CN111518454A

CN111518454A - Composition and method for preparing C-band electromagnetic functional coating

Info

Publication number: CN111518454A
Application number: CN202010470461.0A
Authority: CN
Inventors: 于海涛; 孙新; 张久霖; 杨智慧; 张连平
Original assignee: Beijing Institute of Environmental Features
Current assignee: Beijing Institute of Environmental Features
Priority date: 2020-05-28
Filing date: 2020-05-28
Publication date: 2020-08-11

Abstract

The invention relates to a composition and a method for preparing a C-band electromagnetic functional coating. The composition comprises (a) an absorbent; (B) a resin matrix component comprising a liquid carboxyl-terminated nitrile rubber having a molecular weight of 8000-15000 and a bisphenol A type epoxy resin having an epoxy equivalent of 180-220; the mass ratio of the liquid carboxyl nitrile rubber to the bisphenol A epoxy resin is (10-20): 100. The invention adopts the epoxy resin with the epoxy equivalent of 180-150220 and the liquid carboxyl-terminated butadiene-acrylonitrile rubber with the molecular weight of 8000-15000 as the resin matrix components, the epoxy resin with the epoxy equivalent can meet the requirements of a bonding absorbent and other additives, the liquid carboxyl-terminated butadiene-acrylonitrile rubber with the specific molecular weight can participate in the crosslinking reaction of the resin matrix, the flexibility of the resin matrix can be improved, and the prepared electromagnetic functional coating has good mechanical property.

Description

Composition and method for preparing C-band electromagnetic functional coating

Technical Field

The invention relates to the technical field of preparation of electromagnetic functional coatings, in particular to a composition and a method for preparing a C-band electromagnetic functional coating.

Background

The rapid development of electronic communication technology brings convenience to the life of people and causes great electromagnetic pollution, thereby causing various diseases endangering the health of human bodies. The electromagnetic functional coating is composed of an absorbent and a resin matrix material, can reduce or eliminate electromagnetic radiation pollution to a certain extent, and is being widely developed and applied. In order to meet the requirement of high electromagnetic wave absorption performance, a large amount of absorbent needs to be filled in the resin matrix, which causes the phenomena of high rigidity, easy brittle fracture and shedding, short service life and the like of the electromagnetic functional coating. How to take into account the electromagnetic wave absorption performance and the mechanical properties of the coating, including flexibility, adhesive force, impact strength and the like of the coating, meets the requirements of the use environment, and becomes a key problem which is difficult to solve.

Disclosure of Invention

The traditional electromagnetic functional coating has the defects of poor electromagnetic functional performance, easy falling caused by overhigh rigidity, short service life and the like, and cannot meet the use requirement, so that the development of a novel electromagnetic functional coating which has both electromagnetic wave absorption performance and excellent mechanical performance is urgently needed, and the use performance of a target can be improved.

In order to achieve the purpose, the invention provides the following technical scheme:

a composition for producing a C-band electromagnetically functional coating, the composition comprising:

(A) an absorbent;

(B) a resin matrix component comprising a liquid carboxyl-terminated nitrile rubber having a molecular weight of between 8000-15000 and a bisphenol A type epoxy resin having an epoxy equivalent of between 180-220; the mass ratio of the liquid carboxyl nitrile rubber to the bisphenol A epoxy resin is (10-20): 100.

Preferably, the absorbent is a sheet-shaped ferromagnetic absorbent, the thickness is 100-500nm, and the diameter is 3-10 μm;

preferably, the mass ratio of the absorbent to the resin matrix component is (10-20): (90-80).

Preferably, the composition further comprises one or more of the following additives:

a first diluent, preferably a mixture of ethyl acetate, n-butanol and ethanol in a mass ratio of (1-3) to (1-3), most preferably a mixture of ethyl acetate, n-butanol and ethanol in a mass ratio of 2:1: 1;

a coupling agent, preferably a silane coupling agent;

an anti-aging agent;

an anti-settling agent; and/or

And (4) defoaming agent.

Preferably, the mass ratio of the first diluent to the absorbent is (2-3) to 1;

the mass ratio of the coupling agent to the absorbent is (5-10) 1000;

the mass ratio of the anti-aging agent to the absorbent is (1-5) to 1000;

the mass ratio of the anti-settling agent to the absorbent is (1-5) to 1000; and/or

The mass ratio of the defoaming agent to the absorbent is (1-5) to 1000.

