Multi-layer multifunctional thermal management material

Abstract

A thermal management material comprising a substrate having an outer surface and an inner surface, and a plurality of multi-layer multi-functional thermal management elements bonded to the outer surface of the substrate, the multi-layer multi-functional thermal management elements comprising a low thermal emissivity layer and a high solar absorptivity layer.

Description

Detailed Description of the Invention

[0001] [Cross - Reference to Related Applications]

[0001] This application claims the benefit of the filing date of U.S. Provisional Patent Application No. 62 / 916,097, filed on October 16, 2019, which is hereby incorporated by reference in its entirety.

[0002] [Technical Field]

[0002] This disclosure generally relates to substrates such as fabrics for body gears and other articles having designed performance characteristics, and more particularly to multi - layer thermal management elements bonded to the outer surface of the substrate that limit heat transfer from the outer surface of the substrate to the environment, and further to technical gears such as clothing items that trap solar radiation and convert it into heat directed towards the inside of the substrate.

[0003] [Background]

[0003] Insulating heat - reflective materials typically take the form of a single metal film or a discrete pattern of metal elements adhered or otherwise attached onto a substrate. Insulating heat - reflective materials are used as the inner surface of clothing items such as jackets. A metal film or patterned heat - reflective element is disposed on the inner surface of the clothing item, e.g., the surface facing inward, so as to reflect the wearer's body heat back to the inside of the clothing item or the body side, thereby maintaining the heat generated from the body and keeping the wearer of the clothing item warm under low - temperature conditions. These materials achieve improved heat retention, but there is still a continuing need for new materials that achieve better thermal management.

[0004]

[0004] The embodiments will be readily understood by the following detailed description in conjunction with the accompanying drawings. The embodiments are shown by way of example and not as limitations in the form of the accompanying drawings.

Brief Description of the Drawings

[0005]

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[0006] [DETAILED DESCRIPTION OF THE DISCLOSED EMBODIMENTS]

[0021] In the following detailed description, reference is made to the accompanying drawings, which form a part hereof and in which are shown by way of illustration embodiments that may be practiced. It is to be understood that other embodiments may be utilized and structural or logical changes may be made without departing from the scope. Accordingly, the following detailed description is not to be taken in a limiting sense, and the scope of the embodiments is defined by the appended claims and their equivalents.

[0007]

[0022] Various operations may be described in sequence as a plurality of distinct operations for the purpose of facilitating understanding of the embodiments. However, the order of description should not be construed as suggesting that these operations are order dependent.

[0008]

[0023] The description may use perspectives based on descriptions such as up / down, back / front, and top / bottom. Such descriptions are used merely to facilitate discussion and are not intended to limit the application of the disclosed embodiments.

[0009]

[0024] The terms "coupled" and "connected" may be used along with their derivatives. It should be understood that these terms are not intended to be synonyms for each other. Rather, in certain embodiments, "connected" may be used to indicate that two or more elements are in direct physical contact with each other. "Coupled" may mean that two or more elements are in direct physical contact with each other. However, "coupled" may also mean that two or more elements are not in direct contact with each other but still cooperate or interact with each other.

[0010]

[0025] The term "colorant" means a substance added to change the color of a material such as a high solar absorptance layer, for example, a polymer overlayer. Most colorants can be classified as containing dyes or pigments, or some combination thereof.

[0011]

[0026] For purposes of explanation, an expression in the form of "A / B" or "A and / or B" means (A), (B), or (A and B). For purposes of explanation, an expression in the form of "at least one of A, B, and C" means (A), (B), (C), (A and B), (A and C), (B and C), or (A, B, and C). For purposes of explanation, an expression in the form of "(A)B" means (B) or (AB), that is, A is an optional element.

[0012]

[0027] In the description, the terms "embodiment" or "embodiments" may be used, which may refer to one or more of the same or different embodiments. Further, terms such as "comprising", "including", "having", etc. are synonymous when used with respect to embodiments.

[0013]

[0028] The Omni-Heat (trademark) reflective material functions by reflecting heat radiation back to the body. Materials important in this performance are metals, including but not limited to aluminum, silver, and gold. In addition to showing high reflectivity in the wavelength range of 2.5 to 40 microns, these materials also show low emissivity in the same wavelength range. In other words, these materials exhibit high heat reflectivity and low heat emissivity.

[0014]

[0029] From a mathematical consideration of conduction, convection, and radiation, the main modes of heat transfer, it can be seen that one term, ΔT, is common to all three, which is the temperature difference between the material losing heat and the material / environment gaining heat. These equations are shown below.

Equation

[0015]

[0030] Regarding the above equations, q 対流 is the heat transfer due to convection, where h is the convective heat transfer coefficient, T s is the surface temperature, and T a is the ambient temperature; q 伝導 is the heat transfer due to conduction, where k is the thermal conductivity, A is the cross-sectional area where conduction occurs, T 1 is the temperature of the object losing heat, and T 2 is the temperature of the object receiving heat; q 放射 is the heat transfer due to radiation, where σ is the Boltzmann constant, ε is Weighting the average heat emissivity, A is the surface area, T 1 is the temperature of the surface, and T 2 is the temperature of the object or environment receiving heat.

[0016]

[0031] Consider a situation where the ambient temperature is lower than body temperature. Since clothing and footwear materials are worn in contact with the body as a heat source and there is some conductive heat transfer between the body and the materials worn thereon, the temperature difference (ΔT) between the body and the adjacent material is typically smaller than the ΔT between the outermost material layer and the environment. Therefore, a change in the material that restricts heat transfer between the outermost material layer and the environment may have a greater effect on the overall heat retention than a change that restricts heat transfer between the body and the innermost or adjacent material layer.

[0017]

[0032] Attaching a material with a low emissivity, such as a metal, to the outermost material layer can limit radiative heat transfer to the environment and provide improved heat retention for clothing and footwear. Therefore, aluminum can be used for this purpose. However, aluminum may oxidize and wear away when exposed to the environment and during use in the outermost layer of clothing. The emissivity of a material's surface is its effectiveness in radiating energy as heat radiation. Quantitatively, emissivity is the ratio of the heat radiation emitted by the surface to the radiation that would be emitted by an ideal blackbody surface at the same temperature obtained by the Stefan-Boltzmann law. The ratio varies from 0 to 1 (e.g., 100%), where the surface of a perfect blackbody radiator has an emissivity of 1, while a surface that simply reflects heat radiation from its surroundings has an emissivity of 0.

