CN114806090B - High-heat-conductivity insulating epoxy resin composite material and preparation method thereof - Google Patents
High-heat-conductivity insulating epoxy resin composite material and preparation method thereof Download PDFInfo
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- CN114806090B CN114806090B CN202210424285.6A CN202210424285A CN114806090B CN 114806090 B CN114806090 B CN 114806090B CN 202210424285 A CN202210424285 A CN 202210424285A CN 114806090 B CN114806090 B CN 114806090B
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- 239000003822 epoxy resin Substances 0.000 title claims abstract description 68
- 229920000647 polyepoxide Polymers 0.000 title claims abstract description 68
- 239000002131 composite material Substances 0.000 title claims abstract description 57
- 238000002360 preparation method Methods 0.000 title claims abstract description 28
- PZNSFCLAULLKQX-UHFFFAOYSA-N Boron nitride Chemical class N#B PZNSFCLAULLKQX-UHFFFAOYSA-N 0.000 claims abstract description 87
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical class C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims abstract description 86
- 239000003085 diluting agent Substances 0.000 claims abstract description 24
- 239000003795 chemical substances by application Substances 0.000 claims abstract description 12
- 239000000203 mixture Substances 0.000 claims abstract description 12
- 229920000049 Carbon (fiber) Polymers 0.000 claims description 47
- 239000004917 carbon fiber Substances 0.000 claims description 47
- 229910052582 BN Inorganic materials 0.000 claims description 27
- 239000000243 solution Substances 0.000 claims description 27
- 238000001723 curing Methods 0.000 claims description 21
- 238000003756 stirring Methods 0.000 claims description 21
- 239000002994 raw material Substances 0.000 claims description 20
- 239000006087 Silane Coupling Agent Substances 0.000 claims description 19
- CTENFNNZBMHDDG-UHFFFAOYSA-N Dopamine hydrochloride Chemical compound Cl.NCCC1=CC=C(O)C(O)=C1 CTENFNNZBMHDDG-UHFFFAOYSA-N 0.000 claims description 15
- 229960001149 dopamine hydrochloride Drugs 0.000 claims description 15
- 238000010438 heat treatment Methods 0.000 claims description 12
- 239000011268 mixed slurry Substances 0.000 claims description 10
- 229920001690 polydopamine Polymers 0.000 claims description 10
- 238000001035 drying Methods 0.000 claims description 9
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 claims description 8
- 150000001721 carbon Chemical class 0.000 claims description 8
- 238000002156 mixing Methods 0.000 claims description 8
- 238000005406 washing Methods 0.000 claims description 7
- 239000007795 chemical reaction product Substances 0.000 claims description 6
- DOIRQSBPFJWKBE-UHFFFAOYSA-N dibutyl phthalate Chemical compound CCCCOC(=O)C1=CC=CC=C1C(=O)OCCCC DOIRQSBPFJWKBE-UHFFFAOYSA-N 0.000 claims description 6
- 239000007983 Tris buffer Substances 0.000 claims description 4
- 238000000034 method Methods 0.000 claims description 4
- LENZDBCJOHFCAS-UHFFFAOYSA-N tris Chemical compound OCC(N)(CO)CO LENZDBCJOHFCAS-UHFFFAOYSA-N 0.000 claims description 4
- YSUQLAYJZDEMOT-UHFFFAOYSA-N 2-(butoxymethyl)oxirane Chemical compound CCCCOCC1CO1 YSUQLAYJZDEMOT-UHFFFAOYSA-N 0.000 claims description 3
- RNLHGQLZWXBQNY-UHFFFAOYSA-N 3-(aminomethyl)-3,5,5-trimethylcyclohexan-1-amine Chemical compound CC1(C)CC(N)CC(C)(CN)C1 RNLHGQLZWXBQNY-UHFFFAOYSA-N 0.000 claims description 3
- RPNUMPOLZDHAAY-UHFFFAOYSA-N Diethylenetriamine Chemical compound NCCNCCN RPNUMPOLZDHAAY-UHFFFAOYSA-N 0.000 claims description 3
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 3
- 229920002239 polyacrylonitrile Polymers 0.000 claims description 3
- FAGUFWYHJQFNRV-UHFFFAOYSA-N tetraethylenepentamine Chemical compound NCCNCCNCCNCCN FAGUFWYHJQFNRV-UHFFFAOYSA-N 0.000 claims description 3
- 238000005303 weighing Methods 0.000 claims description 3
- 239000010426 asphalt Substances 0.000 claims description 2
- LNEPOXFFQSENCJ-UHFFFAOYSA-N haloperidol Chemical compound C1CC(O)(C=2C=CC(Cl)=CC=2)CCN1CCCC(=O)C1=CC=C(F)C=C1 LNEPOXFFQSENCJ-UHFFFAOYSA-N 0.000 claims description 2
- 239000000945 filler Substances 0.000 abstract description 24
- 239000011256 inorganic filler Substances 0.000 abstract description 9
- 229910003475 inorganic filler Inorganic materials 0.000 abstract description 9
- 238000009413 insulation Methods 0.000 abstract description 7
- 238000005286 illumination Methods 0.000 abstract description 4
- 238000004100 electronic packaging Methods 0.000 abstract description 3
- 239000000126 substance Substances 0.000 abstract description 3
- 238000010292 electrical insulation Methods 0.000 abstract description 2
- 230000000052 comparative effect Effects 0.000 description 20
- 230000004048 modification Effects 0.000 description 18
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- 229920000642 polymer Polymers 0.000 description 8
