A radar wave absorbing coating and a preparation method thereof

Abstract

The application relates to the technical field of wave-absorbing coatings, and discloses radar wave-absorbing coating and a preparation method thereof. The radar wave-absorbing coating comprises 100 parts by weight of water-based polyurethane emulsion, 0.4-1.6 parts by weight of graphene oxide and 0.3-2 parts by weight of modified ferroferric oxide. The surface of the nano-ferroferric oxide is introduced with multiple hydrophilic hydroxyl groups and carboxyl groups, the surface hydrophilicity is improved, the nano-ferroferric oxide is uniformly dispersed in the water-based polyurethane coating, the coating has higher mechanical strength and tensile property. The multiple hydroxyl groups and carboxyl groups introduced on the surface of the nano-ferroferric oxide form hydrogen bonds and other interactions with the hydroxyl groups and carboxyl groups on the surface of the graphene oxide, the interface action between the nano-ferroferric oxide and the graphene oxide is improved, the impedance matching property of the two is improved, the interface polarization effect is formed, and the absorption effect of the coating on electromagnetic waves is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of wave-absorbing coatings, in particular to a radar wave-absorbing coating and a preparation method thereof. BACKGROUND

[0002] Wave-absorbing materials can weaken or absorb the electromagnetic wave energy received on their surface, and can reduce electromagnetic wave interference. Wave-absorbing agents mainly include ferrites, carbon materials, conductive polymers, etc., and can be made into wave-absorbing coatings, wave-absorbing fabrics, wave-absorbing silica gel, etc., and are widely used in radar wave-absorbing and military stealth technology, communication and electronic systems, etc. Developing thin, light, wide and strong wave-absorbing materials is a research hotspot.

[0003] Water-based polyurethane coatings are green, high in toughness, good in mechanical properties, excellent in weather resistance, and widely used. Adding nano-iron oxide to water-based polyurethane can endow it with good wave-absorbing and mechanical properties. Patent No. CN113956775B discloses a thin wave-absorbing basalt flake polyurethane coating and a coating method thereof. The ferrite is modified by using a silane coupling agent such as KH570, which can improve the corrosion resistance of the basalt flake polyurethane coating. However, ordinary nano-iron oxide and ferrite modified by a silane coupling agent have hydrophobic surfaces and poor hydrophilicity, and are prone to aggregation in water-based coatings, which affects the mechanical properties and wave-absorbing properties of the coating. SUMMARY

[0004] In view of the deficiencies of the prior art, the present application provides a radar wave-absorbing coating and a preparation method thereof, which solves the problem of poor dispersibility of nano-iron oxide in water-based polyurethane coatings, and also solves the problem of poor wave-absorbing properties of polyurethane coatings.

[0005] The technical solution of the present application is: a radar wave-absorbing coating and a preparation method thereof, which comprises 100 parts by weight of water-based polyurethane emulsion, 0.4-1.6 parts by weight of graphene oxide, 0.3-2 parts by weight of modified iron oxide, 0.3-0.8 parts by weight of defoaming agent, and 0.2-0.5 parts by weight of wetting agent.

[0006] The preparation method of the radar wave-absorbing coating is as follows:

[0007] (1) Add water and nano-iron oxide to a flask, ultrasonically disperse, then add a modifier with the following structural formula: After stirring, filter, wash with water, and dry to obtain modified iron oxide.

[0008] (2) Add water-based polyurethane emulsion, graphene oxide and modified iron oxide to a container, stir to mix, then add defoaming agent and wetting agent, and stir to obtain a radar wave-absorbing coating.

[0009] Further, the amount of the nano-Fe3O4 in (1) is 100 parts by weight, and the amount of the modifier is 3-10 parts by weight.

[0010] Further, the temperature during stirring in (1) is 60-85℃, and the stirring time is 2-5h.

[0011] Further, the stirring and mixing time in (2) is 40-60min.

