CN113788986A

CN113788986A - Modified graphite-based functional filler, thermal interface material and preparation method thereof

Info

Publication number: CN113788986A
Application number: CN202111041627.8A
Authority: CN
Inventors: 汪怀远; 高越阳; 朱艳吉; 崔业翔; 徐飞
Original assignee: Tianjin University
Current assignee: Tianjin University
Priority date: 2021-09-07
Filing date: 2021-09-07
Publication date: 2021-12-14
Anticipated expiration: 2041-09-07
Also published as: CN113788986B

Abstract

The invention discloses a modified graphite-based functional filler, a thermal interface material and a preparation method thereof, wherein the modified graphite-based functional filler comprises vermicular expanded graphite, and the surface of the vermicular expanded graphite is provided with a chemically active plating layer; the chemical active coating is used for introducing active groups to improve the polarity of the vermicular expanded graphite; the thermal interface material comprises the modified graphite-based functional filler and liquid rubber; the problem that the application of the existing thermal interface material is limited because the multiple coupling balance of the flexibility characteristic, the heat conduction performance and the electromagnetic shielding effect cannot be achieved is solved.

Description

Modified graphite-based functional filler, thermal interface material and preparation method thereof

Technical Field

The disclosure relates to a functional material for heat management, in particular to a functional filler, a thermal interface material using the functional filler and a preparation method thereof.

Background

Due to the further development of 5G mobile communication technology and integrated circuit manufacturing process, modern electronic devices are moving toward high operating frequency and miniaturization. However, high integration coupled with high power density can accelerate the burn-in process of core electronics and cause serious problems in the field of thermal management. In addition, the complex electromagnetic waves generated by the operation of part of the rf chips not only affect the operation of the adjacent electronic modules, but also cause harm to human health, and because most of the electromagnetic shielding materials achieve the electromagnetic shielding purpose by absorbing and reflecting the electromagnetic waves and converting the electromagnetic waves into heat energy, the electromagnetic shielding materials ignore the problem of large heat accumulation generated in the process of converting the electromagnetic energy. Even if the electromagnetic shielding requirements can be met, the resulting large accumulation of heat can still pose a serious hazard to the electronic devices. Therefore, the electromagnetic shielding performance is considered, and the thermal management performance of the material is also considered, so that the material for specific application is required to have high thermal conductivity and electromagnetic shielding resistance.

Compared to conventional metal-based electromagnetic shielding materials and thermal management materials, polymer materials have attracted a great deal of attention for their processability, light weight, corrosion resistance. However, the low intrinsic thermal conductivity of the polymer (0.1-0.5W m)^-1 K^-1) And the low electromagnetic shielding effectiveness (10-20%) still limits the wide application in the fields of thermal management and electromagnetic shielding coupling to a great extent.

In the first aspect, the problem of the existing thermal management material in thermal management is that the thermal resistance of the assembly caused by the material characteristics during the assembly process of the material is also a great important factor influencing the practical effect of the material. In practical applications, when the heat sink is in direct contact with the heat source device, a large number of micro-area voids are generated due to insufficient bonding interface, and the thermal conductivity of air is very low (about 0.023W m)^-1 K^-1) And thus, non-negligible interfacial thermal resistance may be generated.

Many studies currently employ resin substrates that do not have flexibility and interfacial adhesion properties, and thus, even if some degree of thermal conductivity enhancement is achieved, the core problem of interfacial thermal resistance due to assembly in practical applications is still not solved. For example, the epoxy resin type heat conducting material does not have a flexible characteristic after being molded, so that the heat dissipation groove cannot be ensured to be fully contacted with a heat source in the assembling process, a large number of micro-area gaps cannot be effectively filled, and the actual heat management performance is finally influenced to a great extent. Therefore, it is practical to develop a flexible thermal interface material that can fill the micro-domain voids.

