Heat dissipation-heat insulation switching flame-retardant material and manufacturing method therefor

Abstract

The present invention relates to a heat dissipation-heat insulation switching flame-retardant material comprising core particles and a flame-retardant organic layer generating char, and a manufacturing method therefor. The heat dissipation-heat insulation switching flame-retardant material is characterized by having heat dissipation characteristics at low temperatures and heat insulation and flame retardancy characteristics at high temperatures due to nano-char formation.

Description

Heat-insulating switching flame-retardant material and method for manufacturing the same

[0001] The present invention relates to a heat-insulating switching material that changes from heat-radiating properties to insulation or flame-retardant properties depending on temperature, and a technology for manufacturing the same.

[0002] As the development of intelligent and information technologies continues, there is a growing need for enhanced thermal management to improve the performance and lifespan of electronic devices in diverse fields, such as electric vehicles, communications, and high-power supercomputers. Thermal interface materials (TIMs) play a crucial role as critical components that efficiently connect heat sources to heat sinks, enabling heat transfer. In particular, thermal gap fillers play a crucial role in determining TIM properties, such as high thermal conductivity, thermal and mechanical stability, and low interface resistance.

[0003] Fires involving electronic components, particularly batteries, are occurring frequently worldwide. However, existing TIMs primarily function solely to dissipate heat, limiting their ability to prevent or extinguish fires. Several studies have explored thermal gap fillers, such as ceramics (e.g., SiO2, Al2O3), carbon materials (e.g., graphene, carbon nanotubes), and metals (e.g., Cu, Ag). However, these studies primarily focused on enhancing heat dissipation properties, with minimal attention paid to thermal insulation or flame retardancy to prevent or mitigate electrical fires and explosions. To date, no technology or material has been reported that achieves both heat dissipation and insulation properties. Electrical fires generate toxic gases such as carbon monoxide (CO), hydrogen cyanide (HCN), and polycyclic aromatic hydrocarbons (PAHs), highlighting the need for advanced materials that can reduce the emissions of these toxic gases.

[0004] To address these issues, the development of eco-friendly materials with high thermal insulation or flame retardancy is increasingly emphasized. Biomass- or biomolecule-based flame retardants (FRs) are attracting attention due to their advantages, including high insulation, high flame retardancy, and non-toxicity. In particular, all-in-one flame retardants, such as deoxyribonucleic acid (DNA) and adenosine triphosphate (ATP), inherently possess high flame retardancy due to their phosphoric acid group acting as an acid source that promotes the formation of expanding char, nitrogen groups acting as a blowing agent that generates non-flammable gas, and carbon groups acting as a char source. These all-in-one flame retardants are well-known as eco-friendly materials, emit very low levels of toxic gases, and possess excellent thermal insulation and flame retardancy, making them widely used as next-generation heat insulating and flame retardant materials.

[0005] The present invention presents, for the first time, a heat-dissipating and insulating switching material comprising a heat-converting nanofiller synthesized with layer-by-layer coated chitosan (CS) and DNA using a heat-gap filler including magnetic nanoparticles (MNPs). MNPs were selected as a model gap filler that can be easily functionalized with flame retardants and whose magnetic properties can be tuned to control the heat dissipation path. Therefore, the heat-converting nanofiller exhibits high thermal conductivity (0.467 W m) in an epoxy matrix at room temperature. -1 K -1 It acts as a heat release path indicating the temperature range where electrical fire or explosion is possible. However, in the temperature range where electrical fire or explosion is possible, the heat conversion nanofiller is converted into a heat insulating nanofiller due to the formation of nano-chasm by the organic coating layer, and has low thermal conductivity (0.171 W m) at the ignition point of general plastics (over 300 ℃). -1 K -1 The present invention systematically demonstrates that CS and DNA are directly involved in the formation of nano-chambers, and characterizes various properties of this unique material. The material proposed by the present invention presents a new perspective as a next-generation gap filler capable of simultaneously providing heat dissipation and insulation.

[0006] One object of the present invention is to provide a heat-insulating switching flame retardant material having core particles coated with an organic layer and a positively charged polymer layer whose heat-insulating properties are switched depending on temperature.

[0007] Another object of the present invention is to provide a method for manufacturing the heat-insulating switching flame retardant material.

[0008] In one aspect, the present invention provides a heat-insulating switching flame retardant material comprising a core particle and a flame retardant organic layer that generates char.

[0009] In one embodiment, the core particle may further include a positively charged polymer layer, and the flame retardant organic layer and the positively charged polymer layer may be alternately coated on the surface of the core particle.

[0010] In one embodiment, the flame retardant organic layer may contain phosphorus.

[0011] In one embodiment, the flame retardant organic layer may comprise a nucleotide or phytic acid.

[0012] In one embodiment, the nucleotide may comprise a nucleic acid or an NTP.

[0013] In one embodiment, the nucleic acid may comprise DNA or RNA.

[0014] In one embodiment, the NTP may be a substance comprising any one selected from the group consisting of ATP, GTP, CTP, TTP, and UTP, and the dNTP may be a substance comprising any one selected from the group consisting of dATP, dGTP, dCTP, dTTP, and dUTP.

[0015] In one embodiment, the positively charged polymer layer may include an amine group.

[0016] In one embodiment, the polymer containing the amine group may include chitosan, Poly(L-lysine), Poly(ethyleneimine), Poly(β-amino ester), or Poly(amidoamine).

[0017] In one embodiment, the core particles may comprise metal oxide or ceramic particles.

[0018] In one embodiment, the metal oxide or the ceramic particles may be characterized as having magnetism.

[0019] In one embodiment, the metal oxide may include magnetite (Fe3O4), hematite (Fe2O3), or ferrite.

[0020] In one embodiment, the core particle may have a silica (SiO2) coating on its surface to form a core-shell structure.

[0021] In one embodiment, the diameter of the heat-insulating switching flame retardant material may be 300 nm to 400 nm.

[0022] In one embodiment, the nano-char may be formed to have heat dissipation properties at low temperatures and heat insulation and flame retardancy properties at high temperatures.

[0023] In one embodiment, the heat-insulating switching flame retardant material may be characterized by forming the nano-char at a temperature of 300°C or higher.

[0024] In another aspect, the present invention may be a method for manufacturing a heat-insulating switching flame-retardant material, comprising a first step of preparing a core particle, a second step of coating a surface of the core particle with one of a flame-retardant organic material and a positively charged polymer material to form a first layer, and a third step of coating a different material from the first layer among the flame-retardant organic material and the positively charged polymer material on the first layer to form a second layer.

[0025] In one embodiment, the second step and the third step may be repeated two or more times so that the flame retardant organic material and the positively charged polymer material are alternately coated.

[0026] In one embodiment, the flame retardant organic material may contain phosphorus.

[0027] In one embodiment, the flame retardant organic material may comprise a nucleotide or phytic acid.

[0028] In one embodiment, the nucleotide may comprise a nucleic acid, NTP, or dNTP.

[0029] In one embodiment, the nucleic acid may comprise DNA or RNA.