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- 238000002329 infrared spectrum Methods 0.000 description 6
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- 239000006185 dispersion Substances 0.000 description 5
- 241000276425 Xiphophorus maculatus Species 0.000 description 4
- IISBACLAFKSPIT-UHFFFAOYSA-N bisphenol A Chemical compound C=1C=C(O)C=CC=1C(C)(C)C1=CC=C(O)C=C1 IISBACLAFKSPIT-UHFFFAOYSA-N 0.000 description 4
- VYFYYTLLBUKUHU-UHFFFAOYSA-N dopamine Chemical compound NCCC1=CC=C(O)C(O)=C1 VYFYYTLLBUKUHU-UHFFFAOYSA-N 0.000 description 4
- BDAGIHXWWSANSR-UHFFFAOYSA-N methanoic acid Natural products OC=O BDAGIHXWWSANSR-UHFFFAOYSA-N 0.000 description 4
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- 239000000463 material Substances 0.000 description 3
- OSWFIVFLDKOXQC-UHFFFAOYSA-N 4-(3-methoxyphenyl)aniline Chemical compound COC1=CC=CC(C=2C=CC(N)=CC=2)=C1 OSWFIVFLDKOXQC-UHFFFAOYSA-N 0.000 description 2
- 238000010521 absorption reaction Methods 0.000 description 2
- 230000002411 adverse Effects 0.000 description 2
- 239000007853 buffer solution Substances 0.000 description 2
- 229960003638 dopamine Drugs 0.000 description 2
- IDGUHHHQCWSQLU-UHFFFAOYSA-N ethanol;hydrate Chemical compound O.CCO IDGUHHHQCWSQLU-UHFFFAOYSA-N 0.000 description 2
- 238000011049 filling Methods 0.000 description 2
- 235000019253 formic acid Nutrition 0.000 description 2
- 238000013007 heat curing Methods 0.000 description 2
- 239000007788 liquid Substances 0.000 description 2
- 239000011295 pitch Substances 0.000 description 2
- 239000002861 polymer material Substances 0.000 description 2
- 239000000843 powder Substances 0.000 description 2
- 238000012545 processing Methods 0.000 description 2
- 238000001132 ultrasonic dispersion Methods 0.000 description 2
- QKNYBSVHEMOAJP-UHFFFAOYSA-N 2-amino-2-(hydroxymethyl)propane-1,3-diol;hydron;chloride Chemical compound Cl.OCC(N)(CO)CO QKNYBSVHEMOAJP-UHFFFAOYSA-N 0.000 description 1
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- 244000137852 Petrea volubilis Species 0.000 description 1
- 229910018557 Si O Inorganic materials 0.000 description 1
- 238000009825 accumulation Methods 0.000 description 1
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- 239000004841 bisphenol A epoxy resin Substances 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 239000011304 carbon pitch Substances 0.000 description 1
- 238000012512 characterization method Methods 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 238000013329 compounding Methods 0.000 description 1
- 239000011231 conductive filler Substances 0.000 description 1
- 239000004020 conductor Substances 0.000 description 1
- 239000008367 deionised water Substances 0.000 description 1
- 229910021641 deionized water Inorganic materials 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- 230000017525 heat dissipation Effects 0.000 description 1
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- 238000006460 hydrolysis reaction Methods 0.000 description 1
- 238000011068 loading method Methods 0.000 description 1
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- 229920001343 polytetrafluoroethylene Polymers 0.000 description 1
- 239000004810 polytetrafluoroethylene Substances 0.000 description 1
- LIVNPJMFVYWSIS-UHFFFAOYSA-N silicon monoxide Inorganic materials [Si-]#[O+] LIVNPJMFVYWSIS-UHFFFAOYSA-N 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 230000002195 synergetic effect Effects 0.000 description 1
- 238000009210 therapy by ultrasound Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Classifications
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K3/00—Use of inorganic substances as compounding ingredients
- C08K3/38—Boron-containing compounds
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K7/00—Use of ingredients characterised by shape
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K7/00—Use of ingredients characterised by shape
- C08K7/02—Fibres or whiskers
- C08K7/04—Fibres or whiskers inorganic
- C08K7/06—Elements
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K9/00—Use of pretreated ingredients
- C08K9/04—Ingredients treated with organic substances
- C08K9/06—Ingredients treated with organic substances with silicon-containing compounds
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K9/00—Use of pretreated ingredients
- C08K9/10—Encapsulated ingredients
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K3/00—Use of inorganic substances as compounding ingredients
- C08K3/38—Boron-containing compounds
- C08K2003/382—Boron-containing compounds and nitrogen
- C08K2003/385—Binary compounds of nitrogen with boron
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L2203/00—Applications
- C08L2203/20—Applications use in electrical or conductive gadgets
- C08L2203/206—Applications use in electrical or conductive gadgets use in coating or encapsulating of electronic parts
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- Chemical & Material Sciences (AREA)
