阅读说明：本技术 一种邻苯二甲腈基复合材料及其制备方法和应用 (Phthalonitrile-based composite material and preparation method and application thereof ) 是由 周恒� 郭颖 赵彤 刘先渊 刘翔 于 2020-05-11 设计创作，主要内容包括：本发明公开了一种邻苯二甲腈基复合材料及其制备方法和应用。所述复合材料由邻苯二甲腈树脂和氧化铝@石墨复合粒子组成。氧化铝@石墨复合粒子具有核壳结构,其壳层为氧化铝,核为石墨颗粒,氧化铝包覆在所述石墨颗粒的表层。将所得复合粒子作为导热填料,利用热压工艺使复合粒子与邻苯二甲腈树脂基体紧密结合制备兼具导热和绝缘性能的邻苯二甲腈复合材料。该复合材料具有热导率高、电绝缘、耐高温、力学性能好等优点。(The invention discloses a phthalonitrile-based composite material and a preparation method and application thereof. The composite material consists of phthalonitrile resin and alumina @ graphite composite particles. The aluminum oxide @ graphite composite particle has a core-shell structure, wherein a shell layer is made of aluminum oxide, a core is made of graphite particles, and the surface layers of the graphite particles are coated with the aluminum oxide. The obtained composite particles are used as heat-conducting filler, and the composite particles are tightly combined with a phthalonitrile resin matrix by utilizing a hot-pressing process to prepare the phthalonitrile composite material with heat conduction and insulating properties. The composite material has the advantages of high thermal conductivity, electric insulation, high temperature resistance, good mechanical property and the like.)

1. The aluminum oxide @ graphite composite material is characterized by having a core-shell structure, wherein a shell layer is made of aluminum oxide, a core is made of graphite particles, and the surface layers of the graphite particles are coated with the aluminum oxide.

2. The alumina @ graphite composite of claim 1, wherein the alumina completely coats the surface layer of the graphite particles;

preferably, the coating is a uniform coating;

preferably, the graphite particles are micron-sized;

preferably, the mass percentage of the alumina shell layer in the alumina @ graphite composite material is 5-50%;

preferably, the alumina @ graphite composite has a TEM topography substantially as shown in figure 2.

3. The method of making the alumina @ graphite composite of claim 1 or 2, wherein the method of making comprises the steps of:

(1) dispersing graphite and an anionic surfactant in deionized water to enable the anionic surfactant to completely cover the graphite to obtain a stable and uniform mixed solution;

(2) simultaneously dripping an aluminum salt solution and an alkali liquor into the mixed solution, reacting under the stirring condition, filtering to obtain a precipitate after the reaction is finished, and performing post-treatment on the precipitate to obtain powder;

(3) and calcining the powder to obtain the alumina @ graphite composite material.

4. The method according to claim 3, wherein the anionic surfactant is at least one of sodium dodecyl sulfonate, sodium dodecyl sulfate, and secondary sodium alkyl sulfonate;

preferably, the aluminum salt is at least one of aluminum nitrate, aluminum sulfate, or a hydrate thereof;

preferably, the base is at least one of sodium hydroxide, potassium hydroxide, sodium bicarbonate and potassium bicarbonate.

5. The production method according to claim 3 or 4, wherein in the step (1), the dispersion is ultrasonic dispersion;

preferably, the using amount of the anionic surfactant is 0.5-30% of the mass of the graphite;

preferably, the mass volume ratio of the graphite to the deionized water is 1g (15-50) mL.

Preferably, in the step (2), the mass ratio of the aluminum salt to the graphite is 1: 0.1-10; preferably, the molar ratio of base to aluminum salt is (2.7-3.3): 1; preferably, the volume ratio of the aluminum salt solution to the mixed solution and the volume ratio of the alkali solution to the mixed solution are the same or different, and are 1 (5-30); preferably, the aluminum salt solution and the alkali liquor are slowly added into the mixed solution in a dropwise manner under the stirring condition; preferably, after the aluminum salt solution and the alkali liquor are dripped, stirring and reacting for 2-4 h.

Preferably, in the step (3), the temperature of the calcination is 400-800 ℃; preferably, the calcination time is 1 to 12 hours.

6. A phthalonitrile-based composite comprising the alumina @ graphite composite of claim 1 or 2.

Preferably, the mass percentage of the alumina @ graphite composite material in the phthalonitrile-based composite material is 5-50%.

Preferably, the alumina @ graphite composite material is uniformly distributed in a phthalonitrile matrix;

preferably, the alumina @ graphite composite material is tightly combined with a phthalonitrile matrix, and the porosity is lower than 2.5%;

preferably, the alumina @ graphite composite material is mutually overlapped in a phthalonitrile matrix to form a heat conduction channel.

Preferably, the phthalonitrile-based composite material has a profile substantially as shown in fig. 4.