[0030] In one embodiment, the NTP may be a substance comprising any one selected from the group consisting of ATP, GTP, CTP, TTP, and UTP, and the dNTP may be a substance comprising any one selected from the group consisting of dATP, dGTP, dCTP, dTTP, and dUTP.

[0031] In one embodiment, the positively charged polymer material may include an amine group.

[0032] In one embodiment, the polymer containing the amine group may include chitosan, Poly(L-lysine), Poly(ethyleneimine), Poly(β-amino ester), or Poly(amidoamine).

[0033] In one embodiment, the core particles may comprise metal oxide or ceramic particles.

[0034] In one embodiment, the metal oxide or the ceramic particles may be characterized as having magnetism.

[0035] In one embodiment, the metal oxide may include magnetite (Fe3O4), hematite (Fe2O3), or ferrite.

[0036] In one embodiment, the core particle may have a silica (SiO2) coating on its surface to form a core-shell structure.

[0037] In one embodiment, the first step may be prepared by solvothermal treatment of a mixture comprising a precursor of the core particle followed by cooling.

[0038] In one embodiment, a fourth step of dispersing the coated core particles into a matrix resin and curing the same may be additionally included.

[0039] In one embodiment, the matrix resin may include an epoxy matrix, a silicone matrix, a urethane matrix, or an acrylic matrix resin.

[0040] In another aspect, the present invention may be a heat-insulating switching flame-retardant material manufactured according to the method for manufacturing the heat-insulating switching flame-retardant material.

[0041] A heat-insulating switching flame-retardant material according to an embodiment of the present invention can have heat dissipation properties at low temperatures and insulation and flame-retardant properties at high temperatures by forming nano-char.

[0042] A method for manufacturing a heat-insulating switching flame retardant material according to an embodiment of the present invention can provide a method for manufacturing a heat-insulating switching flame retardant material as described above.

[0043] FIG. 1a is a drawing visually summarizing the basic concept and function of a heat-insulating switching flame retardant material according to one embodiment of the present invention.

[0044] Figure 1b is a schematic diagram showing a step-by-step synthesis process of a heat-insulating switching flame retardant material according to one embodiment of the present invention.

[0045] FIG. 2a shows a scanning electron microscope (SEM) image showing the surface morphology and size of a heat-insulating switching flame retardant material according to one embodiment of the present invention.

[0046] FIG. 2b shows a transmission electron microscope (TEM) image showing the internal structure and detailed morphology of a heat-insulating switching flame retardant material according to one embodiment of the present invention.

[0047] FIG. 2c shows an elemental mapping image visualizing the elemental distribution of a heat-insulating switching flame retardant material according to one embodiment of the present invention.

[0048] FIG. 2d shows a Fourier transform infrared spectroscopy (FT-IR) spectrum that can confirm the functional group of a heat-insulating switching flame retardant material according to one embodiment of the present invention.

[0049] Figure 2e shows the results of a DPPH antioxidant capacity test to confirm the antioxidant properties of a heat-insulating switching flame retardant material according to one embodiment of the present invention.

[0050] Figure 2f shows the results of comparing the biocompatibility of a heat-insulating switching flame-retardant material according to one embodiment of the present invention according to the presence or absence of a magnetic nanoparticle coating and its type.

[0051] FIG. 3a shows a thermogravimetric analysis (TGA) curve for confirming the thermal stability of a heat-insulating switching flame retardant material according to one embodiment of the present invention.

[0052] FIG. 3b shows a differential thermogravimetric analysis (DTG) curve showing the thermal decomposition characteristics of a heat-insulating switching flame retardant material according to one embodiment of the present invention.

[0053] FIG. 3c shows a differential thermal analysis (DTA) curve representing the thermal decomposition reaction of a heat-insulating switching flame retardant material according to one embodiment of the present invention.

[0054] FIG. 3d shows a differential scanning calorimetry (DSC) curve for confirming the thermal characteristics of a heat-insulating switching flame retardant material according to one embodiment of the present invention.

[0055] FIG. 3e shows scanning electron microscope (SEM) and transmission electron microscope (TEM) images at high temperatures to confirm nano-phase formation of a heat-insulating switching flame retardant material according to one embodiment of the present invention.

[0056] FIG. 3f shows the results of X-ray photoelectron spectroscopy (XPS) analysis to confirm the chemical composition change of the heat-insulating switching flame retardant material according to one embodiment of the present invention.

[0057] FIG. 3g shows an XPS high-resolution carbon (C1s) spectrum for confirming the change in carbon bonding state of a heat-insulating switching flame retardant material according to one embodiment of the present invention.

[0058] FIG. 4a is a schematic diagram showing a step of dispersing and curing magnetic particles manufactured according to one embodiment of the present invention into a matrix resin.

[0059] FIG. 4b is a graph showing the change in thermal conductivity of an epoxy matrix according to the concentration of a heat-insulating switching flame retardant material according to one embodiment of the present invention.

[0060] Figure 4c is a graph showing the change in thermal conductivity according to temperature of a heat-insulating switching flame retardant material according to one embodiment of the present invention.

[0061] FIG. 4d is a graph comparing the thermal conductivity of an epoxy matrix containing a heat-insulating switching flame retardant material according to one embodiment of the present invention with that of other epoxy fillers.

[0062] FIG. 4e is a schematic diagram showing a heat dissipation mechanism of a heat-insulating switching flame retardant material according to one embodiment of the present invention.

[0063] FIG. 4f is an image showing the results of a UL 94 vertical burn test of an epoxy matrix containing a heat-insulating switching flame retardant material according to one embodiment of the present invention.

[0064] FIG. 4g is a graph showing the results of a limiting oxygen index (LOI) test of an epoxy matrix containing a heat-insulating switching flame retardant material according to one embodiment of the present invention.

[0065] FIG. 4h is a schematic diagram showing the thermal insulation and flame retardancy mechanism of a heat-insulating switching flame retardant material according to one embodiment of the present invention.

[0066] FIG. 5a is an image showing gas evolution during combustion of an epoxy matrix containing a heat-insulating switching flame retardant material according to one embodiment of the present invention.

[0067] FIG. 5b is a graph showing the concentration of gas emissions during combustion of an epoxy matrix containing a heat-insulating switching flame retardant material according to one embodiment of the present invention.

[0068] FIG. 6 shows the change in color of filler samples according to weight ratio and the strain-stress curve for each sample to determine the mechanical properties of magnetic particles manufactured according to one embodiment of the present invention.

[0069] Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings. The present invention is susceptible to various modifications and variations, and thus specific embodiments are illustrated in the drawings and described in detail in the text. However, this is not intended to limit the present invention to a specific disclosed form, but rather to encompass all modifications, equivalents, and alternatives falling within the spirit and technical scope of the present invention.

[0070] The terminology used in this application is only used to describe specific embodiments and is not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly indicates otherwise. In this application, the terms "comprise" or "have" should be understood to indicate the presence of a feature, number, step, operation, component, or combination thereof described in the specification, but do not preclude the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, or combinations thereof.

[0071] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Terms defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and shall not be interpreted in an idealized or overly formal sense unless explicitly defined herein.

