CN115353740B - Polysiloxane material with electromagnetic shielding function and preparation method thereof - Google Patents
Polysiloxane material with electromagnetic shielding function and preparation method thereof Download PDFInfo
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- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L83/00—Compositions of macromolecular compounds obtained by reactions forming in the main chain of the macromolecule a linkage containing silicon with or without sulfur, nitrogen, oxygen or carbon only; Compositions of derivatives of such polymers
- C08L83/04—Polysiloxanes
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- H—ELECTRICITY
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- H05K9/00—Screening of apparatus or components against electric or magnetic fields
- H05K9/0073—Shielding materials
- H05K9/0081—Electromagnetic shielding materials, e.g. EMI, RFI shielding
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K3/00—Use of inorganic substances as compounding ingredients
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- C08K2003/0806—Silver
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K3/00—Use of inorganic substances as compounding ingredients
- C08K3/02—Elements
- C08K3/08—Metals
- C08K2003/085—Copper
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K2201/00—Specific properties of additives
- C08K2201/001—Conductive additives
Abstract
The application relates to the field of electromagnetic shielding materials, and particularly discloses a polysiloxane material with an electromagnetic shielding function and a preparation method thereof. The polysiloxane material with the electromagnetic shielding function comprises a component A and a component B, wherein the mass ratio of the component A to the component B is (3-8): the component A comprises polysiloxane prepolymer, conductive filler I, dispersant I, solvent I and auxiliary agent, and the component B comprises polyurethane curing agent, wave-absorbing filler, conductive filler II, dispersant II and solvent II. The preparation method comprises the following steps: preparing raw materials according to a proportion, stirring and mixing the raw materials of the component A to obtain the raw material A, stirring and mixing the raw materials of the component B to obtain the component B, blending the component A and the component B according to the proportion, and stirring to obtain the polysiloxane material with the electromagnetic shielding function. The application has the effect of keeping the high-efficiency electromagnetic shielding performance and simultaneously enabling the electromagnetic shielding material to meet the development trend of miniaturization and portability of electronic medical equipment.
Description
Technical Field
The application relates to the field of electromagnetic shielding materials, in particular to a polysiloxane material with an electromagnetic shielding function and a preparation method thereof.
Background
With the rapid development of technology, advanced digital electronic devices and analog circuits are combined to provide medical functions, and the combination has become a major trend of medical devices. Electromagnetic interference has a great influence on electronic medical equipment, and relates to diagnosis of doctors and personal safety of patients. Thus, electromagnetic compatibility is an essential property of electronic medical devices.
In order to improve electromagnetic compatibility of medical equipment, means such as grounding, shielding, filtering and the like are generally adopted. The shielding is to make the conductive and magnetic conductive material into a shielding body so that electromagnetic radiation is controlled inside the medical equipment, thereby reducing the influence of electromagnetic interference. The conductive paint is the most commonly used electromagnetic shielding material and has the advantages of low cost, simplicity, practicability, wide application range and the like.
As electronic medical equipment is developed toward miniaturization, high sensitivity and portability, the requirements for electromagnetic shielding material performance are increasingly increasing. However, how to make the electromagnetic shielding material meet the development trend of miniaturization and portability of electronic medical equipment while maintaining the high-efficiency electromagnetic shielding performance is a problem to be solved in the current medical field.
Disclosure of Invention
In order to ensure that the electromagnetic shielding material meets the development trend of miniaturization and portability of electronic medical equipment while maintaining the high-efficiency electromagnetic shielding performance, the application provides a polysiloxane material with an electromagnetic shielding function and a preparation method thereof.
In a first aspect, the present application provides a polysiloxane material with electromagnetic shielding function, which adopts the following technical scheme:
a polysiloxane material with electromagnetic shielding function, which comprises a component A and a component B, wherein the mass ratio of the component A to the component B is (3-8): 1, wherein the component A comprises the following raw materials in percentage by mass:
50 to 70 percent of polysiloxane prepolymer
Conductive filler 1 2-10%
1 to 5 percent of dispersant
Solvent one 0-10%
11.5% -25% of auxiliary agent;
the component B comprises the following raw materials in percentage by mass:
40 to 70 percent of polyurethane curing agent
1 to 10 percent of wave-absorbing filler
Conductive filler II 1-10%
Dispersant II 5-15%
10% -25% of solvent II.