7. The composite material according to claim 6, wherein the raw materials for preparing the phthalonitrile-based composite material comprise, in parts by weight: 100 parts of phthalonitrile monomer, 1-10 parts of curing agent and 5-50 parts of alumina @ graphite composite material;

preferably, the phthalonitrile monomer is selected from compounds having a structure shown in formula (1):

wherein R is selected from any one of the following structures:

preferably, R is selected from any one of the following structures:

illustratively, R is selected from any one of the following structures:

preferably, the phthalonitrile monomer is selected from compounds having a structure represented by formula (2) or formula (3):

preferably, the curing agent is an amine curing agent;

preferably, the phthalonitrile-based composite material is prepared from the raw materials in parts by weight.

Preferably, the thermal conductivity coefficient of the phthalonitrile-based composite material is 0.2-0.7 W.m^-1·K^-1。

Preferably, the volume of the phthalonitrile-based composite materialResistivity of not less than 10¹⁰Ω·cm。

Preferably, the glass transition temperature of the phthalonitrile-based composite material is 450-465 ℃.

8. The method for producing a phthalonitrile-based composite material as claimed in claim 6 or 7, characterized in that it comprises the following steps: prepared from a feedstock comprising the alumina @ graphite composite material of claim 1 or 2. Preferably, the blend containing the phthalonitrile monomer of claim 7, the curing agent and the alumina @ graphite composite is obtained by a hot pressing reaction.

9. The method of claim 8, comprising the steps of:

(1) uniformly mixing the alumina @ graphite composite material with a phthalonitrile monomer and a curing agent by adopting a melt blending method;

(2) and (2) pouring the mixture obtained in the step (1) into a mold, carrying out primary normal-pressure pre-curing, pressure curing, cooling, demolding and then carrying out normal-pressure post-curing to obtain the phthalonitrile-based composite material.

Preferably, the alumina @ graphite composite, the curing agent and the phthalonitrile monomer have the meaning and amounts as stated in claim 6.

Preferably, in the step (2), the temperature of the atmospheric pre-curing is 150-230 ℃; preferably, the time of the atmospheric pre-curing is 0.5-2.5 h;

preferably, the press curing is a staged press curing; for example, the pressure curing stages are 2-4, and the temperature of each stage of the pressure curing is preferably 230-300 ℃; preferably, the temperature of each stage of curing is increased from stage to stage; preferably, the pressure of the pressure curing is 5-15 MPa.

Preferably, in step (2), the atmospheric postcure is postcured in stages, for example in 2 to 4 stages. Preferably, the temperature of each stage of the normal-pressure post-curing is 300-400 ℃; preferably, the temperature of each stage of curing is increased from stage to stage.

10. The use of the phthalonitrile based composite material according to claim 6 or 7 in the field of thermal conduction and insulation; preferably, the composite material is used for electrical components.

Technical Field

The invention belongs to the field of polymer composite materials, and particularly relates to a phthalonitrile-based composite material as well as a preparation method and application thereof.

Background

In the 5G era, electronic appliances, automated intelligent equipment and the like have been developed in the directions of high power, high density and high integration, and the heat dissipation problem of devices caused by the development is increasingly prominent. If the accumulated heat is not transferred to the surrounding environment in time, the performance and the service life of the device can be seriously influenced, and the heat-conducting composite material is produced at the same time. The ideal packaging material should have good heat conduction and insulation performance, and for some electrical components with long-term high heat productivity, higher service temperature also puts higher requirements on the heat resistance of the material.

The phthalonitrile resin as a high molecular polymer has the advantages of high glass transition temperature (more than 450 ℃), excellent heat resistance, low water absorption, good flame retardance, good mechanical property and the like, and is widely applied to the fields of aerospace, ships, machinery and electronic materials. However, the low thermal conductivity of phthalonitrile resin severely limits the application of phthalonitrile resin in the electronic field. At present, inorganic ceramic fillers are generally added into polymers to prepare heat-conducting and insulating polymer-based composite materials, but the economic effect of the inorganic ceramic fillers is influenced by the high cost of the ceramic fillers, so that the development of a novel filler with excellent performance and low cost is urgently needed.

The carbon material graphite has the obvious advantages of low cost, high heat conductivity, high temperature resistance, low thermal expansion coefficient, small density, stable chemical property and the like. The graphite with a lamellar structure is considered to be a suitable filler for preparing the heat-conducting polymer composite material, but the heat-conducting polymer composite material has reduced insulating property. How to ensure that the heat conductivity and the insulativity of the polymer-based composite material can be considered after the filler is added becomes a technical problem to be solved urgently.

Disclosure of Invention

The invention provides an alumina @ graphite composite material which has a core-shell structure, wherein a shell layer is made of alumina, a core is made of graphite particles, and the surface layer of the graphite particles is coated with the alumina.

According to an embodiment of the present invention, the alumina entirely coats the surface layer of the graphite particles.

