Thermal camouflage material and preparation method and application thereof

Abstract

The application discloses a kind of thermal camouflage materials and its preparation method and application, thermal camouflage material from outside to inside includes nylon 66 nanofiber membrane layer, metal reflection layer and substrate layer in turn;The thickness of nylon 66 nanofiber membrane layer is less than 50 μm, and the fiber diameter of nylon 66 in nylon 66 nanofiber membrane layer is less than 400 nm.Preparation method includes: (1) depositing metal reflection layer on the surface of substrate layer;(2) prepare spinning solution, and carry out electrospinning on the surface of receiving substrate to form nylon 66 nanofiber membrane layer, i.e.the thermal camouflage material of the present application.The thermal camouflage material of the present application realizes the low emissivity of 3-5 and 8-14 μm detection band, while realizing infrared selective radiation heat dissipation cooling and >90% average solar reflectivity, with high reflection capacity in 300-400 nm ultraviolet band, moisture permeable and windproof, simple preparation method, raw material is easy to obtain, low production cost, can be used as personal thermal camouflage material in winter snow background.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of camouflage materials, in particular to a kind of metal-polymer multilayer composite structure for personal thermal camouflage clothing materials. BACKGROUND

[0002] With the rapid development of infrared detection and image processing technology, thermal infrared reconnaissance is gradually developing towards multi-spectrum, high sensitivity, high resolution, detection and attack integration, intelligent identification and other directions. However, the current personal camouflage clothing generally does not have the performance of preventing thermal infrared detection or the performance of thermal infrared camouflage is weak. Considering that camouflage clothing can provide the first line of defense against reconnaissance and monitoring for the human body, the related research on thermal infrared camouflage materials for the human body becomes increasingly important. The temperature of human bare skin is usually 32-35℃, and the infrared radiation characteristics are obvious, mainly distributed in the 7-14 μm band; and has the high emissivity characteristics (εskin≈0.98) similar to black body, which reaches the peak infrared radiation near 9.5 μm. For the detector, due to the influence of H2O, CO2 and suspended particles in the atmosphere, the infrared radiation has less attenuation and strong penetration ability in the atmospheric window band of short wave 3-5 μm and long wave 8-14 μm, which is the most commonly used infrared detection band, and 5-8 μm is a non-detection window band. As can be seen from the above, the human body infrared radiation distribution overlaps with the long wave infrared detection window. According to the AM1.5G solar radiation spectrum, the solar spectrum covers a wide band, including ultraviolet-visible-near infrared (UV-VIS-NIR) band, with high energy density (1000 W / m 2 ), and the average solar reflectivity of human skin is less than 60%, which will absorb the incident solar energy and warm up. In summary, the human body thermal radiation characteristics are exposed to risk.

[0003] According to the Stefan-Boltzmann law:

[0004] M=εσT 4

[0005] M is the infrared radiation emittance of the object; ε is the infrared emissivity; σ is the Boltzmann constant; T is the surface temperature of the object 5. Compared with the environment, the infrared radiation characteristics of the human body are obvious, combined with the detection band of the thermal imager and the infrared radiation formula, reducing the surface temperature or changing the emissivity is the two main ways to realize personal thermal camouflage. Although there are many works around the structure of flexible camouflage devices at present, but the related research on personal thermal camouflage is almost rare.

[0006] Current surface finishing, blade coating, lamination and other technologies can directly coat phase change microcapsules, low-emissivity components or thermochromic structures with infrared camouflage function to the surface of existing clothing materials for camouflage. Further, low-emissivity nanoparticles, conductive fillers, thermochromic VO2 particles and other camouflage functional particles can be directly embedded in the fiber or yarn during the forming stage. The above technical solutions have the following disadvantages: the fabric material treated by low-emissivity coating is hard, has poor touch feeling and reduced air permeability; the coating treatment method is a static control method, and the camouflage effect has certain limitations; the high gloss of metal fillers increases the exposure risk in the radar, laser and visible light bands; the use of metal fillers also increases the weight of the clothes; and the phase change material has the disadvantages of short change duration, easy breakage and easy falling off. In addition to the above fiber-based camouflage structure design methods, the related researches of electro-thermal driven phase change hybrid film, humidity responsive photonic structure film and shape memory polymer assisted infrared adaptive skin also promote the progress of flexible thermal camouflage materials. The above technical solutions have the following disadvantages: the preparation of the electro-modulated film device is complex, the cost is high, and it is difficult to prepare in large area; the shape memory alloy material has poor ductility, and mixing with other polymer components will reduce the shape memory effect; and the above camouflage film devices do not consider human body heat management and basic wearing comfort. In addition, some two-dimensional nanomaterial films with low surface emissivity and excellent optoelectronic tuning performance (adaptive infrared camouflage film, high-temperature resistant ultra-thin camouflage film, strain responsive soft robot, etc.) also show certain thermal camouflage potential. For example, graphene and carbon nanotube film are used as variable emissivity layer, and the carrier density is adjusted by embedding and extracting different components in ionic liquid, and then the emissivity is adjusted. However, the above technical solutions also have the following disadvantages: it is difficult to ensure the basic wearing comfort such as air permeability and moisture permeability; the structure of the soft robot controlled by the microfluidic system is complex and heavy, and the portability is poor. There are also research reports on the use of flexible wearable thermoelectric devices and thermochromic outer layers to realize visible-infrared dual-band camouflage from the perspective of temperature regulation, but the preparation process is complex and the wearing comfort is poor. SUMMARY

