Microcellular foaming intermediate infrared radiation coating as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of camouflage materials, and particularly relates to a microcellular foaming intermediate infrared radiation coating as well as a preparation method and application thereof. When the coating is prepared, the polyethylene resin is subjected to foaming treatment, so that a micro air chamber cavity is formed in the polyethylene resin, and incident infrared waves are reflected for multiple times when being transmitted in the microcellular foaming intermediate infrared stealth coating; specifically, by regulating and controlling the internal microstructure of the microcellular foaming mid-infrared stealth coating, multiple reflections on infrared radiation are completed during use, and the comprehensive infrared reflectivity of the microcellular foaming mid-infrared stealth coating is improved, so that the mid-infrared radiation function is realized; the microcellular foaming mid-infrared stealth coating prepared by the preparation method disclosed by the invention is subjected to an infrared emissivity test according to a GJB 5023.2-2003 standard, and the normal-temperature infrared emissivity is less than or equal to 0.80 under the wave band of 8-14 microns; an adhesive force test shows that the adhesive force reaches grade 2, and the adhesive force performance of the base material is good.

Description

Technical Field

[0001] The present invention belongs to the technical field of camouflage materials, and particularly relates to a microporous foamed mid-infrared radiation coating, a preparation method thereof, and an application thereof. Background Art

[0002] Infrared thermal imaging reconnaissance relies on the radiation intensity difference between the target and the background in the infrared band to complete target recognition and tracking, while infrared stealth aims to change the radiation intensity of the target, so that the infrared radiation brightness of the target and the background remains synchronized for a long time, making it difficult for the target to be detected and recognized by the infrared thermal imaging reconnaissance system. Due to its low infrared emissivity performance, infrared stealth materials can be coated on the surface of equipment to reduce the infrared radiation of the equipment, thereby achieving the infrared stealth of the equipment.

[0003] Previously, the research on low-infrared emissivity camouflage materials mainly focused on improving the infrared reflectivity of the material surface, mainly screening and modifying the material itself, and most of the research objects were metal materials. However, due to the limitations of its own structure and physical properties, it is difficult to find a coating stealth material that combines camouflage stealth and engineering applications. At present, the low-emissivity fillers used in infrared stealth materials are mainly doped with aluminum / silver powder in the coating. These materials have unstable infrared stealth performance, are prone to surface oxidation, and turn into high-emissivity materials. Moreover, they have strong thermal conductivity and generally poor heat insulation performance, and cannot meet the technical requirements of compatible radar wave absorption performance.

[0004] Therefore, it is urgent to study a new low-infrared emissivity camouflage coating to solve the problems existing in the existing low-infrared emissivity camouflage coating. Summary of the Invention

[0005] The purpose of the present invention is to overcome the above-mentioned disadvantages of the existing technology and provide a microporous foamed mid-infrared radiation coating, a preparation method thereof, and an application thereof.

[0006] To achieve the above purpose, the present invention provides the following technical solutions:

[0007] On the one hand, the present invention provides a microporous foamed mid-infrared radiation coating, which comprises the following components by weight: 18-20 parts of a foaming agent, 81-85 parts of a polyethylene resin, and 4-6 parts of a curing agent.

[0008] Specifically, the foaming agent is azodicarbonamide, the polyethylene resin is a high-density polyethylene resin or a linear low-density polyethylene resin, and the curing agent is a silane coupling agent or an aluminate coupling agent.

[0009] Specifically, the high-density polyethylene resin is a thermoplastic resin with high crystallinity and non-polarity, which is polymerized from ethylene under specific conditions and the action of a catalyst;

[0010] The linear low density polyethylene resin is obtained by gas phase fluidized bed polymerization of ethylene as the main raw material and a small amount of α-olefins (such as 1-butene, 1-hexene or 1-octene) as comonomers under high pressure or low pressure in the presence of a catalyst;

[0011] The silane coupling agent is a class of organosilicon compounds containing two different chemically active groups in the molecule, and is used to improve the bonding strength between plastic products, rubber products, etc. and glass fibers, inorganic fillers;

[0012] The aluminate coupling agent is an auxiliary agent commonly used for surface modification of inorganic fillers.