[0012] Further, the preparation method of the modifier is as follows: water, 100 parts by weight of ethylenediamine-N,N'-diacetic acid (the structural formula is ), and 106-132 parts by weight of glycidol (the structural formula is ) are added into a flask, and then an aqueous solution containing 68-80 parts by weight of sodium hydroxide is added dropwise after stirring, the temperature is increased to 55-70℃, and stirring reaction is performed for 6-10h, the imino group of ethylenediamine-N,N'-diacetic acid and the epoxy group of glycidol are subjected to addition reaction by taking sodium hydroxide as a catalyst, after the reaction, 20-37% hydrochloric acid by mass fraction is added dropwise to adjust the pH to 3-4, crystals are precipitated, and after filtration and drying, the modifier is obtained, and the structural formula is .

[0013] Beneficial technical effects: the nano-Fe3O4 is surface-modified by the modifier, and then the modified nano-Fe3O4 and graphene oxide are used as a composite wave-absorbing agent and added into water-based polyurethane paint to obtain radar wave-absorbing paint. The modifier contains multiple hydroxyl groups and carboxyl groups, the multiple hydroxyl groups form strong coordination with iron ions on the surface of the nano-Fe3O4, so that the modifier is modified on the surface of the nano-Fe3O4, which is beneficial to improve the dispersibility of the nano-Fe3O4 particles and solve the problem of agglomeration, and the multiple hydrophilic hydroxyl groups and carboxyl groups are introduced, which significantly improves the surface hydrophilicity of the nano-Fe3O4, so that the nano-Fe3O4 can be uniformly dispersed in the water-based polyurethane paint, and the coating has higher mechanical strength and tensile properties.

[0014] The multiple hydroxyl groups and carboxyl groups introduced on the surface of the nano-Fe3O4 form hydrogen bonds and other interactions with the hydroxyl groups and carboxyl groups on the surface of the graphene oxide, the interface interaction between the nano-Fe3O4 and the graphene oxide is improved, the impedance matching performance of the two is improved, the interface polarization effect is formed, the hybrid capacitance is formed at the interface, the dielectric relaxation behavior is generated, and therefore the absorption effect of the coating on electromagnetic waves is improved, the absorption frequency band is wide, and the wave-absorbing reflection loss is large.

[0015] The paint can be used as a topcoat in actual application, and can be combined with intermediate paint, primer and the like to prepare a three-layer or multi-layer composite coating layer. DETAILED DESCRIPTION

[0016] In order for those skilled in the art to better understand the technical solutions of the present application, the preferred embodiments of the present application are described below in combination with specific examples, but it is not to be understood as a limitation to the present application.

[0017] The solid content of the following aqueous polyurethane emulsion is 40%, model Guobang GG025, from Jining Sun Never Sets Biological Science and Technology Co., Ltd. The average particle size of the nano-magnetic iron oxide is 40 nm. The thickness of the graphene oxide is between 1-3 nm, and the length is between 3-5 μm.

[0018] Example 1:

[0019] (1) Add 10 mL of water, 2 g of ethylenediamine-N, N'-diacetic acid, and 2.64 g of glycidol to a flask, and after stirring, add 3.5 mL of an aqueous solution containing 1.36 g of sodium hydroxide dropwise, heat to 55°C, and stir for 10 h. Add hydrochloric acid with a mass fraction of 37% dropwise to adjust the pH to 3, and precipitate the crystals. After filtration and drying, the modifier is obtained.

[0020] (2) Add 2 L of water and 20 g of nano-magnetic iron oxide to a flask, and ultrasonic dispersion for 20 min. Add 0.6 g of the modifier, heat to 70°C, and stir for 3 h. After filtration and washing with water, the modified magnetic iron oxide is obtained after drying.