In the second aspect, in the aspect of electromagnetic shielding resistance, a relatively common method of the existing thermal management material is to introduce functional filler into a polymer matrix so as to improve the heat conduction performance and the electromagnetic shielding efficiency, but the problem of high interface thermal resistance cannot be effectively solved due to common mixed melting molding, and a layer-shaped filler network with developed orientation is difficult to construct so as to improve the heat transmission efficiency and the electromagnetic shielding efficiency. Therefore, there is a need to develop a flexible thermal interface material with excellent thermal conductivity and electromagnetic shielding performance to efficiently solve the multiple coupling problems of heat dissipation, high frequency electromagnetic wave pollution and practical thermal interface bonding.

In a third aspect, partial research on the functional filler used in the current thermal management material adopts processes such as a chemical vapor deposition method, a plasma vapor deposition method, an ice template method and the like to prepare the functional filler, but the processes cannot be applied in large-scale practical application due to high cost and complex process. Although some researches attempt to improve the electromagnetic shielding performance of the thermal interface material by using transition metal carbonitride (MXENE) as a functional filler, the synthesis process of high-purity transition metal carbonitride is complicated and extremely high in cost, and cannot be applied in a large amount to synergistically enhance the thermal conductivity of the thermal interface material. The thermal interface material obtained by the method has the majority of thermal conductivity lower than 20W m^-1 K^-1Meanwhile, the ideal electromagnetic shielding capability is lacked, so that the multiple requirements of light weight, high heat conduction and high electromagnetic shielding of the thermal interface material at present are difficult to meet.

In the fourth aspect, the traditional mechanical stirring and mixing method is difficult to uniformly mix the high-viscosity polymer matrix and the functional filler, the problem of filler aggregation and uneven distribution is often caused in the actual operation process, and a large number of gaps exist in the nano-micro structure in the forming process, so that the micro-area interface defect is caused, and the overall mechanical property of the material is reduced.

Therefore, the above-mentioned technical difficulties result in the failure to obtain multiple coupling balance of flexibility, thermal conductivity and electromagnetic shielding effect in the thermal interface material.

Disclosure of Invention

In view of this, the present disclosure provides a modified graphite-based functional filler and a thermal interface material using the same, which solve the problem that the application of the conventional thermal interface material is limited due to the inability to achieve multiple coupling balance among flexibility characteristics, thermal conductivity, and electromagnetic shielding efficiency.

In addition, the disclosure also provides a preparation method of the functional filler and the thermal interface material.

In a first aspect, the modified graphite-based functional filler is characterized by comprising:

the expanded graphite in the form of worms may be,

the surface of the vermicular expanded graphite is provided with a chemically active coating;

the chemically active coating is used for introducing active groups to improve the polarity of the vermicular expanded graphite.

In a second aspect, the preparation method of the modified graphite-based functional filler is characterized by comprising the following steps:

obtaining vermicular expanded graphite;

and carrying out in-situ polymerization reaction on the vermicular expanded graphite and a modifier in a biochemical buffer solution to form a chemically active coating on the surface of the vermicular expanded graphite so as to obtain the modified graphite-based functional filler.

Further, the chemically active coating is a nanoscale chemically active coating.

Further, the vermicular expanded graphite is a product of in-situ thermal expansion of crystalline flake graphite, graphite intercalation compound, graphite carbon tubes or graphite-based carbon fibers.

The vermicular expanded graphite retains van der waals' intrinsic force in the graphite structure and has a porous three-dimensional structure.

Further, the modifying agent is a coupling agent;

the biochemical buffer solution is used for mixing the modifier and the vermicular expanded graphite.

Further, the modifier comprises 4- (2-aminoethyl) -1, 2-benzenediol hydrochloride, vinylmethoxysilane or aminoethoxysilane;

the biochemical buffer solution comprises a mixed solution of tris (hydroxymethyl) aminomethane hydrochloride and ethanol, a mixed solution of isopropanol and sodium hydroxide or a mixed solution of absolute ethanol and ammonia water;

and/or the presence of a gas in the interior of the container,

the vermicular expanded graphite: the biochemical buffer solution: the mass ratio of the modifier is 1: 100-300: 0.2 to 1.5;

and/or the presence of a gas in the interior of the container,

the in-situ polymerization reaction condition is that the mechanical stirring is carried out for 12-48 h at room temperature;

the pH value of the reaction ranges from 7 to 12.

