Thermally stable nano-encapsulated phase change material capsule, and preparation method and application thereof

Abstract

The invention relates to a nano-encapsulated phase change material (nano PCM) capsule, and a preparation method and application thereof. The nano-encapsulated phase change material capsule comprises at least one phase change core material; an inner polymeric shell; and an outer inorganic shell. The outer inorganic shell surrounds the inner polymeric shell. As the nanoencapsulated phase change material capsules are small in size and large in surface area, enhanced thermal stability, efficient heat transfer and improved dispersibility in materials such as fabrics and plastics are provided. The nanoencapsulated phase change material capsules buffer temperature fluctuations by storing and releasing energy, thereby providing thermal conditioning for various products such as garments and packaging materials. In addition, the nano-encapsulated phase-change material capsule is superior to a micron-encapsulated phase-change material capsule in the aspects of thermal stability, mechanical property and service life, so that the nano-encapsulated phase-change material capsule becomes an ideal choice suitable for a high-temperature process and multiple thermal cycles.

Description

Cross - Reference to Related Applications

[0001] This application claims priority to U.S. Provisional Patent Application No. 63 / 603,647, filed on November 29, 2023, and U.S. Patent Application No. 18 / 959,698, filed on November 26, 2024, which are hereby incorporated by reference in their entireties. Technical Field

[0002] The present invention generally relates to phase - change materials. Specifically, the present invention relates to a nano - encapsulated phase - change material capsule, a method for preparing the same, and its applications. Background Art

[0003] Phase - change materials (PCMs) can absorb and release heat energy during their melting and freezing processes, respectively. The process of changing physical properties is called the phase - change process, during which the phase - change material absorbs or releases a large amount of latent heat. The PCM phase - change process has isothermality, that is, the temperature remains constant, and this characteristic is beneficial to controlling the temperature change within a small range, thereby achieving precise temperature control. In contrast, traditional solid or liquid sensible - heat storage materials will have their temperatures changed during the process of absorbing / releasing heat, and correspondingly need to operate within a larger working temperature range, which will lead to a lower thermal - conduction efficiency of the system. In recent years, a new type of phase - change material capsule has been developed. It is a polymer composite material composed of a phase - change core material and a micro - or nano - scale shell material. The shell material needs to withstand high and low temperatures and is not affected by temperature - volume changes, and the core material is an organic substance with a phase - change temperature range between - 50°C and 150°C. The phase - change material capsule technology can effectively solve the problems of leakage, phase separation, and corrosion faced by traditional phase - change materials during use.

[0004] Several attempts have been made to micro - encapsulate phase - change materials. For example, the micro - encapsulated phase - change materials disclosed in U.S. Patent No. 10195577 and U.S. Patent Publication No. 20100068525. However, conventional micro - encapsulated phase - change materials still have some disadvantages, such as problems like leakage, poor coating and dispersion ability, and short service life.

[0005] Chinese Patent Application Publication No. 103191670 discloses a method for preparing a low - energy nano - emulsion. However, the final product presents in the form of a liquid emulsion.

[0006] Wu et al. reported a nano - phase - change material capsule. They used ammonium persulfate as an initiator and prepared a paraffin - core, composite PMMA - SiO through the MMA monomer polymerization reaction and the interfacial hydrolysis of tetraethoxysilane (TEOS). 2Nano-capsules with paraffin as the core and PMMA-SiO as the shell were prepared, and the corresponding mechanism was proposed. However, the obtained nano-phase change material capsules are prone to rupture and have a low heat of fusion. In other words, the particles reported by Wu have a low energy storage density. (Wu, Xiao Lin, et al. "One-Pot Synthesis of Nano-Capsules with Paraffin as Core and PMMA-SiO 2 as Shell by Interfacial Hydrolysis and Polymerization." Materials Science Forum. Vol. 722. Trans Tech Publications Ltd, 2012).

[0007] Many conventional encapsulated phase change materials suffer from low thermal stability, resulting in performance degradation under extreme temperature conditions. In addition, the encapsulation methods used often lead to insufficient protection against leakage and phase separation, thus impairing the overall effectiveness of the materials. Moreover, the energy storage density of these materials is often not optimal, further limiting their practical applications, and the preparation process may be too complex, not only increasing the production cost but also hindering the expansion of production. Solving these drawbacks is crucial for the development of next-generation phase change materials that can meet the requirements of modern thermal management applications. Therefore, there is a need in the art for an advanced phase change material that addresses the limitations of current technologies. Summary of the Invention

[0008] To address the above drawbacks, a first aspect of the present invention provides a thermally stable nano-encapsulated phase change material (nano-PCM) capsule, which comprises at least one phase change core material and a double-layer shell. The double-layer shell includes an inner polymer shell containing at least one polymer material and an outer inorganic shell containing an inorganic material. The outer inorganic shell surrounds the inner polymer shell. The formation of the outer inorganic shell enhances the thermal stability of the thermally stable nano-encapsulated phase change material capsule. The nano-encapsulated phase change material capsule maintains thermal stability at temperatures exceeding 200 °C.

[0009] According to one embodiment, the mass ratio between the at least one phase change core material and the shell material is 5-15:10, and the mass ratio between the at least one polymer material and the inorganic material is 5-15:10.

[0010] According to one embodiment, the at least one phase change core material is selected from light paraffinic hydrocarbons, 25# phase change paraffinic hydrocarbons, 30# phase change paraffinic hydrocarbons, 35# paraffinic hydrocarbons, C 12-28 n-alkanes, C 8-18 fatty alcohols, C 8-18Fatty acids and / or their esters or combinations thereof.

