CN112680030B - Conductive microcapsule, graphene conductive ink, preparation method and application of conductive microcapsule, graphene conductive film and self-repairing method of graphene conductive film - Google Patents
Conductive microcapsule, graphene conductive ink, preparation method and application of conductive microcapsule, graphene conductive film and self-repairing method of graphene conductive film Download PDFInfo
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Abstract
The invention belongs to the technical field of novel graphene materials and printing ink, and discloses a conductive microcapsule, graphene conductive printing ink, a preparation method and application of the conductive microcapsule, a graphene conductive film and a self-repairing method of the graphene conductive film. The graphene conductive ink is prepared from the following raw material components in parts by mass: 30-60% of water-based resin, 2-20% of graphene, 1-5% of conductive microcapsule, 2-8% of dispersing agent, 0.1-0.5% of defoaming agent, 0.5-2% of thickening agent and 30-55% of water, wherein the conductive microcapsule takes a composite material of graphene and low-melting-point polyurethane as a core material, takes amino resin as a wall material and has conductive metal particles deposited on the surface, and the melting point of the low-melting-point polyurethane is 50-60 ℃. The conductive microcapsule and the graphene conductive ink have good conductive and self-repairing functions, can repair microcracks of a graphene conductive film, solve the problem of reduction of electrical properties of the graphene conductive film, prolong the service life of the material, and have great industrial application prospects.
Description
Technical Field
The invention belongs to the technical field of novel graphene materials and printing ink, and particularly discloses a conductive microcapsule, graphene conductive printing ink, a preparation method and application of the conductive microcapsule, a graphene conductive film and a self-repairing method of the graphene conductive film.
Background
The conductive ink as a key printing material plays a crucial role in the manufacture of printed electronic products, and the development level of the conductive ink is an important embodiment of the high technology of the printed electronic materials in China. In recent years, with the rapid development of new graphene materials and the high-speed industrialization of printing technologies, the development of graphene conductive ink by utilizing the characteristics of excellent conductivity, stable physical properties, no toxicity and environmental protection of graphene has become a research hotspot in the technical field of printing materials at home and abroad. The graphene conductive ink has the advantages of excellent conductivity, low cost, good printing adaptability, mild curing conditions and the like, can be printed on substrates such as metal foils, plastic films, fabrics, paper and the like, is suitable for screen printing, gravure printing, flexography, offset printing, ink jet printing and the like, and can be applied to the fields of Printed Circuit Boards (PCBs), Radio Frequency Identification (RFID), Display Screens (OLEDs), electrode sensors and the like, so that the graphene conductive ink is expected to be widely applied to next-generation light and thin flexible electronic products such as radio frequency tags, intelligent packaging, film switches, conductive circuits, sensors and the like, and has huge industrial prospects.
Chinese patents CN 202010604538.9, CN 202010658998.X and CN 202010780291.6 all disclose technical schemes of obtaining graphene by peeling expandable graphite, and blending the graphene with a polymer resin binder, an additive and a solvent to prepare graphene conductive ink, and the obtained graphene conductive ink has excellent conductivity and good printing adaptability; chinese patents CN 202010080924.2 and CN 201910444840.X respectively disclose technical solutions for applying polyaniline and sodium sulfanilate modified graphene to preparation of graphene conductive ink, so as to improve the conductivity and environmental friendliness of the graphene conductive ink. At present, although the conductivity, environmental protection and printing adaptability of the graphene conductive ink are remarkably improved in the prior art, the conductive film formed by the existing graphene conductive ink has a short service life, and electrical properties are easily reduced or even become invalid.
Disclosure of Invention
The invention aims to overcome the defects that a conductive film formed by the existing graphene conductive ink is short in service life and easy to cause electrical property reduction, and provides a conductive microcapsule, graphene conductive ink, a preparation method and application thereof, a graphene conductive film and a self-repairing method thereof, wherein the conductive microcapsule and the graphene conductive ink can prolong the service life and are not easy to cause electrical property reduction.