[0007] The present application provides a kind of thermal camouflage material and its preparation method and application, to solve the technical problems of the prior art personal thermal camouflage material difficult to consider multi-spectrum low-emissivity thermal camouflage and wearing comfort.

[0008] To solve the above technical problems, the technical scheme provided by the present application is as follows:

[0009] A kind of thermal camouflage material, the thermal camouflage material is multilayer structure, from outside to inside include nylon 66 nanofiber membrane layer, metal reflection layer and substrate layer in turn;The thickness of the nylon 66 nanofiber membrane layer is less than 50 μm, and the fiber diameter of nylon 66 in the nylon 66 nanofiber membrane layer is less than 400 nm.

[0010] The design idea of the above technical solution is that, from the aspects of reducing surface temperature and inhibiting emissivity, the personal thermal camouflage material with multi-spectrum compatibility and certain wearing comfort needs to meet the following requirements: (1) low emissivity thermal camouflage in 3-5 μm and 8-14 μm detection bands; (2) selective radiation heat dissipation to reduce temperature in 5-8 μm; (3) high reflection in solar band to avoid absorbing solar radiation heat energy to rise temperature; (4) certain wearing comfort. The present application takes electrospun nylon 66 nanofiber membrane as the outermost layer, wherein the inventor finds that the nylon 66 molecular chain is characterized by methylene and amide groups (infrared characteristic peaks: -NH- stretching vibration peak: 3303 cm -1 ; -CH2- symmetric stretching vibration peak: 2864 cm -1 ; -CH2- bending vibration peak: 1465 cm -1 ; amide I band: 1642 cm -1 ; amide II band: 1539 cm -1 ; amide III band: 1275 cm -1 ), so it correspondingly absorbs less in 3-5 μm and 8-14 μm detection bands, and can realize low emissivity thermal camouflage function in the detection bands. The present application further limits the fiber size of the nylon 66 nanofiber membrane, so that the size of the scatterers in the nylon 66 nanofiber membrane is close to or much smaller than the incident electromagnetic wavelength, so that the incident sunlight is scattered by Mie and Rayleigh resonance in the nanofiber membrane, thereby reflecting the sunlight and presenting a white appearance, realizing visible optical camouflage; at the same time, by further limiting the fiber size of the nylon 66 nanofiber membrane, the scatterers in the fiber membrane are mostly concentrated in the size of hundreds of nanometers, thereby strongly scattering short-wave sunlight by Mie scattering, and ultraviolet camouflage can be realized. Based on the above improvements, the present application further specially designs the thickness of the nylon 66 nanofiber membrane, so that its infrared transmittance is at a high level, and the metal reflection layer is used in combination with the nylon 66 nanofiber membrane, effectively improving the reflectivity in the infrared band, avoiding the absorption of infrared rays to cause the material to rise in temperature, thereby realizing thermal camouflage. In addition, it is worth mentioning that the interwoven pore structure in the nylon 66 nanofiber membrane can provide a channel for the passage of water vapor, giving the material good moisture permeability. Therefore, the thermal camouflage material of the present application has low emissivity thermal camouflage in specific bands, selective radiation heat dissipation, high reflection in solar band, and good wearing comfort.

[0011] As a further preferred embodiment of the above technical solution, the thickness of the nylon 66 nanofiber membrane layer is 28 μm, and the fiber diameter of the nylon 66 in the nylon 66 nanofiber membrane layer is 100-240 nm. In order to balance the spectral requirements of the multi-band compatible personal thermal camouflage material, the nylon 66 nanofiber membrane layer in the above parameter range has the best camouflage effect.

