TWI881569B - Thermal conductive and electrically insulating plastic composite material and method of forming the same - Google Patents

Abstract

A thermal conductive and electrically insulating plastic composite material and a method of forming the same are provided. The thermal conductive plastic composite material includes thermoplastic and modified thermal conductive filler dispersed in the thermoplastic. The modified thermal conductive filler includes an inorganic thermal conductive material and at least a siloxane compound covalent bonding to a surface of the inorganic thermal conductive material, in which the siloxane compound is bonded between the inorganic thermal conductive material and the thermoplastic. The modified thermal conductive filler can be homogeneously dispersed in the thermoplastic, thereby effectively increasing thermal conductivity of the thermal conductive and electrically insulating plastic composite material.

Description

Thermally conductive insulating plastic composite material and manufacturing method thereof

The present invention relates to a thermally conductive plastic material and a manufacturing method thereof, and in particular to a thermally conductive insulating plastic composite material and a manufacturing method thereof.

Thermally conductive plastic (TCP) is a material that combines the mechanical properties of plastic with better thermal conductivity. In other words, thermally conductive plastic can effectively transfer heat while maintaining the required properties of plastic, such as light weight, chemical resistance and easy processing. Thermally conductive plastics are widely used in electronic equipment, electric vehicles and aerospace. In recent years, the requirements for thermal management in electronic equipment have further promoted the demand for thermally conductive insulating plastics. Thermally conductive plastics can provide electronic components with improved heat dissipation problems to reduce overheating and maintain component performance and reliability.

Plastic materials have poor thermal conductivity and must be improved by other thermal conductive materials (or thermal conductive powders). However, adding too much thermal conductive material to the process will not only increase costs, but also cause the mechanical properties of thermal conductive plastics to deteriorate, fluidity to deteriorate, and molding problems. In addition, when thermal conductive materials are dispersed in plastics, there may be problems with dispersion and stability, which in turn leads to poor heat transfer efficiency and poor processing efficiency.

In view of this, there is an urgent need to provide a thermally conductive insulating plastic composite material and a manufacturing method thereof to reduce the amount of thermally conductive material added and maintain the thermal conductivity, thereby reducing costs and improving the dispersion and stability issues.

One aspect of the present invention is to provide a thermally conductive insulating plastic composite material, which utilizes a modified thermally conductive filler material dispersed in a thermoplastic plastic to improve the dispersibility of the thermally conductive material and enhance the thermal conductivity of the thermally conductive insulating plastic composite material.

Another aspect of the present invention is to provide a method for manufacturing a thermally conductive insulating plastic composite material, which first uses a silane coupling agent to chemically modify an inorganic thermally conductive material so as to effectively disperse it in a thermoplastic plastic.

According to one aspect of the present invention, a thermally conductive insulating plastic composite material is provided, which comprises a thermoplastic plastic and a modified thermally conductive filling material dispersed in the thermoplastic plastic. The modified thermally conductive filling material comprises an inorganic thermally conductive material and at least one siloxane compound covalently bonded to the surface of the inorganic thermally conductive material, wherein the siloxane compound is bonded between the inorganic thermally conductive material and the thermoplastic plastic.

According to one embodiment of the present invention, the thermoplastic plastic comprises polypropylene (PP), polyamide (PA), polycarbonate (PC), acrylonitrile-butadiene-styrene copolymer (ABS) or a combination thereof.

According to an embodiment of the present invention, the inorganic thermal conductive material comprises aluminum nitride, aluminum oxide, boron nitride, silicon carbide or a combination thereof.

According to one embodiment of the present invention, the siloxane compound comprises at least one hydrolyzable group and at least one special functional group, and the special functional group comprises an organic functional group that can chemically react with the thermoplastic plastic.

According to one embodiment of the present invention, based on the weight of the thermally conductive insulating plastic composite material being 100 wt%, the content of the thermoplastic plastic is 30 wt% to 60 wt%, and the content of the modified thermally conductive filling material is 40 wt% to 70 wt%.

According to an embodiment of the present invention, the volume percentage of the thermally conductive insulating plastic composite material is 100%, and the volume percentage of the inorganic thermally conductive material is 20% to 50%.

