Expandable composition and preparation method thereof, fiber paper, insulating film and electric equipment

Abstract

The invention provides an expandable composition and a preparation method thereof, fiber paper, an insulating film and electric equipment, the expandable composition comprises a resin matrix, liquid crystal resin, an expandable material and an auxiliary agent, the liquid crystal resin is added into the resin matrix, the liquid crystal resin has the characteristics of liquid crystal and is regular in structural arrangement, the thermal conductivity of the composition is improved, and the thermal conductivity of the expandable material is improved. Meanwhile, the uniform distribution of the expandable material can be improved, so that when the composition is heated, each point of the composition is uniformly heated, and the uniform expansion of the composition is facilitated.

Description

Technical Field

[0001] This application relates to the field of insulating materials, and more particularly to an expandable composition and its preparation method, fiber paper, insulating film and electrical equipment. Background Technology

[0002] Insulating film is an important insulating material used in electrical equipment. It has good insulation properties, mechanical strength and heat resistance, and is widely used in various motors, transformers and other electrical equipment.

[0003] Insulating films are generally made of expandable insulating materials. Under heating conditions, the expandable insulating materials expand to achieve fixation and insulation within the motor slot.

[0004] However, the insulating film needs to be inserted into the motor slot during use. During the heating process, uneven temperature may occur inside the insulating film, which may affect the overall expansion effect. Summary of the Invention

[0005] This application provides an expandable composition and its preparation method, as well as fiber paper, insulating film, and electrical equipment, aiming to improve the problem of uneven internal temperature that may exist in the insulating film during the heating process.

[0006] To achieve the above objectives, in a first aspect, embodiments of this application provide an expandable composition comprising a resin matrix, a liquid crystal resin, an expandable material, and additives.

[0007] Optionally, in some embodiments of this application, the mass percentage of the liquid crystal resin in the expandable composition ranges from 5% to 15%.

[0008] Preferably, the mass percentage of the liquid crystal resin in the expandable composition ranges from 8% to 13%.

[0009] Optionally, in some embodiments of this application, the liquid crystal resin includes at least:

[0010] Resin carrier;

[0011] A liquid crystal cell is used to improve the thermal conductivity of the liquid crystal resin, and the liquid crystal cell is embedded in the resin carrier.

[0012] Optionally, in some embodiments of this application, the liquid crystal unit includes at least one of azo double bond-bridged diphenyl, carbon-nitrogen double bond-bridged diphenyl, carbon-carbon double bond-bridged diphenyl, biphenyl, bipyridyl, diphenylcyclohexyl, and diphenyl ester.

[0013] Optionally, in some embodiments of this application, the resin carrier includes at least one selected from epoxy resin, acrylate, polyester, polystyrene, and polyimide.

[0014] Optionally, in some embodiments of this application, the number-average molecular weight of the liquid crystal resin ranges from 300 to 8000.

[0015] Optionally, in some embodiments of this application, the resin matrix comprises an aqueous resin;

[0016] The waterborne resin includes at least one of waterborne epoxy resin, acrylate resin, and waterborne polyurethane resin.

[0017] Optionally, in some embodiments of this application, the expandable material includes at least one of polymeric shape memory material, expandable graphite, expandable physical microspheres, and expandable microcapsules.

[0018] Optionally, in some embodiments of this application, the mass percentage of the expandable material in the expandable composition ranges from 5% to 15%.

[0019] Optionally, in some embodiments of this application, the additives include at least one of curing agents, accelerators, coupling agents, defoamers, and stabilizers.

[0020] Optionally, in some embodiments of this application, the curing agent includes at least one of amine curing agents, phenolic curing agents, and acid anhydride curing agents; and / or

[0021] The accelerator includes at least one of amine accelerators, organophosphorus accelerators, ionic accelerators, and imidazole accelerators; and / or

[0022] The coupling agent includes at least one of silane coupling agents, titanate coupling agents, aluminate coupling agents, phosphate coupling agents, and borate coupling agents; and / or

[0023] The defoamer includes at least one of silicone oil, fatty alcohol, and liquid paraffin; and / or

[0024] The stabilizer includes at least one of phosphorus-based heat stabilizers, organotin stabilizers, and metal soap stabilizers.

[0025] Optionally, in some embodiments of this application, the expandable composition comprises the following components in parts by weight:

[0026]

[0027]

[0028] Optionally, in some embodiments of this application, the expandable composition further includes an epoxy emulsion;

[0029] The epoxy emulsion includes ester-modified epoxy emulsions.

[0030] Optionally, in some embodiments of this application, the ester-modified epoxy emulsion includes at least one of acrylate-modified epoxy emulsion, polyester-modified epoxy emulsion, and fatty acid ester-modified epoxy emulsion.

[0031] Optionally, in some embodiments of this application, the mass ratio of the liquid crystal resin to the ester-modified epoxy emulsion ranges from 0.25 to 0.5.

[0032] Optionally, in some embodiments of this application, the expandable composition comprises the following components in parts by weight:

[0033]

[0034] Optionally, in some embodiments of this application, the in-plane thermal conductivity of the expandable composition ranges from 0.18 W / (m·K) to 0.24 W / (m·K); and / or

[0035] The difference in expansion thickness of the expandable composition ranges from 37 mm to 53 mm.

[0036] Secondly, embodiments of this application provide a method for preparing an expandable composition, used to prepare the expandable composition as described above, the preparation method comprising the following steps:

[0037] The expandable composition is prepared by uniformly dispersing the resin matrix, liquid crystal resin, expandable material and additives, followed by vacuum degassing.

[0038] Optionally, in some embodiments of this application, the step of uniformly dispersing the resin matrix, liquid crystal resin, expandable material, and additives includes:

[0039] The resin matrix, liquid crystal resin, ester-modified epoxy emulsion, expandable materials and additives are uniformly dispersed.

[0040] Thirdly, embodiments of this application provide a fiber paper, which includes fibers and an expandable composition as described above.

[0041] Optionally, in some embodiments of this application, the fiber includes at least one of aramid fiber, boron fiber, aramid sulfone fiber, and polyester fiber.

[0042] Fourthly, embodiments of this application provide an insulating film, the insulating film comprising the fiber paper as described above.

[0043] Fifthly, embodiments of this application provide an electrical device, the electrical device including the insulating film as described above.

[0044] The expandable composition of this application includes a liquid crystal resin. The liquid crystal resin has the characteristics of liquid crystal and a regular structure, which is beneficial to improving the thermal conductivity of the composition. It also helps to improve the uniform distribution of the expandable material, so that when the composition is heated, all points of the composition are heated evenly, which is beneficial to the uniform expansion of the composition. Attached Figure Description

[0045] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0046] Figure 1 This is the chemical structural formula of the liquid crystal resin in some embodiments of this application;

[0047] Figure 2 This is a flowchart of a method for preparing liquid crystal resin in some embodiments of this application;

[0048] Figure 3 The chemical formula of the reaction process in Example 1 of this application is shown.