[0011] According to one embodiment, the nanoencapsulated phase change material capsules have a particle size in the range of 50 nanometers to 500 nanometers and a heat of fusion of at least 50 J / g.

[0012] According to one embodiment, the internal polymer shell comprises polystyrene, polymethylstyrene, polymethyl methacrylate (PMMA), polybutyl acrylate (PBA), polyvinyltoluene, polymethacrylic acid, and polyacrylic acid or any combination and / or copolymer thereof.

[0013] According to one embodiment, the external inorganic shell comprises silica (SiO 2 ) formed by the hydrolysis reaction of tetraethoxysilane in an aqueous ethanol solution.

[0014] A second aspect of the present invention provides a one-pot synthesis method for preparing thermally stable nanoencapsulated phase change material capsules. The method includes: mixing at least one phase change core material with a plurality of non-phase change materials to form a hydrophobic mixture, the non-phase change materials including at least one monomer, an initiator, a crosslinker, and at least one hydrophobic surfactant; heating the hydrophobic mixture at a temperature higher than the melting point of the hydrophobic mixture; dropping an aqueous mixture containing water and at least one hydrophilic surfactant into the hydrophobic mixture to form a nanoemulsion; heating the nanoemulsion to form a phase change material encapsulated by an internal polymer shell; and adding an external shell precursor material and reacting to form the external inorganic shell on the internal polymer shell, thereby forming nanoencapsulated phase change material capsules with a double-layer shell.

[0015] According to one embodiment, the amount of the at least one phase change core material accounts for 100 - 500 parts by weight of the hydrophobic mixture. After low-energy emulsification and polymerization, the plurality of non-phase change materials include 100 - 500 parts by weight of monomers; 1 - 5 parts by weight of initiators; 10 - 50 parts by weight of crosslinkers; 100 - 500 parts by weight of surfactants; and 1000 - 6000 parts by weight of water.

[0016] According to one embodiment, the external shell precursor material includes: 100 - 1000 parts by weight of TEOS; 100 - 1000 parts by weight of ethanol; and 500 - 6000 parts by weight of water.

[0017] According to one embodiment, the crosslinker is selected from allyl methacrylate (AMA), benzoyl peroxide (BPO), dicumyl peroxide (DCP), di-tert-butyl peroxide (DTBP), or cumene hydroperoxide (DBHP) or combinations thereof.

[0018] According to one embodiment, the at least one monomer includes styrene, α-methylstyrene, methyl methacrylate (MMA), butyl acrylate (BA), vinyl toluene, methyl ester, methacrylic acid, and acrylic acid, or a combination thereof.

[0019] According to one embodiment, the initiator includes ammonium persulfate, potassium persulfate, tert-butyl hydroperoxide, and 2,2'-azobisisobutyronitrile (AIBN), or a combination thereof.

[0020] According to one embodiment, the at least one hydrophobic surfactant includes sorbitan esters, fatty alcohol polyoxyethylene ethers (AEO), alkylphenol polyoxyethylene ethers (APEO), or a combination thereof.

[0021] According to one embodiment, the at least one hydrophilic surfactant includes cetyltrimethylammonium bromide (CTAB), sodium dodecyl sulfate (SDS), polysorbate, sodium dodecylbenzenesulfonate (SDBS), or a combination thereof.

[0022] According to one embodiment, the formation of the internal polymer shell and the external inorganic shell is carried out at a temperature in the range of 60 to 80 °C.

[0023] A third aspect of the present invention provides a thermoregulating filament, which includes a solid polymer matrix material and thermally stable nano-encapsulated phase change material capsules dispersed in the solid polymer matrix material. The tensile strength of the thermoregulating filament is in the range of 100 - 400 MPa and the elongation at break is 40% to 170%.

[0024] According to one embodiment, the solid polymer matrix material is selected from polyethylene terephthalate (PET), polyamide (PA), polyacrylonitrile (PAN), polyvinyl alcohol (PVA), polyethylene (PE), or polyvinyl chloride (PVC), or a combination thereof.

[0025] According to one embodiment, the mass ratio between the thermally stable nano-encapsulated phase change material capsules and the solid polymer matrix material is 1 - 50:100.

[0026] According to one embodiment, the diameter of the thermoregulating filament is in the range of 5 microns to 50 microns and the heat of fusion is at least 10 J / g.

[0027] According to one embodiment, the thermoregulating filament is made by a method including: mixing the nano-encapsulated phase change material capsules with a polymer melt to form a mixture; extruding the mixture through a die with a diameter of 0.1 - 0.5 mm and spinning it into a filament; and winding the extruded filament with a winding unit at a winding speed of 1 - 10 m / min and a winding torque of 10 - 100 Nm to form the thermoregulating filament.

[0028] According to one embodiment, the mass ratio between the nano-encapsulated phase change material capsules and the polymer melt is 1-50:100.

[0029] According to one embodiment, the polymer melt is made by a process comprising: before use, pre-drying one or more polymer pellets at 60-90 °C for at least 10 hours; and adding the one or more polymer pellets to a high-torque twin-screw extruder, wherein the barrel temperature is set above the melting temperature of the polymer and the screw speed is set at 10-100 rpm.

[0030] According to one embodiment, the filaments are drawn at a draw ratio of 1 to 5 times at a drawing temperature of 60-90 °C using a regulating unit, and then the drawn filaments are annealed at 150-250 °C to obtain the thermoregulating filaments.

[0031] The fourth aspect of the present invention provides a composite material comprising a solid material or a liquid material and thermally stable nano-encapsulated phase change material capsules dispersed therein.

