CN112778858A - Water-based electromagnetic shielding coating material and preparation method thereof - Google Patents

Water-based electromagnetic shielding coating material and preparation method thereof Download PDF

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CN112778858A
CN112778858A CN202011638790.8A CN202011638790A CN112778858A CN 112778858 A CN112778858 A CN 112778858A CN 202011638790 A CN202011638790 A CN 202011638790A CN 112778858 A CN112778858 A CN 112778858A
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electromagnetic shielding
coating material
water
shielding coating
aqueous
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CN112778858B (en
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马建中
卫林峰
张文博
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Shaanxi University of Science and Technology
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    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D133/00—Coating compositions based on homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Coating compositions based on derivatives of such polymers
    • C09D133/04—Homopolymers or copolymers of esters
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    • C09D5/00—Coating compositions, e.g. paints, varnishes or lacquers, characterised by their physical nature or the effects produced; Filling pastes
    • C09D5/24—Electrically-conducting paints
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D7/00—Features of coating compositions, not provided for in group C09D5/00; Processes for incorporating ingredients in coating compositions
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    • C09D7/00—Features of coating compositions, not provided for in group C09D5/00; Processes for incorporating ingredients in coating compositions
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    • C08K2201/00—Specific properties of additives
    • C08K2201/011—Nanostructured additives

Abstract

The invention discloses a water-based electromagnetic shielding coating material and a preparation method thereof, belonging to the technical field of water-based coating preparation. According to the invention, the polydopamine modified nano-carbon material is endowed with water dispersibility, and after the pH values of the polydopamine modified nano-carbon material filler and the aqueous anionic polyacrylate emulsion are respectively adjusted, the polydopamine modified nano-carbon material filler and the aqueous anionic polyacrylate emulsion are blended, compounded and coated to prepare the aqueous electromagnetic shielding coating material with the mechanical property enhanced by adjusting and controlling the pH. According to the method, the pH value of the formed film is adjusted, and the natural reduction of the pH value during water evaporation is utilized to promote the ionized phenolic hydroxyl groups on the polydopamine to be protonated again, so that the interaction between the polydopamine modified nano-carbon material and the polyacrylate is induced to be changed from electrostatic repulsion to hydrogen bond interaction, the contradiction between filler dispersibility and interface interaction in the existing scheme is solved, and the mechanical property of the aqueous electromagnetic shielding coating material is enhanced.

Description

Water-based electromagnetic shielding coating material and preparation method thereof
Technical Field
The invention belongs to the technical field of preparation of water-based coatings, and relates to a water-based electromagnetic shielding coating material and a preparation method thereof.
Background
With the heavy use of communication equipment, electromagnetic pollution is increasingly serious, and the health of human bodies and the operation of the equipment are seriously damaged. Therefore, the water-based electromagnetic shielding coating is widely applied to the field of electromagnetic interference prevention of product shells of computers, mobile phones, precision instruments, medical instruments and the like. The novel carbon materials such as graphene and carbon nano tubes are very suitable for being used as conductive fillers of the water-based electromagnetic shielding coating material due to the advantages of low density, good conductivity and the like. However, due to the addition of a large amount of conductive filler, the mechanical properties of the composite coating are greatly reduced, so that the coating is easy to crack and fall off, and the service performance and the service life of the coating are seriously influenced. The current thinking for improving the mechanical property of the coating mainly comprises the following steps: 1) reducing the addition amount of the conductive filler; 2) the interface action between the matrix and the conductive filler is enhanced, and the high-efficiency transfer of stress load is promoted. The former increases the thickness of the barrier coating used, making the coating cumbersome and not practical. The latter is the main direction of current research, and the related interface action includes pi-pi action, hydrogen bond action, etc. For example, the inventor uses styrene as a hard monomer in the composition of polyacrylate material in the past, and utilizes the pi-pi action of styrene and graphene to improve the mechanical property of the aqueous electromagnetic shielding coating, and the related work is published in Carbon (DOI:10.1016/j. carbon.2019.04.058). However, similar to other existing methods, the pi-pi effect, the hydrogen bond effect and the electrostatic attraction effect can only improve the final interaction between the conductive filler and the aqueous polymer matrix, and the dispersibility of the filler in the matrix introduction process is difficult to improve. And the strong hydrogen bond and electrostatic attraction can cause the agglomeration of the conductive filler and the aqueous polymer matrix in the blending process, which is more unfavorable for the improvement of the mechanical property of the coating. Therefore, the dispersibility of the conductive filler in the aqueous polymer matrix must be taken into consideration simultaneously when introducing the interfacial effect.
