A polyimide aerogel / phase change material temperature control composite material, its preparation method and application

Abstract

The present invention discloses a polyimide aerogel / phase change material temperature control composite material, its preparation method and application, which relates to the technical field of temperature control composite materials, including a polyimide aerogel carrier and a load carried on the polyimide aerogel carrier, where the load includes fatty alcohol and conductive particles; the conductive particles include carbon black with a particle size of 30 nm and nickel powder with a particle size of 3 μm; the mass ratio of nickel powder to carbon black is 1:0.6 - 1.8. Thus, the polyimide aerogel serves as the support matrix of the PTC composite material, meeting the requirements for applications in harsh environments such as low temperatures; under the action of capillary force, surface tension and hydrogen bonds, the polyimide aerogel with a high surface area can effectively inhibit the collapse and leakage problems caused by the phase change of the phase change material during the heating process of PTC; after the fatty alcohol melts and destroys the conductive network, the polyimide aerogel can inhibit the flow in the molten state and prevent the reformation of the conductive network and the generation of the NTC phenomenon.

Description

Technical Field

[0001] The present invention relates to the technical field of temperature-controlled composite materials, and particularly to a polyimide aerogel / phase change material temperature-controlled composite material, a preparation method thereof, and an application thereof. Background Art

[0002] In recent years, with the rapid development of fields such as aerospace, automotive transportation, and household appliances, various large-scale integrated circuits are widely used in various precision electronic devices, and miniaturization and high integration have become the development direction of various electronic components. However, the thermal expansion and thermal contraction coefficients of different device materials vary greatly. When the temperature difference between the device and the external environment is too large, large thermal stress will be generated, reducing the working performance and reliability of the device, thereby affecting the working efficiency and service life of the device. In order to prevent the components of electronic devices from failing in a high-temperature or low-temperature environment for a long time, general precision electronic devices are required to work in the range of -15 to 50 °C. The temperature control problem has gradually become the main problem restricting the development of electronic components.

[0003] PTC (Positive Temperature Coefficient) materials have broad prospects in temperature control systems in fields such as aerospace, automotive transportation, and household appliances due to their characteristics of realizing adaptive temperature control without the need to rely on a control circuit. Currently, the Curie temperature points of the developed polymer-based PTC materials are generally relatively high (50 - 300 °C), which are difficult to meet the temperature control requirements of electronic components in the normal temperature range, and problems such as a decrease in stability performance are likely to occur during the long-term use of the materials. At present, some researchers have prepared a series of polymer-based PTC materials with low Curie temperatures by directly and simply blending eutectic skeleton support materials with low Curie point phase change materials such as paraffin and organic acid crystals. However, during the heating process of these materials, there are problems such as a large change in the expansion volume of the eutectic skeleton support material, and at the same time, there will be a phenomenon that the heated soft skeleton support material is insufficient to support the phase change material undergoing solid-liquid phase change, and it is prone to problems such as collapse and leakage. Summary of the Invention

[0004] The present invention provides a polyimide aerogel / phase change material temperature-controlled composite material, a preparation method thereof, and an application thereof, to overcome the problems that the skeleton support material of the existing PTC material has a large change in expansion volume and is insufficient to support the solid-liquid phase change during the heating process, and is prone to collapse and leakage, and the existing Joule heating materials need to rely on a control circuit to complete temperature control in applications.

[0005] To achieve the above object, the technical solution of the embodiment of the present invention is as follows:

[0006] The first aspect of the present invention provides a polyimide aerogel / phase change material temperature-controlled composite material, comprising:

[0007] A polyimide aerogel carrier, and a loading carried on the polyimide aerogel carrier, the loading including fatty alcohols and conductive particles;

[0008] The conductive particles include carbon black with a particle size of 30 nm and nickel powder with a particle size of 3 μm;

[0009] The mass ratio of the nickel powder to the carbon black is 1: 0.6 to 1.8.

[0010] Preferably in combination with the first aspect, the polyimide aerogel carrier is prepared by polymerizing aromatic diamine and aromatic dianhydride, freeze-drying and thermal imidization.

[0011] Preferably in combination with the first aspect, the aromatic diamine is one or more of p-phenylenediamine, 3,5-diaminobenzoic acid, 2-(3-aminophenyl)-5-aminobenzimidazole, 4,4'-diaminodiphenyl ether, 2-(4-aminophenyl)-5-aminobenzimidazole;

[0012] And / or, the aromatic dianhydride is one or more of pyromellitic dianhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 4,4'-biphenylether dianhydride, 4,4'-diaminodiphenyl sulfone.

[0013] Preferably in combination with the first aspect, the fatty alcohols are one or more of dodecanol, tridecanol, tetradecanol, pentadecanol.

[0014] The second aspect of the present invention provides a preparation method of the polyimide aerogel / phase change material temperature control composite material described in the first aspect, including:

[0015] Dissolve the aromatic diamine in a polar solvent, add the aromatic dianhydride, carry out heating polymerization and purification, and collect the polyamic acid powder;

[0016] Mix the polyamic acid powder, tertiary amine and water evenly to obtain an aqueous polyamic acid solution, and then carry out freeze-drying and thermal imidization to obtain the polyimide aerogel;

[0017] Heat and melt the fatty alcohol and the conductive particles to obtain a mixture, and immerse the polyimide aerogel in the mixture, and carry out adsorption under a vacuum environment and ultrasonic waves to collect the polyimide aerogel / phase change material temperature control composite material.

[0018] Preferably in combination with the second aspect, the molar ratio of the aromatic diamine to the aromatic dianhydride is 1:1;

[0019] And / or, the mass ratio of the mixture to the polyimide aerogel is 60 to 30:1.

[0020] Preferably in combination with the second aspect, the polar solvent is dimethylacetamide, and the tertiary amine is triethylamine;

[0021] and / or, the solid content of the polyamic acid aqueous solution is 1.2 wt%.

[0022] Preferably in combination with the second aspect, when dissolving the aromatic diamine in the polar solvent, the dissolution time is 20 to 50 min; when performing heat polymerization, the polymerization time is 5 to 15 h;

[0023] and / or, when performing freeze-drying, the freeze-drying time is 48 to 96 h;

[0024] and / or, the thermal imidization includes: first drying at 80 °C, 100 °C, and 120 °C for 1 h in sequence, and then imidizing at 200 °C, 300 °C, and 400 °C for 2 h in sequence to obtain the polyimide aerogel.

