CN109401466B - Nano coating for inhibiting charge accumulation on epoxy resin surface and preparation method thereof - Google Patents
Nano coating for inhibiting charge accumulation on epoxy resin surface and preparation method thereof Download PDFInfo
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- CN109401466B CN109401466B CN201811178377.0A CN201811178377A CN109401466B CN 109401466 B CN109401466 B CN 109401466B CN 201811178377 A CN201811178377 A CN 201811178377A CN 109401466 B CN109401466 B CN 109401466B
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- 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
- C09D129/00—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 an alcohol, ether, aldehydo, ketonic, acetal, or ketal radical; Coating compositions based on hydrolysed polymers of esters of unsaturated alcohols with saturated carboxylic acids; Coating compositions based on derivatives of such polymers
- C09D129/02—Homopolymers or copolymers of unsaturated alcohols
- C09D129/04—Polyvinyl alcohol; Partially hydrolysed homopolymers or copolymers of esters of unsaturated alcohols with saturated carboxylic acids
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J7/00—Chemical treatment or coating of shaped articles made of macromolecular substances
- C08J7/04—Coating
- C08J7/0427—Coating with only one layer of a composition containing a polymer binder
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- 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
- C09D7/40—Additives
- C09D7/60—Additives non-macromolecular
- C09D7/61—Additives non-macromolecular inorganic
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- 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
- C09D7/40—Additives
- C09D7/70—Additives characterised by shape, e.g. fibres, flakes or microspheres
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2363/00—Characterised by the use of epoxy resins; Derivatives of epoxy resins
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- Chemical & Material Sciences (AREA)
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- Life Sciences & Earth Sciences (AREA)
- Engineering & Computer Science (AREA)
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- Wood Science & Technology (AREA)
- Health & Medical Sciences (AREA)
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Abstract
The invention discloses a nano coating for inhibiting charge accumulation on the surface of epoxy resin and a preparation method thereof, wherein the preparation method comprises the following steps: weighing MMT, and dispersing the MMT in deionized water to form a suspension with the mass concentration of 1 wt%; s2, adding PVA and deionized water into the suspension prepared in the step S1 to enable the mass of the PVA to be 40wt% -60wt% of the total solid mass of the PVA and the MMT and the total solid mass fraction in the solution to be 1wt% -2 wt%; s3, adding a cross-linking agent GA after the PVA is completely dissolved, and performing ultrasonic treatment for 15-30min at constant temperature to form a PVA/MMT dispersion system; s4, treating the epoxy resin insulator in the plasma for 4-8 minutes; s5, vertically immersing the epoxy resin insulator into a PVA/MMT dispersion system of the impregnation liquid to form a PVA/MMT two-dimensional nano coating, wherein the coating has a special nano-scale layered structure, so that the surface trap level of the epoxy resin insulator can be reduced from about 1.02eV to about 0.86eV, and carriers can be dispersed along the surfaces of the organosilicate crystal sheet layers which are arranged in parallel; the surface charge accumulation of the insulator can be reduced, and the direct-current flashover voltage is improved by about 20%.
Description
Technical Field
The invention relates to the technical field of insulation, in particular to a nano coating for inhibiting charge accumulation on the surface of epoxy resin and a preparation method thereof.
Background
The problem of accumulation of surface charges of the insulator under direct current voltage is a cause of reduction of flashover voltage along the surface of the insulator, so the problem of accumulation of the charges needs to be solved. Currently, there are two main methods proposed by researchers for modifying materials to inhibit surface charge accumulation, one is surface fluorination treatment and the other is plasma treatment.
The surface fluorination treatment is to utilize the strong oxidizing property of fluorine gas to carry out direct fluorination reaction on the surface of an insulating material to form a firm carbon-fluorine (C-F) surface layer organically combined with a matrix, and the physical and chemical structures of the surface of the material are changed to improve the surface conductivity of the insulator and achieve the purposes of promoting charge dissipation and inhibiting charge accumulation. Its significant drawbacks are three: firstly, fluorine gas and fluorine are highly toxic gases, can stimulate eyes, skin and respiratory mucosa, need special protection facilities in industrial production and application, need special protection for storage, transportation and the like of fluorine gas, and increase the cost; fluorine gas reacts with the insulator (epoxy resin material) and also reacts with metal to corrode the metal, so that the fluorine gas inevitably reacts with the flange and the insert of the insulator to corrode the flange and the insert in the treatment process; thirdly, the chemical components of the surface of the insulator are changed by the chemical treatment method, the aging of the surface of the insulator is accelerated, and the long-term stability of the insulator is still examined.