The existing method for introducing the interface effect cannot balance the filler dispersion and the interface interaction, and is difficult to efficiently improve the mechanical property of the water-based electromagnetic shielding coating.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention aims to provide a water-based electromagnetic shielding coating material and a preparation method thereof, which solve the problem of balance between dispersion of a conductive filler and interface interaction in the preparation process, and finally prepare the water-based electromagnetic shielding coating material with efficiently improved mechanical properties.
In order to achieve the purpose, the invention adopts the following technical scheme to realize the purpose:
the invention discloses a preparation method of a water-based electromagnetic shielding coating material, which comprises the following steps:
1) modifying a nano carbon material by utilizing the self-polymerization reaction of dopamine hydrochloride to prepare a polydopamine modified nano carbon material, and dispersing the obtained polydopamine modified nano carbon material in water to prepare a dispersion liquid;
adjusting the pH value of the obtained dispersion liquid to x by adopting a pH value regulator, wherein the x is more than M and less than 7, and obtaining the stably dispersed dispersion liquid; adjusting the pH value of the water-based anionic polyacrylate emulsion to y by adopting a pH value regulator, wherein the M is more than and less than 7, and obtaining the stably dispersed water-based anionic polyacrylate emulsion;
wherein the pH value M is: the pH value of the agglomeration phenomenon of a composite system blended by the obtained dispersion liquid and the water-based anionic polyacrylate emulsion is shown;
2) blending the stably dispersed dispersion liquid obtained in the step 1) and the stably dispersed water-based anionic polyacrylate emulsion obtained in the step 1) to obtain a composite emulsion, and coating the composite emulsion to obtain the water-based electromagnetic shielding coating material.
Preferably, in the step 1), the pH value M of the composite system in which the obtained dispersion liquid and the aqueous anionic polyacrylate emulsion are blended is obtained by the following operations:
and blending the obtained dispersion liquid and the water-based anionic polyacrylate emulsion to obtain a composite system, adjusting the pH value of the obtained composite system by adopting a pH value regulator until the obtained composite system has an agglomeration phenomenon, and recording the pH value of the obtained composite system when the agglomeration phenomenon occurs as M.
Preferably, in the step 1), the mass ratio of the dopamine hydrochloride to the nanocarbon material is (0.2-0.5): 1.
Preferably, the nano carbon material is one or a mixture of graphene and carbon nanotubes.
Preferably, the concentration of the dispersion is 15-25 mg/g.
Preferably, the pH adjustor is a strong acid solution or a strong base solution.
Further preferably, the strong acid is a 5-10 wt% sulfuric acid solution, and the strong base is a 1-4 wt% sodium hydroxide solution.
Preferably, in the obtained aqueous electromagnetic shielding coating material, the mass of the nano carbon material accounts for 5-50 wt% of the total mass of the obtained aqueous electromagnetic shielding coating material.
Preferably, the aqueous anionic polyacrylate emulsion is anionic polyacrylate emulsion Youwan 141, anionic polyacrylate emulsion Mage AR-1053, anionic polyacrylate emulsion Mage AR-101 or anionic polyacrylate emulsion Mage AR-103.
Preferably, the coating is brush, spray or roller.
The invention also discloses the aqueous electromagnetic shielding coating material prepared by the preparation method.
Compared with the prior art, the invention has the following beneficial effects:
the invention discloses a preparation method of a water-based electromagnetic shielding coating material, and relates to a preparation method of a water-based electromagnetic shielding coating for enhancing mechanical properties. The method comprises the steps of modifying a nano carbon material by polydopamine, and respectively regulating and controlling the pH values of a dispersion liquid and a water-based anionic polyacrylate emulsion: the ionization and protonation of phenolic hydroxyl on polydopamine are regulated and controlled by the change of pH value, the phenolic hydroxyl is ionized to be negatively charged when the pH value is higher, and the polydopamine modified nano-carbon material and the aqueous anionic polyacrylate emulsion keep stable dispersion under the action of electrostatic repulsion. In the drying process of the obtained composite emulsion after coating, the hydrogen ion concentration in the composite emulsion is gradually increased, and the pH value is naturally reduced, so that the ionized phenolic hydroxyl on the polydopamine is induced to be protonated again, and the phenolic hydroxyl and the ester carbonyl in the polyacrylate generate hydrogen bond interaction, and the viscosity of the composite emulsion is increased along with the evaporation of water, so that the agglomeration of the nano carbon material is avoided. In addition, the pH value is adjusted to be larger than the pH value M with the agglomeration phenomenon and smaller than 7, so that the electrostatic repulsion can play a leading role and the uniform dispersion of the system is maintained; and with the evaporation of water, the pH value is reduced, the viscosity of the system is increased, and the agglomeration of the filler is avoided. In addition, the water dispersibility and the interaction groups of the nano carbon material are endowed through Polydopamine (PDA) modification, the dispersibility of the nano carbon material in the aqueous polyacrylate emulsion is greatly improved, the interfacial interaction of the nano carbon material and polyacrylate is simply and efficiently improved through the operation of adjusting the pH value, and finally the high-strength aqueous electromagnetic shielding coating material is obtained. According to the preparation method, through polydopamine modification and pH value regulation of the nano-carbon material, the change of pH from high to low in the drying process of the composite emulsion in the pre-forming stage of the coating material is realized, the conversion from electrostatic repulsion force leading to hydrogen bond action leading is promoted, the stable dispersion of the nano-carbon material during coating is maintained, and the strong interaction between polyacrylate and the nano-carbon material after the finally prepared aqueous electromagnetic shielding coating material is dried is ensured, so that the mechanical property of the obtained aqueous electromagnetic shielding coating material is improved, and the aqueous electromagnetic shielding coating material with the mechanical property regulated through the pH value is prepared. However, in the prior art, the introduction of an interaction mode often makes it difficult to simultaneously consider the dispersion problem and the final interaction strength when the carbon material and the aqueous emulsion are blended, and the mechanical properties of the coating layer are difficult to be efficiently improved.