[0018]

[0033] A protective polymer layer on top of a metal surface, such as aluminum, can protect the metal surface and prevent oxidation and wear. Unfortunately, the polymer coating has a high emissivity, which negates the effect of placing a metal with a low emissivity on the outside of clothing for the purpose of minimizing radiative heat loss to the surroundings and thereby enhancing the heat retention of the clothing. From these findings in conventional wisdom, as is the case with clothing using Omni-Heat (trademark) reflective technology, metal elements are placed inside the clothing.

[0019]

[0034] Contrary to this conventional wisdom, the inventors disclose herein a multi-layer configuration of a metal (e.g., aluminum) and a polymer overlayer that cooperatively achieve a multi-layer thermal management element having a low emissivity as compared to the substrates used in clothing fabric construction. As will be described in detail in the following examples, testing of this multi-layer configuration surprisingly shows that this multi-layer thermal management element has an emissivity of approximately 0.1 (e.g., 10%) (since emissivity is on a scale of 0 to 1, 0.1 is a low value), e.g., 0.07 to 0.13 (e.g., 7% to 13%) of Weighting average emissivity. These multi-layer thermal management elements were bonded to the outside of various substrates and tested using a standard hot plate method. Even at a surface coverage of 30%, the multi-layer thermal management elements increased the thermal resistance of the various substrates by 20 to 67% (see Table 1), which is remarkable and surprising.

[0020]

[0035] Furthermore, by adding a colorant to the protective polymer overlayer, absorption of solar radiation occurs and the heat retention ability of the multi-layer elements can be improved, thereby making them multifunctional. For example, a black colorant can result in a maximum solar light absorption rate (e.g., the absorption rate of energy at wavelengths of 0.3 to 2.5 μm), and as a result, when the sun's light is present as direct sunlight or scattered sunlight, the multi-layer and multifunctional thermal management elements, when attached to the outer surface of the clothing fabric, achieve significantly improved heat retention. At a surface coverage of 55%, the multi-layer thermal management elements increased the thermal resistance of the various substrates by 15 to 73% (see Table 2), which is remarkable and surprising. Additionally, as demonstrated by the results shown in FIG. 14, the multi-layer thermal management elements surprisingly absorb more heat, conduct that heat to the substrate and underlying insulation to which the multi-layer thermal management elements are bonded, and maintain that heat longer than a substrate having a similar solar light absorption rate, and can function as a solar collector.

[0021]

[0036] Since black colorants are typically radioactive, one of ordinary skill in the art can predict that the increased absorption rate is offset by the increased thermal emissivity of the black colorant (e.g., emissivity at wavelengths of 5-40 μm). However, surprisingly, testing has shown that this is not the case. Even with a black colorant in the polymer top layer, the multilayer thermal management element still reduces the overall average thermal emissivity of the base fabric, which leads to an improvement in heat retention. In another embodiment, a photochromic colorant that changes from transparent to colored, such as black, when exposed to sunlight can be used in the polymer top layer to achieve both a maximally low emissivity when not exposed to sunlight and a maximized sunlight absorption rate when exposed to sunlight. Photochromic colorants can be classified as type P or type T. Type P photochromic colorant systems can be switched in each direction by different wavelengths of light. Type P systems change color when irradiated in a specific wavelength range and remain in this state after the stimulus is removed. They only return to their original color when a different set of wavelengths of light is applied to the type P system. Alternatively, type T behavior is seen when light can cause a change in only one direction. Type T systems can return to their original state by a thermal reverse reaction when they are no longer exposed to the light source. Reversibility is an important aspect of both types of photochromism, and for example, a photosensitive material that undergoes an irreversible change is not considered photochromic. Real-world colorants may not always exactly match the strict definitions of the above two types of behavior, but most can be easily classified. Examples of type T colorants of the present disclosure include, but are not limited to, spirooxazine, spirooxazine, and naphthopyran. Examples of type P colorants of the present disclosure include, but are not limited to, diarylethene and fugides.

[0022]

[0037] Referring to FIG. 1, the disclosed thermal management material 10 includes a base fabric 20 having an outer surface 12 (e.g., the surface of the material facing outward with respect to the wearer's body) and an inner surface 13 (e.g., the surface of the material facing inward with respect to the wearer's body), which can have one or more performance characteristics. As disclosed herein, the inner surface 13 can be understood to be closer to the wearer's body of the thermal management material 10 compared to the outer surface 12. A plurality of multilayer multifunctional thermal management elements 15 are coupled to the outer surface 12 of the base fabric, and the arrangement and spacing of the plurality of multilayer multifunctional thermal management elements leave a portion of the base fabric uncovered, enabling the substrate to retain at least a partial performance of the performance characteristics. These multilayer multifunctional thermal management elements 15 are specifically developed as disclosed herein to achieve a thermal management material 10 that can hold heat, absorb solar radiation, and is better than the base fabric 20 without the multilayer multifunctional thermal management elements 15, having a high solar light absorption rate at wavelengths of 0.340 - 2.5 μm and a low thermal emissivity at wavelengths in the range of 5 - 40 μm, such as a fabric.

[0023]

[0038] In an embodiment, each multilayer multifunctional thermal management element 15 has a low thermal emissivity layer 16. In an embodiment, the low thermal emissivity layer 16 of the multilayer multifunctional thermal management element 15 is a discontinuous arrangement of foils such as metal foils (e.g., malleable metals, including but not limited to aluminum, copper, tin, silver, and gold), which is aluminum foil in a specific embodiment. In addition to the low thermal emissivity layer 16, the multilayer multifunctional thermal management element 15 includes a high solar light absorption rate layer 18 disposed on the outermost surface of the thermal management element 15, for example, covering the upper part of the surface facing outward of the low thermal emissivity layer 16. For reference, "facing outward" is exemplified by the direction indicated by arrow 21 in FIG. 1. The multilayer multifunctional thermal management element 15 may include additional layers such as a release layer, an adhesive layer, and a protective layer against wear and oxidation. However, the layer thickness is such that the multilayer multifunctional thermal management element is bonded to the fabric on the outer surface. WeightingIt must be kept thin enough so that the average emissivity does not return to and increase at the level of the fabric itself. In an embodiment, the multi-layer multifunctional thermal management element 15 has an average thermal emissivity of 0.1 to 0.85 (e.g., 10% to 85%), preferably less than 0.7, and most preferably less than 0.5. Weighting In an embodiment, the thermal management material 10 to which the multi-layer multifunctional thermal management element 15 is bonded to the outer surface has an average thermal emissivity of less than 0.9 (e.g., 90%), preferably less than 0.7 (e.g., 70%), and most preferably less than 0.5 (e.g., 50%). Weighting In an embodiment, the thermal management material 10 has an emissivity of about 0% to about 80%, such as about 15 to 65%, about 30 to 80%, about 10 to 50%, 30 to 70%, or about 40 to 60%. Thus, as used herein, a low thermal emissivity layer refers to a layer that provides the multi-functional thermal management element (e.g., the multi-functional thermal management element 15) with an average thermal emissivity of 0.1 to 0.85, preferably less than 0.7, and most preferably less than 0.5, and / or provides the thermal management material (e.g., the thermal management material 10) with an average thermal emissivity of less than 0.9, preferably less than 0.7, and most preferably less than 0.5. Weighting In an embodiment, the multi-layer multifunctional thermal management element 15 has an average solar absorptance of at least 50% (e.g., 0.5), such as greater than 50%, greater than 55% (e.g., 0.55), greater than 60% (e.g., 0.60), greater than 65% (e.g., 0.65), greater than 70% (e.g., 0.70), greater than 75% (e.g., 0.75), greater than 80% (e.g., 0.80), greater than 85% (e.g., 0.85), or even greater than 90% (e.g., 0.90). Weighting In an embodiment, the thermal management material 10 to which the multi-layer multifunctional thermal management element 15 is bonded to the outer surface has an average solar absorptance of at least 50%, such as greater than 50%, greater than 55%, greater than 60%, greater than 65%, greater than 70%, greater than 75%, greater than 80%, greater than 85%, or even greater than 90%.