[0072]

[0073] Conventional heat-dissipating materials have excellent thermal conductivity and have been applied in various industrial fields. However, they only function to dissipate heat and do not provide insulation or flame retardancy in the temperature range where dangerous accidents such as fire and explosion can occur. To solve this problem, there have been attempts to produce separate heat-dissipating materials and insulating or flame retardant materials and simply combine the two materials. However, there has been no report of a single material simultaneously implementing these heat-dissipating, insulating, and flame retardant functions. Therefore, the purpose of the present invention is to provide a heat-insulating switchable material that has the characteristics of heat-dissipating and insulating each other and furthermore, it has flame retardant properties. This is the world's first technology that simultaneously implements the characteristics of conventional heat-dissipating materials and insulating (flame retardant) materials, and is expected to have a very wide range of applications in the environmental, electronics, bio, aerospace, and energy fields.

[0074] A heat-insulating switching flame-retardant material according to the present invention comprises a core particle, a flame-retardant organic layer forming a char, and a positively charged polymer layer, and the flame-retardant organic layer and the positively charged polymer layer may be alternately coated one or more times on the surface of the core particle.

[0075] The above flame-retardant organic layer is a layer composed of an organic material containing phosphorus, carbon, and nitrogen atoms, and may be, for example, a nucleotide or phytic acid containing phosphorus. More specifically, it may include a nucleic acid such as DNA or RNA, or a substance such as NTP or dNTP. Here, NTP may be any one of substances such as ATP, GTP, CTP, TTP, and UTP, and dNTP may be any one of substances such as dATP, dGTP, dCTP, dTTP, and dUTP.

[0076] The above flame retardant organic layer contains phosphorus (P), which serves as an acid source, which is an essential element for high flame retardancy properties, carbon (C), which serves as a char source, and nitrogen (N), which serves as a blowing agent, which is essential for forming insulating properties. Nucleotides are double helix structures composed of a phosphate-sugar backbone and base pairs, and phosphorus (P) in phosphoric acid is a phosphate group (PO4 3- ) exists in the form of a nucleotide, carbon (C) is included as an essential component of sugars and bases, and nitrogen (N) is included as an essential component of bases such as adenine, guanine, cytosine, thymine, or uracil. DNA, a representative material of nucleotides, was selected as a flame-retardant organic layer material according to one embodiment of the present invention because it is a material with such structural characteristics, high thermal stability, and biocompatibility. However, the present invention is not limited to this specific configuration, and any layer containing other flame-retardant organic materials containing phosphoric acid, carbon, and nitrogen atoms may be included in the scope of the present invention.

[0077] The above-mentioned positively charged polymer layer may be composed of a material that has a positive charge in an aqueous solution. A polymer containing an amine group becomes a positively charged material because the amine group acts as a Lewis base in an aqueous solution and is protonated to become an ammonium ion. For example, it may include a polysaccharide such as chitosan, Poly(L-lysine), Poly(ethyleneimine), Poly(βester), or Poly(amidoamine). Chitosan was selected as a material for the positively charged polymer layer according to one embodiment of the present invention because it is a material that can maximize flame retardant properties along with excellent biocompatibility. Such a positively charged polymer material can easily combine with a flame retardant organic layer such as DNA, thereby improving the stability and functionality of the composite material. However, the present invention is not limited to such a specific configuration, and any layer containing a positively charged polymer material that has high biocompatibility and can further maximize flame retardant properties may be included in the scope of the present invention.

[0078] Repeated coatings of the above flame-retardant organic layer and the positively charged polymer layer evenly distribute each material, maximizing the performance of the overall material. The number of repeated coatings can be flexibly adjusted according to the needs of specific functions.

[0079] The core particles may be magnetic particles composed of a magnetic material including metal oxide or ceramic particles, and for example, may include magnetic nanoparticles such as magnetite (Fe3O4), hematite (Fe2O3), or ferrite. In particular, iron oxide magnetic particles have excellent magnetic properties and chemical stability, and thus were selected as the core material for surface functionalization according to one embodiment of the present invention. However, the present invention is not limited to this specific configuration, and other materials having magnetism may also be included within the scope of the present invention.

[0080] The core particles may be coated with silica (SiO2) on their surfaces to form a core-shell structure. By coating the surface of the core particles with silica, oxidation of the core particles can be prevented, and agglomeration of the core particles can be prevented, thereby increasing the stability of the heat-insulating switching flame-retardant material of the present invention.

[0081] The diameter of the material according to the present invention may be about 300 nm to 400 nm, and preferably about 350 nm. The diameter of about 350 nm is the diameter of the heat-insulating switching flame-retardant material when the flame-retardant organic layer and the positively charged polymer layer are repeatedly coated 10 times. The stability of the coating layer can be maximized by the thickness, thereby optimizing the performance of the heat-insulating switching flame-retardant material.

[0082] Figure 1a is a drawing that visually summarizes the basic concept and function of such a heat-insulating switching flame retardant material. The heat-insulating switching flame retardant material according to the present invention switches its heat-radiating and heat-insulating properties depending on the temperature. At room temperature or low temperatures, it exhibits high thermal conductivity, so that it can effectively dissipate internal heat. However, at high temperatures around 300°C, the formation of nano-char in the flame retardant organic layer lowers the thermal conductivity, resulting in heat-insulating properties. In other words, the heat-insulating switching flame retardant material of the present invention switches its heat-radiating and heat-insulating properties depending on the temperature, thereby preventing fires, explosions, etc. in a temperature range where dangerous accidents occur.

[0083] FIG. 1B is a schematic diagram showing a step-by-step synthesis process of a heat-insulating switching flame retardant material according to an embodiment of the present invention. Referring to FIG. 1B, a method for manufacturing a heat-insulating switching flame retardant material may include a first step of preparing core particles, a second step of coating a surface of the core particles with either a flame retardant organic material or a positively charged polymer material to form a first layer, and a third step of coating a different material from the first layer among the flame retardant organic material and the positively charged polymer material on the first layer to form a second layer.

[0084] The first step can be prepared by solvothermal treatment of a mixture containing the precursor of the core particle, followed by cooling. This process plays a crucial role in optimizing the properties of the core particle by precisely controlling its size and shape, and the post-solvothermal cooling process serves to stabilize the core particle crystal.

[0085] The second step is to form a first layer by coating either a flame-retardant organic material or a positively charged polymer material. The present invention does not limit the type of first layer to be coated, and those skilled in the art can appropriately select one based on the manufacturing conditions and purpose.

[0086] The third step involves forming the second layer using a layer-by-layer (LbL) method. For example, if the first layer is a flame-retardant organic material, the second layer is coated with a positively charged polymer. Conversely, if the first layer is a positively charged polymer, the second layer is coated with a flame-retardant organic material. This repeated coating process maximizes the material's versatility.

[0087] By repeating the second and third steps at least twice and alternately coating the flame-retardant organic material and the positively charged polymer material, a heat-insulating switching flame-retardant material having a diameter suitable for forming nano-char can be manufactured.