[0013] Specifically, the blowing agent is azodicarbonamide particles with a size less than or equal to 5 μm, the solid content of the polyethylene resin is 48-52%; the solid content of the curing agent is 39-41%;

[0014] To control the cell size in the coating, the blowing agent is selected as azodicarbonamide particles with a size less than or equal to 5 μm. The reason is that when the particle size of the blowing agent is small, more nucleation points can be generated. When generating gas, more dispersed gas release sources will be formed in the coating, so that a large number of fine air bubbles will be formed inside the coating, and they will be uniformly merged during the growth process to form dense and uniformly sized air bubbles; when the particle size of the blowing agent is large, relatively fewer nucleation points are generated, and the gas is released from fewer positions during the foaming process, resulting in uneven size distribution of the formed air bubbles, which in turn affects the microporous structure inside the coating, and thus the mid-infrared radiation effect cannot be achieved.

[0015] On the other hand, the present invention provides a preparation method of a microporous foamed mid-infrared radiation coating as described above. The specific method is as follows:

[0016] Step 1, surface pretreatment of the substrate: The surface of the substrate is cleaned with anhydrous ethanol to remove the attachments on the surface of the substrate;

[0017] Step 2, preparation of the coating: Weigh the blowing agent, polyethylene resin and curing agent according to the set weight parts, mix them and then disperse them, and add a specific amount of diluent to make the mixed coating reach the preset viscosity. The preset viscosity is 39-43S, the diluent is xylene, and a homogenizing disperser is used for dispersion, with a rotation speed of 1250-1750 r / min and a duration of 9-11 min;

[0018] Furthermore, the viscosity of the coating needs to be adjusted to an appropriate range because: when the viscosity is too high, it is likely to cause difficulties in spray atomization, that is, the droplets generated during spraying are relatively large, and thus it is easy to form orange peel patterns, excessive thickness, and too fast drying speed on the surface of the substrate during spraying; when the viscosity is too low, it is likely to cause a decrease in the solid content of the coating, thereby reducing the covering power of the coating, and it is easy to form sagging and slow drying speed, etc.

[0019] Step 3: Coating preparation: Spray the coating on the surface of the substrate by using air spraying technology. The relevant process parameters are as follows: the air pressure is 0.4 - 0.6 MPa, the spraying distance is 15 - 25 cm, the moving speed of the spray gun is 20 - 40 cm / s, and spray 3 - 5 times.

[0020] When the coating is atomized by compressed air, it can be evenly dispersed on the surface of the substrate and can cover a large area in a short time; moreover, the coating quality of the air spraying process is better. The highly atomized coating can form a uniform and smooth paint film coating on the surface of the substrate, and can effectively reduce coating defects such as sagging and orange peel under good parameter settings, thereby improving the coating appearance.

[0021] Step 4: Coating curing: First, air-dry the sprayed substrate at 20 - 30 °C for 28 - 32 min; then put it into an oven. The temperature in the oven rises from room temperature to 145 - 155 °C in 25 - 35 min, with a heating rate of 3.4 - 5.2 °C / min, and keep it warm for 55 - 65 min; then rise to 245 - 255 °C in 25 - 35 min, with a heating rate of 2.9 - 4.0 °C / min, and keep it warm for 55 - 65 min. Finally, cool to room temperature with the oven.

[0022] It should be noted here that since the decomposition temperature of the foaming agent (azodicarbonamide) is 190 - 220 °C, and the crosslinking and curing temperature of the polyethylene resin is 170 - 200 °C, in order to avoid the pore aggregation caused by too low coating strength after foaming, the coating needs to be pre-cured at a temperature slightly lower than the crosslinking and curing temperature (i.e., 145 - 155 °C). After the coating has a certain strength, then rise the temperature to 245 - 255 °C and keep it warm for 55 - 65 min. Furthermore, while the coating is fully cured, the foaming agent is fully decomposed to generate a uniform and denser microporous structure.