Furthermore, a small amount of dispersion liquid is blended with the aqueous anionic polyacrylate emulsion, and the pH value is adjusted, so that the pH value M of the composite system agglomeration can be easily obtained. On the basis, the interfacial interaction of the filler polydopamine modified nano-carbon material and polyacrylate in the aqueous anionic polyacrylate emulsion is changed into hydrogen bond leading, so that the mechanical property is enhanced. In the traditional process, the pH value of the anionic emulsion is usually directly adjusted to be alkalescent about 8 so as to ensure that electrostatic repulsion exists in the system all the time, the system is maintained to be stably dispersed without agglomeration, and the interfacial interaction between the filler and the polyacrylate is weakened.
Further, the pH value regulator is selected to be strong acid solution or strong alkali solution, so that the system stability of the pH value regulation operation is ensured.
Furthermore, by selecting a sulfuric acid solution and a sodium hydroxide solution as pH value regulators, the volatilization problem caused by using hydrochloric acid and ammonia water is avoided, and the hydrogen ion concentration can be ensured to change along with the evaporation of water.
The invention also discloses the aqueous electromagnetic shielding coating material prepared by the preparation method. By the method, the electrostatic repulsion and the hydrogen bond function can be regulated and controlled by regulating the pH value of the aqueous polymer coating during film forming, so that the electrostatic repulsion plays a main role in the dispersion process of the conductive filler, and good dispersibility is obtained; in the film forming process and the finally obtained aqueous electromagnetic shielding coating material, the hydrogen bond action gradually plays a main role, the interaction between the conductive filler and the aqueous polymer matrix is enhanced, the problem of the balance of filler dispersion and interface interaction is further solved, and the aqueous electromagnetic shielding coating material with the efficiently improved mechanical property is finally prepared.
Drawings
FIG. 1 is a stress-strain curve of the aqueous EMI shielding coating material prepared in example 1;
FIG. 2 is a graph showing electric field intensity before and after finishing of the leather-like shield of the aqueous electromagnetic shielding coating material prepared in example 1;
FIG. 3 is a stress-strain curve of the aqueous EMI shielding coating material prepared in example 2;
FIG. 4 shows electric field intensity before and after the application pattern of the aqueous electro-magnetic shielding coating material prepared in example 2.
Detailed Description
In order to make the technical solutions of the present invention better understood, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
It should be noted that the terms "first," "second," and the like in the description and claims of the present invention and in the drawings described above are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used is interchangeable under appropriate circumstances such that the embodiments of the invention described herein are capable of operation in sequences other than those illustrated or described herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.