[0012] As a further preferred embodiment of the above technical solution, the pore size of the nylon 66 in the nylon 66 nanofiber membrane layer is 60-420 nm. The nylon 66 nanofiber membrane layer in the above parameter range can balance the infrared, solar band transmittance and solar reflectance, and achieve a multi-band camouflage effect.

[0013] As a further preferred embodiment of the above technical solution, the substrate layer is a nano-porous polyethylene film, and the thickness of the substrate layer is 16 μm.

[0014] As a further preferred embodiment of the above technical solution, the metal reflective layer is an Al reflective layer or an Ag reflective layer, and the thickness of the metal reflective layer is 150-300 nm.

[0015] Based on the same technical concept, the present application also provides a preparation method of the above thermal camouflage material, comprising the following steps:

[0016] (1) depositing a metal reflective layer on the surface of the substrate layer;

[0017] (2) dissolving nylon 66 resin particles in a solvent to prepare a spinning solution by sufficient stirring, using the substrate layer with the metal reflective layer as a receiving substrate, and performing electrospinning on the surface of the receiving substrate using the spinning solution to form a nylon 66 nanofiber membrane layer, thereby obtaining the thermal camouflage material; the mass fraction of the nylon 66 resin in the spinning solution is less than 20%.

[0018] The design idea of the above technical solution is that the inventors have found that the mass fraction of the nylon 66 resin spinning solution determines the pore size of the final nylon 66 nanofiber membrane layer and the diameter of the nylon 66 fiber. With the increase of the mass fraction of the spinning solution, the fiber diameter is distributed from nanometers to micrometers, corresponding to the morphology change of the fiber from low-concentration unstable electrostatic spraying to produce beaded fibers, smooth fibers and flat ribbon-shaped fibers, and the pore size also increases and the pore size distribution widens with the increase of the concentration. When the mass fraction of the spinning solution is within the range of the present application, the pore size of the nylon 66 nanofiber membrane layer and the diameter of the nylon 66 fiber are mainly in the order of hundreds of nanometers, which is comparable to the wavelength of ultraviolet light, thereby bringing about strong Mie scattering effect and improving the reflection effect of ultraviolet light.

[0019] As a further preferred embodiment of the above technical solution, the mass fraction of the nylon 66 resin in the spinning solution in step (2) is 17%.

[0020] As a further preferred embodiment of the above technical solution, the method for forming a nylon 66 nanofiber membrane layer by electrospinning the spinning solution on the surface of the receiving substrate in step (2) is as follows: the spinning solution is injected into a 10ml syringe equipped with a 26 gauge needle, the receiving substrate is fixed on a stainless steel roller, a sliding table is used for left and right translation, and the electrospinning is performed at a push injection speed of 1mL·h -1 The electrospinning voltage is 25-32KV, the temperature of the electrospinning machine is 30℃, and the humidity in the electrospinning machine is 30RH%. The spinning effect is best with the above parameters, liquid droplets can be avoided from splashing, and the effect of stable and continuous yarn output is achieved.

[0021] As a further preferred embodiment of the above technical solution, the method for depositing a metal reflective layer on the substrate layer in step (1) is as follows: dopamine hydrochloride is dissolved in a Tris-HCl buffer solution to obtain a polydopamine solution; the substrate layer is immersed in the polydopamine solution to form an adhesion layer on the surface; and a high-vacuum magnetron sputtering system is used to deposit a metal reflective layer on the surface of the substrate layer.

[0022] Based on the same technical concept, the application also provides an application of the thermal camouflage material or the thermal camouflage material prepared by the preparation method.

[0023] Compared with the prior art, the application has the following beneficial effects:

[0024] (1) The thermal camouflage material realizes low emissivity (ε 3-5μm =0.09 and ε 8-14μm =0.23) in the 3-5 and 8-14um detection wave bands to solve the thermal camouflage demand, and high emissivity (ε 5-8μm =0.55) in the non-detection wave band 5-8um to realize infrared selective radiation heat dissipation and cooling, and has a lower equilibrium temperature compared with a sample without selective radiation under the same heating condition, and can realize an average solar reflectivity of >90%, and can bring about a cooling effect of about 20℃ for a skin simulator compared with a low-emissivity camouflage film with poor solar reflectivity under peak solar radiation intensity. -2 In addition, the thermal camouflage material has high reflection capacity in the ultraviolet wave band of 300-400nm, meets the requirement of ultraviolet camouflage, can realize compatible thermal camouflage with a snow background, and has a water vapor transmission rate of about 0.033g·cm -1 ·h -1 , low air permeability, and can be used as a personal thermal camouflage material in winter under a snow background.

