CN113061321B - Composite material and preparation method thereof - Google Patents
Composite material and preparation method thereof Download PDFInfo
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- CN113061321B CN113061321B CN202110330913.XA CN202110330913A CN113061321B CN 113061321 B CN113061321 B CN 113061321B CN 202110330913 A CN202110330913 A CN 202110330913A CN 113061321 B CN113061321 B CN 113061321B
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L63/00—Compositions of epoxy resins; Compositions of derivatives of epoxy resins
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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
- C08K2003/382—Boron-containing compounds and nitrogen
- C08K2003/385—Binary compounds of nitrogen with boron
Abstract
The invention relates to a composite material and a preparation method thereof. The composite material comprises the following components in percentage by mass: 5 to 50 percent of inorganic heat-conducting filler; 0.1 to 2 percent of quaternary ammonium salt modified cellulose; 25 to 50 percent of epoxy resin; 15 to 45 percent of curing agent; 0.1 to 1.5 percent of accelerant. The quaternary ammonium salt modified cellulose has positive charges, the inorganic heat-conducting filler has negative charges, and the inorganic heat-conducting filler is adsorbed by electrostatic action and is uniformly and firmly connected in a fiber network to obtain the framework of the composite material. Under the action of curing agent and accelerator, the epoxy resin is cross-linked and cured into a net-shaped three-dimensional polymer, and the skeleton containing inorganic heat-conducting filler is enveloped in a net-shaped body, so that the composite material has high heat conductivity and high insulation.
Description
Technical Field
The invention relates to the technical field of polymer composite materials, in particular to an epoxy resin-based composite material and a preparation method thereof.
Background
The epoxy resin has hydroxyl and epoxy groups in structure, high chemical activity and wide application. The high-thermal conductivity high-performance heat dissipation film has the advantages of high mechanical property, strong adhesive force, good manufacturability, excellent electrical insulation performance and the like, is commonly used for packaging power electronic transformers, but has low thermal conductivity (about 0.2W/(m.K)), and is far from meeting the requirement of heat dissipation of devices.
With the development of power electronic technology, equipment develops towards miniaturization, high frequency and high power, a power electronic transformer can accumulate a large amount of heat in the operation process, and if the heat cannot be effectively dissipated, the service life of the equipment can be greatly shortened. How to improve the thermal conductivity of the epoxy resin packaging material and ensure the excellent insulating property of the epoxy resin packaging material under high frequency is a very important subject faced by the packaging and heat dissipation of the power electronic transformer at present.
Compared with the intrinsic heat-conducting composite material, the filled heat-conducting composite material has the advantages of simple process and low cost, and is widely researched and practically applied. The high heat-conducting filler is directly added into the epoxy resin matrix, when the filling amount reaches a critical value, the fillers are mutually contacted, the heat conduction of the composite material can be greatly improved, and the method can conveniently and quickly enhance the heat conductivity coefficient of the polymer.
As is well known, power electronic transformers are characterized by two aspects, namely high voltage and high insulation requirements on packaging materials; on the other hand, the high frequency is increased, so that the heating problem of the power electronic transformer is more serious, the aging of the power electronic transformer is accelerated, the insulation performance of the material is adversely affected, the composite packaging material is easy to generate thermal breakdown, and the service life of equipment is affected. In some researches, metal materials (such as gold, silver, copper and the like) and carbon materials (such as graphite, carbon fibers and the like) are used as heat conducting fillers, so that the heat conductivity of the epoxy resin can be greatly improved, but the insulating property of the epoxy resin is remarkably reduced due to the use of the metal materials and the carbon materials, and the epoxy resin is not suitable for packaging of power electronic transformers. Second, in general, the greater the loading of the thermally conductive filler, the greater the thermal conductivity of the composite. However, when the amount of the additive is large, the casting property is deteriorated, which is disadvantageous in processing and molding of the composite material. How to simultaneously realize that the epoxy resin-based composite material has high heat conduction and high insulation performance under the condition of low filler filling amount is a problem which needs to be solved urgently by researchers.
Disclosure of Invention
Based on the epoxy resin matrix composite material, the epoxy resin matrix composite material has high heat conductivity and high insulation.
The technical scheme is as follows:
a composite material comprising, in mass percent:
in one embodiment, the composite material comprises, by mass:
in one embodiment, the composite material comprises, by mass:
in one embodiment, the content of the quaternary ammonium salt in the quaternary ammonium salt modified cellulose is 0.7mmol/g to 1.3 mmol/g.