The invention discloses a water-based electromagnetic shielding coating material with enhanced mechanical property by regulating pH and a preparation method thereof, and the preparation method comprises the following steps:
(1) modifying the nano-carbon material by utilizing the self-polymerization reaction of dopamine hydrochloride to prepare a polydopamine modified nano-carbon material;
(2) dispersing the polydopamine modified nano-carbon material prepared in the step (1) in water to prepare a dispersion liquid with a certain concentration, blending a small amount of the dispersion liquid with an aqueous anionic polyacrylate emulsion to obtain a mixed liquid, adjusting the pH value of the mixed liquid, and observing and recording the pH value M of the composite system with agglomeration;
(3) respectively adjusting the pH values of the aqueous anionic polyacrylate emulsion and the dispersion liquid of the polydopamine modified nano-carbon material by using a strong acid solution or a strong alkali solution until the pH values of the aqueous anionic polyacrylate emulsion and the dispersion liquid of the polydopamine modified nano-carbon material are larger than the pH value of the composite system agglomeration (usually about 0.1-0.5), and simultaneously keeping the pH values of the aqueous anionic polyacrylate emulsion and the dispersion liquid of the polydopamine modified nano-carbon material to be smaller than 7;
(4) and then adding a certain amount of polydopamine modified nano carbon material dispersion liquid into the aqueous anionic polyacrylate emulsion for mechanical blending to obtain a composite emulsion, and coating the mixed composite emulsion to obtain the aqueous electromagnetic shielding coating material with mechanical property regulated by pH value.
Preferably, the mass ratio of the dopamine hydrochloride to the nano carbon material is (0.2-0.5): 1; the nano carbon material is a mixture consisting of one or more of graphene or carbon nano tubes; the concentration of the dispersion liquid of the polydopamine modified nano carbon material is 15-25 mg/g; the water-based anionic polyacrylate emulsion is anionic polyacrylate emulsion derivative 141, anionic polyacrylate emulsion Mage AR-1053, anionic polyacrylate emulsion Mage AR-101 or anionic polyacrylate emulsion Mage AR-103; the strong acid solution is a 5-10 wt% sulfuric acid solution, and the strong base solution is a 1-4 wt% sodium hydroxide solution; in the obtained aqueous electromagnetic shielding coating material, the amount of the polydopamine modified nano carbon material accounts for 5-50 wt% of the total mass of the obtained aqueous electromagnetic shielding coating material; the coating mode is brush coating, spray coating or roller coating.
The invention will be further explained with reference to the drawings and the specific embodiments.
Example 1
Preparing the water-based electromagnetic shielding coating material with the mechanical property enhanced by regulating and controlling the pH value:
(1) adding 0.25g of dopamine hydrochloride into 150mL of Tris buffer solution and 50mL of ethanol at room temperature, modifying 0.5g of graphene nanosheet by utilizing the self-polymerization reaction of the dopamine hydrochloride under the alkalescent condition (the pH value is 8.5), reacting for 24 hours, performing suction filtration, and leaching with water to obtain the polydopamine modified graphene nanosheet. Then, shearing and dispersing the polydopamine modified graphene nanosheets in 30g of water at a high speed to prepare a dispersion liquid with the concentration of 25mg/g, wherein the shearing rate is 5000rpm, and the time is 10 minutes;
(2) and (3) mixing 1g of aqueous dispersion of polydopamine modified graphene nanosheets and 5g of anionic polyacrylate emulsion derived clay 141 under magnetic stirring, and adjusting the pH value with dilute sulfuric acid and sodium hydroxide solution to obtain the pH value of the composite system agglomeration of 6.3.
(3) And (3) adjusting the pH value of the 29g of aqueous dispersion of the polydopamine modified graphene nanosheet and 5.88g of anionic polyacrylate emulsion derivative 141 to 6.8 by using 5 wt% of dilute sulfuric acid solution and 4 wt% of sodium hydroxide solution, and uniformly blending the aqueous dispersion of the polydopamine modified graphene nanosheet and the 5.88g of anionic polyacrylate emulsion derivative 141 under water bath ultrasound, wherein the ultrasound power is 300W, and the ultrasound time is 10min, so that the dark gray aqueous electromagnetic shielding composite emulsion with the mechanical property enhanced by regulating and controlling the pH is obtained. (the mass of the polydopamine modified nano-carbon material accounts for 25.6 wt% of the total mass of the obtained aqueous electromagnetic shielding coating material)
The composite emulsion is used for drying, film forming and spraying:
the composite emulsion is dried to form a film, so that the water-based electromagnetic shielding coating material with the mechanical property enhanced by regulating and controlling the pH value is obtained, and the mechanical property of the material is tested by using a universal tensile machine. Spraying the composite emulsion on a leather substrate, wherein the sizing amount is 200g/m2And drying the coated leather sample in an oven at 105 ℃ for 3 minutes, taking out, and testing the shielding effect of the leather by using an electromagnetic wave detector.
As shown in fig. 1, the tensile strength of the coating material prepared in example 1 was as high as 8.3MPa, and the film-forming tensile strength of the ribbon 141 was about 2MPa, and the tensile strength of the aqueous electro-magnetic shielding coating material was 4.15 times that of the original substrate. As shown in FIG. 2, the electric field intensity before the coating of leather and after the coating of leather was 241V/m and the electric field intensity after the coating of leather and after the coating of leather was 0V/m.