After intensive research, the inventor of the present invention finds that the basic reason for causing the short service life and the easy occurrence of the electrical property decrease of the conductive film obtained by the existing graphene conductive ink is that the binder of the graphene conductive ink is a high molecular material, and in practical application, due to self aging and external force, some local damages and microcracks are inevitably generated, the continuity of the conductive network in the material is damaged, the electrical property decreases and even fails, and thus the service life of the material is shortened. After intensive research, the inventor of the present invention has found that a conductive microcapsule, which takes a composite material of graphene and low-melting-point polyurethane as a core material and amino resin as a wall material and has conductive metal particles deposited on the surface, has a good self-repairing function on graphene conductive ink, and can significantly improve the service life of a conductive film obtained from the graphene conductive ink, so that the conductive film does not substantially suffer from electrical property degradation over a long period of time. The reason for this is presumed to be due to: the conductive microcapsule takes a composite material of graphene and low-melting-point polyurethane as a core material, the graphene can be used as a conductive repairing material due to excellent conductive performance of the graphene, the low-melting-point polyurethane has good fluidity when being heated, and can carry the graphene to spontaneously flow and fill the crack, meanwhile, the polyurethane and matrix resin have good adhesion, so that the recovery of the mechanical property of the crack of the material can be promoted to a certain extent, conductive metal particles deposited on the surface of the conductive microcapsule can endow the surface of the material with good conductive performance, the influence of a conventional insulating microcapsule material on the conductive performance of the graphene conductive ink can be eliminated, and the conductive performance of the conductive ink can be improved; as shown in fig. 1, after the material has microcracks, the amino resin wall material is easily broken under the action of crack stress, and the conductive repairing material in the capsule flows out and fills the microcracks, so that the graphene conductive ink and the graphene conductive film prepared from the graphene conductive ink have good conductive self-repairing functions. Based on this, the present invention has been completed.
Specifically, the invention provides a conductive microcapsule, wherein the conductive microcapsule takes a composite material of graphene and low-melting-point polyurethane as a core material, takes amino resin as a wall material, and has conductive metal particles deposited on the surface, and the melting point of the low-melting-point polyurethane (TPU) is 50-60 ℃.
In the invention, the conductive microcapsule takes a composite material of graphene and low-melting-point polyurethane as a core material. Wherein the graphene may be selected from at least one of physical graphene, CVD graphene, and reduced graphene oxide. The low-melting-point polyurethane (TPU) has a melting point of 50-60 ℃, and specifically can be 50 ℃, 51 ℃, 52 ℃, 53 ℃, 54 ℃, 55 ℃, 56 ℃, 57 ℃, 58 ℃, 59 ℃, 60 ℃ and the like. The mass ratio of the graphene to the low-melting-point polyurethane is preferably (0.05 to 0.2):1, and may be, for example, 0.05:1, 0.06:1, 0.07:1, 0.08:1, 0.09:1, 0.1:1, 0.11:1, 0.12:1, 0.13:1, 0.14:1, 0.15:1, 0.16:1, 0.17:1, 0.18:1, 0.19:1, 0.2:1, or the like.
In the invention, the conductive microcapsule takes amino resin as a wall material. The amino resin is preferably a polymer formed by the polycondensation reaction of melamine and formaldehyde. The reason why the amino resin is selected as the wall material is that the amino resin is easy to break under the action of crack stress, and conditions can be created for the outflow of the graphene and the low-melting-point TPU in the capsule.
In the present invention, the kind of the conductive metal particles in the conductive microcapsule is not particularly limited, and may be silver particles, copper particles, gold particles, or the like, and preferably silver particles and/or copper particles.
In the invention, the mass ratio of the core material to the wall material in the conductive microcapsule is preferably (0.5-2) to 1, and the mass ratio of the total mass of the core material and the wall material to the conductive metal particles is preferably 1 (0.5-2). When the content ratio of the core layer, the wall material and the conductive metal particles is controlled within the above range, the conductive performance and the self-repairing function of the microcapsule can be well balanced. In addition, the particle size of the microcapsule material is preferably 2-20 μm. The particle diameter of the conductive metal particles is preferably 20 to 150 nm.
