Composite coating with electromagnetic protection and explosion-proof functions, preparation method and application

Abstract

The invention belongs to the technical field of electromagnetic wave absorbing materials, and discloses a composite coating with electromagnetic protection and explosion-proof functions as well as a preparation method and application of the composite coating. The coating comprises 40 to 60 parts of polycarbodiimide modified diphenylmethane diisocyanate, 40 to 60 parts of a semi-prepolymer which is synthesized from polycarbonate diol with the equivalent weight of 1000 and has the NCO content of 10 to 20 percent, 73 to 100 parts of a polyether amine curing agent, 15 to 20 parts of diethyl toluenediamine or dimethyl thio toluenediamine, 0.5 to 2 parts of calcium carbonate and 3 to 6 parts of magnetic powder. And the two components are quickly reacted and molded through a spraying process. According to the invention, the polyurea elastomer is used as a matrix, so that the coating is endowed with excellent impact resistance, explosion-proof characteristics, water impermeability, oil resistance, low temperature resistance and other environmental tolerance; meanwhile, an adjustable electromagnetic wave absorption function is realized by doping specific magnetic powder. The coating is simple in preparation process and excellent in comprehensive performance, and is particularly suitable for equipment surfaces with high requirements on stealth and survival protection, such as oil storage equipment.

Description

Technical Field

[0001] This invention belongs to the field of electromagnetic wave absorbing materials technology. Specifically, this invention relates to a composite coating that combines electromagnetic protection and explosion-proof functions, its preparation method, and its application. Background Technology

[0002] In complex electromagnetic environments, the radar stealth and survivability of equipment are crucial. Radar-absorbing coatings, as an effective means of controlling target radar signatures, have been widely used. Among them, carbonyl iron powder, with its high magnetic permeability and high Curie temperature, is one of the most widely used magnetic absorbers. However, traditional radar-absorbing coatings based on thermosetting resins such as epoxy, phenolic, and polyimide generally suffer from drawbacks such as high brittleness, insufficient toughness, and poor impact resistance. When the equipment surface is subjected to fragment impacts or explosive shock loads, these coatings are prone to cracking, powdering, and flaking, rendering them unable to meet the radar stealth requirements of the target. In addition, the environmental tolerance of radar-absorbing coatings, such as water permeability, abrasion resistance, impact resistance, low-temperature resistance, and oil resistance, are also key indicators for evaluating their engineering application value. Therefore, developing multifunctional coatings that maintain excellent radar absorption performance while possessing good explosion-proof characteristics and environmental resistance has become a key approach to improving the overall effectiveness of equipment.

[0003] Polyurea elastomers, as high-performance polymers generated through the rapid reaction of isocyanates and amino compounds, possess unique molecular structures and reaction mechanisms that endow them with great potential as protective coatings for equipment surfaces. In terms of mechanical properties, their extremely high elongation at break and energy dissipation capacity give the coating excellent explosion-proof and impact-resistant characteristics. Regarding environmental resistance, the extremely low water permeability of polyurea materials effectively blocks moisture penetration, preventing coating blistering, peeling, and oxidation failure; its excellent low-temperature resistance allows it to maintain high elasticity in cold environments, avoiding embrittlement and cracking; simultaneously, its superior oil resistance resists the erosion of chemical media such as fuel oil, ensuring the long-term reliability of the coating in oily environments.

[0004] In existing technologies, radar-absorbing and explosion-proof polyurea materials with ferrite as the main absorber are used. These materials possess good explosion-proof and radar-absorbing properties, but their environmental resistance is lacking, making it difficult to meet the radar signature control requirements of targets in complex environments. Existing technologies have also prepared compound flame-retardant coating materials using organic-inorganic flame retardants, exhibiting high flame-retardant properties and adhesion, but lacking stealth performance. Furthermore, existing technologies have used polyether-type polyurethane elastomers as a matrix to prepare camouflage-functional oil reservoir materials. These coating materials have good water resistance, oil resistance, and environmental resistance, and possess visible / near-infrared camouflage capabilities, but lack stealth performance in the microwave band. Summary of the Invention