[0032] According to one embodiment, the solid material or the liquid material comprises polyurethane (PU), polymethyl methacrylate (PMMA), acrylonitrile-butadiene-styrene copolymer (ABS), polyamide (PA), polycarbonate (PC), polyoxymethylene (POM), polypropylene (PP), polystyrene (PS), polyethylene (PE), and silicone rubber.

[0033] According to one embodiment, the mass ratio between the thermally stable nano-encapsulated phase change material capsules and the solid material or the liquid material is 1-100:100.

[0034] According to one embodiment, the composite material is made by the following steps: mixing the thermally stable nano-encapsulated phase change material capsules and the solid material or the liquid material at a temperature of 10 °C to 300 °C to obtain a mixture; cooling the mixture and granulating it into pellets; and molding or injection molding the pellets to obtain the composite material. The mixing process is carried out in an open mill, an internal mixer, a molding press, or an extruder.

[0035] The present invention provides significant advantages over current micron PCM capsules. As a thermal storage medium, due to the small size and large specific surface area of the nano-encapsulated phase change material capsules, more efficient heat transfer can be achieved between the phase change nanoparticles and the surrounding environment. Even at high temperatures exceeding 200 °C, the double-layer structure of the nano-encapsulated phase change material capsules shows outstanding thermal stability, which enables them to be processed using methods such as melt spinning. The nano-sized distribution and its excellent mechanical properties enable them to be uniformly dispersed in other matrix materials such as fabrics and plastics, especially in slender fibers with a smooth surface.

[0036] In addition, the technology can be reused for heating-cooling cycles and has a significantly longer service life compared to other thermal storage materials. With these advantages and a wider range of available fabric materials, this technology will significantly enhance the thermal and physical comfort of fabric products. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] To clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained without creative efforts based on these drawings. In the drawings:

[0038] Figure 1 A schematic diagram of a thermally stable nano-encapsulated phase change material capsule according to an embodiment of the present invention is shown;

[0039] Figure 2 The particle size distribution of the thermally stable nano-encapsulated phase change material capsule is shown;

[0040] Figure 3 The differential scanning calorimetry (DSC) spectrum of the thermally stable nano-encapsulated phase change material capsule is shown;

[0041] Figure 4A A scanning electron microscope (SEM) image of a thermally stable nano-encapsulated phase change material capsule according to an embodiment of the present invention is shown. Figure 4B A transmission electron microscope (TEM) image of a thermally stable nano-encapsulated phase change material capsule according to an embodiment of the present invention is shown;

[0042] Figure 5 The temperature-weight ratio curve of samples with different shells is shown;

[0043] Figure 6 A nano-encapsulated phase change material capsule nylon filament according to an embodiment of the present invention is shown;

[0044] Figure 7AShows a nano-encapsulated phase change material capsule fabric according to an embodiment of the present invention. Figure 7B Shows a micrograph of a nano-encapsulated phase change material capsule fabric;

[0045] Figure 8 Shows the tensile stress of nano-encapsulated phase change material capsule nylon filaments with different diameters at different nominal strains;

[0046] Figure 9 Shows the DSC spectrum of nano-encapsulated phase change material capsule nylon filaments according to an embodiment of the present invention;

[0047] Figure 10 Shows three nano-encapsulated phase change material capsule silicone composites (right-angled silicone with nano-encapsulated phase change material capsules, flocked silicone, high-elastic silicone) according to an embodiment of the present invention; and

[0048] Figure 11A Shows the density of silicone and nano-encapsulated phase change material capsules with different ratios. Figure 11B Shows the Shore A hardness of right-angled silicone, flocked silicone and high-elastic silicone with nano-encapsulated phase change material capsules. Figure 11C Shows the latent heat of right-angled silicone, flocked silicone and high-elastic silicone with nano-encapsulated phase change material capsules. Detailed Description of the Invention

[0049] The present invention will be described in detail with reference to the following embodiments and the accompanying drawings. It should be understood that the specific embodiments are for illustrative purposes only and should not be construed as limiting the present invention. Those skilled in the art will understand that other changes and modifications can be made to the invention described herein in addition to the specific embodiments.

[0050] The present invention includes all such changes and modifications, and also includes all steps and features separately or jointly mentioned or pointed out in this specification, as well as any and all combinations of any two or more steps or features. Other aspects and advantages of the present invention will become apparent to those skilled in the art by reviewing the subsequent description.

[0051] In a first aspect of the present invention, there is provided a thermally stable nano-encapsulated phase change material capsule, which comprises at least one phase change core material and a double-layer shell (an external inorganic shell and an internal polymer shell), as Figure 1 shown. The internal polymer maintains encapsulation tightness and provides a synthetic template, and the inorganic shell improves mechanical strength and thermal stability. Importantly, when the external inorganic shell is formed, the thermal stability of the nano-encapsulated phase change material capsule is significantly increased. The formation of the external shell on the nano-encapsulated phase change material capsule significantly enhances its thermal stability. The nano-encapsulated phase change material capsule maintains thermal stability at temperatures above 200 °C.

[0052] The phase change core material includes, but is not limited to, light paraffin hydrocarbons, 25# phase change paraffin hydrocarbons, 30# phase change paraffin hydrocarbons, 35# paraffin hydrocarbons, C 12-28 n-alkanes, C 8-18 fatty alcohols, C 8-18 fatty acids and / or their esters or combinations thereof. The term "#" means the melting temperature of the phase change core material. For example, 25# indicates that the melting temperature of the phase change core material is 25 °C.

[0053] The internal polymer shell can include polystyrene, polymethylstyrene, polymethyl methacrylate, polybutyl acrylate, polyvinyltoluene, polymethacrylic acid, and polyacrylic acid or any combination and / or copolymer thereof. The external inorganic shell can include silica (SiO 2 ) generated by the hydrolysis reaction of tetraethoxysilane in an aqueous ethanol solution.