The invention also provides a preparation method of the conductive microcapsule, which comprises the following steps:
s1, uniformly melting and blending the graphene and the low-melting-point polyurethane according to the mass ratio (0.05-0.2) to 1, wherein the melting point of the low-melting-point polyurethane is 50-60 ℃, so as to obtain the composite material of the graphene and the low-melting-point polyurethane;
s2, adjusting the pH value of a mixed aqueous solution of melamine and formaldehyde to 8-9, and stirring at the temperature of 60-80 ℃ at the rotating speed of 400-600 r/min until the solution is transparent to obtain a prepolymer solution; the mass ratio of the melamine to the formaldehyde to the water in the system is 1 (1-3) to 15-25;
s3, stirring the composite material of the graphene and the low-melting-point polyurethane obtained in the step S1 and an emulsifier at the temperature of 60-80 ℃ for 0.1-1 h, then adding water, and stirring and emulsifying at the rotating speed of 10000-20000 r/min for 5-20 min to obtain a stable oil-in-water emulsion; the mass ratio of the composite material of graphene and low-melting-point polyurethane to the emulsifier to water is 1 (0.02-0.1) to 10-30;
s4, adjusting the pH value of the oil-in-water type emulsion obtained in the step S3 to 4-5, slowly dropwise adding the prepolymer solution obtained in the step S2 into the emulsion, simultaneously reducing the stirring speed to 100-200 r/min, after dropwise adding of the prepolymer solution is finished, preserving heat for 2-4 h at 60-80 ℃, cooling, repeatedly washing the obtained product with deionized water and petroleum ether for 2-5 times, and performing suction filtration and vacuum drying to obtain microcapsules;
s5, blending the microcapsule obtained in the step S4, metal salt, a reducing agent and water to form a suspension, carrying out liquid phase reduction reaction on the suspension by using a microwave reactor, wherein the microwave power is 500-1000W, the microwave time is 5-15 min, cooling after the reaction is finished, repeatedly washing the obtained product for 2-5 times by using deionized water and ethanol, and carrying out suction filtration and vacuum drying to obtain the conductive microcapsule; the mass ratio of the microcapsule, the metal salt, the reducing agent and the water is 1 (0.5-2) to (0.05-0.1) to (50-150); the metal salt is at least one selected from the group consisting of silver acetate, silver nitrate, copper sulfate and copper acetate.
In the preparation method of the conductive microcapsule provided by the present invention, in step S1, the melt blending of the graphene and the low-melting-point polyurethane may be performed in various existing melt blending apparatuses, for example, in an open mill or an internal mixer. The temperature of the melt blending can be 60-80 ℃, and the time can be 3-5 h.
In the method for preparing the conductive microcapsule provided by the present invention, in step S2, the method for obtaining the mixed aqueous solution of melamine and formaldehyde is not particularly limited, and for example, melamine, formaldehyde and water may be mixed in any order.
In the preparation method of the conductive microcapsule provided by the present invention, in step S3, the kind of the emulsifier is not particularly limited, and for example, the emulsifier may be various existing ionic surfactants, nonionic surfactants or amphoteric surfactants, and specific examples thereof include but are not limited to: stearic acid, sodium stearate, sodium dodecyl benzene sulfonate, sodium octadecyl sulfate, lecithin, fatty glyceride, span, tween, PE-6200 and the like.
In the preparation method of the conductive microcapsule provided by the present invention, in step S5, the reducing agent may be any of various existing substances capable of reducing a metal salt to a metal, such as vitamin C.
The invention also provides application of the conductive microcapsule as a self-repairing material.
In addition, the invention also provides graphene conductive ink which has a conductive and self-repairing function, wherein the graphene conductive ink is prepared from the following raw material components in parts by mass:
the conductive microcapsule is the conductive microcapsule.
In the graphene conductive ink provided by the present invention, specific examples of the aqueous resin include, but are not limited to: at least one of aqueous polyurethane resin (PU), aqueous acrylic resin (PA) and aqueous acrylic modified polyurethane resin (PUA).
In the graphene conductive ink provided by the present invention, the graphene component in the graphene conductive ink may be specifically selected from at least one of physical graphene, CVD graphene, and reduced graphene oxide, and is preferably the same as the graphene contained in the conductive microcapsule.
The invention also provides a preparation method of the graphene conductive ink, which comprises the following steps:
s1, sequentially adding a dispersing agent, graphene and a defoaming agent into water, mixing, and carrying out wet grinding for 0.5-3 h by using a nano sand mill to obtain uniform graphene slurry;
and S2, sequentially adding the graphene slurry obtained in the step S1 and the conductive microcapsules into water-based resin, stirring and blending uniformly at a low speed, adding a thickening agent to adjust the viscosity of the system to 10,000-50,000 cP, filtering and discharging to obtain the graphene conductive ink.