[0049] Figure 4 This is the chemical structural formula of the liquid crystal resin in Example 8 of this application;

[0050] Figure 5 This is the chemical structural formula of the liquid crystal resin in Example 9 of this application;

[0051] Figure 6 These are comparison images of the insulating film before and after expansion in some embodiments of this application. Detailed Implementation

[0052] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the protection scope of this application.

[0053] Insulating paper is an important insulating material used in electrical equipment. It has good insulation properties, mechanical strength and heat resistance, and is widely used in various motors, transformers and other electrical equipment to ensure the safe and reliable operation of these devices.

[0054] In recent years, the development of expandable insulating materials has replaced the function of existing drip-on paint, while also requiring the ability to fix and insulate within motor slots. Expandable insulating materials need to expand under heating conditions to achieve the desired fixation and insulation effects within the slots; however, the uniformity of expansion is related to the overall thermal conductivity of the material. Since this material needs to be inserted into the motor slots during use, temperature differences between different points within the material are inevitable during heating, thus affecting the overall expansion effect.

[0055] In view of this, there is an urgent need to develop an expandable insulating material with high thermal conductivity to make the temperature at different points similar, thereby ensuring the uniformity of material expansion and the reliability of its fixation.

[0056] According to a first aspect of the embodiments of this application, an expandable composition is provided, the expandable composition comprising a resin matrix, a liquid crystal resin, an expandable material, and additives.

[0057] By adopting the above scheme, liquid crystal resin is added to the resin matrix. Liquid crystal resin has the characteristics of liquid crystal and has a regular structure, which is beneficial to improving the thermal conductivity of the composition. It also helps to improve the uniform distribution of the expandable material, so that when the composition is heated, all points of the composition are heated evenly, which is beneficial to the uniform expansion of the composition.

[0058] It should be noted that liquid crystal resin is a type of high molecular liquid crystal material, also called liquid crystal polymer. It exhibits anisotropy under certain heating conditions. Adding liquid crystal resin helps to form thermally conductive pathways inside the composition, thereby dispersing local heat during equipment operation and avoiding performance degradation caused by local heating.

[0059] In some embodiments of this application, the mass percentage of liquid crystal resin in the expandable composition ranges from 5% to 15%. Further, the mass percentage of liquid crystal resin in the expandable composition ranges from 8% to 13%. Exemplarily, the mass percentage of liquid crystal resin in the expandable composition is 8%, 9%, 10%, 11%, 12%, 13%, and any value between two adjacent values.

[0060] By adopting the above scheme, the appropriate amount of liquid crystal resin helps to make the composition have a continuous thermal conduction path, thereby ensuring that the expansion of each point of the composition is uniform when heated.

[0061] For some embodiments of this application, please refer to Figure 1 The liquid crystal resin includes at least:

[0062] Resin carrier;

[0063] A liquid crystal cell is used to improve the thermal conductivity of liquid crystal resin. The liquid crystal cell is embedded in a resin carrier.

[0064] By adopting the above scheme, the liquid crystal resin includes a resin carrier and liquid crystal cells embedded on the resin carrier. Since the liquid crystal cells can improve the thermal conductivity of the liquid crystal resin, the addition of the liquid crystal resin helps to improve the uniformity of the expansion of the composition when heated.

[0065] It should be noted that liquid crystal resin is made by modifying a resin carrier using liquid crystal cells. The liquid crystal cells are arranged in an ordered manner through hydrogen bonds or van der Waals forces, thereby giving the liquid crystal resin both fluidity and crystal orientation.

[0066] In some embodiments of this application, the liquid crystal cell may include at least one of the following: azo double bond-bridged diphenyl, carbon-nitrogen double bond-bridged diphenyl, carbon-carbon double bond-bridged diphenyl, biphenyl, bipyridyl, diphenylcyclohexyl, and diphenyl ester.

[0067] It is understandable that diphenyl groups bridged by azo double bonds, diphenyl groups bridged by carbon-nitrogen double bonds, diphenyl groups bridged by carbon-carbon double bonds, biphenyl, bipyridyl, diphenylcyclohexyl, and diphenyl ester groups all possess liquid crystal properties, which helps to improve the structural regularity of liquid crystal resins. Moreover, the aforementioned types of liquid crystal units have rigidity and conjugated structures, which can ensure the stability of liquid crystal resin properties at high temperatures, while also improving the mechanical strength and modulus of liquid crystal resins.

[0068] In some embodiments of this application, the molar percentage of the liquid crystal cell in the liquid crystal resin ranges from 25% to 40%.

[0069] By adopting the above scheme, an appropriate content of liquid crystal cells in the liquid crystal resin helps to optimize the formation and stability of the liquid crystal phase in the liquid crystal resin. At the same time, the rigid structure of the liquid crystal cells can provide a good heat conduction path, which helps to improve the thermal conductivity of the liquid crystal resin.

[0070] In some embodiments of this application, the resin carrier includes at least one selected from epoxy resin, acrylate, polyester, polystyrene, and polyimide.

[0071] By adopting the above schemes, epoxy resin-based resins can form a rigid network structure through a curing reaction, suitable for bonding and coating applications on various substrates and for applications requiring high mechanical properties; acrylate-based resins have excellent transparency, good flexibility, and adhesion, suitable for applications requiring high transparency and high flexibility; polyester-based resins can support the directional alignment of liquid crystal cells, providing high tensile strength, while also having good flexibility, which is beneficial for buffering expansion stress; polystyrene-based resins have good transparency and excellent heat resistance, suitable for applications requiring high transparency and heat resistance; and polyimide-based resins have good high-temperature resistance, and the thermal conductivity of polyimide-based resins is significantly enhanced.

[0072] It should be noted that the liquid crystal resin used in the embodiments of this application can be commercially available or homemade.

[0073] The commercially available grades of liquid crystal resins in this application embodiment can be ICTE, LCTs, LCP, etc. If they are to be used in an aqueous system, the commercially available liquid crystal resin can be dissolved in a solvent. For example, the solvent can be at least one of ketone solvents, alcohol solvents, and alcohol ether solvents; for example, the ketone solvent can be acetone or cyclohexanone; the alcohol solvent can be ethanol; and the alcohol ether solvent can be at least one of propylene glycol methyl ether and ethylene glycol methyl ether.

[0074] If the liquid crystal resin used in the embodiments of this application needs to be prepared in-house, please refer to the preparation method. Figure 2 It includes the following steps:

[0075] S100. The raw material containing the resin carrier is dispersed in the first solvent to obtain the first mixture;

[0076] S200: Add raw materials containing liquid crystal units to the first mixture, and obtain liquid crystal resin through polycondensation reaction.