- Health & Medical Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Medicinal Chemistry (AREA)
- Polymers & Plastics (AREA)
- Organic Chemistry (AREA)
- Compositions Of Macromolecular Compounds (AREA)
Abstract
The invention belongs to the technical field of heat-conducting insulating composite materials, and discloses a high-heat-conducting insulating epoxy resin composite material and a preparation method thereof, wherein the composite material prepared by the invention comprises 100 parts of epoxy resin, 20-30 parts of curing agent, 5-35 parts of inorganic filler and 10-20 parts of diluent, wherein the inorganic filler is a mixture of modified boron nitride and modified carbon fiber. In addition, the invention also discloses a preparation method of the composite material. The high-heat-conductivity insulating epoxy resin composite material prepared by the invention has excellent heat conduction performance and electrical insulation, achieves the heat conductivity of 1.505 Wm ‑1K‑1 and the volume resistivity of 3.25E+11 Ω & cm under the condition of low filler content (18.71 wt percent), and has great application prospect in the fields requiring heat conduction, such as heat exchangers in chemical industry, and the fields requiring heat conduction and insulation, such as LED illumination, electronic packaging and the like.
Description
Technical Field
The invention belongs to the field of heat-conducting insulating composite materials, and particularly relates to a high-heat-conducting insulating epoxy resin composite material and a preparation method thereof.
Background
With the rapid development of 5G, consumer electronics, LED illumination and aerospace technology, the power density and heat flow density of novel devices and equipment are continuously increased, and excessive heat accumulation can seriously threaten the performance and stability of the devices and greatly reduce the service life of the devices. The rapid heat dissipation to the outside by using a material having excellent heat conduction properties is an important way to solve this problem. Because of the characteristics of low cost, easy processing, excellent insulating property and the like, the polymer material is widely applied in a plurality of fields, but the inherent low thermal conductivity (< 0.5 Wm -1K-1) of the polymer limits the application of the polymer material in the field of thermal management.
The addition of inorganic and metallic fillers with excellent thermal conductivity to polymers is a common method to increase the thermal conductivity of polymers, but the increase in thermal conductivity of polymers by the addition of fillers tends to be quite far from theoretical due mainly to weak interaction forces between the filler and the polymer, the inability of the filler to disperse uniformly and the extremely high thermal resistance between the filler and the polymer. In addition, if a large amount of filler is added to obtain a polymer composite material with high thermal conductivity, the addition of a large amount of filler causes cost increase, mechanical properties and processability of the material to be lowered, and how to obtain a polymer composite material with high thermal conductivity at a low filler content remains a great challenge.
Disclosure of Invention
Aiming at the problems and the defects existing in the prior art, the invention aims to provide a high-heat-conductivity insulating epoxy resin composite material and a preparation method thereof.
Based on the above purpose, the invention adopts the following technical scheme:
the invention provides a high-heat-conductivity insulating epoxy resin composite material which is mainly prepared from the following raw material components in parts by weight: 100 parts of epoxy resin, 20-30 parts of curing agent and 5-35 parts of inorganic filler; the inorganic filler is a mixture of modified boron nitride and modified carbon fiber.
Preferably, the modified boron nitride is prepared by modifying hexagonal boron nitride by a silane coupling agent; the modified carbon fiber is prepared by modifying carbon fiber with polydopamine.
Preferably, the preparation steps of the modified boron nitride specifically include: adding boron nitride into the hydrolyzed silane coupling agent solution, uniformly dispersing, heating to 91-95 ℃, stirring and reacting for 6-8 h, washing and drying to obtain modified boron nitride; the addition amount of the silane coupling agent is 1-15% of the mass of the boron nitride.
More preferably, the dispersion during the modification of the boron nitride is ultrasonic dispersion for 30min, and the drying temperature is 60 ℃.
More preferably, the preparation steps of the hydrolyzed silane coupling agent solution specifically include: adding the silane coupling agent into 95% ethanol water solution, adding formic acid to adjust the pH to 3-5, and stirring for 15min to obtain hydrolyzed silane coupling agent solution.