[0054] In one embodiment, the mass ratio between the phase change core material and the non-phase change shell material is 5-15:10. The non-phase change shell material includes at least one polymer material forming the internal polymer shell and an inorganic material forming the external inorganic shell.

[0055] Conventionally, the preparation of phase change nanoemulsions undergoes a high-energy emulsification process that relies on mechanical forces (such as high-pressure homogenizers) to achieve its desired particle size. However, high-energy emulsification usually has a low yield and is only suitable for small-scale production such as in research laboratories.

[0056] The double-layer shell of the present invention is formed by the following steps: low-energy emulsification, followed by polymerization of a mixture of the phase change core material and the non-phase change shell material in water.

[0057] The method described below employs a low-energy emulsification step based on phase inversion driven by chemical forces to prepare a high-concentration nanoemulsion of the phase change core material. The advantage of this method is a high yield. The production scale of the resulting phase change material nanoemulsion can be easily expanded to an industrial scale. In addition, the polymerization and encapsulation processes are carried out by in-situ one-pot polymerization.

[0058] More specifically, the method for batch preparation of thermally stable nano-encapsulated phase change material capsules begins with a pre-mixing step. A phase change core material is mixed with certain non-phase change materials to form a hydrophobic mixture, and the certain non-phase change materials include at least one monomer, an initiator, a cross-linking agent, and at least one hydrophobic surfactant. Next, with continuous stirring at 100 - 500 rpm, the hydrophobic mixture is heated to a temperature above the melting point of the mixture and maintained for a period of time until a transparent and homogeneous hydrophobic mixture is formed. Similarly, a hydrophilic component (such as a hydrophilic surfactant) is added to water to form an aqueous mixture. Then, a low-energy emulsification process is carried out. The aqueous mixture is added to the hydrophobic mixture in a constant droplet stream. Emulsification is carried out at a stirring speed of 100 - 500 rpm at a temperature of 10 - 80 °C for 15 - 30 minutes using a magnetic stirrer (or other suitable low-energy emulsification equipment, such as a low-shear mixer). The ratio of the aqueous phase to the organic phase is maintained at 1 - 3:1 to obtain an optimal droplet size distribution. After that, a nanoemulsion is formed. The low-energy emulsification process provides a template of small and uniform droplet sizes for the subsequent polymerization reaction.

[0059] In the second stage of the preparation method, an internal shell is formed by the polymerization reaction and cross-linking reaction of monomers and encapsulates each nano-droplet. The polymerization reaction is carried out at 60 - 80 °C while continuously stirring for 4 - 6 hours to ensure the formation of a complete shell, thereby obtaining a uniform double-layer encapsulation structure. During this period, continuous stirring is required at 300 - 600 rpm and in an inert gas atmosphere to obtain thermally stable nano-PCM capsule particles with a uniform particle size of about 50 to 500 nanometers. The inert gas can be nitrogen.

[0060] In the third stage, an external inorganic shell is formed from a precursor material through a sol-gel reaction. The precursor material of the external inorganic shell can include tetraethyl orthosilicate (TEOS). TEOS is a compound that is often used as a precursor for preparing silica in the fields of materials science and chemistry. TEOS undergoes hydrolysis and polycondensation reactions to form silica, which can be used to manufacture thin films, coatings, or as a component in various materials, including as the external shell of microcapsules in encapsulation technology.

[0061] The cross-linking agent can be selected from allyl methacrylate (AMA), benzoyl peroxide (BPO), dicumyl peroxide (DCP), di-tert-butyl peroxide (DTBP), or cumene hydroperoxide (DBHP) or a combination thereof. The monomers can include, but are not limited to, styrene, α-methylstyrene, methyl methacrylate (MMA), butyl acrylate (BA), vinyl toluene, methyl ester, methacrylic acid, and acrylic acid or a combination thereof.

[0062] The initiator may include, but is not limited to, ammonium persulfate, potassium persulfate, tert-butyl hydroperoxide, and 2,2'-azobisisobutyronitrile or a combination thereof.

[0063] The surfactant may include, but is not limited to, polysorbate, sorbitan ester, cetyltrimethylammonium bromide, and alkyl polyethoxylate or a combination thereof. The surfactant is temperature-sensitive.

[0064] In one embodiment, the amount of the phase change core material accounts for 100-500 parts by weight of the mixture of the phase change core material and the non-phase change material of the shell. After the low-energy emulsification and polymerization reaction are completed, the non-phase change material may include the following components in the mixture in proportions: 100-500 parts by weight of monomer, 1-5 parts by weight of initiator, 10-50 parts by weight of crosslinking agent, 100-500 parts by weight of surfactant, and 1000-6000 parts by weight of water.

[0065] It should be noted that the thermally stable nano-encapsulated PCM is superior to the micro-PCM product in the following aspects:

[0066] (1) Due to the smaller size (50-500 nanometers) and larger specific surface area of the nano-encapsulated phase change material capsules, compared with the large-size PCM materials, its thermal conductivity is significantly enhanced. Therefore, the nano-encapsulated phase change material capsules can achieve more efficient heat transfer between the PCM nanoparticles and the surrounding environment.

[0067] (2) The double-layer structure of the nano-encapsulated phase change material capsule particles maintains thermal stability at high temperatures above 200 °C, which enables them to be processed by high-temperature processes such as melt spinning.

[0068] (3) The nano-sized distribution enables these materials to be uniformly dispersed in other matrix materials such as fabrics and plastics. Their good mechanical properties (tensile strength of 100-400 MPa and elongation at break of 40-170%) allow these materials to be dispersed in long and thin filaments with a diameter as small as 5-50 microns, resulting in a smooth surface.