According to one embodiment of the present invention, the inorganic thermal conductive material comprises a first inorganic material and a second inorganic material. The average particle size of the first inorganic material is 40 μm to 80 μm, and the average particle size of the second inorganic material is 2 μm to 8 μm. The mixing ratio of the first inorganic material to the second inorganic material is 100:0 to 50:50.

According to another aspect of the present invention, a method for manufacturing a thermally conductive insulating plastic composite is provided. The method includes providing a plurality of inorganic thermally conductive materials; chemically modifying the inorganic thermally conductive materials using a silane coupling agent to form a modified thermally conductive filling material, wherein the mixing ratio of the silane coupling agent to the inorganic thermally conductive material is 2:98 to 5:95; and mixing the modified thermally conductive filling material with a thermoplastic plastic to obtain a thermally conductive insulating plastic composite.

According to one embodiment of the present invention, the chemical modification operation includes a step of hydrolyzing the silane coupling agent to obtain a plurality of hydrolyzed silane coupling agents, wherein each of the hydrolyzed silane coupling agents comprises at least one hydrolyzed group; and a step of dehydrating the inorganic thermal conductive material and the hydrolyzed silane coupling agent to covalently bond the hydrolyzed silane coupling agent and the inorganic thermal conductive material.

According to an embodiment of the present invention, the silane coupling agent comprises at least one hydrolyzed group and at least one special functional group, and the special functional group is selected from the group consisting of epoxy group, amino group, acryl group, alkenyl group and isocyanate group.

By using the thermally conductive insulating plastic composite material and the manufacturing method thereof of the present invention, an inorganic thermally conductive material is modified by a silane coupling agent. The obtained modified thermally conductive filling material can be uniformly dispersed in a thermoplastic plastic and enhance the interface strength between the inorganic thermally conductive material and the thermoplastic plastic. Therefore, the thermal conductivity of the thermally conductive insulating plastic composite material can be greatly enhanced.

As used in the present invention, "around", "about", "approximately" or "substantially" generally means within 20%, within 10%, or within 5% of the stated value or range.

As mentioned above, it is known that a large amount of thermal conductive material must be added to achieve the effect of improving thermal conductivity. However, this method not only increases the manufacturing cost, but also reduces the mechanical properties (especially impact strength) and fluidity and formability of the thermal conductive plastic during processing. Furthermore, since the mixing of thermal conductive material and plastic has dispersion and stability problems, it often results in poor thermal conductivity and processing efficiency of the thermal conductive plastic. Therefore, the present invention provides a thermally conductive insulating plastic composite material and a manufacturing method thereof, wherein an inorganic thermally conductive material is modified by a silane coupling agent, and the obtained modified thermally conductive filling material can be effectively dispersed in a thermoplastic plastic, thereby reducing the interfacial thermal resistance between the inorganic thermally conductive material and the thermoplastic plastic, and increasing the overlap rate between the modified thermally conductive filling materials, thereby effectively improving the thermal conductivity of the thermally conductive insulating plastic composite material.

The thermally conductive insulating plastic composite of the present invention comprises a thermoplastic plastic and a modified thermally conductive filling material dispersed in the thermoplastic plastic. In some embodiments, based on the weight of the thermally conductive insulating plastic composite being 100 wt%, the content of the thermoplastic plastic is about 30 wt% to about 60 wt%, and the content of the modified thermally conductive filling material is about 40 wt% to about 70 wt%. When the contents of the thermoplastic plastic and the modified thermally conductive filling material are respectively within the aforementioned ranges, the formed thermally conductive insulating plastic composite can have better thermal conductivity and good mechanical properties. In some embodiments, the thermoplastic plastic comprises polypropylene (PP), polyamide (PA), polycarbonate (PC), acrylonitrile-butadiene-styrene copolymer (ABS) or a combination thereof.

The modified thermally conductive filling material is prepared by chemically modifying an inorganic thermally conductive material with a silane coupling agent. In some embodiments, the inorganic thermally conductive material comprises aluminum nitride, aluminum oxide, boron nitride, silicon carbide, or a combination thereof, preferably aluminum nitride. In some embodiments, based on the volume percentage of the thermally conductive insulating plastic composite being 100%, the volume percentage of the inorganic thermally conductive material is about 20% to about 50%. When the volume percentage of the inorganic thermally conductive material is within the aforementioned range, the thermal conductivity of the thermally conductive insulating plastic composite can be effectively improved.

