Multi-band imitated vegetation composite camouflage material based on multiple cooling modes and preparation method thereof

Abstract

The application discloses a multi-waveband imitated vegetation composite camouflage material based on a multiple cooling mode and a preparation method thereof. The material comprises a high-hygroscopic camouflage base material, a high-reflective filler, phase change microcapsules and an additive. The high-hygroscopic camouflage base material not only serves as a matrix of various fillers and simulates the transpiration cooling effect of plants, but also, in combination with green pigments, can form a similar reflection spectrum to green plants; the high-reflective filler improves the reflectivity of the camouflage material in the visible light-near infrared-mid-infrared waveband, thereby realizing a radiation cooling effect; and the phase change microcapsules have a relatively high phase change enthalpy at normal temperature, thereby further reducing the overall temperature difference between the material and the environment background. The composite camouflage material is highly similar to green plants in the solar spectrum waveband, has a high correlation coefficient of 0.9778, can realize the same color and the same spectrum, and has a relatively low radiation temperature characteristic in the mid-infrared waveband. The camouflage material is expected to realize multi-waveband compatible camouflage in a vegetation background.

Description

Technical Field

[0001] This invention belongs to the field of multi-band camouflage material technology, specifically relating to a visible-near-infrared-mid-infrared multi-band vegetation-simulating composite camouflage material based on multiple cooling methods and its preparation method. Background Technology

[0002] In recent years, hyperspectral detection technology has evolved from unit structures to array structures, and from single-field-of-view to variable-field-of-view. Combined with satellite remote sensing systems for target identification, it has significantly improved sensitivity, accuracy, precision, detection range, and convenience. Traditional single-band camouflage techniques are insufficient to meet current target protection requirements. Hyperspectral detection covers the visible, near-infrared, and mid-infrared bands. In the visible and near-infrared bands, hyperspectral detection distinguishes targets from the background by analyzing the reflected solar energy. In the mid-infrared band, targets are primarily identified through the object's thermal radiation characteristics. Green vegetation serves as a common background environment for ground-based camouflage targets, making biomimetic vegetation camouflage materials a key research focus in the camouflage field. To achieve camouflage across multiple spectral bands, the visible light band requires uniform color, the near-infrared band requires spectral similarity to green vegetation, and the mid-infrared band requires low temperature radiation characteristics and infrared emissivity.

[0003] For example, Chinese patent CN114322663B discloses a visible-infrared compatible multi-band camouflage system and a multi-band camouflage vehicle. This system achieves multi-band camouflage by collecting and storing environmental information such as surrounding images and temperature, and adjusting image processing and temperature processing modules via a main controller. However, due to advancements in hyperspectral detection accuracy, display screen modules are easily detected. Another example is Chinese patent CN112457766A, which discloses a multi-band camouflage heat-insulating and cooling coating that only has high reflectivity in the visible-near-infrared range, rather than achieving uniform color and spectrum. Using heat insulation and cooling methods cannot fundamentally solve the temperature difference with the environmental background; this heat should be stored or dissipated strategically. A third example is CN114705082A, which discloses a 3D aerogel-based phase change composite material with both infrared stealth and visible light camouflage functions. The surface temperature should be close to the target temperature; temperatures that are too high or too low will easily be detected by detectors (an 8°C temperature difference is too large). Furthermore, the color-changing ink used in the MGPT composite material must not only be detectable by the naked eye but also have a spectrum consistent with green vegetation to cope with hyperspectral detection.