Preferably, the preparation steps of the modified carbon fiber specifically include: preparing a dopamine hydrochloride solution by using a Tris buffer solution, adding carbon fibers into the dopamine hydrochloride solution, uniformly dispersing, stirring and reacting for 6-24 hours at 50 ℃ to obtain a reaction product A, washing and centrifuging the reaction product A, and drying to obtain modified carbon fibers; the mass ratio of the carbon fiber to the dopamine hydrochloride is 1:0.8-10.
More preferably, the dispersion during the modification of the carbon fibers is ultrasonic dispersion for 30min, and the drying temperature is 60 ℃.
More preferably, the concentration of the Tris buffer is 10mmol/L and the pH is 8-9; the concentration of the dopamine hydrochloride solution is 0.25-2 g/L.
More preferably, the modified hexagonal boron nitride has a size of 3 to 35 μm; the length dimension of the modified asphalt-based carbon fiber is 30-300 mu m.
Preferably, the mass ratio of the modified boron nitride to the modified carbon fiber in the inorganic filler is (2-10) to (5-20).
Preferably, the silane coupling agent is at least one of KH-550, KH-560 and KH-792, and the carbon fiber is any one of polyacrylonitrile-based carbon fiber and pitch-based carbon fiber.
Preferably, the epoxy resin is any one of bisphenol A type epoxy resins E12, E31 and E51; the curing agent is any one of adducts of isophorone diamine, tetraethylene pentamine, diethylenetriamine and butyl glycidyl ether,
Preferably, the raw material component further comprises a diluent, wherein the weight part of the diluent is 10-20 parts; the diluent is any one of absolute ethyl alcohol, acetone and dibutyl phthalate.
The second aspect of the invention provides a preparation method of the high-heat-conductivity insulating epoxy resin composite material according to the first aspect, which comprises the following steps:
(1) Weighing the raw material components according to the parts by weight of the first aspect, mixing the modified boron nitride and the modified carbon fiber, and uniformly stirring to obtain a modified mixture;
(2) Sequentially adding epoxy resin and a curing agent into the modified mixture obtained in the step (1), and stirring and dispersing to obtain mixed slurry;
(3) And (3) injecting the mixed slurry obtained in the step (2) into a mold, and heating and curing in stages to obtain the high-heat-conductivity insulating epoxy resin composite material.
More preferably, in the step (1), the modified boron nitride and the modified carbon fiber are uniformly mixed in a closed container, and the mixing time is 10min.
More preferably, the specific steps of adding the epoxy resin into the step (2) for stirring and dispersing are as follows: magnetically stirring at 60 ℃ for 1h, and ultrasonically dispersing for 1h.
More preferably, the specific steps of stirring and dispersing after adding the curing agent in the step (2) are as follows: magnetically stirring at room temperature for 10min, and ultrasonically dispersing for 10min.
Preferably, the specific steps of the staged heat curing in the step (3) are as follows: curing for 4h in an oven at 30 ℃, and then heating to 80 ℃ for further curing for 4h.
When the raw material component contains the diluent, premixing the diluent and the epoxy resin in the step (2), uniformly stirring to obtain a mixed solution of the epoxy resin and the diluent, and then adding the obtained mixed solution of the epoxy resin and the diluent to the modified mixture obtained in the step (1) instead of the epoxy resin for stirring and dispersing.
More preferably, when the raw material component contains a diluent, the specific step of the staged heat curing in step (3) is: curing for 4h in an oven at 30 ℃, then heating to 80 ℃ for 4h, and finally heating to 120 ℃ and maintaining for 12h.
Compared with the prior art, the invention has the following beneficial effects:
(1) According to the invention, modified boron nitride and modified carbon fiber are used as inorganic filler to prepare the epoxy resin composite material, and the platy modified boron nitride and the platy modified carbon fiber are used in a mixed manner, so that the platy modified boron nitride can be connected with the platy modified carbon fiber to form a heat conduction path or network, and the epoxy resin composite material with high heat conduction and insulation is obtained under the condition of low filler content. In one of the embodiments, the invention gives epoxy resin composites with excellent thermal conductivity and insulation properties at low filler content (18.71 wt%), with thermal conductivity up to 1.505 Wm -1K-1, volume resistivity up to 3.25E+11 Ω cm,
The heat-conducting material can be applied to the fields requiring heat conduction, such as heat exchangers in chemical industry, and the fields requiring heat conduction and insulation, such as LED illumination, electronic packaging and the like.
(2) The modified boron nitride prepared by the invention is prepared by modifying hexagonal boron nitride by a silane coupling agent, and the modified carbon fiber is prepared by modifying carbon fiber by polydopamine. According to the invention, the dispersibility of the boron nitride and the carbon fiber in the epoxy resin is improved, the viscosity is reduced, the processing performance is improved, the defects in the composite material can be reduced, the thermal conductivity of the composite material is improved, the interaction force between the filler and the epoxy resin value is increased, and the scattering degree of phonons at the interface is reduced, so that the thermal resistance is reduced.