According to an embodiment of the invention, the graphite particles are in the micron size range; for example, the graphite particles have a particle size of 0.15 to 50 μm, for example 0.5 to 20 μm.

According to an embodiment of the present invention, the mass percentage of the alumina shell layer to the alumina @ graphite composite material is 5 to 50%, preferably 10 to 30%, and exemplary is 9.07%, 10%, 15%, 18.37%, 20%, 24%, 25%, 30%.

According to an embodiment of the present invention, the alumina @ graphite composite has a TEM topography substantially as shown in figure 2.

The invention also provides a preparation method of the alumina @ graphite composite material, which comprises the following steps:

(1) dispersing graphite and an anionic surfactant in deionized water to enable the anionic surfactant to completely cover the graphite to obtain a stable and uniform mixed solution;

(2) dropwise adding an aluminum salt solution and an alkali liquor into the mixed solution obtained in the step (1) at the same time, reacting under a stirring condition, filtering to obtain a precipitate after the reaction is finished, and performing post-treatment on the precipitate to obtain powder;

(3) and (3) calcining the powder obtained in the step (2) to obtain the alumina @ graphite composite material.

According to an embodiment of the invention, the graphite has the meaning as described above.

According to an embodiment of the present invention, the anionic surfactant is at least one of sodium dodecyl sulfonate, sodium dodecyl sulfate, secondary sodium alkyl sulfonate, preferably sodium dodecyl sulfate and/or sodium dodecyl sulfate.

According to an embodiment of the present invention, the aluminum salt is at least one of aluminum nitrate, aluminum sulfate, or a hydrate thereof, for example, aluminum nitrate nonahydrate and/or aluminum sulfate octadecahydrate.

According to an embodiment of the invention, the base is at least one of sodium hydroxide, potassium hydroxide, sodium bicarbonate and potassium bicarbonate, for example sodium hydroxide and/or potassium hydroxide.

According to an embodiment of the invention, in step (1), the dispersion is ultrasonic dispersion. For example, the power of the ultrasonic wave is 80-120W, preferably 90-110W, and exemplary is 80W, 90W, 100W, 110W and 120W. For example, the time of the ultrasound is 10min to 60min, preferably 20 to 40min, and exemplarily 20min, 30min, and 40 min. For example, the ultrasound temperature is 70 to 90 ℃, preferably 75 to 85 ℃, exemplary 70 ℃, 75 ℃, 80 ℃, 85 ℃, 90 ℃.

According to an embodiment of the present invention, in the step (1), the amount of the anionic surfactant is 0.5 to 30% by mass, preferably 2 to 7% by mass, and is exemplified by 2%, 3%, 4%, 5%, 6%, 7% by mass of the graphite.

According to an embodiment of the invention, in step (1), the mass-to-volume ratio of graphite to deionized water is 1g (15-50) mL, such as 1g (20-40) mL, exemplary 1g:20mL, 1g:30mL, 1g:40mL, 1g:50 mL.

According to an embodiment of the present invention, in the step (2), the mass ratio of the aluminum salt to the graphite is 1:0.1 to 10, preferably 1:0.5 to 2, and exemplarily 1:0.64, 1:0.75, 1:1, 1:1.5, 1: 2.

According to an embodiment of the present invention, in step (2), the molar ratio of base to aluminium salt is (2.7-3.3):1, preferably (2.9-3.1):1, exemplarily 3: 1.

According to the embodiment of the invention, in the step (2), the volume ratio of the aluminum salt solution to the mixed solution and the volume ratio of the alkali solution to the mixed solution are the same or different, and are, for example, 1 (5-30), preferably 1 (10-20), and exemplarily 1:10, 1:15, and 1: 20.

According to the embodiment of the present invention, in the step (2), the aluminum salt solution and the alkali solution are slowly added dropwise to the mixed solution under stirring. For example, the dropping time is not more than 2 hours, for example, 1 to 2 hours. Further, in the dropping process, the pH value of the system is kept between 6 and 7.

According to an embodiment of the present invention, in step (2), after the aluminum salt solution and the alkali solution are added dropwise, the reaction is stirred for 2 to 4 hours, such as 2 to 3 hours, for example, 2 hours, 2.5 hours, and 3 hours.

According to an embodiment of the present invention, in the step (2), the post-treatment includes washing and drying. For example, the precipitate is washed at least 2 times with ethanol. For example, the washed precipitate is dried under vacuum; further, the temperature of the vacuum drying is 90-110 ℃, preferably 95-105 ℃, exemplary 90 ℃, 100 ℃, 110 ℃; further, the vacuum drying time is 8-16h, preferably 10-14h, and exemplary 10h and 12 h.

According to the embodiment of the present invention, in the step (3), the temperature of the calcination is 400-. For example, the calcination time is 1 to 12 hours, preferably 2 to 5 hours, and exemplarily 2 hours, 3 hours, 4 hours, 5 hours.