[0088] A fourth step of dispersing the coated core particles into a matrix resin and curing the dispersed core particles may be additionally included. In one embodiment of the present invention, the matrix resin may be an epoxy matrix resin. The epoxy matrix resin was selected due to its excellent mechanical strength and thermal stability. The epoxy resin can combine with the core particles to increase the structural stability of the entire material and maintain performance even in high-temperature environments. However, the present invention is not limited to this specific configuration, and any resin widely used in thermal interface materials (TIM) and heat-dissipating materials, such as silicone matrix, urethane matrix, or acrylic matrix resin, may be included in the scope of the present invention.

[0089] Below, Experimental Example 1 showing the synthesis process of the heat-insulating switching flame-retardant material of the present invention is introduced.

[0090] (Experimental Example 1)

[0091] [Synthetic material]

[0092] The following chemicals were used in the experiments: Iron(III) chloride hexahydrate (FeCl3·6H2O), sodium acetate (NaAc), trisodium citrate, and ethylene glycol (99.5%, 500 mL) were purchased from Samchun Chemical Co., Ltd., Seoul, Korea. Deoxyribonucleic acid sodium salt extracted from salmon testis (fish sperm DNA, 10 g), low-molecular-weight chitosan (50 g), and sodium dodecyl sulfate (SDS) were purchased from Sigma-Aldrich, St. Louis, MO, USA. DNA was stored at 4°C until use. For the preparation of the epoxy matrix, resorcinol diglycidyl ether (RDGE) was purchased from Toronto Research Chemicals, Toronto, Canada. Additionally, N,N-dimethylbenzylamine (BDMA) and 2,4,6-tris(dimethylaminomethyl)phenol (DMP-30) were purchased from Sigma-Aldrich, St. Louis, MO, USA.

[0093] Synthesis of Iron Oxide Magnetic Nanoparticles

[0094] Hereinafter, for convenience of expression, MNPs will be used as an abbreviation for magnetic nanoparticle.

[0095] Fe3O4MNPs were synthesized using a solvothermal method. A mixture of FeCl3·6H2O (1.3 g), sodium acetate (NaAc, 2 g), trisodium citrate (0.5 g), and ethylene glycol (40 mL) was stirred vigorously to form a yellow-green suspension. 100 mL of this suspension was transferred to a stainless steel autoclave with a Teflon liner, sealed, and solvothermally treated in a vacuum oven at 200 °C for 14 h. The autoclave was then cooled naturally to room temperature. The resulting black powder was thoroughly washed with deionized water and ethanol via magnetic separation, and then vacuum-dried at 50 °C for 24 h.

[0096] [Silica capping on iron oxide magnetic nanoparticles]

[0097] Next, the synthesized MNP (140 mg) was diluted with a mixture of ethanol (28 mL) and water (7 mL) using the Stober method. After adding ammonia solution (1 mL, 28 wt%), tetraethyl orthosilicate (TEOS) (400 μL) was introduced into the reaction mixture, which was mechanically stirred at 25°C for 8 h. During this period, silica was formed on the surface of the magnetite nanoparticles through hydrolysis and subsequent condensation of TEOS.

[0098] [Magnetic Nanoparticle Phase LbL Method]

[0099] Before use, DNA extracted from fish sperm was briefly filtered through a syringe filter (pore size: 450 nm). DNA solutions were prepared by slowly dissolving DNA powder in an aqueous solution containing 1 vol% acetic acid (Sigma-Aldrich Srl, Milan, Italy) and stirring at 300 rpm for 2 h at room temperature using a magnetic stirrer. The pH of these solutions was adjusted to 4 at 2.5 wt% and 8 wt%, respectively. Finally, the pH of the 0.5 wt% DNA solution was adjusted to 7 only for the layer-by-layer (LbL) treatment. NaOH was used in all cases. Chitosan (CS) was prepared by dissolving it in an aqueous solution containing 1 vol% acetic acid (Sigma-Aldrich Srl, Milan, Italy) and stirring at pH 4 for 24 h at room temperature using a magnetic stirrer. A CS solution of 0.5 wt%, pH 3.5 was prepared and used in the LbL method.

[0100] Before the LbL process, SDS was used as a protective agent to prevent aggregation of Fe3O4MNPs. SDS is an anionic surfactant, sodium dodecyl sulfate. Fe3O4 / SiO₂ nanoparticles (1%, w / w suspension) were adsorbed with SDS (0.025 M) in a 0.5 M NaCl solution for 4 h, and then washed three times with water. The presence of salt ions changes the structure of the adsorbed polyelectrolyte, affects the Debye length of the electrical interaction, and shields the charge of the polyion repeating segment. Afterwards, excess SDS was removed from the supernatant by centrifugation.

[0101] A certain amount of the prepared chitosan powder was added to a vessel containing purified silica-coated Fe3O4 nanoparticles in a 0.5 M NaCl solution with 1% acetic acid. The mixture was placed in a shaking incubator for 4 hours to ensure that the chitosan layer was effectively deposited and evenly distributed on the nanoparticle surface. After this incubation period, the vessel was removed from the shaking incubator, and the nanoparticles were separated from the solution using a magnetic separator. The nanoparticles were then washed with deionized water to remove any residual chitosan that was not firmly bound to the nanoparticle surface. The chitosan-coated nanoparticles were resuspended in a 0.5 M NaCl solution with 1% acetic acid, and a certain amount of the prepared DNA powder was added to the vessel. The vessel was placed in a shaking incubator again for 4 hours under the same conditions. The shaking incubator promoted the efficient adsorption of DNA molecules onto the CS-coated nanoparticle surface. After incubation, the vessel was removed from the shaking incubator, and the nanoparticles were separated from the solution using a magnetic separator. The nanoparticles were then washed with deionized water to remove unbound DNA. This LbL process was repeated a total of 10 times (10 BL) to obtain the desired multilayer coating on the nanoparticles. After each cycle, the nanoparticles were washed with deionized water and resuspended in 0.5 M NaCl solution with 1% acetic acid before proceeding to the next coating step.

[0102] The above LbL method process is merely an example, and chitosan does not necessarily need to be coated first. DNA can be coated first, and then chitosan can be coated using the LbL method. This can be selected depending on the experimental conditions and purpose.

[0103] [Characterization of MNP@CS / DNA Thermally Switchable Nanofillers]

[0104] For convenience of expression below, MNP@CS / DNA is defined and used as a composite nanoparticle in which chitosan (CS) and deoxyribohexane (DNA) are coated on the surface of MNP using a layer-by-layer (LbL) method.