(3) Further, the invention adopts polydopamine to coat the modified carbon fiber. This is because, although carbon fiber is an important carbon-based heat conductive filler, its axial thermal conductivity can be as high as 800 Wm -1K-1, but its excellent electrical conductivity limits its application of heat conductive properties. Therefore, the insulating polydopamine shell can prevent the addition of the polydopamine shell from adversely affecting the electrical insulation performance of the epoxy resin while utilizing the excellent heat conduction performance of the carbon fiber. In one embodiment, when the modified boron nitride and the modified carbon fiber are mixed to improve the thermal conductivity of the epoxy resin matrix to obtain the optimal effect, the filling amount of the modified carbon fiber is up to 7.23 wt%, and the volume resistivity of the composite material prepared by the method is still up to 3.25E+1Ω & cm due to the modification of polydopamine.
Drawings
FIG. 1 is an infrared spectrum of boron nitride before and after modification in an embodiment of the invention;
FIG. 2 is a scanning electron microscope image of boron nitride prior to modification in an embodiment of the present invention;
FIG. 3 is a scanning electron microscope image of modified boron nitride in an embodiment of the invention;
FIG. 4 is an infrared spectrum of carbon fiber before and after modification in an embodiment of the present invention;
FIG. 5 is a scanning electron microscope image of a carbon fiber before modification in an embodiment of the present invention;
fig. 6 is a scanning electron microscope image of the modified carbon fiber in the embodiment of the present invention.
Detailed Description
The present invention will be further described in detail below with reference to the accompanying drawings by way of examples in order to make the objects, technical solutions and advantages of the present invention more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.
It should be noted that, without conflict, the embodiments of the present application and features of the embodiments may be combined with each other. The application will be described in detail below with reference to the drawings in connection with embodiments.
Example 1
The embodiment of the invention provides a high-heat-conductivity insulating epoxy resin composite material which is prepared from the following raw material components in parts by mass: 100g of E51 epoxy resin, 25g of curing agent (adduct of diethylenetriamine and butyl glycidyl ether), 17.65g of modified boron nitride, 11.11g of modified carbon fiber and 10g of diluent (dibutyl phthalate). The preparation process comprises the following steps:
(1) Weighing the raw materials in parts by weight, and placing the modified boron nitride and the modified carbon fiber into a closed container, and shaking the container 10 min or more forcefully to uniformly mix the two materials together;
(2) Stirring epoxy resin and a diluent by using a glass rod, uniformly mixing the epoxy resin and the diluent to obtain a mixed solution of the epoxy resin and the diluent, then adding the modified boron nitride and the modified carbon fiber mixture into the mixed solution of the epoxy resin and the diluent to obtain a mixed slurry a, and magnetically stirring 1h and ultrasonic 1h at 60 ℃ to uniformly disperse the filler and remove bubbles;
(3) Adding a curing agent into the mixed slurry a obtained in the step (2), magnetically stirring at room temperature for 10min and ultrasonically stirring for 10min to obtain mixed slurry b, uniformly dispersing and removing bubbles;
(4) Pouring the mixed slurry b into a polytetrafluoroethylene mould, then placing the mould into a baking oven at 30 ℃ for curing 4h, then heating to 80 ℃ for curing 4h again, finally heating to 120 ℃ again and keeping 12h to completely remove the diluent therein, thus obtaining the high-heat-conductivity insulating epoxy resin composite material.
The preparation method of the modified boron nitride specifically comprises the following steps: preparing an ethanol water solution with the mass fraction of 95 wt%, then dropwise adding formic acid to adjust the pH value to 3-5, adding 4.5 g silane coupling agent into the 900 mL solution with the adjusted pH value, and magnetically stirring 15min to promote the hydrolysis of the silane coupling agent KH-560, so as to obtain a hydrolyzed silane coupling agent solution; 45 g hexagonal boron nitride (h-BN) is added into the hydrolyzed silane coupling agent solution, and 30 min is ultrasonically treated to promote the dispersion of the boron nitride; transferring the dispersion liquid into a three-neck flask provided with a condensing device, heating to 91-95 ℃, and then reacting for 6-8 h under mechanical stirring; and repeatedly washing the obtained modified h-BN powder with deionized water, and finally drying the modified h-BN powder in an oven at 60 ℃ for later use.