[0021] (3) Add 1 kg of aqueous polyurethane emulsion, 4 g of graphene oxide, and 3 g of modified magnetic iron oxide to a container, and stir for 40 min. Then add 6 g of defoaming agent DiGol AIREX 902W and 2 g of wetting agent Haimi Disponer W-19, and after stirring, the radar wave absorbing coating is obtained.

[0022] Example 2:

[0023] (1) Add 8 mL of water, 2 g of ethylenediamine-N, N'-diacetic acid, and 2.12 g of glycidol to a flask, and after stirring, add 4 mL of an aqueous solution containing 1.6 g of sodium hydroxide dropwise, heat to 70°C, and stir for 6 h. Add hydrochloric acid with a mass fraction of 20% dropwise to adjust the pH to 4, and precipitate the crystals. After filtration and drying, the modifier is obtained.

[0024] (2) Add 2.5 L of water and 20 g of nano-magnetic iron oxide to a flask, and ultrasonic dispersion for 20 min. Add 1 g of the modifier, heat to 60°C, and stir for 5 h. After filtration and washing with water, the modified magnetic iron oxide is obtained after drying.

[0025] (3) Add 1 kg of aqueous polyurethane emulsion, 8 g of graphene oxide, and 8 g of modified magnetic iron oxide to a container, and stir for 60 min. Then add 8 g of defoaming agent DiGol AIREX 902W and 3 g of wetting agent Haimi Disponer W-19, and after stirring, the radar wave absorbing coating is obtained.

[0026] Example 3:

[0027] (1) Add 3L water, 20g nano-magnetic iron oxide into a flask, ultrasonic dispersion for 30min, add 1.5g modifier (prepared according to the method of Example 1), heat to 85℃, stir for 2h, filter and wash with water, dry to obtain modified magnetic iron oxide.

[0028] (2) Add 1kg water-based polyurethane emulsion, 12g graphene oxide, 14g modified magnetic iron oxide into a container, stir and mix uniformly for 60min, then add 3g defoaming agent DiGol AIREX 902W, 5g wetting agent HENKEL Disponer W-19, stir to obtain radar wave absorbing coating.

[0029] Example 4:

[0030] (1) Add 3L water, 20g nano-magnetic iron oxide into a flask, ultrasonic dispersion for 30min, add 2g modifier (prepared according to the method of Example 1), heat to 80℃, stir for 3h, filter and wash with water, dry to obtain modified magnetic iron oxide.

[0031] (2) Add 1kg water-based polyurethane emulsion, 16g graphene oxide, 20g modified magnetic iron oxide into a container, stir and mix uniformly for 60min, then add 6g defoaming agent DiGol AIREX 902W, 2g wetting agent HENKEL Disponer W-19, stir to obtain radar wave absorbing coating.

[0032] Comparative Example 1:

[0033] (1) Add 1kg water-based polyurethane emulsion, 4g graphene oxide, 3g nano-magnetic iron oxide into a container, stir and mix uniformly for 40min, then add 6g defoaming agent DiGol AIREX 902W, 2g wetting agent HENKEL Disponer W-19, stir to obtain radar wave absorbing coating.

[0034] Comparative Example 2:

[0035] (1) Add 2L water, 20g nano-magnetic iron oxide into a flask, ultrasonic dispersion for 20min, add 0.6g pentaerythritol, heat to 70℃, stir for 3h, filter and wash with water, dry to obtain modified magnetic iron oxide.

[0036] (2) Add 1kg water-based polyurethane emulsion, 4g graphene oxide, 3g modified magnetic iron oxide into a container, stir and mix uniformly for 40min, then add 6g defoaming agent DiGol AIREX 902W, 2g wetting agent HENKEL Disponer W-19, stir to obtain radar wave absorbing coating.

[0037] Comparative Example 3:

[0038] (1) Add 2 L of water, 20 g of nano-magnetic iron oxide into a flask, ultrasonic dispersion for 20 min, add 0.6 g of citric acid, heat to 70℃, stir for 3 h, filter and wash with water, dry to obtain modified magnetic iron oxide.