[0025] Preferably in combination with the second aspect, the heating and melting time is 1 to 2 h; the temperature of the vacuum environment is 90 °C; the ultrasonic time is 1 to 2 h;

[0026] and / or, when performing vacuum adsorption, the adsorption time is 12 to 24 h.

[0027] The third aspect of the present invention provides an application of the single polyimide aerogel / phase change material temperature control composite material described in the first aspect or the polyimide aerogel / phase change material temperature control composite material prepared by the method described in the second aspect in the preparation of low-temperature thermal management materials for precision electronic components.

[0028] Compared with the prior art, the advantages or beneficial effects of the embodiments of the present invention at least include:

[0029] The polyimide aerogel / phase change material temperature control composite material provided by the present invention uses polyimide aerogel as a carrier, uses fatty alcohol as a phase change material and is loaded in the porous structure of the polyimide aerogel, and the fatty alcohol contains uniformly distributed carbon black and nickel powder; on the one hand, the polyimide aerogel serves as a support matrix for the PTC composite material, meeting the requirements for applications in harsh environments such as low temperatures; on the other hand, under the action of capillary force, surface tension, and hydrogen bonds, the polyimide aerogel with a high surface area can effectively inhibit the collapse and leakage problems caused by the phase change of the phase change material during heating; on the third hand, after the fatty alcohol melts and destroys the conductive network, it can inhibit the flow in the molten state and prevent the reformation of the conductive network and the generation of the NTC phenomenon; on the fourth hand, it simultaneously has a low low-temperature resistivity, stable performance, and high repeatability given by the composite conductive particles with different particle sizes.

[0030] The preparation method provided by the present invention polymerizes aromatic diamine and aromatic dianhydride under the condition of being dissolved in a polar solvent, and after purification treatment, a polyamic acid powder is obtained; then, the polyamic acid powder and a tertiary amine are mixed in water to obtain a polyamic acid solution, followed by freeze-drying and thermal imidization to obtain a polyimide aerogel. Then, fatty alcohol and conductive particles are heated and melted to obtain a mixture, and the polyimide aerogel is impregnated in the mixture, and adsorption is carried out under vacuum and ultrasonic waves so that the mixture can be fully adsorbed into the three-dimensional porous structure of the polyimide aerogel, and the polyimide aerogel / phase change material temperature control composite material is collected. On the one hand, the polyimide aerogel serves as a support matrix for the PTC composite material, meeting the requirements for application in harsh environments such as low temperature. On the other hand, under the action of capillary force, surface tension and hydrogen bonds, the polyimide aerogel with a high surface area can effectively inhibit the collapse and leakage problems caused by the phase change of the phase change material during the heating process of PTC. Thirdly, after the fatty alcohol melts and destroys the conductive network, it can inhibit the flow in the molten state, preventing the reformation of the conductive network and the occurrence of the NTC phenomenon. Fourthly, it simultaneously has a low low-temperature resistivity, stable performance and high repeatability given by the compounding of conductive particles with different particle sizes. Fifthly, compared with the traditional single vacuum negative pressure adsorption, ultrasonic adsorption can prevent the aggregation of high-viscosity mixture particles from blocking the pores of the aerogel and affecting the adsorption efficiency. The mechanical vibration of ultrasonic waves can effectively disperse the particles, and the acoustic cavitation effect and tunneling effect can increase the adsorption effect, making the overall structure tighter.

[0031] The polyimide aerogel / phase change material temperature control composite material provided by the present invention, on the one hand, has excellent temperature control performance under vacuum and low temperature conditions and is expected to be used as a low-temperature thermal management material for precision electronic components; on the other hand, its preparation method is simple, raw materials are easy to obtain, and it is easy to carry out large-scale industrial production.

[0032] In addition, on the one hand, most of the existing polymer-based PTC temperature control materials with low Curie temperature are prepared by blending low-Curie temperature phase change materials with polymer-based skeleton support materials, and the encapsulation strategy combining porous materials has not been considered. On the other hand, different from the temperature control materials of porous materials adsorbing phase change core materials, which complete passive temperature regulation through the absorption or release of latent heat during the phase change process of the phase change core materials, the polyimide aerogel / phase change material temperature control composite material of the present invention realizes active self-controlled temperature regulation through adaptive Joule heating. Description of the Drawings

[0033] Figure 1 It is a micrograph of the polyimide aerogel / phase change material temperature control composite material prepared in Example 5;

[0034] Figure 2 It is a thermal analysis spectrum of the polyimide aerogel / phase change material temperature control composite material prepared in Example 1;

[0035] Figure 3 Temperature-resistivity graph of the polyimide aerogel / phase change material temperature control composite prepared in Example 5;

[0036] Figure 4 Temperature-resistivity cycle graph of the polyimide aerogel / phase change material temperature control composite prepared in Example 5;

[0037] Figure 5 Temperature control graph of the polyimide aerogel / phase change material temperature control composite prepared in Example 5 under vacuum environment. Detailed implementation manners

[0038] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings. The described embodiments should not be regarded as limitations on the present invention. All other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

[0039] In the following description, reference is made to "some embodiments", which describe subsets of all possible embodiments. However, it can be understood that "some embodiments" can be the same subset or different subsets of all possible embodiments and can be combined with each other without conflict. Unless otherwise defined, all technical and scientific terms used in the embodiments of the present invention have the same meaning as commonly understood by those skilled in the technical field to which the embodiments of the present invention belong. The terms used in the embodiments of the present invention are only for the purpose of describing the embodiments of the present invention and are not intended to limit the present invention.

[0040] In the following description of this embodiment, terms such as "include", "comprise", "have" and "contain" are all open-ended terms, that is, they are intended to include but not limited to.

[0041] It should be noted that all raw materials / reagents in the embodiments of the present invention can be purchased on the market or prepared by conventional methods well-known to those skilled in the art; the term " / or" in the embodiments of the present invention is only used to describe the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B represents three situations of A alone, B alone, and A and B existing simultaneously, where A and B can be singular or plural, and the character " / " generally represents an "or" relationship between the associated objects before and after.