By adopting the technical scheme, in the component A, the polysiloxane prepolymer is used as a film forming substance, the polysiloxane prepolymer takes O-Si-O as a main body structure, the conductivity of the polysiloxane prepolymer is superior to that of the conventional high polymer resin, the electromagnetic shielding effect of the material is improved, and the coating can be endowed with better heat resistance and mechanical impact resistance; the addition of the first dispersing agent improves the dispersibility of the first conductive filler in the polysiloxane prepolymer network structure, improves the agglomeration phenomenon, and improves the electromagnetic shielding performance of the material while enhancing the conductivity;
in the component B, the wave-absorbing filler can absorb incident electromagnetic waves, so that the electromagnetic shielding performance of the material is improved, the conductive filler is beneficial to further improving the conductivity of the material, and meanwhile, the electromagnetic shielding effect is improved; the addition of the second dispersing agent enables the wave-absorbing filler and the second conductive filler to be fully mixed and mutually permeated, and under the interaction of the wave-absorbing filler and the second conductive filler, the conductivity and the electromagnetic shielding performance of the material are obviously improved;
when the component A and the component B are mixed, the material is solidified under the action of a polyurethane solidifying agent, and the mixture of the component A and the component B is sprayed on the surface of medical equipment, so that a coating with better electromagnetic shielding performance can be obtained; experiments show that the electromagnetic shielding effectiveness of the polysiloxane material with the electromagnetic shielding function can reach 46-48dB by spraying the polysiloxane material with the electromagnetic shielding function on the substrate, and the development trend of miniaturization and portability of electronic medical equipment is met while the high-efficiency electromagnetic shielding performance is maintained.
Alternatively, the polysiloxane prepolymers are prepared from raw materials comprising nanosilica sol, alkoxysilane and silane capping agent.
By adopting the technical scheme, the polysiloxane prepolymer prepared from the nano silica sol, the alkoxy silane and the silane end capping agent has film forming property, not only has conductivity superior to common film forming organic matters, but also can improve the curing property of the material, so that the obtained coating can be cured at normal temperature after the component A and the component B are mixed, and the polysiloxane material with the electromagnetic shielding function can be conveniently sprayed on the surface of medical equipment.
Optionally, the first conductive filler is metal powder.
By adopting the technical scheme, the metal powder has good conductivity, and the powdery filler is convenient to disperse in the system, so that electromagnetic shielding effect and conductivity are provided for the polysiloxane material.
Optionally, the first conductive filler is silver-coated copper powder.
By adopting the technical scheme, the silver-coated copper powder has excellent conductivity, the cost is far lower than that of silver powder, the property is stable, the silver-coated copper powder is not easy to oxidize, the silver-coated copper powder is convenient to disperse in a system, and the silver-coated copper powder can provide better electromagnetic shielding performance for polysiloxane materials.
Optionally, the wave-absorbing filler is selected from one of nickel-plated graphite, nickel-plated expanded graphite, nickel-plated graphene nanoplatelets, nickel-plated carbon fibers, nickel-plated carbon nanofibers, nickel-plated single-walled carbon nanotubes and nickel-plated multi-walled carbon nanotubes.
By adopting the technical scheme, the nickel-plated carbon filler is used as the wave-absorbing filler, has good conductivity and magnetic conductivity, and can interact with the second conductive filler in the system, so that the electromagnetic shielding performance of the material is improved.
Optionally, the wave-absorbing filler is nickel-plated graphene.
Through adopting above-mentioned technical scheme, graphite alkene has advantages such as absorption frequency channel is wide, the compatibility is good, light in weight, thickness are little, and nickel can improve the absorption capacity of graphite alkene to electromagnetic wave by a wide margin, and when the experiment found that selects nickel plating graphite alkene as the wave absorbing filler, the electromagnetic shielding performance of material is best.
Optionally, the nickel content of the wave-absorbing filler is not less than 30%.
By adopting the technical scheme, the improvement of the nickel content is beneficial to the improvement of the conductivity of the wave-absorbing filler, so that the electromagnetic shielding effect of the material is improved.
Optionally, the second conductive filler is one selected from graphite, expanded graphite, graphene nanoplatelets, single-walled carbon nanotubes, multi-walled carbon nanotubes, carbon nanofibers, and carbon fibers.
