CN112480404B - Magnetic heat-conducting polyimide composite material and preparation method thereof - Google Patents

Magnetic heat-conducting polyimide composite material and preparation method thereof Download PDF

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CN112480404B
CN112480404B CN202011354869.8A CN202011354869A CN112480404B CN 112480404 B CN112480404 B CN 112480404B CN 202011354869 A CN202011354869 A CN 202011354869A CN 112480404 B CN112480404 B CN 112480404B
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ferroferric oxide
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高纪明
杨阳
杨军
刘杰
王进
江乾
张丽敏
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Zhuzhou Times New Material Technology Co Ltd
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    • C08G73/00—Macromolecular compounds obtained by reactions forming a linkage containing nitrogen with or without oxygen or carbon in the main chain of the macromolecule, not provided for in groups C08G12/00 - C08G71/00
    • C08G73/06—Polycondensates having nitrogen-containing heterocyclic rings in the main chain of the macromolecule
    • C08G73/10—Polyimides; Polyester-imides; Polyamide-imides; Polyamide acids or similar polyimide precursors
    • C08G73/1067—Wholly aromatic polyimides, i.e. having both tetracarboxylic and diamino moieties aromatically bound
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    • C01G49/08—Ferroso-ferric oxide [Fe3O4]
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    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
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Abstract

The invention discloses a magnetic heat-conducting polyimide composite material and a preparation method thereof, wherein ferric salt or ferric salt and salt doped with element M are dissolved in ethylene glycol, then urea and hexadecyl trimethyl ammonium bromide are added, the mixture is stirred and dissolved, the temperature is kept at 200-240 ℃ for 15-30 h, and nano ferroferric oxide or nano doped ferroferric oxide is obtained through cooling treatment; mixing the slurry with a solvent and a dispersant, stirring and dispersing, and then adding a surface modifier for modification to obtain dispersed slurry; the raw material for synthesizing polyamic acid is added to the dispersion slurry to synthesize polyamic acid, which is then imidized. The composite material synthesized by the invention has magnetism, the heat-conducting property is further improved, and the invention has the advantages of simple process, low cost, environmental protection and easy realization of industrial production.

Description

Magnetic heat-conducting polyimide composite material and preparation method thereof
Technical Field
The invention belongs to the field of preparation of functional polymer composite materials, and relates to a magnetic heat-conducting polyimide composite material and a preparation method thereof.
Background
Polyimide (PI) is a polymer having an imide ring structure in the main chain, and has excellent chemical stability, mechanical properties, electrical insulation properties, high thermal stability and glass transition temperature, and thus has been widely used in the high-tech fields of aerospace, rail transit, microelectronics, and the like. With the rapid development of new technologies such as AI and 5G, higher requirements are put on the performance of polyimide. Especially, the popularization and application of the 5G communication technology lead to the continuous increase of the power consumption and the heat productivity of the equipment due to the introduction of high frequency, the continuous improvement of the hardware integration level, the continuous miniaturization of chips and the multiple increase of the number of networking equipment and antennas, and meanwhile, electromagnetic interference between the equipment and the electromagnetic interference inside the equipment are ubiquitous, and the harm of the electromagnetic interference and the electromagnetic radiation to the electronic equipment is increasingly serious, so that the electromagnetic radiation and the heat dissipation of components become the bottleneck problem of the communication terminal equipment in the 5G era.
The maturity of the 5G technology can promote the rapid development of mobile terminal equipment such as unmanned vehicles, intelligent wearing and the like, develop brand new application fields for electromagnetic shielding and heat conducting products, and put forward higher requirements on the comprehensive performance of device materials. However, the existing magnetic polyimide material has a complex preparation process, is difficult to realize industrial production, and does not find a polyimide composite material with both magnetism and heat conductivity.
Disclosure of Invention
The technical problem to be solved by the invention is to overcome the defects and shortcomings in the background art and provide a preparation method of a polyimide composite material with both magnetic property and thermal conductivity.
In order to solve the technical problems, the technical scheme provided by the invention is as follows:
a preparation method of a magnetic heat-conducting polyimide composite material comprises the following steps:
(1) Dissolving ferric salt or ferric salt and salt of a doping element M in ethylene glycol, adding urea and hexadecyl trimethyl ammonium bromide, stirring and dissolving, keeping the temperature at 200-240 ℃ for 15-30 h, and cooling to obtain nano ferroferric oxide or nano-doped ferroferric oxide;
(2) Mixing the ferroferric oxide or doped ferroferric oxide obtained in the step (1) with a solvent and a dispersant, stirring and dispersing, and then adding a surface modifier for modification to obtain dispersed slurry;
(3) And (3) adding a raw material for synthesizing polyamic acid into the dispersed slurry obtained in the step (2), synthesizing polyamic acid, and then carrying out imidization to obtain the ferroferric oxide/polyimide composite material or the doped ferroferric oxide/polyimide composite material.