In one embodiment, the quaternary ammonium salt is epoxy quaternary ammonium salt. Preferably, the quaternary ammonium salt is 2, 3-epoxypropyltrimethylammonium chloride.
In one embodiment, the inorganic heat conductive filler is selected from at least one of boron nitride, aluminum oxide, and silicon dioxide.
In one embodiment, the epoxy resin is selected from at least one of bisphenol a type epoxy resin and bisphenol F type epoxy resin.
In one embodiment, the curing agent is at least one selected from the group consisting of methyl tetrahydrophthalic anhydride and methyl hexahydrophthalic anhydride.
In one embodiment, the accelerator is selected from at least one of 2-ethyl-4-methylimidazole and N, N-dimethylbenzylamine.
The invention also provides a preparation method of the composite material, which comprises the following steps:
mixing the inorganic heat-conducting filler, quaternary ammonium salt modified cellulose and water to prepare a mixture A;
carrying out ice template treatment on the mixture A to prepare a network heat-conducting framework with a directional arrangement structure;
mixing the epoxy resin, the curing agent and the accelerator to prepare a mixture B;
and mixing the network heat conduction framework with the oriented arrangement structure with the mixture B, and sequentially carrying out vacuum defoaming treatment and curing treatment.
In one embodiment, during the freezing process of the ice template treatment, the adopted refrigerant is selected from liquid nitrogen, dry ice or solid ethanol; in the freeze-drying process of the ice template treatment, the vacuum degree is less than 10Pa, the temperature is less than-50 ℃, and the time is more than 48 h.
In one embodiment, the time of the vacuum defoaming treatment is 1 h-48 h, and the vacuum degree is less than 133 Pa.
In one embodiment, the curing treatment comprises pre-curing treatment and secondary curing treatment, wherein the temperature of the pre-curing treatment is 90-110 ℃, and the time is 1.5-3 h; the temperature of the secondary curing treatment is 130-160 ℃, and the time is 8-15 h.
Compared with the prior art, the invention has the following beneficial effects:
the preparation raw materials of the epoxy resin-based composite material mainly comprise specific amounts of inorganic heat-conducting filler, quaternary ammonium salt modified cellulose, epoxy resin, a curing agent and an accelerator. The quaternary ammonium salt modified cellulose has positive charges, the surface of the inorganic heat-conducting filler has negative charges due to the hydroxyl groups and other groups, and the inorganic heat-conducting filler is adsorbed by electrostatic action and is uniformly and firmly connected in a fiber network to obtain the framework of the composite material. Under the action of curing agent and accelerator, the epoxy resin is cross-linked and cured into a net-shaped three-dimensional polymer, and the skeleton containing inorganic heat-conducting filler is enveloped in a net-shaped body, so that the composite material has high heat conductivity and high insulation.
Tests prove that the thermal conductivity of the epoxy resin-based composite material is greater than 0.3W/(m.K), the breakdown field strength under power frequency can be kept about 95% of that of pure epoxy resin, the breakdown time under 44kHz high frequency (voltage amplitude of 13kV) can reach 79.97s, and the breakdown time is improved by more than 3 times compared with that of pure epoxy resin (18.85 s). Therefore, the epoxy resin-based composite material provided by the invention also improves the thermal conductivity and the high-frequency breakdown characteristic under the condition of maintaining the power frequency insulating property.
According to the preparation method of the epoxy resin-based composite material, provided by the invention, the inorganic heat-conducting filler is sequenced by using an ice template method (freezing and freeze-drying), so that the inorganic heat-conducting filler and the quaternary ammonium salt modified fiber form a three-dimensional network heat-conducting framework together, and then the three-dimensional network heat-conducting framework is compounded with the epoxy resin to prepare the high-heat-conductivity and high-insulation composite material.
Drawings
FIG. 1 is a schematic diagram of an apparatus for freezing treatment in an embodiment of the present invention;
FIG. 2 is a SEM image of a network thermal skeleton with an oriented structure according to example 1 of the present invention;
FIG. 3 is an infrared thermal imaging graph of the epoxy resin-based composite material prepared in example 2 of the present invention and the pure epoxy resin of comparative example 1 under the voltage conditions of 44kHz frequency and 3.8kV amplitude.
Detailed Description
The present invention will be described in further detail with reference to specific examples. The present invention may be embodied in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.