[0042] In the following description of this embodiment, the term "at least one" means one or more, and "a plurality" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single items or plural items. For example, "at least one of a, b, or c", or "at least one of a, b, and c" can all represent: a, b, c, a - b (i.e., a and b), a - c, b - c, or a - b - c, where a, b, and c can be single or multiple respectively.

[0043] Those skilled in the art should understand that in the following description of the embodiments of the present invention, the sequence numbers do not imply the order of execution, and some or all of the steps can be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation to the implementation process of the embodiments of the present invention.

[0044] The terms used in the embodiments of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The singular forms "a" and "the" used in the embodiments of the present invention and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0045] Those skilled in the art should understand that the numerical range in the embodiments of the present invention should be understood as specifically disclosing each intermediate value between the upper and lower limits of the range. Each intermediate value between any stated value and the stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded from the range.

[0046] Unless otherwise specified, the technical / scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention pertains. Although the present invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the embodiments or test examples of the present invention. All documents mentioned in this specification are generally incorporated by reference to disclose and describe the methods and / or materials related to the documents. In case of conflict with any incorporated document, the content of this specification of the present invention shall prevail.

[0047] It should be noted that all raw materials and / or reagents in the embodiments of the present invention are purchased on the market or prepared by conventional methods well-known to those skilled in the art.

[0048] In a first aspect, an embodiment of the present invention provides a polyimide aerogel / phase change material temperature control composite material, comprising:

[0049] A polyimide aerogel carrier, and a load carried on the polyimide aerogel carrier, the load including fatty alcohol and conductive particles;

[0050] The conductive particles include carbon black with a particle size of 30 nm and nickel powder with a particle size of 3 μm;

[0051] The mass ratio of the nickel powder to the carbon black is 1:0.6 - 1.8.

[0052] It should be noted that the fatty alcohol contains uniformly distributed conductive particles inside.

[0053] The polyimide aerogel / phase change material temperature control composite material provided by the present invention uses polyimide aerogel as a carrier, fatty alcohol as a phase change material and is loaded in the porous structure of the polyimide aerogel, and the fatty alcohol contains uniformly distributed carbon black and nickel powder inside; on the one hand, the polyimide aerogel, as the support matrix of the PTC composite material, can meet the requirements for application in harsh environments such as low temperature; on the other hand, under the action of capillary force, surface tension and hydrogen bond, the polyimide aerogel with a high surface area can effectively inhibit the collapse and leakage problems caused by the phase change of the phase change material during the heating process of the PTC; on the third hand, after the fatty alcohol melts and destroys the conductive network, it can inhibit the flow in the molten state and prevent the re - formation of the conductive network and the generation of the NTC phenomenon; on the fourth hand, it also has a low low - temperature resistivity, stable performance and high repeatability given by the compound conductive particles with different particle sizes; on the fifth hand, compared with the traditional single vacuum negative pressure adsorption, ultrasonic adsorption can prevent the aggregation of high - viscosity mixture particles from blocking the pores of the aerogel and affecting the adsorption efficiency. The mechanical vibration of ultrasonic waves can effectively disperse the particles, and the acoustic cavitation effect and tunneling effect can increase the adsorption effect, and the overall structure is tighter.

[0054] In practical applications, due to its excellent comprehensive properties of mechanical properties, high temperature resistance, extreme low temperature resistance, corrosion resistance and high porosity, polyimide aerogel has become one of the most concerned materials in the field of special engineering polymers.

[0055] In the present invention, the polyimide aerogel can provide a high - support - strength framework for the PTC material, and the high and low temperature resistance and corrosion resistance can also endow the PTC material with extremely high environmental adaptability. The high porosity can provide more surface area for adsorbing the phase change material and conductive particles, and provide more capillary force, surface tension and hydrogen bond force for the phase change material.

[0056] In a specific embodiment, the polyimide aerogel carrier in the embodiment of the present invention is preferably prepared by polymerizing aromatic diamine and aromatic dianhydride, freeze - drying and thermal imidization.

[0057] In specific embodiments, the aromatic diamine in the embodiments of the present invention is preferably one of p-phenylenediamine, 3,5-diaminobenzoic acid, 2-(3-aminophenyl)-5-aminobenzimidazole, 4,4'-diaminodiphenyl ether, 2-(4-aminophenyl)-5-aminobenzimidazole.

[0058] In specific embodiments, the aromatic dianhydride in the embodiments of the present invention is preferably one of pyromellitic dianhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 4,4'-oxydiphthalic dianhydride, 4,4'-diaminodiphenyl sulfone.

[0059] In specific embodiments, the fatty alcohols in the embodiments of the present invention are preferably one of dodecanol, tridecanol, tetradecanol, pentadecanol; further preferably, tetradecanol. In the present application, the role of the fatty alcohol is a phase change material.

[0060] In a second aspect, the embodiments of the present invention provide a method for preparing a polyimide aerogel / phase change material temperature control composite material, including:

[0061] S10: After dissolving the aromatic diamine in a polar solvent, add the aromatic dianhydride, carry out heating polymerization and purification, and then collect the polyamic acid powder.

[0062] S20: Mix the polyamic acid powder, tertiary amine and water to obtain an aqueous polyamic acid solution, and then carry out freeze-drying and thermal imidization to obtain the polyimide aerogel.

[0063] S30: Heat and melt the fatty alcohol and the conductive particles to obtain a mixture, immerse the polyimide aerogel in the mixture, and carry out adsorption under vacuum and ultrasound to collect the polyimide aerogel / phase change material temperature control composite material.

[0064] In step S1 of the preparation method provided by the present invention, there is no limitation on the specific implementation method of dissolution. For example, dissolution can be carried out under heating conditions or under stirring conditions, as long as the aromatic diamine and the polar solvent are dissolved evenly. There is no particular limitation on the stirring in the present invention. For example, it can be mechanical stirring. Generally, in a better case, in order to make the reaction more complete, continue to stir and react for a period of time after adding.