[0077] By adopting the above scheme, the raw materials containing the resin carrier are dispersed in the first solvent to obtain the first mixture, which helps to achieve uniform dispersion of the first mixture; then, the raw materials containing liquid crystal units are added to the first mixture, and the appropriate polycondensation reaction conditions are adjusted to achieve the preparation of liquid crystal resin.

[0078] In some embodiments of this application, the first solvent includes, but is not limited to, at least one of propylene glycol methyl ether, ethanol, ethylene glycol butyl ether, dimethylformamide, dimethyl sulfoxide, acetone, acetonitrile, dimethylacetamide, sulfolane, diethyl ether, tetrahydrofuran, and methyl ethyl ketone.

[0079] By adopting the above scheme, the first solvents are all organic solvents with good dissolving ability. Selecting different first solvents according to the properties of the resin carrier helps to fully dissolve different resin carriers. Moreover, the first solvent also helps to improve the dispersibility of the resin carrier and promotes the reaction between the resin carrier and the raw materials containing liquid crystal units.

[0080] In some embodiments of this application, the step of adding a raw material containing liquid crystal units to a first mixture and then performing a polycondensation reaction to obtain a liquid crystal resin includes:

[0081] The raw material containing liquid crystal units is dispersed in a second solvent to obtain a second mixture;

[0082] A second mixture is added dropwise to a first mixture, and a condensation reaction is carried out to obtain a liquid crystal resin.

[0083] By adopting the above scheme, the raw materials containing liquid crystal units are first fully dispersed using a second solvent, and then a second mixture is added to the first mixture, which is beneficial to the controllability of the reaction, thereby enabling the introduction of more liquid crystal units onto the resin carrier.

[0084] In some embodiments of this application, the raw material containing liquid crystal cells may include a diamine monomer containing liquid crystal cells. The range of selectable liquid crystal cells is the same as that described above.

[0085] In some embodiments of this application, the step of adding a raw material containing liquid crystal units to a first mixture and then performing a polycondensation reaction to obtain a liquid crystal resin includes:

[0086] A raw material containing liquid crystal units is added to a first mixture, and a polycondensation reaction is carried out to obtain a first liquid crystal.

[0087] A neutralizing agent is added to the first liquid crystal to obtain the second liquid crystal;

[0088] Water was added to the second liquid crystal and stirred to obtain liquid crystal resin.

[0089] By adopting the above scheme and adding a neutralizing agent, it is helpful for the liquid crystal resin to form salts to improve its hydrophilicity, making it suitable for subsequent aquatic applications.

[0090] In some embodiments of this application, the neutralizing agent includes, but is not limited to, at least one of hydrochloric acid, glacial acetic acid, lactic acid, phosphoric acid, guanidinoacetic acid, etc.

[0091] By adopting the above scheme, the neutralizing agent is selected as an acidic component, which helps to react with the first liquid crystal to form a salt, thereby improving the hydrophilicity of the liquid crystal.

[0092] In some embodiments of this application, the second solvent may be the same as or different from the first solvent. The second solvent includes, but is not limited to, at least one of propylene glycol methyl ether, ethanol, ethylene glycol butyl ether, dimethylformamide, dimethyl sulfoxide, acetone, acetonitrile, dimethylacetamide, sulfolane, diethyl ether, tetrahydrofuran, and methyl ethyl ketone.

[0093] In some embodiments of this application, the molar ratio of the raw material containing the resin carrier to the raw material containing the liquid crystal unit ranges from 1:(1.5 to 3).

[0094] By adopting the above scheme, the raw materials containing the resin carrier and the raw materials containing the liquid crystal units are configured in a suitable molar ratio, which helps to optimize the formation and stability of the liquid crystal phase, thereby ensuring the stability of the prepared liquid crystal resin. If the amount of raw materials containing liquid crystal units added is too small, a stable liquid crystal phase may not be formed; if the amount of raw materials containing liquid crystal units added is too large, the carrier will excessively restrict the movement of the liquid crystal units, affecting the thermal stability of the liquid crystal resin.

[0095] In some embodiments of this application, the number-average molecular weight of the liquid crystal resin ranges from 300 to 8000. Further, the number-average molecular weight of the liquid crystal resin ranges from 500 to 5000. Exemplarily, the number-average molecular weight of the liquid crystal resin can be 500, 800, 1000, 1200, 1500, 1700, 2000, 2300, 2500, 2700, 3000, 3200, 3500, 3800, 4000, 4300, 4500, 4800, 5000, or any value between two adjacent values.

[0096] Understandably, liquid crystal resins with a suitable number-average molecular weight range can combine the properties of liquid crystals with good flexibility. If the molecular weight of the liquid crystal resin is too large, it may result in insufficient flexibility of the expandable composition; if the molecular weight of the liquid crystal resin is too small, it may result in insufficient thermal conductivity of the expandable composition.

[0097] In some embodiments of this application, the in-plane thermal conductivity of the liquid crystal resin ranges from 0.1 W / m·K to 0.3 W / m·K. Exemplarily, the thermal conductivity of the liquid crystal resin can be 0.1 W / m·K, 0.12 W / m·K, 0.15 W / m·K, 0.18 W / m·K, 0.2 W / m·K, 0.22 W / m·K, 0.25 W / m·K, 0.27 W / m·K, 0.3 W / m·K, or any value between two adjacent values.

[0098] By adopting the above scheme, the greater the thermal conductivity of the liquid crystal resin, the better its thermal conductivity, which helps to improve the temperature rise uniformity of the expandable composition during heating.

[0099] In some embodiments of this application, the resin matrix includes an aqueous resin;

[0100] Among them, waterborne resins include at least one of waterborne epoxy resins, acrylate resins, and waterborne polyurethane resins.

[0101] By adopting the above solution, waterborne resins can be selected according to different application scenarios, including but not limited to waterborne epoxy resins, acrylate resins, and waterborne polyurethane resins.

[0102] It should be noted that the type of waterborne resin selected is the same as the type of resin carrier selected in the liquid crystal resin, or the type of waterborne resin selected is similar in nature to the type of resin carrier selected in the liquid crystal resin.

[0103] It should be noted that the aqueous resin in this application embodiment is a resin system in which water is used instead of organic solvent as the dispersion medium. The molecular chain of aqueous resin usually contains hydrophilic groups, such as carboxyl groups, hydroxyl groups, ether bonds, etc., or is stably dispersed in water by an emulsifier to form an emulsion, dispersion or aqueous solution.

[0104] In this application embodiment, the aqueous resin serves as the continuous phase of the expandable composition, providing a dispersion basis for the liquid crystal resin and the expandable material. Furthermore, the aqueous resin and the liquid crystal resin form an interpenetrating network, increasing the crosslinking density of the composition after curing, thereby enhancing the mechanical strength and heat resistance of the composition.