The plasma treatment is in a dielectric barrier discharge form or an atmospheric pressure plasma jet form, the surface of the insulating material is modified by low-temperature plasma, the physical appearance (roughness) is mainly changed, and other gases can be added to participate in chemical reaction to form a coating. Its disadvantages are two: one is that no matter what type of discharge, a special electrode structure is required. For example, DBD discharge, positive and negative electrodes can only be flat plates, insulators are placed between them, and the insulators to be treated can only be flat plates; such as APPJ, the discharge is jet-like and can only handle very small areas. And secondly, uniform discharge and uniform treatment are difficult to achieve no matter what discharge form is adopted. Therefore, this concept cannot meet the requirements of large-scale industrial applications at all.
An effective solution to the problems in the related art has not been proposed yet.
Disclosure of Invention
Aiming at the technical problems in the related art, the invention provides a nano coating for inhibiting the accumulation of the surface charges of the epoxy resin and a preparation method thereof, which can solve the technical problems.
In order to achieve the technical purpose, the technical scheme of the invention is realized as follows:
a preparation method of a nano coating dipping solution comprises the following steps:
s1, weighing MMT, dispersing the MMT in deionized water to form suspension with the mass concentration of 1wt%, then stirring at a high speed for 5-10min, and carrying out ultrasonic treatment for 15-30 min;
s2, adding PVA and deionized water into the suspension prepared in the step S1 to enable the mass of the PVA to be 40wt% -60wt% of the total mass of the PVA and the MMT, enabling the mass fraction of the total solid in the solution to be 1wt% -2wt%, placing the mixture in a water bath, heating to 90 ℃ while stirring, and performing ultrasonic dispersion again for 15-30 min;
s3, adding a cross-linking agent GA after PVA is completely dissolved, enabling the ratio of the mole number of GA to the total mole number of hydroxyl groups on a PVA chain to be 1:20, adding a catalyst HCl for cross-linking reaction, enabling the ratio of the mole number of the catalyst HCl to the mole number of GA to be 1:5, and carrying out ultrasonic treatment for 15-30min at constant temperature to form a uniform and transparent nano coating dipping solution PVA/MMT dispersion system.
Further, PVA and deionized water were added to the suspension prepared in step S1 in step S2 so that the mass of PVA was 50wt% of the total solid mass of PVA and MMT.
The nano coating impregnating solution is prepared according to the preparation method of the nano coating impregnating solution.
The application of the nano coating impregnating solution in inhibiting the charge accumulation on the surface of the epoxy resin.
The method for preparing the nano coating by using the nano coating dipping solution comprises the following steps:
s1, processing the epoxy resin insulator in the plasma for 4-8 minutes to remove surface impurities and improve the hydrophilicity of the surface of the substrate;
s2, vertically immersing the epoxy resin insulator into the impregnation liquid PVA/MMT dispersion system, keeping the impregnation liquid PVA/MMT dispersion system for 60-120S, taking out the epoxy resin insulator, vertically placing the epoxy resin insulator in a thermostat at 60 ℃ for 1-2 h, and forming a laminated PVA/MMT two-dimensional nano coating with high orientation;
and S3, after the surface coating of the insulator is dried, turning the dipping direction of the epoxy resin insulator up and down, repeating the dipping process of the step S2 for a plurality of times, and obtaining the nano coating which has uniform coating thickness and inhibits the accumulation of the surface charges of the epoxy resin.
Further, the epoxy resin insulator coated with the nano coating layer has a surface trap level of 0.86eV in step S3.
Further, the coating thickness obtained in step S3 is 200-100 nm.
The nano coating is prepared by the method for preparing the nano coating by using the nano coating impregnation liquid.
The invention has the beneficial effects that: the PVA/MMT dispersion system solution is adopted to dip the insulators to form the two-dimensional nano coating, the operation is simple and convenient, the efficiency is high, the PVA/MMT dispersion system solution is prepared once, a plurality of insulators can be dipped, the coating has a special nano-scale layered structure, the surface trap level of the epoxy resin insulator can be reduced from about 1.02eV to about 0.86eV, the evacuation of carriers along the surfaces of the organosilicate crystal sheet layers which are arranged in parallel is facilitated, and the tangential migration of the carriers is easy; the surface charge accumulation of the insulator can be reduced, and the direct-current flashover voltage is improved by about 20%.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without creative efforts.