[0004] Currently, there is a lot of research on single-band camouflage materials, while multi-band camouflage is more in line with the current development needs of the camouflage field. In order to improve the survivability of weapons and equipment and other targets and achieve low detectability of camouflage technology, the development of camouflage materials with visible light, near-infrared and mid-infrared multi-bands is of great value and significance for the protection of weapons and equipment. Summary of the Invention

[0005] To improve the camouflage band range, the present invention aims to provide a multi-band (visible-near-infrared-mid-infrared) vegetation-simulating composite camouflage material based on multiple cooling methods and its preparation method. This vegetation-simulating composite camouflage material uses a hygroscopic polymer and highly hygroscopic inorganic material as the substrate to simulate the transpiration cooling effect of plants. Then, colorants simulate the reflectivity trend of green vegetation, and titanium dioxide in the high-reflectivity filler increases the reflectivity in the visible-near-infrared band, enabling the camouflage material to achieve the same color and spectrum as green plants in this band. Aluminum powder in the high-reflectivity filler increases the reflectivity in the mid-infrared band and reduces the emissivity of the camouflage material. Phase change microcapsules absorb heat with high phase change enthalpy to regulate infrared radiation characteristics. Additives not only make PAAS easier to disperse but also ensure uniform film texture during the drying and casting process, preventing excessive aluminum powder sedimentation, while also providing stronger weather resistance and enhancing outdoor practicality. The camouflage material is the same color and spectrum as plant leaves, has an infrared emissivity lower than that of green plants, and a radiation temperature characteristic similar to that of plant backgrounds, achieving optical camouflage and infrared radiation feature camouflage with the same color and spectrum in the visible light-near infrared-mid infrared bands.

[0006] The technical solution adopted by this invention to solve its technical problem is as follows:

[0007] A multi-band vegetation-simulating composite camouflage material based on multiple cooling methods comprises, by weight parts: 300-600 parts of highly hygroscopic camouflage substrate, 10-30 parts of high-reflectivity filler, 10-30 parts of phase change microcapsules, and 5-20 parts of additives; the highly hygroscopic camouflage substrate is composed of hygroscopic inorganic substances, hygroscopic polymers sodium polyacrylate and polyvinyl alcohol, and colorants; the high-reflectivity filler includes metallic pigments and high-reflectivity materials in the visible-near-infrared band.

[0008] Furthermore, the highly hygroscopic camouflage substrate is composed of 1-50 parts of hygroscopic inorganic material, 100-300 parts of sodium polyacrylate, 100-300 parts of polyvinyl alcohol, and 1-50 parts of colorant.

[0009] The phase change microcapsules used in this invention are microcapsules with polymethyl methacrylate (PMMA) as the shell material and eicosane as the core. Preferably, any one or more alkanes with different melting points can be selected as the core material according to different environmental temperature requirements.

[0010] The colorant used in this invention is any one or more of the following: chrome green, phthalocyanine, chlorophyll and its derivatives, which have a similar color to leaves.

[0011] The metallic pigment in the high-reflectivity filler used in this invention is any one or more of high-reflectivity materials such as aluminum powder, copper powder, and silver powder; the visible-near-infrared high-reflectivity material in the high-reflectivity filler is one or more of titanium dioxide, zinc oxide, or microcapsules with high reflectivity.

[0012] Furthermore, the mass ratio of the visible-near-infrared high reflectivity material to the metallic pigment in the high reflectivity filler is 1:0.5 to 1.

[0013] The additive is fumed silica, and either hydrophilic or hydrophobic types can be selected according to the actual situation.

[0014] This invention also provides a method for preparing the above-mentioned multi-band vegetation-simulating composite camouflage material based on multiple cooling methods, comprising the following steps:

[0015] (1) Preparation of highly hygroscopic camouflage substrate: Hygroscopic inorganic material and highly reflective material in the visible-near infrared band are added to deionized water and stirred evenly; polyvinyl alcohol (PVA) is added and stirred continuously at 200-400 rpm for 1-3 hours at a heating temperature of 80-95℃ to obtain a PVA mixed solution; pigments and additives are added to deionized water and ultrasonically vibrated and stirred to disperse evenly to obtain a suspension; sodium polyacrylate (PAAS) is evenly dispersed in anhydrous ethanol to obtain a PAAS-ethanol mixed solution; the PAAS-ethanol mixed solution is quickly added to the suspension and stirred continuously at 300-600 rpm for 1-2 hours at a heating temperature of 60-80℃ to obtain a PAAS mixed solution; the PVA mixed solution is added to the PAAS mixed solution and stirred continuously at room temperature for 1-2 hours to obtain a highly hygroscopic camouflage substrate;

