reduction etching was performed for 5 minutes under the above conditions to obtain a clean aluminum shielding tape pretreated in situ / etching.

[0052] Next, a suspension composed of 0.8g of carboxylated carbon nanotubes and 100mL of dimethylacetamide (DMAc) was added to a three-necked flask, N2 gas was introduced and the mixture was stirred continuously. A solution of 10.09g of hexamethylene diisocyanate, 0.2g of dibutyltin dilaurate and 10g of DMAc was added dropwise. After the addition was completed, the mixture was stirred at 80℃ for 6 hours. Finally, the repair / conductivity enhancer was obtained after filtration and washing.

[0053] Then, 5 parts of conductive / repairing dual-effect reinforcing agent, 28 parts of dicyclohexylmethane diisocyanate, 60 parts of polyetheramine D2000 and 107 parts of DMAc solvent were weighed and prepolymerized at 60°C for 3 hours under N2 atmosphere. Then, a compound solvent consisting of 9.0 parts of aniline, 7.6 parts of adipic acid dihydrazide, 10 parts of 4,4'-dithiodiphenylamine, 2.6 parts of terephthalaldehyde and 30 parts of DMAc was added dropwise. The polymerization reaction was continued at 80°C for 0.5 hours under N2 atmosphere. Finally, 1 part of defoamer and 1 part of leveling agent were added to obtain conductive / self-healing coating.

[0054] Finally, 165 parts of solvent DMAc were added to the conductive / self-healing coating obtained in step 3 to adjust the solid content of the coating system to 22%. The coating was then atomized and sprayed onto the surface of the aluminum shielding strip obtained in step 1. Finally, the coating was dried to complete the preparation of the conductive self-healing coating on the surface of the aluminum shielding strip.

[0055] Example 4

[0056] First, a 12% (w / w) mixed solution of aluminum fluoride and sodium fluoride was added to the container, with the ratio of aluminum fluoride to sodium fluoride being 2:1.2. The pH was adjusted to 6.0 using dilute hydrochloric acid. An aluminum shielding strip was used as the cathode, and a graphite sheet was used as the anode, immersed in the solution at a suitable distance. The applied power supply current density was adjusted to 25 mA / cm². 2 The solution temperature was maintained at 40℃, and the reduction etching was performed for 20 minutes under the above conditions to obtain a clean aluminum shielding tape pretreated in situ / etching.

[0057] Next, a suspension composed of 0.8g of carboxylated carbon nanotubes and 100mL of dimethylacetamide (DMAc) was added to a three-necked flask, N2 gas was introduced and the mixture was stirred continuously. A solution of 12g of hexamethylene diisocyanate, 0.2g of dibutyltin dilaurate and 10g of DMAc was added dropwise. After the addition was completed, the mixture was stirred at 60℃ for 10h. Finally, the repair / conductivity enhancer was obtained after filtration and washing.

[0058] Then, weigh 4 parts of conductive / repairing dual-effect reinforcing agent, 28 parts of diphenylmethane diisocyanate and hexamethylene diisocyanate mixed solution (1:1), 60 parts of polyetheramine and 108 parts of DMAc solvent, and prepolymerize at 25°C for 6 hours under N2 atmosphere. Then, add dropwise a compound solvent composed of 9 parts of aniline, 4 parts of adipate dihydrazide, 9.62 parts of 1,6-hexanediol, 2.6 parts of terephthalaldehyde and 30 parts of DMAc. Continue the polymerization reaction at 60°C for 1 hour under N2 atmosphere. Finally, add 0.5 parts of defoamer and 0.5 parts of leveling agent to obtain conductive / self-repairing coating.

[0059] Finally, 340 parts of solvent DMAc were added to the conductive / self-healing coating obtained in step 3 to adjust the solid content of the coating system to 15%. The coating was then atomized and sprayed onto the surface of the aluminum shielding strip obtained in step 1. Finally, the coating was dried to complete the preparation of the conductive self-healing coating on the surface of the aluminum shielding strip.