The invention also provides a self-repairing graphene conductive film, wherein the self-repairing graphene conductive film is prepared by coating and curing the graphene conductive ink.
In addition, the invention also provides a self-repairing method of the graphene conductive film, wherein the graphene conductive film is prepared by coating and curing the graphene conductive ink, and the self-repairing method comprises the steps of heating the graphene conductive film to 50-80 ℃ and keeping the temperature for 1-3 hours when the electrical performance of the graphene conductive film is reduced.
The conductive microcapsule and the graphene conductive ink provided by the invention have good conductive and self-repairing functions, can repair microcracks generated by the graphene conductive film due to self aging or external force, enable the graphene conductive film not to be prone to electrical property reduction, prolong the service life of the material, and have great industrial application prospects.
Drawings
Fig. 1 is a schematic diagram of a self-repairing process of the graphene conductive ink provided by the invention.
Detailed Description
The present invention will be described in detail below by way of examples. The examples of embodiments are intended to be illustrative of the invention and are not to be construed as limiting the invention. The examples do not specify particular techniques or conditions, and are performed according to the techniques or conditions described in the literature in the art or according to the product specifications. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products commercially available.
In the following examples and comparative examples, the parts of each raw material are parts by mass.
Example 1
(1) Preparation of conductive microcapsules
S1, mixing 0.1 part of graphene with 1.5 parts of low-melting-point polyurethane granules (the melting point is 50-60 ℃, the same applies below), feeding the mixture into an internal mixer, and carrying out melt blending for 5 hours at the temperature of 80 ℃ to obtain the composite material of the graphene and the low-melting-point polyurethane;
s2, adding 1 part of melamine, 2 parts of formaldehyde and 20 parts of water into a reaction container, adjusting the pH value of the solution to 8-9 by using triethanolamine, and stirring at a constant temperature of 70 ℃ at a rotating speed of 600r/min until the solution is transparent to obtain a prepolymer solution;
s3, adding the composite material of graphene and low-melting-point polyurethane in the step S1 and 0.1 part of PE-6200 into a reaction container, stirring at a constant temperature of 70 ℃ for 0.5h, then adding 40 parts of water, and stirring and emulsifying for 10min at a rotating speed of 15,000r/min by using an emulsifier to obtain a stable oil-in-water emulsion;
s4, adjusting the pH value of the oil-in-water emulsion in the step S3 to 4-5 with acetic acid, slowly dripping the prepolymer solution in the step S2 into the emulsion, simultaneously reducing the stirring speed to 150r/min, preserving the temperature for 3 hours at 70 ℃ after the dripping of the prepolymer solution is finished, repeatedly washing the obtained product for 3 times with deionized water and petroleum ether after cooling, and performing suction filtration and vacuum drying to obtain microcapsules;
s5, blending 1 part of the microcapsule obtained in the step S4, 1 part of silver acetate, 0.08 part of vitamin C and 100 parts of water to form a suspension, carrying out liquid phase reduction on the suspension by using a microwave reactor, wherein the microwave power is 800W, the microwave time is 10min, cooling after the reaction is finished, repeatedly washing the obtained product for 3 times by using deionized water and ethanol, and carrying out suction filtration and vacuum drying to obtain the conductive microcapsule. The conductive microcapsule takes a composite material of graphene and low-melting-point polyurethane as a core material and amino resin as a wall material, and silver particles are deposited on the surface of the conductive microcapsule, wherein the particle size of the conductive microcapsule is 2-10 mu m, and the particle size of the silver particles is 20-150 nm.
(2) Preparation of graphene conductive ink
Sequentially adding 2 parts of dispersing agent, 5 parts of graphene and 0.3 part of defoaming agent into 50.7 parts of water, mixing, and wet-grinding for 2 hours by using a nano sand mill to prepare uniform graphene slurry; and sequentially adding the obtained graphene slurry and 1 part of conductive microcapsule into 40 parts of waterborne polyurethane resin, stirring and blending at a low speed of 600r/min for 10min, then adding 1 part of thickening agent to adjust the viscosity of the system to 10,000-50,000 cP, filtering and discharging to obtain the graphene conductive ink.