Preferably, the composition further comprises:

a curing agent, which can be triethylene tetramine; preferably, the mass ratio of the curing agent to the resin matrix component is preferably (0.5-1): 100; and

a second diluent, preferably a mixture of ethyl acetate, n-butanol and ethanol in a mass ratio of (1-3) to (1-3), most preferably a mixture of ethyl acetate, n-butanol and ethanol in a mass ratio of 2:1: 1; preferably, the second diluent is used in an amount such that the viscosity of the composition is from 20 to 25 s.

A method for preparing a C-band electromagnetic functional coating using the composition, the method comprising the steps of:

(1) a step of preparing the resin matrix component to obtain a modified resin;

(2) preparing the modified resin and the absorbent to obtain the electromagnetic functional coating;

(3) and forming the electromagnetic functional coating into an electromagnetic functional coating.

Preferably, the step (1) includes the steps of:

stirring the liquid carboxyl-terminated nitrile-butadiene rubber and the bisphenol A epoxy resin at the stirring speed of preferably 100-200r/min to obtain the modified resin.

Preferably, the step (2) includes the steps of:

(21) mixing an absorbent with an additive, preferably, mixing the absorbent with a first diluent and a coupling agent, then adding an anti-aging agent, an anti-settling agent and a defoaming agent, mixing, and finally adding the modified resin for mixing;

(22) and (4) grinding the mixture obtained in the step (21) to obtain the electromagnetic functional coating.

Preferably, the step (3) includes the steps of:

and mixing the electromagnetic functional coating with a curing agent and a second diluent, wherein the viscosity of the mixture is preferably 20-25s, and then spraying and curing to obtain the electromagnetic functional coating.

Preferably, the spraying pressure of the spraying is 0.3-0.5MPa, and the spraying interval is not less than 20 min;

the curing temperature is 60-70 ℃, and the curing time is 2-4 h; and/or

The thickness of the electromagnetic function coating is 1-3mm, more preferably 1-1.5mm, and more preferably 1-1.1 mm.

Advantageous effects

The technical scheme of the invention has the following advantages:

the composition provided by the invention adopts the epoxy resin with the epoxy equivalent of 180-220 and the liquid carboxyl-terminated butadiene-acrylonitrile rubber (CTBN) with the molecular weight of 8000-15000 as resin matrix components, the epoxy resin with the epoxy equivalent can meet the requirements of an adhesive absorbent and other auxiliaries, the liquid carboxyl-terminated butadiene-acrylonitrile rubber with the specific molecular weight can participate in the crosslinking reaction of the resin matrix, the flexibility of the resin matrix can be improved, and the prepared electromagnetic functional coating has good mechanical properties.

The invention preferably adopts a sheet-shaped ferromagnetic absorbent with the thickness of 100-500nm and the diameter of 3-10 mu m as the absorbent, the absorbent has high magnetic conductivity imaginary part in the C wave band, low dielectric constant and good electromagnetic function performance, the reflectivity of the prepared electromagnetic function coating in the C wave band is lower than-10 dB, and the reflectivity of the prepared electromagnetic function coating in some specific frequency points can be lower than-20 dB.

The electromagnetic functional coating prepared by the invention has electromagnetic wave absorption performance and excellent mechanical property, can improve the use performance of a target, and has wide application prospect.

Drawings

FIG. 1 is a flowchart of the method of example 1;

FIG. 2 is an external view of a coating made according to the present invention;

FIG. 3 is a reflectance graph of the coating made in example 1;

FIG. 4 is a graph of the reflectance of the coating made in example 2;

FIG. 5 is a graph of the reflectance of the coating made in example 3;

FIG. 6 is a graph of the reflectance of the coating made in example 4;

FIG. 7 is a graph of the reflectance of the coating made in example 5;

FIG. 8 is a graph of the reflectance of the coating made in example 8.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. It is to be understood that the embodiments described are only a few embodiments of the present invention, and not all embodiments. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.

First aspect

The present invention provides in a first aspect a composition for the preparation of a C-band electromagnetically functional coating, the composition comprising:

(A) an absorbent;

(B) a resin matrix component comprising a liquid carboxyl-terminated nitrile rubber having a molecular weight of 8000-15000 and a bisphenol A type epoxy resin having an epoxy equivalent of 180-220; the mass ratio of the liquid carboxyl nitrile rubber to the bisphenol A epoxy resin is (10-20): 100.