Where the terms "comprising," "having," and "including" are used herein, it is intended to cover a non-exclusive inclusion, as another element may be added, unless an explicit limitation is used, such as "only," "consisting of … …," etc.
Unless mentioned to the contrary, terms in the singular may include the plural and are not to be construed as being one in number.
Furthermore, the drawings are not 1: 1 and the relative dimensions of the various elements in the figures are drawn for illustrative purposes only to facilitate understanding of the invention and are not necessarily drawn to scale, and are not to scale.
Specifically, the technical scheme of the invention is as follows:
The technical scheme is as follows:
a matrix composite comprising, in mass percent:
the preparation raw materials of the epoxy resin-based composite material mainly comprise specific amounts of inorganic heat-conducting filler, quaternary ammonium salt modified cellulose, epoxy resin, a curing agent and an accelerator. The quaternary ammonium salt modified cellulose has positive charges, the surface of the inorganic heat-conducting filler has negative charges due to the hydroxyl groups and other groups, and the inorganic heat-conducting filler is adsorbed by electrostatic action and is uniformly and firmly connected in a fiber network to obtain the framework of the composite material. Under the action of curing agent and accelerator, the epoxy resin is cross-linked and cured into a net-shaped three-dimensional polymer, and the skeleton containing inorganic heat-conducting filler is enveloped in a net-shaped body, so that the composite material has high heat conductivity and high insulation. In addition, by varying the content of each raw material, the thermal conductivity and insulation properties, and the ductility of the composite material can be synergistically controlled.
In one preferred embodiment, the composite material comprises, by mass:
further, the composite material comprises the following components in percentage by mass:
in one embodiment, the content of the quaternary ammonium salt in the quaternary ammonium salt modified cellulose is 0.7mmol/g to 1.3 mmol/g. The quaternary ammonium salt modified cellulose is selected, so that the inorganic heat-conducting filler and the quaternary ammonium salt modified cellulose can be firmly adsorbed together through electrostatic interaction, and the phenomenon that the heat conductivity of the composite material is not obviously improved or a three-dimensional heat-conducting framework network collapses after freeze-drying due to too much or too little cation content can be avoided.
In one embodiment, the inorganic thermally conductive filler is selected from at least one of Boron Nitride (BN), aluminum nitride, alumina, and silica. The inorganic heat-conducting filler has excellent thermal stability and chemical stability, high mechanical strength and high heat conductivity, and is more favorable for improving the heat conductivity of the epoxy resin-based composite material. Preferably, the present invention uses boron nitride as the inorganic heat conductive filler, including but not limited to micron boron nitride and boron nitride nanosheets, and further preferably boron nitride with a particle size of 1 μm to 15 μm, such as 10 μm of boron nitride available from dendong rijin technologies ltd.
In one embodiment, the epoxy resin is selected from at least one of bisphenol a type epoxy resin and bisphenol F type epoxy resin. The epoxy resin has excellent insulating property and is easy to obtain raw materials. The epoxy resin used in the present invention is available from the Hansen Hexion, model 828 EL.
In one embodiment, the curing agent is at least one selected from the group consisting of methyl tetrahydrophthalic anhydride and methyl hexahydrophthalic anhydride. The curing agent is more beneficial to the crosslinking and curing of the epoxy resin and improves the insulating property.
In one embodiment, the accelerator is selected from at least one of 2-ethyl-4-methylimidazole and N, N-dimethylbenzylamine.
The invention also provides a preparation method of the composite material, which comprises the following steps:
mixing the inorganic heat-conducting filler, quaternary ammonium salt modified cellulose and water to prepare a mixture A;
carrying out ice template treatment on the mixture A to prepare a network heat-conducting framework with a directional arrangement structure;
mixing the epoxy resin, the curing agent and the accelerator to prepare a mixture B;
and mixing the network heat conduction framework with the oriented arrangement structure with the mixture B, and sequentially carrying out vacuum defoaming treatment and curing treatment.
The quaternary ammonium salt modified cellulose has charges, can be uniformly and firmly connected in a fiber network through electrostatic adsorption of the inorganic heat-conducting filler, and the inorganic heat-conducting filler is sequenced by using an ice template method (freezing and freeze-drying), so that the inorganic heat-conducting filler and the quaternary ammonium salt modified fiber form a three-dimensional network heat-conducting framework together. And then mixing (soaking or pouring) the three-dimensional network heat-conducting framework and epoxy resin, under the action of a curing agent and an accelerant, crosslinking and curing the epoxy resin into a net-shaped three-dimensional polymer, and enveloping the framework containing the inorganic heat-conducting filler in a net-shaped body to prepare the high-heat-conducting and high-insulation composite material.