[0069] (4) It can be reused for many heating-cooling cycles, usually able to withstand up to 1000 cycles, while maintaining a longer service life compared to other thermal storage materials. After undergoing 1000 cycles, its efficiency only drops by 10%.

[0070] (5)Conventional microencapsulated phase change materials have a high tendency to rupture and phase separate after being in an ultrasonic water bath. The rupture of the conventional microencapsulated phase change material particles is visible to the naked eye. Similarly, the phase separation phenomenon often occurs. In contrast, the thermally stable nanoencapsulated phase change material capsules of the present invention remain stable after the same treatment (ultrasonic water bath for 10 minutes). With these advantages, combined with a wider range of fabric materials, this technology will significantly improve the thermal and physical comfort of fabric products.

[0071] When the thermally stable nanoencapsulated phase change material capsules are used with other materials to manufacture products, the final products exhibit an effective buffering balance of heat against environmental temperature fluctuations. For example, the thermally stable nanoencapsulated phase change material capsules are used with other materials to manufacture fibers, fabrics, etc. For example, the thermal comfort of clothing can be improved while increasing the heat transfer efficiency.

[0072] The present invention also provides a heat-regulating filament, which comprises a solid polymer matrix material and thermally stable nanoencapsulated phase change material capsules dispersed in the solid polymer matrix material. The mass ratio between the thermally stable nanoencapsulated phase change material capsules and the solid polymer matrix material is 1-50:100. The diameter of the prepared heat-regulating filament is in the range of 5 to 50 microns and the heat of fusion is 10 J / g or greater. The tensile strength of the heat-regulating filament is in the range of 100-400 MPa and the elongation at break is 40% to 170%.

[0073] In one embodiment, the solid polymer matrix material may include, but is not limited to, polyethylene terephthalate (PET), polyamide (PA), polyacrylonitrile (PAN), polyvinyl alcohol (PVA), polyethylene (PE), or polyvinyl chloride (PVC), or a combination thereof.

[0074] More specifically, the heat-regulating filament is made by a method comprising: incorporating the nanoencapsulated phase change material capsules into a polymer melt and extruding, followed by spinning. First, before use, the polymer pellets are pre-dried at 60-90 °C for at least 10 hours; and then added to a high-torque twin-screw extruder, where the barrel temperature is higher than the melting temperature of the polymer and the screw speed is set at 10-100 rpm. Next, the nanoencapsulated phase change material capsules are added to the extruder. Then extrusion is carried out to obtain an extruded composite material with a die head diameter of 0.1-0.5 mm, where the mass ratio between the nanoencapsulated phase change material capsules and the pre-dried polymer pellets is 1-50:100.

[0075] In one embodiment, the extruded composite material is wound at a winding speed of 1 - 10 m / min and a winding torque of 10 - 100 Nm using a winding unit to form filaments. The filaments are stretched by an adjusting unit at a stretching ratio of 1 - 5 times and a stretching temperature of 60 - 90 °C, and the stretched filaments are annealed at 150 - 250 °C to obtain thermally conditioned filaments.

[0076] In addition, the present invention also provides a composite material, which comprises a solid material or a liquid material and heat - stable nano - encapsulated phase - change material capsules dispersed therein. The mass ratio between the heat - stable nano - encapsulated phase - change material capsules and the solid material or the liquid material is 1 - 100:100.

[0077] In one embodiment, the solid material or the liquid material may include PU, poly - PMMA, ABS, PA, PC, POM, PP, PS, PE, and silicone rubber.

[0078] The composite material is prepared by the following steps: dispersing the rupture - resistant heat - stable nano - encapsulated phase - change material capsules in a water - based solid material or liquid material. Next, the mixture is cooled and granulated into pellets, and the pellets are molded or injection - molded to obtain the composite material.

[0079] The heat - stable nano - encapsulated phase - change material capsules and the solid material or the liquid material are mixed at a weight ratio of 1 - 100:100.

[0080] In one embodiment, the mixing process is carried out in an open mill, an internal mixer, a molding press, or an extruder.

[0081] The following examples illustrate the present invention without intending to limit it.

[0082] Examples

[0083] Example 1 - Characteristics of Thermally Stable Nanopackaged Phase Change Material Capsules

[0084] Dynamic light scattering (DLS) is a technique used in the fields of physics and chemistry, which analyzes the size and motion of particles in a solution by measuring the fluctuations of light scattering. The particle size distribution diagram shows the volume fraction relative to the particle size (in nanometers). Figure 2 It is shown that after the low - energy emulsification and polymerization process, the average particle size of the heat - stable nano - encapsulated phase - change material capsules is in the range of 300 nanometers to 900 nanometers.

[0085] Preferably, the average particle size of the heat - stable nano - encapsulated phase - change material capsules is in the range of 300 nanometers to 600 nanometers. More preferably, the average particle size of the heat - stable nano - encapsulated phase - change material capsules is 388 nanometers.

[0086] The DSC spectrum of the heat - stable nano - encapsulated phase - change material capsules is as Figure 3As shown. The x-axis indicates temperature in degrees Celsius, and the y-axis indicates heat flow (W / g). The heat fusion indicates the amount of energy required to change the thermally stable nano-encapsulated phase change material capsules from the solid state to the liquid state. The latent heat value of the calculated nano-encapsulated phase change material capsules can be obtained from the results of the DSC spectrum. As Figure 3 shown, the prepared thermally stable nano-encapsulated phase change material capsules have a latent heat of 78.33 J / g at 25 - 30 °C and a supercooling degree of 0.01 °C.