By adopting the technical scheme, the carbon-based filler is used as the second conductive filler, so that the electrical conductivity, the thermal conductivity and the shielding effectiveness of the material can be obviously improved, and the second conductive filler and the wave-absorbing filler in the system are mutually penetrated, so that the electromagnetic shielding performance of the material is further improved.
Optionally, the second conductive filler is a multiwall carbon nanotube.
By adopting the technical scheme, the multi-wall carbon nano tube has simple structure and stable chemical property, a small amount of multi-wall carbon nano tubes have good conductivity, and a line contact type and surface contact type conductive network can be formed, so that the whole mechanical property and conductivity of the material are greatly improved, and experiments show that the electromagnetic shielding performance of the material is optimal when the multi-wall carbon nano tube is selected as the second conductive filler.
In a second aspect, the present application provides a method for preparing a polysiloxane material with electromagnetic shielding function, which adopts the following technical scheme:
a method for preparing a polysiloxane material with electromagnetic shielding function, which comprises the following steps:
s1, preparing raw materials according to a proportion, adding a conductive filler I, a dispersant I, a pigment, a solvent I and an auxiliary agent into a polysiloxane prepolymer, and stirring and mixing to obtain a component A;
s2, adding a solvent II, a dispersant II, a wave-absorbing filler and a conductive filler II into the polyurethane curing agent, and stirring and mixing to obtain a component B;
s3, blending the component A and the component B according to the proportion, and stirring to obtain the polysiloxane material with the electromagnetic shielding function.
Through adopting above-mentioned technical scheme, make component A and component B mix through the mode of blending, obtain the electromagnetic shielding coating of single-layer structure, be convenient for medical instrument realizes the lightweight, when keeping high-efficient electromagnetic shielding performance, satisfies the miniaturized, portable development trend of electron medical equipment.
In summary, the present application includes at least one of the following beneficial technical effects:
1. in the component A, polysiloxane prepolymer is used as a film forming substance, which is beneficial to improving the electromagnetic shielding effect, heat resistance and mechanical impact resistance of the material; the first dispersing agent improves the dispersibility of the first conductive filler, improves the agglomeration phenomenon, and improves the electromagnetic shielding performance of the material while enhancing the conductivity; in the component B, the wave-absorbing filler can absorb incident electromagnetic waves, the conductive filler II is beneficial to further improving the conductivity of the material, and meanwhile, the electromagnetic shielding effect is improved, and the dispersing agent II enables the wave-absorbing filler and the conductive filler II to be fully mixed and mutually permeated, so that the conductivity and the electromagnetic shielding performance of the material are obviously improved; when the component A and the component B are mixed, the material is cured under the action of the polyurethane curing agent, so that a coating with good electromagnetic shielding performance can be obtained, and the development trend of miniaturization and portability of electronic medical equipment is met while the high-efficiency electromagnetic shielding performance is maintained;
2. the polysiloxane prepolymer prepared from the nano silicon dioxide sol, the alkoxy silane and the silane end capping agent has film forming property, not only has conductivity superior to common film forming organic matters, but also can improve the solidifying performance of the material, so that the obtained coating can be solidified at normal temperature after the component A and the component B are mixed, and the polysiloxane material with electromagnetic shielding function can be conveniently sprayed on the surface of medical equipment;
3. the component A and the component B are mixed in a blending mode, so that the electromagnetic shielding coating with a single-layer structure is obtained, the medical instrument is convenient to realize light weight, and the development trend of miniaturization and portability of the electronic medical equipment is met while the high-efficiency electromagnetic shielding performance is maintained.
Detailed Description
Raw material source
The raw material specifications in the following examples and comparative examples are shown in table 1 below unless otherwise specified.
TABLE 1 raw material specification
| Raw materials | Specification of specification |
| Nano silicon dioxide sol | Average particle diameter of 30nm |
| Dispersant I | Digadispers 755W |
| Copper powder | Average particle diameter of 10 μm |
| Silver coated copper powder | Average grain diameter of 10-20 μm, silver content of more than or equal to 30% |
| Pigment | Carbon black color paste |
| Defoaming agent | Digao Tego 901W |
| Thickening agent | RongaHasi Le Shun RM-8W |
| Polyurethane curing agent | Kesi wound Bayhydur XP2655 |
| Dispersing agent II | Digaospers 752W |
| Nickel plated multiwall carbon nanotubes | The pipe diameter is 10-30nm and the length is 10-30 mu m |
| Nickel-plated graphene | The average sheet diameter is 5 mu m, and the nickel content is more than or equal to 30 percent |
| Graphene | Average sheet diameter 5 μm |
| Single-wall carbonNanotube | Pipe diameter 20nm and length 20 μm |
| Multiwall carbon nanotubes | The pipe diameter is 10-30nm and the length is 10-30 mu m |
Performance test
Sample preparation
The materials with electromagnetic shielding function prepared in examples and comparative examples were taken as test objects, sprayed and coated on the surface of 304 stainless steel plate having a size of 50cm×50cm×1cm to prepare samples, two samples were prepared for each material with electromagnetic shielding function, one sample coating had a dry film thickness of 15 μm and the other sample coating had a dry film thickness of 25 μm.