Composition comprising a metal oxide and a metal oxide

As for the amount of the epoxy resin and the liquid carboxyl-terminated nitrile rubber, the mass ratio of the liquid carboxyl-terminated nitrile rubber to the bisphenol A type epoxy resin is defined to be (10-20):100, and for example, may be 10:100, 15:100, 20: 100. When the using amount of the liquid carboxyl-terminated butadiene-acrylonitrile rubber is too high, the adhesion force of the coating is poor; when the amount of the liquid carboxyl-terminated nitrile rubber is too low, the coating has poor flexibility.

Absorbent agent

In some preferred embodiments, the absorbent is a sheet-shaped ferromagnetic absorbent, the thickness of the absorbent is 100-500nm, the diameter of the absorbent is 3-10 μm, the imaginary part of the magnetic permeability of the absorbent in the C band is high, the dielectric constant is low, and the electromagnetic functional coating has good electromagnetic functional performance, the reflectivity of the prepared electromagnetic functional coating in the C band is lower than-10 dB, and the reflectivity of the electromagnetic functional coating in some specific frequency points can be lower than-20 dB.

As for the amount of the absorbent used, the present invention preferably controls the mass ratio of the absorbent to the resin matrix component to be (10-20) to (90-80). When the dosage of the absorbent is too much, the rigidity of the electromagnetic functional coating is too high, the electromagnetic functional coating is easy to break and fall off, and the service life is short; when the dosage of the absorbent is too small, the electromagnetic functional coating has better mechanical property, but the electromagnetic property is poorer. The inventor finds that the coating prepared by combining the absorbent and the resin matrix component according to the mass ratio of (10-20) to (90-80) can simultaneously achieve the electromagnetic wave absorption performance of the coating and the mechanical property of the coating.

Additive agent

The composition may further comprise one or more of the following additives:

for example, the composition provided by the invention can comprise a first diluent, the first diluent is preferably a mixture of ethyl acetate, n-butanol and ethanol according to the mass ratio of (1-3) to (1-3), most preferably a mixture of ethyl acetate, n-butanol and ethanol according to the mass ratio of 2:1:1, and the coating sprayed by adding the specific diluent is flat and smooth and has high volatilization speed. The mass ratio of the first diluent to the absorbent is preferably (2-3):1, and may be, for example, 2:1, 2.5:1, 3: 1.

For example, the compositions provided herein may include a coupling agent, preferably a silane coupling agent, KH-560 (gamma-glycidoxypropyltrimethoxysilane). The mass ratio of coupling agent to absorbent is preferably (5-10):1000, and may be, for example, 5:1000, 6:1000, 7:1000, 8:1000, 9:1000, 10: 1000. The coupling agent can coat and modify the surface of the absorbent, reduce the dielectric constant of the absorbent and facilitate the combination of the coupling agent and the epoxy resin, so that the wave-absorbing coating has good absorption performance and mechanical property.

For example, the composition provided by the present invention may contain an anti-aging agent, which is commonly used in the art, and the present invention is not limited herein. The mass ratio of the antioxidant to the absorbent is preferably (1-5):1000, and may be, for example, 1:1000, 2:1000, 3:1000, 4:1000, 5:1000, and most preferably 1.5: 1000.

For example, the composition provided by the present invention may contain an anti-settling agent, and the anti-settling agent may be an anti-aging agent commonly used in the art, which is not listed herein. The mass ratio of the anti-settling agent to the absorbent is preferably (1-5):1000, and may be, for example, 1:1000, 2:1000, 3:1000, 4:1000, 5:1000, and most preferably 1: 1000.

For example, the composition provided by the invention may contain a defoaming agent, and the defoaming agent may be an antioxidant commonly used in the art, which is not listed herein. The mass ratio of the defoaming agent to the absorbent is preferably (1-5):1000, and may be, for example, 1:1000, 2:1000, 3:1000, 4:1000, 5:1000, and most preferably 2: 1000.

Curing agent

The curing agent is preferably triethylene tetramine, and the mass ratio of the curing agent to the resin matrix component is preferably (0.5-1):100, and may be, for example, 0.5:100, 0.6:100, 0.7:100, 0.8:100, 0.9:100, 1: 100.

A second diluent

The second diluent is preferably a mixture of ethyl acetate, n-butanol and ethanol in a mass ratio of (1-3) to (1-3) and most preferably a mixture of ethyl acetate, n-butanol and ethanol in a mass ratio of 2:1: 1.

In some preferred embodiments, the second diluent is used in an amount such that the viscosity of the composition is from 20 to 25s (paint viscosity is measured in 4 cups of paint, as measured by the time the paint runs off). The viscosity is too high, the spraying and discharging are difficult, the wire drawing phenomenon is easy to occur, and the adhesive force of the electromagnetic functional coating is reduced; the viscosity is too low, and the solvent of the electromagnetic functional coating is difficult to volatilize, so that the flexibility of the electromagnetic functional coating is poor.