FIG. 1 is an XRD spectrum of the PVA/MMT coating and related materials of example 4;
FIG. 2 is a TEM image of the PVA/MMT coating in example 4;
FIG. 3 is an SEM image of the PVA/MMT coating in example 4;
FIG. 4 is a surface electron trap level distribution diagram of the epoxy resin material coated with the PVA/MMT nano-coating in example 4;
FIG. 5 is a distribution diagram of the surface hole trap energy level of the epoxy resin material coated with the PVA/MMT nano-coating in example 4;
FIG. 6 is a Weibull distribution plot for example 4;
fig. 7 is a flow chart of a process for preparing a nano-coating by using a nano-coating dipping solution according to an embodiment of the invention.
Detailed Description
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 that can be derived by one of ordinary skill in the art from the embodiments given herein are intended to be within the scope of the present invention.
Raw materials: montmorillonite (MMT), also known as montmorillonite and microcrystalline kaolinite, is a natural silicate clay ore with a two-dimensional layered structure, the silicate sheet layer of which is a crystal structure formed by silicon-oxygen tetrahedron and aluminum hydroxyl octahedron in a ratio of 2:1, the silicate sheet layer of MMT is formed under the combined action of van der waals force, hydrogen bond and dipole moment, the length and width of a single sheet layer can reach hundreds of nanometers, and the thickness is only 1 nm. The MMT used in the described embodiments of the invention is supplied by BYK Additives, USA.
Polyvinyl alcohol (PVA) is a water-soluble resin having excellent chemical stability, thermal stability, electrical insulation, adhesiveness, light transmittance, mechanical properties and the like, and the average molecular weight of the PVA 67000 used in the examples described in the present invention is provided by Kuraray corporation of japan.
Catalyst for the crosslinking reaction HCl, 37% by weight, HCl used in the examples described herein, was supplied by Sigma-Aldrich, USA.
Glutaraldehyde (GA), 50% by weight, supplied by Sigma-Aldrich, USA;
example 1:
a preparation method of a nano coating dipping solution comprises the following steps:
s1, weighing MMT10g, dispersing in 990g of deionized water to form a suspension with the mass concentration of 1wt%, then stirring at a high speed for 5min, and carrying out ultrasonic treatment for 15 min;
s2, adding 6.67g of PVA and deionized water into the suspension prepared in the step S1 to enable the mass of the PVA to be 40wt% of the total solid mass of the PVA and the MMT and the mass fraction of the total solid in the solution to be 1wt%, placing the mixture in a water bath, heating to 90 ℃ while stirring, and performing ultrasonic dispersion again for 15 min;
s3, after the PVA is completely dissolved, 0.76g of cross-linking agent GA is added, the ratio of the mole number of GA to the mole total number of hydroxyl groups on the PVA chain is 1:20, 0.06g of cross-linking reaction catalyst HCI is added, the ratio of the mole number of HCl catalyst to the mole number of GA is 1:5, and the mixture is subjected to ultrasonic treatment for 15min at constant temperature to form a uniform and transparent nano coating impregnation liquid PVA/MMT dispersion system.
Example 2:
s1, weighing MMT10g, dispersing in 990g of deionized water to form a suspension with the mass concentration of 1wt%, then stirring at a high speed for 8min, and carrying out ultrasonic treatment for 20 min;
s2, adding 10g of PVA and deionized water into the suspension prepared in the step S1 to enable the mass of the PVA to account for 50wt% of the total solid mass of the PVA and the MMT and the mass fraction of the total solid in the solution to be 1wt%, placing the mixture in a water bath, heating to 90 ℃ while stirring, and performing ultrasonic dispersion again for 20 min;
s3, after the PVA is completely dissolved, 1.14g of cross-linking agent GA is added, the ratio of the mole number of GA to the mole total number of hydroxyl groups on the PVA chain is 1:20, 0.06g of cross-linking reaction catalyst HCI is added, the ratio of the mole number of catalyst HCl to the mole number of GA is 1:5, and ultrasonic treatment is carried out for 20min at constant temperature, so that a uniform and transparent nano-coating impregnation liquid PVA/MMT dispersion system is formed.