[0105] Referring to the upper left of Fig. 1b, tetraethyl orthosilicate (TEOS) is added to the iron oxide magnetic nanoparticles to form a silica (SiO2) coating on the MNP surface, forming a core-shell structure. Next, sodium dodecyl sulfate (SDS) functionalization is performed to impart a strong and stable negative charge to the particle surface for smooth coating of chitosan. If DNA is coated first, SDS functionalization is not desirable, and other surfactants can be used to impart a strong and stable positive charge to the particle surface. Subsequently, as shown in the upper right of Fig. 1, positively charged CS and negatively charged DNA are alternately and repeatedly coated. As a result, flame-retardant organic coating layers composed of CS and DNA can be accumulated on the MNP surface through electrostatic interaction. The presence of each flame-retardant organic layer is confirmed through zeta potential analysis when CS and DNA are repeatedly coated. This coating process is repeated until 20 flame-retardant organic layers (10 alternating coatings of CS and DNA) are accumulated on the MNP surface. The number of alternating coatings was selected as 10 times (10BL) because the total thickness of the flame-retardant organic layers is preferably greater than approximately 53 nm to form nanochar at the nanoscale.

[0106] The shape and size of the resulting MNP@CS / DNA are presented in Fig. 2(a), (b) and Table 1 below.

[0107] Particle Type MNP@SiO2 MNP@CS / DNA(1BL) MNP@CS / DNA(3BL) MNP@CS / DNA(5BL) MNP@CS / DNA(7BL) MNP@CS / DNA(10BL) Shell Thickness (nm) 18.91±0.92 24.23±1.06 31.25±2.13 46.54±3.0 25 5.12±4.0 26 1.62±2.11

[0108] The final diameter of MNP@CS / DNA is about 300 nm to about 400 nm, preferably about 350 nm, indicating that the shape and size distribution of the nanofiller are well defined. However, it is difficult to visually confirm the presence of CS and DNA layers on the MNP surface. Therefore, the elemental mapping results of MNP@CS / DNA were obtained through high-angle reducing dark-field (HAADF) imaging as shown in Fig. 2(c). Each element appears as a small dot with a size proportional to its atomic ratio. The weight and atomic ratio of each element present in MNP@CS / DNA were characterized as shown in Table 2 below.

[0109] Chemical Element Weight Ratio (%) Atomic Ratio (%) Fe38.817.52N0.510.81O40.2363.4P1.241.01Si19.2217.26

[0110] Iron (Fe) is the major component, accounting for approximately 38.8 wt% and 17.52 at% of the MNP@CS / DNA composition. The high iron content is attributed to the magnetic core of MNP@CS / DNA. Nitrogen (N) is also observed at approximately 0.51 wt% and 0.81 at%. This nitrogen content likely originates from the flame-retardant organic layer composed of CS and DNA. Oxygen (O) is the most abundant element, accounting for approximately 40.23 wt% and 63.4 at% of the MNP@CS / DNA composition. The significant oxygen content mainly comes from the silica coating encapsulating the MNP core, which prevents aggregation and provides stability to MNP@CS / DNA. In addition, phosphorus (P) was detected at approximately 1.24 wt% and 1.01 at%. This phosphorus content may originate from the extraction and purification process of DNA, which incorporates phosphate into its backbone structure. Silicon (Si) peaks were also identified at approximately 19.22 wt% and 17.26 at%. The silicon content further confirms that a silica coating was successfully formed on the MNP surface. These results suggest that all reagents such as CS and DNA were effectively combined during the LBL coating process, resulting in the formation of a thick flame-retardant organic layer composed of CS and DNA on the MNP surface. As shown in Fig. 2d, the presence of the flame-retardant organic layer composed of CS and DNA on the MNP@CS / DNA surface was confirmed using Fourier transform infrared spectroscopy (FT-IR). MNP@CS / DNA exhibited similar peaks to MNP and silica-coated MNP (MNP@SiO2). The MNP spectrum showed peaks at approximately 580 and 3435 cm -1 The absorption peak corresponding to iron oxide was observed in the MNP@SiO2 spectrum at approximately 802 cm -1 In the case of MNP@CS / DNA, a peak corresponding to the stretching vibration of Si-O-Si derived from silica was observed. However, MNP@CS / DNA showed a peak at approximately 896 cm -1 and 3364 cm -1In each case, additional peaks corresponding to amine (NH) and amide (C=O) groups derived from CS were observed. In addition, at approximately 552-622 cm -1 and 1068 cm -1 In the phosphate group (PO2) - ) and two peaks corresponding to about 1500-1750 cm -1 Peaks corresponding to nucleobase vibrations of DNA were identified. These results provide important evidence confirming the presence of a flame-retardant organic layer composed of CS and DNA on the surface of MNP@CS / DNA.

[0111] Figure 2e shows the results of further investigation of the antioxidant capacity of MNP@CS / DNA using 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay. Upon addition of MNP@CS / DNA, the color of the DPPH solution rapidly changed from purple to yellow. This color change was monitored using UV-Vis spectroscopy, and a rapid decrease in the intensity of the absorbance peak at 516 nm was observed after the addition of MNP@CS / DNA. However, this change was not observed for MNP. This indicates that the MNP@CS / DNA nanofiller has a significant antioxidant capacity compared to MNP, which is attributed to the effect of the flame-retardant organic layer composed of CS and DNA present on the MNP surface.

[0112] Furthermore, Figure 2f demonstrates that this flame-retardant organic layer enhances the biocompatibility of MNPs in various cell lines. While MNPs are widely used as imaging agents, their toxicity often limits their biological applications. Cell viability results for 72 h showed that MNP@CS / DNA exhibited significantly higher viability than MNP@SiO2. This suggests that the flame-retardant organic layers of CS and DNA are significantly more biocompatible than the silica coating, which is a common strategy for addressing the toxicity issue of MNPs.

[0113] Figure 3a shows the results of thermogravimetric analysis (TGA) to verify the thermal stability of MNP@CS / DNA. The analysis included uncoated MNP, MNP@SiO2, and bilayer-coated MNP@CS / DNA (1, 3, 5, 7, and 10 BL) samples. The TGA graph shows a clear weight loss profile with increasing temperature. MNP exhibited minimal weight loss, indicating the absence of a flame-retardant organic layer, while MNP@SiO2 exhibited higher weight loss due to the thermal decomposition of the silica coating. In particular, for MNP@CS / DNA, the weight loss gradually increased with increasing layer number, indicating the cumulative effect of the thermal decomposition of the CS and DNA layers. In addition, the thermal stability of the organic coating composed of CS and DNA decreased with increasing temperature, resulting in a greater weight loss at higher temperatures. The first weight loss (15%) up to 200°C is due to evaporation of physically adsorbed water or solvent, and the second major weight loss (62%) from 200°C to 800°C is due to decomposition of CS and DNA layers.

[0114] As shown in Fig. 3(b), the differential thermogravimetric analysis (DTG) graph shows that MNP and MNP@SiO2 are slightly decomposed only at about 200°C. However, MNP@CS / DNA exhibits three large peaks in the temperature range from 280°C to 550°C, which are due to the chemical reaction between the flame-retardant organic layer composed of CS and DNA.

[0115] Differential thermal analysis (DTA) provides valuable information about the temperature-dependent degradation of a material by showing how the rate of weight change of a material changes at a given temperature. The resulting DTA curve for MNP@CS / DNA, shown in Figure 3c, shows that the primary decomposition occurs around 200°C, with secondary decomposition occurring up to 500°C. This distinguishes the temperatures at which a char network, which facilitates heat transfer, is formed from the temperatures at which char, which facilitates heat rejection, is formed. Furthermore, DTA curves provide insight into the temperature-dependent phase transitions or reactions of a material. The peaks in the DTA curves indicate the temperatures at which specific phase transitions or reactions occur. In particular, the peaks above 300°C indicate char formation in the flame-retardant organic layer composed of CS and DNA. Ultimately, all elements except iron (Fe), the main element of MNP, are combusted at approximately 500°C.