[0087] Figures 4A - 4B SEM and TEM photos of the thermally stable nano-encapsulated phase change material capsules are shown. It can be seen that the nano-encapsulated phase change material capsules have a uniform particle size in the range of 50 nanometers to 500 nanometers. Generally, the particle size of any individual nano-encapsulated phase change material capsule is less than 500 nanometers.

[0088] Example 2 - Composition of Thermally Stable Nanopackaged Phase Change Material Capsules

[0089] Table 1 lists the components of different thermally stable nano-encapsulated phase change material capsules.

[0090] Table 1

[0091] The synthesis process of the thermally stable nano-encapsulated phase change material capsule 1 includes: (1) mixing 100 parts by weight of hexadecane with a variety of non-phase change materials containing 100 parts by weight of styrene, 1 part by weight of AIBN, 10 parts by weight of AMA, and 20 parts by weight of Span 80 to form a hydrophobic mixture; (2) maintaining the hydrophobic mixture at a temperature of 25 °C; (3) dripping an aqueous mixture containing 1000 parts by weight of water and 20 parts by weight of CTAB into the hydrophobic mixture at a constant rate of 5 ml / min and with stirring at 300 rpm to form a nanoemulsion; (4) maintaining the above nanoemulsion at 70 °C in a sealed nitrogen atmosphere for 5 hours to form an internal polymer shell; and (5) adding 100 parts by weight of TEOS / ethanol (1:1) to the above solution and heating at 70 °C for 5 hours to form an external inorganic shell on the internal polymer shell, thereby forming a nano-encapsulated phase change material capsule with a double-layer shell.

[0092] The synthesis process of the thermally stable nano-encapsulated phase change material capsules 2 includes: (1) mixing 100 parts by weight of hexadecane with various non-phase change materials containing 100 parts by weight of styrene / methyl methacrylate (1:1), 1 part by weight of AIBN, 10 parts by weight of AMA, and 20 parts by weight of Span 80 to form a hydrophobic mixture; (2) maintaining the hydrophobic mixture at a temperature of 40 °C; (3) dropping an aqueous mixture containing 1000 parts by weight of water and 25 parts by weight of Tween 80 into the hydrophobic mixture at a constant rate of 5 ml / min and under stirring at 300 rpm to form a nanoemulsion; (4) maintaining the above nanoemulsion at 70 °C in a sealed nitrogen atmosphere for 5 hours to form an internal polymer shell; and (5) adding 200 parts by weight of TEOS / ethanol (1:1) to the above solution and heating at 70 °C for 5 hours to form an external inorganic shell on the internal polymer shell, thereby forming nano-encapsulated phase change material capsules with a double-layer shell.

[0093] Example 4 - Thermal Stability of Nanopackaged Phase Change Material Capsules with Different Shells

[0094] See Figure 5 , three thermally stable nano-encapsulated phase change material capsules were prepared. Compared with the single-layer shell, the thermal stability temperature of the double-layer shell is increased by about 80 degrees.

[0095] Example 5

[0096] Manufacture of Thermoregulatory Filaments

[0097] Refer to Figure 6 and Figures 7A - 7B , nano-encapsulated phase change material capsule nylon filaments are presented, and these filaments can be linearly arranged or arranged in an interwoven manner to form a fabric.

[0098] See Figure 8 , nano-encapsulated phase change material capsule filaments with different diameters in the range of 17 - 26 microns were tested. The results show that the tensile strength of the nano-encapsulated phase change material capsule filaments is in the range of 100 - 400 MPa and the elongation rate is 40% to 170%. The latent heat of the prepared nano-encapsulated phase change material capsule filaments is 16.07 J / g ( Figure 9 ).

[0099] Example 6

[0100] Manufacture of Composite Materials

[0101] A nano-encapsulated phase change composite material can be formed by processing nano-encapsulated phase change material capsules and a polymer matrix. The processing can be blending, extrusion, molding, etc. For example, a nano-encapsulated phase change material silica gel composite material with different silica gels is provided. Figure 10 Three different types of nano-encapsulated phase change material capsule silica gel composite materials are shown, which include right-angled silica gel, flocked silica gel, and highly elastic silica gel, all of which are incorporated with nano-encapsulated phase change material capsules. The right-angled silica gel composite material has a higher latent heat capacity and is an ideal choice for applications that require continuous thermal regulation. Although the flocked silica gel sheet is softer, it can provide moderate heat storage, while the highly elastic silica gel composite material shows a balanced combination of flexibility and thermal stability due to its excellent elasticity. These composite materials demonstrate an application method of nano-encapsulated phase change material capsules and provide a comparison of material properties based on the type of silica gel matrix, including their heat storage and mechanical properties.

[0102] The physical properties (such as density, Shore A hardness, and latent heat) of the nano-encapsulated phase change material silica gel composite materials are also tested, as Figures 11A - 11C shown. Figure 11A The density of silica gel and silica gel-based composite materials with different ratios of nano-PCM capsules is shown. The results show the density of silica gel and silica gel-based composite materials with different ratios of nano-PCM capsules. For example, as the nano-PCM capsule content increases from 10% to 30%, the density also increases. When the nano-PCM capsule content is 10%, the density of the silica gel composite material is approximately 1.1 g / cm 3 , while when the nano-PCM capsule content is 30%, the density increases to approximately 1.25 g / cm 3 . This indicates that a higher nano-PCM capsule content produces a denser composite material, which may affect thermal conductivity and mechanical properties. Figure 11B The Shore A hardness of right-angled silica gel, flocked silica gel, and highly elastic silica gel with nano-PCM capsules is shown. For example, the right-angled silica gel composite material shows a Shore A hardness of 70, while the flocked silica gel composite material exhibits a lower hardness value of approximately 60, indicating that it is softer in texture. In contrast, the highly elastic silica gel with nano-PCM capsules shows a hardness of 65, reflecting the balance between its flexibility and hardness. These variations highlight the influence of nano-PCM capsules on the mechanical properties of different types of silica gel. Figure 11C The latent heat values of right-angled silica gel, flocked silica gel, and highly elastic silica gel composite materials with nano-PCM capsules are shown. The right-angled silica gel exhibits the highest latent heat value of 50 J / g, followed by the highly elastic silica gel with 45 J / g and the flocked silica gel composite material with 40 J / g.