[0065] In step S1 of the preparation method provided by the present invention, there is no limitation on the specific implementation method of polymerization. For example, polymerization can be carried out under heating conditions or at room temperature as long as the aromatic diamine and the aromatic dianhydride can undergo a polymerization reaction to obtain polyamic acid.

[0066] In step S1 of the preparation method provided by the present invention, there are no restrictions on the specific implementation method of purification. For example, the reaction product of aromatic diamine and aromatic dianhydride can be subjected to multiple washing, centrifugation, drying and other treatments. Among them, solvents such as deionized water, ethanol, methanol, etc. can be used to wash the reaction product; drying treatment can be carried out at high temperature or in a frozen environment.

[0067] Preferably, under the condition of stirring at room temperature, the polar solvent and aromatic diamine are mixed and dissolved, and then aromatic dianhydride is added, and the mixture is stirred and polymerized by heating in a water bath to obtain a solution, so that the reaction is more uniform. Then, the above solution is dropped into deionized water drop by drop, and the precipitated powder is ground, washed and dried to obtain polyamic acid powder.

[0068] In the preparation method provided by the present invention, aromatic diamine and aromatic dianhydride are compounded under the condition of being dissolved in a polar solvent. After the polymerization reaction and purification treatment of aromatic diamine and aromatic dianhydride, polyamic acid powder is obtained; then, the polyamic acid powder and tertiary amine are mixed in water to obtain a polyamic acid solution, which is freeze-dried and thermally imidized to obtain polyimide aerogel. Then, fatty alcohol and conductive particles are heated and melted to obtain a mixture, and the polyimide aerogel is impregnated in the mixture, and adsorption is carried out under vacuum and ultrasonic waves so that the mixture can be fully adsorbed into the three-dimensional porous structure of the polyimide aerogel, and the polyimide aerogel / phase change material temperature control composite material is collected. On the one hand, the polyimide aerogel, as the support matrix of the PTC composite material, can meet the requirements for application in harsh environments such as low temperature; on the other hand, under the action of capillary force, surface tension and hydrogen bond, the polyimide aerogel with a high surface area can effectively inhibit the collapse and leakage problems caused by the phase change of the phase change material during the heating process of PTC; on the third hand, after the fatty alcohol melts and destroys the conductive network, the flow in the molten state can be inhibited, and the reformation of the conductive network and the generation of NTC phenomenon can be prevented; on the fourth hand, it simultaneously has a lower low-temperature resistivity, stable performance and high repetition rate given by the compounding of conductive particles with different particle sizes; on the fifth hand, compared with the traditional single vacuum negative pressure adsorption, ultrasonic adsorption can prevent the aggregation of high-viscosity mixture particles from blocking the pores of the aerogel and affecting the adsorption efficiency. The mechanical vibration of ultrasonic waves can effectively disperse the particles, and the adsorption effect can be increased through the acoustic cavitation effect and tunneling effect, and the overall structure is tighter.

[0069] In a specific embodiment, the molar ratio of the aromatic diamine to the aromatic dianhydride in the embodiment of the present invention is preferably 1:1.

[0070] In a specific embodiment, the mass ratio of the mixture to the polyimide aerogel in the embodiment of the present invention is preferably 60-30:1.

[0071] In a specific embodiment, the polar solvent in the embodiment of the present invention is preferably dimethylacetamide, and the tertiary amine is preferably triethylamine.

[0072] In a specific embodiment, the solid content of the polyamic acid aqueous solution in the embodiment of the present invention is preferably 1.2 wt%.

[0073] In a specific embodiment, when dissolving aromatic diamine in a polar solvent in the embodiment of the present invention, the dissolution time is preferably 20 - 50 min; when performing heat polymerization, the polymerization time is preferably 5 - 15 h.

[0074] In a specific embodiment, when performing freeze-drying in the embodiment of the present invention, the freeze-drying time is preferably 48 - 96 h.

[0075] In a specific embodiment, the thermal imidization in the embodiment of the present invention includes: first drying at 80 °C, 100 °C, and 120 °C for 1 h in sequence, and then imidizing at 200 °C, 300 °C, and 400 °C for 2 h in sequence to obtain a polyimide aerogel.

[0076] In a specific embodiment, the heating and melting time in the embodiment of the present invention is preferably 1 - 2 h; the temperature of the vacuum environment is preferably 90 °C; the ultrasonic time is preferably 1 - 2 h.

[0077] In a specific embodiment, when performing vacuum adsorption in the embodiment of the present invention, the adsorption time is preferably 12 - 24 h.

[0078] In a third aspect, the embodiment of the present invention provides an application of the polyimide aerogel / phase change material temperature control composite material described in the first aspect or the polyimide aerogel / phase change material temperature control composite material prepared by the method described in the second aspect in the preparation of low-temperature thermal management materials for precision electronic components.

[0079] The polyimide aerogel / phase change material temperature control composite material provided by the present invention, on the one hand, has excellent temperature control performance under vacuum and low-temperature conditions and is expected to be used as a low-temperature thermal management material for precision electronic components; on the other hand, its preparation method is simple, the raw materials are easy to obtain, and it is easy to carry out large-scale industrial production.

[0080] Next, the technical method of the present invention will be further elaborated in combination with specific embodiments.

[0081] Examples 1 - 8

[0082] This embodiment provides a preparation method of a polyimide aerogel / phase change material temperature control composite material 1 - 8, and the specific steps are as follows:

[0083] (1) After dissolving aromatic diamine in a polar solvent, add aromatic dianhydride, perform polymerization and purification, and then collect polyamic acid powder:

[0084] 22.43 g (0.1 mol) of 2-(4-aminophenyl)-5-aminobenzimidazole was dissolved in 724 g of N,N-dimethylacetamide solution at room temperature and stirred at 400 rpm for 30 min. Next, 29.42 g (0.1 mol) of 3,3',4,4'-biphenyltetracarboxylic dianhydride was dissolved in this solution, and the mixture was continuously stirred for 10 h under a nitrogen atmosphere at room temperature to obtain a polyamic acid solution. The polyamic acid solution was dropped into deionized water drop by drop, and the precipitated powder was ground, washed three times with deionized water and ethanol, and dried at 80 °C for 12 h to obtain polyamic acid powder.