[0116] The differential scanning calorimetry (DSC) curve of MNP@CS / DNA, presented in Fig. 3d, exhibits an overall exothermic trend due to char formation in the flame-retardant organic layer composed of CS and DNA. The exothermic peak around 300°C of MNP@CS / DNA is due to char formation in the flame-retardant organic layer, indicating the decomposition of the organic material. These comprehensive results explain the important thermal properties and unique behaviors of MNP@CS / DNA with an organic layer composed of CS and DNA.

[0117] Furthermore, we speculated that the flame-retardant organic layer composed of CS and DNA exhibited excellent thermal properties of MNP@CS / DNA through unique changes at the nanoscale interface. To confirm this, nano-char, a nano-sized bridge structure, was directly observed in MNP@CS / DNA as the temperature increased using an electron microscope, as shown in Fig. 3e. This phenomenon was mainly attributed to the presence of the flame-retardant organic layer composed of CS and DNA. Importantly, char formation plays a crucial role in heat blocking and fire spread delay. Therefore, these results suggest that MNP@CS / DNA has the potential to simultaneously provide heat blocking and fire prevention as an advanced nanofiller material.

[0118] The chemical composition changes of MNP@CS / DNA with temperature were investigated using X-ray photoelectron spectroscopy (XPS). The results presented in Fig. 3f show that MNP@CS / DNA contains six elements: Fe2p, N1s, O1s, C1s, P2p, and Si2p. In particular, the nitrogen (N) and phosphorus (P) peaks are attributed to the flame-retardant organic layer composed of CS and DNA on the MNP surface. A significant change in the atomic percentage (at%) of MNP@CS / DNA was observed at approximately 300°C, in which the element concentration of C1s increased by 38.90%, whereas the concentrations of Si2p, P2p, N1s, O1s, and Fe2p decreased by 12.56%, 0.48%, 2.21%, 22.69%, and 0.96%, respectively. These changes were due to the gasification of nitrogen and phosphorus in the flame-retardant organic layer composed of CS and DNA, resulting in the formation of nanochars around 300°C.

[0119] A closer look at Fig. 3g reveals that the C1 spectrum of MNP@CS / DNA is divided into peaks with binding energies of 287.5, 286.0, 284.9, 283.6, and 283.0 eV, which correspond to NC=O, C-O-C (or C-OH), C-N, C-O, and C=C (or C-C) bonds, respectively. Among these, the NC=O, C-N, and C-O bonds decreased by 3.28%, 10.40%, and 4.28%, respectively, which is a result of the chemical interaction of the C-N and C-N bonds derived from the nucleobases of DNA and the amines of CS with the C-O bond derived from the ribose sugars of DNA and the carbons of CS.

[0120] In contrast, the C=C (or CC) bond increased by 34.83%, indicating the formation of nanochar. In addition, for the flame-retardant organic layer composed of CS and DNA, four peaks at 533.9, 533.1, 532, and 530.9 eV were observed in the O1s spectrum, which correspond to C-O-C / OH, C-O-C, P-O, and Si-O-C bonds, respectively.

[0121] Referring to Figure 3h, the nitrogen and phosphoric acid groups of CS and DNA were measured as CNC and NH bonds at 401 eV and 400 eV, respectively, in the N1s spectrum, and as PO2- bonds at 133.2 eV in the P2p spectrum. However, the areas of these peaks decreased at approximately 300°C. These results suggest that the flame-retardant organic layer composed of CS and DNA can participate in nanochar formation, providing thermal insulation and fire prevention.

[0122] Afterwards, MNP@CS / DNA was incorporated as a filler in the epoxy resin and its heat dissipation properties within the epoxy matrix were investigated.

[0123] [Step of dispersing magnetic particles in matrix resin and curing them]

[0124] Samples were fabricated in a dumbbell shape using a Teflon mold according to the ASTM D638 Type I standard. The fabrication process of the specimens according to the ASTM D638 standard was as follows. Resorcinol diglycidyl ether (RDGE) was used as an epoxy matrix resin, N,N-dimethylbenzylamine (BDMA) was used as a curing agent, and 2,4,6-tris(dimethylaminomethyl)phenol (DMP-30) was used as an accelerator. The synthesized MNP@CS / DNA nanocomposites were incorporated in the range of 0 to 10 wt% (0, 1, 2, 5, and 10 wt%). The compositions of each final resin are shown in Table 3 of the supporting information. The mixtures of RDGE, BDMA, DMP-30, and MNP@CS / DNA were poured into the Teflon mold, and the initial curing was performed in an oven at 80°C for 1 h. The second curing step was performed in an oven at 130°C for 30 minutes.

[0125] Composition of epoxy composite (wt%)RDGEBDMADMP-30MNP@CS / DNA952.52.50942.52.51932.52.52902.52.55852.52.510

[0126] In particular, MNP@CS / DNA has temperature-independent magnetic properties. Utilizing these properties, the MNP@CS / DNA nanofillers were uniformly and unidirectionally aligned within the epoxy matrix, as shown in Fig. 4a. Consequently, the MNP@CS / DNA nanofillers were uniformly distributed within the epoxy matrix, indicating that manufacturing stability and a heat dissipation path were established. The heat dissipation properties were obtained by varying the concentration of MNP@CS / DNA nanofillers within the epoxy matrix through laser flash analysis (LFA). The results are summarized in Table 4 below.

[0127] MNP@CS / DNA weight ratio (wt%) density (g cm -3 )Specific heat (kJ·kg) -1 ·K -1 )Thermal diffusivity (mm)2 / s -1 )Thermal conductivity( W·m-1K-1 )01.531.1300.1400.242101.801.1510.1410.292201.881.1650.1510.330302.391.1780.1660.467402.091.1350.1690.402501.791.1400.1800.369

[0128] The thermal diffusivity and thermal conductivity of MNP@CS / DNA in the epoxy matrix are defined by Equation 1:

[0129] , (Formula 1)

[0130] Here, k is thermal conductivity, α is thermal diffusivity, ρ is density, and c p is the constant pressure specific heat.

[0131] The thermal diffusivity of the epoxy matrix increased with increasing content of MNP@CS / DNA nanofiller. This result indicates that the distribution of MNP@CS / DNA nanofiller can promote rapid diffusion of thermal energy within the epoxy matrix. With respect to the thermal conductivity presented in Fig. 4b and Table 5 below, 30 wt% MNP@CS / DNA nanofiller exhibited a maximum thermal conductivity of 0.467 W m in the epoxy matrix. -1 K -1 The value of was indicated.