Preferably, in the present invention, the freezing process is performed using an apparatus as shown in FIG. 1. The device comprises a heat insulation container, a copper plate and a polytetrafluoroethylene grinding tool. The copper plate is arranged in the heat insulation container, a certain amount of refrigerant is contained in the heat insulation container, the lower end of the copper plate is in contact with the refrigerant, and the upper end of the copper plate is connected with the polytetrafluoroethylene grinding tool. The polytetrafluoroethylene grinding tool is used for containing a mixture A (mixed liquid of inorganic heat-conducting filler, quaternary ammonium salt modified cellulose and water), a certain temperature gradient is formed through a copper plate, and the mixture A is gradually frozen from bottom to top until the mixture A is completely frozen and is orderly arranged.
In one embodiment, the freezing process uses a refrigerant selected from liquid nitrogen, dry ice or solid ethanol. Preferably, the present invention employs liquid nitrogen as the refrigerant.
Freezing to obtain ice crystals, freeze-drying the ice crystals in a freeze dryer to remove water in the ice crystals to obtain the network heat-conducting skeleton with the three-dimensional arrangement structure. The three-dimensional network heat-conducting framework is prepared in advance, and the problems that the viscosity of epoxy resin is increased and the ductility is poor when inorganic filler is directly added into the epoxy resin are solved. It can be understood that if matching with grinding tools of different shapes, three-dimensional network heat-conducting frameworks of different shapes can be prepared, and then the three-dimensional network heat-conducting framework is subjected to vacuum casting by using a mixture of epoxy resin, a curing agent and an accelerator which are prepared according to a certain proportion, so that the corresponding epoxy resin-based composite material can be prepared. In addition, high heat conduction can be realized under the condition of lower filling amount of the filler by preparing the three-dimensional network heat conduction framework in advance.
In one embodiment, the vacuum degree of the freeze-drying treatment is less than 10Pa, the temperature is < -50 ℃, and the time is more than 48 h.
In one embodiment, the epoxy resin, the curing agent and the accelerator are mixed according to the mass ratio of 100: (50-110): (0.5-5), stirring, and pre-vacuumizing for 20min at normal temperature to obtain an uncured mixture B.
In one embodiment, the time of the vacuum defoaming treatment is 1 h-48 h, and the vacuum degree is less than 133 Pa.
In one embodiment, the curing treatment comprises pre-curing treatment and secondary curing treatment, wherein the temperature of the pre-curing treatment is 90-110 ℃, and the time is 1.5-3 h; the temperature of the secondary curing treatment is 130-160 ℃, and the time is 8-15 h. The segmented curing is beneficial to preventing implosion caused by excessive polymerization heat from influencing normal intermolecular crosslinking.
The following is a further description with reference to specific examples and comparative examples.
The quaternary ammonium salt modified cellulose used in the following examples and comparative examples was purchased from xylem biotechnology limited of Tianjin; 10 μm boron nitride was purchased from dendong rijin technologies ltd; bisphenol a type epoxy resin is the 828EL type by Hexion.
Example 1
The embodiment provides an epoxy resin-based composite material and a preparation method thereof.
(1) 2g of 10 μm BN was added to 10g of an aqueous solution of quaternary ammonium salt-modified cellulose, and the mixture was stirred for 10 minutes to obtain a uniformly mixed mixture A. The concentration of the quaternary ammonium salt modified cellulose in the aqueous solution of the quaternary ammonium salt modified cellulose is 0.6 wt%, and the cation content is 0.6 mmol/g.
(2) And pouring the mixture A into a polytetrafluoroethylene grinding tool, connecting the polytetrafluoroethylene grinding tool with a copper plate, immersing the lower end of the copper plate into liquid nitrogen, transferring the sample into a freeze dryer after the mixture A is completely frozen (the working parameter is that the vacuum degree is less than 5Pa, the temperature is-56 ℃), freeze-drying for 48 hours, and taking out to obtain the network heat-conducting framework with the oriented arrangement structure. Fig. 2 is an SEM image of the network thermal skeleton in the present embodiment, and it can be seen from fig. 2 that BN is arranged in a vertical direction.