Further, after a chemically active coating is formed on the surface of the vermicular expanded graphite, the vermicular expanded graphite is washed by a detergent and then dried to obtain the final modified graphite-based functional filler.

Further, the detergent comprises deionized water, absolute ethyl alcohol or isopropanol;

and/or the presence of a gas in the interior of the container,

the drying mode is freeze drying, and the drying time is controlled to be 12-72 hours.

In a third aspect, the thermal interface material comprises:

the modified graphite-based functional filler according to the first aspect.

Further, the thermal interface material further comprises liquid rubber.

Further, the liquid rubber comprises one or a mixture of more of nitrile rubber, natural rubber, ethylene propylene rubber, butadiene rubber or styrene butadiene rubber.

In a fourth aspect, the method for preparing a thermal interface material is characterized by comprising:

the liquid rubber of the third aspect and the modified graphite-based functional filler;

and vulcanizing and adding a mixture containing the liquid rubber and the modified graphite-based functional filler to obtain the thermal interface material.

Further, the solid mass percentage of the mixture is 10-40 wt%.

Further, the method for obtaining the mixture adopts a vacuum multi-stage mixing mode.

The vacuum multi-stage mixing is implemented under the negative pressure condition, the mixture is uniformly dispersed by means of the mixing and stirring action of different gradients, micron-sized air gaps in the functional filler are cooperatively eliminated, and the rubber matrix is fully filled in the functional filler micro-area.

Further, the mixture also comprises a vulcanization accelerator and an anti-aging agent;

the vulcanization accelerator comprises sulfur or 2, 2' -dithiodibenzothiazole;

the anti-aging agent comprises 2,2, 4-trimethyl-1, 2-dihydroquinoline polymer (RD), 2-thiol benzimidazole (MB) or 6-ethoxy-2, 2, 4-trimethyl-1, 2-dihydroquinoline;

the vulcanization accelerator is: the anti-aging agent: the mass ratio of the liquid rubber is 0.5-2: 0.5-2: 100.

further, the conditions of the vulcanization addition are: pressurizing for 6-8 MPa at 120-180 ℃, maintaining the pressure for 1-3 min, and then releasing the pressure; pressurizing for the second time at 10-12 MPa, maintaining the pressure for 2-5 min, and then releasing the pressure; and pressurizing for three times at 14-18 MPa, maintaining the pressure for 4-6 min, then decompressing, cooling to normal temperature, and then demolding.

The vulcanization addition operation promotes the modified graphite-based functional filler to be directionally arranged in the rubber matrix through gradient pressure induction, so that a multilayer oriented network structure is constructed; then, the crosslinking degree between rubber chain segments is strengthened by means of the coupling of temperature and pressure, and the function of improving the overall mechanical property of the thermal interface material is achieved.

Further, the vacuum multi-stage mixing mode adopts a vacuum three-stage stirring mixing mode; wherein the vacuum degree during mixing is-90 to 100 kPa; the first-order mixing speed is 200-500 rpm, and the stirring time is 30-60 s; the rotation speed of the second-order mixing is 600-1200 rpm, and the stirring time is 60-180 s; the rotation speed of the three-stage mixing is 1500-2500 rpm, and the stirring time is 120-240 s.

Further, adding a diluent during the vacuum multi-stage mixing;

the diluent comprises one or more of dimethylbenzene, ethyl acetate, acetone or cyclohexanone;

the mass ratio of the diluent to the liquid rubber is 0.3-1.8: 1.

further, venting the mixture to volatilize the diluent prior to the performing of the vulcanization addition, the solvent volatilization process conditions being: and (4) standing for 12-72 hours at 40-70 ℃ in a ventilating manner.

The invention has the following beneficial effects:

first, the disclosed thermal interface material has high electromagnetic shielding effectiveness

1. According to the modified graphite-based functional filler disclosed by the invention, a nanoscale chemically active coating is formed on the surface of a graphite-based material with a vermicular three-dimensional structure through in-situ polymerization, active groups such as amino, hydroxyl, vinyl and catecholamine structures can be introduced into the nanoscale chemically active coating, the polarity of the vermicular expanded graphite can be improved through the introduction of the active groups, more polarization centers are formed, and more dipoles are provided through asymmetric charge distribution. The dipoles can absorb electromagnetic energy, break free and rotate, thereby enhancing the electromagnetic shielding effectiveness of the thermal interface material.