The second aspect

The invention provides in a second aspect a method for preparing a C-band electromagnetic functional coating using a composition provided in the first aspect, the method comprising the steps of:

(1) a step of preparing the resin matrix component to obtain a modified resin;

In the step (1), the liquid carboxyl-terminated nitrile rubber and the bisphenol A epoxy resin are preferably stirred, the stirring speed is preferably 100-200r/min, and the stirring time is preferably 5-10min, so as to obtain the modified resin.

Step (2), wherein the step (2) comprises the following steps:

(21) mixing the absorbent with the additive (for example, mixing is achieved by a stirring method), preferably, mixing the absorbent with the first diluent and the coupling agent (for example, mixing is achieved by a stirring method, the stirring rotation speed is preferably 400-;

(22) and (4) grinding the mixture obtained in the step (21) to obtain the electromagnetic functional coating. The grinding is preferably carried out by a three-roller grinding machine, and the grinding effect is achieved by mutual extrusion of the surfaces of the three horizontal rollers and friction at different speeds, so that the materials of all components are better fused, and the uniformity of the coating is improved. The grinding rotation speed is preferably 200-300r/min, and the grinding time is preferably 50-60 min.

And (3) the step (3) comprises the following steps:

mixing the electromagnetic functional coating with a curing agent and a second diluent (for example, mixing is achieved by a stirring method, the stirring speed is preferably 100-. The spraying process affects the appearance quality of the coating, and in order to ensure the appearance quality of the coating, the spraying needs to be carried out under appropriate parameters: in some preferred embodiments, the spraying pressure of the spraying is 0.3-0.5MPa, for example, 0.3MPa, 0.4MPa, 0.5MPa, the spraying interval is not less than 20min, and the caliber of the spray gun is phi 1.5 mm. In some preferred embodiments, the curing temperature is 60 ℃ to 70 ℃, for example, 60 ℃, 65 ℃, 70 ℃ and the curing time is 2 to 4 hours, for example, 2 hours, 3 hours, 4 hours. In some preferred embodiments, the thickness of the electromagnetic functional coating is 1 to 3mm, more preferably 1 to 1.5mm, and still more preferably 1 to 1.1 mm.

The method provided by the invention has one or more of the following advantages:

the electromagnetic functional coating prepared by the method provided by the invention has both electromagnetic wave absorption performance and excellent mechanical property, can improve the use performance of a target, and has wide application prospect.

The method provided by the invention can uniformly distribute the absorbent in the resin matrix to form a coating with a uniform structure.

The preparation method provided by the invention has the advantages that by adjusting the spraying process parameters and the viscosity of the coating, the performance stability is ensured, the appearance quality of the coating is improved, and the universality is higher.

The preparation method provided by the invention is convenient for realizing engineering production.

The following are examples of the present invention.

Example 1

Referring to fig. 1, the preparation method provided in this embodiment includes the following steps:

(1) mixing and stirring liquid carboxyl-terminated butadiene-acrylonitrile rubber (CTBN) with the molecular weight of 8000-15000 and bisphenol A epoxy resin with the epoxy equivalent of 180-220 according to the mass ratio of 10:100, wherein the stirring speed is 100r/min, and the stirring time is 5min, so as to obtain the modified epoxy resin.

(2) Mixing and stirring an absorbent, a coupling agent KH560 and a diluent according to a mass ratio of 1000:5:2000, wherein the stirring speed is 400r/min, and the stirring time is 20min, wherein the absorbent is a sheet-shaped ferromagnetic absorbent, the thickness is 100-500nm, the diameter is 3-10 mu m, and the diluent is ethyl acetate, n-butyl alcohol and ethanol in a ratio of 2:1: 1.

(3) And (3) mixing and stirring the anti-aging agent, the anti-settling agent and the defoaming agent with the mixture obtained in the step (2) at a stirring speed of 400r/min for 5min, wherein the using amounts of the anti-aging agent, the anti-settling agent and the defoaming agent meet the following condition that the mass ratio of the absorbent to the anti-aging agent to the anti-settling agent to the defoaming agent is 1000:1.5:1: 2.

(4) Mixing and stirring the modified epoxy resin and the mixture obtained in the step (3), wherein the stirring speed is 400r/min, and the stirring time is 5 min; the dosage of the modified epoxy resin meets the following condition that the mass ratio of the modified epoxy resin to the absorbent is 20: 80.