[0085] (2) After mixing the polyamic acid powder, tertiary amine and water, a polyamic acid aqueous solution was obtained, and then freeze-drying and thermal imidization were carried out to obtain a polyimide aerogel:

[0086] The polyamic acid powder was dissolved in an aqueous solution of triethylamine to obtain a polyamic acid salt solution with a solid content of 1.2%. The prepared polyamic acid salt was injected into a mold, the temperature was set at -50 °C, and the sample was frozen for 30 min. After inverting the mold, the sample was placed in a vacuum freeze-dryer and kept under vacuum at -30 °C and a pressure below 10 Pa for 72 h. Next, the sample was placed in a vacuum oven and imidized at 200 °C, 300 °C and 400 °C for 2 h each to obtain a polyimide aerogel.

[0087] (3) After heating and melting fatty alcohol and conductive particles, a mixture was obtained, and the polyimide aerogel was impregnated in the mixture, and adsorption was carried out under vacuum and ultrasound to collect a polyimide aerogel / phase change material temperature control composite material:

[0088] 20 g of fatty alcohol was heated and melted at 70 °C, 2.4 - 3.6 g of carbon black and 2.0 - 4.0 g of nickel were slowly added, and the mixture was mechanically stirred at 300 rpm for 1 h to obtain a mixture. Subsequently, the polyimide aerogel was impregnated in the molten mixture, adsorbed under a vacuum atmosphere in a 90 °C vacuum oven for 12 h, and adsorbed in an ultrasonic bath at 70 °C for 2 h. The mixture was fully adsorbed into the three-dimensional pores of the aerogel. After cooling to room temperature, a polyimide aerogel / phase change material temperature control composite material was obtained.

[0089] The polyimide aerogel / phase change material temperature control composite materials of Examples 1 - 8 were prepared according to the same method as above. As shown in Table 1, Table 1 shows the component conditions, low-temperature resistivity, Curie temperature, PTC strength (P = Lg(ρ max / ρ min ), ρ max is the maximum resistivity of the material, ρ minA comparison table of the minimum resistivity of the material and whether there is collapse leakage (at 80 °C, the PTC is in good condition, √ if there is no collapse leakage; × if there is collapse leakage).

[0090] Table 1

[0091]

[0092]

[0093] Comparative Examples 1-3

[0094] Comparative Examples 1-3 provide a method for preparing a single conductive particle carbon black-based polyimide aerogel / tetradecanol temperature control composite material, and the specific steps are as follows:

[0095] (1) After dissolving aromatic diamine in a polar solvent, add aromatic dianhydride, carry out polymerization and purification, and collect polyamic acid powder:

[0096] Dissolve 22.43 g (0.1 mol) of 2-(4-aminophenyl)-5-aminobenzimidazole in 724 g of N,N-dimethylacetamide solution at room temperature and stir at 400 rpm for 30 min. Next, dissolve 29.42 g (0.1 mol) of 3,3',4,4'-biphenyltetracarboxylic dianhydride in this solution, and continuously stir for 10 h under a nitrogen atmosphere and at room temperature to obtain a polyamic acid solution. Dropwise add the polyamic acid solution into deionized water, grind the precipitated powder, wash it three times in deionized water and ethanol, and dry it at 80 °C for 12 h to obtain polyamic acid powder.

[0097] (2) After mixing polyamic acid powder, tertiary amine and water, obtain an aqueous polyamic acid solution, and then carry out freeze-drying and thermal imidization to obtain polyimide aerogel:

[0098] Dissolve the polyamic acid powder in an aqueous triethylamine solution to obtain a polyamic acid salt solution with a solid content of 1.2%. Inject the prepared polyamic acid salt into a mold, set the temperature to -50 °C and freeze the sample for 30 min. After inverting the mold, place the sample in a vacuum freeze-dryer and keep it under vacuum at -30 °C and a pressure below 10 Pa for 72 h. Next, place the sample in a vacuum oven and carry out imidization at 200 °C, 300 °C and 400 °C for 2 h each to obtain polyimide aerogel.

[0099] (3) Preparation of a single conductive particle carbon black-based polyimide aerogel / phase change material temperature control composite material:

[0100] 20 g of myristyl alcohol was heated and melted at 70 °C, 2.4 - 3.6 g of carbon black was slowly added, and mechanical stirring was carried out at 300 rpm for 1 h to obtain a mixed material. Subsequently, the aerogel was impregnated in the molten mixed material, adsorbed in a vacuum atmosphere in a vacuum oven at 90 °C for 12 h, and adsorbed by ultrasonic wave at 70 °C for 2 h. The mixed material was fully adsorbed into the three-dimensional pores of the aerogel, and a single conductive particle carbon black-based polyimide aerogel / myristyl alcohol temperature-controlled composite material was obtained after it was cooled to room temperature.

[0101] Table 2 is a comparison table of the component conditions, low-temperature resistivity, Curie temperature, PTC strength, and whether there is a collapse and leakage condition of the single conductive particle carbon black-based polyimide aerogel / myristyl alcohol temperature-controlled composite materials in Comparative Examples 1 - 3.

[0102] Table 2

[0103]

[0104] Comparative Examples 4 - 6

[0105] Comparative Examples 4 - 6 provide a preparation method of a single conductive particle nickel powder-based polyimide aerogel / myristyl alcohol temperature-controlled composite material. The specific steps are as follows:

[0106] (1) After dissolving aromatic diamine in a polar solvent, aromatic dianhydride was added, and after polymerization and purification, polyamic acid powder was collected:

[0107] 22.43 g (0.1 mol) of 2-(4-aminophenyl)-5-aminobenzimidazole was dissolved in 724 g of N,N-dimethylacetamide solution at room temperature, and stirred at 400 rpm for 30 min. Next, 29.42 g (0.1 mol) of 3,3',4,4'-biphenyltetracarboxylic dianhydride was dissolved in this solution, and continuously stirred for 10 h under a nitrogen atmosphere and at room temperature to obtain a polyamic acid solution. The polyamic acid solution was dropped into deionized water drop by drop, the precipitated powder was ground, washed three times in deionized water and ethanol, and dried at 80 °C for 12 h to obtain polyamic acid powder.