[0105] In some embodiments of this application, the mass percentage of the expandable material in the expandable composition ranges from 5% to 15%. Exemplarily, the mass percentage of the expandable material in the expandable composition is 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, and any value between two adjacent values.

[0106] By adopting the above scheme, the appropriate amount of expandable material helps to give the composition high thermal conductivity and expansion rate, thus giving the composition both good heat dissipation and expandability.

[0107] In some embodiments of this application, the expandable material includes at least one of polymeric shape memory material, expandable graphite, expandable physical microspheres, and expandable microcapsules.

[0108] By employing the above-mentioned methods, the polymer shape memory material can expand uniformly upon heating, ensuring uniform filling of the composition in the applicable scenario. Simultaneously, this material also possesses good mechanical strength and toughness, contributing to enhanced mechanical properties of the composition. Expanded graphite expands rapidly upon heating, significantly increasing its volume and effectively filling the space in the applicable scenario. Furthermore, expanded graphite forms a good insulating layer after expansion, improving the electrical insulation properties of the composition. Expanded physical microspheres expand uniformly upon heating, ensuring high expansion uniformity of the composition in all directions and avoiding problems caused by uneven local expansion. In addition, expanded physical microspheres have good processability, allowing for easy mixing and processing with other materials. Expanded microcapsules can be designed to achieve controllable expansion, releasing the internal expanding agent under specific conditions. By selecting different expanding materials, various properties can be optimized, such as expansion uniformity, thermal conductivity, mechanical properties, thermal stability, and electrical insulation.

[0109] For example, the average particle size of the expandable physical microspheres ranges from 15 μm to 40 μm, which helps to achieve both good processability and uniform expansion during heating.

[0110] In some embodiments of this application, the additives include at least one of curing agents, accelerators, coupling agents, defoamers, and stabilizers.

[0111] By adopting the above scheme, the additives are selected from at least one of curing agents, accelerators, coupling agents, defoamers, and stabilizers, which helps to improve the processing performance or overall performance of the composition, thereby ensuring that the prepared composition has high thermal conductivity, good expansion uniformity, etc.

[0112] In some embodiments of this application, the curing agent includes at least one of amine curing agents, phenolic curing agents, and acid anhydride curing agents.

[0113] By adopting the above scheme, amine curing agents can undergo ring-opening addition reactions with epoxy resin matrices to form a dense cross-linked structure; moreover, amine curing agents can cure at room temperature, but their heat resistance is slightly poor; phenol curing agents can react with hydroxyl / carboxyl groups in the resin matrix to generate ester bond networks, which helps to improve the heat resistance of the composition; phenol curing agents provide high cross-linking density and rigid benzene ring structure, which helps to improve the thermal stability of the composition.

[0114] In some embodiments of this application, the accelerator includes at least one of amine accelerators, organophosphorus accelerators, ionic accelerators, and imidazole accelerators.

[0115] By adopting the above schemes, amine accelerators can be pre-cured in low-temperature environments; organophosphorus accelerators help reduce the exothermic reaction and the generation of volatile gases, thereby reducing the porosity of the composition after expansion; ionic accelerators help improve the compatibility between the resin matrix and the expandable material, and help improve the interfacial bonding energy between the two, thereby resisting expansion stress; imidazole accelerators can play a slow-release role in the expansion effect, helping to reduce the volume expansion deviation rate of the composition.

[0116] In some embodiments of this application, the coupling agent includes at least one of silane coupling agents, titanate coupling agents, aluminate coupling agents, phosphate coupling agents, and borate coupling agents.

[0117] In some embodiments of this application, the defoamer includes at least one of silicone oil, fatty alcohol, and liquid paraffin.

[0118] In some embodiments of this application, the stabilizer includes at least one of phosphorus-based heat stabilizers, organotin stabilizers, and metal soap stabilizers.

[0119] It is understandable that phosphorus-based heat stabilizers, organotin stabilizers, and metal soap stabilizers are all common types of stabilizers on the market, and will not be elaborated on here.

[0120] In some embodiments of this application, the expandable composition comprises the following components in parts by weight:

[0121]

[0122] By adopting the above scheme, the expandable composition is obtained by compounding the components in the above mass parts, which helps the composition to be heated evenly at all points during heating, thereby ensuring the uniform expansion of the composition.

[0123] In some embodiments of this application, the expandable composition may also include an epoxy emulsion.

[0124] It is understandable that adding an epoxy emulsion to the composition, which has flexible segments, can improve the regularity of the liquid crystal resin to a certain extent, thereby promoting the regular arrangement of the liquid crystal resin.

[0125] In some embodiments of this application, the epoxy emulsion may include an ester-modified epoxy emulsion.

[0126] By adopting the above-mentioned approach, ester-modified epoxy emulsions help improve the flexibility of the composition; at the same time, ester-modified epoxy emulsions also help promote the uniform dispersion of liquid crystal resins and expandable materials in the resin matrix.

[0127] In some embodiments of this application, the ester-modified epoxy emulsion includes at least one of acrylate-modified epoxy emulsion, polyester-modified epoxy emulsion, and fatty acid ester-modified epoxy emulsion.

[0128] In some embodiments of this application, the mass ratio of liquid crystal resin to ester-modified epoxy emulsion ranges from 0.25 to 0.5.

[0129] By adopting the above scheme, the ester-modified epoxy emulsion has good flexibility. Blending the ester-modified epoxy emulsion with liquid crystal resin in an appropriate ratio helps to make the expandable composition have both uniform expansion and flexibility.

[0130] In some embodiments of this application, the expandable composition comprises the following components in parts by weight:

[0131]

[0132] In some embodiments of this application, the in-plane thermal conductivity of the expandable composition is from 0.18 W / (m·K) to 0.58 W / (m·K). Further, the in-plane thermal conductivity of the expandable composition is from 0.19 W / (m·K) to 0.55 W / (m·K). For example, the thermal conductivity of the expandable composition is 0.19 W / (m·k), 0.20 W / (m·k), 0.22 W / (m·k), 0.24 W / (m·k), 0.28 W / (m·k), 0.30 W / (m·k), 0.32 W / (m·k), 0.35 W / (m·k), 0.40 W / (m·k), 0.43 W / (m·k), 0.45 W / (m·k), 0.48 W / (m·k), 0.50 W / (m·k), 0.53 W / (m·k), 0.55 W / (m·k), and any value between two adjacent values.

[0133] In some embodiments of this application, the expansion thickness difference of the expandable composition is 37 mm to 61 mm. Exemplarily, the expansion thickness difference of the expandable composition can be 37 mm, 38 mm, 39 mm, 40 mm, 41 mm, 42 mm, 43 mm, 44 mm, 45 mm, 46 mm, 47 mm, 48 mm, 49 mm, 50 mm, 51 mm, 52 mm, 53 mm, 54 mm, 55 mm, 56 mm, 57 mm, 58 mm, 59 mm, 60 mm, 61 mm, and any value between two adjacent values.