[0005] To address the aforementioned problems in existing technologies, this invention provides a composite coating that combines electromagnetic protection and explosion-proof functions, its preparation method, and its application. The preparation method is simple and easy to implement, and the resulting coating exhibits excellent explosion-proof performance, electromagnetic protection performance, and mechanical properties, meeting electromagnetic protection requirements across different frequency ranges. Furthermore, it possesses strong environmental resistance, such as wear resistance, impact resistance, water impermeability, oil resistance, and low-temperature resistance.

[0006] This invention provides a composite coating with both electromagnetic protection and explosion-proof functions, comprising 40-60 parts of a semi-prepolymer with an NCO content of 10-20% synthesized from polycarbodiimide-modified diphenylmethane diisocyanate and 40-60 parts of polycarbonate diol, 73-100 parts of polyetheramine curing agent, 15-20 parts of diethyltoluenediamine or dimethylthiotoluenediamine, 0.5-2 parts of calcium carbonate, and 3-6 parts of magnetic powder.

[0007] Optionally, the polyetheramine curing agent includes JEFFAMINET-5000 and JEFFAMINED-2000.

[0008] Optionally, 73-100 parts of polyetheramine curing agent include 8-12 parts of JEFFAMINE T-5000 and 65-80 parts of JEFFAMINE D-2000.

[0009] Optionally, the magnetic powder is at least one of flake carbonyl iron powder, flake iron-silicon-aluminum alloy powder, or flake iron-silicon-chromium alloy powder, with a particle size of 10~50μm.

[0010] Another aspect of the present invention discloses a method for preparing the aforementioned composite coating that combines electromagnetic protection and explosion-proof functions, comprising the following steps: S1: Polycarbodiimide-modified diphenylmethane diisocyanate is reacted with polycarbonate diol to synthesize an isocyanate semi-prepolymer with an NCO content of 10%~20%, which is used as component A; S2: Polyetheramine curing agent, aromatic diamine chain extender, nano-calcium carbonate and magnetic powder are blended to obtain component R; S3: The components A and R are coated onto the substrate surface using a compressed air spraying process, and the reaction forms the composite coating.

[0011] Optionally, in step S3, the volume ratio of component A to component R is 0.5 to 2, and a compressed air spraying process is used, with a spraying time of 3 to 10 seconds.

[0012] Optionally, the parameters of the compressed air spraying process are: spray gun diameter 1~2mm, air pressure 0.5~1.2MPa, and spraying distance 10~100cm.

[0013] Optionally, in step S3, the substrate surface is pretreated by grinding and solvent cleaning before spraying.

[0014] A third aspect of the present invention also discloses the application of the aforementioned composite coating in an oil storage device.

[0015] Optionally, the composite coating is sprayed onto the oil storage device to achieve broadband effective electromagnetic absorption in the 2~18GHz frequency band.

[0016] Compared with the prior art, the present invention has at least the following beneficial effects: (1) This invention introduces magnetic powder into polyurea elastomer to prepare a microwave absorbing coating material with explosion-proof properties. The polyurea matrix can overcome the shortcomings of conventional thermosetting resin matrices such as epoxy, phenolic, and polyimide, which are brittle, lack toughness, and have poor impact resistance. The magnetic powder can fully utilize its dielectric and magnetic loss characteristics to efficiently absorb electromagnetic waves.

[0017] (2) The addition of calcium carbonate filler in this invention improves the toughness and impact resistance of the coating, further optimizes its explosion-proof performance, and improves the environmental tolerance of the coating.

[0018] (3) The coating of the present invention can be sprayed over a large area, and the gelation time is short, which is convenient and quick. Attached Figure Description

[0019] The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of the invention.