According to an embodiment of the present invention, in the step (3), the calcination is performed in a tube furnace.

According to an exemplary embodiment of the present invention, the preparation method of the alumina @ graphite composite material comprises the following steps:

(1) ultrasonically dispersing graphite and an anionic surfactant in deionized water to enable the anionic surfactant to completely cover the graphite to obtain a stable and uniform mixed solution;

(2) slowly dripping an aluminum salt solution and an alkali liquor into the mixed solution under the stirring condition, keeping the pH of the system to be 6-7 in the dripping process, reacting under the stirring condition after finishing dripping, filtering to obtain a precipitate after finishing the reaction, and performing post-treatment on the precipitate to obtain powder;

(3) and calcining the powder to obtain the alumina @ graphite composite material.

In preparation, the aluminum salt provides aluminum ions and the base provides hydroxide ions to the solution. After the anionic surfactant is dissolved in the deionized water, the alkyl end of the anionic surfactant is combined with the graphite, and the anion at the other end is combined with the aluminum ions in the solution; and simultaneously, generating aluminum hydroxide by aluminum ions and hydroxide radicals in the solution to obtain composite particles of aluminum hydroxide coated graphite, and calcining at high temperature to obtain the aluminum oxide @ graphite composite material.

The invention also provides the alumina @ graphite composite material prepared by the method.

The invention also provides application of the alumina @ graphite composite material as a heat-conducting filler. Preferably as a heat conductive filler of the phthalonitrile-based resin.

The invention also provides a phthalonitrile-based composite material which contains the alumina @ graphite composite material. For example, the alumina @ graphite composite may comprise 5 to 50% by mass of the phthalonitrile-based composite, such as 10 to 30%, illustratively 5%, 10%, 15%, 20%, 25%, 30%.

According to an embodiment of the present invention, the alumina @ graphite composite is uniformly distributed in the phthalonitrile matrix resin. Preferably, the alumina @ graphite composite is tightly bound to the phthalonitrile matrix resin with a porosity of less than 2.5%.

According to an embodiment of the present invention, the alumina @ graphite composite material is overlapped with each other in the phthalonitrile matrix resin to form a heat conducting channel.

According to an embodiment of the present invention, the phthalonitrile-based composite material has a profile substantially as shown in fig. 4.

According to the embodiment of the invention, the raw materials for preparing the phthalonitrile-based composite material comprise the following components in parts by weight: 100 parts of phthalonitrile monomer, 1-10 parts of curing agent and 5-50 parts of alumina @ graphite composite material;

the alumina @ graphite composite has the meaning as described above.

According to an embodiment of the present invention, the phthalonitrile monomer is selected from compounds having a structure represented by formula (1):

wherein R is selected from any one of the following structures:

preferably, R is selected from any one of the following structures:

illustratively, R is selected from any one of the following structures:

according to an embodiment of the present invention, the phthalonitrile monomer is selected from compounds having a structure represented by formula (2) or formula (3):

according to an embodiment of the present invention, the curing agent is an amine-based curing agent, and may be, for example, at least one of 4, 4-diaminodiphenyl sulfone, 4 '-diaminodiphenyl sulfone, 4-amino- (3, 4-dicyanophenyloxy) benzene, m-aminophenylacetylene, and 4, 4' -biphenyldiamine; illustrative is 4-amino- (3, 4-dicyanophenoxy) benzene.

According to an embodiment of the present invention, the curing agent is used in an amount of 2 to 8 parts, illustratively 2 parts, 3 parts, 4 parts, 5 parts, 6 parts, 7 parts, 8 parts.

According to an embodiment of the present invention, the alumina @ graphite composite is used in an amount of 10 to 30 parts, illustratively 11 parts, 11.625 parts, 12 parts, 15 parts, 18 parts, 18.5 parts, 20 parts, 25 parts, 26.25 parts, 30 parts.

According to the embodiment of the invention, the phthalonitrile-based composite material is prepared from the raw materials in parts by weight.

According to the inventionAccording to the scheme, the thermal conductivity coefficient of the phthalonitrile-based composite material is 0.2-0.7 W.m^-1·K^-1. Preferably, the thermal conductivity coefficient of the phthalonitrile-based composite material is 0.3-0.68 W.m^-1·K^-1。

According to an embodiment of the present invention, the volume resistivity of the phthalonitrile-based composite material is not less than 10¹⁰Ω · cm, preferably not less than 10¹¹Ω·cm。

According to an embodiment of the present invention, the glass transition temperature of the phthalonitrile-based composite material is 450-.

The invention also provides a preparation method of the phthalonitrile-based composite material, which comprises the following steps: the composite material is prepared from the raw materials containing the alumina @ graphite composite material. Preferably, the composite material is obtained by hot-pressing a blend containing the phthalonitrile monomer, the curing agent and the alumina @ graphite composite material.