Example 2
Preparing the water-based electromagnetic shielding coating material with the mechanical property enhanced by regulating and controlling the pH value:
(1) adding 0.5g of dopamine hydrochloride into 300mL of Tris buffer solution and 100mL of ethanol at room temperature, modifying 2.5g of carbon nanotubes by utilizing the autopolymerization reaction of the dopamine hydrochloride under the alkalescent condition (the pH value is 8.5), filtering after reacting for 24 hours, and leaching with water to prepare the polydopamine modified carbon nanotubes. Then, the polydopamine modified carbon nano tube is sheared and dispersed in 197g of water at a high speed to prepare dispersion liquid with the concentration of 15mg/g, the shearing rate is 5000rpm, and the time is 10 minutes;
(2) 1g of polydopamine modified carbon nanotube aqueous dispersion and 5g of anionic polyacrylate emulsion Mage AR-1053 are mixed under magnetic stirring, and the pH value is adjusted by dilute sulfuric acid and sodium hydroxide solution, so that the pH value of the composite system aggregate is 6.1.
(3) And (2) adjusting the pH value of the residual aqueous dispersion of the polydopamine-modified carbon nano tube and 8.52g of anionic polyacrylate emulsion Mage AR-1053 to 6.3 by using 10 wt% of dilute sulfuric acid solution and 1 wt% of sodium hydroxide solution, and uniformly blending the two under water bath ultrasound, wherein the ultrasound power is 300W, and the ultrasound time is 10min, so that the black aqueous electromagnetic shielding composite emulsion with the mechanical property enhanced by regulating and controlling the pH is obtained. (the mass of the polydopamine modified nano-carbon material accounts for 50 wt% of the total mass of the obtained aqueous electromagnetic shielding coating material)
Drying film forming and roll coating of the composite emulsion are carried out:
the composite emulsion is dried to form a film, so that the water-based electromagnetic shielding coating material with the mechanical property enhanced by regulating and controlling the pH value is obtained, and the mechanical property of the material is tested by using a universal tensile machine. The composite emulsion is coated on a paper substrate in a rolling way, and the sizing amount is 150g/m2And drying the coated paper pattern in an oven at 60 ℃ for 10 minutes, taking out, and testing the shielding effect of the coated paper pattern by using an electromagnetic wave detector.
As shown in fig. 3, the tensile strength of the coating material prepared in example 2 was as high as 6.9MPa, while the film-forming tensile strength of Mage AR-1053 was about 1.8MPa, and the tensile strength of the aqueous electro-magnetic shielding coating material was 3.83 times that of the original substrate. As shown in FIG. 4, the electric field intensity before shielding with the paper pattern after coating was 284V/m, and the electric field intensity after shielding was 0V/m.
Example 3
Preparing the water-based electromagnetic shielding coating material with the mechanical property enhanced by regulating and controlling the pH value:
(1) adding 0.3g of dopamine hydrochloride into 300mL of Tris buffer solution and 100mL of ethanol at room temperature, modifying 1g of graphene nanosheet by utilizing the self-polymerization reaction of the dopamine hydrochloride under the alkalescent condition (the pH value is 8.5), reacting for 24 hours, performing suction filtration, and leaching with water to obtain the polydopamine modified graphene nanosheet. Then, the polydopamine modified carbon nano tube is sheared and dispersed in 63.7g of water at a high speed to prepare dispersion liquid with the concentration of 20mg/g, the shearing rate is 5000rpm, and the time is 10 minutes;
(2) 1g of polydopamine modified carbon nanotube aqueous dispersion and 5g of anionic polyacrylate emulsion Mage AR-101 are mixed under magnetic stirring, and the pH value is adjusted by using dilute sulfuric acid and sodium hydroxide solution, so that the pH value of the composite system agglomeration is 5.8.
(3) And (2) adjusting the pH value of the residual aqueous dispersion of the polydopamine-modified carbon nano tube and 68.1g of anionic polyacrylate emulsion Mage AR-101 to 6.3 by using 8 wt% of dilute sulfuric acid solution and 2 wt% of sodium hydroxide solution, and uniformly blending the two under water bath ultrasound, wherein the ultrasound power is 300W, and the ultrasound time is 10min, so that the gray aqueous electromagnetic shielding composite emulsion with the mechanical property enhanced by regulating and controlling the pH value is obtained. (the mass of the polydopamine modified nano-carbon material accounts for 5 wt% of the total mass of the obtained aqueous electromagnetic shielding coating material)
The composite emulsion is coated on a base material to obtain the water-based electromagnetic shielding coating material with the mechanical property enhanced by regulating and controlling the pH value. After the composite emulsion is formed into a film and is dried, the tensile strength of the composite emulsion is 9MPa through a universal tensile machine test, the film-forming tensile strength of Mage AR-101 is about 2.4MPa, and the tensile strength of the water-based electromagnetic shielding coating material is 3.75 times of that of an original base material. And brushing the composite emulsion on a wood board, and testing the shielding effect of the coated wood board by using an electromagnetic wave detector after drying, wherein the electric field strengths before and after shielding are 241V/m and 0V/m respectively.