[0103] Those skilled in the art will understand that, given these teachings, alternative embodiments can be implemented without undue experimentation or deviation without departing from the spirit or scope of the present invention. The present invention is limited only by the following claims, which, when considered in conjunction with the above specification and drawings, include all such embodiments and modifications.

[0104] Industrial applicability:

[0105] Nanopackaged phase change material capsule particles can provide effective buffering against environmental temperature fluctuations in a multitude of products such as clothing, bedding, and footwear. For example, the nano-PCM capsules in fabrics continuously interact with the human microclimate, storing and releasing energy to balance body temperature and promote comfort. Additionally, nanopackaged phase change material capsules can be included in packaging materials to maintain the temperature of goods throughout transportation without affecting the amount of available space.

[0106] Definitions

[0107] Throughout this specification, unless the context requires otherwise, the word "comprise" or variations such as "comprises" or "comprising" shall be understood to imply the inclusion of the stated integer or group of integers but not the exclusion of any other integer or group of integers. It should also be noted that in this disclosure and particularly in the claims and / or paragraphs, terms such as "comprises / comprised / comprising" may have the meaning ascribed to them in United States patent law, for example such that it allows elements not expressly recited, but excludes elements found in the prior art or elements affecting the basic or novel characteristics of the invention.

[0108] Furthermore, throughout this specification and the claims, unless the context otherwise requires, the word "include" or variations such as "includes / including" will be understood to imply the inclusion of the stated integer or group of integers but not the exclusion of any other integer or group of integers.

[0109] References in this specification to "one embodiment", "an embodiment", "example embodiment", etc. indicate that the described embodiment may include a particular feature, structure, or characteristic, but not every embodiment necessarily includes the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is considered within the knowledge of those skilled in the art to effect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described.

[0110] As used herein, the terms "approximately," "basically," "substantially," and "about" are used to describe and account for small variations. When used in conjunction with an event or circumstance, the terms can refer to instances where the event or circumstance occurs precisely as well as instances where it occurs nearly. As used herein with respect to a given value or given range, the term "about" generally means within ±10%, ±5%, ±1%, or ±0.5% of the given value or given range. Ranges may be indicated herein as one endpoint to another endpoint or between two endpoints. All ranges disclosed in this disclosure include the endpoints unless otherwise specified. When referring to "substantially" the same value or property, the term may refer to a value within ±10%, ±5%, ±1%, or ±0.5% of the average of the value.

[0111] In the preparation methods described herein, except where a time or order of operations is explicitly recited, steps may be performed in any order without departing from the principles of the invention. A recitation in a claim of performing a first step and then subsequently performing several other steps shall be taken to mean that the first step is performed before any other step, but the other steps may be performed in any suitable order unless an order is further recited in the other steps. For example, a claim element reciting "step A, step B, step C, step D, and step E" shall be interpreted to mean that step A is performed first, step E is performed last, and steps B, C, and D may be performed in any order between step A and step E and the order still falls within the literal scope of the claimed process. A given step or subset of steps may also be repeated. Additionally, unless explicit claim language recites that the specified steps are to be performed separately, the specified steps may be performed simultaneously.

[0112] The term "nanoencapsulated phase change material" as used in the present invention refers to a phase change material having a double-shell structure at the nanoscale. Its core contains a material that can absorb and release heat energy during a phase change, while the double shell provides structural integrity, thermal stability, and enhanced dispersibility in various matrices.

[0113] The term "double shell" as used in the present invention refers to a double encapsulation structure including an inner polymer shell layer and an outer inorganic shell layer. The inner polymer shell layer is a polymer base layer that tightly encapsulates the phase change core material; the outer inorganic shell layer is an inorganic layer formed by hydrolysis and condensation reactions, such as silica, for enhancing mechanical strength and thermal stability.

[0114] The term "low-energy emulsification" used in the present invention refers to an emulsification process that is mainly driven by chemical forces (such as phase inversion) rather than mechanical energy. The mechanical energy required for this method is extremely low, it can be operated at a relatively low temperature (10°C to 80°C), and can produce high-yield and uniform nanoemulsions, which are suitable for industrial-scale production.

[0115] Other definitions of the selected terms used herein may exist in the detailed description of the present invention and apply throughout the text. Unless otherwise defined, all other technical terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention pertains.

Claims

1. A thermally stable nano-encapsulated phase change material capsule, characterized in that: The thermally stable nano-encapsulated phase change material capsules comprise: at least one phase change core material; and A double-layer shell, the double-layer shell comprising: an inner polymeric shell comprising at least one polymeric material; and an outer inorganic shell comprising an inorganic material, wherein the outer inorganic shell surrounds the inner polymer shell, and The formation of the outer inorganic shell enhances the thermal stability of the thermally stable nanoencapsulated phase change material capsules, and the thermally stable nanoencapsulated phase change material capsules maintain thermal stability at a temperature exceeding 200°C.