(5) And (4) grinding the mixture obtained in the step (4) on a three-roll grinder, wherein the rotating speed of a discharge grinding roll of the three-roll grinder is 200r/min, and the grinding time is 50min, so that the electromagnetic functional coating is obtained.

(6) Weighing a curing agent triethylene tetramine, adding the curing agent triethylene tetramine into the electromagnetic functional coating, wherein the mass ratio of the triethylene tetramine to the modified epoxy resin is 0.5:100, then adding a diluent, wherein the diluent is a mixture composed of ethyl acetate, n-butyl alcohol and ethanol according to a ratio of 2:1:1, adjusting the viscosity of the electromagnetic functional coating to be 20s, mixing and stirring, and stirring at a rotation speed of 100r/min for 2 min.

(7) And (3) forming a coating on the mixture obtained in the step (6) by using a spraying process, adjusting spraying process parameters, setting the caliber of a spray gun to be phi 1.5mm, the spraying pressure to be 0.3-0.5MPa, and the spraying interval to be not less than 20min, curing after the spraying is finished, wherein the curing condition is that the temperature is 70 ℃, the time is 4 hours, and the final coating thickness is 1.04mm, so that the requirements of the electromagnetic function and the mechanical property of the target C waveband can be met.

Fig. 2 is an appearance diagram of the coating layer obtained, and it can be seen from fig. 2 that the appearance quality of the coating layer is good. The obtained product has excellent reflectivity which is lower than-10 dB and reaches-22 dB at 6GHz within the frequency band of 4GHz-8GHz as shown in figure 3.

The mechanical properties of the electromagnetic functional coating are shown in table 1.

TABLE 1

Serial number	Item	Measured value
			1	Adhesion (MPa)	5.12
2	Impact Strength (kg. cm)	41
			3	Flexibility (see GB/T1731-93, measured with mandrels of different diameters)	50mm

It should be noted that, there is no special inspection standard for the flexibility inspection of the coating, and the method adopted in the industry at present is for reference from GB/T1731-93, which is mainly aimed at the inspection of thin-layer top-coat paint type coatings, which are thin, so that the shaft rod with the maximum diameter given in the standard still cannot be used for the inspection of the wave-absorbing coating. The flexibility test of the wave-absorbing coating refers to the standard, and the diameter of the mandrel is an integral dozen, such as 50mm, 60mm, 70mm, 80mm, 90mm, 100 mm, 110mm, 120mm and the like.

Example 2

(1) Mixing and stirring liquid carboxyl-terminated butadiene-acrylonitrile rubber (CTBN) with the molecular weight of 8000-15000 and bisphenol A epoxy resin with the epoxy equivalent of 180-220 according to the mass ratio of 12:100, wherein the stirring speed is 150r/min, and the stirring time is 10min, so as to obtain the modified epoxy resin.

(2) Mixing and stirring an absorbent, a coupling agent KH560 and a diluent according to a mass ratio of 1000:10:2500 at a stirring speed of 450r/min for 25min, wherein the absorbent is a flaky ferromagnetic absorbent with a thickness of 100-500nm and a diameter of 3-10 μm, and the diluent is ethyl acetate, n-butanol and ethanol in a ratio of 2:1: 1.

(3) And (3) mixing and stirring the anti-aging agent, the anti-settling agent and the defoaming agent with the mixture obtained in the step (2) at the stirring speed of 450r/min for 10min, wherein the using amounts of the anti-aging agent, the anti-settling agent and the defoaming agent meet the following condition that the mass ratio of the absorbent to the anti-aging agent to the anti-settling agent to the defoaming agent is 1000:1.5:1: 2.

(4) Mixing and stirring the modified epoxy resin and the mixture obtained in the step (3), wherein the stirring speed is 450r/min, and the stirring time is 10 min; the amount of the modified epoxy resin is such that the mass ratio of the modified epoxy resin to the absorbent is 18: 82.

(5) And (4) grinding the mixture obtained in the step (4) on a three-roll grinder, wherein the rotating speed of a discharge grinding roll of the three-roll grinder is 200r/min, and the grinding time is 60min, so as to obtain the electromagnetic functional coating.

(6) Weighing a curing agent triethylene tetramine, adding the curing agent triethylene tetramine into the electromagnetic functional coating, wherein the mass ratio of the triethylene tetramine to the modified epoxy resin is 1:100, then adding a diluent, wherein the diluent is a mixture composed of ethyl acetate, n-butyl alcohol and ethanol according to a ratio of 2:1:1, adjusting the viscosity of the electromagnetic functional coating to be 25s, mixing and stirring, and stirring at a rotation speed of 100r/min for 2 min.