Further, the doping element M comprises one or more of Co, mn or Ni.
Further, the iron salt is FeCl 3 ·6H 2 Salts of O, M with MCl 2 (ii) a FeCl as a raw material for synthesizing ferroferric oxide 3 ·6H 2 The mass ratio of O, EG, urea, CTAB and the like is (0.8-1.2): (14-20): (3-7): (1-3); feCl in the raw material for synthesizing doped ferroferric oxide 3 ·6H 2 O、MCl 2 EG, urea and CTAB in a mass ratio of (0.5-0.8): (0.3-0.4): (14-20): (3-7): (1-3).
Further, the cooling treatment of the step (1) is rapid cooling in flowing water.
Further, in the step (2), the mixture is mixed with a solvent and a dispersing agent, the rotating speed is controlled to be 500-800r/min, the mixture is stirred and dispersed for 15-30 h, then a surface modifier is added, the rotating speed is increased to be 2000-3000 r/min, and the mixture is stirred for 0.5-1.5 h.
Further, the surface modifier is a titanate coupling agent and/or a silane coupling agent, and the dosage of the surface modifier is 3-10wt% of ferroferric oxide or doped ferroferric oxide.
Further, the dispersing agent comprises one or more of BYK-2055, BYK-161, BYK-160 or BYK-2050, and the amount of the dispersing agent is 3-10wt% of ferroferric oxide or doped ferroferric oxide.
Further, the raw materials for synthesizing the polyamic acid in the step (3) comprise aromatic diamine, aromatic dianhydride and plasticizer, and the reaction temperature is controlled below 10 ℃.
The invention provides a magnetic heat-conducting polyimide composite material which is prepared by the method and comprises polyimide and hollow nano-spherical ferroferric oxide or doped ferroferric oxide dispersed in the polyimide.
Furthermore, the filling amount of the ferroferric oxide or the doped ferroferric oxide is 10-25 wt% of the composite material.
Compared with the prior art, the invention has the following advantages and effects:
(1) The invention adopts a solvothermal method to synthesize ferroferric oxide and multi-element doped ferroferric oxide in one step. The synthesized ferroferric oxide and the multi-element doped ferroferric oxide have high controllable degree of particle morphology, high crystallinity and high purity.
(2) By optimizing the surface modification of the particles, the polymer composite material with the filler uniformly dispersed in the polyimide matrix is synthesized by an in-situ method.
(3) Researches show that the magnetic domain structure of the composite material synthesized by the invention is changed under the action of an external magnetic field, the heat-conducting property is changed accordingly, and the heat-conducting property of the composite material is further improved while the composite material has magnetism.
(4) The polyimide composite material with the heat-conducting property and the electromagnetic shielding property can meet the requirements of heat dissipation and electromagnetic shielding of devices and integrated circuits under high-density and high-speed operation, and effectively improves the information transmission rate and frequency in the technical field of 5G communication.
(5) The in-situ synthesis method, the inorganic filler dispersion method and the surface modification method adopted by the invention are similar to the industrial production process, and the method has the advantages of simple process, low cost, greenness, environmental protection and easy realization of industrial production.
Drawings
In order to more clearly illustrate the embodiments or technical solutions of the present invention, the drawings used in the embodiments or technical solutions in the prior art are briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to these drawings without creative efforts.
FIG. 1 is a graph showing the thermal conductivity of the composite material of examples 1 to 4 of the present invention in the presence or absence of an external magnetic field;
FIG. 2 is the thermal conductivity of the composite material of examples 3 and 5 to 7 of the present invention in the presence or absence of an external magnetic field;
FIG. 3 shows different Fe contents in examples 1-4 of the present invention under the action of no external magnetic field 3 O 4 The magnetic domain structure of the/PI composite material is (a) 10wt%; (b) 15 wt.%；(c)20wt％；(d)25wt％；
FIG. 4 shows different Fe contents under the action of external magnetic field in examples 1-4 of the present invention 3 O 4 The magnetic domain structure of the/PI composite material is (a) 10wt%; (b) 15wt%; (c) 20wt%; (d) 25wt%;
FIG. 5 shows 20wt% of examples 3 and 5 to 7 according to the invention without external magnetic field x Fe 3-x O 4 Magnetic domain structure of/PI composite material (a) Fe 3 O 4 ；(b)CoFe 2 O 4 ；(c)Mn 0.05 Fe 2.95 O 4 ；(d)Ni 0.4 Fe 2.6 O 4 ；
FIG. 6 shows 20wt% of M in examples 3 and 5 to 7 according to the invention by the action of an external magnetic field x Fe 3-x O 4 Magnetic domain structure of/PI composite material (a) Fe 3 O 4 ；(b)CoFe 2 O 4 ；(c)Mn 0.05 Fe 2.95 O 4 ；(d)Ni 0.4 Fe 2.6 O 4 。
FIG. 7 is Fe prepared in example 1 of the present invention 3 O 4 SEM photograph.