[0108] (2) After mixing polyamic acid powder, tertiary amine and water evenly, a polyamic acid aqueous solution was obtained, and then freeze-dried and thermally imidized to obtain a polyimide aerogel:

[0109] The polyamic acid powder is dissolved in an aqueous triethylamine solution to obtain a polyamic acid salt solution with a solid content of 1.2%. The prepared polyamic acid salt is injected into a mold, the temperature is set at -50 °C, and the sample is frozen for 30 min. After inverting the mold, the sample is placed in a vacuum freeze dryer and kept under vacuum at -30 °C and a pressure below 10 Pa for 72 h. Next, the sample is placed in a vacuum oven and imidized at 200 °C, 300 °C, and 400 °C for 2 h each to obtain a polyimide aerogel.

[0110] (3) Preparation of a polyimide aerogel / tetradecanol temperature-controlled composite material with a single conductive particle nickel powder system:

[0111] 20 g of tetradecanol is heated and melted at 70 °C, 5 - 20 g of nickel powder is slowly added, and the mixture is mechanically stirred at 300 rpm for 1 h to obtain a mixed material. Subsequently, the aerogel is impregnated in the molten mixed material and adsorbed in a vacuum atmosphere in a 90 °C vacuum oven for 12 h and adsorbed by ultrasonic treatment at 70 °C for 2 h. The mixed material is fully adsorbed into the three-dimensional pores of the aerogel, and the polyimide aerogel / tetradecanol temperature-controlled composite material with a single conductive particle nickel powder system is obtained after it cools to room temperature.

[0112] Table 3 is a comparison table of the component conditions, low-temperature resistivity, Curie temperature, PTC strength, and whether there is collapse and leakage of the polyimide aerogel / tetradecanol temperature-controlled composite material with a single conductive particle nickel powder system for Comparative Examples 4 - 6.

[0113] Table 3

[0114]

[0115] Comparative Examples 7 - 9

[0116] Comparative Examples 7 - 9 provide a preparation method for a polyimide aerogel / paraffin temperature-controlled composite material with a single conductive particle carbon black system. The specific steps are as follows:

[0117] (1) After dissolving aromatic diamine in a polar solvent, aromatic dianhydride is added, and after polymerization and purification, polyamic acid powder is collected:

[0118] 22.43 g (0.1 mol) of 2-(4-aminophenyl)-5-aminobenzimidazole is dissolved in 724 g of an N,N-dimethylacetamide solution at room temperature and stirred at 400 rpm for 30 min. Next, 29.42 g (0.1 mol) of 3,3',4,4'-biphenyltetracarboxylic dianhydride is dissolved in this solution, and the mixture is continuously stirred for 10 h under a nitrogen atmosphere and at room temperature to obtain a polyamic acid solution. The polyamic acid solution is slowly dropped into deionized water, the precipitated powder is ground, washed three times in deionized water and ethanol, and dried at 80 °C for 12 h to obtain polyamic acid powder.

[0119] (2) Mix the polyamic acid powder, tertiary amine, and water evenly to obtain an aqueous polyamic acid solution, and then perform freeze-drying and thermal imidization to obtain a polyimide aerogel:

[0120] Dissolve the polyamic acid powder in an aqueous triethylamine solution to obtain a polyamic acid salt solution with a solid content of 1.2%. Inject the prepared polyamic acid salt into a mold, set the temperature to -50°C, and freeze the sample for 30 minutes. After inverting the mold, place the sample in a vacuum freeze-dryer and keep it under vacuum at -30°C and a pressure below 10 Pa for 72 hours. Next, place the sample in a vacuum oven and perform imidization at 200°C, 300°C, and 400°C for 2 hours each to obtain a polyimide aerogel.

[0121] (3) Preparation of a polyimide aerogel / paraffin temperature-controlled composite with a single conductive particle carbon black system:

[0122] Heat 20 g of paraffin to melt at 70°C, slowly add 2.4 - 3.6 g of carbon black, and mechanically stir at 300 rpm for 1 hour to obtain a mixture. Subsequently, immerse the aerogel in the molten mixture, adsorb it in a vacuum atmosphere in a 90°C vacuum oven for 12 hours, and perform adsorption in an ultrasonic bath at 70°C for 2 hours. The mixture is fully adsorbed into the three-dimensional pores of the aerogel, and when it cools to room temperature, a polyimide aerogel / paraffin temperature-controlled composite with a single conductive particle carbon black system is obtained.

[0123] Table 4 is a comparison table of the component conditions, low-temperature resistivity, Curie temperature, PTC strength, and whether there is collapse and leakage of the polyimide aerogel / paraffin temperature-controlled composite with a single conductive particle carbon black system for Comparative Examples 7 - 9.

[0124] Table 4

[0125]

[0126] Comparative Examples 10 - 12

[0127] Comparative Examples 10 - 12 provide a composite material not encapsulated with polyimide aerogel. The specific steps are as follows:

[0128] Heat 20 g of fatty alcohol to melt at 70°C, slowly add 2.4 - 3.6 g of carbon black, and mechanically stir at 300 rpm for 1 hour to obtain a mixture. Pour the mixture into a mold, and when it cools to room temperature, a composite material not encapsulated with polyimide aerogel is obtained.

[0129] Table 5 is a comparison table of the component conditions, low-temperature resistivity, Curie temperature, PTC strength, and whether there is collapse and leakage of a composite material not encapsulated with polyimide aerogel provided by Comparative Examples 10 - 12.