[0024]

[0039] In an embodiment, the multi-layer multifunctional thermal management element 15 has an average solar absorptance of at least 50% (e.g., 0.5), such as greater than 50%, greater than 55% (e.g., 0.55), greater than 60% (e.g., 0.60), greater than 65% (e.g., 0.65), greater than 70% (e.g., 0.70), greater than 75% (e.g., 0.75), greater than 80% (e.g., 0.80), greater than 85% (e.g., 0.85), or even greater than 90% (e.g., 0.90). Weighting In an embodiment, the thermal management material 10 to which the multi-layer multifunctional thermal management element 15 is bonded to the outer surface has an average solar absorptance of at least 50%, such as greater than 50%, greater than 55%, greater than 60%, greater than 65%, greater than 70%, greater than 75%, greater than 80%, greater than 85%, or even greater than 90%. WeightingShows the average solar absorptance. As used herein, the absorptance discussed refers to the ratio of the absorbed light to the incident light, and thus the absorptance is on a scale of 0 to 1, where a value of 1 means that all of the incident light is absorbed. Further, as disclosed herein, a high solar absorptance layer has an average solar absorptance of at least 0.5, or at least 0.55, or at least 0.6, or at least 0.65, or at least 0.7, or at least 0.75, or at least 0.80, or at least 0.85, or at least 0.90 in a multilayer multifunctional thermal management element (e.g., multilayer multifunctional thermal management element 15), and / or in a thermal management material (e.g., thermal management material 10). Weighting Gives an average solar absorptance of at least 0.5, or at least 0.55, or at least 0.6, or at least 0.65, or at least 0.7, or at least 0.75, or at least 0.80, or at least 0.85, or at least 0.90 in a thermal management material (e.g., thermal management material 10), and / or is a layer (e.g., high solar absorptance layer 18) that gives an average solar absorptance of at least 0.5, or at least 0.55, or at least 0.6, or at least 0.65, or at least 0.7, or at least 0.75, or at least 0.80, or at least 0.85, or at least 0.90. Weighting Is a layer (e.g., high solar absorptance layer 18) that gives an average solar absorptance of at least 0.5, or at least 0.55, or at least 0.6, or at least 0.65, or at least 0.7, or at least 0.75, or at least 0.80, or at least 0.85, or at least 0.90.

[0025]

[0040] In an embodiment, the multilayer multifunctional thermal management element 15 is relatively small, such as a dot with a diameter of 0.1 to 10 mm, so as not to overly interfere with the performance characteristics of the base fabric 20. Thus, in various embodiments, a plurality of multilayer multifunctional thermal management elements 15 coupled to the outer-facing surface of the base fabric 20, such as the outer-facing surface of the outermost layer of a clothing item, can be used. For example, a base fabric 20 for body gear is disclosed. In one embodiment, the discontinuous pattern of the multilayer multifunctional thermal management element 15 manages body heat by absorbing solar radiation while reducing the radiation of radiant heat returning from the surface of the outermost layer of the clothing item to the environment.

[0026]

[0041] In an embodiment, the plurality of multilayer multifunctional thermal management elements 15 are generally arranged in a discontinuous array on the surface of the substrate 20 facing outward, whereby a portion of the substrate 20 is exposed between adjacent multilayer multifunctional thermal management elements 15. In various embodiments, the multilayer multifunctional thermal management elements 15 may be arranged in an array of spaced-apart elements, while in other embodiments, which will be discussed at greater length below, the multilayer multifunctional thermal management elements 15 may be arranged in a pattern of interconnected elements. In some embodiments, the multilayer multifunctional thermal management elements 15 may take the form of solid shapes or closed-loop members, such as circular, square, hexagonal, or other shapes including irregular shapes. In other embodiments, the discontinuous pattern of the multilayer multifunctional thermal management elements 15 may take the form of a lattice, grid, or other interconnected pattern.

[0027]

[0042] Generally, sufficient surface area of the surface of the substrate 20 facing outward should be exposed to achieve the desired performance characteristics or functions of the substrate (e.g., stretchability, drapability, handfeel, breathability, water vapor transfer, air permeability, and / or wicking). For example, if the exposed substrate is too small, properties such as water vapor transfer and / or air permeability may be impaired to an unacceptable degree in terms of the percentage of coverage. As used herein, the term "surface coverage area" refers to a measurement obtained from a unit cell, which may be, for example, a region containing a plurality of multilayer multifunctional thermal management elements. In one example, the unit cell is a unit cell of at least 1 inch × 1 inch at a given point in a fabric of a discontinuous array of multilayer multifunctional thermal management elements, and does not necessarily correspond to the percentage of the entire clothing item covered by the multilayer multifunctional thermal management elements. For example, a 1 inch × 1 inch unit cell (25.4 mm × 25.4 mm unit cell), a 2 inch × 2 inch unit cell (50.8 mm × 50.8 mm unit cell), a 3 inch × 3 inch unit cell (76.2 mm × 76.2 mm unit cell), etc. In one example, the unit cell may be the entire outer surface of the material measured from seam to seam of a given clothing item.