According to the preparation method of the thermal interface material, liquid rubber and the modified graphite-based functional filler are uniformly dispersed and micron-sized air gaps in the modified graphite-based functional filler are cooperatively eliminated in a vacuum multi-stage mixing mode, so that a rubber matrix is fully filled in a functional filler micro-area; and in the vulcanization operation process, gradient pressure induction is utilized to promote the modified graphite-based functional filler to be directionally arranged in the rubber matrix, a multilayer oriented network structure is constructed, multiple interfaces in unit volume are provided to promote electromagnetic waves to be subjected to multiple reflection so as to be attenuated, and the electromagnetic shielding efficiency of the thermal interface material is improved.

Secondly, the thermal interface material disclosed by the invention has high heat-conducting property

According to the thermal interface material disclosed by the invention, the liquid rubber matrix is uniformly filled in intrinsic gaps (micro-regions) of the modified graphite-based functional filler disclosed by the invention, and the nano chemically active coating of the modified graphite-based functional filler reduces the space density of the contact thermal resistance of a micro-region interface (filler-matrix) and strengthens the bridging effect of the micro-region interface.

In addition, the multilayer oriented structure formed by the oriented arrangement of the modified graphite-based functional filler in the rubber matrix promotes a developed space heat conduction path, and is beneficial to efficient diffusion and transmission of heat flow, so that the heat conduction performance of the thermal interface material is greatly improved.

The vulcanization treatment promotes the chemical bonds in the modified graphite-based functional filler to perform addition reaction with the rubber matrix chain segments, and the interface bridging effect is enhanced to form a cross-linked network so as to further improve the flexibility and the mechanical property; the optimized flexibility characteristic enables the thermal interface material to effectively fill tiny air gaps of the element interface in the application process, and the overall heat transfer effect after assembly is enhanced.

The thermal interface material disclosed by the invention has the advantages that the thermal conductivity and the electromagnetic shielding effectiveness are coupled and enhanced, meanwhile, the flexibility and the mechanical property which are lacked by most thermal interface materials are ensured, the application range of the frontier thermal management field is further widened, and the thermal interface material has application value in the traditional thermal management field and a new comprehensive thermomagnetic coupling radio frequency system; the special flexibility of the heat dissipation module ensures the sufficient contact between the heat dissipation module and the heat-generating electronic element, and greatly improves the problem of interface bonding of heat-accumulating elements in practical application; its excellent thermal conductivity exceeds many commercial thermal interface materials and even partial metal alloys; meanwhile, the electromagnetic shielding performance of over 99.9999 percent and the electromagnetic shielding value of 79.0dB are achieved, and the electromagnetic shielding performance of the electromagnetic shielding device far exceeds the electromagnetic shielding performance (99 percent) required by the current commercial standard; in addition, its electromagnetic shielding value is twice that required by some military and aerospace electronics (30 dB). The heat-conducting electromagnetic shielding device disclosed by the invention maintains excellent flexible characteristics and mechanical properties while the synergistic coupling enhancement of the heat-conducting property and the electromagnetic shielding effectiveness is realized.

Drawings

The above and other objects, features and advantages of the present disclosure will become more apparent from the following description of embodiments of the present disclosure with reference to the accompanying drawings, in which:

FIG. 1A is an HRTEM image of the graphite-based filler of example 1;

FIG. 1B is a HRTEM image of the modified graphite-based functional filler of example 2;

as can be seen from fig. 1A and 1B, after the modified graphite-based functional filler prepared by the present disclosure undergoes in-situ polymerization, a chemical plating layer with a thickness of about 3nm is formed on the surface of the graphite-based filler, the chemical affinity of the filler is improved after the active group is introduced, and the diffraction spot diagram also shows that the filler subjected to in-situ polymerization still well retains a crystal structure.