The inorganic thermally conductive material may include inorganic materials having different average particle sizes. In other words, in some embodiments, the inorganic thermally conductive material includes a first inorganic material and a second inorganic material, wherein the average particle size of the first inorganic material is about 40 μm to about 80 μm; and the average particle size of the second inorganic material is about 2 μm to about 8 μm. Preferably, the first inorganic material and the second inorganic material include the same material. In some embodiments, the mixing ratio of the first inorganic material to the second inorganic material is about 100:0 to about 50:50.

Generally speaking, inorganic materials of different particle sizes have different material costs, but when the first inorganic material and the second inorganic material are mixed in the aforementioned specific mixing ratio, the thermal conductivity of the thermally conductive insulating plastic composite material will not have a significant difference. In a specific example, the first inorganic material is spherical aluminum nitride with a larger particle size (e.g., D ₅₀ is 55 μm), and the second inorganic material is irregular aluminum nitride with a smaller particle size (e.g., D ₅₀ is 5 μm). Compared to spherical aluminum nitride with a larger particle size, the material cost of aluminum nitride with a smaller particle size and an irregular shape is lower, and the thermally conductive insulating plastic composite material produced within the aforementioned mixing ratio range can have good thermal conductivity. Therefore, the effect of reducing material costs can be achieved by mixing the irregular aluminum nitride with a smaller particle size.

The modified thermally conductive filling material after chemical modification includes an inorganic thermally conductive material and a siloxane compound covalently bonded to the inorganic thermally conductive material. Therefore, when the modified thermally conductive filling material is dispersed in a thermoplastic plastic, the siloxane compound is bonded between the thermoplastic plastic and the inorganic thermally conductive material. In some embodiments, the siloxane compound includes at least one hydrolyzed group (e.g., an alkoxy group) and at least one special functional group, wherein the hydrolyzed group can bond with the inorganic thermally conductive material, and the special functional group includes an organic functional group that can chemically react with the thermoplastic plastic. In some embodiments, the special functional group is selected from the group consisting of an epoxy group, an amino group, an acryl group, an alkenyl group, and an isocyanate group.

In some embodiments, the thermoplastic plastic may optionally contain glass fibers dispersed therein. In the aforementioned embodiments, based on the weight of the thermally conductive insulating plastic composite being 100 wt%, the amount of glass fibers used is 3 wt% to 10 wt%. The purpose of adding glass fibers is to enhance the strength of the thermally conductive insulating plastic composite, and when the amount of glass fibers added is within the aforementioned range, the strength of the thermally conductive insulating plastic composite can be effectively increased.

The manufacturing method of the thermally conductive insulating plastic composite material includes chemically modifying an inorganic thermally conductive material using a silane coupling agent to form a modified thermally conductive filling material. In some embodiments, the mixing ratio of the silane coupling agent to the inorganic thermally conductive material is about 2:98 to about 5:95. When the mixing ratio of the silane coupling agent to the inorganic thermally conductive material is within the aforementioned range, the modified thermally conductive filling material can be effectively dispersed in the thermoplastic plastic, thereby improving the thermal conductivity of the thermally conductive insulating plastic composite material.

In some embodiments, the silane coupling agent comprises at least one hydrolyzable group and at least one special functional group. For example, the silane coupling agent has the structure of the following formula (1). (1) In formula (1), X is an amino group, an alkenyl group, an acryl group, an epoxy group or an isocyanate group; L is a linear alkyl group having 2 to 6 carbon atoms, an amino group (-NH-) or a carbonyl group; R is each independently an alkyl group having 1 to 4 carbon atoms or a hydrogen atom; and n is an integer from 1 to 3. In some specific examples, the silane coupling agent is 3-aminopropyltriethoxysilane or 3-acryloxypropyltrimethoxysilane.