(3) Bisphenol A epoxy resin methyl tetrahydrophthalic anhydride and N, N-dimethylbenzylamine are mixed according to the mass ratio of 100:86:2, and after stirring, pre-vacuum is performed for 20min at normal temperature to obtain an uncured mixture B.
(4) And (3) soaking the network heat-conducting framework prepared in the step (2) in the mixture B prepared in the step (3), defoaming in vacuum for 20h, carrying out pre-curing treatment for 2h at 100 ℃, and carrying out secondary curing treatment for 10h at 150 ℃ to prepare the high-heat-conducting and high-insulation epoxy resin-based composite material with the mass sum of BN and quaternary ammonium salt modified cellulose accounting for 16.8%.
The test shows that the thermal conductivity is 0.55W/(m.K), the breakdown field strength at power frequency is 41.67kV/mm, the breakdown field strength is 5.72 percent lower than that of pure epoxy resin (44.20kV/mm), and the breakdown time (44.90s) of the epoxy resin is improved by 137 percent compared with that of the pure epoxy resin (18.85s) under the high frequency of 44kHz (the voltage amplitude is 13 kV).
Example 2
The embodiment provides an epoxy resin-based composite material and a preparation method thereof.
(1) 4g of 10 μm BN was added to 10g of an aqueous solution of quaternary ammonium salt-modified cellulose, and the mixture was stirred for 10 minutes to obtain a uniformly mixed mixture A. The concentration of the quaternary ammonium salt modified cellulose in the aqueous solution of the quaternary ammonium salt modified cellulose is 0.6 wt%, and the cation content is 0.6 mmol/g.
(2) And pouring the mixture A into a polytetrafluoroethylene grinding tool, connecting the polytetrafluoroethylene grinding tool with a copper plate, immersing the lower end of the copper plate into liquid nitrogen, transferring the sample into a freeze dryer after the mixture A is completely frozen (the working parameter is that the vacuum degree is less than 5Pa, the temperature is-56 ℃), freeze-drying for 48 hours, and taking out to obtain the network heat-conducting framework with the oriented arrangement structure.
(3) Mixing bisphenol A type epoxy resin, methyl tetrahydrophthalic anhydride and N, N-dimethylbenzylamine according to the mass ratio of 100:86:2, stirring, and pre-vacuumizing for 20min at normal temperature to obtain an uncured mixture B.
(4) And (3) soaking the network heat-conducting framework prepared in the step (2) in the mixture B prepared in the step (3), defoaming in vacuum for 20h, carrying out pre-curing treatment for 2h at 100 ℃, and carrying out secondary curing treatment for 10h at 150 ℃ to prepare the high-heat-conducting and high-insulation epoxy resin-based composite material with the total mass of BN and quaternary ammonium salt modified cellulose accounting for 30.1%.
The test shows that the thermal conductivity is 1.19W/(m.K), the breakdown field strength at power frequency is 41.84kV/mm, the breakdown field strength is 5.34% lower than that of pure epoxy resin (44.20kV/mm), and the breakdown time (79.97s) of the epoxy resin is improved by 324% under 44kHz high frequency (voltage amplitude of 13kV) compared with that of the pure epoxy resin (18.85 s).
Fig. 3 is an infrared thermal imaging graph of the epoxy resin-based composite material prepared in the embodiment and pure epoxy resin (sample thickness is 0.3mm, and is sandwiched between the ball plate electrodes) under the voltage conditions of the frequency of 44kHz and the amplitude of 3.8kV, and it can be seen that the epoxy resin-based composite material prepared in the embodiment can effectively reduce the temperature of the epoxy resin by 28 ℃ compared with the pure epoxy resin.
Example 3
The embodiment provides an epoxy resin-based composite material and a preparation method thereof.
(1) 1g of 10 μm BN was added to 10g of an aqueous solution of quaternary ammonium salt-modified cellulose, and the mixture was stirred for 10 minutes to obtain a uniformly mixed mixture A. The concentration of the quaternary ammonium salt modified cellulose in the aqueous solution of the quaternary ammonium salt modified cellulose is 0.6 wt%, and the cation content is 0.6 mmol/g.
(2) And pouring the mixture A into a polytetrafluoroethylene grinding tool, connecting the polytetrafluoroethylene grinding tool with a copper plate, immersing the lower end of the copper plate into liquid nitrogen, transferring the sample into a freeze dryer after the mixture A is completely frozen (the working parameter is that the vacuum degree is less than 5Pa, the temperature is-56 ℃), freeze-drying for 48 hours, and taking out to obtain the network heat-conducting framework with the oriented arrangement structure.