[0134] According to a second aspect of the embodiments of this application, a method for preparing an expandable composition is provided, for preparing the expandable composition as described above, the method comprising the following steps:

[0135] The resin matrix, liquid crystal resin, expandable material and additives are uniformly dispersed and then degassed under vacuum to obtain an expandable composition.

[0136] By adopting the above scheme, water-based resin, liquid crystal resin, expandable material and additives are mixed, then dispersed at high speed and degassed under vacuum to obtain an expandable composition. The method is simple and suitable for industrial production.

[0137] In some embodiments of this application, the step of uniformly dispersing the resin matrix, liquid crystal resin, expandable material, and additives includes:

[0138] The resin matrix, liquid crystal resin, ester-modified epoxy emulsion, expandable materials and additives are uniformly dispersed.

[0139] In some embodiments of this application, the composition is prepared by the following method:

[0140] Materials: 35-50 parts water-based resin, 5-15 parts liquid crystal resin, 20-45 parts ester-modified epoxy emulsion, 5-15 parts expandable material, 1-5 parts curing agent, 0.1-3 parts accelerator, 1-5 parts adhesion promoter, 0.1-3 parts defoamer, and 0.1-3 parts stabilizer; Mix the above raw material components according to the proportions, add them to the reaction vessel, disperse at high speed, and then degas under vacuum to obtain the composition.

[0141] According to a third aspect of the embodiments of this application, a fiber paper is provided, the fiber paper comprising fibers and an expandable composition as described above.

[0142] By adopting the above-described solution, the fiber paper of this application embodiment has excellent insulation, heat resistance, mechanical strength, and expansion uniformity.

[0143] In some embodiments of this application, the fiber includes at least one of aramid fiber, boron fiber, aramid fiber, and polyester fiber.

[0144] For example, the fiber can be selected from aramid fiber, which helps to form a thermally conductive path in the fiber paper, effectively dispersing heat, thereby improving the thermal uniformity of the fiber paper during use. Aramid fiber can take into account insulation, heat resistance and processability.

[0145] Specifically, aramid fibers are chopped aramid fibers and precipitated aramid fibers. By using chopped aramid fibers and precipitated aramid fibers, the paper uniformity of the fiber paper can be guaranteed.

[0146] Specifically, the total mass of aramid fibers accounts for 70-95% of the fiber paper, and the mass percentage of the composition is 5% to 30%.

[0147] Specifically, the mass ratio of aramid chopped fibers to aramid precipitated fibers includes, but is not limited to, 3:7, 4:6, and 5:5.

[0148] In some embodiments of this application, the method for preparing fiber paper includes the following steps:

[0149] Aramid short-cut fibers and the composition were mixed in water and then decomposed using a decomposition machine;

[0150] Aramid precipitated fibers were added for secondary decomposition, and the mixture was obtained after stirring.

[0151] The mixture is poured into a paper forming machine with an inner diameter of 200 mm and dehydrated to obtain a wet sheet. The wet sheet is then subjected to flat cold pressing for 5 to 30 minutes, and then transferred to a paper dryer. It is dried at 60 to 100°C for 10 to 60 minutes, and then hot-pressed at 90 to 110°C and 5 to 20 MPa for 5 minutes to obtain fiber paper.

[0152] Then, the fiber paper is bonded to both sides of the polymer film with an adhesive, and the film is dried and calendered to obtain an insulating film.

[0153] In some embodiments of this application, the polymer film includes, but is not limited to, one of polyimide film and polyester film.

[0154] In some embodiments of this application, the thickness of the polymer film ranges from 25 μm to 1000 μm. Exemplarily, the thickness of the polymer film can be 25 μm, 50 μm, 75 μm, 100 μm, 150 μm, 200 μm, 250 μm, 300 μm, 400 μm, 500 μm, 600 μm, 700 μm, 800 μm, 900 μm, 1000 μm, or any value between two adjacent values.

[0155] In some embodiments of this application, the adhesive includes, but is not limited to, one of epoxy adhesives, acrylic resin adhesives, polyurethane adhesives, and silicone adhesives.

[0156] In some embodiments of this application, the adhesive application thickness ranges from 5 μm to 150 μm. Exemplarily, the adhesive application thickness can be 5 μm, 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, 110 μm, 120 μm, 130 μm, 140 μm, 150 μm, or any value between two adjacent values.

[0157] According to a fourth aspect of the embodiments of this application, an insulating film is provided, the insulating film comprising the fiber paper as described above.

[0158] By adopting the above solution, the insulating film of this application embodiment has a uniform temperature at each point when heated, that is, the expansion ratio of each point on the surface of the insulating film is similar when heated and expanded, so that the insulating film can fully fill the gap in the motor slot to effectively fill the gap in the motor slot, thereby ensuring the reliability of fixing the components inside the motor, and is suitable for long-term operation in high-temperature environments such as motors and transformers.

[0159] According to a fifth aspect of the embodiments of this application, an electrical device is provided, the electrical device including the insulating film as described above.

[0160] By adopting the above solution, the high thermal uniformity of the insulating film helps to disperse local heat during the operation of electrical equipment, avoiding performance degradation caused by severe local heating, thereby ensuring the fixing and insulation functions of the motor slot in the electrical equipment.

[0161] The present application will be specifically described below through specific embodiments. These embodiments are only some embodiments of the present application and are not intended to limit the present application. Unless otherwise specified, the raw materials used in the following embodiments are all commercially available products.

[0162] Example 1

[0163] An insulating film is prepared by the following method:

[0164] Preparation of liquid crystal resin:

[0165] Mix 3g of ethylene glycol butyl ether and 6g of ethanol to obtain a blend solution;

[0166] 50g of E-44 epoxy resin was dispersed in a blending solution to obtain the first mixture.

[0167] 18.75 g of p-diaminoazobenzene was dissolved in 100 mL of ethanol to obtain a second mixture;

[0168] The second mixture was slowly added dropwise to the first mixture. After the addition was complete, the temperature was raised to 90°C and the reaction was allowed to proceed for 3 hours. After the reaction was complete, 20 mL of glacial acetic acid was added dropwise to neutralize and form a salt, yielding a liquid crystal resin with a number-average molecular weight of 800. The reaction structure is shown in [reference needed]. Figure 3 ;

[0169] Preparation of the composition:

[0170] Materials: 40g waterborne bisphenol A type epoxy resin, 13g liquid crystal resin, 27g acrylate modified epoxy emulsion, 10g expanded physical microspheres, 5g amine curing agent D8, 0.5g imidazole accelerator U200, 1g silane coupling agent KH560, 0.6g silicone defoamer BYK-333, 0.2g polypropylene glycol stabilizer; wherein, the D50 particle size of the expanded physical microspheres is 20μm;

[0171] The above raw materials are dispersed at high speed and then degassed under vacuum to obtain the composition;

[0172] Preparation of insulating film:

[0173] The ingredients are prepared according to 84 wt% aramid fiber and 16 wt% composition. Specifically, 12.6 g of aramid chopped fiber and 8 g of composition are mixed in water and decomposed by a decomposition machine. Then, 29.4 g of aramid precipitated fiber is added for secondary decomposition to obtain a third mixture.