Example 2
(1) Preparation of conductive microcapsules: same as in example 1.
(2) Preparing graphene conductive ink: sequentially adding 2 parts of dispersing agent, 5 parts of graphene and 0.3 part of defoaming agent into 48.7 parts of water, mixing, and wet-grinding for 2 hours by using a nano sand mill to prepare uniform graphene slurry; and sequentially adding the obtained graphene slurry and 3 parts of conductive microcapsules into 40 parts of waterborne polyurethane resin, stirring and blending at a low speed of 600r/min for 10min, then adding 1 part of thickening agent to adjust the viscosity of the system to 10,000-50,000 cP, filtering and discharging to obtain the graphene conductive ink.
Example 3
(1) Preparation of conductive microcapsules: same as in example 1.
(2) Preparing graphene conductive ink: sequentially adding 2 parts of dispersing agent, 5 parts of graphene and 0.3 part of defoaming agent into 46.7 parts of water, mixing, and wet-grinding for 2 hours by using a nano sand mill to prepare uniform graphene slurry; and sequentially adding the obtained graphene slurry and 5 parts of conductive microcapsules into 40 parts of waterborne polyurethane resin, stirring and blending at a low speed of 600r/min for 10min, then adding 1 part of thickening agent to adjust the viscosity of the system to 10,000-50,000 cP, filtering and discharging to obtain the graphene conductive ink.
Example 4
Conductive microcapsules and graphene conductive ink were prepared according to the method of example 3, except that the amount of graphene used in the composite of graphene and low-melting polyurethane in step (1) was 0.15 parts, and the preparation conditions were the same as in example 3. The obtained conductive microcapsule takes a composite material of graphene and low-melting-point polyurethane as a core material, takes amino resin as a wall material, and has silver particles deposited on the surface, wherein the particle size of the conductive microcapsule is 2-10 mu m, and the particle size of the silver particles is 20-100 nm.
Example 5
Conductive microcapsules and graphene conductive ink were prepared according to the method of example 3, except that the amount of graphene used in the composite of graphene and low-melting polyurethane in step (1) was 0.3 parts, and the preparation conditions were the same as in example 3. The obtained conductive microcapsule takes a composite material of graphene and low-melting-point polyurethane as a core material, takes amino resin as a wall material, and has silver particles deposited on the surface, wherein the particle size of the conductive microcapsule is 2-10 mu m, and the particle size of the silver particles is 20-100 nm.
Example 6
(1) Preparation of conductive microcapsules
S1, mixing 0.3 part of graphene with 2.7 parts of low-melting-point polyurethane granules, feeding the mixture into an internal mixer, and carrying out melt blending for 5 hours at 80 ℃ to obtain a graphene and low-melting-point polyurethane composite material;
s2, adding 1 part of melamine, 2 parts of formaldehyde and 20 parts of water into a reaction container, adjusting the pH value of the solution to 8-9 by using triethanolamine, and stirring at a constant temperature of 70 ℃ at a rotating speed of 600r/min until the solution is transparent to obtain a prepolymer solution;
s3, adding the composite material of graphene and low-melting-point polyurethane in the step S1 and 0.15 part of PE-6200 into a reaction container, stirring at a constant temperature of 70 ℃ for 0.5h, then adding 50 parts of water, and stirring and emulsifying for 10min at a rotating speed of 15,000r/min by using an emulsifier to obtain a stable oil-in-water emulsion;
s4, adjusting the pH value of the oil-in-water emulsion in the step S3 to 4-5 with acetic acid, slowly dripping the prepolymer solution in the step S2 into the emulsion, simultaneously reducing the stirring speed to 150r/min, preserving the temperature for 3 hours at 70 ℃ after the dripping of the prepolymer solution is finished, repeatedly washing the obtained product for 3 times with deionized water and petroleum ether after cooling, and performing suction filtration and vacuum drying to obtain microcapsules;
s5, blending 1 part of the microcapsule obtained in the step S4, 1 part of silver acetate, 0.08 part of vitamin C and 100 parts of water to form a suspension, carrying out liquid phase reduction on the suspension by using a microwave reactor, wherein the microwave power is 800W, the microwave time is 10min, cooling after the reaction is finished, repeatedly washing the obtained product for 3 times by using deionized water and ethanol, and carrying out suction filtration and vacuum drying to obtain the conductive microcapsule. The conductive microcapsule takes a composite material of graphene and low-melting-point polyurethane as a core material and amino resin as a wall material, and silver particles are deposited on the surface of the conductive microcapsule, wherein the particle size of the conductive microcapsule is 5-15 mu m, and the particle size of the silver particles is 20-100 nm.