Detection method
Test 1: VOC content test
The test method comprises the following steps: the materials with electromagnetic shielding function prepared in examples and comparative examples were taken as test objects, and the VOC content of the paint was tested according to GB/T18582-2020.
Test 2: shielding effectiveness test (before aging)
The test method comprises the following steps: each sample was tested for shielding effectiveness in the frequency band of 2GHz-18GHz according to GJB 6190-2008.
Test 3: hardness test
The test method comprises the following steps: each specimen coating was tested for hardness according to GB/T6739-2006.
Test 4: dry adhesion test
The test method comprises the following steps: each test specimen coating was tested for adhesion according to GB/T9286-2021.
Test 5: shielding effectiveness test (after aging)
The test method comprises the following steps: according to GB/T16259-2008, the wavelength range is 290-800 nm, irradiance is 550W/m 2 As light source, each sample was subjected to 1000h of artificial accelerated aging, followed by GJB 6190-2008, each aged sample was tested for shielding effectiveness in the frequency band of 2GHz-18 GHz.
Examples
Example 1
A polysiloxane material with electromagnetic shielding function, which is prepared by the following steps:
q1, weighing 1kg of nano silica sol, 1kg of methyltrimethoxysilane (alkoxy silane) and 500g of tetramethyl disiloxane (silane end capping agent), mixing the alkoxy silane and the silane end capping agent, controlling the temperature at 45 ℃, controlling the stirring speed at 30rpm, adding the nano silica sol into the obtained mixture, and reacting for 2 hours to obtain polysiloxane prepolymer;
q2, weighing 2kg of polysiloxane prepolymer, 200g of dispersing agent I, 400g of silver-coated copper powder (average particle size 10 mu m, silver content 30%), 800g of pigment, 80g of defoamer, 120g of thickener and 400g of deionized water (solvent I), controlling the stirring speed at 300rpm, adding the dispersing agent I, the silver-coated copper powder and the pigment into the polysiloxane prepolymer, stirring for 30min, performing ultrasonic vibration for 2min, sequentially adding the defoamer, the thickener and the deionized water, and stirring for 30min to obtain a component A;
q3, weighing 600g of polyurethane curing agent, 375g of propylene glycol diacetate (solvent II), 225g of dispersant II, 150g of nickel-plated graphene (nickel content is 30%) and 150g of graphene, controlling the stirring speed at 500rpm, adding the solvent II into the polyurethane curing agent for dilution, sequentially adding the dispersant II, the nickel-plated graphene and the graphene, stirring for 30min, and performing ultrasonic vibration for 5min to obtain a component B;
q4, weighing 3kg of the component A and 1kg of the component B, blending the component A and the component B, controlling the stirring speed at 300rpm, and stirring for 10min to obtain the polysiloxane material with the electromagnetic shielding function.
Examples 2 to 3
Examples 2-3 differ from example 1 in the type, quality and specification of component a starting materials, see in particular table 2 below.
TABLE 2 kinds, quality and Specifications of component A raw materials in examples 2-3
| Examples | Example 2 | Example 3 |
| Types of alkoxysilanes | Tetraethoxysilane | Phenyl trimethoxysilane |
| Kinds of silane-terminated agents | Trimethylmethoxysilane | Tetramethyl disiloxane |
| Quality of polysiloxane prepolymer | 2.8kg | 2.6kg |
| Mass of dispersant one | 40g | 160g |
| Quality of silver-coated copper powder | 80g | 320g |
| Specification of silver-coated copper powder | Average particle diameter 15 μm and silver content 30% | Average particle diameter 20 μm and silver content 30% |
| PigmentQuality of (2) | 740g | 400g |
| Quality of defoamer | 20g | 60g |
| Mass of thickener | 40g | 60g |
| Mass of solvent one | 280g | 400g |
Examples 4 to 5
Examples 4-5 differ from example 1 in the mass of the component B starting materials, in particular in Table 3 below.