[0020] Figure 1 This is a reflectivity curve of Embodiment 1 of the present invention in the frequency range of 2~18 GHz under room temperature conditions; Figure 2 This is a reflectivity curve of Embodiment 2 of the present invention in the frequency range of 2~18 GHz under room temperature conditions; Figure 3 This is a reflectivity curve of Embodiment 3 of the present invention in the frequency range of 2~18 GHz under room temperature conditions. Detailed Implementation

[0021] To better understand the above-described objectives, features, and advantages of the present invention, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, unless otherwise specified, the embodiments of the present invention and the features thereof can be combined with each other. Furthermore, the present invention can be implemented in other ways different from those described herein; therefore, the scope of protection of the present invention is not limited to the specific embodiments disclosed below.

[0022] A specific embodiment of the present invention, such as Figure 1-3A composite coating with both electromagnetic protection and explosion-proof functions is disclosed, comprising 40-60 parts of polycarbodiimide-modified diphenylmethane diisocyanate and 40-60 parts of a semi-prepolymer with an NCO content of 10-20% synthesized from polycarbonate diol with an equivalent of 1000, 73-100 parts of polyetheramine curing agent, 15-20 parts of diethyltoluenediamine or dimethylthiotoluenediamine, 0.5-2 parts of calcium carbonate and 3-6 parts of magnetic powder.

[0023] It is understandable that NCO content refers to the percentage of isocyanate groups in a chemical substance.

[0024] Furthermore, 73-100 parts of polyetheramine curing agent include 8-12 parts of JEFFAMINE T-5000 and 65-80 parts of JEFFAMINE D-2000; the magnetic powder is carbonyl iron powder.

[0025] Furthermore, the composite coating comprises 50 parts of a semi-prepolymer with an NCO content of 12.6% synthesized from polycarbodiimide-modified diphenylmethane diisocyanate and 50 parts of polycarbonate diol with an equivalent of 1000, as well as 10 parts of JEFFAMINE T-5000, 72.75 parts of JEFFAMINE D-2000, 17.25 parts of diethyltoluene diamine, 1 part of calcium carbonate, and 4 parts of carbonyl iron powder.

[0026] Another specific embodiment discloses a method for preparing a composite coating that combines electromagnetic protection and explosion-proof functions, the specific steps of which are as follows: S1. Polycarbodiimide-modified diphenylmethane diisocyanate and polycarbonate diol are used to synthesize semi-prepolymer component A; In component A, the mass ratio of polycarbodiimide-modified diphenylmethane diisocyanate to polycarbonate diol is 1.0~2.5; the NCO% of the semi-prepolymer is 10~20%.

[0027] S2. Component R is obtained by blending polyetheramine curing agent, diethyltoluenediamine or dimethylthiotoluenediamine, calcium carbonate and magnetic powder; Among them, the mass fractions of polyetheramine curing agent, diethyltoluenediamine, calcium carbonate and magnetic powder in component R are 70.56~80.56%, 20.44~28.44%, 0.7~3.9% and 4.9~11.7%, respectively.

[0028] S3. The components A and R are sprayed onto the pretreated substrate in a preset volume ratio using a compressed air spraying process to form a polyurea elastomer microwave absorbing coating.

[0029] The volume ratio of components A to R is 0.5 to 2; the gelation time of the coating is 3 to 10 seconds.

[0030] Optionally, the polycarbodiimide-modified diphenylmethane diisocyanate in step S1 is Isonate. ® .

[0031] Optionally, in step S2, the magnetic powder is at least one of flake carbonyl iron powder, flake iron-silicon-aluminum alloy powder, and flake iron-silicon-chromium alloy powder; the particle size range of the magnetic powder is 10~50 μm; and the particle size range of calcium carbonate is 1~500 nm.

[0032] Optionally, the polyetheramine curing agent in step S2 is JEFFAMINE T-5000 or JEFFAMINE D-2000.

[0033] Optionally, in step S3, the compressed air spraying process has a spray gun diameter of 1~2 mm, an air pressure of 0.5~1.2 MPa, a spraying distance of 10~100 cm, a spraying angle of 90°, a spraying thickness of 2 mm, and allows the spraying to dry at room temperature between adjacent spraying passes.