[0023] It is supplementary to note that there is no sequential order between Step 1 and Step 2 in this preparation method. In principle, as long as the surface pretreatment of the substrate and the preparation of the coating are completed before the coating is prepared.

[0024] The present invention uses a single material with a pore structure to replace metal as the filler of the infrared stealth coating. That is, for the infrared stealth coating, without adding low-emissivity fillers, the comprehensive infrared wave reflectivity is improved by changing the internal structure.

[0025] On the other hand, the present invention provides a microcellular foamed mid-infrared radiation coating, or the application of a microcellular foamed mid-infrared radiation coating prepared by a preparation method of the microcellular foamed mid-infrared radiation coating in infrared camouflage and infrared stealth.

[0026] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects:

[0027] (1) When preparing this coating, the polyethylene resin is foamed to form micro-air chamber cavities inside the polyethylene resin, so that the incident infrared waves are reflected multiple times when transmitting inside the microcellular foamed mid-infrared stealth coating; specifically, by regulating the microstructure inside the microcellular foamed mid-infrared stealth coating, multiple reflections of infrared radiation can be completed during use, improving the comprehensive infrared reflectivity of the microcellular foamed mid-infrared stealth coating, thereby realizing the mid-infrared radiation function; the microcellular foamed mid-infrared stealth coating prepared by the present invention is tested for infrared emissivity according to the standard of GJB 5023.2-2003, and the normal-temperature infrared emissivity is less than or equal to 0.8 in the wavelength range of 8μm to 14μm; when the adhesion is tested according to the standard of GB / T 1720-1989, the adhesion reaches level 2, and the adhesion performance of the substrate is good.

[0028] (2) The present invention uses a silane coupling agent or an aluminate coupling agent to crosslink and cure the polyethylene resin. Since the silane coupling agent or the aluminate coupling agent molecule contains organic reactive groups, and these organic reactive groups can react with the active sites on the molecular chain of the polyethylene resin, during the heating and curing process, the organic reactive groups and the polyethylene resin undergo a chemical reaction, so that the silane coupling agent or the aluminate coupling agent forms a crosslinked structure between the polyethylene resin and the surface of the inorganic material, thereby improving the adhesion of the coating.

[0029] (3) The air spraying process adopted in the preparation method of the present invention has the advantage of strong adaptability. Whether facing flat plates or curved workpieces with complex structures, as long as the spray gun angle is flexibly adjusted, the coating can be successfully completed, and it can adapt to the painting of the surfaces of various shaped objects. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The drawings here are incorporated into the specification and form a part of this specification, and are used together with the specification to explain the principles of the present invention.

[0031] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, for those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0032] Figure 1 This is a flowchart of the preparation method of the microcellular foaming mid-infrared radiation coating of the present invention. Specific embodiments

[0033] Here, the exemplary embodiments will be described in detail, and the examples are shown in the drawings. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. On the contrary, they are merely examples consistent with some aspects of the present invention detailed in the appended claims.

[0034] In order to enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described in detail below with reference to the drawings and embodiments.

[0035] Now, prepare the coating according to the components of each raw material in Table 1 below, specifically as follows:

[0036] Table 1

[0037]

[0038] Example 1

[0039] See Figure 1 As shown, this example provides a preparation method of a microcellular foaming mid-infrared radiation coating, and the specific method is as follows:

[0040] Step 1. Substrate surface pretreatment: Wipe the surface of the substrate with a non-woven fabric dipped in anhydrous ethanol to remove the excess attachments on the substrate surface;

[0041] Step 2. Coating preparation: Weigh 18 parts of azodicarbonamide, 81 parts of high-density polyethylene resin, and 4 parts of silane coupling agent by weight, mix them and disperse them, and gradually add xylene to make the viscosity of the mixed coating 39 - 40S; Disperse with a homogenizing disperser, the rotation speed during dispersion is 1250r / min, and the duration is 11min; The particle size of the azodicarbonamide is 5μm, the solid content of the high-density polyethylene resin is 48%, and the solid content of the silane coupling agent is 39%;