[0039] (2) Add 1 kg of water-based polyurethane emulsion, 4 g of graphene oxide, 3 g of modified magnetic iron oxide into a container, stir and mix uniformly for 40 min, then add 6 g of defoaming agent Digo AIREX 902W, 2 g of wetting agent Hengmei Disponer W-19, stir to obtain radar wave absorbing coating.

[0040] Comparative Example 4:

[0041] (1) Add 2 L of water, 20 g of nano-magnetic iron oxide into a flask, ultrasonic dispersion for 20 min, add 0.6 g of tartaric acid, heat to 70℃, stir for 3 h, filter and wash with water, dry to obtain modified magnetic iron oxide.

[0042] (2) Add 1 kg of water-based polyurethane emulsion, 4 g of graphene oxide, 3 g of modified magnetic iron oxide into a container, stir and mix uniformly for 40 min, then add 6 g of defoaming agent Digo AIREX 902W, 2 g of wetting agent Hengmei Disponer W-19, stir to obtain radar wave absorbing coating.

[0043] The radar wave absorbing coating is coated on the surface of the tinplate, baked at 80℃ for 6 h to form a coating with a thickness of 2 mm and a surface density of 4 kg / m 2 The reflection loss and wave absorbing performance of the coating are tested by a vector network analyzer according to the standard GJB / 2038a-2011 by using the bow method, and the test frequency range is 2-18 GHz.

[0044] The tensile properties are tested according to the standard GB / T 528-2009.

[0045] Table 1 Wave absorbing performance of the coating

[0046]

[0047] Compared with Example 1, in Comparative Example 1, nano-magnetic iron oxide and graphene oxide are added into the polyurethane coating as composite wave absorbing agent. Due to the low interface performance and poor impedance matching of nano-magnetic iron oxide and graphene oxide, the frequency of the coating with a reflection loss of ≤-10 dB is only between 8.4-10.5 GHz, the absorption bandwidth is only 2.1 GHz, the maximum reflection loss is only-11.5 dB, and the wave absorbing performance is poor. The agglomeration problem of nano-magnetic iron oxide is serious, which affects the mechanical strength and tensile properties of the polyurethane coating, and the poor dispersibility also affects the wave absorbing performance of the coating.

[0048] The modifier of embodiments 1-4 contains multiple hydroxyl groups, which form strong coordination with iron ions on the surface of nanometer ferroferric oxide, thereby modifying the modifier on the surface of ferroferric oxide, which is beneficial to improve the dispersibility of nanometer ferroferric oxide particles, improve the agglomeration problem, and at the same time introduce multiple hydrophilic hydroxyl and carboxyl groups, which significantly improve the surface hydrophilicity of nanometer ferroferric oxide, uniformly disperse in the waterborne polyurethane coating, and make the coating have higher mechanical strength and tensile properties. The hydroxyl and carboxyl groups introduced on the surface of nanometer ferroferric oxide form hydrogen bonds and other interactions with the hydroxyl and carboxyl groups on the surface of graphene oxide, thereby improving the interfacial interaction between nanometer ferroferric oxide and graphene oxide, improving the impedance matching performance of the two, forming an interfacial polarization effect, forming a hybrid capacitor at the interface, and producing dielectric relaxation behavior, thereby improving the absorption effect of electromagnetic waves. The frequency of the reflection loss ≤-10 dB of example 4 is between 7.3-12.6 GHz, the absorption bandwidth reaches 5.3 GHz, the maximum reflection loss reaches-31.0 dB, and the wave absorption performance is the best. The maximum elongation at break of the coating of example 1 reaches 550.2%, and the maximum tensile strength of the coating of example 2 reaches 23.6 MPa.