[0174] The third mixture is then poured into a paper forming machine with an inner diameter of 200 mm and dehydrated to obtain a wet sheet.

[0175] The wet sheet was cold-pressed on a flat plate for 5 minutes, then transferred to a paper dryer and dried at 80°C for 10 minutes. After low-temperature calendering at 105°C, fiber paper was obtained.

[0176] The adhesive is evenly applied to the surface of the fiber paper using a coating machine to obtain an insulating film coated with adhesive, with a coating thickness of 30 μm. The composite film is obtained by laminating the fiber paper-polyimide film-fiber paper in the following order. The composite film is placed in a desiccator and dried at 80°C for 10 min, and then hot-pressed at 105°C and 10 MPa for 5 min to obtain the insulating film.

[0177] Example 2

[0178] An insulating film is prepared by the following method:

[0179] Preparation of liquid crystal resin:

[0180] Mix 3g of ethylene glycol butyl ether and 6g of ethanol to obtain a blend solution;

[0181] 50g of E-44 epoxy resin was dispersed in a blending solution to obtain the first mixture.

[0182] 18.75 g of p-diaminoazobenzene was dissolved in 100 mL of ethanol to obtain a second mixture;

[0183] The second mixture was slowly added dropwise to the first mixture. After the addition was completed, the temperature was raised to 90°C and the reaction was allowed to proceed for 3 hours. After the reaction was complete, 20 mL of glacial acetic acid was added dropwise to neutralize and form a salt, thus obtaining a liquid crystal resin with a number average molecular weight of 800.

[0184] Preparation of the composition:

[0185] Materials: 40g waterborne bisphenol A type epoxy resin, 8g liquid crystal resin, 32g acrylate modified epoxy emulsion, 10g expanded physical microspheres, 5g amine curing agent D8, 0.5g imidazole accelerator U200, 1g silane coupling agent KH560, 0.6g silicone defoamer BYK-333, 0.12g polypropylene glycol stabilizer. The D50 particle size of the expanded physical microspheres is 20μm.

[0186] The above raw materials are dispersed at high speed and then degassed under vacuum to obtain the composition;

[0187] Preparation of insulating film:

[0188] The ingredients are prepared according to 84 wt% aramid fiber and 16 wt% composition. Specifically, 12.6 g of aramid chopped fiber and 8 g of composition are mixed in water and decomposed by a decomposition machine. Then, 29.4 g of aramid precipitated fiber is added for secondary decomposition to obtain a third mixture.

[0189] The third mixture is then poured into a paper forming machine with an inner diameter of 200 mm and dehydrated to obtain a wet sheet.

[0190] The wet sheet was cold-pressed in a flatbed for 5 minutes, then transferred to a paper dryer and dried at 80°C for 10 minutes. After low-temperature calendering at 105°C, fiber paper was obtained.

[0191] The adhesive is evenly applied to the surface of the fiber paper using a coating machine to obtain an insulating film coated with adhesive, with a coating thickness of 30 μm. The composite film is obtained by laminating the fiber paper-polyimide film-fiber paper in the following order. The composite film is placed in a desiccator and dried at 80°C for 10 min, and then hot-pressed at 105°C and 10 MPa for 5 min to obtain the insulating film.

[0192] Example 3

[0193] An insulating film is prepared by the following method:

[0194] Preparation of liquid crystal resin:

[0195] Mix 3g of ethylene glycol butyl ether and 6g of ethanol to obtain a blend solution;

[0196] 50g of E-44 epoxy resin was dispersed in a blending solution to obtain the first mixture.

[0197] 18.75 g of p-diaminoazobenzene was dissolved in 100 mL of ethanol to obtain a second mixture;

[0198] The second mixture was slowly added dropwise to the first mixture. After the addition was completed, the temperature was raised to 90°C and the reaction was allowed to proceed for 3 hours. After the reaction was complete, 20 mL of glacial acetic acid was added dropwise to neutralize and form a salt, thus obtaining the liquid crystal resin.

[0199] Preparation of the composition:

[0200] Materials: 40g waterborne bisphenol A type epoxy resin, 8g liquid crystal resin, 32g acrylate modified epoxy emulsion, 10g expanded physical microspheres, 5g amine curing agent D8, 0.5g imidazole accelerator U200, 1g silane coupling agent KH560, 0.6g silicone defoamer BYK-333, 0.12g polypropylene glycol stabilizer; wherein, the D50 particle size of the expanded physical microspheres is 20μm;

[0201] The above raw materials are dispersed at high speed and then degassed under vacuum to obtain the composition;

[0202] Preparation of insulating film:

[0203] The mixture is prepared according to 92 wt% aramid fiber and 8 wt% composition. Specifically, 13.8 g of aramid chopped fiber and 4 g of composition are mixed in water and decomposed by a decomposition machine. Then, 32.2 g of aramid precipitated fiber is added for secondary decomposition to obtain a third mixture.

[0204] The third mixture is then poured into a paper forming machine with an inner diameter of 200 mm and dehydrated to obtain a wet sheet.

[0205] The wet sheet was cold-pressed in a flatbed for 5 minutes, then transferred to a paper dryer and dried at 80°C for 10 minutes. After low-temperature calendering at 105°C, fiber paper was obtained.

[0206] The adhesive is evenly applied to the surface of the fiber paper using a coating machine to obtain fiber paper coated with adhesive, with a coating thickness of 30μm. The composite film is obtained by laminating the fiber paper-polyimide film-fiber paper in the following order. The composite film is placed in a desiccator and dried at 80℃ for 10min, and then hot-pressed at 105℃ and 10MPa for 5min to obtain an insulating film.

[0207] Example 4

[0208] An insulating film differs from Example 1 in that the composition formulation is different. The composition formulation in this example is as follows: 40g of waterborne bisphenol A type epoxy resin, 5g of liquid crystal resin, 35g of acrylate-modified epoxy emulsion, 10g of expanded physical microspheres, 5g of amine curing agent, 0.5g of imidazole accelerator, 1g of silane coupling agent, 0.6g of silicone defoamer, and 0.12g of polypropylene glycol stabilizer. The above raw materials are dispersed at high speed and degassed under vacuum to obtain the composition.