In some embodiments, the chemical modification operation comprises a hydrolysis step and a dehydration step. The hydrolysis step is to subject the silane coupling agent to a hydrolysis reaction so that the silane coupling agent comprises at least one hydrolyzed group (e.g., -OH group). The hydrolysis step comprises first mixing the silane coupling agent with an alcohol solvent, wherein the mixing conditions may be, for example, a pH value of about 10 to about 13 and a temperature of about 25°C to about 40°C for about 4 hours to about 7 hours. When the silane coupling agent comprises an amine group, the aforementioned pH value should be adjusted to about 3 to about 5. In one embodiment, based on the total volume of the solution being 100%, the silane coupling agent is about 1% to 5%, and the alcohol solvent is about 90% to 95%. In one embodiment, the carbon number of the alcohol solvent may correspond to the carbon number of the silane alkoxy group of the silane coupling agent (such as R in the above formula (1)), such as methanol, ethanol or propanol. The hydrolysis step further includes dripping a few drops of deionized water to cause the above mixed solution to undergo a hydrolysis reaction.

Then, an inorganic thermally conductive material is added to the mixed solution and reacted for about 10 minutes to about 30 minutes to perform a dehydration step, so that the silane coupling agent covalently bonds to the inorganic thermally conductive material and is coated on the surface of the inorganic thermally conductive material. In some embodiments, the dehydration step further includes baking at a temperature of about 80°C to about 120°C for about 1 hour to about 6 hours after wetting with an anhydrous alcohol solvent. It can be understood that during the aforementioned chemical modification operation, based on a microscopic perspective, the silane coupling agent on the surface of the inorganic thermally conductive material can selectively hydrolyze with the adjacent silane coupling agent to form a -Si-O-Si- bonding structure, thereby enhancing the modification effect.

The manufacturing method of the thermally conductive insulating plastic composite material also includes mixing the modified thermally conductive filling material and the thermoplastic plastic to obtain the thermally conductive insulating plastic composite material. Since the silane coupling agent contains a special functional group that is reactive with the thermoplastic plastic, the silane coupling agent can be bonded between the inorganic thermally conductive material and the thermoplastic plastic after the reaction. In this way, the inorganic thermally conductive materials can be effectively contacted to form a heat energy channel. Therefore, the thermal conductivity efficiency can be improved without using a large amount of inorganic thermally conductive materials.

FIG. 1 is a scanning electron microscope (SEM) image of a modified thermally conductive filling material obtained by modifying aluminum nitride with a silane coupling agent according to some embodiments of the present invention. As can be seen from FIG. 1, the aluminum nitride powder is uniformly distributed in a granular form, that is, the inorganic thermally conductive material modified by the silane coupling agent can be uniformly distributed in the thermoplastic plastic, and has good dispersibility without agglomeration. FIG. 2 is a scanning electron microscope image of a thermally conductive insulating plastic composite material according to some embodiments of the present invention, which is a thermally conductive insulating plastic composite material in which aluminum nitride modified by silane is bonded to polycarbonate. As can be seen from FIG. 2, the modified aluminum nitride has good bonding with polycarbonate, and no pores exist, that is, the interface compatibility is good. In other words, the chemical modification of the silane coupling agent can effectively improve the dispersibility of the inorganic thermal conductive material and effectively bond the inorganic thermal conductive material and the thermoplastic plastic.

Several embodiments are used below to illustrate the application of the present invention, but they are not intended to limit the present invention. Those with ordinary knowledge in the technical field of the present invention can make various changes and modifications without departing from the spirit and scope of the present invention. Examples 1-1 to 4-1

The thermally conductive insulating plastic composite materials of Examples 1-1 to 4-1 are prepared by using polycarbonate (PC) containing a small amount of glass fiber (GF) as a thermoplastic plastic, aluminum nitride as an inorganic thermal conductive material, and independently using 3-aminopropyl triethoxysilane or 3-acryloxypropyl trimethoxysilane as a silane coupling agent, wherein a small amount of glass fiber is added to enhance the strength of the thermally conductive insulating plastic composite material. The inorganic thermal conductive material includes spherical aluminum nitride with a D ₅₀ particle size of 55 μm and optionally includes irregular aluminum nitride with a D ₅₀ particle size of 5 μm. In Examples 1-1 to 4-1, the mixing ratio of polycarbonate and modified aluminum nitride is adjusted, and the addition ratio of spherical aluminum nitride and irregular aluminum nitride is controlled. The obtained thermally conductive insulating plastic composite material is tested for thermal conductivity according to the transient plane heat source method (Hot Disk) specified in ISO-22007-2, and for tensile strength and bending strength according to ASTM D638 and ASTM D790, and insulation impedance is measured using the transient heat source plane method. The mixing ratio of each component of Examples 1-1 to 4-1 is shown in Table 1, where modified AlN represents aluminum nitride modified by a silane coupling agent. The thermal conductivity, tensile strength, insulation resistance and flexural strength of Examples 1-1 to 4-1 are shown in Table 2.