[0025] (2) The preparation method of the thermal camouflage material is simple, the raw materials are easy to obtain, the production cost is low, and the method is suitable for large-scale industrial production.

[0026] The application will be described in further detail below with reference to the drawings. BRIEF DESCRIPTION OF DRAWINGS

[0027] The accompanying drawings, which form a part of this application, are intended to provide further understanding of the application and are incorporated herein in their entirety, and they show by way of illustration the present embodiments of the application and are used for explaining the present application. In the drawings:

[0028] Figure 1 SEM images and size distribution of the nylon 66 nanofiber membranes prepared from the different mass fraction of the spinning solution of Example 1;

[0029] Figure 2 Capillary pore size distribution of the nylon 66 nanofiber membranes prepared from the different mass fraction of the spinning solution of Example 1;

[0030] Figure 3 Comparison chart of the infrared transmittance of different processes of nylon 66 tested by fixing the membrane thickness and changing the mass concentration and by fixing the mass concentration and changing the membrane thickness of Example 1;

[0031] Figure 4 Finite difference time domain simulation scattering efficiency of Example 1;

[0032] Figure 5 UV–VIS–NIR diffuse reflectance test results of Example 1;

[0033] Figure 6 Simulation curves of the average infrared transmittance and the average solar reflectance of the nanofiber membranes with a given porosity of 80% at 3-5 μm and 8-14 μm with respect to the diameter and the membrane thickness of Example 1;

[0034] Figure 7 Reflection spectrum test curve of the thermal camouflage material of Example 1;

[0035] Figure 8 Structure schematic diagram of the infrared camouflage effect test device of the thermal camouflage material of Example 1 and test results;

[0036] Figure 9 Photo of the spectral selective radiation heat dissipation effect test experimental device of the thermal camouflage material of Example 1;

[0037] Figure 10 Structure schematic diagram, photo and test results of the solar radiation heat energy insulation efficiency test experimental device of the thermal camouflage material of Example 1;

[0038] Figure 11 UV–VIS–NIR reflectance of Example 1 used as a comparison sample for outdoor reflection of solar radiation experiments;

[0039] Figure 12The thermal camouflage material of Example 1 was tested for water vapor transmission rate, air permeability and mechanical properties. DETAILED DESCRIPTION

[0040] The embodiments of the present application are described in detail below with reference to the accompanying drawings, but the present application can be implemented in various different ways as defined and covered by the claims.

[0041] Example 1:

[0042] The thermal camouflage material of the present example is of a multi-layer structure, comprising a nylon 66 nanofiber film layer, a metal reflection layer and a substrate layer from outside to inside; wherein the fiber diameter of nylon 66 in the nylon 66 nanofiber film layer is 100-240 nm, the thickness of the nylon 66 nanofiber film layer is 28 μm, and the pore size is 60-420 nm; the metal reflection layer is an Al layer; and the substrate layer is a nano-porous polyethylene film with a thickness of 16 μm.

[0043] The thermal camouflage material of the present example is prepared by the following method:

[0044] Raw materials: nylon 66 resin particles, 16 μm thick nano-porous polyethylene film (nanoPE), 25 μm thick nano-porous polypropylene film (nanoPP), high-purity Al target material, formic acid solvent, dopamine hydrochloride and 10 mM Tris-HCl buffer.

[0045] (1) First, dissolve dopamine hydrochloride in Tris-HCl buffer to obtain a polydopamine (PDA) solution; then immerse nanoPE in the surface of the PDA solution to form an adhesion layer; then use a high-vacuum magnetron sputtering system to deposit a metal Al reflection layer on the surface of the PDA-treated nanoPE. In order to prevent the metal layer from blocking the pore structure of the nanoPE, the nanoPE was pre-treated with a punching process.

[0046] (2) Dissolve nylon 66 resin particles in formic acid solvent and then thoroughly stir to prepare a 17% mass concentration of spinning solution, then inject into a 10 ml syringe equipped with a 26 gauge needle to spin at a bolus injection speed of 1 mL·h -1 The electrospinning voltage is about 25-32 KV, the spinning machine temperature is 30°C, and the humidity is 30 RH%. Then the above Al-metallized nanoPE is fixed as a receiving substrate on a stainless steel roller, and the left and right translation of the slide table is coordinated to finally obtain the thermal camouflage material of the present example.

[0047] The thermal camouflage material of the present example is used to make a flexible wearable personal thermal camouflage clothing.