(3) Mixing bisphenol A type epoxy resin, methyl tetrahydrophthalic anhydride and N, N-dimethylbenzylamine according to the mass ratio of 100:86:2, stirring, and pre-vacuumizing for 20min at normal temperature to obtain an uncured mixture B.
(4) And (3) soaking the network heat-conducting framework prepared in the step (2) in the mixture B prepared in the step (3), defoaming in vacuum for 20h, carrying out pre-curing treatment for 2h at 100 ℃, and carrying out secondary curing treatment for 10h at 150 ℃ to prepare the high-heat-conducting and high-insulation epoxy resin-based composite material with the mass sum of BN and quaternary ammonium salt modified cellulose accounting for 9.2%.
The test shows that the thermal conductivity is 0.32W/(m.K), the breakdown field strength at power frequency is 42.42kV/mm, the breakdown field strength is 4.03 percent lower than that of pure epoxy resin (44.20kV/mm), and the breakdown time (27.56s) of the epoxy resin is improved by 46 percent compared with that of the pure epoxy resin (18.85s) under the high frequency of 44kHz (voltage amplitude of 13 kV).
Example 4
The embodiment provides an epoxy resin-based composite material and a preparation method thereof.
(1) 3g of 10 μm BN was added to 10g of an aqueous solution of quaternary ammonium salt-modified cellulose, and the mixture was stirred for 10 minutes to obtain a uniformly mixed mixture A. The concentration of the quaternary ammonium salt modified cellulose in the aqueous solution of the quaternary ammonium salt modified cellulose is 0.6 wt%, and the cation content is 0.6 mmol/g.
(2) And pouring the mixture A into a polytetrafluoroethylene grinding tool, connecting the polytetrafluoroethylene grinding tool with a copper plate, immersing the lower end of the copper plate into liquid nitrogen, transferring the sample into a freeze dryer after the mixture A is completely frozen (the working parameter is that the vacuum degree is less than 5Pa, the temperature is-56 ℃), freeze-drying for 48 hours, and taking out to obtain the network heat-conducting framework with the oriented arrangement structure.
(3) Mixing bisphenol A type epoxy resin, methyl tetrahydrophthalic anhydride and N, N-dimethylbenzylamine according to the mass ratio of 100:86:2, stirring, and pre-vacuumizing for 20min at normal temperature to obtain an uncured mixture B.
(4) And (3) soaking the network heat-conducting framework prepared in the step (2) in the mixture B prepared in the step (3), defoaming in vacuum for 20h, carrying out pre-curing treatment for 2h at 100 ℃, and carrying out secondary curing treatment for 10h at 150 ℃ to prepare the high-heat-conducting and high-insulation epoxy resin-based composite material with the mass sum of BN and quaternary ammonium salt modified cellulose accounting for 23.5%.
The test shows that the thermal conductivity is 0.82W/(m.K), the breakdown field strength at power frequency is 41.13kV/mm, the breakdown field strength is 6.95 percent lower than that of pure epoxy resin (44.20kV/mm), and the breakdown time (55.92s) of the epoxy resin is improved by 197 percent compared with that of the pure epoxy resin (18.85s) under the high frequency of 44kHz (voltage amplitude of 13 kV).
Comparative example 1
This comparative example provides an epoxy resin and a method of making the same.
(1) Preparing epoxy resin: bisphenol A type epoxy resin, methyl tetrahydrophthalic anhydride and N, N-dimethylbenzylamine in a mass ratio of 100: 86: 2, stirring, and pre-vacuumizing for 8 hours at normal temperature to obtain a mixture A.
(2) And (3) carrying out pre-curing treatment on the mixture A for 2h at the temperature of 100 ℃, and then carrying out secondary curing treatment for 10h at the temperature of 150 ℃ to obtain the pure epoxy resin.
The test shows that the thermal conductivity is 0.14W/(m.K), the breakdown field strength at power frequency is 44.20kV/mm, and the breakdown time at 44kHz high frequency (voltage amplitude is 13kV) is 18.85 s.
The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.
The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.