Fig. 1 shows infrared spectra of boron nitride before and after modification, and shows that the infrared spectra of modified boron nitride has a weak absorption peak near the wavenumber 1100 cm -1, which is caused by stretching vibration of an Si-O bond, and shows that the silane coupling agent successfully modifies the boron nitride. FIGS. 2 and 3 are scanning electron microscope images of boron nitride before and after modification, respectively, and as can be seen from FIG. 3, the size of the modified boron nitride is 3-35 μm; as can be seen by comparing fig. 2 and 3, the surface morphology of the boron nitride was hardly changed before and after the modification, which suggests that the modification did not damage the boron nitride structure and thus did not adversely affect the intrinsic thermal conductivity of the boron nitride.
The preparation method of the modified carbon fiber specifically comprises the following steps: preparing Tris-HCl buffer solution with pH value of 8-9 and concentration of 10mmol/L, adding dopamine hydrochloride into the buffer solution to make the concentration of the prepared dopamine hydrochloride solution be 0.25-2 g/L; adding 20 g pitch-based carbon fiber into 8L dopamine hydrochloride solution, performing ultrasonic treatment for 30min to promote the dispersion of the pitch-based carbon fiber in the solution, and performing magnetic stirring reaction for 6-24 h at 50 ℃; and repeatedly centrifuging and washing the obtained modified carbon fiber, and finally drying the modified carbon fiber in an oven at 60 ℃ for later use.
Fig. 4 shows infrared spectra of carbon fibers before and after modification, and shows that the infrared spectra of the modified carbon fibers show a wide absorption peak in the wave number range of 3400-3100 cm -1, which is caused by-O-H and-N-H of dopamine and polydopamine, which indicates that polydopamine is used for successfully modifying the carbon fibers. Fig. 5 and 6 are scanning electron microscope images of the carbon fiber before and after modification, respectively, and it can be seen from fig. 5 that the length dimension of the modified carbon fiber is 30-300 μm; as can be seen from comparing fig. 5 and 6, the surface of the modified carbon fiber becomes rough because polydopamine particles formed by oxidation and self-polymerization of dopamine are accumulated on the surface of the carbon fiber, which can promote the mechanical meshing action between the carbon fiber and the epoxy resin, and can also improve the surface activity of the carbon fiber so as to increase the interaction force between the carbon fiber and the epoxy resin.
Example 2
The content of the high-heat-conductivity insulating epoxy resin composite material is basically the same as that of the embodiment 1, except that: the amount of modified boron nitride in the raw material is 11.11g.
Example 3
The content of the high-heat-conductivity insulating epoxy resin composite material is basically the same as that of the embodiment 1, except that: the amount of modified boron nitride in the raw material is 25g.
Example 4
The content of the high-heat-conductivity insulating epoxy resin composite material is basically the same as that of the embodiment 1, except that: the raw material components do not contain a diluent; in the preparation step (2), the mixture of the epoxy resin and the diluent is not mixed, and the modified boron nitride and the modified carbon fiber mixture is directly added into the epoxy resin to obtain mixed slurry; the temperature is not raised to 120 ℃ in the preparation step (4) and is kept for 12 hours to remove the diluent.
Example 5
The content of the high-heat-conductivity insulating epoxy resin composite material is basically the same as that of the embodiment 1, except that: in the preparation step (1), the mixing operation of the modified boron nitride and the modified carbon fiber is not carried out, and in the step (2), the modified boron nitride and the modified carbon fiber are respectively added into the mixed liquid of the epoxy resin and the diluent to obtain mixed slurry.
Example 6
The content of the high-heat-conductivity insulating epoxy resin composite material is basically the same as that of the embodiment 1, except that: the raw material components are specifically as follows: bisphenol A epoxy resin E12 g, curing agent (isophorone diamine) 20g, modified boron nitride 3g, modified carbon fiber 2g, diluent (absolute ethyl alcohol) 10g; in the step of preparing the modified boron nitride, the silane coupling agent is 0.45g KH-550; in the step of preparing the modified carbon fiber, the carbon fiber is 12.8 g polyacrylonitrile-based carbon fiber.
Example 7
The content of the high-heat-conductivity insulating epoxy resin composite material is basically the same as that of the embodiment 1, except that: bisphenol A type epoxy resin E31 g, curing agent (tetraethylenepentamine) 30g, modified boron nitride 21g, modified carbon fiber 14g and diluent (acetone) 20g; in the step of preparing the modified boron nitride, 6.75g KH-792 of silane coupling agent was used.
Example 8
The content of the high-heat-conductivity insulating epoxy resin composite material is basically the same as that of the embodiment 1, except that: the raw material components comprise 2g of modified boron nitride and 20g of modified carbon fiber.
Example 9
The content of the high-heat-conductivity insulating epoxy resin composite material is basically the same as that of the embodiment 1, except that: the modified boron nitride in the raw material component is 10g, and the modified carbon fiber is 5g.
Comparative example 1
The content of the high-heat-conductivity insulating epoxy resin composite material is basically the same as that of the embodiment 1, except that: the raw materials adopt unmodified carbon fibers to replace modified carbon fibers; in the preparation process, the preparation of the modified carbon fiber is not carried out, and in the step (1), the unmodified carbon fiber and the modified boron nitride are directly mixed.