[0130] Table 5

[0131]

[0132] As can be seen from Table 1 above, in Examples 1-5, when the fatty alcohol is tetradecanol, when the comprehensive properties of the polyimide aerogel / phase change material temperature control composite material, such as the low-temperature resistivity, Curie temperature, and PTC strength, are optimal, the optimal mass ratio of carbon black to nickel powder is 1:1.8. The mass fraction of carbon black in the fatty alcohol is 12%, 15%, and 18%, and the mass fraction of nickel powder in the fatty alcohol is 10% and 20%. Among them, the carbon black with a mass fraction of 18% of the fatty alcohol compounded with the nickel powder with a mass fraction of 20% of the fatty alcohol has too high a system viscosity, and it is difficult for the aerogel to adsorb sufficiently. At the optimal mass ratio of 1:1.8, the optimal low-temperature resistivity of the polyimide aerogel / phase change material temperature control composite material is 0.77 Ω·m, the optimal Curie temperature is 34 °C, and the optimal PTC strength is 3.41. When the mass ratio of carbon black to nickel powder is 1:1.8, the comprehensive properties of the polyimide aerogel / phase change material temperature control composite materials with dodecanol, tridecanol, and pentadecanol as fatty alcohols are verified. It can be seen that when the fatty alcohol is tetradecanol, the effect is the best, because the compatibility between the conductive filler and tetradecanol is the best, and the interfacial interaction is the strongest.

[0133] As can be seen from Table 2, Comparative Examples 1-3 verified the component conditions, low-temperature resistivity, Curie temperature, and PTC strength of the polyimide aerogel / tetradecanol temperature control composite material with a single conductive particle carbon black system. When the carbon black is 3.6 g, the comprehensive effect is the best, the optimal low-temperature resistivity is 1.42 Ω·m, the optimal Curie temperature is 34 °C, and the optimal PTC strength is 3.07. Comparing with the low-temperature resistivity of 0.77 Ω·m and the PTC strength of 3.41 at the optimal mass ratio of 1:1.8 of carbon black and nickel powder in Example 5, its low-temperature resistivity is higher and the PTC strength is lower. This shows that the introduction of composite conductive particles with different particle sizes increases new conductive network connection points. At the same time, during the phase change process, the conductive network is more easily damaged. The composite material has lower low-temperature resistivity and higher PTC strength.

[0134] As can be seen from Table 3, Comparative Examples 4-6 verified the component conditions, low-temperature resistivity, Curie temperature, and PTC strength of the polyimide aerogel / tetradecanol temperature-controlled composite material with a single conductive particle nickel powder system. When the nickel powder was 10 g, the comprehensive effect was optimal, the optimal low-temperature resistivity was 3.90 Ω·m, the optimal Curie temperature was 34 °C, and the optimal PTC strength was 2.32. Compared with the low-temperature resistivity of 0.77 Ω·m and the PTC strength of 3.41 of the optimal mass ratio of carbon black to nickel powder of 1:1.8 in Example 5, its low-temperature resistivity was high and the PTC strength was low. This again verified that the introduction of compound conductive particles with different particle sizes increased new conductive network connection points, and during the phase change process, the conductive network was more easily damaged. The composite material had lower low-temperature resistivity and higher PTC strength.

[0135] As can be seen from Table 4, Comparative Examples 7-9 verified the system with paraffin as the comparative phase change material. When the carbon black was 3.6 g, the comprehensive effect was optimal, the optimal low-temperature resistivity was 3.27 Ω·m, the optimal Curie temperature was 47 °C, and the optimal PTC strength was 1.97. Compared with the fatty alcohol system, the effect was worse. The composite material with the fatty alcohol system as the phase change material had lower low-temperature resistivity and higher PTC strength. This was because the conductive filler had better wettability in tetradecanol and was more uniformly dispersed than in paraffin, so it had more excellent initial conductivity. At the same time, tetradecanol had a higher phase change enthalpy, and the phase change caused greater damage to the crystallization of tetradecanol, and the conductive network was more easily damaged, so the tetradecanol system had a higher PTC strength.

[0136] As can be seen from Table 5, Comparative Examples 10-12 verified that the composite material without polyimide aerogel encapsulation showed a collapse phenomenon. Under the capillary force, surface tension, and hydrogen bond action, the polyimide aerogel with a high surface area could effectively inhibit the collapse and leakage problems caused by the softening of the matrix and the phase change of the phase change material during the heating process of PTC.

[0137] As can be seen from Tables 1-4 above, compared with Comparative Examples 1-6, the introduction of compound conductive particles in Examples 1-8 made the composite material have lower low-temperature resistivity and higher PTC strength. Compared with Comparative Examples 7-9, for the system with paraffin as the comparative phase change material, the composite material with the fatty alcohol system as the phase change material had lower low-temperature resistivity and higher PTC strength. Compared with Comparative Examples 10-11, under the capillary force, surface tension, and hydrogen bond action, the polyimide aerogel with a high surface area could effectively inhibit the collapse and leakage problems caused by the softening of the matrix and the phase change of the phase change material during the heating process of PTC.

[0138] To verify the technical effects of this application, the performance of the polyimide aerogel / phase change material temperature-controlled composite material in the examples was analyzed, and the results were as Figures 1-5 shown. Figure 1It is the microscopic morphology diagram of the polyimide aerogel / phase change material temperature control composite material in Example 5. Figure 2 It is the DSC diagram of the polyimide aerogel / phase change material temperature control composite material in Example 1. Figure 3 It is the temperature-resistivity diagram of the polyimide aerogel / phase change material temperature control composite material in Example 5. Figure 4 It is the temperature-resistivity cycle diagram of the polyimide aerogel / phase change material temperature control composite material in Example 5. Figure 5 It is the temperature control diagram of the polyimide aerogel / phase change material temperature control composite material in a vacuum environment in Example 5.

[0139] According to Figure 1 It can be seen that the morphological structure of the prepared polyimide aerogel / phase change material temperature control composite material. The polyimide aerogel exhibits a three-dimensional tubular pore structure, which is caused by the unidirectional freezing method. The fatty alcohol and conductive particles fill the pores of the aerogel, showing the characteristics of complete adsorption. No obvious interface between the aerogel and the phase change material can be observed, indicating good compatibility between the polyimide aerogel with high surface area and the phase change material, which is due to the capillary force, surface tension and hydrogen bond force between them.

[0140] According to Figure 2 It can be seen that when the sample is heated from -20°C to 80°C at a heating rate of 5°C / min, the abscissas of several main characteristic points such as the change trend, starting point and peak temperature point of the two curves are almost equal, which indicates that the phase change temperature and phase change interval of the PTC composite material depend on the phase change material used to prepare the PTC composite material. The Curie temperature of tetradecanol is about 34°C and the melting point is 39.4°C. The Curie temperature of the PTC composite material is about 34°C and the melting point is 38.9°C.