Table 1 Embodiment PC (wt%) GF (wt%) Modified AlN (wt%) Modified AlN (Vol%) AlN mixing ratio after modification (55μm:5μm) 1-1 twenty three% 7% 70% 50% 50:50 1-2 twenty three% 7% 70% 50% 70:30 1-3 twenty three% 7% 70% 50% 80:20 1-4 twenty three% 7% 70% 50% 100:0 2-1 32% 5.5% 63% 40% 50:50 2-2 32% 5.5% 63% 40% 80:20 2-3 32% 5.5% 63% 40% 100:0 3-1 43% 4.6% 53% 30% 50:50 3-2 43% 4.6% 53% 30% 80:20 4-1 56% 3.5% 40% 20% 100:0

Table 2 Embodiment Tensile strength(MPa) Bending strength (MPa) Insulation resistance(Ω) Thermal conductivity (W/mK) 1-1 44.6 71.2 1.1x10 ¹⁴ 11.76 1-2 46.5 73.6 7.5x10 ¹³ 10.43 1-3 47.6 75.2 7.3x10 ¹³ 10.51 1-4 38.6 64.3 5.6x10 ¹⁴ 10.91 2-1 48.1 71.6 8.5x10 ¹³ 8.72 2-2 43.7 67.8 6.9x10 ¹³ 9.05 2-3 41.6 63.1 3.6x10 ¹⁴ 8.65 3-1 45.5 73.1 4.6x10 ¹⁴ 6.34 3-2 39.8 68.4 5.6x10 ¹³ 6.17 4-1 56.0 80.1 1.1x10 ¹⁴ 4.67

According to Table 1 and Table 2 above, since the amount of inorganic thermally conductive material added in Examples 1-1 to 4-1 does not exceed 50 vol%, the thermally conductive insulating plastic composite materials of Examples 1-1 to 4-1 all have sufficient mechanical strength. In addition, the thermally conductive insulating plastic composite materials after adding the modified thermally conductive filler material can have good electrical insulation properties, and the insulation impedance thereof is between 5.6x10 ¹³ Ω and 5.6x10 ¹⁴ Ω. Furthermore, the thermally conductive insulating plastic composite materials of Examples 1-1 to 4-1 have better thermal conductivity coefficients. Compared to the thermal conductivity of conventional inorganic filler thermally conductive plastic materials (about 0.4 W/mK to 3 W/mK), the thermal conductivity of Example 1-1 can be increased by more than 60 times to 11.76 W/mK. Therefore, even if more aluminum nitride with a smaller particle size is added, the thermal conductivity of the thermally conductive insulating plastic composite can still be effectively improved.

According to the above embodiments, the present invention provides a thermally conductive insulating plastic composite material and a manufacturing method thereof, wherein the inorganic thermally conductive material is modified by a silane coupling agent, and the obtained modified thermally conductive filling material can be effectively dispersed in the thermoplastic plastic, thereby reducing the interfacial thermal resistance between the inorganic thermally conductive material and the thermoplastic plastic, and increasing the overlap rate between the modified thermally conductive filling materials, thereby effectively improving the thermal conductivity of the thermally conductive insulating plastic composite material. Secondly, since the inorganic thermally conductive material used has good electrical insulation, the modified thermally conductive filling material with uniform dispersion can effectively improve the insulation of the thermally conductive insulating plastic composite material.

Although the present invention has been disclosed as above with several embodiments, they are not intended to limit the present invention. Anyone with ordinary knowledge in the technical field to which the present invention belongs can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be defined by the scope of the attached patent application.

without

The present disclosure can be better understood by reading the following detailed description in conjunction with the accompanying drawings. [Figure 1] is a scanning electron microscope (SEM) image of a modified thermally conductive filler material according to some embodiments of the present invention. [Figure 2] is a scanning electron microscope image of a thermally conductive insulating plastic composite material according to some embodiments of the present invention.