[0042] Step 3. Coating preparation: Spray the coating on the surface of the substrate by air spraying technology, and the relevant process parameters are as follows: The air pressure is 0.4MPa, the spraying distance is 15cm, the moving speed of the spray gun is 20cm / s, and spray 3 times;

[0043] Step 4, Coating Curing: First, air-dry the sprayed substrate at 20 - 30°C for 32 minutes; then place it in an oven. The temperature in the oven rises from room temperature to 145°C in 35 minutes at a heating rate of 3.4°C / min, and keep the temperature for 65 minutes; then rise to 245°C in 28 minutes at a heating rate of 3.6°C / min, and keep the temperature for 65 minutes; finally, let it cool to room temperature with the oven to obtain the microcellular foamed mid-infrared radiation coating A.

[0044] Example 2

[0045] See Figure 1 As shown, this example provides a method for preparing a microcellular foamed mid-infrared radiation coating. The specific method is as follows:

[0046] Step 1, Substrate Surface Pretreatment: Wipe the substrate surface with a non-woven fabric dipped in anhydrous ethanol to remove excess attachments on the substrate surface;

[0047] Step 2, Coating Preparation: Weigh 19 parts of azodicarbonamide, 83 parts of high-density polyethylene resin, and 5 parts of silane coupling agent by weight, mix them and disperse, and gradually add xylene to make the viscosity of the mixed coating 40 - 41 S; use a homogenizing disperser for dispersion, with a rotation speed of 1550 r / min and a duration of 10 minutes during dispersion; the particle size of azodicarbonamide is less than 4 μm, the solid content of high-density polyethylene resin is 50%, and the solid content of silane coupling agent is 41%;

[0048] Step 3, Coating Preparation: Spray the coating on the substrate surface using air spraying technology. The relevant process parameters are as follows: air pressure is 0.5 MPa, spraying distance is 18 cm, the moving speed of the spray gun is 28 cm / s, and spray 5 times;

[0049] Step 4, Coating Curing: First, air-dry the sprayed substrate at 20 - 30°C for 29 minutes; then place it in an oven. The temperature in the oven rises from room temperature to 152°C in 28 minutes at a heating rate of 4.5°C / min, and keep the temperature for 60 minutes; then rise to 252°C in 30 minutes at a heating rate of 3.3°C / min, and keep the temperature for 62 minutes; finally, let it cool to room temperature with the oven to obtain the microcellular foamed mid-infrared radiation coating B.

[0050] Example 3

[0051] See Figure 1 As shown, this example provides a method for preparing a microcellular foamed mid-infrared radiation coating. The specific method is as follows:

[0052] Step 1, Substrate Surface Pretreatment: Wipe the substrate surface with a non-woven fabric dipped in anhydrous ethanol to remove excess attachments on the substrate surface;

[0053] Step 2, Coating Preparation: Weigh 20 parts of azodicarbonamide, 85 parts of high-density polyethylene resin, and 6 parts of silane coupling agent by weight. After mixing, disperse them and gradually add xylene to make the viscosity of the mixed coating 41 - 43 S. Use a homogenizing disperser for dispersion, with a rotation speed of 1500 r / min and a duration of 9 min during dispersion. The particle size of the azodicarbonamide is less than 3 μm, the solid content of the high-density polyethylene resin is 51%, and the solid content of the silane coupling agent is 39%.

[0054] Step 3, Coating Application: Spray the coating on the surface of the substrate using air spraying technology. The relevant process parameters are as follows: air pressure is 0.6 MPa, spraying distance is 22 cm, the moving speed of the spray gun is 34 cm / s, and spray 4 times.

[0055] Step 4, Coating Curing: First, air-dry the sprayed substrate at 20 - 30 °C for 28 min. Then put it into an oven. The temperature in the oven rises from room temperature to 148 °C in 25 min, with a heating rate of 4.9 °C / min, and keep it warm for 58 min. Then, it rises to 248 °C in 32 min, with a heating rate of 3.1 °C / min, and keep it warm for 58 min. Finally, cool it to room temperature with the oven to obtain the microporous foamed mid-infrared radiation coating C.