Example 4
Preparing the water-based electromagnetic shielding coating material with the mechanical property enhanced by regulating and controlling the pH value:
(1) adding 1g of dopamine hydrochloride into 600mL of Tris buffer solution and 200mL of ethanol at room temperature, modifying 3g of carbon nanotubes by utilizing the autopolymerization reaction of the dopamine hydrochloride under the alkalescent condition (the pH value is 8.5), reacting for 24 hours, performing suction filtration, and leaching with water to obtain the polydopamine modified graphene nanosheet. Then, the polydopamine modified carbon nano tube is sheared and dispersed in 196g of water at a high speed to prepare dispersion liquid with the concentration of 20mg/g, the shearing rate is 5000rpm, and the time is 10 minutes;
(2) 1g of polydopamine modified carbon nanotube aqueous dispersion and 5g of anionic polyacrylate emulsion Mage AR-103 are mixed under magnetic stirring, and the pH value is adjusted by using dilute sulfuric acid and sodium hydroxide solution, so that the pH value of the composite system agglomeration is 5.8.
(3) And (3) adjusting the pH value of the residual aqueous dispersion of the polydopamine-modified carbon nano tube and 26.53g of anionic polyacrylate emulsion Mage AR-103 to 6.3 by using 7 wt% of dilute sulfuric acid solution and 3 wt% of sodium hydroxide solution, and uniformly blending the two under water bath ultrasound, wherein the ultrasound power is 300W, and the ultrasound time is 10min, so that the black aqueous electromagnetic shielding composite emulsion with the mechanical property enhanced by regulating and controlling the pH is obtained. The composite emulsion is coated on a base material to obtain the water-based electromagnetic shielding coating material with the mechanical property enhanced by regulating and controlling the pH value. (the mass of the polydopamine modified nano-carbon material accounts for 30 wt% of the total mass of the obtained aqueous electromagnetic shielding coating material)
After the composite emulsion is formed into a film and is dried, the tensile strength of the composite emulsion is 11.4MPa through a universal tensile machine test, the film-forming tensile strength of Mage AR-103 is about 2.1MPa, and the tensile strength of the water-based electromagnetic shielding coating material is 5.43 times of that of an original base material. Brushing the composite emulsion on a plastic PVC sheet, drying, and testing the shielding effect of the coated PVC by using an electromagnetic wave detector, wherein the electric field intensity before and after shielding is 256V/m and 0V/m respectively.
Example 5
Preparing the water-based electromagnetic shielding coating material with the mechanical property enhanced by regulating and controlling the pH value:
(1) adding 1g of dopamine hydrochloride into 150mL of Tris buffer solution and 50mL of ethanol at room temperature, modifying 1g of graphene nanosheet and 1g of carbon nanotube by utilizing the self-polymerization reaction of the dopamine hydrochloride under the alkalescent condition (the pH value is 8.5), reacting for 24 hours, performing suction filtration, and leaching with water to obtain the polydopamine modified nanocarbon material. Then, the polydopamine modified nano carbon material is sheared and dispersed in 77g of water at a high speed to prepare dispersion liquid with the concentration of 25mg/g, the shearing rate is 5000rpm, and the time is 10 minutes;
(2) 1g of aqueous dispersion of the polydopamine modified nanocarbon material and 5g of anionic polyacrylate emulsion Mage AR-101 are mixed under magnetic stirring, and the pH value is adjusted by dilute sulfuric acid and sodium hydroxide solution, so that the pH value of the composite system agglomeration is 5.8.