According to an embodiment of the invention, the preparation method comprises the steps of:

(1) uniformly mixing the alumina @ graphite composite material with a phthalonitrile monomer and a curing agent by adopting a melt blending method;

(2) and (2) pouring the mixture obtained in the step (1) into a mold, carrying out primary normal-pressure pre-curing, pressure curing, cooling, demolding and then carrying out normal-pressure post-curing to obtain the phthalonitrile-based composite material.

According to an embodiment of the present invention, the alumina @ graphite composite, the curing agent and the phthalonitrile monomer have the meanings and amounts as described above.

According to an embodiment of the present invention, in step (1), the melt blending temperature is determined according to the phthalonitrile monomer used. Wherein the blending time is 20min-40min, such as 20min, 25min, 30min, 35min, 40 min.

According to the embodiment of the invention, in the step (2), the temperature of the atmospheric pre-curing is 150-. Wherein the time of the atmospheric pre-curing is 0.5-2.5h, preferably 1-2h, and is exemplified by 1h, 1.5h and 2 h.

According to an embodiment of the present invention, in the step (2), the press curing is a press curing performed in stages; for example, the number of press-curing stages is 2 to 4, preferably 2 to 3. Wherein the temperature of each stage of the pressure curing is 230-300 ℃, preferably 230-280 ℃, and exemplarily 230 ℃, 250 ℃ and 280 ℃. Preferably, the temperature of each stage of curing is increased from stage to stage. Wherein the stage times of the press curing are the same or different, for example 1 to 3.5h, preferably 1.5 to 3h, exemplary 1h, 1.5h, 2h, 2.5h, 3h, 3.5 h.

According to an embodiment of the present invention, in the step (2), the pressure of the pressure curing is 5 to 15MPa, preferably 8 to 12MPa, and exemplary pressure is 8MPa, 10MPa, 12 MPa.

According to an embodiment of the present invention, in the step (2), the cooling is natural cooling to room temperature.

According to an embodiment of the present invention, in step (2), the atmospheric postcure may be postcured in stages, for example in 2 to 4 stages. Wherein the temperature of each stage of the normal-pressure post-curing is 300-400 ℃, preferably 315-375 ℃, and exemplarily 315 ℃, 330 ℃, 350 ℃ and 375 ℃. Preferably, the temperature of each stage of curing is increased from stage to stage. Wherein, the time of each stage of the normal pressure post-curing is the same or different and is selected from 4 to 6 hours, such as 4 hours, 4.5 hours, 5 hours, 5.5 hours and 6 hours. Illustratively, under normal pressure, the post cure is carried out for 5h at 315 ℃ and 5h at 375 ℃.

The invention also provides the phthalonitrile-based composite material prepared by the method.

The invention also provides the application of the phthalonitrile-based composite material in the field of heat conduction and insulation; preferably, the composite material is used for electrical components.

The invention has the beneficial effects that:

(1) the invention provides an alumina @ graphite shell-core composite material as a filler of a phthalonitrile-based composite material, which is different from an inorganic ceramic filler with high cost and a metal filler which is easy to corrode and conduct electricity. The aluminum oxide @ graphite shell-core composite material is coated with an aluminum oxide insulating layer on the surface of graphite, has the remarkable advantages of low cost, high thermal conductivity, high temperature resistance, low thermal expansion coefficient, low density, stable chemical property and the like of carbon material graphite, can construct a heat conducting network in a phthalonitrile resin matrix, improves the thermal conductivity of the phthalonitrile composite material, maintains high volume resistivity of the composite material, and meets the insulation requirement.

(2) The preparation method of the alumina @ graphite shell-core composite material provided by the invention can control the content of alumina by adjusting the proportion of the raw materials, and has the advantages of mild reaction conditions and simple and controllable process. The prepared alumina @ graphite core-shell composite material is high in yield, low in cost and good in performance.

(3) The invention provides a heat-conducting insulating phthalonitrile-based composite material and a preparation method thereof, wherein the phthalonitrile-based composite material has good heat conductivity and insulating property, and can well solve the problems of heat dissipation, electric insulation and heat resistance of high-power electric appliances when being applied to electric appliance elements.

Drawings

Fig. 1 is a Transmission Electron Microscope (TEM) image of graphite.

Fig. 2 is a Transmission Electron Microscope (TEM) image of the alumina @ graphite core-shell composite particles prepared in preparation example 1.

Fig. 3 is a thermogravimetric analysis (TGA) graph of the alumina @ graphite core-shell composite particles and graphite prepared in preparation 1 and preparation 2 under an air atmosphere.

Fig. 4 is a Scanning Electron Microscope (SEM) cross-section view of the alumina @ graphite core-shell composite particle filled phthalonitrile-based composite prepared in example 3.