[0016] (2) Preparation of phase change microcapsules: Weigh eicosane and dissolve it in polymethyl methacrylate (PMMA) solution; add emulsifier and distilled water dropwise, set the heating temperature to 20-50℃, the rotation speed to 800-3000 rpm, emulsify for 10-30 min, add hydrochloric acid to adjust the pH value to 3-5, set the temperature to 20-50℃, keep the reaction at this temperature for 1-12 h, after the reaction is completed, wash, filter, and vacuum dry to obtain phase change microcapsules;

[0017] (3) Add the metallic pigment and phase change microcapsules to the highly hygroscopic camouflage substrate prepared in step (1) in sequence, stir at room temperature for 1 to 2 hours; vacuum and let stand to remove bubbles; pour into a mold and dry at 30°C to obtain a multi-band composite camouflage material with multiple cooling modes.

[0018] Furthermore, the mass concentration of the hydrophilic fumed silica solution in step (1) is 0.1wt% to 1wt%. The viscosity of the PAAS solution is too high. Using hydrophilic fumed silica can make the PAAS easier to disperse. Pre-dispersing powdered chromium green and titanium dioxide uniformly in water before preparing the PAAS solution can ensure that it is uniformly dispersed and stable.

[0019] Further, in step (2), the concentration of the emulsifier Tween 20 solution is 1wt% to 10wt%, the solvent of the PMMA solution is xylene with a concentration of 0.01 to 0.2 g / ml, and the mass ratio of eicosane core to PMMA shell is 5:2.

[0020] Compared with the prior art, the beneficial effects of the present invention are:

[0021] (1) This invention broadens the scope of the camouflage field and can simultaneously meet the camouflage requirements of multiple bands such as visible light, near infrared and mid-infrared.

[0022] (2) This invention uses a combination of hygroscopic inorganic materials and hygroscopic polymers to adsorb moisture from the surrounding environment, allowing the moisture to evaporate continuously and achieving an evaporative cooling effect. The high-reflectivity filler reflects solar thermal radiation and mid-infrared energy radiation, achieving a radiative cooling effect; the phase change microcapsules have a high phase change enthalpy and can absorb a large amount of latent heat, achieving a phase change endothermic cooling effect; that is, the combined use of traditional evaporative cooling, low-radiative cooling, and phase change endothermic cooling works together to reduce the temperature of the camouflage material.

[0023] (3) The present invention uses a combination of highly absorbent composite substrate and various camouflage fillers to achieve the same color and spectrum as green plants in the visible light and near-infrared bands, and has similar characteristics to green plants such as "green peak", "red edge", "near-infrared plateau" and "water absorption valley"; and has a lower infrared emissivity and radiation temperature characteristics in the mid-infrared band.

[0024] (4) The present invention is simple to prepare and low in cost. Moreover, by changing the combination of different camouflage fillers, the camouflage effect required under different environmental backgrounds can be achieved. Attached image description:

[0025] Figure 1 A flowchart illustrating the preparation method of multi-band vegetation camouflage material with multiple cooling methods;

[0026] Figure 2 SEM image of phase change microcapsules;

[0027] Figure 3 The reflectance of leaves of plants such as osmanthus, bamboo, pomelo, and cherry trees under the solar spectrum.

[0028] Figure 4 The reflectance of the camouflage materials in Examples 1, 2, 3, and 4 in the solar spectral band;

[0029] Figure 5 Infrared camouflage thermal images of examples 1, 2, 3, and 4 placed on osmanthus trees;

[0030] Figure 6The temperature difference between the leaves of Osmanthus fragrans in the natural environment is shown in Examples 1, 2, 3, and 4. Detailed Implementation

[0031] The present invention will be further described in conjunction with the embodiments and accompanying drawings:

[0032] The flowchart of the preparation method of multi-band vegetation camouflage material based on multiple cooling methods is shown below. Figure 1 .