[0034] Optionally, the pretreatment in step 3 involves polishing with 200-grit sandpaper and ultrasonically cleaning the substrate with ethanol.

[0035] Thirdly, the present invention also discloses the application of a composite coating that combines electromagnetic protection and explosion-proof functions, for use in oil storage equipment.

[0036] To illustrate the effectiveness of the method proposed in this invention, the above technical solution of this invention will be described in detail below through several specific embodiments.

[0037] Example 1 S1 will Isonate ® A semi-prepolymer with an NCO% of 12.6% was synthesized by combining 50 parts of 143L and 50 parts of polycarbonate diol with an equivalent of 1000. This is component A.

[0038] S2 Component R is obtained by blending 10 parts of JEFFAMINE T-5000, 72.75 parts of JEFFAMINE D-2000, 17.25 parts of diethyltoluene diamine, 1 part of calcium carbonate and 4 parts of carbonyl iron powder.

[0039] S3 Components A and R are blended in a volume ratio of 1:1 to obtain a spray coating.

[0040] S4 uses anhydrous ethanol as a medium to ultrasonically clean the substrate and then sands its surface. The spray gun nozzle diameter is set to 1.5 mm, the air pressure to 1.0 MPa, the spraying distance to 50 cm, the spraying angle to 90°, and the spraying thickness to 2 mm. The substrate is allowed to dry at room temperature between adjacent passes.

[0041] Once the S5 coating is surface dry after spraying, a microwave absorbing coating material with explosion-proof properties can be obtained.

[0042] Example 2 S1 will Isonate ® A semi-prepolymer with an NCO% of 16% was synthesized by combining 60 parts of 143L and 40 parts of polycarbonate diol with an equivalent of 1000. This is component A.

[0043] S2 Component R is obtained by blending 10 parts of JEFFAMINE T-5000, 65.56 parts of JEFFAMINE D-2000, 24.44 parts of diethyltoluene diamine, 3 parts of calcium carbonate and 7 parts of carbonyl iron powder.

[0044] S3 Components A and R are blended in a volume ratio of 1:1 to obtain a spray coating.

[0045] S4 uses anhydrous ethanol as a medium to ultrasonically clean the substrate and then sands its surface. The spray gun nozzle diameter is set to 1.5 mm, the air pressure to 1.0 MPa, the spraying distance to 50 cm, the spraying angle to 90°, and the spraying thickness to 2 mm. The substrate is allowed to dry at room temperature between adjacent passes.

[0046] Once the S5 coating is surface dry after spraying, a microwave absorbing coating material with explosion-proof properties can be obtained.

[0047] Example 3 S1 will Isonate ® A semi-prepolymer with an NCO% of 18% was synthesized from 66 parts of 143L and 34 parts of polycarbonate diol with an equivalent of 1000, which is component A.

[0048] S2 10 parts JEFFAMINE T-5000, 61.33 parts JEFFAMINE D-2000, 28.67 parts diethyltoluene diamine, 2 parts calcium carbonate and 3 parts carbonyl iron powder were blended to obtain component R.

[0049] S3 Components A and R are blended in a volume ratio of 1:1 to obtain a spray coating.

[0050] S4 uses anhydrous ethanol as a medium to ultrasonically clean the substrate and then sands its surface. The spray gun nozzle diameter is set to 1.5 mm, the air pressure to 1.0 MPa, the spraying distance to 50 cm, the spraying angle to 90°, and the spraying thickness to 1.2 mm. The substrate is allowed to dry at room temperature between adjacent passes.

[0051] S5 uses anhydrous ethanol as a medium to ultrasonically clean the substrate and then sands its surface. The spray gun nozzle diameter is set to 1.5 mm, the air pressure to 1.0 MPa, the spraying distance to 50 cm, the spraying angle to 90°, and the spraying thickness to 1.0 mm. The substrate is allowed to dry at room temperature between adjacent passes.