[0048] To study the influence of the thickness of the nylon 66 nanofiber membrane and the morphology of the fiber on the spectrum in the thermal camouflage material of this embodiment, the mass fraction of the spinning solution in the preparation method (2) was changed, and the spinning solution with a concentration ranging from low to medium to high (7wt% to 27wt%) was used to process fibers with diameters ranging from nanometers to micrometers. The morphological transformation of the fibers was from bead-like fibers produced by low-concentration unstable electrostatic spraying to smooth fibers and then to flat ribbon fibers. Figure 1 The morphology and diameter distribution of nylon 66 fibers prepared from spinning solutions with different mass fractions were observed by scanning electron microscopy (measured using ImageJ software). Figure 2 The capillary pore size distribution of nylon 66 nanofiber membranes prepared with spinning solutions of different mass fractions was obtained. According to the results of capillary pore size test, the pore size of the fiber membranes changed similarly with concentration. When the mass concentration was less than 20 wt%, the pore size was mostly concentrated in the hundreds of nanometers. Subsequently, as the concentration increased, the pore size increased and the pore size distribution became wider.

[0049] The infrared transmittance of nylon 66 processed with different methods was tested, with the film thickness fixed and the mass concentration varied, and with the mass concentration fixed and the film thickness varied, respectively (results are shown in the figure). Figure 3 As shown, (a) represents the infrared transmittance of nylon 66 fiber membranes of the same thickness but different mass concentrations, (b) represents the infrared reflectance of nylon 66 fiber membranes of the same thickness but different mass concentrations, (c) represents the infrared transmittance of nylon 66 nanofiber membranes of different thicknesses prepared with 17wt% spinning solution, and (d) represents the infrared transmittance of nylon 66 nanofiber membranes of different thicknesses prepared with 20wt% spinning solution. The results are shown in the figure. Figure 5 As shown in the figure, (a)-(c) represent the UV-VIS-NIR diffuse reflectance of the nylon 66 nanofiber membrane, and (d)-(f) represent the UV-VIS-NIR transmittance of the nylon 66 nanofiber membrane. Combined with finite difference time-domain simulation (FDTD) scattering efficiency (the results are shown in the figure below). Figure 4It can be inferred that the fiber diameter and pore size distribution close to short wave 3-5 μιη at high concentration will produce partial Mie scattering effect, so that the same thickness under the concentration of the spinning solution increases, the infrared transmittance in 3-5 μιη attenuates faster than that in 8-14 μιη. Under the same mass concentration, the material thickness increases, the corresponding volume increases, the optical path of the incident infrared electromagnetic wave becomes longer, resulting in the gradual decrease of 3-5 μιη and 8-14 μιη infrared transmittance.

[0050] From Figure 5 It can be seen that the nylon 66 nanofiber membrane has high reflectivity in the ultraviolet band (300-400 nm), which is caused by the strong Mie scattering effect of the nanoscale fiber and pore structure with a size comparable to the ultraviolet light. When interfering with the long-wave red light in the solar spectrum, the fiber size of the medium concentration nylon 66 is much smaller than the incident light wavelength, resulting in a decrease in Mie scattering and an increase in Rayleigh scattering effect, so the reflectivity in the near-infrared band decreases with the increase of wavelength. The high concentration electrospun nylon 66 fiber membrane with larger diameter (23wt% and 27wt%) and wider size distribution has a wide range of Mie scattering in the entire solar band, and the reflectivity curve tends to be flat as a whole, with an average reflectivity of about 70%. Increasing the thickness of the membrane can improve the solar reflectivity, because the dense arrangement of the fibers will cause a large number of interfaces between the air and the fiber skeleton, which is beneficial to increase the light scattering probability. Although the increase of fiber diameter or membrane thickness can improve the solar reflectivity, this improvement is at the expense of the infrared transmittance, and the spectral requirements of infrared transmittance and solar reflectivity need to be balanced.

[0051] Further simulation of the spectral performance of the nylon 66 nanofiber membrane is carried out, and the optimal membrane thickness and diameter range are obtained. Figure 6(Figure (a) is the infrared transmittance (2.5-25 μm) of the nylon 66 with a mass concentration of 27 wt%, a porosity of 80%, and a film thickness of 50 μm, (b) is the simulated and measured spectral curves of the solar reflectance (380-890 nm), (c) is the influence of the fiber diameter and the film thickness on the infrared transmittance of the nylon 66 nanofiber film at 3-5 μm under the same porosity, (d) is the influence of the fiber diameter and the film thickness on the infrared transmittance of the nylon 66 nanofiber film at 8-14 μm under the same porosity, (e) is the influence of the fiber diameter and the film thickness on the solar reflectance of the nylon 66 nanofiber film under the same porosity) The average infrared transmittance at 3-5 μm and 8-14 μm and the average solar reflectance of the nanofiber film with a given porosity of 80% are simulated in relation to the fiber diameter and the film thickness. The FDTD simulation results show that the fiber diameter < 400 nm and the film thickness < 50 μm are conducive to achieving high infrared transmittance, although increasing the fiber diameter or the film thickness is conducive to improving the solar reflectance, but such improvement is at the expense of the transmittance at the infrared and solar wave bands, which is consistent with the experimental measurement results.