Detailed Description
In order to facilitate understanding of the invention, the invention will be described more fully and in detail with reference to the accompanying drawings and preferred embodiments, but the scope of the invention is not limited to the specific embodiments below.
Unless otherwise defined, all terms of art used hereinafter have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of the present invention.
Unless otherwise specifically stated, various raw materials, reagents, instruments, equipment and the like used in the present invention are commercially available or can be prepared by existing methods.
According to the invention, the ferroferric oxide or doped ferroferric oxide magnetic material synthesized by the method is introduced into the polyimide matrix, and the obtained composite material has magnetism and the heat-conducting property is further improved, so that the multifunctional polyimide composite material with both magnetism and heat-conducting property is obtained.
The preparation method of the magnetic filler of one embodiment of the invention comprises the following steps:
(1) Solvothermal method for synthesizing Fe 3 O 4 : dissolving iron salt in EG (ethylene glycol), then adding urea and CTAB (cetyl trimethyl ammonium bromide), stirring and dissolving, and keeping the temperature at 200-240 ℃ for 15-30 h. Then quickly cooling to room temperature and carrying out post-treatment to obtain the product. Solvothermal synthesis of M-doped M x Fe 3-x O 4 In addition, a salt of M is added to the raw material, wherein M is preferably one or more of Co, mn and Ni, but is not limited to the above elements, and Zn, cd, mg, cu and partial rare earth elements can be contained.
The ethylene glycol is used as a solvent in the reaction process, has slight reducibility, and is helpful for promoting the synthesis process of ferroferric oxide. CTAB is used as a surface modifier and a morphology directing agent in the reaction process, and is beneficial to forming the nano hollow sphere by the synthesized ferroferric oxide.
EG. The feeding sequence of urea and CTAB is determined according to the solid-liquid state and the solubility condition of raw materials, firstly, ferric salt and a certain amount of doping element-containing substances are dissolved in EG to form stable solution; the order of addition of urea and CTAB has little effect on the reaction, but urea will generally dissolve first, depending on the solubility of the two.
The heat preservation can be carried out in a blast drying oven, the temperature inside the oven is uniformly distributed, and no obvious temperature gradient exists. The rapid cooling is carried out, for example, the particles are placed in flowing water for cooling, the specific cooling speed is not strictly required, and the rapid cooling is to avoid the appearance, appearance and structure changes of the particles in the cooling process.
FeCl can be used as ferric salt 3 ·6H 2 The salt of O and M can adopt MCl 2 . Preferably, the ferroferric oxide Fe is synthesized by a solvothermal method 3 O 4 Of the starting materials, feCl 3 ·6H 2 The mass ratio of O, EG, urea, CTAB and the like is as follows: (0.8-1.2): (14-20): (3-7): (1-3). Preferably, a solventThermal method for synthesizing doped ferroferric oxide M x Fe 3-x O 4 ，FeCl 3 ·6H 2 O、MCl 2 EG, urea and CTAB in the following mass ratios: (0.5-0.8): (0.3-0.4): (14-20): (3-7): (1-3).
The ferroferric oxide particles with high crystallinity and hollow nano-sphere shapes are obtained by one-step synthesis by adopting a solvothermal method. Synthesizing hollow nano-spherical doped ferroferric oxide nano-particles with different components by multi-element doping. The factors influencing the crystallinity and the nanometer spherical shape of the magnetic filler are mainly as follows: the factors of the dosage ratio of the raw materials, the reaction temperature, the reaction time, the selection of the morphology directing agent and the like lead to the microscopic morphology of the hollow nano sphere, have larger specific surface area, and are easier to disperse in the polyimide polymer matrix under the same state, so that the composite material has a uniform and stable magnetic domain structure.