(7) And (3) forming a coating on the mixture obtained in the step (6) by using a spraying process, adjusting spraying process parameters, setting the caliber of a spray gun to be phi 1.5mm, the spraying pressure to be 0.3-0.5MPa, and the spraying interval to be not less than 20min, curing after the spraying is finished, wherein the curing condition is that the temperature is 70 ℃, the time is 4 hours, and the final coating thickness is 1.02mm, so that the requirements of the electromagnetic function and the mechanical property of the target C waveband can be met.

The obtained product has excellent reflectivity which is lower than-10 dB and reaches-24 dB at 6GHz within the frequency band of 4GHz-8GHz as shown in figure 4.

The mechanical properties of the electromagnetic functional coating are shown in table 2.

TABLE 2

Serial number	Item	Measured value
			1	Adhesion (MPa)	5.35
2	Impact Strength (kg. cm)	46
			3	Flexibility (see GB/T1731-93, measured with mandrels of different diameters)	50mm

Example 3

(1) Mixing and stirring liquid carboxyl-terminated butadiene-acrylonitrile rubber (CTBN) with the molecular weight of 8000-15000 and bisphenol A epoxy resin with the epoxy equivalent of 180-220 according to the mass ratio of 15:100, wherein the stirring speed is 120r/min, and the stirring time is 10min, so as to obtain the modified epoxy resin.

(2) Mixing and stirring an absorbent, a coupling agent KH560 and a diluent according to a mass ratio of 1000:5:2200 at a stirring speed of 500r/min for 20min, wherein the absorbent is a sheet-shaped ferromagnetic absorbent with a thickness of 100-500nm and a diameter of 3-10 μm, and the diluent is ethyl acetate, n-butanol and ethanol in a ratio of 2:1: 1.

(3) And (3) mixing and stirring the anti-aging agent, the anti-settling agent and the defoaming agent with the mixture obtained in the step (2) at the stirring speed of 450r/min for 8min, wherein the using amounts of the anti-aging agent, the anti-settling agent and the defoaming agent meet the following condition that the mass ratio of the absorbent to the anti-aging agent to the anti-settling agent to the defoaming agent is 1000:1.5:1: 2.

(4) Mixing and stirring the modified epoxy resin and the mixture obtained in the step (3), wherein the stirring speed is 400r/min, and the stirring time is 5 min; the amount of the modified epoxy resin is such that the mass ratio of the modified epoxy resin to the absorbent is 16: 84.

(6) Weighing a curing agent triethylene tetramine, adding the curing agent triethylene tetramine into the electromagnetic functional coating, wherein the mass ratio of the triethylene tetramine to the modified epoxy resin is 0.5:100, then adding a diluent, wherein the diluent is a mixture composed of ethyl acetate, n-butyl alcohol and ethanol according to a ratio of 2:1:1, adjusting the viscosity of the electromagnetic functional coating to be 22s, mixing and stirring, and stirring at a rotation speed of 100r/min for 2 min.

(7) And (3) forming a coating on the mixture obtained in the step (6) by using a spraying process, adjusting spraying process parameters, setting the caliber of a spray gun to be phi 1.5mm, the spraying pressure to be 0.3-0.5MPa, and the spraying interval to be not less than 20min, curing after the spraying is finished, wherein the curing condition is that the temperature is 70 ℃, the time is 4 hours, and the final coating thickness is 1.01mm, so that the requirements of the electromagnetic function and the mechanical property of the target C waveband can be met.

The obtained product has excellent reflectivity which is lower than-10 dB and reaches-22 dB at 6.5GHz within the frequency band of 4GHz-8GHz as shown in figure 5.

The mechanical properties of the electromagnetic functional coating are shown in table 3.

TABLE 3

Serial number	Item	Measured value
			1	Adhesion (MPa)	5.86
2	Impact Strength (kg. cm)	50
			3	Flexibility (see GB/T1731-93, measured with mandrels of different diameters)	50mm

Example 4

(1) Mixing and stirring liquid carboxyl-terminated butadiene-acrylonitrile rubber (CTBN) with the molecular weight of 8000-15000 and bisphenol A epoxy resin with the epoxy equivalent of 180-220 according to the mass ratio of 18:100, wherein the stirring speed is 180r/min, and the stirring time is 7min, so as to obtain the modified epoxy resin.