Detailed Description

The technical solution of the present invention will be further described in detail with reference to specific embodiments. It is to be understood that the following examples are only illustrative and explanatory of the present invention and should not be construed as limiting the scope of the present invention. All the technologies realized based on the above-mentioned contents of the present invention are covered in the protection scope of the present invention.

Unless otherwise indicated, the raw materials and reagents used in the following examples are all commercially available products or can be prepared by known methods.

Preparation example 1

The alumina @ graphite shell-core composite particle is prepared by the following steps:

(1) dispersing 10g of graphite and 0.4g of sodium dodecyl sulfate in 300ml of deionized water, and carrying out ultrasonic treatment in an ultrasonic cleaning machine at 80 ℃ and 100w of power for 0.5 hour to obtain a stable and uniform mixed solution;

(2) the mixture was mechanically stirred at 80 ℃ for 2 hours, and 15.0g of aluminum nitrate nonahydrate and 4.8g of sodium hydroxide were weighed to prepare 20ml of aqueous solutions, and then added dropwise to the mixture while keeping the pH at 6-7. And continuously reacting for 2 hours under the stirring condition, performing suction filtration, washing filter residues with ethanol for 3-5 times, and transferring to a vacuum oven at 100 ℃ for drying for 12 hours to obtain the aluminum hydroxide @ graphite particles. And calcining the aluminum hydroxide @ graphite particles in a 600 ℃ tubular furnace for 3 hours to obtain the product aluminum oxide @ graphite shell-core composite particles.

Fig. 1 is a Transmission Electron Microscope (TEM) image of graphite, and fig. 2 is a Transmission Electron Microscope (TEM) image of the prepared alumina @ graphite core-shell composite particles. As can be seen by comparison, the aluminum oxide is successfully coated on the surface layer of the graphite, and the aluminum oxide @ graphite shell-core composite particle is successfully prepared.

Fig. 3 is a thermogravimetric analysis (TGA) of the prepared alumina @ graphite core-shell composite particles in an air atmosphere, from which it can be obtained that the mass percentage of the alumina shell layer in the alumina @ graphite core-shell composite particles is 18.37%.

Preparation example 2

The alumina @ graphite shell-core composite particle is prepared by the following steps:

(1) dispersing 10g of graphite and 0.4g of sodium dodecyl sulfate in 300ml of deionized water, and carrying out ultrasonic treatment in an ultrasonic cleaning machine at 80 ℃ and 100w of power for 0.5 hour to obtain a stable and uniform mixed solution;

(2) the mixture was mechanically stirred at 80 ℃ for 2 hours, and 7.5g of aluminum nitrate nonahydrate and 2.4g of sodium hydroxide were weighed to prepare 20ml of aqueous solutions, and then added dropwise to the mixture while keeping the pH at 6-7. And continuously reacting for 2 hours under the stirring condition, performing suction filtration, washing filter residues with ethanol for 3-5 times, and transferring to a vacuum oven at 100 ℃ for drying for 12 hours to obtain the aluminum hydroxide @ graphite particles. And calcining the aluminum hydroxide @ graphite particles in a 600 ℃ tubular furnace for 3 hours to obtain the product aluminum oxide @ graphite shell-core composite particles.

Fig. 3 is a thermogravimetric analysis (TGA) of the prepared alumina @ graphite core-shell composite particles in an air atmosphere, from which it can be obtained that the mass percentage of the alumina shell layer in the alumina @ graphite core-shell composite particles is 9.07%.

Preparation example 3

The alumina @ graphite shell-core composite particle is prepared by the following steps:

(1) dispersing 10g of graphite and 0.4g of sodium dodecyl sulfate in 300ml of deionized water, and carrying out ultrasonic treatment in an ultrasonic cleaning machine at 80 ℃ and 100w of power for 0.5 hour to obtain a stable and uniform mixed solution;

(2) the mixture was mechanically stirred at 80 ℃ for 2 hours, and 20g of aluminum nitrate nonahydrate and 6.4g of sodium hydroxide were weighed to prepare 20ml of aqueous solutions, and then added dropwise to the mixture while keeping the pH at 6-7. And continuously reacting for 2 hours under the stirring condition, performing suction filtration, washing filter residues with ethanol for 3-5 times, and transferring to a vacuum oven at 100 ℃ for drying for 12 hours to obtain the aluminum hydroxide @ graphite particles. And calcining the aluminum hydroxide @ graphite particles in a 600 ℃ tubular furnace for 3 hours to obtain the product aluminum oxide @ graphite shell-core composite particles. The mass percentage of the alumina shell layer in the alumina @ graphite core-shell composite particle is about 24%.