[0028]

[0043] The multi-layer multifunctional heat management element 15 covers a sufficient surface area of the surface facing outward of the base fabric 20 in order to obtain a desired degree of heat management (e.g., mitigation of thermal radiation or absorption of solar radiation when exposed even to direct sunlight or indirect sunlight, or both mitigation of thermal radiation and absorption of solar radiation). A sufficient surface area of the surface facing outward of the base fabric 20 may be exposed in order to achieve or maintain desired performance characteristics or functions of the base fabric (e.g., breathability, water vapor or air permeability, or wicking property). In various embodiments, the multi-layer multifunctional heat management element 15 may cover a sufficient surface area of the base fabric 20 to achieve a desired degree of heat management. For example, in a specific unit cell such as a 1-inch × 1-inch unit cell (a 25.4 mm × 25.4 mm unit cell), in various embodiments, the surface coverage area of the multi-layer multifunctional heat management element 15 is, for example, about 5 to 95%, about 10 to 90%, about 20 to 80%, 30 to 70%, 40 to 60%, or about 55%. In a given article, or even in a part of an article, the surface area coverage rate by the multi-layer multifunctional heat management element may be consistent or various within the area of the article or over the entire area of the article.

[0029]

[0044] In an embodiment, each of the multilayer multifunctional thermal management elements 15 has a diameter of about 1 mm, although larger and smaller sizes are conceivable. In an embodiment, each of the multilayer multifunctional thermal management elements 15 is within the range of about 0.1 mm to about 10.0 mm in diameter, for example, about 0.1, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, 7.0, 7.5, 8.0, 8.5, 9.0, 9.5, or 10.0 mm, or any value or range therein. In an embodiment, the individual multilayer multifunctional thermal management elements 15 in a particular region are spaced at intervals of about 0.1 to about 10.0 mm, for example, about 0.1, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, 7.0, 7.5, 8.0, 8.5, 9.0, 9.5, or 10.0 mm, or any value or range therein. As used herein, the diameter is the average distance from the center of the multilayer multifunctional thermal management element 15 regardless of its shape, for example, the geometric center of the multilayer multifunctional thermal management element 15, such as the center of a circular, triangular, square, polygonal, etc., or irregular shape. One of ordinary skill in the art can determine the geometric center of a certain shape.

[0030]

[0045] In an embodiment, the low-emissivity layer 16 of each of the multilayer multifunctional thermal management elements 15 has a thickness within the range of about 5 nm to about 100 nm, for example, a thickness such as about 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, or 100 nm, or a thickness of any value or conceivable partial range, and includes or consists of a metal foil, such as an aluminum foil.

[0031]

[0046] In an embodiment, the high solar absorptance layer 18 is a polymer or a mixture of polymers having a thickness in the range of about 0.1 μm to about 10.0 μm, such as about 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, 7.0, 7.5, 8.0, 8.5, 9.0, 9.5, or 10.0 μm, or any value or sub-range may also be considered. Examples of polymers relevant to the present disclosure include, but are not limited to, polyethylene, polypropylene, polystyrene, poly(tetrafluoroethylene), polyisobutylene, polyacrylonitrile, polybutadiene, poly(vinyl chloride), poly(methyl acrylate), poly(methyl methacrylate), polybutadiene, polychloroprene, poly(cis-1,4-isoprene), poly(trans-1,4-isoprene), polyurethane, polyester, polyamide, polyether, polyolefin, polyacrylate, poly(3-hydroxybutyric acid) (PHB), poly[(R)-3-hydroxybutyrate-co-(R)-3-hydroxyvalerate] (PHBV), 3-hydroxybutyrate and 3-hydroxyhexanoate (PHBH), poly-lactic acid (PLA), cellulose, chitin, lacquer, and natural rubber, or their copolymers or combinations. In an embodiment, the high solar absorptance layer 18 includes a colorant, such as a colorant that aids in the absorption of solar energy. In one example, the colorant is a black colorant. In certain embodiments, the high solar absorptance layer 18 is present only on the outer surface of the multilayer multifunctional thermal management element 15. In other embodiments, the high solar absorptance layer 18 may at least partially cover a portion of the base fabric to which the individual multilayer multifunctional thermal management elements 15 are not attached, for example, as a coating on top of both the low emissivity layer 16 and the base fabric 20.

[0032]

[0047] The multi-layer multifunctional thermal management element 15 is disposed on the outer surface of the body gear and / or the outermost surface of the base fabric 20 so that they are exposed to the environment, which enables the multi-layer multifunctional thermal management element 15 to, for example, reduce heat radiation to the environment and absorb solar radiation, while allowing the base fabric 20 to fully perform its desired function. In some embodiments, the multi-layer multifunctional thermal management element 15 can perform these functions without adversely affecting the drape, feel, or other properties of the base fabric. According to various embodiments, the base fabric 20 may be part of any form of bodywear, blanket, tent, rainfly, sleeping bag, or any material or device for which thermal management is desired. As used herein, bodywear includes, but is not limited to, sports wear such as compression garments, T-shirts, shorts, tights, sleeves, headbands, etc., outdoor clothing such as jackets, pants, leggings, shirts, gloves, hats, etc., and footwear, and any other thing worn on the body.

[0033]

[0048] In various embodiments, the multi-layer multifunctional thermal management element 15 may be disposed on the surface of the base fabric 20 facing outward that has one or more desired properties or characteristics. In some embodiments, the base fabric 20 may have other desirable properties such as abrasion resistance, antistatic property, antibacterial activity, water repellency, anti-inflammatory property, hydrophilicity, hydrophobicity, wind resistance, sunlight protection, SPF protection, recoverability, stain resistance, wrinkle resistance, etc. In other embodiments, the spacing between the thermal management elements 15 helps to enable the outer surface of the base fabric 20 to have the desired drape, appearance, and / or texture. Suitable base fabrics 20 include nylon, polyester, polypropylene, rayon, cotton, spandex, wool, silk, or blends thereof, or any other material having the desired appearance, feel, weight, thickness, folding method, structure, texture, or other desired properties. In various embodiments, by leaving a specified percentage of the base fabric uncoated by the multi-layer multifunctional thermal management element 15, that portion of the base fabric 20 may be able to perform its desired function.