TABLE 3 mass of component B starting materials in examples 4-5
| Examples | Example 4 | Example 5 |
| Quality of polyurethane curing agent | 975g | 1.05kg |
| Mass of solvent two | 150g | 225g |
| Mass of dispersant II | 150g | 75g |
| Quality of nickel-plated graphene | 75g | 15g |
| Quality of graphene | 150g | 135g |
The results of the performance measurements of examples 1-5 and their samples (dry film thickness 25 μm) are shown in Table 4 below.
TABLE 4 results of Performance measurements of examples 1-5 and samples thereof (dry film thickness 25 μm)
| Examples | Example 1 | Example 2 | Example 3 | Example 4 | Example 5 |
| VOC content | ≤20g/L | ≤20g/L | ≤20g/L | ≤20g/L | ≤20g/L |
| Shielding effectiveness (before aging) | 61dB | 55dB | 60dB | 59dB | 57dB |
| Hardness of | 4H | 4H | 4H | 4H | 4H |
| Dry adhesion | Level 0 | Level 0 | Level 0 | Level 0 | Level 0 |
| Shielding effectiveness (after aging) | 59dB | 52dB | 57dB | 57dB | 55dB |
Examples 6 to 7
Examples 6-7 differ from example 5 in the quality of nickel plated graphene and graphene in component B, see in particular table 5 below.
TABLE 5 mass of component B starting materials in examples 6-7
| Examples | Example 6 | Example 7 |
| Quality of nickel-plated graphene | 135g | 75g |
| Quality of graphene | 15g | 75g |
The results of the performance measurements of examples 5-7 and their samples (dry film thickness 25 μm) are shown in Table 6 below.
TABLE 6 results of Performance measurements of examples 5-7 and samples thereof (dry film thickness 25 μm)
| Examples | Example 5 | Example 6 | Example 7 |
| VOC content | ≤20g/L | ≤20g/L | ≤20g/L |
| Shielding effectiveness (before aging) | 57dB | 57dB | 59dB |
| Hardness of | 4H | 4H | 4H |
| Dry adhesion | Level 0 | Level 0 | Level 0 |
| Shielding effectiveness (after aging) | 55dB | 54dB | 56dB |
Examples 8 to 9
Examples 8-9 differ from example 1 in that the component A and component B weighed in the Q4 step are different in mass, see in particular Table 7 below.
TABLE 7 mass of component A and mass of component B in examples 8-9
| Examples | Example 8 | Example 9 |
| Mass of component A | 3.5kg | 3.6kg |
| Mass of component B | 0.7kg | 0.45kg |
The results of performance measurements of examples 1, 8, 9 and their samples (dry film thickness 25 μm) are shown in Table 8 below.
TABLE 8 results of Performance measurements of examples 1, 8, 9 and samples thereof (dry film thickness 25 μm)
| Examples | Example 1 | Example 8 | Example 9 |
| VOC content | ≤20g/L | ≤20g/L | ≤20g/L |
| Shielding effectiveness (before aging) | 61dB | 62dB | 61dB |
| Hardness of | 4H | 4H | 4H |
| Dry adhesion | Level 0 | Level 0 | Level 0 |
| Shielding effectiveness (after aging) | 59dB | 60dB | 58dB |
Examples 10 to 16
Examples 10-16 differ from example 8 in the type of electrically conductive filler one, wave-absorbing filler and electrically conductive filler two selected, as specified in Table 9 below.
Table 9 categories of conductive filler I, wave-absorbing filler and conductive filler II in examples 10 to 16
| Examples | Conductive filler I | Wave-absorbing filler | Conductive filler II |
| Example 10 | Silver coated copper powder | Nickel plated multiwall carbon nanotubes | Graphene |
| Example 11 | Silver coated copper powder | Nickel plated multiwall carbon nanotubes | Single-walled carbon nanotubes |
| Example 12 | Silver coated copper powder | Nickel plated multiwall carbon nanotubes | Multiwall carbon nanotubes |
| Example 13 | Silver coated copper powder | Nickel-plated graphene | Multiwall carbon nanotubes |
| Example 14 | Silver coated copper powder | Nickel-plated graphene | Single-walled carbon nanotubes |
| Example 15 | Copper powder | Nickel-plated graphene | Graphene |
| Example 16 | Copper powder | Nickel-plated graphene | Multiwall carbon nanotubes |
The results of the performance measurements of examples 8, 10-16 and their samples (dry film thickness 25 μm) are shown in Table 10 below.