[0209] Example 5

[0210] An insulating film differs from Example 1 in that the composition formulation is different. The composition formulation in this example is as follows: 40g of waterborne bisphenol A type epoxy resin, 15g of liquid crystal resin, 25g of acrylate-modified epoxy emulsion, 10g of expanded physical microspheres, 5g of amine curing agent, 0.5g of imidazole accelerator, 1g of silane coupling agent, 0.6g of silicone defoamer, and 0.12g of polypropylene glycol stabilizer. The above raw materials are dispersed at high speed and degassed under vacuum to obtain the composition.

[0211] Example 6

[0212] An insulating film differs from Example 1 in that the composition formulation is different. The composition formulation in this example is: 40g of waterborne bisphenol A type epoxy resin, 8g of liquid crystal resin, 32g of acrylate-modified epoxy emulsion, 5g of expanded physical microspheres, 5g of amine curing agent, 0.5g of imidazole accelerator, 1g of silane coupling agent, 0.6g of silicone defoamer, and 0.12g of polypropylene glycol stabilizer. The above raw materials are dispersed at high speed and degassed under vacuum to obtain the composition.

[0213] Example 7

[0214] An insulating film differs from Example 1 in that the composition formulation is different. The composition formulation in this example is: 40g of waterborne bisphenol A type epoxy resin, 8g of liquid crystal resin, 32g of acrylate-modified epoxy emulsion, 15g of expanded physical microspheres, 5g of amine curing agent, 0.5g of imidazole accelerator, 1g of silane coupling agent, 0.6g of silicone defoamer, and 0.12g of polypropylene glycol stabilizer. The above raw materials are dispersed at high speed and degassed under vacuum to obtain the composition.

[0215] Example 8

[0216] An insulating film differs from that of Example 2 in that it uses a different liquid crystal resin. In this example, the liquid crystal resin is prepared using the following method:

[0217] Mix 3g of ethylene glycol butyl ether and 6g of ethanol to obtain a blend solution;

[0218] 50g of E-44 epoxy resin was dispersed in a blending solution to obtain the first mixture.

[0219] 20g of 4,4'-diamino-3,3'-dimethylhydroxybiphenylmethane was dissolved in 100mL of ethanol to obtain a second mixture;

[0220] The second mixture was slowly added dropwise to the first mixture. After the addition was complete, the temperature was raised to 90°C, and the reaction was allowed to proceed for 3 hours. After the reaction was complete, 20 mL of glacial acetic acid was added dropwise to neutralize and form a salt, yielding the liquid crystal resin. The reaction structure is shown in [reference needed]. Figure 4 .

[0221] Example 9

[0222] An insulating film differs from that of Example 2 in that it uses a different liquid crystal resin. In this example, the liquid crystal resin is prepared using the following method:

[0223] Mix 3g of ethylene glycol butyl ether and 6g of ethanol to obtain a blend solution;

[0224] 50g of E-44 epoxy resin was dispersed in a blending solution to obtain the first mixture.

[0225] 18g of 4,4'-diaminobibenzyl was dissolved in 100mL of ethanol to obtain a second mixture;

[0226] The second mixture was slowly added dropwise to the first mixture. After the addition was complete, the temperature was raised to 90°C, and the reaction was allowed to proceed for 3 hours. After the reaction was complete, 20 mL of glacial acetic acid was added dropwise to neutralize and form a salt, yielding the liquid crystal resin. The reaction structure is shown in [reference needed]. Figure 5 .

[0227] Example 10

[0228] An insulating film, differing from Example 1 in that it does not contain acrylate-modified epoxy emulsion. The formulation of the composition in this example is as follows: 40g of waterborne bisphenol A type epoxy resin, 40g of liquid crystal resin, 10g of expanded physical microspheres, 5g of amine curing agent D8, 0.5g of imidazole accelerator U200, 1g of silane coupling agent KH560, 0.6g of silicone defoamer BYK-333, and 0.12g of polypropylene glycol stabilizer, wherein the D50 particle size of the expanded physical microspheres is 20μm;

[0229] The above raw materials are dispersed at high speed and then degassed under vacuum to obtain the composition;

[0230] Comparative Example 1

[0231] An insulating film is prepared by the following method:

[0232] Mix 15g of aramid chopped fibers in water, then decompose them using a decomposition machine. Add 35g of aramid precipitated fibers for a second decomposition to obtain a mixed solution.

[0233] The mixture is then poured into a paper forming machine with an inner diameter of 200 mm and dehydrated to obtain a wet sheet;

[0234] The wet sheet was cold-pressed on a flat plate for 5 minutes, then transferred to a paper dryer and dried at 80°C for 10 minutes. After low-temperature calendering at 105°C, fiber paper was obtained.

[0235] The adhesive is evenly applied to the surface of the fiber paper using a coating machine to obtain fiber paper coated with adhesive, with a coating thickness of 30μm. The composite film is obtained by laminating the fiber paper-polyimide film-fiber paper in the following order. The composite film is placed in a desiccator and dried at 80℃ for 10min, and then hot-pressed at 105℃ and 10MPa for 5min to obtain an insulating film.

[0236] Comparative Example 2

[0237] An insulating film, differing from Example 1 in that no liquid crystal resin is added to the composition. The formulation of this comparative example is: 40g of waterborne bisphenol A type epoxy resin, 40g of acrylate modified epoxy emulsion, 10g of expanded physical microspheres, 5g of amine curing agent, 0.5g of imidazole accelerator, 1g of silane coupling agent, and 0.6g of organosilicon defoamer.

[0238] The above raw materials are dispersed at high speed and then degassed under vacuum to obtain the composition;

[0239] Preparation of insulating film:

[0240] 12.6g of aramid chopped fibers and 8g of the composition were mixed in water and decomposed using a decomposition machine. Then, 29.4g of aramid precipitated fibers were added for a second decomposition to obtain a third mixture.

[0241] The third mixture is then poured into a paper forming machine with an inner diameter of 200 mm and dehydrated to obtain a wet sheet.

[0242] The wet sheet was cold-pressed in a flatbed for 5 minutes, then transferred to a paper dryer and dried at 80°C for 10 minutes. After low-temperature calendering at 105°C, fiber paper was obtained.

[0243] The adhesive is evenly applied to the surface of the fiber paper using a coating machine to obtain fiber paper coated with adhesive, with a coating thickness of 30μm. The composite film is obtained by laminating the fiber paper-polyimide film-fiber paper in the following order. The composite film is placed in a desiccator and dried at 80℃ for 10min, and then hot-pressed at 105℃ and 10MPa for 5min to obtain an insulating film.

[0244] Detection methods:

[0245] (1) In-plane thermal conductivity:

[0246] The in-plane thermal conductivity of the samples from the examples and comparative examples was tested according to the standard GB / T 20039-2006.