Comparative example 2
The content of the high-heat-conductivity insulating epoxy resin composite material is basically the same as that of the embodiment 1, except that: the raw materials adopt unmodified boron nitride to replace modified boron nitride; the preparation process does not carry out the preparation of modified boron nitride, and the unmodified boron nitride and the modified carbon fiber are directly adopted for mixing in the step (1).
Comparative example 3
The content of the high-heat-conductivity insulating epoxy resin composite material is basically the same as that of the embodiment 1, except that: the raw materials adopt unmodified carbon fibers to replace modified carbon fibers, and unmodified boron nitride to replace modified boron nitride; in the preparation process, the preparation of the modified carbon fiber and the modified boron nitride is not carried out, and in the step (1), the unmodified carbon fiber and the unmodified boron nitride are directly mixed.
Comparative example 4
The content of the high-heat-conductivity insulating epoxy resin composite material is basically the same as that of the embodiment 1, except that: 42.86g of unmodified boron nitride is adopted to replace 17.65g of modified boron nitride in the raw material, and modified carbon fiber is not added; the preparation process does not carry out the preparation of the modified carbon fiber and the modified boron nitride.
Performance testing
Before testing, the high heat conduction insulating epoxy resin composite material samples prepared in examples 1-3 and comparative examples 1-4 were sanded with sand paper of more than 1000 mesh to be round pieces with a diameter of about 25mm, a thickness of about 5-mm and a smooth surface. The samples were subjected to thermal conductivity testing and characterization using a TPS 2200 thermal constant analyzer from Hot Disk, sweden. The volume resistivity of the samples was measured using an HRMS-900 high temperature insulation resistance measurement system from the company marsupium, herborist. The results of the sample thermal conductivity and volume resistivity tests are shown in table 1.
TABLE 1 test results of inorganic filler types, amounts and sample thermal conductivity and volume resistivity in samples of examples 1 to 3 and comparative examples 1 to 4
From the thermal conductivity test results we found that:
From the thermal conductivity data of the samples of comparative example 3 and comparative example 4 we found that the thermal conductivity of the composite material was 1.313W m -1 K-1 when the content of the boron nitride and carbon fiber mixed filler in comparative example 3 was 18.71 wt%, whereas the thermal conductivity of the composite material (0.866W m -1 K-1) was much smaller when the filler content was much larger than that of the mixed filler (filler content up to 25.53 wt%) when boron nitride was used alone in comparative example 4. Therefore, the effect of the combination of the boron nitride and the carbon fiber is better than that of the boron nitride singly.
Thermal conductivity data for comparative example 1 and comparative examples 1 to 3 we found that when the inorganic filler content was 18.71%, the thermal conductivity of the prepared composites was as follows: example 1> comparative example 2> comparative example 1> comparative example 3 the thermal conductivity of the example 1 sample prepared with modified boron nitride and modified carbon fiber reached 1.505W m -1 K-1, higher than the composite sample prepared with modified boron nitride alone, modified carbon fiber alone, and completely unmodified filler. Therefore, the synergistic effect exists between the modified boron nitride and the modified carbon fiber in improving the heat conduction performance of the epoxy resin, and the heat conduction performance of the epoxy resin composite material can be further improved under the condition of low filler filling by the preparation method of the invention.
Since the thermal conductivity of the composite material depends not only on the content of the mixed filler, but also has a great relationship with the mixing ratio between boron nitride and carbon fiber. To explore the ratio of the amount of modified boron nitride to the amount of modified carbon fiber, we fixed the amount of modified carbon fiber and adjusted the amount of modified boron nitride to obtain samples of examples 1 to 3. From the thermal conductivity data of the samples of comparative examples 1-3, we found that, although the content of the mixed filler increases with the amount of modified boron nitride, the thermal conductivity of the prepared composite samples was as follows: example 2< example 3< example 1, wherein the filler content of example 3 is highest. Therefore, when the modified boron nitride and the modified carbon fiber are used in a mixed mode to improve the heat conductivity of the epoxy resin, the optimal mixing ratio of the modified boron nitride to the modified carbon fiber, which is explored by the application, is 17.65:11.11, and is about 1.6:1; the optimum loading was 18.71wt%.