[0049] The frequency of the reflection loss ≤-10 dB of example 1 is between 7.6-11.2 GHz, the absorption bandwidth reaches 3.6 GHz, the maximum reflection loss reaches-18.4 dB, the tensile strength is 17.4 MPa, and the elongation at break is 550.2%. Compared with example 1, comparative example 2 uses pentaerythritol to modify the surface of nanometer ferroferric oxide, does not introduce hydrophilic carboxyl groups, and the hydrophilicity of the modified ferroferric oxide is lower than that of example 1. The dispersibility in the waterborne polyurethane coating is poor, resulting in lower tensile properties of the coating, and lower interfacial interaction with graphene oxide, poor impedance matching performance, and poor wave absorption performance.

[0050] Compared with example 1, comparative examples 3 and 4 use citric acid and tartaric acid to modify the surface of nanometer ferroferric oxide, respectively. The hydroxyl content of citric acid and tartaric acid is lower than that of the modifier of example 1, and the coordination ability on the surface of nanometer ferroferric oxide is lower than that of example 1, resulting in poor modification effect on nanometer ferroferric oxide. The wave absorption performance and tensile properties of the coating are lower than those of example 1.

[0051] The above-described embodiments only express several embodiments of the present application, and the description is more specific and detailed, but it cannot be understood as limiting the scope of the patent. It should be noted that for ordinary skilled persons in the art, without departing from the concept of the present application, several modifications and improvements can be made, which are within the scope of protection of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.

Claims

1. A radar absorbing paint, characterized in that, The radar wave-absorbing coating comprises 100 parts by weight of water-based polyurethane emulsion, 0.4-1.6 parts by weight of graphene oxide, 0.3-2 parts by weight of modified ferroferric oxide, 0.3-0.8 parts by weight of defoaming agent, and 0.2-0.5 parts by weight of wetting agent. The modified ferroferric oxide is prepared by adding water and nano ferroferric oxide into a flask, adding a modifier after ultrasonic dispersion, filtering after stirring, washing with water, and drying to obtain the modified ferroferric oxide. The structural formula of the modifier is: ; The nano ferroferric oxide is used in an amount of 100 parts by weight, and the modifier is used in an amount of 3-10 parts by weight.

2. The radar wave absorbing paint according to claim 1, characterized by The temperature during stirring is 60-85℃, and the stirring time is 2-5h.

3. The radar absorbing paint of claim 1, wherein, The modified ferroferric oxide is prepared by adding water and nano ferroferric oxide into a flask, adding a modifier after ultrasonic dispersion, filtering after stirring, washing with water, and drying to obtain the modified ferroferric oxide.

4. The radar absorbing paint according to claim 3, characterized in that, The nano ferroferric oxide is used in an amount of 100 parts by weight, and the modifier is used in an amount of 3-10 parts by weight.

5. The radar absorbing paint of claim 3, wherein, The temperature during stirring is 60-85℃, and the stirring time is 2-5h.

6. The radar absorbing paint of claim 3, wherein, The modified ferroferric oxide is prepared by adding water and nano ferroferric oxide into a flask, adding a modifier after ultrasonic dispersion, filtering after stirring, washing with water, and drying to obtain the modified ferroferric oxide.

7. A method for the preparation of a radar absorbing paint according to any one of claims 1 to 6, characterized in that, The nano ferroferric oxide is used in an amount of 100 parts by weight, and the modifier is used in an amount of 3-10 parts by weight.

8. The method of claim 7, wherein the radar absorbing coating is prepared by a process comprising: The temperature during stirring is 60-85℃, and the stirring time is 2-5h. The modified ferroferric oxide is prepared by adding water and nano ferroferric oxide into a flask, adding a modifier after ultrasonic dispersion, filtering after stirring, washing with water, and drying to obtain the modified ferroferric oxide. The nano ferroferric oxide is used in an amount of 100 parts by weight, and the modifier is used in an amount of 3-10 parts by weight. The temperature during stirring is 60-85℃, and the stirring time is 2-5h.

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