[0247] (2) Uniformity of expansion:

[0248] A 15mm×180mm sample was prepared and heated at 150℃ for 15 minutes using a single-sided heat source. After cooling to room temperature, the thickness after expansion was measured at 10 points at different locations on the sample. The uniformity of expansion was judged based on the thickness difference.

[0249] (3) Expansion ratio:

[0250] The insulating films of the examples and comparative examples were heated to 150°C, and the dimensions of the expandable insulating paper before and after expansion in the thickness direction were tested. The expansion ratio was calculated using the following formula: Expansion ratio = Thickness dimension after expansion / Thickness dimension before expansion.

[0251] The test results are shown in Table 1:

[0252] Table 1

[0253]

[0254]

[0255] Compared with Comparative Examples 1 and 2, Example 10 contained liquid crystal resin, Comparative Example 1 contained only aramid fiber matrix without any composition, and Comparative Example 2 contained no liquid crystal resin. As shown in Table 1, the in-plane thermal conductivity of Comparative Examples 1 and 2 decreased significantly. Comparative Example 1 did not expand at all. Compared with Example 10, Comparative Example 2 had a similar expansion ratio, but the difference in expansion thickness was significantly increased. This is because liquid crystal resin helps to improve the thermal conductivity of the composition and also helps to improve the uniform distribution of the expandable material, ensuring that the composition is heated evenly at all points, thus contributing to the uniform expansion of the composition.

[0256] Compared to Examples 1-9 and Example 10, the composition, in addition to the liquid crystal resin, incorporates an acrylate-modified epoxy emulsion, which helps promote the orderly arrangement of the liquid crystal resin, thereby further improving the in-plane thermal conductivity of the composition. Furthermore, with similar expansion ratios, the difference in expansion thickness of the composition can be significantly reduced, resulting in better expansion uniformity of the insulating film and ensuring reliable fixation within the motor slot. Please refer to [link / reference]. Figure 6 , Figure 6 The diagram illustrates the thickness difference before and after expansion in Example 1.

[0257] The above provides a detailed description of the expandable composition and its preparation method, fiber paper, insulating film, and electrical equipment provided in the embodiments of this application. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the methods and core ideas of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. An expandable composition, characterized in that, The expandable composition includes a resin matrix, a liquid crystal resin, an expandable material, and additives.

2. The expandable composition according to claim 1, characterized in that, The mass percentage of the liquid crystal resin in the expandable composition ranges from 5% to 15%. Preferably, the mass percentage of the liquid crystal resin in the expandable composition ranges from 8% to 13%.

3. The expandable composition according to claim 1, characterized in that, The liquid crystal resin includes at least: Resin carrier; A liquid crystal cell is used to improve the thermal conductivity of the liquid crystal resin, and the liquid crystal cell is embedded in the resin carrier.

4. The expandable composition according to claim 3, characterized in that, The liquid crystal unit includes at least one of the following: azo double bond-bridged diphenyl, carbon-nitrogen double bond-bridged diphenyl, carbon-carbon double bond-bridged diphenyl, biphenyl, bipyridyl, diphenylcyclohexyl, and diphenyl ester.

5. The expandable composition according to claim 3, characterized in that, The resin carrier includes at least one of epoxy resin, acrylate, polyester, polystyrene, and polyimide.

6. The expandable composition according to any one of claims 3 to 5, characterized in that, The number-average molecular weight of the liquid crystal resin ranges from 300 to 8000.

7. The expandable composition according to claim 1, characterized in that, The resin matrix includes an aqueous resin; The waterborne resin includes at least one of waterborne epoxy resin, acrylate resin, and waterborne polyurethane resin.

8. The expandable composition according to claim 1, characterized in that, The expandable material includes at least one of polymeric shape memory material, expandable graphite, expandable physical microspheres, and expandable microcapsules.

9. The expandable composition according to claim 1 or 8, characterized in that, The mass percentage of the expandable material in the expandable composition ranges from 5% to 15%.

10. The expandable composition according to claim 1, characterized in that, The additives include at least one of curing agents, accelerators, coupling agents, defoamers, and stabilizers.

11. The expandable composition according to claim 10, characterized in that, The curing agent includes at least one of amine curing agents, phenolic curing agents, and acid anhydride curing agents; and / or The accelerator includes at least one of amine accelerators, organophosphorus accelerators, ionic accelerators, and imidazole accelerators; and / or The coupling agent includes at least one of silane coupling agents, titanate coupling agents, aluminate coupling agents, phosphate coupling agents, and borate coupling agents; and / or The defoamer includes at least one of silicone oil, fatty alcohol, and liquid paraffin; and / or The stabilizer includes at least one of phosphorus-based heat stabilizers, organotin stabilizers, and metal soap stabilizers.

12. The expandable composition according to any one of claims 1 to 11, characterized in that, The expandable composition comprises the following components in parts by weight:

13. The expandable composition according to claim 1, characterized in that, The expandable composition further includes an epoxy emulsion; The epoxy emulsion includes ester-modified epoxy emulsions.

14. The expandable composition according to claim 13, characterized in that, The ester-modified epoxy emulsion includes at least one of acrylate-modified epoxy emulsion, polyester-modified epoxy emulsion, and fatty acid ester-modified epoxy emulsion.

15. The expandable composition according to claim 13, characterized in that, The mass ratio of the liquid crystal resin to the ester-modified epoxy emulsion ranges from 0.25 to 0.

5.

16. The expandable composition according to claim 13, characterized in that, The expandable composition comprises the following components in parts by weight:

17. The expandable composition according to any one of claims 1 to 16, characterized in that, The in-plane thermal conductivity of the expandable composition ranges from 0.18 W / (m·K) to 0.58 W / (m·K); and / or The expansion thickness difference of the expandable composition ranges from 37 mm to 65 mm.

18. A method for preparing an expandable composition, characterized in that, The method for preparing the expandable composition according to any one of claims 1 to 17 comprises the following steps: The expandable composition is prepared by uniformly dispersing the resin matrix, liquid crystal resin, expandable material and additives, followed by vacuum degassing.

19. The method for preparing the expandable composition according to claim 18, characterized in that, The step of uniformly dispersing the resin matrix, liquid crystal resin, expandable material, and additives includes: The resin matrix, liquid crystal resin, epoxy emulsion, expandable material and additives are uniformly dispersed.

20. A type of fiber paper, characterized in that, The fiber paper comprises fibers and the expandable composition as described in any one of claims 1 to 17.

21. The fiber paper according to claim 20, characterized in that, The fiber includes at least one of aramid fiber, polyamide fiber, aramid fiber, and polyester fiber.

22. An insulating film, characterized in that, The insulating film comprises the fiber paper as described in claim 20 or 21.

23. An electrical appliance, characterized in that, The electrical equipment includes the insulating film as described in claim 22.

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