[0052] The performance of the thermal camouflage material of the present embodiment was tested.

[0053] Firstly, the infrared camouflage effect of the thermal camouflage material of the present embodiment was tested, and the reflectance spectrum test curve of the thermal camouflage material of the present embodiment is shown in Figure 7 The curve test device is shown in Figure X (a). The high-emissivity adhesive tape with an emissivity close to that of a black body was used as a comparative sample, a direct current power supply was connected to the bottom heating sheet of the sample, and an adiabatic polystyrene foam substrate was used to eliminate the downward heat conduction effect. The results are shown in Figure 8 (b). Under the same surface temperature (T s ), the average radiation temperature of the thermal camouflage material of the present embodiment was always lower than that of the adhesive tape.

[0054] The spectral selective radiation heat dissipation effect of the thermal camouflage material of the present embodiment was further tested, and the test device was based on the device shown in Figure X (a) and covered with an acrylic plastic cover to avoid the interference of air on the temperature measurement (the photo is shown in Figure 9 ). Celgard 2500 (porous polypropylene, nanoPP) and a nano-porous polyethylene (nanoPE) laminated with a sputtered metal reflection layer were used to prepare a sample with a size and thickness basically consistent with those of the thermal camouflage material of the present embodiment as a comparative sample. The results are shown in Figure 8 (c) and Figure 8(d) As shown, under the influence of no solar radiation in the room, the metal surface of the comparative sample is heated synchronously with the thermal camouflage material of the present embodiment on the same heating plate, and the surface temperature of the two samples is recorded in real time by testing the thermocouple. When thermal equilibrium is reached, it can be observed that the surface temperature of the thermal camouflage material of the present embodiment is always lower than that of the metal layer of the non-spectrum selective radiation low-emissivity comparative sample. According to the blackbody radiation law, the infrared radiation exitance of the two samples is calculated, and the thermal camouflage material of the present embodiment is obviously superior to the full low-emissivity Al / nanoPE / PP in terms of radiation heat dissipation ability at 5-8 μm.

[0055] The effect of the thermal camouflage material of the present embodiment on the insulation of solar radiation heat energy was tested, and the test device and results are shown in Figure 10 , wherein the structure diagram and the physical photo of the test device are shown in Figure 10 (a) and Figure 10 (b), respectively, the 25 μm thick nanoPP metal surface and the white surface sputtered with metal Al are laminated with the nanoPE layer to prepare metal-colored and white samples with sizes and thicknesses basically consistent with those of the thermal camouflage material of the present embodiment. Four completely identical heating plates are connected to a direct current power supply to maintain synchronous temperature rise, and the power density is controlled to be 104 W / m 2 to simulate the metabolic heat production rate of the human body. The results are shown in Figure 10 (c), Figure 10 (c) is the real-time temperature curve of the four skin simulators when using transparent PE windshields (without thermal convection), and the temperature of the skin simulator covered by the thermal camouflage material of the present embodiment is obviously lower than that covered by the metal-colored Al / nanoPP / nanoPE or white nanoPP / Al / nanoPE. Compared with the bare skin simulator, the temperature of the skin simulator covered by the thermal camouflage material of the present embodiment can be reduced by more than 20℃ under the peak solar radiation intensity. In addition, when the PE windshields are removed and air convection is introduced, the temperature of the skin simulator covered by the thermal camouflage material of the present embodiment is still lower than that covered by the other two low-emissivity films or in the bare state, proving that the thermal camouflage material of the present embodiment has excellent effect on insulating solar radiation heat energy.