Example 3:
s1, weighing MMT10g, dispersing in 990g of deionized water to form a suspension with the mass concentration of 1wt%, then stirring at a high speed for 10min, and carrying out ultrasonic treatment for 30 min;
s2, adding 12g of PVA and deionized water into the suspension prepared in the step S1 to enable the mass of the PVA to be 60wt% of the total solid mass of the PVA and the MMT and the mass fraction of the total solid in the solution to be 2wt%, placing the mixture in a water bath, heating to 90 ℃ while stirring, and performing ultrasonic dispersion again for 30 min;
s3, after the PVA is completely dissolved, 1.368g of cross-linking agent GA is added, the ratio of the mole number of GA to the mole total number of hydroxyl groups on the PVA chain is 1:20, 0.06g of cross-linking reaction catalyst HCI is added, the ratio of the mole number of HCl catalyst to the mole number of GA is 1:5, and ultrasonic treatment is carried out for 30min at constant temperature, so that a uniform and transparent nano-coating impregnation liquid PVA/MMT dispersion system is formed.
Example 4:
as shown in fig. 7, the method for preparing a nano coating using the nano coating dipping solution prepared in example 2 includes the following steps:
s1, processing the epoxy resin insulator in the plasma for 4 minutes to remove surface impurities and improve the hydrophilicity of the surface of the substrate;
s2, vertically immersing the epoxy resin insulator into the impregnation liquid PVA/MMT dispersion system, keeping the impregnation liquid PVA/MMT dispersion system for 60S, taking out the epoxy resin insulator, vertically placing the epoxy resin insulator in a thermostat at 60 ℃ for 1 h, and forming a laminated PVA/MMT two-dimensional nano coating with high orientation;
and S3, after the surface coating of the insulator is dried, turning the dipping direction of the epoxy resin insulator up and down, repeating the dipping process of the step S2 for a plurality of times to control the thickness of the coating and ensure the uniformity of the thickness of the coating, and obtaining the nano coating which has uniform thickness and inhibits the accumulation of the charges on the surface of the epoxy resin.
Example 5:
the method for preparing the nano coating by using the nano coating impregnation liquid prepared in the embodiment 2 comprises the following steps:
s1, processing the epoxy resin insulator in the plasma for 8 minutes to remove surface impurities and improve the hydrophilicity of the surface of the substrate;
s2, vertically immersing the epoxy resin insulator into the impregnation liquid PVA/MMT dispersion system, keeping the impregnation liquid PVA/MMT dispersion system for 120S, taking out the epoxy resin insulator, vertically placing the epoxy resin insulator in a thermostat at 60 ℃ for 2h, and forming a laminated PVA/MMT two-dimensional nano coating with high orientation;
and S3, after the surface coating of the insulator is dried, turning the dipping direction of the epoxy resin insulator up and down, repeating the dipping process of the step S2 for a plurality of times to control the thickness of the coating and ensure the uniformity of the thickness of the coating, and obtaining the nano coating which has uniform thickness and inhibits the accumulation of the charges on the surface of the epoxy resin.
In examples 4 and 5, the epoxy resin insulator was treated in plasma in step S1, and the plasma treatment system was used under the condition that the flow rate was 20cm3Min, air pressure 150mtor, power 300W. In step S2, after the constant temperature treatment, under the action of gravity, the MMT sheetThe lamellar structure can form arrangement in the same direction along with the flow direction of liquid in a solution, and is self-assembled with PVA molecular chains under the action of a cross-linking agent to form a two-dimensional nano coating with high orientation.
As shown in FIG. 1, the XRD patterns of the PVA/MMT coating and related materials in example 4 are shown, wherein 1 corresponds to the XRD pattern of the PVA sample, 2 corresponds to the XRD pattern of the MMT sample, 3 corresponds to the XRD pattern of the pure PVA/MMT film, 4 corresponds to the XRD pattern of the epoxy resin with the PVA/MMT coating, and 5 corresponds to the XRD pattern of the epoxy resin without the PVA/MMT coating. As can be seen from the figure, the (001) plane diffraction peak of the pure MMT sample is around 7.81 °, and the corresponding interplanar distance is calculated from the Bragg equation to be ds =1.1 nm, which is substantially consistent with the crystal structure of MMT. The diffraction peak of a pure PVA/MMT film (obtained by taking a silicon wafer as a substrate to prepare a coating and peeling the coating from the silicon wafer) is shifted to 3.24 degrees, the corresponding interplanar distance is changed to ds =2.7 nm, namely, the distance between MMT layers is increased, and the PVA molecules enter the MMT layer structure. Similarly, the diffraction peak of the epoxy resin material coated with the PVA/MMT nano coating is near 2.94 degrees, the corresponding distance between crystal planes is ds =2.9 nm, the diffraction peak is narrow, and no impurity peak exists, which indicates that a relatively regular PVA/MMT layered structure is formed on the surface of the epoxy resin. Since the thickness of the single-layer MMT is about 1nm, the thickness of the PVA layer between the MMT layers is about 2 nm.