Example 1

In the embodiment, the heat-conducting and insulating phthalonitrile-based composite material (the alumina @ graphite shell-core composite particles account for about 5% of the mass of the composite material) is prepared by the following method:

weighing 8.0g of phthalonitrile monomer (shown in formula (2)) and heating for melting, adding 0.4g of curing agent 4-amino- (3, 4-dicyano phenoxy) benzene, mechanically stirring uniformly, then adding 0.44g of alumina @ graphite shell-core composite particles prepared in preparation example 1, and mechanically stirring uniformly for 20 minutes to obtain a mixture.

The mixture was poured into a preheated mold and pre-cured at 200 ℃ for 1 hour at atmospheric pressure. Then curing the mixture for 2 hours at 230 ℃, 2 hours at 250 ℃ and 2 hours at 280 ℃ under the pressure of 10 MPa. Naturally cooling to room temperature, demoulding, and curing at 315 ℃ for 5 hours and 375 ℃ for 5 hours under normal pressure to obtain the heat-conducting and insulating phthalonitrile-based composite material.

Example 2

In the embodiment, the heat-conducting and insulating phthalonitrile-based composite material (the alumina @ graphite shell-core composite particles account for about 10% of the mass of the composite material) is prepared by the following method:

weighing 8.0g of phthalonitrile monomer (shown in formula (2)) and heating for melting, adding 0.4g of curing agent 4-amino- (3, 4-dicyano phenoxy) benzene, mechanically stirring uniformly, then adding 0.93g of alumina @ graphite shell-core composite particles prepared in preparation example 1, and mechanically stirring uniformly for 20 minutes to obtain a mixture.

The mixture was poured into a preheated mold and pre-cured at 200 ℃ for 1 hour at atmospheric pressure. Then curing the mixture for 2 hours at 230 ℃, 2 hours at 250 ℃ and 2 hours at 280 ℃ under the pressure of 10 MPa. Naturally cooling to room temperature, demoulding, and curing at 315 ℃ for 5 hours and 375 ℃ for 5 hours under normal pressure to obtain the heat-conducting and insulating phthalonitrile-based composite material.

Example 3

In the embodiment, the heat-conducting and insulating phthalonitrile-based composite material (the alumina @ graphite shell-core composite particles account for about 15% of the mass of the composite material) is prepared by the following method:

weighing 8.0g of phthalonitrile monomer (shown in formula (3)) and heating for melting, adding 0.4g of curing agent 4-amino- (3, 4-dicyano phenoxy) benzene, mechanically stirring uniformly, then adding 1.48g of alumina @ graphite composite particles prepared in preparation example 1, and mechanically stirring uniformly for 20 minutes to obtain a mixture.

The mixture was poured into a preheated mold and pre-cured at 200 ℃ for 1 hour at atmospheric pressure. Then curing the mixture for 2 hours at 230 ℃, 2 hours at 250 ℃ and 2 hours at 280 ℃ under the pressure of 10 MPa. Naturally cooling to room temperature, demoulding, and curing at 315 ℃ for 5 hours and 375 ℃ for 5 hours under normal pressure to obtain the heat-conducting and insulating phthalonitrile-based composite material.

Fig. 4 is a Scanning Electron Microscope (SEM) cross-sectional view of the phthalonitrile composite prepared, and it can be seen that: the alumina @ graphite shell-core composite particles are uniformly distributed in the resin and are free from agglomeration. In addition, the hot pressing process enables the alumina @ graphite particles to be tightly combined with phthalonitrile, and no obvious holes exist (the porosity is lower than 2.5%). Good interface adhesion can effectively transfer heat between particles and resin, and reduce interface thermal resistance. The aluminum oxide @ graphite particles are mutually overlapped, and a corresponding heat conduction channel is effectively constructed.

Example 4

In the embodiment, the heat-conducting and insulating phthalonitrile-based composite material (the alumina @ graphite shell-core composite particles account for about 20% of the mass of the composite material) is prepared by the following method:

weighing 8.0g of phthalonitrile monomer (shown in formula (3)) and heating for melting, adding 0.4g of curing agent 4-amino- (3, 4-dicyano phenoxy) benzene, mechanically stirring uniformly, then adding 2.1g of alumina @ graphite shell-core composite particles prepared in preparation example 1, and mechanically stirring uniformly for 20 minutes to obtain a mixture.

The mixture was poured into a preheated mold and pre-cured at 200 ℃ for 1 hour at atmospheric pressure. Then curing the mixture for 2 hours at 230 ℃, 2 hours at 250 ℃ and 2 hours at 280 ℃ under the pressure of 10 MPa. Naturally cooling to room temperature, demoulding, and curing at 315 ℃ for 5 hours and 375 ℃ for 5 hours under normal pressure to obtain the heat-conducting and insulating phthalonitrile-based composite material.

Comparative example 1

No filler was added. 8.0g of phthalonitrile monomer (shown in formula (2)) is weighed, heated and melted, 0.4g of curing agent 4-amino- (3, 4-dicyano phenoxy) benzene is added, and mechanical stirring is carried out for 20 minutes until uniformity is achieved.