TABLE 10 results of Performance measurements of examples 8, 10-16 and samples thereof (dry film thickness 25 μm)
| Examples | VOC content | Shielding effectiveness (before aging) | Hardness of | Dry adhesion | Shielding effectiveness (after aging) |
| Example 8 | ≤20g/L | 62dB | 4H | Level 0 | 60dB |
| Example 10 | ≤20g/L | 63dB | 4H | Level 0 | 60dB |
| Example 11 | ≤20g/L | 61dB | 4H | Level 0 | 59dB |
| Example 12 | ≤20g/L | 61dB | 4H | Level 0 | 59dB |
| Example 13 | ≤20g/L | 65dB | 4H | Level 0 | 63dB |
| Example 14 | ≤20g/L | 63dB | 4H | Level 0 | 61dB |
| Example 15 | ≤20g/L | 57dB | 4H | Level 0 | 54dB |
| Example 16 | ≤20g/L | 59dB | 4H | Level 0 | 57dB |
As can be seen from the combination of examples 8 and 10-16 and the combination of table 10, when silver-coated copper powder is selected as the conductive filler, the shielding effectiveness of the material is significantly better than when copper powder is selected as the first conductive filler, when nickel-plated graphene is selected as the second conductive filler, the shielding effectiveness of the material is better than other combinations, and when silver-coated copper powder is selected as the first conductive filler, nickel-plated graphene is selected as the first conductive filler, and when multi-walled carbon nanotube is selected as the second conductive filler, the shielding effectiveness of the material is optimal.
Comparative example
Comparative examples 1 to 2
Comparative examples 1 to 2 differ from example 1 in that the mass of component A and the mass of component B weighed in the Q4 step are different, specifically as shown in Table 11 below.
TABLE 11 mass of component A and mass of component B in comparative examples 1-2
| Comparative example | Comparative example 1 | Comparative example 2 |
| Mass of component A | 2kg | 3kg |
| Mass of component B | 1kg | 300g |
The results of the performance tests of examples 1, 8, 9 and comparative examples 1-2 and their test pieces (dry film thickness 25 μm) are shown in Table 12 below.
TABLE 12 results of Performance measurements of examples 1, 8, 9 and comparative examples 1-2 and their samples (dry film thickness 25 μm)
| Example 1 | Example 8 | Example 9 | Comparative example 1 | Comparative example 2 | |
| VOC content | ≤20g/L | ≤20g/L | ≤20g/L | ≤20g/L | ≤20g/L |
| Shielding effectiveness (before aging) | 61dB | 62dB | 61dB | 58dB | 52dB |
| Hardness of | 4H | 4H | 4H | 3H | 2H |
| Dry adhesion | Level 0 | Level 0 | Level 0 | Level 0 | Level 2 |
| Shielding effectiveness (after aging) | 59dB | 60dB | 58dB | 55dB | 49dB |
It can be seen from a combination of examples 1, 8, 9 and comparative examples 1 to 2 and a combination of Table 12 that when the mass ratio of component A and component B is in the range of (3-8): 1, the shielding effectiveness of the polysiloxane material having an electromagnetic shielding function is significantly improved, and when the mass ratio of component A and component B is in the range of 5:1, the shielding effectiveness of the material is optimal.
Comparative example 3
Comparative example 3 differs from example 1 in that in component a, a thermosetting acrylic resin (average molecular weight 15000) of the same quality was selected instead of the polysiloxane prepolymer.
Comparative example 4
Comparative example 4 differs from example 1 in that in component A, bisphenol A type epoxy resin (trade name E51) of the same quality was selected instead of the polysiloxane prepolymer.
The results of the performance tests of example 1 and comparative examples 3 to 4 and their samples (dry film thickness 15 μm, 25 μm) are shown in Table 13 below.