(2) Magnetic filler dispersion and surface modification: mixing the obtained magnetic filler with a solvent (such as DMF) and a dispersing agent, stirring and dispersing for 15-30 h, and controlling the rotating speed to 500-800r/min. Then adding a surface modifier, raising the rotating speed to 2000-3000 r/min, and stirring for 0.5-1.5 h to obtain the dispersion slurry. The rotation speed is increased to facilitate the combination of the active groups of the surface modifier and the surface groups of the inorganic filler.
Wherein the surface modifier is selected from titanate coupling agent TM-48, TM-38S and silane coupling agent KH550, preferably TM-48. The dosage proportion of the ferroferric oxide and the doped ferroferric oxide is 3-10wt percent. The surface modification can improve the dispersion uniformity of the filler in the polyimide matrix, improve the organic combination degree of the filler and the matrix and improve the heat-conducting property of the composite material. The method has simple process and is easier to realize industrialization.
Wherein the dispersant is selected from BYK-2055, BYK-161, BYK-160 and BYK-2050, preferably BYK-2055. The dosage proportion of the ferroferric oxide and the multi-element doped ferroferric oxide is 3-10wt percent.
The magnetic heat-conducting polyimide composite material comprises Fe 3 O 4 Composite material of/PI and M x Fe 3-x O 4 Composite materials of the type I and II Fe 3 O 4 /M x Fe 3-x O 4 The filling amount is 10-25 wt% of the composite material.
The preparation method of the polyimide composite material of one embodiment of the invention comprises the following steps:
(3) In-situ synthesis of Fe 3 O 4 (M x Fe 3-x O 4 ) PAA resin: adding a solvent (such as DMF), a plasticizer, aromatic diamine and aromatic dianhydride into the dispersed slurry obtained in the step (2) for reaction, wherein the reaction temperature is controlled below 10 ℃.
(4) Imidization: mixing Fe 3 O 4 (M x Fe 3-x O 4 ) Imidization of PAA resin to obtain Fe 3 O 4 the/PI composite material or M x Fe 3- x O 4 a/PI composite material. Vacuum imidization can be adopted, but the atmosphere environment in the imidization process is not limited to a vacuum environment, and other inert gases can be used without oxygen, such as: inert gas environments such as argon and nitrogen are also possible.
The in-situ synthesis process uses ferroferric oxide dispersion liquid as a polyimide precursor synthesis solvent, the ferroferric oxide forms stable dispersion liquid in the polyimide precursor synthesis process, the dispersion liquid is always in a stirring and dispersing state in the reaction process, so that the filler is uniformly dispersed in the matrix, and the composite material is beneficial to having a uniform and stable magnetic domain structure.
Example 1
Fe 3 O 4 The ferroferric oxide filling amount in the/PI composite material is 10wt%.
Step one, synthesizing Fe by solvothermal method 3 O 4 ：3mmol FeCl 3 ·6H 2 O and 48mL EG were dissolved well in a glass beaker, 15mmol urea was added to the solution, stirring was continued until completely dissolved, and finally 6mmol CTAB was added to the above solution, continuing at high speedStir until all solids are dissolved. Transferring the dissolved solution into a 50mL reaction kettle, placing the reaction kettle into a forced air drying oven, preserving the temperature at 220 ℃ for 24 hours, placing the reaction kettle into flowing water, rapidly cooling to room temperature, separating the synthesized black solid, washing with absolute ethyl alcohol, and drying for later use. After multiple times of or amplification experiments, 2.79g of ferroferric oxide is obtained. The microscopic morphology is a hollow sphere nanostructure, and the SEM photograph is shown in FIG. 7.
Step two, magnetic filler dispersion and surface modification: taking a proper amount of ferroferric oxide in the step one, 70g of DMF (N, N-dimethylformamide) and 2.79g of dispersant BYK-2055, mechanically stirring for 24 hours, and dispersing, wherein the rotating speed is controlled to be 500-800r/min. 0.28g of TM-48 is added into the system, and the rotating speed is increased to 2500r/min for 1h.
Step three, in-situ synthesis of Fe 3 O 4 [ PAA resin: after 30g of DMF, 5g of a plasticizer (pyromellitic dianhydride) and 12.01g of ODA (4, 4-diaminodiphenyl ether) were added to the dispersion slurry obtained in the second step and sufficiently dissolved, 13.09g of PMDA (pyromellitic dianhydride) was added in a small amount to the reaction system in a plurality of times, and the reaction system was controlled to 10 ℃ or lower.