In order to visually observe the microstructure of the PVA/MMT, the cross section of the PVA/MMT coating is shot by adopting SEM and TEM, and the result is shown in figures 2-3, wherein the structure of the PVA/MMT coating on the substrate is very regular, the MMT monolithic layer structure is fully stripped and arranged along the consistent direction, the MMT monolithic layer structure has extremely high orientation, the overall thickness of the PVA/MMT coating can be controlled between 200 and 1000 nm according to different dipping times, and the thickness of the PVA/MMT coating produced by single dipping is about 200 nm.
The trap level of the PVA/MMT nano-coating layer obtains the distribution of the trap level on the surface of the epoxy resin material coated with the PVA/MMT nano-coating layer by using an isothermal current attenuation method, and as a result, as shown in fig. 4-5, fig. 4 is an electron trap level distribution diagram, in which a is the epoxy resin coated with the PVA/MMT nano-coating layer, b is the epoxy resin without the coating layer, fig. 5 is a hole trap level distribution diagram, in which c is the epoxy resin coated with the PVA/MMT nano-coating layer, and d is the epoxy resin without the coating layer. As can be seen from the figure, after the PVA/MMT two-dimensional nano coating is coated, the electron trap and the hole trap of the surface layer of the epoxy resin material are changed from about 1.02eV to about 0.86 eV. The shallow trap energy level is mainly related to the two-dimensional layered structure which is tightly arranged in the coating, and the special structure is helpful for the evacuation of carriers along the surfaces of the organosilicate crystal sheet layers which are arranged in parallel, so that the transfer of the carriers in the tangential direction is easy. In the normal direction, due to the barrier effect of hundreds of layers of dense organic/inorganic repeating structures, the migration of carriers in the normal direction is effectively blocked, so that the conductance in the normal direction is not increased.
Analysis of the charge dispersion effect of the PVA/MMT two-dimensional nano coating: in order to observe the charge dispersion effect of the PVA/MMT coating, the dissipation phenomenon of the surface charge of the PVA/MMT coating is studied by adopting a Kelvin Probe Force Microscope (KPFM) mode of AFM. KPFM is a method of recording the surface potential of a sample in which the Kelvin probe used works on a principle similar to that of an active electrostatic probe. Before the experiment, the sample is adhered to a metal tray special for AFM by conductive silver adhesive, and the tray is grounded. The specific steps of the experiment are as follows:
1) first, the surface topography of the sample was scanned with an AFM probe, which was used as a reference for KPFM probe movement. And then recording the initial potential distribution of the surface of the sample by using a KPFM mode, wherein the scanned area is a rectangle of 2 mu m multiplied by 0.5 mu m.
2) Then, an AFM probe was contacted to the surface of the sample, a direct current voltage was applied thereto, and scanning was performed in a contact mode in a region of 100nm × 25nm at the center for injecting charges to the surface of the sample.
3) Then, the sample is converted into a KPFM mode again, and the surface potential of the sample is scanned. The appearance of the sample is not changed in the charge injection process in the step 2, but the potential of the central area of the sample is obviously changed, namely the initial surface potential distribution of the sample after the charge is injected.
4) And (3) continuously scanning the surface potential of the sample in a KPFM mode, and recording the process of the surface potential of the sample changing along with time, wherein the time interval between two adjacent frames is about 20 s.
The experimental result is analyzed, so that the surface charge of the sample which is not coated with the nano coating dissipates very slowly, and a large amount of charges are accumulated on the surface of the sample after 332 s; the sample coated with the nano coating has the evidence that the surface charge is quickly dissipated and diffused to the surroundings, which shows that the coating has a remarkable effect of dispersing the charge. In particular, the spatial scale of the experiment is only hundreds of nanometers, and the unique properties of the microstructure of the PVA/MMT coating are reflected.