[0034]

[0049] In various embodiments, a single layer of substrate 20 may be used, including a substrate 20 having an outer surface on which the multi-layer multifunctional thermal management element 15 is disposed. On the other hand, in other embodiments, a multi-layer fabric including a layer of substrate 20 bonded to one or more other layers may be used. In this case, the substrate 20 is an outer layer having an outer surface on which the multi-layer multifunctional thermal management element 15 is disposed, for example, an overlying thermal insulation layer. In certain embodiments, the individual multi-layer multifunctional thermal management elements 15 are individually bonded to the substrate, such as by gluing, and / or joined to the substrate. In certain embodiments, the multi-layer multifunctional thermal management element 15 is directly bonded to the substrate.

[0035]

[0050] In various embodiments, the multilayer multifunctional thermal management element 15 may be permanently attached to the substrate 20 in various ways, including but not limited to gluing, heat pressing, printing, or sewing. In some embodiments, the multilayer multifunctional thermal management element 15 may be attached to the substrate 20 by frequency welding, such as by high frequency welding or ultrasonic welding. In some embodiments, the multilayer multifunctional thermal management element 15 may be attached to the substrate using gravure printing. In some specific, non-limiting examples, the gravure printing method can use an engraved roller rotating in an adhesive bath that contains an adhesive material (e.g., an adhesive that will bond the multilayer multifunctional thermal management element 15 to the substrate) in the engraved dots or lines of the roller. Excess adhesive on the roller can be wiped off using a blade, and then the adhesive can be attached to the foil containing the multilayer multifunctional thermal management material on the carrier material as it passes between the engraved roller and the pressure roller. The multilayer multifunctional thermal management material is placed on the carrier material such that the high solar absorptance layer is closer to the carrier material than the low thermal emissivity layer, and the adhesive is applied to the surface opposite the carrier material. In various embodiments, the gravure printing methods can include direct gravure printing, reverse gravure printing, or differential offset gravure printing, and in various embodiments, the adhesive weight can be controlled by the percent solids, the gravure print volume, the pattern depth, and / or the speed of the gravure printing cylinder. Following the application of the adhesive to the foil by gravure printing, a substrate (e.g., the substrate 20) is laminated to the adhesive-containing foil. The laminate is then pressed and cured in a continuous process, and then the carrier material is removed, leaving the multilayer multifunctional thermal management element 15 on the substrate in a pattern that matches the pattern engraved on the gravure printing roller.

[0036]

[0051] In various embodiments, the multilayer multifunctional thermal management element 15 may be applied in a pattern or in a continuous or discontinuous array. For example, as shown in FIGS. 15A - 15H, the thermal management element may take the form of an array of individual solid or closed - loop members adhered to or otherwise fixed to the substrate in a desired pattern. Such a configuration has been found to provide thermal insulation to the user while allowing the substrate to still exhibit the desired properties (e.g., breathability and stretchability). In various embodiments, such discontinuous, individual, spaced - apart multilayer multifunctional thermal management elements may take the form of circles, triangles, squares, pentagons, hexagons, octagons, stars, crosses, crescents, ellipses, or any other suitable shape.

[0037]

[0052] The embodiments shown in FIGS. 15A - 15H show the multilayer multifunctional thermal management element as discrete, individual elements, but in some other embodiments, some or all of the multilayer multifunctional thermal management elements may be arranged such that they are connected to each other, such as in stripes, wavy lines, or matrix / lattice patterns, or any other pattern that allows for partial coverage of the substrate. For example, as shown in FIGS. 16A - 16F, the configuration of the multilayer multifunctional thermal management element attached to the substrate may be in the form of various partially or fully connected elements, and the pattern may combine both discontinuous elements (such as those shown in FIGS. 15A - 15H) and geometric patterns that are connected to each other (such as those shown in FIGS. 16A - 16F). In various embodiments, the pattern of the multilayer multifunctional thermal management element may be symmetric, regular, random, and / or asymmetric. Further, as discussed below, the pattern of the multilayer multifunctional thermal management element may be placed on the substrate in strategic locations to improve the performance of the bodywear. In various embodiments, the size and / or spacing of the multilayer multifunctional thermal management element may also vary in different regions of the bodywear in order to balance the need for improved thermal insulation properties in specific regions while maintaining the function of the substrate.

[0038]

[0053] In various embodiments, the location, pattern, and / or coverage rate of the multilayer multifunctional thermal management element may vary. Naturally, the location and ratio of the coating can be changed according to the type of clothing. In some embodiments, the degree of coating by the multilayer multifunctional thermal management element may gradually vary as needed across the entire clothing item. In various embodiments, the pattern of the multilayer multifunctional thermal management element may be symmetric, regular, random, and / or asymmetric. Further, as discussed below, the pattern of the multilayer multifunctional thermal management element may be disposed on the outer surface of the base fabric at strategic locations to improve the performance of the bodywear. In various embodiments, the size of the multilayer multifunctional thermal management element may also vary in order to balance the need for improved thermal insulation properties while maintaining the functionality of the base fabric.

[0039] [Examples]

[0054] In various embodiments, the thermal management materials described herein can have better thermal management and insulation properties compared to other insulating materials that do not have the thermal management materials disclosed herein.

[0040]

[0055] ASTM G173 describes the solar spectrum at the Earth's surface. The proportion of the total solar power in the UV region is 3.2% (UVA and UVB, 0.28 - 0.38 μm), 53.4% in the visible region (0.38 - 0.78 μm), and 43.4% in the IR region (0.78 - 3.0 μm). Substantially all solar energy is contained at wavelengths <2.5 μm (see Figure 2).

[0041]

[0056] The Planck distribution shows the radiation emitted by a blackbody surface at a given absolute temperature (see Figure 3). At typical surface temperatures (0 - 70 °C), the peak radiation is at approximately 10 μm. The surface radiation is significantly lower in intensity than solar irradiation but is much broader than solar irradiation. At a nominal skin temperature of 35 °C, approximately 95% of the radiant energy from the blackbody is contained within the spectral region of 5 ≤ λ ≤ 40 μm.

[0042]

[0057] Thermal emissivity, or emissivity, is an indicator of an object's ability to radiate thermal energy. The value of emissivity varies from 0 to 1. Metals tend to exhibit low thermal emissivity and high thermal reflectivity. Polymers tend to exhibit high thermal emissivity and low thermal reflectivity.