[0060] Example 5

[0061] First, add an 8% (w / w) mixed solution of aluminum fluoride and sodium fluoride to the container, with an aluminum fluoride to sodium fluoride ratio of 2:0.75. Adjust the pH to 4.5 using dilute hydrochloric acid. Use an aluminum shielding strip as the cathode and a graphite sheet as the anode, immersing them in the solution at a suitable distance. Adjust the applied power supply current density to 5 mA / cm². 2 The solution temperature was maintained at 30℃, and the reduction etching was performed for 20 minutes under the above conditions to obtain a clean aluminum shielding tape pretreated in situ / etching.

[0062] Next, a suspension composed of 1g of carboxylated carbon nanotubes and 100mL of dimethylacetamide (DMAc) was added to a three-necked flask, N2 gas was introduced and the mixture was stirred continuously. A solution of 6g hexamethylene diisocyanate, 0.2g dibutyltin dilaurate and 10g DMAc was added dropwise. After the addition was completed, the mixture was stirred at 80℃ for 6h. Finally, the repair / conductivity enhancer was obtained after filtration and washing.

[0063] Then, weigh 1 part of conductive / repairing dual-effect reinforcing agent, 16 parts of trimethyl hexamethylene diisocyanate, 30 parts of polyetheramine and 153 parts of DMAc solvent, and prepolymerize at 50°C for 1 hour under N2 atmosphere. Then, add dropwise a compound solvent composed of 7 parts of aniline, 8 parts of adipate dihydrazide, 5 parts of isophorone diamine and 2,2'-(ethylenedioxy)bis(ethylamine) mixture (1:1), 3 parts of terephthalaldehyde and 30 parts of DMAc. Continue the polymerization reaction at 60°C for 2.5 hours under N2 atmosphere. Finally, add 1 part of defoamer, 1 part of leveling agent and other additives to obtain conductive / self-repairing coating.

[0064] Finally, 88 parts of solvent DMAc were added to the conductive / self-healing coating obtained in step 3 to adjust the solid content of the coating system to 18%. The coating was then atomized and sprayed onto the surface of the aluminum shielding strip obtained in step 1. Finally, the coating was dried to complete the preparation of the conductive self-healing coating on the surface of the aluminum shielding strip.

[0065] Table 1 shows the water contact angle, surface contact resistance, and self-healing time (scratch disappearance cutoff time) of the coatings prepared in Example 1, Example 2, Example 3, the coating not prepared in step 1 in Example 3, the aluminum shielding tape treated in step 1 (using the relevant parameters of step 1 in Example 3), and the untreated aluminum shielding tape.

[0066] Table 1

[0067]

[0068] As shown in Table 1, the untreated aluminum shielding tape exhibited the highest surface contact resistance, with the naturally formed dense oxide film leading to a decrease in conductivity. However, the surface contact resistance of the aluminum shielding tape treated in step 1 decreased significantly, and its conductivity was significantly improved. However, due to the pore formation on its surface, the water contact angle also decreased. In Examples 1-3, the hydrophobicity (water contact angle) of the samples was significantly improved. This was because the conductive / repair enhancer, embedded in the long chains of conductive units in the coating polymer, formed a conductive pathway network, resulting in a substantial reduction in surface contact resistance. Furthermore, the in-situ reduction / etching pretreatment formed a new porous aluminum surface structure on the aluminum shielding tape, increasing the specific surface area of ​​the shielding tape and thus increasing the contact area between the coating and the substrate, which is also a significant reason for the reduced contact resistance. The coating sample in Example 3 had more reasonable process parameters and formulation ratios in the aluminum shielding tape pretreatment (step 1) and coating preparation (steps 2 and 3), exhibiting not only good electrical performance but also the fastest self-healing speed at full-load operating temperature (90°C) and half-load operating temperature (60°C). Therefore, the coating in Example 3 exhibited excellent conductive self-healing performance.

[0069] The above description of the present invention represents only some embodiments, but the present invention is not limited to the above embodiments. The above embodiments are illustrative and not restrictive. All specific extensions using the materials and methods of the present invention, without departing from the spirit and scope of the claims, are within the protection scope of the present invention.