[0056] Example 4

[0057] See Figure 1 As shown, this example provides a method for preparing a microporous foamed mid-infrared radiation coating. The specific method is as follows:

[0058] Step 1, Substrate Surface Pretreatment: Wipe the surface of the substrate with a non-woven fabric dipped in anhydrous ethanol to remove excess attachments on the substrate surface.

[0059] Step 2, Coating Preparation: Weigh 20 parts of azodicarbonamide, 85 parts of linear low-density polyethylene resin, and 6 parts of aluminate coupling agent by weight. After mixing, disperse them and add a certain amount of xylene solution to make the viscosity of the mixed coating 39 - 41 S. Use a homogenizing disperser for dispersion, with a rotation speed of 1750 r / min and a duration of 9 min during dispersion. The relevant process parameters are as follows: the particle size of the azodicarbonamide is less than 4 μm, the solid content of the linear low-density polyethylene resin is 52%, and the solid content of the aluminate coupling agent is 40%.

[0060] Step 3, Coating Application: Spray the coating on the surface of the substrate using air spraying technology. The relevant process parameters are as follows: air pressure is 0.5 MPa, spraying distance is 25 cm, the moving speed of the spray gun is 40 cm / s, and spray 5 times.

[0061] Step 4. Coating curing: First, air-dry the sprayed substrate at 20 - 30°C for 30 min, and then put it into an oven. The temperature in the oven is raised from room temperature to 155°C in 32 min at a heating rate of 4.1°C / min, and kept at this temperature for 55 min. Then, it is heated to 255°C in 26 min at a heating rate of 3.8°C / min and kept at this temperature for 55 min. Finally, it is cooled to room temperature with the oven to obtain the microcellular foamed mid-infrared radiation coating D.

[0062] Comparative Example 1

[0063] This comparative example provides a method for preparing a microcellular foamed mid-infrared radiation coating, and the specific method is as follows:

[0064] Step 1. Substrate surface pretreatment: Wipe the surface of the substrate with a non-woven fabric dipped in anhydrous ethanol to remove the excess attachments on the substrate surface;

[0065] Step 2. Coating preparation: Weigh 15 parts of azodicarbonamide, 95 parts of high-density polyethylene resin, and 3 parts of silane coupling agent by weight, mix them and disperse, and gradually add xylene to make the viscosity of the mixed coating 40S; Disperse with a homogenizing disperser at a rotation speed of 1500 r / min for 10 min; The particle size of the azodicarbonamide is less than 4 μm, the solid content of the high-density polyethylene resin is 50%, and the solid content of the silane coupling agent is 39%;

[0066] Step 3. Coating preparation: Spray the coating on the surface of the substrate by air spraying technology, and the relevant process parameters are as follows: air pressure is 0.5 MPa, spraying distance is 20 cm, the moving speed of the spray gun is 25 cm / s, and spray 5 times;

[0067] Step 4. Coating curing: First, air-dry the sprayed substrate at 20 - 30°C for 30 min; Then put it into an oven, the temperature in the oven is raised from room temperature to 150°C in 30 min at a heating rate of 4.2°C / min, and kept at this temperature for 60 min; Then it is heated to 250°C in 30 min at a heating rate of 3.3°C / min and kept at this temperature for 60 min; Finally, it is cooled to room temperature with the oven to obtain the microcellular foamed mid-infrared radiation coating E.

[0068] It should be supplemented and explained that: The substrates used in the above Examples 1 - 4 and Comparative Example 1 are all alumina ceramic sheet substrates, and the substrate size is 40 mm (length) × 40 mm (width) × 1 mm (thickness).

[0069] To further verify the effectiveness of the technical solutions provided by the present invention, the above coatings A, B, C, D, and E are respectively tested as follows:

[0070] (1) Use a digital micrometer to test the thickness of the coating.