[0043]

[0058] In a given object, the measured emissivity is determined by the material properties of its surface. In fact, it is common to increase the emissivity of a metal object by painting it black, because the paint is a polymer coating and the black colorant typically absorbs and radiates more infrared thermal radiation than other colorants. This is demonstrated by the test shown in FIG. 4. A metal plate 401 was placed on a hot plate 405 painted black to create a high-emissivity surface. A tape piece of high-emissivity black insulating tape 406 (the tape is a polymer film with an adhesive layer) was placed on the metal plate 401. This configuration was imaged using an infrared (IR) thermal imaging camera 410 on a stand 412 that directly measures the radiosity, which is generally proportional to the thermal emissivity. This radiosity is converted to temperature using the internal software of the camera according to Planck's distribution, and the results are typically reported as temperature, or apparent temperature. At a given emissivity setting of the IR camera, the thermal emissivity of an object maintained at the same actual temperature will be proportional to the apparent temperature measured by the camera. The hot plate was set to approximately 37° C. and a thermal image was measured. A thermocouple was used to confirm the temperature of the hot plate (see arrow 415), and the metal plate (see arrow 418) was approximately 37° C. (see FIG. 4).

[0044]

[0059] The results of this test are shown in Fig. 5. The processing area 502 is masked, which is due to the reflection of the thermal imaging camera (e.g., camera 410 in Fig. 4) on the metal plate 401 (note how in Fig. 4 the location of the camera is right above the metal plate). The painted black hot plate 405 (corresponding to 405a in Box 2) appears to have an apparent temperature of 36.5 °C, which is consistent with the actual temperature measured using a thermocouple. In contrast, the metal plate 401 (corresponding to 401a in Box 1) appears to have an apparent temperature of 22.4 °C, which is much lower than the actual temperature measured using a thermocouple, indicating that the metal plate emits less thermal energy than the area painted black. Therefore, when the outermost surface of an object is metal, it is predicted that the object will exhibit a low emissivity and retain more heat, as opposed to losing thermal energy by radiation to its surroundings. This is further demonstrated in Fig. 5 by placing a small piece of the black insulating tape 406, which is a thin polymer film with an underlying adhesive layer, on the metal plate 401. The apparent temperature of the black insulating tape (corresponding to 406a in Box 3) is 36.8 °C, which also coincides with the actual temperature of the metal plate measured using a thermocouple. When the outermost surface of an object is polymer, it is predicted that the object will exhibit a high emissivity, which leads to a greater radiative heat loss.

[0045]

[0060] As shown in FIGS. 6, 7, 9, and 10, the thermal management elements (FIGS. 6 and 7) and the thermal management elements coupled to the fabric surface (FIGS. 9 and 10) were tested to measure the thermal emissivity and solar absorptance. Using a Laboratory Portable SpectroReflectometer (LPSR) 300 spectrophotometer, spectral measurements were generally made in accordance with ASTM E903 over the range of sunlight that constitutes the ultraviolet, visible, and near-infrared (UV / Vis / NIR) wavelength range (0.25 < λ < 2.5 μm). Using a Nicolet iS50 Fourier transform infrared (FTIR) spectrophotometer with a Pike Upward MID integrating sphere, spectral measurements were generally made in accordance with ASTM E408 over the thermal range of mid-infrared (MIR) of 2.5 - 40 μm. The average spot size for each measurement was approximately a rectangular spot of 7.6 mm × 2 mm for UV / Vis / NIR (0.25 - 2.5 μm) and approximately an elliptical spot of 8.5 mm × 7.5 mm for MIR (2.5 - 40 μm). In both devices, the measurement spot size was determined to be large enough with respect to the thermal management element when affixed to the fabric surface such that the measurement represents the average of the spectral response of the multi-material (i.e., fiber and element) fabric surface. This was verified by considering the deviation between the measured values of three samples taken at various positions in each device. The thermal management elements were measured on cardboard.

[0046]

[0061] Reflectance and transmittance measurements were made. From energy conservation, since reflectance (ρ(λ)) + transmittance (τ(λ)) + absorptance (α(λ)) = 1, the absorptance of an object can be calculated from its measured spectral reflectance and spectral transmittance. By Kirchhoff's law, the spectral emissivity (ε(λ)) is equal to the spectral absorptance (α(λ)). The fabric and cardboard are nominally opaque for 5 ≦ λ ≦ 40 μm (i.e., τ = 0), and thus α(λ) = 1 - ρ(λ) = ε(λ).

[0047] Weighting The average thermal emissivity is,

Equation

[0048] Weighting The average solar absorptance is

Equation

[0049]

[0062] Referring to FIGS. 6, 7, 9, and 10, samples containing a multilayer management element in which a thin black polymer layer is the outermost layer on a thin metal layer result in a lower thermal emissivity than a purely black polymer thermal management element. This was a surprising result that was not predicted.

[0050]

[0063] Specifically, FIG. 6 illustrates the thermal emissivity versus wavelength of various thermal management elements including a silver thermal management element (line 605) (e.g., the high solar absorptance layer does not contain a colorant), the multilayer multifunctional thermal management element of the present disclosure (line 610), and a black polymer thermal management element (line 615) (e.g., a pure black polymer thermal management element without metal). In the example shown in FIG. 6, the multilayer multifunctional thermal management element (line 610) included a black metal multilayer multifunctional thermal management element. Specifically, the low emissivity layer (e.g., the low emissivity layer 16 in FIG. 1) contained metal, and the high solar absorptance layer (e.g., the high solar absorptance layer 18 in FIG. 1) contained a black colorant in the polymer upper layer. The silver thermal management element (line 605) showed an average thermal emissivity of 10.3%, Weighting the black metal multilayer multifunctional thermal management element (line 610) showed an average thermal emissivity of 53.8%, Weighting the black polymer thermal management element (line 615) showed an average thermal emissivity of 91.3%. Weighting showed an average thermal emissivity.

[0051]

[0064] Figure 7 illustrates the thermal emissivity versus wavelength for the various thermal management elements discussed above with respect to FIG. 6, including a silver thermal management element (line 705), a multilayer multifunctional thermal management element (line 710), and a black polymer thermal management element (line 715). As discussed above with respect to FIG. 6, the multifunctional thermal management element included a black metal multilayer multifunctional thermal management element. The silver thermal management element (line 705) exhibited an average absorptance of 17.1%, Weighting the multilayer multifunctional thermal management element (line 710) exhibited an average absorptance of 91.5%, Weighting and the black polymer thermal management element (line 715) exhibited an average thermal emissivity of 93.5%. Weighting

[0052]

[0065] Figure 9 shows the thermal emissivity versus wavelength for two different fabrics: a black base fabric (line 905) and the same black base fabric (line 910) with the multilayer multifunctional thermal management element of the present disclosure bonded thereto covering 55% of the surface. With respect to FIG. 9, the multifunctional thermal management element included the same black metal multilayer multifunctional thermal management element as discussed above with respect to FIGS. 6 and 7. The black base fabric without the multifunctional thermal management element (line 905) exhibited an average emissivity of 93.5%. Weighting The black base fabric with the multilayer multifunctional thermal management element bonded thereto (line 910) exhibited an average emissivity of 68.3%. Weighting