[0132] Particle Type MNP@SiO2 MNP@CS / DNA(1BL) MNP@CS / DNA(3BL) MNP@CS / DNA(5BL) MNP@CS / DNA(7BL) MNP@CS / DNA(10BL) LOI (%) 21±0.92 24.23±0.76 27.70±0.23 29.34±0.45 31.23±0.62 32.62±0.56

[0133] However, when the filler content exceeded 30 wt%, the thermal conductivity tended to decrease. This decrease is due to the phenomenon of thermal energy transfer when the nanofillers collide with each other as the thermal energy moves from the high-temperature region to the low-temperature region within the material. This phenomenon indicates that when the filler content exceeded 30 wt%, the arrangement of the nanofillers was disturbed due to magnetization, preventing unidirectional heat conduction. Through Fig. 4c, the thermal conductivity of the sample containing 30 wt% MNP@CS / DNA filler was confirmed at each temperature. Importantly, the MNP@CS / DNA nanofiller formed a nanochar network within the epoxy matrix at approximately 300°C. The nanochar of MNP@CS / DNA within the epoxy matrix can perform a heat dissipation function, and the thermal conductivity was 0.171 W m at 30 wt%. -1 K -1 It exhibits thermal conductivity and performs heat blocking function. This suggests that MNP@CS / DNA can switch from heat dissipation to heat insulation at a certain critical temperature (about 300℃ or higher) in the epoxy matrix. In the case of any untreated epoxy or conventional filler, the thermal conductivity increases as the temperature increases, so the material easily reaches the ignition temperature because it absorbs heat, making it vulnerable to fire. The heat-insulating switching flame retardant material according to the present invention can perform the heat dissipation function at room temperature, but as the temperature increases, the matrix nanochar is formed and heat blocking proceeds in accordance with the thermal properties of the previous filler. Finally, the heat is blocked at about 300℃, which can prevent the risk of fire at the ignition temperature of the plastic.

[0134] Figure 4d is a diagram showing the thermal conductivity of the present invention (This work) and other materials applied to the epoxy matrix according to the content of the epoxy filler. Referring to this, the heat-insulating switching flame retardant material of the present invention not only has the unique characteristic of switching between heat dissipation and insulation, but also exhibits high thermal conductivity values ​​even with a low nanofiller content compared to other materials applied to the epoxy matrix.

[0135] Therefore, the MNP@CS / DNA nanofiller can act as a thermal interface material (TIM) exhibiting heat dissipation properties within the epoxy matrix, as depicted in Fig. 4e.

[0136] For heat-dissipating materials, nanofillers that directly convert to heat-insulating materials have not been reported to date. Therefore, developing a standardized evaluation to analyze the transition between heat dissipation and insulation properties of heat-converting nanofillers is currently challenging. However, because achieving high flame retardancy in electronic devices has only recently become increasingly important, few studies have investigated both the insulation and flame retardancy properties of epoxy resins.

[0137] Finally, the flame retardancy properties of epoxy resins containing different weight percentages of MNP@CS / DNA were comprehensively evaluated using the UL94 vertical test, as shown in Fig. 4f. The evaluated epoxy matrices contained 0, 1, 2, 5, and 10 wt% nanofillers. The UL 94 vertical test is a recognized standard for evaluating flammability, applying a controlled flame to vertically positioned samples to consider factors such as flame propagation, flame duration, and droplet formation behavior.

[0138] Significantly, the epoxy composite containing 10 wt% MNP@CS / DNA exhibited excellent flame retardancy performance, achieving a V-0 rating within the UL 94 classification. The composite containing 5 wt% MNP@CS / DNA also achieved a V-1 rating. As shown in Fig. 4g, a limiting oxygen index (LOI) test was performed using the epoxy resin specimen containing 10 wt% MNP@CS / DNA. Through the LOI test, it was found that the 10 wt% MNP@CS / DNA specimen achieved an LOI of 32.7%, which can be considered a high LOI value among several previous inventions and studies.

[0139] These results demonstrate self-extinguishing behavior and the absence of burning droplets immediately after removal of the ignition source. This result, as depicted in Figure 4h, is attributed to synergistic effects such as the cooperation between expansion, barrier formation, nanochar formation, and radical scavenging ability. These results are highly significant, suggesting that the heat-converting nanofiller according to the present invention can achieve not only insulating properties but also high flame retardancy in epoxy resins.

[0140] Smoke is a major factor that directly affects chain ignition and human casualties in fire accidents. Therefore, smoke suppression is a commonly analyzed indicator along with flame retardancy and thermal insulation properties. As shown in Figure 5a, the black smoke observed in a commonly used untreated epoxy was significantly reduced when 30 wt% MNP@CS / DNA nanofiller was doped into the matrix. The images of the combustion samples after doping with MNP@CS / DNA nanofiller show that the char generated by the nanofiller effectively extinguished the flame while maintaining its original shape as much as possible.

[0141] As shown in Fig. 5b, the gases were analyzed using a detector, and explosive gases (Exp) such as O2, CO, and CH₄ were recorded as concentration profiles for up to 150 seconds. For the untreated epoxy, O2 decreased to 18.6 vol%. For CO, a maximum of 250 ppm was released 39 seconds after ignition, which is a level at which carbon monoxide poisoning can cause confusion, unconsciousness, or even death. The flammable explosive gases also increased to 6 vol%. However, for the epoxy matrix containing MNP@CS / DNA, the CO level increased to 99 ppm after 40 seconds, indicating a 60.4% reduction in carbon monoxide production compared to the untreated epoxy. Other values ​​remained at typical levels and recovered to below 25 ppm, which is within the normal range, after 76 seconds. These results suggest that MNP@CS / DNA is a material that can reduce toxic gas production during combustion.

[0142] For further applications of the MNP@CS / DNA nanofiller, the mechanical properties of the epoxy matrix were investigated according to ASTM D 638 Type I. As shown in the left figure of Fig. 6, the color of the samples gradually changed as the MNP@CS / DNA content increased from 0 to 10 wt%. The right figure of Fig. 6 presents the strain-stress curves of each specimen. All materials exhibited failure characteristics in the plastic region beyond the elastic region. A significant change in Young's modulus was observed as the content exceeded 10 wt%. In addition, the uniform dispersion of MNP@CS / DNA within the epoxy matrix enhanced the fracture toughness of the system, which was indicated by a larger strain-stress curve of the nanocomposite system. This suggests that MNP@CS / DNA can improve the mechanical properties of the epoxy matrix.

[0143] In this paper, we comprehensively explored the multifaceted potential of MNP@CS / DNA as an advanced nanofiller for various applications. Through a step-by-step synthetic process, we obtained MNP@CS / DNA with an innovative multilayer organic structure. This unique organic layer composed of CS and DNA exhibited outstanding versatility and efficiency in various applications. Through various characterizations, we revealed the excellent thermal conversion properties of MNP@CS / DNA. As a magnetized, aligned thermal conversion nanofiller, MNP@CS / DNA intercalates into the epoxy matrix at the curing temperature, forming nanochar chains that serve as heat conduction channels. This results in a thermal conductivity of 0.467 W m, which cannot be achieved with pure MNP. -1 K -1 It provides a thermal conductivity of 0.171 W m. However, at the critical temperature (over 300°C), the expandable nanochar layer formed by the organizational decomposition of the flame-retardant organic layer forms an effective barrier to heat conduction and flame propagation, resulting in a thermal conductivity of 0.171 W m. -1 K -1 It achieved a V-0 rating in the UL 94 vertical test and a thermal conductivity of 0.012. This suggests that MNP@CS / DNA can change its thermal properties from heat dissipation to insulation and flame retardancy depending on the critical temperature. Furthermore, a LOI of 32.7% was achieved with 10 wt% filler doping. Furthermore, the heat conversion filler was able to reduce carbon monoxide (CO) emissions in smoke, which is considered the most dangerous factor in fire accidents, by 60.4%.