TABLE 13 results of Performance measurements of example 1 and comparative examples 3-4 and their samples (dry film thickness 15 μm, 25 μm)
| VOC content | Shielding effectiveness (before aging) | Hardness of | Dry adhesion | Shielding effectiveness (after aging) | |
| Example 1 (25 μm) | ≤20g/L | 61dB | 4H | Level 0 | 59dB |
| Comparative example 3 (25 μm) | ≤30g/L | 50dB | 3H | Level 0 | 45dB |
| Comparative example 4 (25 μm) | ≤30g/L | 51dB | 3H | Level 0 | 45dB |
| Example 1 (15 μm) | ≤20g/L | 48dB | 3H | Level 0 | 46dB |
| Comparative example 3 (15 μm) | ≤30g/L | 30dB | 2H | Level 2 | 25dB |
| Comparative example 4 (15 μm) | ≤30g/L | 28dB | 2H | Level 2 | 22dB |
As can be seen from the combination of example 1 and comparative examples 3-4, and table 13, the hardness, shielding effectiveness and aging resistance of the material were significantly reduced after the film forming polysiloxane prepolymer in component a was replaced with other resins; as can be seen from the test results of the samples with the dry film thickness of 15 μm and the dry film thickness of 25 μm, when the thickness of the coating is reduced, the polysiloxane material with the electromagnetic shielding function still has higher shielding effectiveness, hardness, adhesive force and aging resistance, can meet the use requirements of medical equipment, accords with the development trend of miniaturization and portability, and the materials in comparative examples 1 and 2 have the problem that the shielding effectiveness, the hardness and the adhesive force are greatly reduced after the thickness of the coating is reduced, so that the use requirements cannot be met.
Comparative example 5
Comparative example 5 differs from example 1 in that a wave-absorbing filler was added to component a, i.e., steps Q2 and Q3, as follows:
q2, weighing 2kg of polysiloxane prepolymer, 200g of dispersing agent I, 400g of silver-coated copper powder (average particle size 10 mu m, silver content 30%), 133.3g of nickel-plated graphene (nickel content 30%), 800g of pigment, 80g of defoaming agent, 120g of thickening agent and 400g of deionized water (solvent I), controlling the stirring speed at 300rpm, adding the dispersing agent I, the silver-coated copper powder, the nickel-plated graphene and the pigment into the polysiloxane prepolymer, stirring for 30min, performing ultrasonic vibration for 2min, sequentially adding the defoaming agent, the thickening agent and the deionized water, and stirring for 30min to obtain a component A;
q3, weighing 600g of polyurethane curing agent, 375g of propylene glycol diacetate (solvent II), 225g of dispersant II and 150g of graphene, controlling the stirring speed at 500rpm, adding the solvent II into the polyurethane curing agent for dilution, sequentially adding the dispersant II and the graphene, stirring for 30min, and performing ultrasonic vibration for 5min to obtain the component B.
Comparative example 6
Comparative example 6 differs from example 1 in that in component a, the same mass of graphene was selected as the conductive filler one, and in component B, the same mass of silver-coated copper powder was selected as the conductive filler two.
Comparative example 7
Comparative example 7 differs from example 1 in that in component a, the same mass of graphene was selected as the first conductive filler instead of silver-coated copper powder, in component B, the same mass of silver-coated copper powder was selected as the second conductive filler instead of graphene, and a wave-absorbing filler was added to component a, i.e., steps Q2 and Q3, as follows:
q2, weighing 2kg of polysiloxane prepolymer, 200g of dispersant I, 400g of graphene, 133.3g of nickel-plated graphene (nickel content is 30%), 800g of pigment, 80g of defoamer, 120g of thickener and 400g of deionized water (solvent I), controlling the stirring speed at 300rpm, adding the dispersant I, the graphene, the nickel-plated graphene and the pigment into the polysiloxane prepolymer, stirring for 30min, performing ultrasonic vibration for 2min, sequentially adding the defoamer, the thickener and the deionized water, and stirring for 30min to obtain a component A;
q3, weighing 600g of polyurethane curing agent, 375g of propylene glycol diacetate (solvent II), 225g of dispersing agent II and 150g of silver-coated copper powder (average particle size 10 mu m and silver content 30%), controlling the stirring speed at 500rpm, adding the solvent II into the polyurethane curing agent for dilution, sequentially adding the dispersing agent II and the silver-coated copper powder, stirring for 30min, and performing ultrasonic vibration for 5min to obtain the component B.