Step four, vacuum imidization: mixing Fe in the third step 3 O 4 The PAA resin adopts vacuum imidization to complete Fe 3 O 4 Preparing a/PI composite material, wherein the vacuum imidization conditions are as follows: the temperature is raised at a rate of 2 ℃/min from the room temperature to 320 ℃, and the temperature is kept at 320 ℃ for 5min.
Example 2
Fe 3 O 4 The ferroferric oxide filling amount in the PI composite material is 15wt%.
Step one, synthesizing Fe by solvothermal method 3 O 4 ：3mmol FeCl 3 ·6H 2 O and 48mL EG were dissolved well in a glass beaker, 15mmol urea was added to the solution and stirring was continued until complete dissolution and finally 6mmol CTAB was added to the solution and stirring at high speed continued until all solids were dissolved. Transferring the dissolved solution into a 50mL reaction kettle, placing the reaction kettle in a forced air drying oven, preserving the temperature at 220 ℃ for 24h, placing the reaction kettle in flowing water, rapidly cooling to room temperature, and synthesizingThe black solid is separated, washed by absolute ethyl alcohol and dried for later use. After multiple times of or amplification experiments, 4.43g of ferroferric oxide is obtained.
Step two, magnetic filler dispersion and surface modification: taking a proper amount of ferroferric oxide in the step one, 70g of DMF (N, N-dimethylformamide) and 4.43g of dispersant BYK-2055, mechanically stirring for 24 hours, and dispersing, wherein the rotating speed is controlled to be 500-800r/min. 0.44g of TM-48 is added into the system, and the rotating speed is increased to 2500r/min for 1h.
Step three, synthesizing Fe in situ 3 O 4 PAA resin: after 30g of DMF and 5g of a plasticizer (pyromellitic dianhydride) and 12.01g of ODA (4, 4-diaminodiphenyl ether) were added to the dispersion slurry obtained in the second step and sufficiently dissolved, 13.09g of PMDA (pyromellitic dianhydride) was added in a small amount to the reaction system several times, and the reaction system was controlled to 10 ℃ or lower.
Step four, vacuum imidization: mixing Fe in the third step 3 O 4 The PAA resin adopts vacuum imidization to complete Fe 3 O 4 The preparation method of the/PI composite material comprises the following steps of: the temperature is raised at a rate of 2 ℃/min from the room temperature to 320 ℃, and the temperature is kept at 320 ℃ for 5min.
Example 3
Fe 3 O 4 The ferroferric oxide filling amount in the/PI composite material is 20wt%.
Step one, synthesizing Fe by solvothermal method 3 O 4 ：3mmol FeCl 3 ·6H 2 O and 48mL EG were dissolved well in a glass beaker, 15mmol urea was added to the solution, stirring was continued until complete dissolution, and finally 6mmol CTAB was added to the solution and stirring at high speed continued until all solids were dissolved. Transferring the dissolved solution into a 50mL reaction kettle, placing the reaction kettle into a forced air drying oven, preserving the temperature at 220 ℃ for 24 hours, placing the reaction kettle into flowing water, rapidly cooling to room temperature, separating the synthesized black solid, washing with absolute ethyl alcohol, and drying for later use. 6.28g of ferroferric oxide is obtained through multiple times of or amplification experiments.
Step two, magnetic filler dispersion and surface modification: taking a proper amount of ferroferric oxide in the step one, 70g of DMF (N, N-dimethylformamide) and 6.28g of dispersant BYK-2055, mechanically stirring for 24 hours, and dispersing, wherein the rotating speed is controlled to be 500-800r/min. 0.63g of TM-48 is added into the system, and the rotating speed is increased to 2500r/min for 1h.
Step three, in-situ synthesis of Fe 3 O 4 PAA resin: after 30g of DMF and 5g of a plasticizer (pyromellitic dianhydride) and 12.01g of ODA (4, 4-diaminodiphenyl ether) were added to the dispersion slurry obtained in the second step and sufficiently dissolved, 13.09g of PMDA (pyromellitic dianhydride) was added in a small amount to the reaction system several times, and the reaction system was controlled to 10 ℃ or lower.
Step four, vacuum imidization: mixing Fe in the third step 3 O 4 The PAA resin adopts vacuum imidization to complete Fe 3 O 4 Preparing a/PI composite material, wherein the vacuum imidization conditions are as follows: the temperature is raised at a rate of 2 ℃/min from the room temperature to 320 ℃, and the temperature is kept at 320 ℃ for 5min.