From the volume resistivity test results we found that:
boron nitride and carbon fiber modification help the composite maintain excellent insulation properties. As can be seen from the volume resistivity test results in table 1, the volume resistivity of the sample of only modified carbon fiber (comparative example 2) was 9.13e+9Ω·cm, while the volume resistivity of the sample of unmodified filler (comparative example 3) was only 7.68e+7Ω·cm, indicating that the carbon fiber modification significantly improved the resistivity of the composite material. Meanwhile, the volume resistivity of the sample of modified boron nitride alone (comparative example 1) was 8.01E+8Ω·cm, which is slightly higher than that of the sample of unmodified filler (comparative example 3), indicating that the boron nitride modification also increases the resistivity of the composite material. The volume resistivity of the inorganic filler sample (example 1) modified by the modified boron nitride and the modified carbon fiber is higher than 3.25E+1Ω & cm, so that the composite material can be obviously reduced in conductivity and enhanced in insulativity by compounding the modified boron nitride and the modified carbon fiber.
According to the analysis, the modification of the boron nitride and the carbon fiber is beneficial to reducing the contact thermal resistance and improving the volume resistivity of the composite material, and is beneficial to the application of the prepared high-heat-conductivity insulating epoxy resin composite material to the fields requiring heat conduction such as heat exchangers in chemical industry and the fields requiring heat conduction and insulation such as LED illumination and electronic packaging.
In conclusion, the invention effectively overcomes the defects in the prior art and has high industrial utilization value. The above-described embodiments are provided to illustrate the gist of the present invention, but are not intended to limit the scope of the present invention. It will be understood by those skilled in the art that various modifications and equivalent substitutions may be made to the technical solution of the present invention without departing from the spirit and scope of the technical solution of the present invention.
Claims (7)
1. The high-heat-conductivity insulating epoxy resin composite material is characterized by being mainly prepared from the following raw material components in mass: 100g of epoxy resin, 25g of curing agent, 17.65g of modified boron nitride and 11.11g of modified carbon fiber; the modified boron nitride is prepared by modifying hexagonal boron nitride by a silane coupling agent; the modified carbon fiber is prepared by modifying carbon fiber with polydopamine; the preparation steps of the modified carbon fiber specifically comprise: preparing a dopamine hydrochloride solution by using a Tris buffer solution, adding carbon fibers into the dopamine hydrochloride solution, uniformly dispersing, stirring and reacting for 6-24 hours at 50 ℃ to obtain a reaction product A, washing and centrifuging the reaction product A, and drying to obtain modified carbon fibers; the mass ratio of the carbon fiber to the dopamine hydrochloride is 1:0.8-10; the concentration of the dopamine hydrochloride solution is 0.25g/L; the carbon fiber is any one of polyacrylonitrile-based carbon fiber and asphalt-based carbon fiber.
2. The high thermal conductivity insulating epoxy resin composite material according to claim 1, wherein the preparation steps of the modified boron nitride specifically include: adding boron nitride into the hydrolyzed silane coupling agent solution, uniformly dispersing, heating to 91-95 ℃, stirring and reacting for 6-8 h, washing and drying to obtain modified boron nitride; the addition amount of the silane coupling agent is 1-15% of the mass of the boron nitride.
3. The high thermal conductivity insulating epoxy resin composite according to claim 2, wherein the silane coupling agent is at least one of KH-550, KH-560, KH-792.
4. The high thermal conductivity insulating epoxy resin composite according to claim 3, wherein the epoxy resin is any one of bisphenol a type epoxy resins E12, E31, E51; the curing agent is any one of adducts of isophorone diamine, tetraethylene pentamine, diethylenetriamine and butyl glycidyl ether.
5. The high thermal conductivity insulating epoxy resin composite of claim 4, wherein the raw material composition further comprises a diluent, the diluent being 10g; the diluent is any one of absolute ethyl alcohol, acetone and dibutyl phthalate.
6. A method for preparing the high thermal conductivity insulating epoxy resin composite material according to any one of claims 1 to 5, comprising the steps of:
(1) Weighing the raw material components according to the mass of claims 1-5, mixing modified boron nitride and modified carbon fiber, and uniformly stirring to obtain a modified mixture;
(2) Sequentially adding epoxy resin and a curing agent into the modified mixture obtained in the step (1), and stirring and dispersing to obtain mixed slurry;
(3) Injecting the mixed slurry obtained in the step (2) into a mold, and heating and curing in stages to obtain the high-heat-conductivity insulating epoxy resin composite material;
the preparation steps of the modified carbon fiber specifically comprise: preparing a dopamine hydrochloride solution by using a Tris buffer solution, adding carbon fibers into the dopamine hydrochloride solution, uniformly dispersing, stirring and reacting for 6-24 hours at 50 ℃ to obtain a reaction product A, washing and centrifuging the reaction product A, and drying to obtain modified carbon fibers; the mass ratio of the carbon fiber to the dopamine hydrochloride is 1:0.8-10; the concentration of the dopamine hydrochloride solution is 0.25g/L.
7. The method for preparing the high-heat-conductivity insulating epoxy resin composite material according to claim 6, wherein the specific steps of heating and curing in stages in the step (3) are as follows: curing for 4h in an oven at 30 ℃, and then heating to 80 ℃ for further curing for 4h.
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