The results of the performance tests of example 1 and comparative examples 5 to 7 and their test pieces (dry film thickness 25 μm) are shown in Table 14 below.
TABLE 14 results of Performance measurements of example 1 and comparative examples 5-7 and their samples (dry film thickness 25 μm)
| Example 1 | Comparative example 5 | Comparative example 6 | Comparative example 7 | |
| VOC content | ≤20g/L | ≤20g/L | ≤20g/L | ≤20g/L |
| Shielding effectiveness (before aging) | 61dB | 54dB | 50dB | 56dB |
| Hardness of | 4H | 4H | 4H | 4H |
| Dry adhesion | Level 0 | Level 0 | Level 0 | Level 0 |
| Shielding effectiveness (after aging) | 59dB | 50dB | 47dB | 51dB |
As can be seen from the combination of example 1 and comparative examples 5 to 7 and the combination of table 14, in comparative example 5, since the wave-absorbing filler was added to the component a, the wave-absorbing filler and the conductive filler were not sufficiently mixed and penetrated each other, resulting in a significant decrease in shielding effectiveness; in comparative example 6, graphene is selected as the first conductive filler, silver-coated copper powder is selected as the second conductive filler, the dispersion effect of the graphene in the polysiloxane prepolymer network structure is inferior to that of the silver-coated copper powder, and the interpenetration effect of the silver-coated copper powder and the wave-absorbing filler is poor, so that the shielding effectiveness of the material is further reduced; in comparative example 7, nickel-plated graphene and graphene are added to component a, silver-coated copper powder is added to component B, and the shielding effectiveness is still significantly lower than that of example 1, which indicates that the dispersion effect of the metal powder in the polysiloxane prepolymer network structure has the effect of improving the shielding effectiveness of the material.
The above embodiments are not intended to limit the scope of the present application, so: all equivalent changes in structure, shape and principle of the application should be covered in the scope of protection of the application.
Claims (5)
1. A polysiloxane material with electromagnetic shielding function, characterized in that: comprises a component A and a component B, wherein the mass ratio of the component A to the component B is (3-8): 1, wherein the component A comprises the following raw materials in percentage by mass:
50 to 70 percent of polysiloxane prepolymer
Conductive filler 1 2-10%
1 to 5 percent of dispersant
Solvent one 0-10%
Pigment 10-20%
1.5% -5% of an auxiliary agent;
the component B comprises the following raw materials in percentage by mass:
40 to 70 percent of polyurethane curing agent
1 to 10 percent of wave-absorbing filler
Conductive filler II 1-10%
Dispersant II 5-15%
10% -25% of a second solvent;
the polysiloxane prepolymer is prepared from raw materials comprising nano silicon dioxide sol, alkoxy silane and silane end capping agent, the first conductive filler is metal powder, the wave-absorbing filler is selected from one of nickel-plated graphite, nickel-plated expanded graphite, nickel-plated graphene nano sheets, nickel-plated carbon fibers, nickel-plated carbon nano fibers, nickel-plated single-wall carbon nano tubes and nickel-plated multi-wall carbon nano tubes, and the second conductive filler is selected from one of graphite, expanded graphite, graphene nano sheets, single-wall carbon nano tubes, multi-wall carbon nano tubes, carbon nano fibers and carbon fibers;
the preparation method of the polysiloxane material with the electromagnetic shielding function comprises the following steps:
s1, preparing raw materials according to a proportion, adding a conductive filler I, a dispersant I, a pigment, a solvent I and an auxiliary agent into a polysiloxane prepolymer, and stirring and mixing to obtain a component A;
s2, adding a solvent II, a dispersant II, a wave-absorbing filler and a conductive filler II into the polyurethane curing agent, and stirring and mixing to obtain a component B;
s3, blending the component A and the component B according to the proportion, and stirring to obtain the polysiloxane material with the electromagnetic shielding function.
2. A polysiloxane material with electromagnetic shielding function according to claim 1, wherein: the first conductive filler is silver-coated copper powder.
3. A polysiloxane material with electromagnetic shielding function according to claim 1, wherein: the wave-absorbing filler is nickel-plated graphene.
4. A polysiloxane material with electromagnetic shielding function according to claim 1, wherein: the nickel content of the wave-absorbing filler is not less than 30%.
5. A polysiloxane material with electromagnetic shielding function according to claim 1, wherein: the second conductive filler is a multi-wall carbon nano tube.
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