(2) Mixing and stirring an absorbent, a coupling agent KH560 and a diluent according to a mass ratio of 1000:5:2000, wherein the stirring speed is 400r/min, and the stirring time is 30min, wherein the absorbent is a sheet-shaped ferromagnetic absorbent, the thickness is 100-500nm, the diameter is 3-10 mu m, and the diluent is ethyl acetate, n-butyl alcohol and ethanol in a ratio of 2:1: 1.

(3) And (3) mixing and stirring the anti-aging agent, the anti-settling agent and the defoaming agent with the mixture obtained in the step (2) at a stirring speed of 400r/min for 10min, wherein the using amounts of the anti-aging agent, the anti-settling agent and the defoaming agent meet the following condition that the mass ratio of the absorbent to the anti-aging agent to the anti-settling agent to the defoaming agent is 1000:1.5:1: 2.

(4) Mixing and stirring the modified epoxy resin and the mixture obtained in the step (3), wherein the stirring speed is 400r/min, and the stirring time is 10 min; the amount of the modified epoxy resin used satisfies the condition that the mass ratio of the modified epoxy resin to the absorbent is 13: 87.

(6) Weighing a curing agent triethylene tetramine, adding the curing agent triethylene tetramine into the electromagnetic functional coating, wherein the mass ratio of the triethylene tetramine to the modified epoxy resin is 0.5:100, then adding a diluent, wherein the diluent is a mixture composed of ethyl acetate, n-butyl alcohol and ethanol according to a ratio of 2:1:1, adjusting the viscosity of the electromagnetic functional coating to 24s, mixing and stirring, and stirring at a rotation speed of 150r/min for 2 min.

(7) And (3) forming a coating on the mixture obtained in the step (6) by using a spraying process, adjusting spraying process parameters, setting the caliber of a spray gun to be phi 1.5mm, the spraying pressure to be 0.3-0.5MPa, and the spraying interval to be not less than 20min, curing after the spraying is finished, wherein the curing condition is that the temperature is 70 ℃, the time is 4 hours, and the final coating thickness is 1.06mm, so that the requirements of the electromagnetic function and the mechanical property of the target C waveband can be met.

The obtained product has excellent reflectivity which is lower than-10 dB and reaches-22 dB at 6GHz within the frequency band of 4GHz-8GHz as shown in figure 6.

The mechanical properties of the magnetic functional coating are shown in table 4.

TABLE 4

Serial number	Item	Measured value
			1	Adhesion (MPa)	5.44
2	Impact Strength (kg. cm)	42
			3	Flexibility (see GB/T1731-93, measured with mandrels of different diameters)	60mm

Example 5

(1) Mixing and stirring liquid carboxyl-terminated butadiene-acrylonitrile rubber (CTBN) with the molecular weight of 8000-15000 and bisphenol A epoxy resin with the epoxy equivalent of 180-220 according to the mass ratio of 20:100, wherein the stirring speed is 200r/min, and the stirring time is 10min, so as to obtain the modified epoxy resin.

(2) Mixing and stirring an absorbent, a coupling agent KH560 and a diluent according to a mass ratio of 1000:5:2000, wherein the stirring speed is 500r/min, and the stirring time is 30min, wherein the absorbent is a sheet-shaped ferromagnetic absorbent, the thickness is 100-500nm, the diameter is 3-10 mu m, and the diluent is ethyl acetate, n-butyl alcohol and ethanol in a ratio of 2:1: 1.

(3) And (3) mixing and stirring the anti-aging agent, the anti-settling agent and the defoaming agent with the mixture obtained in the step (2) at a stirring speed of 500r/min for 10min, wherein the using amounts of the anti-aging agent, the anti-settling agent and the defoaming agent meet the following condition that the mass ratio of the absorbent to the anti-aging agent to the anti-settling agent to the defoaming agent is 1000:1.5:1: 2.

(4) Mixing and stirring the modified epoxy resin and the mixture obtained in the step (3), wherein the stirring speed is 500r/min, and the stirring time is 10 min; the dosage of the modified epoxy resin meets the following condition that the mass ratio of the modified epoxy resin to the absorbent is 10: 90.

(6) Weighing a curing agent triethylene tetramine, adding the curing agent triethylene tetramine into the electromagnetic functional coating, wherein the mass ratio of the triethylene tetramine to the modified epoxy resin is 0.5:100, then adding a diluent, wherein the diluent is a mixture composed of ethyl acetate, n-butyl alcohol and ethanol according to a ratio of 2:1:1, adjusting the viscosity of the electromagnetic functional coating to be 25s, mixing and stirring, and stirring at a rotation speed of 200r/min for 3 min.