[0144] The synthesized MNP@CS / DNA thermal-switching nanofiller presents a promising future as an advanced material. Its versatile properties, including thermal conductivity, flame retardancy, mechanical strength, and biocompatibility, hold great potential in a variety of fields, from construction to electronics. In summary, this study demonstrates the transformative potential of MNP@CS / DNA as a thermal-switching nanofiller, and it can serve as a blueprint for designing innovative and eco-friendly materials that not only offer immediate practical applications but also simultaneously enhance safety, performance, and environmental protection.

[0145]

[0146] Although the present invention has been described above with reference to preferred embodiments thereof, it will be understood by those skilled in the art that various modifications and changes may be made to the present invention without departing from the spirit and scope of the present invention as set forth in the claims below.

Claims

1. Core particles; and Containing a flame retardant organic layer that generates char, Heat-insulating switching flame retardant material.

2. In paragraph 1, further comprising a positively charged polymer layer, The flame retardant organic layer and the positively charged polymer layer are alternately coated on the surface of the core particle. Heat-insulating switching flame retardant material.

3. In paragraph 1, The above flame retardant organic layer contains phosphorus, Heat-insulating switching flame retardant material.

4. In paragraph 3, The above flame retardant organic layer comprises nucleotides or phytic acid, Heat-insulating switching flame retardant material.

5. In paragraph 4, The above nucleotides include nucleic acids, NTPs or dNTPs. Heat-insulating switching flame retardant material.

6. In paragraph 5, The nucleic acid comprises DNA or RNA, Heat-insulating switching flame retardant material.

7. In paragraph 5, The above NTP comprises any one selected from the group consisting of ATP, GTP, CTP, TTP and UTP, The above dNTP comprises any one selected from the group consisting of dATP, dGTP, dCTP, dTTP and dUTP. Heat-insulating switching flame retardant material.

8. In paragraph 2, The positively charged polymer layer comprises an amine group, Heat-insulating switching flame retardant material.

9. In paragraph 8, The polymer containing the above amine group includes chitosan, Poly(L-lysine), Poly(ethyleneimine), Poly(β-amino ester) or Poly(amidoamine). Heat-insulating switching flame retardant material.

10. In paragraph 1, The core particles include metal oxide or ceramic particles, Heat-insulating switching flame retardant material.

11. In paragraph 10, The metal oxide or ceramic particles are characterized in that they have magnetism. Heat-insulating switching flame retardant material.

12. In paragraph 11, The above metal oxide includes magnetite (Fe3O4), hematite (Fe2O3) or ferrite. Heat-insulating switching flame retardant material.

13. In paragraph 1, The above core particles have a silica (SiO2) coating on their surface to form a core-shell structure. Heat-insulating switching flame retardant material.

14. In paragraph 1, The diameter of the above heat-insulating switching flame retardant material is 300 nm to 400 nm, Heat-insulating switching flame retardant material.

15. In paragraph 1, It is characterized by having heat dissipation properties at low temperatures and insulation and flame retardancy properties at high temperatures due to the formation of nano-char. Heat-insulating switching flame retardant material.

16. In paragraph 15, The above heat-insulating switching flame retardant material is characterized by forming the nano-char at a temperature of 300°C or higher. Heat-insulating switching flame retardant material.

17. Step 1: Preparing core particles; A second step of forming a first layer by coating the surface of the core particle with either a flame-retardant organic material or a positively charged polymer material; and A third step of forming a second layer by coating a flame-retardant organic material and a positively charged polymer material different from the first layer on the first layer, Method for manufacturing a heat-insulating switching flame retardant material.

18. In paragraph 17, The second and third steps are repeated two or more times so that the flame retardant organic material and the positively charged polymer material are alternately coated. Method for manufacturing a heat-insulating switching flame retardant material.

19. In paragraph 17, The above flame retardant organic material contains phosphorus, Method for manufacturing a heat-insulating switching flame retardant material.

20. In paragraph 19, The above flame retardant organic material comprises nucleotides or phytic acid. Method for manufacturing a heat-insulating switching flame retardant material.

21. In paragraph 20, The above nucleotides include nucleic acids, NTPs or dNTPs. Method for manufacturing a heat-insulating switching flame retardant material.

22. In paragraph 21, The nucleic acid comprises DNA or RNA, Method for manufacturing a heat-insulating switching flame retardant material.

23. In paragraph 21, The above NTP comprises any one selected from the group consisting of ATP, GTP, CTP, TTP and UTP, The above dNTP comprises any one selected from the group consisting of dATP, dGTP, dCTP, dTTP and dUTP. Method for manufacturing a heat-insulating switching flame retardant material.

24. In paragraph 17, The above positively charged polymer material contains an amine group, Method for manufacturing a heat-insulating switching flame retardant material.

25. In paragraph 24, The polymer containing the above amine group includes chitosan, Poly(L-lysine), Poly(ethyleneimine), Poly(β-amino ester) or Poly(amidoamine). Method for manufacturing a heat-insulating switching flame retardant material.

26. In paragraph 17, The core particles include metal oxide or ceramic particles, Method for manufacturing a heat-insulating switching flame retardant material.

27. In paragraph 26, The metal oxide or ceramic particles are characterized in that they have magnetism. Method for manufacturing a heat-insulating switching flame retardant material.

28. In paragraph 27, The above metal oxide includes magnetite (Fe3O4), hematite (Fe2O3) or ferrite. Method for manufacturing a heat-insulating switching flame retardant material.

29. In paragraph 17, The above core particles have a silica (SiO2) coating on their surface to form a core-shell structure. Method for manufacturing a heat-insulating switching flame retardant material.

30. In paragraph 17, The first step is to prepare a mixture containing a precursor of the core particle by solvothermal treatment and then cooling it. Method for manufacturing a heat-insulating switching flame retardant material.

31. In paragraph 17, A fourth step of dispersing the coated core particles into a matrix resin and curing them is additionally included. Method for manufacturing a heat-insulating switching flame retardant material.

32. In paragraph 31, The above matrix resin includes an epoxy matrix, a silicone matrix, a urethane matrix or an acrylic matrix resin. Method for manufacturing a heat-insulating switching flame retardant material.

33. A heat-insulating switching flame retardant material manufactured according to the method of manufacturing the heat-insulating switching flame retardant material according to any one of the items 17 to 32. Heat-insulating switching flame retardant material.

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