[0053]

[0066] Figure 10 shows the solar absorptance versus wavelength for the two different fabrics discussed above with respect to FIG. 9, specifically a black base fabric (line 1005) and the same black base fabric (line 1010) with the multilayer multifunctional thermal management element of the present disclosure bonded thereto covering 55% of the surface. The black base fabric without the multifunctional thermal management element (line 1005) exhibited an average absorptance of 91.9%. Weighting The black base fabric with the multilayer multifunctional thermal management element (line 1010) bonded thereto exhibited an average absorptance of 92.0%. Weighting

[0054]

[0067] Using the standard hot plate method, generally in accordance with ASTM F-1868, Part A: Dry Heat Transport, under the following conditions: T プレート = 35 °C, T a周囲The thermal resistance was measured at 20°C, relative humidity = 65%, and wind speed = 1 m / s. Table 1 shows the results for six different fabrics with silver foil laminated on the fabric surface. For each fabric, the thermal resistance is significantly higher when the silver foil is on the outermost surface of the fabric and facing away from the heat source. For a given fabric, the thermal resistance increases as the surface coverage rate of the silver foil increases.

[0055]

[0068]

Table 1

[0056]

[0069]

Table 2

[0057]

[0070] Among the multilayer management elements of the present disclosure on the fabric, those in which a thin polymer layer (e.g., a thin black polymer layer) is the outermost layer result in improved heat retention. This is a surprising result that was not predicted. In addition to improving the heat retention of the base fabric in the absence of incident solar radiation, when solar radiation increases the heat input due to the absorption rate of the black outer layer and conduction to the heat management material, the further result shows even more improved heat retention.

[0058]

[0071] To determine the effect of material and environmental parameters on the relative importance of the thermal emissivity and solar absorptivity of fabrics in insulation, a thermal model (Figure 11A) and a thermal resistance network (Figure 11B) were developed. The variable parameters of the model include the thermal emissivity of the fabric surface, the solar absorptivity of the fabric surface, the thermal resistance of the fabric, the air gap between the fabric and the skin, the ambient temperature, the proportion of incident sunlight (i.e., the percentage of solar radiant energy reaching the surface of the clothing item), the wind speed, and the activity level. Some of the results of the thermal model are shown in Figure 12 as heat to the skin versus the proportion of solar energy reaching the fabric for three different fabrics: a black base fabric (line 1205), the same black base fabric with a 50% silver thermal management element on the outermost surface (line 1210), and the same black base fabric with a 50% multilayer black thermal management element of the present disclosure on the outermost surface (line 1215). When the proportion of sunlight reaching the fabric is zero, the fabric with the silver thermal management element on the outermost surface retains the most heat. This is consistent with the thermal resistance measurements (see Table 1). However, at a sunlight proportion exceeding about 3% (illustrated by arrow 1220), the fabric with the multilayer black thermal management element on the outermost surface retains the most heat. From a state with no sunlight to the maximum proportion of sunlight, across the range of the proportion of total sunlight, the fabric with the multilayer multifunctional black thermal management element on the outermost surface retains more heat than the single black fabric. This is consistent with the low emissivity and high solar absorptivity multifunctionality of the multilayer thermal management element and is consistent with the thermal resistance measurements (see Table 2 and Figure 12).

[0059]

[0072] Figure 13 shows a schematic configuration of an experiment conducted to determine the heat confined by a black base fabric and the same black base fabric with a multilayer multifunctional thermal management element (HME, illustrated as black dots in Figure 13) combined to cover 55% of the surface. Two fabrics are placed adjacent to each other on top of two layers of fibrous insulation (80 gsm per layer). Thermocouples (tc a and tc b ) are placed under each fabric (tc c and tc d) was placed. The hot plate was set near the deep body temperature (37 °C), and the overall configuration was placed in a low-temperature room at 4 °C. A Sunlite ENH 250 watt / MR16 clear glass sphere, represented by the sun in the schematic diagram and used to simulate solar radiation, was placed approximately 23 cm above the cloth surface.

[0060]

[0073] Figure 14 is a graph of data collected using the experimental configuration shown in Figure 13. Before exposure to the simulated solar radiation, the steady-state temperature under the base fabric containing the multi-layer multifunctional heat management element (HME) is higher than the steady-state temperature under the same base fabric without the HME, even inside the insulation layer. This result demonstrates that more heat is trapped under the cloth containing the HME. After turning on the light to simulate exposure to solar radiation, the temperature under the base fabric containing the HME rises higher than the temperature under the same base fabric without the HME, even inside the insulation layer. Furthermore, after turning off the light, the heat absorbed and conducted to the cloth / insulation laminate is retained longer under the base fabric containing the HME, even inside the insulation layer, than the heat absorbed and conducted under the same base fabric without the HME. This was a surprising result considering that the solar light absorption rate values of the black HME and the black cloth are approximately the same. These results indicate that the HME functions surprisingly as a solar heat collector that absorbs more heat than a base fabric characterized by a similar solar light absorption rate, conducts it to the material, and maintains it longer.

[0061]

[0074] In certain embodiments herein, a thermal management material is discussed that includes a base fabric having an outer surface and an inner surface, and a plurality of multi-layer multifunctional heat management elements coupled to the outer surface of the substrate. In one example, each of the plurality of multi-layer multifunctional heat management elements may include a low thermal emissivity layer and a high solar light absorption rate layer, and the thermal management material Weighting has an average thermal emissivity of less than 0.8.

[0062]

[0075] In another embodiment, the article of bodywear includes a thermal management material, the thermal management material having a base fabric with an outer surface and an inner surface, and a plurality of multi-layer multifunctional thermal management elements bonded to the outer surface of the base material. In such an example, each of the plurality of multi-layer multifunctional thermal management elements may include a low thermal emissivity layer and a high solar absorptivity layer, and the thermal management material has an average thermal emissivity of less than 0.8 Weighting and having.

[0063]

[0076] In yet another embodiment, a method of manufacturing a thermal management material includes selecting a base fabric having an outer surface and an inner surface, and bonding one or more multi-layer multifunctional thermal management elements to the outer surface of the base fabric. In such an example, each of the one or more multi-layer multifunctional thermal management elements may include a low thermal emissivity layer and a high solar absorptivity layer.