The mixture was poured into a preheated mold and pre-cured at 200 ℃ for 1 hour at atmospheric pressure. Then curing the mixture for 2 hours at 230 ℃, 2 hours at 250 ℃ and 2 hours at 280 ℃ under the pressure of 10 MPa. Naturally cooling to room temperature, demolding, curing at 315 deg.C for 5 hr and at 375 deg.C for 5 hr under normal pressure to obtain phthalonitrile resin.

Comparative example 2

Weighing 8.0g of phthalonitrile monomer (shown as a formula (2)) and heating for melting, adding 0.4g of curing agent 4-amino- (3, 4-dicyano phenoxy) benzene, mechanically stirring uniformly, then adding 0.44g of graphite (the graphite accounts for about 5% of the mass of the composite material), and mechanically stirring for 20 minutes until uniform to obtain a mixture.

The mixture was poured into a preheated mold and pre-cured at 200 ℃ for 1 hour at atmospheric pressure. Then curing the mixture for 2 hours at 230 ℃, 2 hours at 250 ℃ and 2 hours at 280 ℃ under the pressure of 10 MPa. Naturally cooling to room temperature, demoulding, and curing at 315 ℃ for 5 hours and 375 ℃ for 5 hours under normal pressure to obtain the phthalonitrile-based composite material.

Comparative example 3

Weighing 8.0g of phthalonitrile monomer (shown in formula (3)) and heating for melting, adding 0.4g of curing agent 4-amino- (3, 4-dicyano phenoxy) benzene, mechanically stirring uniformly, then adding 1.48g of graphite (the graphite accounts for about 15% of the mass of the composite material), and mechanically stirring for 20 minutes until uniform to obtain a mixture.

The mixture was poured into a preheated mold and pre-cured at 200 ℃ for 1 hour at atmospheric pressure. Then curing the mixture for 2 hours at 230 ℃, 2 hours at 250 ℃ and 2 hours at 280 ℃ under the pressure of 10 MPa. Naturally cooling to room temperature, demolding, curing at 315 ℃ for 5 hours and at 375 ℃ for 5 hours under normal pressure to obtain the phthalonitrile composite material.

The phthalonitrile-based composite materials prepared in the above examples and comparative examples were tested by the following test methods, and the specific test results are shown in table 1.

(1) Thermal conductivity test

The thermal conductivity of the composite material is tested by a transient plane heat source method (Hot Disk).

(2) Volume resistivity test

The volume resistivity of the composite material was measured at a voltage of 500V using a digital high resistance meter model PC 68.

(3) Dynamic Mechanical Analysis (DMA)

The glass transition temperature of the composite material is tested by using Netzsch 242c, the test temperature is 25-500 ℃, the test frequency is 1Hz, and nitrogen is used as shielding gas.

TABLE 1 Properties of phthalonitrile based composites prepared in examples and comparative examples

According to table 1, the comparison between examples 1 to 4 and comparative example 1 can conclude that, as the content of the alumina @ graphite composite particles increases, the heat-conducting fillers are mutually overlapped to form a heat-conducting network, so that the heat conductivity coefficient of the composite material is effectively improved, and heat can be better transferred. The volume resistivity of the corresponding composite material decreases slightly, but still remains at a high level.

According to the comparison among the comparative example 1, the comparative example 2 and the comparative example 3 in the table 1, the conclusion can be drawn that the heat conductivity coefficient and the electric conductivity of the composite material filled with the untreated graphite are both obviously improved, and the composite material is applied to the field of heat and electric conduction of polymer matrix composite materials. However, the high conductivity of untreated graphite does not meet the insulation requirements.

From table 1, comparing example 1 with comparative example 2, it can be seen that the thermal conductivity of the alumina @ graphite particle filled composite is comparable to that of the untreated graphite filled composite at the same level, but the volume resistivity is several orders of magnitude higher. The aluminum oxide and graphite are compounded, so that the high heat-conducting property of the carbon material graphite and the insulating property of the aluminum oxide are combined, and a good effect is obtained.

From Table 1, it can be concluded that the glass transition temperature of the composites filled with alumina @ graphite particles fluctuates between 455 ℃ and 460 ℃ as compared to that of the pure phthalonitrile resin, and that the glass transition temperature of the composites filled with alumina @ graphite particles is still very high (Tg >450 ℃). Therefore, the phthalonitrile composite material filled with the alumina @ graphite particles has good heat resistance.

In conclusion, the alumina @ graphite composite particle prepared by the simple and feasible method has high yield, low cost and good performance, and the composite material prepared by blending the alumina @ graphite composite particle serving as the heat-conducting filler and the phthalonitrile resin has high heat conductivity, and meanwhile, the material still keeps good electrical insulation and heat resistance. The invention provides a new idea for the application of the carbon material in the field of heat conduction and insulation of composite materials.

The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiment. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.