FIG. 2A is a cross-sectional SEM image of the thermal interface material of example 1;

FIG. 2B is a cross-sectional SEM image of the thermal interface material of example 2;

FIG. 2C is a high magnification SEM magnification view of a cross-section of the thermal interface material of example 2;

as can be seen in fig. 2B, the thermal interface material prepared by the present disclosure possesses excellent in-plane orientation alignment and forms a multi-layer oriented network structure. The microstructure characteristic is favorable for efficient transmission of phonons, and the modified graphite-based functional filler which is in close contact with the layers also has a nano coating to reduce interface thermal resistance and bring high heat conductivity. In addition, the multilayer oriented network structure can provide multiple interfaces in unit volume to promote multi-order reflection of electromagnetic waves so as to achieve the purpose of attenuation, a large number of active groups are introduced into a nano coating formed through in-situ polymerization reaction so as to form more polarization centers, and more dipoles are provided through asymmetric charge distribution. The dipoles can absorb electromagnetic energy, break freely and rotate, thereby enhancing electromagnetic shielding effectiveness.

As can be seen from fig. 2C, superior in-plane alignment was observed even in the high-magnification SEM image and no apparent interface defects were observed; as can be seen from fig. 2A, the graphite-based filler lacking the nano active plating layer and the rubber matrix are not sufficiently fused, and obvious cavity and interface defects appear in the prepared thermal interface material.

FIG. 3A is a graph illustrating the effect of the flexibility characteristics of the thermal interface material of example 2;

FIG. 3B is a graph comparing the flexibility characteristics and utility performance of the thermal interface material of example 2;

as can be seen from fig. 3A and 3B, the thermal interface material prepared by the method of the present disclosure has better flexibility characteristics, can be folded and bent at will, and has excellent tensile strength; can meet the requirements of the heat management field of the leading edge field, such as heat management application of wearable devices.

FIG. 4 is a graph comparing in-plane thermal conductivity and electromagnetic shielding effectiveness of comparative examples 1-2 and examples 1-2;

as can be seen from fig. 4, the thermal interface material prepared by the method of the present disclosure substantially improves the thermal conductivity while optimizing the electromagnetic shielding effectiveness.

FIG. 5 is a graph comparing mechanical properties of comparative examples 1-2 and examples 1-2;

as can be seen in fig. 5, the tensile strength of the thermal interface material prepared by the method of the present disclosure is greatly enhanced. Wherein the tensile strength of example 2 is nearly 10 times stronger than that of comparative example 1, reaching 23.3 MPa; and the elongation at break is also maintained at a good level (> 130%).

Detailed Description

The present disclosure is described below based on examples, but it is worth explaining that the present disclosure is not limited to these examples. In the following detailed description of the present disclosure, some specific details are set forth in detail. However, the present disclosure may be fully understood by those skilled in the art for those parts not described in detail.

Furthermore, those of ordinary skill in the art will appreciate that the drawings are provided solely for the purposes, features, and advantages of the present disclosure, and are not necessarily drawn to scale.

Also, unless the context clearly requires otherwise, throughout the description and the claims, the words "comprise", "comprising", and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is, the meaning of "includes but is not limited to".

Comparative example 1

Step (1): adding a proper amount of ethyl acetate into 30g of liquid nitrile rubber, 0.06g of sulfur, 0.06g of 2, 2' -dithiodibenzothiazyl and 0.06g of 2,2, 4-trimethyl-1, 2-dihydroquinoline polymer to obtain a liquid rubber mixture;

step (2): carrying out vacuum multi-stage mixing assembly on the liquid rubber mixture to obtain a homogeneous mixture; wherein the vacuum degree during mixing is-100 kPa; the rotation speed of the first-order mixing is 500rpm, and the stirring time is 45 s; the rotation speed of the second-order mixing is 1200rpm, and the stirring time is 90 s; the speed of rotation of the third mixing was 1800rpm and the stirring time was 120 s.

And (3): putting the obtained homogeneous mixture into a 60 ℃ oven for solvent volatilization for 48 hours, and removing residual ethyl acetate and volatile components to obtain cured rubber;

and (4): vulcanizing the obtained cured rubber, pressurizing at 150 ℃ for 6MPa for one time, maintaining the pressure for 2min, and then releasing the pressure; pressurizing for the second time at 10MPa, maintaining the pressure for 4min, and then releasing the pressure; and (3) pressurizing for three times at 14MPa, maintaining the pressure for 5min, then relieving the pressure, cooling to normal temperature, and then demolding to obtain the vulcanized rubber.