[0033] Example 1

[0034] Weigh 40 parts of PMMA and dissolve them in 20 ml of xylene, stirring thoroughly at 50°C. Then weigh 100 parts of eicosane and dissolve them in the same solution to form a homogeneous oil phase. Measure 10 parts of Tween 20 and 30 ml of distilled water, mix thoroughly, and slowly add the oil phase solution dropwise. Cool the mixture to 25°C and rotate at 1500 rpm. After emulsifying for 30 minutes, reduce the rotation speed to 500 rpm. Add hydrochloric acid to adjust the pH to 3, set the temperature to 30°C, and maintain the reaction temperature for 12 hours. After the reaction is complete, wash three times, filter, and vacuum dry to obtain phase change microcapsules.

[0035] Weigh 270 parts of PAAS and premix and disperse them using 540 parts of anhydrous ethanol; weigh 8 parts of hydrophilic fumed silica and 30 parts of chrome green, add them to 150 ml of deionized water, and perform ultrasonic vibration and mechanical stirring for 10 min to obtain a suspension; quickly add the pre-dispersed PAAS to the suspension, increase the rotation speed to 560 rpm, set the heating temperature to 50℃, and continue stirring for two hours to obtain a PAAS mixture.

[0036] Weigh 30 parts of anhydrous lithium chloride and 10 parts of titanium dioxide and add them to 50 ml of deionized water; weigh 180 parts of PVA (make the mass ratio of PAAS to PVA 3:2) and add them to the lithium chloride-titanium dioxide solution. Set the heating temperature to 92℃ and the rotation speed to 180 rpm, and stir continuously for two hours to obtain a PVA mixture.

[0037] The PAAS mixture and PVA mixture were stirred evenly at room temperature. After stirring for 0.5 hours at room temperature, 6 parts of floating aluminum powder and 10 parts of phase change microcapsules were added, and stirring was continued for 1 hour. The mixture was poured into a petri dish, vacuumed, and allowed to stand to remove bubbles. It was then dried in a 30°C constant temperature drying oven to obtain the multi-band composite camouflage material.

[0038] Example 2

[0039] Weigh 40 parts of PMMA and dissolve them in 20 ml of xylene, stirring thoroughly at 40°C. Then weigh 100 parts of eicosane and dissolve them in the same solution to form a homogeneous oil phase. Measure 10 parts of Tween 20 and 30 ml of distilled water, mix thoroughly, and slowly add the oil phase solution dropwise. Cool the mixture to 25°C and rotate at 1500 rpm. After emulsifying for 30 minutes, reduce the rotation speed to 500 rpm. Add hydrochloric acid to adjust the pH to 3, set the temperature to 30°C, and maintain the reaction temperature for 12 hours. After the reaction is complete, wash three times, filter, and vacuum dry to obtain phase change microcapsules.

[0040] Weigh 270 parts of PAAS and premix and disperse them using 540 parts of anhydrous ethanol; weigh 8 parts of hydrophilic fumed silica and 30 parts of chromium green, add them to 150 ml of deionized water, and perform ultrasonic vibration and mechanical stirring for 10 min to obtain a suspension; quickly add the predispersed PAAS to the above suspension, increase the rotation speed to 560 rpm, set the heating temperature to 50℃, and continue stirring for two hours to obtain a PAAS mixture.

[0041] Weigh 30 parts of anhydrous lithium chloride and 10 parts of zinc oxide and add them to 50 ml of deionized water; weigh 180 parts of PVA (to make the mass ratio of PAAS to PVA 3:2) and add them to the lithium chloride-zinc oxide solution. Set the heating temperature to 92℃ and the rotation speed to 180 rpm, and stir continuously for two hours to obtain a PVA mixture.