[0141] According to Figure 3 It can be seen that in the programmable constant temperature and humidity test chamber for heating and cooling experiments, during the heating process, when the sample temperature is near the Curie temperature, the resistivity increases sharply to the peak. This characteristic is due to the phase change of the tetradecanol phase change matrix in the PTC composite material absorbing heat and rising to the Curie temperature, which destroys the conductive network of the material. Examples 1-9 have lower low-temperature resistivity, low Curie temperature and high PTC strength. During the cooling process, there is a deviation between the curve and the heating curve. The phase change material has supercooling, and there is a difference between the crystallization temperature and the melting temperature. Before cooling to the crystallization temperature, the phase change material is still in the molten state. When reaching the crystallization temperature, the tetradecanol solidifies and crystallizes, and the conductive network begins to return to the initial resistance value.

[0142] According to Figure 4It can be seen that during 50 heating and cooling cycles, the low-temperature resistivity of the prepared polyimide aerogel / phase change material temperature-controlled composite material is maintained between 1.50 and 1.61 Ω·m, and the PTC strength decreases from 3.53 to 3.25, showing excellent cycle stability. This is attributed to the capillary force, surface tension and hydrogen bond force between the aerogel and tetradecanol. In the molten state, tetradecanol does not flow and its position remains unchanged, showing stability.

[0143] According to Figure 5 It can be seen that the self-made vacuum chamber is placed in the chamber of a programmable constant temperature and humidity test chamber at -20 °C to simulate the working environment of spacecraft electronic components. A 5-mm-thick aluminum block is loaded on the PTC surface for device temperature control testing. In a non-adiabatic environment considering only thermal radiation, in the first few minutes of power-on, the heat generation is greater than the heat dissipation (thermal radiation) at this time, and the temperature of the composite material rises rapidly. After heating for a period of time, the Curie temperature point of tetradecanol is reached. At this time, the internal conductive network is damaged and an open circuit is formed, and heat cannot be generated continuously. The heat generation is equal to the heat dissipation, and a thermal equilibrium state is reached. As the applied voltage increases, the temperature at which the composite material reaches the thermal equilibrium state gradually increases, but it is still below 34 °C, fully demonstrating the application potential of the PTC composite material in the field of temperature control of spacecraft electronic components.

[0144] As described above, only the specific embodiments of the present invention are provided, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, and all should be covered by the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claimed rights.

Claims

1. A polyimide aerogel / phase change material temperature-controlled composite material, characterized in that, Comprising: A polyimide aerogel carrier, and a load carried on the polyimide aerogel carrier, the load comprising fatty alcohol and conductive particles; The conductive particles include carbon black with a particle size of 30 nm and nickel powder with a particle size of 3 μm; The mass ratio of the nickel powder to the carbon black is 1:0.6 - 1.

8.

2. The polyimide aerogel / phase change material temperature control composite material according to claim 1, wherein The polyimide aerogel carrier is prepared by polymerizing aromatic diamine and aromatic dianhydride, followed by freeze-drying and thermal imidization.

3. The polyimide aerogel / phase change material temperature control composite material according to claim 2, wherein The aromatic diamine is one or more of p-phenylenediamine, 3,5-diaminobenzoic acid, 2-(3-aminophenyl)-5-aminobenzimidazole, 4,4'-diaminodiphenyl ether, 2-(4-aminophenyl)-5-aminobenzimidazole; The aromatic dianhydride is one or more of pyromellitic dianhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 4,4'-biphenylether dianhydride, 4,4'-diaminodiphenyl sulfone; 4. The polyimide aerogel / phase change material temperature control composite material according to claim 1, wherein The fatty alcohols are one or more of dodecanol, tridecanol, tetradecanol, pentadecanol.

5. A method for preparing a polyimide aerogel / phase change material temperature control composite material according to any one of claims 1-4, characterized in that, Comprising: Dissolve the aromatic diamine in a polar solvent, add the aromatic dianhydride, carry out polymerization and purification, and then collect the polyamic acid powder; Mix the polyamic acid powder, tertiary amine and water to obtain an aqueous polyamic acid solution, and then carry out freeze-drying and thermal imidization to obtain the polyimide aerogel; Heat and melt the fatty alcohol and conductive particles to obtain a mixture, immerse the polyimide aerogel in the mixture, and carry out adsorption under a vacuum environment and ultrasonic treatment, and collect the polyimide aerogel / phase change material temperature control composite material.

6. The polyimide aerogel / phase change material temperature control composite material according to claim 5, characterized in that, The molar ratio of the aromatic diamine to the aromatic dianhydride is 1:1; The mass ratio of the mixture to the polyimide aerogel is 60 - 30:

1.

7. The preparation method of the polyimide aerogel / phase change material temperature control composite material according to claim 5, characterized in that, The polar solvent is dimethylacetamide, and the tertiary amine is triethylamine; The solid content of the aqueous polyamic acid solution is 1.2 wt%.

8. The preparation method of the polyimide aerogel / phase change material temperature control composite material according to claim 5, characterized in that, When dissolving the aromatic diamine in the polar solvent, the dissolution time is 20 - 50 min; when carrying out heating polymerization, the polymerization time is 5 - 15 h; When carrying out freeze-drying, the freeze-drying time is 48 - 96 h; The thermal imidization includes: first drying at 80 °C, 100 °C, and 120 °C for 1 h each in sequence, and then imidizing at 200 °C, 300 °C, and 400 °C for 2 h each in sequence to obtain the polyimide aerogel.

9. The preparation method of the polyimide aerogel / phase change material temperature control composite material according to claim 5, characterized in that The heating and melting time is 1 - 2 h; the temperature of the vacuum environment is 90 °C; the ultrasonic time is 1 - 2 h; And / or, when carrying out vacuum adsorption, the adsorption time is 12 - 24 h.

10. Use of the polyimide aerogel / phase change material temperature control composite material according to any one of claims 1 - 4 or the polyimide aerogel / phase change material temperature control composite material prepared by the method according to any one of claims 5 - 9 in the preparation of low-temperature thermal management materials for precision electronic components.

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