(7) And (3) forming a coating on the mixture obtained in the step (6) by using a spraying process, adjusting spraying process parameters, setting the caliber of a spray gun to be phi 1.5mm, the spraying pressure to be 0.3-0.5MPa, and the spraying interval to be not less than 20min, curing after the spraying is finished, wherein the curing condition is that the temperature is 70 ℃, the time is 4 hours, and the final coating thickness is 1.1mm, so that the requirements of the electromagnetic function and the mechanical property of the target C waveband can be met.

The obtained product has excellent reflectivity which is lower than-10 dB and reaches-30 dB at 5GHz within the frequency band of 4GHz-8GHz as shown in figure 7.

The mechanical properties of the electromagnetic functional coating are shown in table 5.

TABLE 5

Example 6

The preparation of example 6 is essentially the same as example 1, except that:

in the step (1), the mass ratio of the liquid carboxyl-terminated butadiene-acrylonitrile rubber to the bisphenol A type epoxy resin is 5: 100.

TABLE 6

Serial number	Item	Measured value
			1	Adhesion (MPa)	6.21
2	Impact Strength (kg. cm)	45
			3	Flexibility (see GB/T1731-93, measured with mandrels of different diameters)	150mm

Example 7

The preparation of example 7 is essentially the same as example 1, except that:

in the step (1), the mass ratio of the liquid carboxyl-terminated butadiene-acrylonitrile rubber to the bisphenol A type epoxy resin is 30: 100.

TABLE 7

Serial number	Item	Measured value
			1	Adhesion (MPa)	1.20
2	Impact Strength (kg. cm)	35
			3	Flexibility (see GB/T1731-93, measured with mandrels of different diameters)	60mm

Example 8

The preparation of example 8 is essentially the same as example 1, except that:

in the step (4), the mass ratio of the absorbent to the modified epoxy resin is 30: 70.

FIG. 8 is a reflectivity curve of the coating prepared in example 8, the radar absorbing performance of the coating is very poor and is higher than-2 dB.

Example 9

The preparation of example 9 is essentially the same as example 1, except that:

in step (6), the viscosity of the mixture was adjusted to 15s by adjusting the amount of the diluent.

TABLE 8

Serial number	Item	Measured value
			1	Adhesion (MPa)	4.88
2	Impact Strength (kg. cm)	40
			3	Flexibility (see GB/T1731-93, measured with mandrels of different diameters)	120mm

Example 10

Example 10 was prepared essentially as in example 1, except that:

in step (6), the viscosity of the mixture was adjusted to 30s by adjusting the amount of the diluent.

TABLE 8

Serial number	Item	Measured value
			1	Adhesion (MPa)	1.02
2	Impact Strength (kg. cm)	39
			3	Flexibility (see GB/T1731-93, measured with mandrels of different diameters)	60mm

Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present invention, but not to limit the same; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.

Claims

1. A composition for producing a C-band electromagnetically functional coating, the composition comprising:

(A) an absorbent;

2. The composition of claim 1,

the absorbent is a sheet ferromagnetic absorbent, the thickness is 100-500nm, and the diameter is 3-10 μm;

3. The composition according to claim 1 or 2,

the composition further comprises one or more of the following additives:

a coupling agent, preferably a silane coupling agent;

an anti-aging agent;

an anti-settling agent; and/or

And (4) defoaming agent.

4. The composition of claim 3,

the mass ratio of the first diluent to the absorbent is (2-3) to 1;

the mass ratio of the coupling agent to the absorbent is (5-10) 1000;

the mass ratio of the anti-aging agent to the absorbent is (1-5) to 1000;

The mass ratio of the defoaming agent to the absorbent is (1-5) to 1000.

5. The composition according to any one of claims 1 to 4,

the composition further comprises:

6. A method for preparing a C-band electromagnetic functional coating by using the composition of any one of claims 1 to 5, wherein the method comprises the following steps:

(1) a step of preparing the resin matrix component to obtain a modified resin;

7. The method of claim 6,

the step (1) comprises the following steps:

8. The method according to claim 6 or 7,

the step (2) comprises the following steps:

9. The method according to any one of claims 6 to 8,

the step (3) comprises the following steps:

10. The method of claim 9,

the spraying pressure of the spraying is 0.3-0.5MPa, and the spraying interval is not less than 20 min;

the curing temperature is 60-70 ℃, and the curing time is 2-4 h; and/or