[0056] The inventors also took snow photos of the camouflage effect of the thermal camouflage material of the present embodiment in Harbin in winter in January 2023. The thermal camouflage material of the present embodiment was adhered to the outer layer of a down jacket (as shown in Figure 10The apparent temperature of the nanofiber membrane covering area in the 8-14 pm thermal image is close to the uniform snow background, which has the infrared thermal camouflage effect. Then, the ultraviolet imaging system is modified by using the 380 nm center wavelength filter to verify the ultraviolet camouflage effect. The contrast sample cotton, nylon cloth and printed paper have similar white appearance in the visible light band as the thermal camouflage material of the embodiment, but under the ultraviolet lens, the contrast sample is black and the thermal camouflage material of the embodiment is white similar to the snow background, which proves the ultraviolet camouflage ability of the thermal camouflage material of the embodiment. Figure 10 (e) The photos of PA66 / Al / nanoPE under the uniform snow background, visible light and ultraviolet 380 nm center wavelength filter lens (the upper row from left to right is the white cotton cloth, white nylon cloth and white paper contrast sample, and the lower row is two PA66 / Al / nanoPE samples). Figure 11 The UV-VIS-NIR reflectance is used as the outdoor reflected solar radiation experiment contrast sample.

[0057] Finally, the water vapor transmission rate (WVTR), air permeability and mechanical properties of the thermal camouflage material of the embodiment are tested, and the results are shown in Figure 12 As shown in the figure, the WVTR of the thermal camouflage material of the embodiment is approximately 0.033 g·cm -2 ·h -1 , the air permeability is very low but is conducive to windproof for winter snow scene. In terms of mechanical properties, the tensile strength of the thermal camouflage material of the embodiment is 57.11 MPa, the elongation at break is 36.14%, and the Young's modulus (slope of stress-strain curve) is better than that of traditional nylon cloth.

[0058] Embodiment 2:

[0059] The thermal camouflage material of the embodiment is a multilayer structure, which includes a nylon 66 nanofiber membrane layer, a metal reflection layer and a substrate layer from outside to inside; wherein the fiber diameter of nylon 66 in the nylon 66 nanofiber membrane layer is 45-105 nm, the thickness of the nylon 66 nanofiber membrane layer is 45 pm, and the pore size is 75-255 nm; the metal reflection layer is an Al layer; and the substrate layer is a nano-porous polyethylene membrane with a thickness of 16 pm.

[0060] The thermal camouflage material of the embodiment is prepared by the following method:

[0061] Raw materials: nylon 66 resin particles, 16 pm thick nano-porous polyethylene membrane (nanoPE), 25 pm thick nano-porous polypropylene membrane (nanoPP), high-purity Al target material, formic acid solvent, hydrochloric acid dopamine and 10Mm Tris-HCl buffer.

[0062] (1) First, dopamine hydrochloride is dissolved in Tris-HCl buffer to obtain a polydopamine (PDA) solution; then nanoPE is immersed in the surface of the PDA solution to form an adhesion layer; subsequently, a metal Al reflective layer is deposited on the surface of the PDA-treated nanoPE by using a high-vacuum magnetron sputtering system. In order to prevent the metal layer from blocking the pore structure of the nanoPE, the nanoPE is pre-treated by punching.

[0063] (2) Dissolve nylon 66 resin particles in formic acid solvent and then fully stir to prepare a 13% mass concentration of spinning solution, and then inject a 10ml syringe equipped with a 26 gauge needle to spin at a bolus injection speed of 1mL·h -1 The electrospinning voltage is about 25-32KV, the spinning machine temperature is 30℃, and the humidity is 30RH%. Then the above Al-metallized nanoPE is fixed on a stainless steel roller as a receiving substrate, and the slide table is translated left and right to finally obtain the thermal camouflage material of the embodiment.

[0064] The thermal camouflage material of the embodiment is used to make a flexible wearable personal thermal camouflage clothing.

[0065] Embodiment 3:

[0066] The thermal camouflage material of the embodiment is a multilayer structure, which includes a nylon 66 nanofiber film layer, a metal reflective layer and a substrate layer from outside to inside; wherein the fiber diameter of nylon 66 in the nylon 66 nanofiber film layer is 120-270nm, the thickness of the nylon 66 nanofiber film layer is 15μm, and the pore size is 150-770nm; the metal reflective layer is an Al layer; and the substrate layer is a nano-porous polyethylene film with a thickness of 16μm.

[0067] The thermal camouflage material of the embodiment is prepared by the following method:

[0068] Raw materials: nylon 66 resin particles, 16μm thick nano-porous polyethylene film (nanoPE), 25μm thick nano-porous polypropylene film (nanoPP), high-purity Al target material, formic acid solvent, dopamine hydrochloride and 10Mm Tris-HCl buffer.