[0064]

[0077] Although specific embodiments have been illustrated and described herein, those skilled in the art will appreciate that various alternative and / or equivalent embodiments or implementations that are intended to achieve the same purpose may be presented and described without departing from the scope and replaced with the embodiments presented and described. Those skilled in the art will readily appreciate that the embodiments may be implemented in a very broad manner. This application is intended to cover any modifications or variations of the embodiments discussed herein. Accordingly, it is clearly intended that the embodiments be limited only by the claims and their equivalents.

Claims

1. A base fabric having an outer surface and an inner surface, and a plurality of multi-layer multi-functional heat management elements bonded to the outer surface of the base fabric, the heat management material comprising: each of the plurality of multi-layer multi-functional heat management elements includes a low thermal emissivity layer and a high solar absorptivity layer, the heat management material has a weighted average thermal emissivity of less than 0.8, each of the plurality of multi-layer multi-functional heat management elements has a diameter of 0.1 mm to 10.0 mm, in each of the plurality of multi-layer multi-functional heat management elements, the high solar absorptivity layer is disposed outside the low thermal emissivity layer, and the high solar absorptivity layer provides a weighted average solar absorptivity of at least 0.5 to the multi-layer multi-functional heat management element, a heat management material.

2. The heat management material according to claim 1, wherein the heat management material has a weighted average solar absorptivity of at least 0.

5.

3. The heat management material according to claim 1 or 2, wherein the low thermal emissivity layer is a metal foil.

4. The heat management material according to any one of claims 1 to 3, wherein the low thermal emissivity layer has a thickness of 5 nm to 100 nm.

5. The heat management material according to any one of claims 1 to 4, wherein the high solar absorptivity layer has a thickness of 0.1 μm to 10.0 μm.

6. The heat management material according to any one of claims 1 to 5, wherein the high solar absorptivity layer includes a polymer upper layer.

7. The heat management material according to any one of claims 1 to 6, wherein the high solar absorptivity layer includes a colorant.

8. The heat management material according to claim 7, wherein the colorant is a black colorant.

9. A base fabric having an outer surface and an inner surface, and a plurality of multi-layer multi-functional heat management elements bonded to the outer surface of the base fabric, the heat management material comprising: each of the plurality of multi-layer multi-functional heat management elements includes a low thermal emissivity layer and a high solar absorptivity layer, the heat management material has a weighted average thermal emissivity of less than 0.8, the high solar absorptivity layer includes a colorant, the colorant is a black colorant, the colorant is a photochromic colorant that becomes colored from transparent when exposed to light, in each of the plurality of multi-layer multi-functional heat management elements, the high solar absorptivity layer is disposed outside the low thermal emissivity layer, and the high solar absorptivity layer provides a weighted average solar absorptivity of at least 0.5 to the multi-layer multi-functional heat management element, a heat management material.

10. A base fabric having an outer surface and an inner surface, and A thermal management material comprising a plurality of multi-layer multifunctional thermal management elements bonded to the outer surface of the base fabric, wherein each of the plurality of multi-layer multifunctional thermal management elements includes a low thermal emissivity layer and a high solar absorptivity layer, the thermal management material has a weighted average thermal emissivity of less than 0.8, in at least one 1-inch by 1-inch unit cell, the surface coverage area of the plurality of multi-layer multifunctional thermal management elements is 5% to 95% of the outer surface of the base fabric, in each of the plurality of multi-layer multifunctional thermal management elements, the high solar absorptivity layer is disposed outside the low thermal emissivity layer, and the high solar absorptivity layer provides a weighted average solar absorptivity of at least 0.5 to the multi-layer multifunctional thermal management element, a thermal management material.

11. The thermal management material according to any one of claims 1 to 10, wherein the surface coverage area of the plurality of multi-layer multifunctional thermal management elements varies between different regions of the thermal management material.

12. A base fabric having an outer surface and an inner surface, and a plurality of multi-layer multifunctional thermal management elements bonded to the outer surface of the base fabric, a thermal management material comprising: wherein each of the plurality of multi-layer multifunctional thermal management elements includes a low thermal emissivity layer and a high solar absorptivity layer, the thermal management material has a weighted average thermal emissivity of less than 0.8, a coat, jacket, shoes, boots, slippers, gloves, mittens, hat, scarf, trousers, socks, tent, backpack, sleeping bag, blanket, shirt, footwear, or a part of a pullover, in each of the plurality of multi-layer multifunctional thermal management elements, the high solar absorptivity layer is disposed outside the low thermal emissivity layer, and the high solar absorptivity layer provides a weighted average solar absorptivity of at least 0.5 to the multi-layer multifunctional thermal management element, a thermal management material.

13. A bodywear article comprising a thermal management material, wherein the thermal management material has a base fabric having an outer surface and an inner surface, and a plurality of multi-layer multifunctional thermal management elements bonded to the outer surface of the base fabric, wherein each of the plurality of multi-layer multifunctional thermal management elements includes a low thermal emissivity layer and a high solar absorptivity layer, in each of the plurality of multi-layer multifunctional thermal management elements, the high solar absorptivity layer is disposed outside the low thermal emissivity layer, and the high solar absorptivity layer provides a weighted average solar absorptivity of at least 0.5 to the multi-layer multifunctional thermal management element, the thermal management material has a weighted average thermal emissivity of less than 0.8, a bodywear article.

14. The bodywear article according to claim 13, wherein the heat management material has a weighted average solar absorptance of at least 0.

5.

15. The bodywear article according to claim 13 or 14, wherein the low emissivity layer is a metal foil.

16. The bodywear article according to any one of claims 13 to 15, wherein the high solar absorptance layer includes a polymer upper layer.

17. A method for manufacturing a heat management material, comprising: selecting a base fabric having an outer surface and an inner surface; bonding one or more multi-layer multifunctional heat management elements to the outer surface of the base fabric, wherein each of the one or more multi-layer multifunctional heat management elements includes a low emissivity layer and a high solar absorptance layer, each of the multi-layer multifunctional heat management elements having a diameter of from 0.1 mm to 10.0 mm, and in each of the plurality of multi-layer multifunctional heat management elements, the high solar absorptance layer is disposed outside the low emissivity layer, and the high solar absorptance layer provides a weighted average solar absorptance of at least 0.5 to the multi-layer multifunctional heat management element.

18. The method according to claim 17, wherein the heat management material has a weighted average solar absorptance of at least 0.

5.

19. The method according to claim 17 or 18, wherein the low emissivity layer is a metal foil.

20. The method according to any one of claims 17 to 19, wherein the high solar absorptance layer includes a polymer upper layer.

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