Surface charge accumulation of PVA/MMT coated insulator: in order to investigate the actual effect of the PVA/MMT coating, a two-dimensional nano coating is coated on one half of the surface of the epoxy resin insulator, and the other half of the surface of the epoxy resin insulator is kept unchanged. Applying a voltage of-20 kV in the air of 0.1 MPa, measuring the surface potential distribution after 30min, and calculating the corresponding surface charge distribution, wherein the result shows that the accumulation of 'charge spots' is obvious and the charge density is larger in the area which is not coated with the two-dimensional nano coating; and the number and density of the 'charge spots' in the area coated with the two-dimensional nano coating are obviously reduced, and the charge is uniformly distributed integrally, so that the coating has the effects of promoting surface charge evacuation and reducing the density of the 'charge spots' on the insulator which is actually applied under direct voltage.
A pair of finger pressure electrodes are adopted to test the surface flashover voltage of the test sample, the electrode spacing is 3mm, the test is carried out for 45 times respectively, the flashover voltage value of each time is recorded, a Weibull distribution diagram is drawn, as shown in figure 6, wherein the flashover voltage value at the position with the probability of 63.2% is taken as the characteristic flashover voltage. The flashover voltage of the uncoated epoxy resin is 5.7kV, the flashover voltage of the coated epoxy resin is 7.1kV, and the flashover voltage is increased by about 20%.
In summary, according to the technical scheme of the invention, the insulators are impregnated by adopting the PVA/MMT dispersion solution to form the two-dimensional nano coating, the operation is simple and convenient, the efficiency is high, the PVA/MMT dispersion solution is prepared once, a plurality of insulators can be impregnated, the coating has a special nano-scale layered structure, the surface trap level of the epoxy resin insulator can be reduced from about 1.02eV to about 0.86eV, the dispersion of carriers along the surfaces of the organosilicate crystal sheet layers arranged in parallel is facilitated, and the tangential migration of the carriers is facilitated; the surface charge accumulation of the insulator can be reduced, and the direct-current flashover voltage is improved by about 20%.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.
Claims (8)
1. A preparation method of a nano coating impregnating solution is characterized by comprising the following steps:
s1, weighing MMT, dispersing the MMT in deionized water to form suspension with the mass concentration of 1wt%, then stirring at a high speed for 5-10min, and carrying out ultrasonic treatment for 15-30 min;
s2, adding PVA and deionized water into the suspension prepared in the step S1 to enable the mass of the PVA to be 40wt% -60wt% of the total mass of the PVA and the MMT, enabling the mass fraction of the total solid in the solution to be 1wt% -2wt%, placing the mixture in a water bath, heating to 90 ℃ while stirring, and performing ultrasonic dispersion again for 15-30 min;
s3, adding a cross-linking agent GA after PVA is completely dissolved, enabling the ratio of the mole number of GA to the total mole number of hydroxyl groups on a PVA chain to be 1:20, adding a catalyst HCl for cross-linking reaction, enabling the ratio of the mole number of the catalyst HCl to the mole number of GA to be 1:5, and carrying out ultrasonic treatment for 15-30min at constant temperature to form a uniform and transparent nano coating dipping solution PVA/MMT dispersion system.
2. The method of claim 1, wherein step S2 is performed by adding PVA and deionized water into the suspension prepared in step S1, so that the mass of PVA is 50wt% of the total solid mass of PVA and MMT.
3. A nanocoating dip prepared according to the method of any one of claims 1-2.
4. Use of a nanocoating dip according to claim 3 for inhibiting the accumulation of charge on the epoxy surface.
5. The method for preparing the nano coating by using the nano coating impregnating solution of claim 3, which is characterized by comprising the following steps:
s1, processing the epoxy resin insulator in the plasma for 4-8 minutes to remove surface impurities and improve the hydrophilicity of the surface of the substrate;
s2, vertically immersing the epoxy resin insulator into the impregnation liquid PVA/MMT dispersion system, keeping the impregnation liquid PVA/MMT dispersion system for 60-120S, taking out the epoxy resin insulator, vertically placing the epoxy resin insulator in a thermostat at 60 ℃ for 1-2 h, and forming a laminated PVA/MMT two-dimensional nano coating with high orientation;
and S3, after the surface coating of the insulator is dried, turning the epoxy resin insulator up and down along the dipping direction, repeating the dipping process of the step S2 for a plurality of times, and obtaining the nano coating which has uniform coating thickness and inhibits the accumulation of the surface charges of the epoxy resin.
6. The method of claim 5, wherein the epoxy insulator coated with the nano-coating at step S3 has a surface trap level of 0.86 eV.
7. The method as claimed in claim 5, wherein the thickness of the coating obtained in step S3 is 200 nm and 100 nm.
8. A nanocoating prepared according to any one of claims 5-7.
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