[0069] (1) First, dopamine hydrochloride is dissolved in Tris-HCl buffer to obtain a polydopamine (PDA) solution; then nanoPE is immersed in the surface of the PDA solution to form an adhesion layer; subsequently, a metal Al reflective layer is deposited on the surface of the PDA-treated nanoPE by using a high-vacuum magnetron sputtering system. In order to prevent the metal layer from blocking the pore structure of the nanoPE, the nanoPE is pre-treated by punching.

[0070] (2) The nylon 66 resin particles are dissolved in formic acid solvent and then a 20% mass concentration of spinning solution is prepared by fully stirring, followed by injection into a 10 ml syringe equipped with a 26 gauge needle to spin at a 1 mL·h -1 push injection speed. The electrospinning voltage is about 25-32 KV, the spinning machine temperature is 30°C, and the humidity is 30 RH%. Then the above-mentioned Al-metallized nanoPE is fixed on a stainless steel roller as a receiving substrate, and is matched with a slide table to move left and right, and finally the thermal camouflage material of the present embodiment is obtained.

[0071] The thermal camouflage material of the present embodiment is used to make a flexible wearable personal thermal camouflage clothing.

[0072] The above is only the preferred embodiment of the present application and is not used to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application. The above is only the preferred embodiment of the present application, and the protection scope of the present application is not limited to the above-mentioned embodiment. For those skilled in the art, the improvements and changes obtained without departing from the technical concept of the present application shall be regarded as the protection scope of the present application.

Claims

1. A thermal camouflage material, characterized in that, The thermal camouflage material is a multi-layer structure, from outside to inside comprising a nylon 66 nanofiber film layer, a metal reflection layer and a substrate layer in sequence; the thickness of the nylon 66 nanofiber film layer is less than 50 μm, and the fiber diameter of nylon 66 in the nylon 66 nanofiber film layer is less than 400 nm.

2. The thermal camouflage material according to claim 1, characterized in that, The thickness of the nylon 66 nanofiber film layer is 28 μm, and the fiber diameter of nylon 66 in the nylon 66 nanofiber film layer is 100-240 nm.

3. The thermal camouflage material of claim 1, wherein, The pore size of the nylon 66 nanofiber film layer is 60-420 nm.

4. The thermal camouflage material according to any one of claims 1 to 3, characterized in that, The substrate layer is a nano-porous polyethylene film, and the thickness of the substrate layer is 16 μm.

5. The thermal camouflage material according to any one of claims 1 to 3, characterized in that, The metal reflection layer is an Al reflection layer or an Ag reflection layer.

6. A method of producing a thermal camouflage material according to any one of claims 1 to 5, characterized in that, The method comprises the following steps: (1) depositing a metal reflection layer on the surface of the substrate layer; (2) dissolving nylon 66 resin particles in a solvent to prepare a spinning solution by sufficient stirring, using the substrate layer with the metal reflection layer as a receiving substrate, and using the spinning solution to perform electrostatic spinning on the surface of the receiving substrate to form a nylon 66 nanofiber film layer, thereby obtaining the thermal camouflage material; the mass fraction of nylon 66 resin in the spinning solution is less than 20%.

7. The method of claim 6, wherein the heat camouflage material is prepared by mixing the heat camouflage material with a solvent. The mass fraction of nylon 66 resin in the spinning solution in step (2) is 17%.

8. The method of claim 6, wherein the heat camouflage material is prepared by mixing the heat camouflage material with a solvent. The method for forming a nylon 66 nanofiber membrane layer by electrospinning the spinning solution on the surface of a receiving substrate in step (2) is as follows: the spinning solution is injected into a 10-ml syringe equipped with a 26-gauge needle, the receiving substrate is fixed on a stainless steel roller, a sliding table is used for left-right translation, and spinning is performed at a push injection speed of 1 mL·h -1 -1, an electrospinning voltage of 25-32 KV, a spinning machine temperature of 30°C, and a spinning machine humidity of 30 RH%.

9. The method of producing a thermal camouflage material according to any one of claims 6 to 8, characterized in that, In step (1), the method for depositing a metal reflection layer on the substrate layer is as follows: dissolving dopamine hydrochloride in a Tris-HCl buffer to obtain a polydopamine solution; immersing the substrate layer in the polydopamine solution to form an adhesive layer on the surface; and using a high-vacuum magnetron sputtering system to deposit a metal reflection layer on the surface of the substrate layer.

10. Use of a thermal camouflage material according to any one of claims 1 to 5 or a thermal camouflage material produced by the production method according to any one of claims 6 to 9, characterized in that, The thermal camouflage material is used for making a flexible wearable personal thermal camouflage clothing.

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