Comparative example 2

Step (1): 10g of liquid nitrile rubber, 0.02g of sulfur, 0.02g of 2, 2' -dithiodibenzothiazyl, 0.02g of 2,2, 4-trimethyl-1, 2-dihydroquinoline polymer and 3g of graphite compound, and adding a proper amount of ethyl acetate to obtain a liquid rubber mixture;

And (3): putting the obtained homogeneous mixture into a 60 ℃ oven for solvent volatilization for 48 hours, removing residual ethyl acetate and volatile components, and curing to obtain a composite material precursor;

and (4): vulcanizing the obtained precursor material, pressurizing for 6MPa at 160 ℃, maintaining the pressure for 2min, and then releasing the pressure; pressurizing for the second time at 10MPa, maintaining the pressure for 4min, and then releasing the pressure; and pressurizing for three times at 15MPa, maintaining the pressure for 5min, then decompressing, cooling to normal temperature, and then demolding to obtain the flexible thermal interface material.

Example 1

Step (1): rapidly carrying out in-situ thermal expansion on 5g of graphite compound at 700 ℃ for 80s to obtain porous vermicular graphite;

step (2): adding a proper amount of ethyl acetate into 10g of liquid nitrile rubber, 0.02g of sulfur, 0.02g of 2, 2' -dithiodibenzothiazyl, 0.02g of 2,2, 4-trimethyl-1, 2-dihydroquinoline polymer and 3.2g of worm graphite filler to obtain a liquid rubber mixture;

and (3): carrying out vacuum multi-stage mixing assembly on the liquid rubber mixture to obtain a homogeneous mixture; wherein the vacuum degree during mixing is-100 kPa; the rotation speed of the first-order mixing is 500rpm, and the stirring time is 45 s; the rotation speed of the second-order mixing is 1200rpm, and the stirring time is 90 s; the speed of rotation of the third mixing was 1800rpm and the stirring time was 120 s.

And (4): putting the obtained homogeneous mixture into a 60 ℃ oven for solvent volatilization for 48 hours, removing residual ethyl acetate and volatile components, and curing to obtain a composite material precursor;

and (5): vulcanizing the obtained precursor material, pressurizing for 6MPa at 160 ℃, maintaining the pressure for 2min, and then releasing the pressure; pressurizing for the second time at 12MPa, maintaining the pressure for 4min, and then releasing the pressure; and pressurizing for three times at 15MPa, maintaining the pressure for 5min, then decompressing, cooling to normal temperature, and then demolding to obtain the flexible thermal interface material.

Example 2

step (2): mixing 3.6g of porous worm graphite and 0.75g of 4- (2-aminoethyl) -1, 2-benzenediol hydrochloride in 500g of trihydroxymethyl aminomethane hydrochloride and ethanol buffer solution, and carrying out in-situ polymerization reaction for 36h at room temperature to obtain a functional filler precursor; fully washing the functional filler precursor, and freeze-drying for 48 hours to obtain the in-situ polymerization modified graphite-based functional filler;

and (3): adding a proper amount of ethyl acetate into 10g of liquid nitrile rubber, 0.02g of sulfur, 0.02g of 2, 2' -dithiodibenzothiazyl, 0.02g of 2,2, 4-trimethyl-1, 2-dihydroquinoline polymer and 3.2g of in-situ polymerization modified graphite-based functional filler to obtain a liquid rubber mixture;

and (4): carrying out vacuum multi-stage mixing assembly on the liquid rubber mixture to obtain a homogeneous mixture; wherein the vacuum degree during mixing is-100 kPa; the rotation speed of the first-order mixing is 500rpm, and the stirring time is 45 s; the rotation speed of the second-order mixing is 1200rpm, and the stirring time is 90 s; the speed of rotation of the third mixing was 1800rpm and the stirring time was 120 s.