[0042] The PAAS mixture and PVA mixture were stirred evenly at room temperature. After stirring for 0.5 hours at room temperature, 6 parts of floating aluminum powder and 10 parts of phase change microcapsules were added, and stirring was continued for 1 hour. The mixture was poured into a petri dish, vacuumed, and allowed to stand to remove bubbles. It was then dried in a 30°C constant temperature drying oven to obtain the multi-band composite camouflage material.

[0043] Example 3

[0044] Weigh 270 parts of PAAS and premix and disperse them in anhydrous ethanol at a mass ratio of 1:2; weigh 8 parts of hydrophilic fumed silica and 30 parts of chrome green, add them to 150 ml of deionized water, and perform ultrasonic vibration and mechanical stirring for 10 min to obtain a suspension; quickly add the predispersed PAAS to the above suspension, increase the rotation speed to 560 rpm, set the heating temperature to 50℃, and continue stirring for two hours to obtain a PAAS mixture.

[0045] Weigh 30 parts of anhydrous lithium chloride and add it to 50 ml of deionized water; weigh 180 parts of PVA (make the mass ratio of PAAS to PVA 3:2) and add it to the lithium chloride solution. Set the heating temperature to 92℃ and the rotation speed to 180 rpm, and stir continuously for two hours to obtain a PVA mixture.

[0046] The PAAS mixture and PVA mixture were stirred evenly at room temperature. After stirring for 0.5 hours at room temperature, 6 parts of floating aluminum powder were added and stirring was continued for 0.5 hours. The mixture was then poured into a petri dish, vacuumed, and allowed to stand to remove bubbles. The mixture was then placed in a 30℃ constant temperature drying oven to dry, thus obtaining the multi-band composite camouflage material.

[0047] Example 4

[0048] PAAS mixture and PVA mixture were prepared according to the method in Example 1.

[0049] The PAAS mixture and PVA mixture were stirred evenly at room temperature. After stirring for 0.5 hours at room temperature, 6 parts of floating aluminum powder were added and stirring was continued for 0.5 hours. The mixture was then poured into a petri dish, vacuumed, and allowed to stand to remove bubbles. The mixture was then placed in a 30℃ constant temperature drying oven to dry, thus obtaining the multi-band composite camouflage material.

[0050] Figure 2 SEM image of phase change microcapsules; Figure 3 The reflectance of green vegetation leaves under the solar spectrum; Figure 4 The reflectance spectra of camouflage materials examples 1, 2, 3, and 4 under the solar spectrum clearly show that the reflectance spectra of examples 1 and 2 are similar in shape to those of the green leaf, and the features such as "red edge," "green peak," "near-infrared plateau," and "water absorption valley" correspond completely. This indicates that examples 1 and 2 have achieved the camouflage requirements in the visible-near-infrared range by matching the color and spectrum of the green leaf. Table 1 further confirms the camouflage requirements in the solar spectral band through similarity data. Figure 5 Using an infrared thermal imager to depict outdoor radiation temperature characteristics, it was found that the image completely blended with the environmental background. Figure 6 Comparing the total daily radiation temperatures of Examples 1, 2, 3, and 4 with those of the green vegetation, it can be observed that the addition of phase change microcapsules shortens the temperature difference between Examples 1 and 2 and the green vegetation, making them more similar. The overall maximum radiation temperature difference is 1.3℃, meeting the requirements for infrared camouflage. In summary, Examples 1 and 2 meet the requirements for multi-band camouflage in the visible-near-infrared-mid-infrared ranges.

[0051] Table 1. Similarity coefficients between Examples 1, 2, 3, and 4 and various plant leaves.