(3) And (3) adjusting the pH value of the remaining aqueous dispersion of the polydopamine modified nano carbon material and 22.57g of anionic polyacrylate emulsion Mage AR-101 to 6.3 by using 9 wt% of dilute sulfuric acid solution and 2 wt% of sodium hydroxide solution, and uniformly blending the aqueous dispersion of the polydopamine modified nano carbon material and the anionic polyacrylate emulsion Mage AR-101 under water bath ultrasound, wherein the ultrasound power is 300W, and the ultrasound time is 10min, so that the black-gray waterborne electromagnetic shielding composite emulsion with mechanical property regulated and controlled based on the pH value is obtained. The composite emulsion is coated on a base material to obtain the water-based electromagnetic shielding coating material with the mechanical property enhanced by regulating and controlling the pH value. (the mass of the polydopamine modified nano-carbon material accounts for 27.5 wt% of the total mass of the obtained aqueous electromagnetic shielding coating material)
After the composite emulsion is formed into a film and dried, the tensile strength of the composite emulsion is tested to be 8.5MPa by a universal tensile machine. Spraying the composite emulsion on plastic PC, drying, and testing the shielding effect of the coated PVC by using an electromagnetic wave detector, wherein the electric field strengths before and after shielding are 294V/m and 0V/m respectively.
Example 6
Preparing the water-based electromagnetic shielding coating material with the mechanical property enhanced by regulating and controlling the pH value:
(1) adding 2g of dopamine hydrochloride into 400mL of Tris buffer solution and 200mL of ethanol at room temperature, modifying 3g of graphene nanosheet and 7g of carbon nanotube by utilizing the self-polymerization reaction of the dopamine hydrochloride under the alkalescent condition (the pH value is 8.5), reacting for 24 hours, performing suction filtration, and leaching with water to obtain the polydopamine modified nanocarbon material. Then, the polydopamine modified nano carbon material is sheared and dispersed in 588g of water at a high speed to prepare dispersion liquid with the concentration of 20mg/g, the shearing rate is 5000rpm, and the time is 10 minutes;
(2) 1g of aqueous dispersion of the polydopamine modified nanocarbon material and 5g of anionic polyacrylate emulsion Yoigong 141 are mixed under magnetic stirring, and the pH value is adjusted by dilute sulfuric acid and sodium hydroxide solution, so that the pH value of the composite system agglomeration is 6.
(3) And (3) adjusting the pH value of the remaining aqueous dispersion of the polydopamine modified nanocarbon material and 183.5g of anionic polyacrylate emulsion derivative 141 to 6.5 by using 6 wt% of dilute sulfuric acid solution and 3 wt% of sodium hydroxide solution, and uniformly blending the aqueous dispersion of the polydopamine modified nanocarbon material and the 183.5g of anionic polyacrylate emulsion derivative 141 under water bath ultrasound, wherein the ultrasound power is 300W, and the ultrasound time is 10min, so that the black-gray aqueous electromagnetic shielding composite emulsion with the mechanical property enhanced by regulating and controlling the pH is obtained. The composite emulsion is coated on a base material to obtain the water-based electromagnetic shielding coating material with the mechanical property enhanced by regulating and controlling the pH value. (the mass of the polydopamine modified nano-carbon material accounts for 13.8 wt% of the total mass of the obtained aqueous electromagnetic shielding coating material)
After the composite emulsion is formed into a film and is dried, the tensile strength of the composite emulsion is 14.3MPa through a universal tensile machine test, the film-forming tensile strength of the Nippon 141 is about 2MPa, and the tensile strength of the water-based electromagnetic shielding coating material is 7.15 times of the tensile strength of an original base material. And (3) rolling and coating the composite emulsion on a plastic PP sheet, drying, and testing the shielding effect of the coated PP by using an electromagnetic wave detector, wherein the electric field intensity before and after shielding is 214V/m and 0V/m respectively.
Specifically, in the embodiments of the present invention, the tensile strength of the aqueous electromagnetic shielding coating material is 3.8 to 7.2 times of the tensile strength of the original base material.
In summary, the invention discloses a water-based electromagnetic shielding coating material and a preparation method thereof, and belongs to the technical field of water-based coating preparation. According to the invention, the polydopamine modified nano-carbon material is endowed with water dispersibility, and after the pH values of the polydopamine modified nano-carbon material filler and the aqueous anionic polyacrylate emulsion are respectively adjusted, the polydopamine modified nano-carbon material filler and the aqueous anionic polyacrylate emulsion are blended, compounded and coated to prepare the aqueous electromagnetic shielding coating material with the mechanical property enhanced by adjusting and controlling the pH. According to the method, the pH value of the formed film is adjusted, and the natural reduction of the pH value during water evaporation is utilized to promote the ionized phenolic hydroxyl groups on the polydopamine to be protonated again, so that the interaction between the polydopamine modified nano-carbon material and the polyacrylate is induced to be changed from electrostatic repulsion to hydrogen bond interaction, the contradiction between filler dispersibility and interface interaction in the existing scheme is solved, and the mechanical property of the aqueous electromagnetic shielding coating material is enhanced.