(2) Preparing graphene conductive ink: same as in example 5.
Example 7
(1) Preparation of conductive microcapsules
S1, mixing 0.5 part of graphene with 5.5 parts of low-melting-point polyurethane granules, feeding the mixture into an internal mixer, and carrying out melt blending for 5 hours at 80 ℃ to obtain a graphene and low-melting-point polyurethane composite material;
s2, adding 1 part of melamine, 2 parts of formaldehyde and 20 parts of water into a reaction container, adjusting the pH value of the solution to 8-9 by using triethanolamine, and stirring at a constant temperature of 70 ℃ at a rotating speed of 600r/min until the solution is transparent to obtain a prepolymer solution;
s3, adding the composite material of graphene and low-melting-point polyurethane in the step S1 and 0.3 part of PE-6200 into a reaction container, stirring at a constant temperature of 70 ℃ for 0.5h, then adding 80 parts of water, and stirring and emulsifying for 10min at a rotating speed of 15,000r/min by using an emulsifier to obtain a stable oil-in-water emulsion;
s4, adjusting the pH value of the oil-in-water emulsion in the step S3 to 4-5 with acetic acid, slowly dripping the prepolymer solution in the step S2 into the emulsion, simultaneously reducing the stirring speed to 150r/min, preserving the temperature for 3 hours at 70 ℃ after the dripping of the prepolymer solution is finished, repeatedly washing the obtained product for 3 times with deionized water and petroleum ether after cooling, and performing suction filtration and vacuum drying to obtain microcapsules;
s5, blending 1 part of the microcapsule obtained in the step S4, 1 part of copper acetate, 0.08 part of vitamin C and 100 parts of water to form a suspension, carrying out liquid phase reduction on the suspension by using a microwave reactor, wherein the microwave power is 800W, the microwave time is 10min, repeatedly washing the obtained product for 3 times by using deionized water and ethanol after the reaction is finished and cooled, and carrying out suction filtration and vacuum drying to obtain the conductive microcapsule. The conductive microcapsule takes a composite material of graphene and low-melting-point polyurethane as a core material and amino resin as a wall material, and copper particles are deposited on the surface of the conductive microcapsule, wherein the particle size of the conductive microcapsule is 5-20 mu m, and the particle size of the copper particles is 20-100 nm.
(2) Preparing graphene conductive ink: same as in example 5.
Example 8
Conductive microcapsules and a graphene conductive ink were prepared according to the method of example 5, except that in the step (1), silver acetate was used in an amount of 0.5 part, and the preparation conditions were the same as in example 5. The obtained conductive microcapsule takes a composite material of graphene and low-melting-point polyurethane as a core material, takes amino resin as a wall material, and has silver particles deposited on the surface, wherein the particle size of the conductive microcapsule is 5-20 mu m, and the particle size of the silver particles is 20-80 nm.
Example 9
Conductive microcapsules and graphene conductive ink were prepared according to the method of example 5, except that, in the step (1), silver acetate was used in an amount of 2 parts, and the preparation conditions were the same as in example 5. The obtained conductive microcapsule takes a composite material of graphene and low-melting-point polyurethane as a core material, takes amino resin as a wall material, and has silver particles deposited on the surface, wherein the particle size of the conductive microcapsule is 5-20 mu m, and the particle size of the silver particles is 50-150 nm.
Comparative example 1
A graphene conductive ink was prepared according to the method of example 1, except that no conductive microcapsule was added, to obtain a reference graphene conductive ink.
Comparative example 2
Conductive microcapsules and a graphene conductive ink were prepared according to the method of example 1, except that the surface conductive modification treatment was not performed during the preparation of the conductive microcapsules (i.e., step S5 was not included), and the remaining conditions were the same as those of example 1, to obtain a reference graphene conductive ink.