Example 4
Fe 3 O 4 The ferroferric oxide filling amount in the/PI composite material is 25wt%.
Step one, synthesizing Fe by solvothermal method 3 O 4 ：3mmol FeCl 3 ·6H 2 O and 48mL EG were dissolved well in a glass beaker, 15mmol urea was added to the solution and stirring was continued until complete dissolution and finally 6mmol CTAB was added to the solution and stirring at high speed continued until all solids were dissolved. Transferring the dissolved solution into a 50mL reaction kettle, placing the reaction kettle into a forced air drying oven, preserving the temperature at 220 ℃ for 24 hours, placing the reaction kettle into flowing water, rapidly cooling to room temperature, separating the synthesized black solid, washing with absolute ethyl alcohol, and drying for later use. 8.37g of ferroferric oxide is obtained through a plurality of times of or amplification experiments.
Step two, magnetic filler dispersion and surface modification: taking a proper amount of ferroferric oxide in the step one, 70g of DMF (N, N-dimethylformamide) and 8.37g of dispersant BYK-2055, and mechanically stirring and dispersing for 24 hours, wherein the rotating speed is controlled to be 500-800r/min. 0.84g of TM-48 is added into the system, and the rotating speed is increased to 2500r/min for 1 hour.
Step three, in-situ synthesis of Fe 3 O 4 PAA resin:after 30g of DMF, 5g of a plasticizer (pyromellitic dianhydride) and 12.01g of ODA (4, 4-diaminodiphenyl ether) were added to the dispersion slurry obtained in the second step and sufficiently dissolved, 13.09g of PMDA (pyromellitic dianhydride) was added in a small amount to the reaction system in a plurality of times, and the reaction system was controlled to 10 ℃ or lower.
Step four, vacuum imidization: mixing Fe in the third step 3 O 4 The PAA resin adopts vacuum imidization to complete Fe 3 O 4 Preparing a/PI composite material, wherein the vacuum imidization conditions are as follows: the temperature is raised at a rate of 2 ℃/min from room temperature to 320 ℃, and the temperature is kept at 320 ℃ for 5min.
Example 5
Co element doped Fe 3 O 4 The filler loading in the/PI composite was 20 wt.%.
Step one, synthesizing Co-doped Fe by solvothermal method 3 O 4 ：2mmol FeCl 3 ·6H 2 O、1mmol CoCl 2 ·6H 2 O and 48mL EG were dissolved well in a glass beaker, 15mmol urea was added to the solution, stirring was continued until complete dissolution, and finally 6mmol CTAB was added to the solution and stirring at high speed continued until all solids were dissolved. Transferring the dissolved solution into a 50mL reaction kettle, placing the reaction kettle into a forced air drying oven, preserving the temperature at 220 ℃ for 24 hours, placing the reaction kettle into flowing water, rapidly cooling to room temperature, separating the synthesized black solid, washing with absolute ethyl alcohol, and drying for later use. 6.28g of Co-doped ferroferric oxide is obtained through multiple times of or amplification experiments.
Step two, magnetic filler dispersion and surface modification: taking a proper amount of Co-doped ferroferric oxide in the step one, 70g of DMF (N, N-dimethylformamide) and 6.28g of dispersant BYK-2055, and mechanically stirring and dispersing for 24 hours, wherein the rotating speed is controlled to be 500-800r/min. 0.63g of TM-48 is added into the system, and the rotating speed is increased to 2500r/min for 1h.
Step three, in-situ synthesis of Co-doped Fe 3 O 4 [ PAA resin: after 30g of DMF and 5g of a plasticizer (pyromellitic dianhydride) and 12.01g of ODA (4, 4-diaminodiphenyl ether) were added to the dispersion slurry obtained in the second step and sufficiently dissolved, 13.09g of PMDA (pyromellitic dianhydride) was added in a small amountAdding the reaction system for multiple times, and controlling the temperature of the reaction system to be below 10 ℃.
Step four, vacuum imidization: doping Co in the third step with Fe 3 O 4 Method for completing Co-doped Fe by adopting PAA resin through vacuum imidization 3 O 4 Preparing a/PI composite material, wherein the vacuum imidization conditions are as follows: the temperature is raised at a rate of 2 ℃/min from room temperature to 320 ℃, and the temperature is kept at 320 ℃ for 5min.
Example 6
Mn element doped Fe 3 O 4 The filler loading in the/PI composite was 20% by weight.