[0071] (2) The adhesion performance of the coating is tested by using a film scribing tester in accordance with the standard of GB / T 1720-1989;

[0072] (3) The normal temperature infrared emissivity of the coating in the 8 μm - 14 μm band is tested by using a handheld infrared emissivity measuring instrument in accordance with the standard of GJB 5023.2-2003. The test results are shown in Table 2.

[0073] Table 2

[0074]

[0075] In summary, as can be seen from the test results in Table 2, the adhesion performance of the microcellular foamed mid-infrared radiation coatings prepared in the above embodiments all reaches level 2, and the infrared emissivities are all ≤ 0.8, all having excellent adhesion performance and mid-infrared radiation performance; in the comparative examples, the content of high-density polyethylene resin is relatively high and the content of the foaming agent is relatively high, resulting in relatively low cell size and density, so that the infrared emissivity is on the high side and cannot meet the application requirements in infrared camouflage and infrared stealth. Therefore, the performances of the microcellular foamed mid-infrared radiation coatings prepared by the preparation method of the present invention all meet the design requirements.

[0076] The above are only specific embodiments of the present invention, enabling those skilled in the art to understand or implement the present invention. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention.

[0077] It should be understood that the present invention is not limited to the content already described above, and various modifications and changes can be made without departing from its scope. The scope of the present invention is only limited by the appended claims.

Claims

1. A microporous foamed mid-infrared radiation coating, characterized in that: The composition comprises the following components by weight: 18 to 20 parts of a foaming agent, 81 to 85 parts of a polyethylene resin and 4 to 6 parts of a curing agent.

2. The microporous foamed mid-infrared radiation coating according to claim 1, characterized in that: The foaming agent is azodicarbonamide, the polyethylene resin is a high-density polyethylene resin or a linear low-density polyethylene resin, and the curing agent is a silane coupling agent or an aluminate coupling agent.

3. The microporous foamed mid-infrared radiation coating according to claim 1, characterized in that: The particle size of the foaming agent is less than or equal to 5 μm, the solid content of the polyethylene resin is 48-52%, and the solid content of the curing agent is 39-41%.

4. The method for preparing the microporous foamed mid-infrared radiation coating according to any one of claims 1 to 3, characterized in that: The specific steps are as follows: Step 1: pretreatment of substrate surface; Step 2, coating preparation: weighing the foaming agent, polyethylene resin and curing agent according to the set weight parts, dispersing after mixing, and adding a specific amount of diluent to make the coating reach a preset viscosity; Step 3, coating preparation: spraying the coating on the surface of the substrate; Step 4: Coating curing: curing the sprayed substrate to obtain a microporous foamed mid-infrared radiation coating.

5. The preparation method according to claim 4, characterized in that: In step 1, anhydrous ethanol is used to clean the surface of the substrate to remove the attached matter on the surface of the substrate.

6. The preparation method according to claim 4, characterized in that: In step 2, the preset viscosity is 39-43S.

7. The preparation method according to claim 4, characterized in that: In step 2, a homogenizer is used for dispersion, with a rotation speed of 1250 to 1750 r / min and a duration of 9 to 11 min.

8. The preparation method according to claim 4, characterized in that: In step 3, the spraying adopts air spraying technology, and the relevant process parameters are as follows: air pressure is 0.4-0.6MPa, spraying distance is 15-25cm, spray gun moving speed is 20-40cm / s, and spraying is 3-5 times.

9. The preparation method according to claim 4, characterized in that: Step 4 is specifically as follows: first, air-dry the sprayed substrate at 20-30°C for 28-32 minutes; then place it in a drying device, which heats the substrate from room temperature to 145-155°C over 25-35 minutes and keeps it warm for 55-65 minutes; then heats the substrate to 245-255°C over 25-35 minutes and keeps it warm for 55-65 minutes; and finally cools it to room temperature with the drying device.

10. Use of the microporous foamed mid-infrared radiation coating according to any one of claims 1 to 3, or the microporous foamed mid-infrared radiation coating prepared by the preparation method according to any one of claims 4 to 9 in infrared camouflage and infrared stealth.

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