Claims

1. A method for preparing a conductive self-healing coating on the surface of an aluminum shielding strip, characterized in that, The specific steps are as follows: Step 1, In-situ reduction / etching pretreatment of aluminum material: A mixed solution of aluminum fluoride and sodium fluoride was added to a container, and the pH of the mixed solution was adjusted. An aluminum shielding tape was used as the cathode, and a graphite sheet was used as the anode. The aluminum shielding tape was immersed in the mixed solution with a suitable distance between them. The temperature of the mixed solution and the current density of the external power supply were controlled. Under the above conditions, a reduction etching was performed for a certain period of time to obtain a clean aluminum shielding tape that had undergone in-situ reduction / etching pretreatment. Step 2, Preparation of a dual-effect enhancer for conductivity and repair: A suspension composed of carboxylated carbon nanotubes and dimethylacetamide was added to a three-necked flask, N2 gas was introduced and the mixture was stirred continuously. Then, excess isocyanate, dibutyltin dilaurate and an appropriate amount of dimethylacetamide were added dropwise to obtain a mixed solution. After the addition was completed, the mixed solution was stirred and reacted at 60℃~80℃ for 6~10h. After filtration and washing, a dual-effect enhancer for conductivity and repair was obtained. Step 3, Prepare conductive / self-healing coating: Weigh the conductive / repairing dual-effect reinforcing agent, diisocyanate, polyetheramine, and dimethylacetamide, and prepolymerize them under N2 atmosphere for a certain time; then add a compound solvent composed of aniline, adipic dihydrazide, diamine compound, terephthalaldehyde, and dimethylacetamide dropwise, and continue the polymerization reaction under N2 atmosphere for a certain time; finally, add defoamer and leveling agent to obtain conductive / self-repairing coating. Step 4: Prepare a conductive / self-healing coating on the surface of the aluminum shielding strip: First, add an appropriate amount of dimethylacetamide solvent to the conductive / self-healing coating obtained in step 3 to adjust the solid content of the coating system; then, spray the coating onto the surface of the aluminum shielding strip obtained in step 1 by atomization, and finally dry to complete the preparation of the conductive self-healing coating on the surface of the aluminum shielding strip.

2. The method for preparing a conductive self-healing coating on the surface of an aluminum shielding strip according to claim 1, characterized in that, In step 1, the mass fraction of aluminum fluoride and sodium fluoride is 5-12%, the mass ratio of aluminum fluoride to sodium fluoride is 2:0.5-1.5, the pH range is 4.5-6, the temperature of the mixed solution is controlled at 30-60℃, and the applied power supply current density is 5-25 mA / cm². 2 The reduction etching reaction time is 5 to 20 minutes.

3. The method for preparing a conductive self-healing coating on the surface of an aluminum shielding strip according to claim 1, characterized in that, In step 2, the amount of carboxylated carbon nanotubes added is 0.5-1g, the amount of dimethylacetamide is 100mL, the isocyanate is hexamethylene diisocyanate, the amount of isocyanate added is 6-12g, and the amount of dibutyltin dilaurate added is 0.1-0.2g.

4. The method for preparing a conductive self-healing coating on the surface of an aluminum shielding strip according to claim 1, characterized in that, In step 3, the mass of the conductive / repair dual-effect reinforcing agent is 1-5 parts, the mass of diisocyanate is 16-28 parts, the mass of polyetheramine is 30-60 parts, the mass of dimethylacetamide is 107-153 parts, and the total mass of the prepolymer solvent is 200 parts; in the compound solvent, the mass of aniline is 7-9 parts, the mass of adipic dihydrazide is 4-8 parts, the mass of the diamine compound is 5-10 parts, the mass of terephthalaldehyde is 1-3 parts, and the mass of dimethylacetamide is 30 parts; the mass of diisocyanate is... One or more of isophorone diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, and trimethylhexane diisocyanate; the diamine compound is one or more of isophorone diamine, diethyltoluene diamine, 2,2'-(ethylenedioxy)bis(ethylamine), 1,6-hexanediamine, and 4,4'-dithiodiphenylamine; 0.5 to 1 part of defoamer and 0.5 to 1 part of leveling agent are added.

5. The method for preparing a conductive self-healing coating on the surface of an aluminum shielding strip according to claim 1, characterized in that, In step 3, the prepolymerization reaction time is 1–6 h and the prepolymerization reaction temperature is 25–60 °C; the polymerization time is 0.5–2.5 h and the polymerization reaction temperature is 60–80 °C.

6. The method for preparing a conductive self-healing coating on the surface of an aluminum shielding strip according to claim 1, characterized in that, In step 4, the solid content of the coating system is adjusted to a range of 15% to 28%.

Images