2. The thermally stable nanoencapsulated phase change material capsule according to claim 1, wherein the mass ratio between the at least one phase change core material and the shell material is 5-15:10, and the mass ratio between the at least one polymer material and the inorganic material is 5-15:

10.

3. The thermally stable nano-encapsulated phase change material capsule according to claim 1, wherein the at least one phase change core material is selected from paraffin, C 12-28 Alkanes, C 8-18 Fatty alcohol, C 8-18 Fatty acids and / or esters thereof or combinations thereof.

4. The thermally stable nanoencapsulated phase change material capsule of claim 1, wherein the particle size of the nanoencapsulated phase change material capsule is in the range of 50 nm to 500 nm and the latent heat of fusion is at least 50 J / g.

5. The thermally stable nanoencapsulated phase change material capsule according to claim 1, wherein the inner polymer shell comprises polystyrene, polymethylstyrene, polymethylmethacrylate (PMMA), polybutylacrylate (PBA), polyvinyltoluene, polymethacrylic acid, polyacrylic acid or any combination and / or copolymer thereof.

6. The thermally stable nanoencapsulated phase change material capsule of claim 1, wherein the outer inorganic shell comprises silica generated by the hydrolysis reaction of tetraethoxysilane (TEOS) in an ethanol aqueous solution.

7. A one-pot synthesis method for preparing the thermally stable nano-encapsulated phase change material capsule according to claim 1, characterized in that: The method comprises: mixing at least one phase change core material with a plurality of non-phase change materials to form a hydrophobic mixture, the plurality of non-phase change materials comprising at least one monomer, an initiator, a crosslinker, and at least one hydrophobic surfactant; heating the hydrophobic mixture at a temperature above the melting point of the hydrophobic mixture; dropping an aqueous mixture comprising water and at least one hydrophilic surfactant into the hydrophobic mixture to form a nanoemulsion; heating the nanoemulsion to form a phase change material encapsulated by an inner polymer shell; as well as An outer shell precursor material is added and reacted to form the outer inorganic shell on top of the inner polymer shell, thereby forming the thermally stable nanoencapsulated phase change material capsule having a double-layer shell.

8. The method of claim 7, wherein the at least one phase change core material is present in an amount of 100-500 parts by weight of the hydrophobic mixture, and the plurality of non-phase change materials comprises: 100-500 parts by weight of monomer; 1-5 parts by weight of an initiator; 10-50 parts by weight of a cross-linking agent; 100-500 parts by weight of a surfactant; and 1000-6000 parts by weight of water.

9. The method of claim 7, wherein the outer shell precursor material comprises: 100-1000 parts by weight of tetraethoxysilane (TEOS); 100-1000 parts by weight of ethanol; and 500-6000 parts by weight of water.

10. The method according to claim 7, wherein the crosslinking agent is selected from allyl methacrylate (AMA), benzoyl peroxide (BPO), dicumyl peroxide (DCP), di-tert-butyl peroxide (DTBP) or dicumyl hydroperoxide (DBHP) or a combination thereof.

11. The method of claim 7, wherein the at least one monomer comprises styrene, alpha-methylstyrene, methyl methacrylate (MMA), butyl acrylate (BA), vinyl toluene, methyl esters, methacrylic acid, and acrylic acid, or combinations thereof.

12. The method of claim 7, wherein the initiator comprises ammonium persulfate, potassium persulfate, tert-butyl hydroperoxide, and 2,2'-azobisisobutyronitrile (AIBN), or a combination thereof.

13. The method of claim 7, wherein the at least one hydrophobic surfactant comprises a sorbitan ester, an alcohol ethoxylate (AEO), an alkylphenol ethoxylate (APEO), or a combination thereof.

14. The method of claim 7, wherein the at least one hydrophilic surfactant comprises cetyltrimethylammonium bromide (CTAB), sodium dodecyl sulfate (SDS), polysorbate, sodium dodecylbenzene sulfonate (SDBS), or a combination thereof.

15. A thermally regulating filament comprising a solid polymer matrix material and the thermally stable nanoencapsulated phase change material capsules according to claim 1 dispersed in the solid polymer matrix material, wherein the thermally regulating filament has a tensile strength in the range of 100-400 MPa and an elongation of 40% to 170%.

16. The heat regulating filament according to claim 15, wherein the solid polymer matrix material is selected from polyethylene terephthalate (PET), polyamide (PA), polyacrylonitrile (PAN), polyvinyl alcohol (PVA), polyethylene (PE) or polyvinyl chloride (PVC) or a combination thereof.

17. The thermal regulating filament of claim 15, wherein the mass ratio between the thermally stable nanoencapsulated phase change material capsules and the solid polymer matrix material is 1-50:

100.

18. The heat regulating filament of claim 15, wherein the heat regulating filament has a diameter in the range of 5 microns to 50 microns and a latent heat of fusion of at least 10 J / g.

19. The heat regulating filament of claim 15, wherein the heat regulating filament is made by a process comprising: mixing the nano-encapsulated phase change material capsules with a polymer melt to form a mixture, wherein the mass ratio between the nano-encapsulated phase change material capsules and the polymer melt is 1-50:100; Extruding the mixture through a die having a diameter of 0.1-0.5 mm and spinning into filaments; and The extruded filaments are wound with a winding unit at a winding speed of 1-10 m / min and a winding torque of 10-100 Nm to form the heat-conditioned filaments.

20. The heat-conditioned filament according to claim 19, wherein the filament is stretched at a stretching temperature of 60-90°C at a stretching ratio of 1 to 5 times using a conditioning unit, and then the stretched filament is annealed at 150-200°C to obtain the heat-conditioned filament.

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