Step one, synthesizing Mn doped Fe by solvothermal method 3 O 4 ：2mmol FeCl 3 ·6H 2 O、1mmol MnCl 2 ·6H 2 O and 48mL EG were dissolved well in a glass beaker, 15mmol urea was added to the solution and stirring was continued until complete dissolution and finally 6mmol CTAB was added to the solution and stirring at high speed continued until all solids were dissolved. Transferring the dissolved solution into a 50mL reaction kettle, placing the reaction kettle into a forced air drying oven, preserving the temperature at 220 ℃ for 24 hours, placing the reaction kettle into flowing water, rapidly cooling to room temperature, separating the synthesized black solid, washing with absolute ethyl alcohol, and drying for later use. 6.28g of Mn-doped ferroferric oxide is obtained through multiple times of or amplified experiments.
Step two, magnetic filler dispersion and surface modification: taking a proper amount of Mn-doped ferroferric oxide in the step one, 70g of DMF (N, N-dimethylformamide) and 6.28g of dispersant BYK-2055, mechanically stirring and dispersing for 24 hours, and controlling the rotating speed to 500-800r/min. 0.63g of TM-48 is added into the system, and the rotating speed is increased to 2500r/min for 1h.
Step three, in-situ synthesis of Mn-doped Fe 3 O 4 PAA resin: after 30g of DMF and 5g of a plasticizer (pyromellitic dianhydride) and 12.01g of ODA (4, 4-diaminodiphenyl ether) were added to the dispersion slurry obtained in the second step and sufficiently dissolved, 13.09g of PMDA (pyromellitic dianhydride) was added in a small amount to the reaction system several times, and the reaction system was controlled to 10 ℃ or lower.
Step four, vacuum imidization: doping Mn in the third step with Fe 3 O 4 Method for completing Mn doped Fe by adopting PAA resin through vacuum imidization 3 O 4 Preparing a/PI composite material, wherein the vacuum imidization conditions are as follows: the temperature is raised at a rate of 2 ℃/min from the room temperature to 320 ℃, and the temperature is kept at 320 ℃ for 5min.
Example 7
Fe doped with Ni element 3 O 4 The filler loading in the/PI composite was 20% by weight.
Step one, synthesizing Ni-doped Fe by solvothermal method 3 O 4 ：2mmol FeCl 3 ·6H 2 O、1mmol NiCl 2 ·6H 2 O and 48mL EG were dissolved well in a glass beaker, 15mmol urea was added to the solution, stirring was continued until complete dissolution, and finally 6mmol CTAB was added to the solution and stirring at high speed continued until all solids were dissolved. Transferring the dissolved solution into a 50mL reaction kettle, placing the reaction kettle into a forced air drying oven, preserving the temperature at 220 ℃ for 24 hours, placing the reaction kettle into flowing water, rapidly cooling to room temperature, separating the synthesized black solid, washing with absolute ethyl alcohol, and drying for later use. 6.28g of Ni-doped ferroferric oxide is obtained through a plurality of times of or amplification experiments.
Step two, magnetic filler dispersion and surface modification: taking a proper amount of Ni-doped ferroferric oxide in the step one, 70g of DMF (N, N-dimethylformamide) and 6.28g of dispersant BYK-2055, mechanically stirring and dispersing for 24 hours, and controlling the rotating speed to 500-800r/min. 0.63g of TM-48 is added into the system, and the rotating speed is increased to 2500r/min for 1h.
Step three, in-situ synthesis of Ni-doped Fe 3 O 4 PAA resin: after 30g of DMF and 5g of a plasticizer (pyromellitic dianhydride) and 12.01g of ODA (4, 4-diaminodiphenyl ether) were added to the dispersion slurry obtained in the second step and sufficiently dissolved, 13.09g of PMDA (pyromellitic dianhydride) was added in a small amount to the reaction system several times, and the reaction system was controlled to 10 ℃ or lower.
Step four, vacuum imidization: the Fe3O4/PAA resin in the third step is subjected to vacuum imidization to complete Ni doping Fe 3 O 4 Preparing a/PI composite material, wherein the vacuum imidization conditions are as follows: the temperature is raised at a rate of 2 ℃/min from the room temperature to 320 ℃, and the temperature is kept at 320 DEG C5min。
The thermal conductivity of the composite materials prepared in the above examples in the presence or absence of an external magnetic field is shown in tables 1 and 2 and fig. 1 to 2. The magnetic domain structure of the composite material in the presence or absence of an external magnetic field is shown in fig. 3 to 6.