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Claims (9)

A thermally conductive insulating plastic composite material comprises: a thermoplastic plastic; and a plurality of modified thermally conductive filling materials dispersed in the thermoplastic plastic, wherein each of the modified thermally conductive filling materials comprises: an inorganic thermally conductive material, wherein the inorganic thermally conductive material comprises a first inorganic material and a second inorganic material, an average particle size of the first inorganic material is 40 μm to 80 μm, and an average particle size of the second inorganic material is 2 μm to 8 μm; at least one siloxane compound covalently bonded to a surface of the inorganic thermally conductive material, and the at least one siloxane compound is bonded between the inorganic thermally conductive material and the thermoplastic plastic; and a glass fiber, wherein the weight of the thermally conductive insulating plastic composite material is 100 wt%, the content of the thermoplastic plastic is 23 wt% to 56 wt%, the content of the modified thermal conductive filling materials is 40 wt% to 70 wt%, and the content of the glass fiber is 3 wt% to 7 wt%. A thermally conductive insulating plastic composite as described in claim 1, wherein the thermoplastic plastic comprises polypropylene (PP), polyamide (PA), polycarbonate (PC), acrylonitrile-butadiene-styrene copolymer (ABS) or a combination thereof. A thermally conductive insulating plastic composite material as described in claim 1, wherein the inorganic thermally conductive material comprises aluminum nitride, aluminum oxide, boron nitride, silicon carbide or a combination thereof. A thermally conductive insulating plastic composite material as described in claim 1, wherein the at least one siloxane compound comprises at least one hydrolyzed group and at least one special functional group, and the at least one special functional group comprises an organic functional group that can undergo a chemical reaction with the thermoplastic plastic. The thermally conductive insulating plastic composite material as described in claim 1, wherein the volume percentage of the inorganic thermally conductive material is 20% to 50% based on the volume percentage of the thermally conductive insulating plastic composite material being 100%. The thermally conductive insulating plastic composite material as described in claim 1, wherein a mixing ratio of the first inorganic material to the second inorganic material is 100:0 to 50:50, and the mixing ratio of the first inorganic material to the second inorganic material excludes 100:0. A method for manufacturing a thermally conductive insulating plastic composite material, comprising: Providing a plurality of inorganic thermally conductive materials; Using a plurality of silane coupling agents to perform a chemical modification operation on the inorganic thermally conductive materials to form a plurality of modified thermally conductive filling materials, wherein a mixing ratio of the silane coupling agents to the inorganic thermally conductive materials is 2:98 to 5:95, the inorganic thermally conductive materials include a first inorganic material and a second inorganic material, an average particle size of the first inorganic material is 40 μm to 80 μm, and an average particle size of the second inorganic material is 2 μm to 8 μm; and The modified thermally conductive filling materials, a thermoplastic plastic and a glass fiber are mixed to obtain the thermally conductive insulating plastic composite material, wherein based on the weight of the thermally conductive insulating plastic composite material being 100 wt%, the content of the thermoplastic plastic is 23 wt% to 56 wt%, the content of the modified thermally conductive filling materials is 40 wt% to 70 wt%, and the content of the glass fiber is 3 wt% to 7 wt%. The manufacturing method of the thermally conductive insulating plastic composite material as described in claim 7, wherein the chemical modification operation comprises: Performing a hydrolysis step on the silane coupling agents to obtain a plurality of hydrolyzed silane coupling agents, wherein each of the hydrolyzed silane coupling agents contains at least one hydrolyzed group; and Performing a dehydration step on the inorganic thermal conductive materials and the hydrolyzed silane coupling agents to covalently bond the hydrolyzed silane coupling agents and the inorganic thermal conductive materials. A method for manufacturing a thermally conductive insulating plastic composite as described in claim 7, wherein the silane coupling agents contain at least one hydrolyzed group and at least one special functional group, and the at least one special functional group is selected from a group consisting of an epoxy group, an amino group, an acryl group, an alkenyl group and an isocyanate group.