And (5): putting the obtained homogeneous mixture into a 60 ℃ oven for solvent volatilization for 48 hours, removing residual ethyl acetate and volatile components, and curing to obtain a composite material precursor;

and (6): vulcanizing the obtained precursor material, pressurizing for 6MPa at 160 ℃, maintaining the pressure for 2min, and then releasing the pressure; pressurizing for the second time at 12MPa, maintaining the pressure for 4min, and then releasing the pressure; and pressurizing for three times at 15MPa, maintaining the pressure for 5min, then decompressing, cooling to normal temperature, and then demolding to obtain the flexible thermal interface material.

Example 3

Step (1): 5g of crystalline flake graphite and 0.75g of gamma-aminopropyltriethoxysilane are mixed in 400g of 25wt% isopropanol buffer solution to carry out in-situ polymerization reaction for 36h at room temperature to obtain a functional filler precursor; fully washing the functional filler precursor, and freeze-drying for 48 hours to obtain the in-situ polymerization modified graphite-based functional filler;

step (2): adding proper amount of dimethylbenzene into 10g of liquid rubber, 0.02g of sulfur, 0.02g of 2, 2' -dithiodibenzothiazyl, 0.02g of 2,2, 4-trimethyl-1, 2-dihydroquinoline polymer and 3.2g of in-situ polymerization modified graphite-based functional filler to obtain a liquid rubber mixture;

And (4): putting the obtained homogeneous mixture into a 60 ℃ oven for solvent volatilization for 48 hours, removing residual xylene and volatile components, and curing to obtain a composite material precursor;

Example 4

Step (1): mixing 1.8g of flake graphite, 1.8g of graphite compound, 0.72g of 4- (2-aminoethyl) -1, 2-benzenediol hydrochloride in 500g of trihydroxymethyl aminomethane hydrochloride and ethanol buffer solution, and carrying out in-situ polymerization reaction for 36h at room temperature to obtain a composite functional filler precursor; fully washing the composite functional filler precursor, and freeze-drying for 48 hours to obtain the in-situ polymerization modified graphite-based functional filler;

step (2): adding proper amount of dimethylbenzene into 10g of liquid nitrile rubber, 0.02g of sulfur, 0.02g of 2, 2' -dithiodibenzothiazyl, 0.02g of 2,2, 4-trimethyl-1, 2-dihydroquinoline polymer and 3.2g of in-situ polymerization modified graphite-based functional filler to obtain a liquid rubber mixture;

Table 1 thermal conductivity, electromagnetic shielding property and mechanical properties of comparative examples 1 to 2 and examples 1 to 2

Note: the main body thermal conductivity is measured based on the standard ISO 22007-2 by adopting a Hot Disk-TPS method; the anisotropic thermal conductivity is tested by adopting a laser flash LFA method based on the standard ISO 22007-4-2017; mechanical property testing is based on the ASTM D638 standard; the electromagnetic shielding effectiveness is tested in the frequency domain range of 8.2-12.4GHz by adopting an Agilent PNA-N5244A vector network analyzer.

As shown in table 1, examples 1 and 2 showed better overall performance than comparative examples 1 and 2; in addition, compared with the embodiment 1, the embodiment 2 has obviously improved heat-conducting property, electromagnetic shielding effectiveness and mechanical property in various aspects, and shows excellent anisotropic heat-conducting property.

Example 2 excellent thermal conductivity also far exceeded current commercial thermal interface material levels (5-10W m)^-1 K^-1) (ii) a The excellent electromagnetic shielding performance exceeds the current commercial standard electromagnetic shielding value by 20dB and is twice as high as the required value of 30dB of partial military and aerospace electronic equipment. The heat conducting performance and the electromagnetic shielding effectiveness are efficiently balanced, and meanwhile, the better mechanical property is kept, so that the application range is widened for more heat management examples.

The bulk thermal conductivities of both example 3 and example 4 exceeded 30W m^-1 K^-1Wherein example 3 electromagnetic shielding index exceeds 40 dB; example 4 electromagnetic shielding index is over 60dB and tensile strength is over 25 MPa; the information shows that the thermal interface material has enhanced coupling in heat conduction performance, electromagnetic shielding performance and mechanical performance.