Test example
Printing the graphene conductive ink provided in the embodiments 1 to 9 and the comparative examples 1 to 2 on a fabric in a screen printing manner, drying and curing to obtain a conductive film, performing a bending test of a bending tester for 1000 times, heating the conductive film to 60 ℃ for repairing for 2 hours, and testing the sheet resistance of the conductive film before bending, after bending for 1000 times and after repairing respectively by using a sheet resistance tester. The test results are shown in table 1:
TABLE 1
As can be seen from table 1, the sheet resistance of the conductive film formed by the graphene conductive ink prepared in examples 1 to 9 is significantly increased after bending, the electrical properties are reduced, and the sheet resistance is reduced after heating and repairing, which indicates that the electrical properties of the conductive film are repaired. The conductive film formed by the graphene conductive ink provided by the invention has a self-repairing function, can repair microcracks generated by self-aging or external force of materials, and prolongs the service life of the materials. Comparative example 2 does not perform conductive modification treatment on the surface of the conductive microcapsule, and the sheet resistance of the conductive film formed by the graphene conductive ink is large, which shows that the electrical properties of the ink and the conductive film can be remarkably improved by performing conductive modification treatment on the surface of the conductive microcapsule.
Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made in the above embodiments by those of ordinary skill in the art without departing from the principle and spirit of the present invention.
Claims (10)
1. The conductive microcapsule for the self-repairing graphene conductive film is characterized in that a composite material of graphene and low-melting-point polyurethane is used as a core material, amino resin is used as a wall material, conductive metal particles are deposited on the surface of the composite material, and the melting point of the low-melting-point polyurethane is 50-60 ℃;
the conductive microcapsule is prepared by the method comprising the following steps:
s1, uniformly melting and blending the graphene and the low-melting-point polyurethane according to the mass ratio (0.05-0.2) to 1, wherein the melting point of the low-melting-point polyurethane is 50-60 ℃, so as to obtain the composite material of the graphene and the low-melting-point polyurethane;
s2, adjusting the pH value of a mixed aqueous solution of melamine and formaldehyde to 8-9, and stirring at the temperature of 60-80 ℃ at the rotating speed of 400-600 r/min until the solution is transparent to obtain a prepolymer solution; the mass ratio of the melamine to the formaldehyde to the water in the system is 1 (1-3) to 15-25;
s3, stirring the composite material of the graphene and the low-melting-point polyurethane obtained in the step S1 and an emulsifier at the temperature of 60-80 ℃ for 0.1-1 h, then adding water, and stirring and emulsifying at the rotating speed of 10000-20000 r/min for 5-20 min to obtain a stable oil-in-water emulsion; the mass ratio of the composite material of graphene and low-melting-point polyurethane to the emulsifier to water is 1 (0.02-0.1) to 10-30;
s4, adjusting the pH value of the oil-in-water type emulsion obtained in the step S3 to 4-5, slowly dropwise adding the prepolymer solution obtained in the step S2 into the emulsion, simultaneously reducing the stirring speed to 100-200 r/min, after dropwise adding of the prepolymer solution is finished, preserving heat for 2-4 h at 60-80 ℃, cooling, repeatedly washing the obtained product with deionized water and petroleum ether for 2-5 times, and performing suction filtration and vacuum drying to obtain microcapsules;
s5, blending the microcapsule obtained in the step S4, metal salt, a reducing agent and water to form a suspension, carrying out liquid phase reduction reaction on the suspension by using a microwave reactor, wherein the microwave power is 500-1000W, the microwave time is 5-15 min, cooling after the reaction is finished, repeatedly washing the obtained product for 2-5 times by using deionized water and ethanol, and carrying out suction filtration and vacuum drying to obtain the conductive microcapsule; the mass ratio of the microcapsule, the metal salt, the reducing agent and the water is 1 (0.5-2) to (0.05-0.1) to (50-150); the metal salt is at least one selected from the group consisting of silver acetate, silver nitrate, copper sulfate and copper acetate.
2. The conductive microcapsule for a self-repairing graphene conductive film according to claim 1, wherein the mass ratio of the core material to the wall material is (0.5-2): 1; the mass ratio of the total mass of the core material and the wall material to the conductive metal particles is 1 (0.5-2).