Claims (10)
1. The composite material is characterized by comprising the following raw materials in percentage by mass:
the content of quaternary ammonium salt in the quaternary ammonium salt modified cellulose is 0.6 mmol/g; the quaternary ammonium salt is epoxy quaternary ammonium salt; in the composite material, the quaternary ammonium salt modified cellulose adsorbs the inorganic heat-conducting filler through electrostatic action, the inorganic heat-conducting filler is connected in fiber grids of the quaternary ammonium salt modified cellulose to serve as a framework of the composite material, the epoxy resin is crosslinked and cured into a net-shaped three-dimensional polymer under the action of the curing agent and the accelerator, and the net-shaped three-dimensional polymer envelops the framework.
2. The composite material according to claim 1, characterized in that the raw materials are, in mass percent:
3. Composite material according to claim 1 or 2, characterized in that said quaternary ammonium salt is 2, 3-epoxypropyltrimethylammonium chloride.
4. The composite material of claim 3, wherein the inorganic thermally conductive filler is selected from at least one of boron nitride, aluminum nitride, alumina, and silica.
5. The composite material according to claim 4, wherein the epoxy resin is selected from at least one of bisphenol A type epoxy resin and bisphenol F type epoxy resin.
6. The composite material of claim 5, wherein the curing agent is selected from at least one of methyl tetrahydrophthalic anhydride and methyl hexahydrophthalic anhydride; and/or
The accelerator is at least one selected from 2-ethyl-4-methylimidazole and N, N-dimethylbenzylamine.
7. A method for preparing a composite material according to any one of claims 1 to 6, characterized in that it comprises the following steps:
mixing the inorganic heat-conducting filler, quaternary ammonium salt modified cellulose and water to prepare a mixture A;
carrying out ice template treatment on the mixture A to prepare a network heat-conducting framework with a directional arrangement structure;
mixing the epoxy resin, the curing agent and the accelerator to prepare a mixture B;
And mixing the network heat conduction framework with the directional arrangement structure with the mixture B, and sequentially carrying out vacuum defoaming treatment and curing treatment.
8. The method for preparing the composite material according to claim 7, wherein in the freezing process of the ice template treatment, the adopted refrigerant is selected from liquid nitrogen, dry ice or solid ethanol; in the freeze-drying process of the ice template treatment, the vacuum degree is less than 10Pa, the temperature is less than-50 ℃, and the time is more than 48 h.
9. The method for preparing the composite material according to claim 7, wherein the time of the vacuum defoaming treatment is 1h to 48h, and the vacuum degree is less than 133 Pa.
10. The preparation method of the composite material according to claim 9, wherein the curing treatment comprises a pre-curing treatment and a secondary curing treatment, the temperature of the pre-curing treatment is 90-110 ℃, and the time is 1.5-3 h; the temperature of the secondary curing treatment is 130-160 ℃, and the time is 8-15 h.
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| JPS562341A (en) * | 1979-06-20 | 1981-01-12 | Matsushita Electric Works Ltd | Epoxy resin casting material |
| CN106700427A (en) * | 2016-12-30 | 2017-05-24 | 深圳先进技术研究院 | Boron nitride/epoxy resin composite material and preparation method thereof |
| CN107189348A (en) * | 2017-05-11 | 2017-09-22 | 华中科技大学 | A kind of epoxy resin heat conduction composite and its preparation and application |
| CN108690324A (en) * | 2017-04-11 | 2018-10-23 | 深圳市圳田科技有限公司 | A kind of micro-nano composite insulating material of high-thermal-conductivity epoxy resin base alumina-boron nitride |
| CN111909490A (en) * | 2020-08-17 | 2020-11-10 | 清华大学 | Epoxy resin composite material and preparation method thereof |
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2021
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Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS562341A (en) * | 1979-06-20 | 1981-01-12 | Matsushita Electric Works Ltd | Epoxy resin casting material |
| CN106700427A (en) * | 2016-12-30 | 2017-05-24 | 深圳先进技术研究院 | Boron nitride/epoxy resin composite material and preparation method thereof |
| CN108690324A (en) * | 2017-04-11 | 2018-10-23 | 深圳市圳田科技有限公司 | A kind of micro-nano composite insulating material of high-thermal-conductivity epoxy resin base alumina-boron nitride |
| CN107189348A (en) * | 2017-05-11 | 2017-09-22 | 华中科技大学 | A kind of epoxy resin heat conduction composite and its preparation and application |
| CN111909490A (en) * | 2020-08-17 | 2020-11-10 | 清华大学 | Epoxy resin composite material and preparation method thereof |
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