The above-mentioned embodiments only express several embodiments of the present disclosure, and the description thereof is more specific and detailed, but not construed as limiting the scope of the present disclosure. It should be noted that, for those skilled in the art, various changes, substitutions of equivalents, improvements and the like can be made without departing from the spirit of the disclosure, and these are all within the scope of the disclosure. Therefore, the protection scope of the present disclosure should be subject to the appended claims.

The above-mentioned embodiments are merely embodiments for expressing the disclosure, and the description is more specific and detailed, but not construed as limiting the scope of the disclosure. It should be noted that, for those skilled in the art, various changes, substitutions of equivalents, improvements and the like can be made without departing from the spirit of the disclosure, and these are all within the scope of the disclosure. Therefore, the protection scope of the present disclosure should be subject to the appended claims.

Claims

1. A modified graphite-based functional filler, comprising:

the expanded graphite in the form of worms may be,

2. A preparation method of a modified graphite-based functional filler is characterized by comprising the following steps:

obtaining vermicular expanded graphite;

3. The method for preparing a modified graphite-based functional filler according to claim 2, characterized in that:

the chemical activity coating is a nano-scale chemical activity coating;

and/or the presence of a gas in the interior of the container,

the vermicular expanded graphite is a product of in-situ thermal expansion of crystalline flake graphite, graphite intercalation compound, graphite carbon tube or graphite-based carbon fiber;

and/or the presence of a gas in the interior of the container,

the modifier is a coupling agent;

4. The method for preparing a modified graphite-based functional filler according to claim 3, characterized in that:

the modifier comprises 4- (2-aminoethyl) -1, 2-benzenediol hydrochloride, vinylmethoxysilane or aminoethoxy silane;

and/or the presence of a gas in the interior of the container,

the pH value of the reaction ranges from 7 to 12.

5. A thermal interface material, comprising:

the modified graphite-based functional filler of claim 1.

6. The thermal interface material of claim 5, wherein:

the thermal interface material also includes a liquid rubber.

7. The thermal interface material of claim 6, wherein:

the liquid rubber comprises one or a mixture of more of nitrile rubber, natural rubber, ethylene propylene rubber, butadiene rubber or styrene butadiene rubber.

8. A method of making a thermal interface material, comprising:

the liquid rubber of claim 6 or 7 and the modified graphite-based functional filler;

9. The method of preparing a thermal interface material of claim 8, wherein:

the mass percentage of the solid of the mixture is 10-40 wt%;

and/or the presence of a gas in the interior of the container,

the method for obtaining the mixture adopts a vacuum multi-stage mixing mode;

and/or the presence of a gas in the interior of the container,

the mixture also comprises a vulcanization accelerator and an anti-aging agent;

the vulcanization accelerator comprises sulfur or 2, 2' -dithiodibenzothiazole;

the vulcanization accelerator is: the anti-aging agent: the mass ratio of the liquid rubber is 0.5-2: 0.5-2: 100, respectively;

and/or the presence of a gas in the interior of the container,

the conditions of the vulcanization addition are as follows: pressurizing for 6-8 MPa at 120-180 ℃, maintaining the pressure for 1-3 min, and then releasing the pressure; pressurizing for the second time at 10-12 MPa, maintaining the pressure for 2-5 min, and then releasing the pressure; and pressurizing for three times at 14-18 MPa, maintaining the pressure for 4-6 min, then decompressing, cooling to normal temperature, and then demolding.

10. The method of preparing a thermal interface material of claim 9, wherein:

the vacuum multi-stage mixing mode adopts a vacuum three-stage stirring mixing mode; wherein the vacuum degree during mixing is-90 to 100 kPa; the first-order mixing speed is 200-500 rpm, and the stirring time is 30-60 s; the second-order mixing speed is 600-1200 rpm, and the stirring time is 60-180 s; the rotation speed of the three-order mixing is 1500-2500 rpm, and the stirring time is 120-240 s;

and/or the presence of a gas in the interior of the container,

adding a diluent during the vacuum multi-stage mixing;

the mass ratio of the diluent to the liquid rubber is 0.3-1.8: 1.