The above-mentioned contents are only for illustrating the technical idea of the present invention, and the protection scope of the present invention is not limited thereby, and any modification made on the basis of the technical idea of the present invention falls within the protection scope of the claims of the present invention.

Claims (9)

1. A preparation method of a water-based electromagnetic shielding coating material is characterized by comprising the following steps:
1) modifying a nano carbon material by utilizing the self-polymerization reaction of dopamine hydrochloride to prepare a polydopamine modified nano carbon material, and dispersing the obtained polydopamine modified nano carbon material in water to prepare a dispersion liquid;
adjusting the pH value of the obtained dispersion liquid to x by adopting a pH value regulator, wherein the x is more than M and less than 7, and obtaining the stably dispersed dispersion liquid; adjusting the pH value of the water-based anionic polyacrylate emulsion to y by adopting a pH value regulator, wherein the M is more than and less than 7, and obtaining the stably dispersed water-based anionic polyacrylate emulsion;
wherein the pH value M is: the pH value of the agglomeration phenomenon of a composite system blended by the obtained dispersion liquid and the water-based anionic polyacrylate emulsion is shown;
2) blending the stably dispersed dispersion liquid obtained in the step 1) and the stably dispersed water-based anionic polyacrylate emulsion obtained in the step 1) to obtain a composite emulsion, and coating the composite emulsion to obtain the water-based electromagnetic shielding coating material.
2. The method for preparing the aqueous electromagnetic shielding coating material of claim 1, wherein the pH M at which the complex system of the dispersion liquid and the aqueous anionic polyacrylate emulsion is agglomerated in step 1) is obtained by:
and blending the obtained dispersion liquid and the water-based anionic polyacrylate emulsion to obtain a composite system, adjusting the pH value of the obtained composite system by adopting a pH value regulator until the obtained composite system has an agglomeration phenomenon, and recording the pH value of the obtained composite system when the agglomeration phenomenon occurs as M.
3. The method for preparing the aqueous electromagnetic shielding coating material according to claim 1, wherein the mass ratio of the dopamine hydrochloride to the nanocarbon material in the step 1) is (0.2-0.5): 1.
4. The method for preparing an aqueous electromagnetic shielding coating material of claim 1, wherein the nano-carbon material is a mixture of one or more of graphene and carbon nanotubes.
5. The method for preparing an aqueous electromagnetic shielding coating material of claim 1, wherein the concentration of the dispersion is 15-25 mg/g.
6. The method for preparing an aqueous electromagnetic shielding coating material of claim 1, wherein the pH adjusting agent is a strong acid solution or a strong alkali solution.
7. The method for preparing an aqueous electromagnetic shielding coating material of claim 6, wherein the strong acid solution is 5 to 10 wt% sulfuric acid solution, and the strong base solution is 1 to 4 wt% sodium hydroxide solution.
8. The method for preparing an aqueous electromagnetic shielding coating material according to claim 1, wherein the mass of the polydopamine modified nano-carbon material in the aqueous electromagnetic shielding coating material accounts for 5-50 wt% of the total mass of the aqueous electromagnetic shielding coating material.
9. An aqueous electromagnetic shielding coating material prepared by the preparation method of any one of claims 1 to 8.
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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114479242A (en) * 2022-01-28 2022-05-13 泰州泽钰新材料科技有限公司 Conductive bio-based plastic and preparation method and application thereof

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CN108276577A (en) * 2018-02-02 2018-07-13 天津工业大学 Poly-dopamine modified lithium carbon nanotube graphene/polyimide composite material and preparation method thereof
CN108951282A (en) * 2018-06-12 2018-12-07 中国电子科技集团公司第三十三研究所 A kind of graphene/carbon nano-tube composite electromagnetic screen paper and preparation method thereof
CN111748255A (en) * 2020-06-30 2020-10-09 陕西科技大学 Photo-thermal insulation type composite leather finishing agent based on Pickering emulsion polymerization method and preparation method thereof

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CN108276577A (en) * 2018-02-02 2018-07-13 天津工业大学 Poly-dopamine modified lithium carbon nanotube graphene/polyimide composite material and preparation method thereof
CN108951282A (en) * 2018-06-12 2018-12-07 中国电子科技集团公司第三十三研究所 A kind of graphene/carbon nano-tube composite electromagnetic screen paper and preparation method thereof
CN111748255A (en) * 2020-06-30 2020-10-09 陕西科技大学 Photo-thermal insulation type composite leather finishing agent based on Pickering emulsion polymerization method and preparation method thereof

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114479242A (en) * 2022-01-28 2022-05-13 泰州泽钰新材料科技有限公司 Conductive bio-based plastic and preparation method and application thereof

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