[0052] Once the S6 coating is surface dry after spraying, a microwave absorbing coating material with explosion-proof properties can be obtained.

[0053] Comparative Example 1 is Example 1 from the patent application CN202011259733.9, which describes a radar-absorbing explosion-proof polyurea material and its preparation method.

[0054] The microwave absorption performance test was conducted in accordance with GJB2038A-2011, and the explosion protection performance test was conducted in accordance with GJB8455-2015. The performance test comparison table is shown in Table 1.

[0055] Table 1 Performance Test Comparison

[0056] As shown in Table 1, Examples 1-3 all exhibit excellent explosion-proof and environmental resistance. However, due to differences in the content of magnetic powder, the three coatings exhibit different electromagnetic properties, resulting in different radar absorption performances. The effective absorption bandwidth (reflection loss < -10 dB) of Example 1 covers the entire C-band (4-8 GHz), the effective absorption bandwidth (reflection loss < -10 dB) of Example 2 covers the entire X-band (8.2-12.4 GHz), and the effective absorption bandwidth (reflection loss < -10 dB) of Example 3 covers 2.4-18 GHz, meeting the radar stealth requirements in complex environments. Compared with Comparative Example 1, the three examples exhibit significantly higher elongation at break and Shore hardness, while also demonstrating water impermeability, low-temperature resistance, and oil resistance.

[0057] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A composite coating that combines electromagnetic protection and explosion-proof functions, characterized in that, It includes a semi-prepolymer with an NCO content of 10-20% synthesized from 40-60 parts of polycarbodiimide-modified diphenylmethane diisocyanate and 40-60 parts of polycarbonate diol, as well as 73-100 parts of polyetheramine curing agent, 15-20 parts of diethyltoluenediamine or dimethylthiotoluenediamine, 0.5-2 parts of calcium carbonate and 3-6 parts of magnetic powder.

2. The composite coating according to claim 1, characterized in that, The polyetheramine curing agents include JEFFAMINET-5000 and JEFFAMINED-2000.

3. The composite coating according to claim 2, characterized in that, 73-100 parts of polyetheramine curing agent include 8-12 parts of JEFFAMINE T-5000 and 65-80 parts of JEFFAMINE D-2000.

4. The composite coating according to claim 1, characterized in that, The magnetic powder is at least one of flake carbonyl iron powder, flake iron-silicon-aluminum alloy powder, or flake iron-silicon-chromium alloy powder, with a particle size of 10~50μm.

5. A method for preparing a composite coating with both electromagnetic protection and explosion-proof functions as described in any one of claims 1-4, characterized in that, Includes the following steps: S1: Polycarbodiimide-modified diphenylmethane diisocyanate is reacted with polycarbonate diol to synthesize an isocyanate semi-prepolymer with an NCO content of 10%~20%, which is used as component A; S2: Polyetheramine curing agent, aromatic diamine chain extender, nano-calcium carbonate and magnetic powder are blended to obtain component R; S3: The components A and R are coated onto the substrate surface using a compressed air spraying process, and the reaction forms the composite coating.

6. The preparation method according to claim 5, characterized in that, In step S3, the volume ratio of component A to component R is 0.5 to 2, and a compressed air spraying process is used, with a spraying time of 3 to 10 seconds.

7. The preparation method according to claim 5, characterized in that, The parameters of the compressed air spraying process are: spray gun diameter 1~2mm, air pressure 0.5~1.2MPa, and spraying distance 10~100cm.

8. The preparation method according to claim 5, characterized in that, In step S3, the substrate surface is pretreated by grinding and solvent cleaning before spraying.

9. The application of the composite coating according to any one of claims 1-4 in coating oil storage equipment.

10. The application according to claim 9, characterized in that, The composite coating is sprayed onto the oil storage equipment to achieve wideband effective electromagnetic absorption in the 2~18GHz frequency band.

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