3. The conductive microcapsule for a self-repairing graphene conductive film according to claim 1, wherein the conductive microcapsule has a particle size of 2-20 μm; the particle size of the conductive metal particles is 20-150 nm.
4. The preparation method of the conductive microcapsule for the self-repairing graphene conductive film, disclosed by any one of claims 1 to 3, is characterized by comprising the following steps of:
s1, uniformly melting and blending the graphene and the low-melting-point polyurethane according to the mass ratio (0.05-0.2) to 1, wherein the melting point of the low-melting-point polyurethane is 50-60 ℃, so as to obtain the composite material of the graphene and the low-melting-point polyurethane;
s2, adjusting the pH value of a mixed aqueous solution of melamine and formaldehyde to 8-9, and stirring at the temperature of 60-80 ℃ at the rotating speed of 400-600 r/min until the solution is transparent to obtain a prepolymer solution; the mass ratio of the melamine to the formaldehyde to the water in the system is 1 (1-3) to 15-25;
s3, stirring the composite material of the graphene and the low-melting-point polyurethane obtained in the step S1 and an emulsifier at the temperature of 60-80 ℃ for 0.1-1 h, then adding water, and stirring and emulsifying at the rotating speed of 10000-20000 r/min for 5-20 min to obtain a stable oil-in-water emulsion; the mass ratio of the composite material of graphene and low-melting-point polyurethane to the emulsifier to water is 1 (0.02-0.1) to 10-30;
s4, adjusting the pH value of the oil-in-water type emulsion obtained in the step S3 to 4-5, slowly dropwise adding the prepolymer solution obtained in the step S2 into the emulsion, simultaneously reducing the stirring speed to 100-200 r/min, after dropwise adding of the prepolymer solution is finished, preserving heat for 2-4 h at 60-80 ℃, cooling, repeatedly washing the obtained product with deionized water and petroleum ether for 2-5 times, and performing suction filtration and vacuum drying to obtain microcapsules;
s5, blending the microcapsule obtained in the step S4, metal salt, a reducing agent and water to form a suspension, carrying out liquid phase reduction reaction on the suspension by using a microwave reactor, wherein the microwave power is 500-1000W, the microwave time is 5-15 min, cooling after the reaction is finished, repeatedly washing the obtained product for 2-5 times by using deionized water and ethanol, and carrying out suction filtration and vacuum drying to obtain the conductive microcapsule; the mass ratio of the microcapsule, the metal salt, the reducing agent and the water is 1 (0.5-2) to (0.05-0.1) to (50-150); the metal salt is at least one selected from the group consisting of silver acetate, silver nitrate, copper sulfate and copper acetate.
5. The application of the conductive microcapsule for the self-repairing graphene conductive film as claimed in any one of claims 1 to 3 as a self-repairing material.
6. The graphene conductive ink is characterized by being prepared from the following raw materials in parts by mass:
the conductive microcapsule for the self-repairing graphene conductive film is as claimed in any one of claims 1 to 3.
7. The graphene conductive ink according to claim 6, wherein the aqueous resin is at least one selected from the group consisting of an aqueous urethane resin, an aqueous acrylic resin, and an aqueous acrylic modified urethane resin; the graphene is selected from at least one of physical graphene, CVD graphene and reduced graphene oxide.
8. A method for preparing the graphene conductive ink according to claim 6 or 7, wherein the method comprises the following steps:
s1, sequentially adding a dispersing agent, graphene and a defoaming agent into water, mixing, and carrying out wet grinding for 0.5-3 h by using a nano sand mill to obtain uniform graphene slurry;
and S2, sequentially adding the graphene slurry obtained in the step S1 and the conductive microcapsules into water-based resin, stirring and blending uniformly at a low speed, adding a thickening agent to adjust the viscosity of the system to 10,000-50,000 cP, filtering and discharging to obtain the graphene conductive ink.
9. A self-repairing graphene conductive film is characterized in that the self-repairing graphene conductive film is prepared by coating and curing the graphene conductive ink of claim 6 or 7.
10. A self-repairing method of a graphene conductive film is characterized in that the graphene conductive film is prepared by coating and curing the graphene conductive ink of claim 6 or 7, and the self-repairing method comprises the step of heating the graphene conductive film to 50-80 ℃ and keeping the temperature for 1-3 hours when the electrical performance of the graphene conductive film is reduced.
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