[0052]

[0053] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A multi-band vegetation-simulating composite camouflage material based on multiple cooling methods, characterized in that, The product comprises, by weight parts: 300-600 parts of highly hygroscopic camouflage substrate, 10-30 parts of high-reflectivity filler, 10-30 parts of phase change microcapsules, and 5-20 parts of additives; the highly hygroscopic camouflage substrate is composed of inorganic hygroscopic agents, sodium polyacrylate and polyvinyl alcohol, and colorants, wherein the colorants are any one or more of chrome green, phthalocyanine, chlorophyll and their derivatives; the high-reflectivity filler includes metallic pigments and high-reflectivity materials in the visible-near-infrared band, wherein the metallic pigments are any one or more of aluminum powder, copper powder and silver powder, and the high-reflectivity materials in the visible-near-infrared band are any one or more of titanium dioxide, zinc oxide or microcapsules with high reflectivity; the phase change microcapsules are microcapsules with polymethyl methacrylate as the shell material and one or more of eicosane or its derivatives as the core material; the additives are hydrophilic or hydrophobic fumed silica.

2. The multi-band vegetation-simulating composite camouflage material based on multiple cooling methods according to claim 1, characterized in that, The highly hygroscopic camouflage substrate is composed of 1-50 parts of hygroscopic inorganic material, 100-300 parts of sodium polyacrylate, 100-300 parts of polyvinyl alcohol, and 1-50 parts of colorant.

3. The multi-band vegetation-simulating composite camouflage material based on multiple cooling methods according to claim 1, characterized in that, The mass ratio of the visible-near-infrared high reflectivity material to the metallic pigment in the high reflectivity filler is 1:0.5~1.

4. A method for preparing a multi-band vegetation-simulating composite camouflage material based on multiple cooling methods as described in any one of claims 1-3, characterized in that, Includes the following steps: (1) Preparation of highly hygroscopic camouflage substrate: Hygroscopic inorganic material and high reflectivity material in the visible-near infrared band are added to deionized water and stirred evenly; polyvinyl alcohol is added and stirred continuously at 200-400 rpm for 1-3 hours at a heating temperature of 80-95℃ to obtain a PVA mixed solution; pigments and additives are added to deionized water and ultrasonically vibrated and stirred to disperse evenly to obtain a suspension; sodium polyacrylate is evenly dispersed in anhydrous ethanol to obtain a PAAS-ethanol mixed solution; the PAAS-ethanol mixed solution is added to the suspension and stirred continuously at 300-600 rpm for 1-2 hours at a heating temperature of 60-80℃ to obtain a PAAS mixed solution; the PVA mixed solution is added to the PAAS mixed solution and stirred continuously at room temperature for 1-2 hours to obtain a highly hygroscopic camouflage substrate; (2) Preparation of phase change microcapsules: Weigh eicosane and dissolve it in polymethyl methacrylate solution; add emulsifier and distilled water dropwise, set the heating temperature to 20~50℃, the rotation speed to 800~3000rpm, emulsify for 10~30min, add hydrochloric acid to adjust the pH value to 3~5, set the temperature to 20~50℃, keep the reaction at the temperature for 1~12h, after the reaction is completed, wash, filter, and vacuum dry to obtain phase change microcapsules; (3) Add the metallic pigment and phase change microcapsules to the highly hygroscopic camouflage substrate prepared in step (1) in sequence, stir at room temperature for 1 to 2 hours; vacuum and let stand to remove bubbles; pour into a mold and dry at 30°C to obtain a multi-band composite camouflage material with multiple cooling methods.

5. The method for preparing multi-band vegetation-simulating composite camouflage material based on multiple cooling methods according to claim 4, characterized in that, In step (1), the mass concentration of the visible-near-infrared high reflectivity material is 0.1 wt% to 1 wt%; the mass concentration of the additive is 0.1 wt% to 1 wt%.

6. The method for preparing multi-band vegetation-simulating composite camouflage material based on multiple cooling methods according to claim 4, characterized in that, In step (2), the core-shell ratio of eicosane to polymethyl methacrylate is 5:

2.

7. The method for preparing multi-band vegetation-simulating composite camouflage material based on multiple cooling methods according to claim 4, characterized in that, In step (3), the mass concentration of the metallic pigment is 0.1 wt% to 1 wt%; the mass concentration of the phase change microcapsules is 0.1 wt% to 2 wt%.

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