TABLE 1 thermal conductivity coefficient of ferroferric oxide polyimide composite material with different filling amount
Filling amount (wt%) 10 15 20 25
Non-magnetic field heat conductivity coefficient (W/m. K) 0.3 0.33 0.36 0.41
Thermal conductivity coefficient with magnetic field (W/m. K) 0.34 0.38 0.44 0.55
TABLE 2 thermal conductivity of ferroferric oxide polyimide composite material with same filling amount (20 wt%) and different doping elements
Doping element Is not doped Co Mn Ni
Non-magnetic field heat conductivity coefficient (W/m. K) 0.36 0.32 0.35 0.35
Thermal conductivity coefficient with magnetic field (W/m. K) 0.44 0.4 0.42 0.4
It can be seen from the above studies that the polyimide composite material synthesized in the above embodiments changes the magnetic domain structure under the action of the external magnetic field, reduces the thermal resistance, increases the thermal conductivity, and improves the thermal conductivity. The higher the filler content is, the greater the influence of an external magnetic field on the heat-conducting property of the composite material is. The influence of an external magnetic field on the heat-conducting property of the ferroferric oxide polyimide composite material doped with different elements is different, so that the multifunctional polyimide composite material with different magnetic properties and heat-conducting properties under the condition of the external magnetic field can be prepared by doping different elements and different contents or doping multiple elements.
The foregoing is considered as illustrative of the preferred embodiments of the invention and is not to be construed as limiting the invention in any way. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical spirit of the present invention should fall within the protection scope of the technical scheme of the present invention, unless the technical spirit of the present invention departs from the content of the technical scheme of the present invention.

Claims (9)

1. A preparation method of a magnetic heat-conducting polyimide composite material is characterized by comprising the following steps:
(1) Dissolving ferric salt or ferric salt and a salt of a doping element M in ethylene glycol, adding urea and hexadecyl trimethyl ammonium bromide, stirring and dissolving, keeping the temperature at 200-240 ℃ for 15-30 h, and cooling to obtain nano ferroferric oxide or nano doped ferroferric oxide, wherein the doping element M comprises one or more of Co, mn or Ni;
(2) Mixing the ferroferric oxide or doped ferroferric oxide obtained in the step (1) with a solvent and a dispersant, stirring and dispersing, and then adding a surface modifier for modification to obtain dispersed slurry;
(3) And (3) adding a raw material for synthesizing polyamic acid into the dispersed slurry obtained in the step (2), synthesizing polyamic acid, and then carrying out imidization to obtain the ferroferric oxide/polyimide composite material or the doped ferroferric oxide/polyimide composite material.
2. The method according to claim 1, wherein the iron salt is FeCl 3-6H 2O, and the salt of M is MCl2; in the raw materials for synthesizing the ferroferric oxide, the mass ratio of FeCl3.6H2O, EG, urea and CTAB is (0.8-1.2): (14-20): (3-7): (1-3); in the raw material for synthesizing the doped ferroferric oxide, the mass ratio of FeCl3.6H2O, MCl2, EG, urea and CTAB is (0.5-0.8): (0.3-0.4): (14-20): (3-7): (1-3).
3. The method according to claim 1, wherein the cooling treatment of step (1) is rapid cooling in flowing water.
4. The preparation method according to claim 1, wherein in the step (2), the solvent and the dispersant are mixed, the rotation speed is controlled to be 500-800r/min, the mixture is stirred and dispersed for 15-30 h, then the surface modifier is added, the rotation speed is increased to be 2000-3000 r/min, and the mixture is stirred for 0.5-1.5 h.
5. The preparation method according to claim 1 or 4, wherein the surface modifier is a titanate coupling agent and/or a silane coupling agent, and the dosage of the surface modifier is 3-10wt% of ferroferric oxide or doped ferroferric oxide.
6. The preparation method according to claim 1 or 4, wherein the dispersant comprises one or more of BYK-2055, BYK-161, BYK-160 or BYK-2050, and the dosage of the dispersant is 3-10wt% of ferroferric oxide or doped ferroferric oxide.
7. The method according to claim 1, wherein the raw materials for synthesizing the polyamic acid in the step (3) comprise an aromatic diamine, an aromatic dianhydride, and a plasticizer, and the reaction temperature is controlled to be 10 ℃ or lower.
8. A magnetic heat-conducting polyimide composite material is characterized by being prepared by the method of any one of claims 1 to 7 and comprising polyimide and hollow nano-spherical ferroferric oxide or doped ferroferric oxide dispersed in the polyimide.
9. The composite material according to claim 8, wherein the ferroferric oxide or doped ferroferric oxide is filled in an amount of 10-25 wt% of the composite material.
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