COMPOSITE MATERIAL

Abstract

The present application provides a composite material and a method for producing the same. The present application can provide a composite material having excellent other necessary properties such as impact resistance or processability, as well as excellent heat conduction characteristics as a tight heat transfer network is formed therein by an anisotropic heat-conductive filler.

Claims

1. A composite material comprising a polymer matrix and a thermal conductor, wherein the thermal conductor comprises a first anisotropic heat-conductive filler combined with a magnetic body and a second anisotropic heat-conductive filler not combined with the magnetic body, wherein a volume of the thermal conductor in the composite material is 60 vol % or less of the composite material, and wherein a volume of the first anisotropic heat-conductive filler is at most 3 times a volume of the second anisotropic heat-conductive filler.

2. The composite material according to claim 1, wherein the first anisotropic heat-conductive filler is oriented to form heat transfer paths and the second anisotropic heat-conductive filler connects the heat transfer paths.

3. The composite material according to claim 2, wherein the composite material is in the form of a film, and the first anisotropic heat-conductive filler is oriented in a thickness direction of the film to form the heat transfer paths.

4. The composite material according to claim 1, wherein the composite material is in the form of a film, and a thermal conductivity measured along a thickness direction of the film is at least 0.3 W/mK.

5. The composite material according to claim 3, wherein a thickness of the film form is at least 10 m.

6. The composite material according to claim 1, wherein the polymer matrix comprises one or more selected from the group consisting of an acrylic resin, a silicone resin, an epoxy resin, a urethane resin, an amino resin, a polyester, an olefin resin and a phenol resin.

7. The composite material according to claim 1, wherein the first or second anisotropic heat-conductive filler is alumina, (aluminum nitride (AlN), (boron nitride (BN), silicon nitride, silicon carbide (SiC), beryllium oxide (BeO), carbon black, graphene, graphene oxide, carbon nanotube or graphite.

8. The composite material according to claim 1, wherein the first or second anisotropic heat-conductive filler has an aspect ratio of at least 5.

9. The composite material according to claim 8, wherein the first or second anisotropic heat-conductive filler has an average particle diameter of the cross section in a range of from about 1 m to 100 m.

10. The composite material according to claim 1, wherein the magnetic body is iron oxide, ferrite or alloy nanoparticles.

11. The composite material according to claim 1, wherein the magnetic body has an average particle diameter in a range of from about 10 nm to 1,000 m.

12. A method for producing the composite material of claim 1, the method comprising: curing a curable precursor of the polymer matrix, said curing carried out while applying a magnetic field to a mixture comprising the curable precursor, the first anisotropic heat-conductive filler combined with the magnetic body, and the second anisotropic heat-conductive filler not combined with the magnetic body, to orient the first anisotropic heat-conductive filler combined with the magnetic body, to thereby form the composite material comprising the polymer matrix and the thermal conductor.

13. The composite material according to claim 3, wherein a thermal conductivity measured along the thickness direction of the film is at least 4 W/mK.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0044] FIG. 1 is a photograph of the magnetic composite filler produced in Production Example 1.

[0045] FIGS. 2 and 3 are photographs of the composite materials produced in Examples 1 and 2.

[0046] FIG. 4 is a photograph of the composite material produced in Comparative Example 2.

MODE FOR INVENTION

[0047] The present application will be specifically described by way of examples, but the scope of the present application is not limited to the following examples.

Production Example 1. Production of Magnetic Composite Filler (A)

[0048] A composite filler was formed by using boron nitride in the form of fibers having an aspect ratio of about 40 or so and an average diameter of the cross section in the direction perpendicular to the longitudinal direction of about 10 m or so as an anisotropic heat-conductive filler, and using iron oxide (Fe2O3) particles having an average particle diameter in a level of about 100 nm to 200 nm as a magnetic body. The iron oxide particles were immersed in a hydrochloric acid solution at room temperature to activate surface reaction groups. Subsequently, the iron oxide particles with activated surface reaction groups and the boron nitride were dispersed in an aqueous solution at a weight ratio of 10:6 (boron nitride:iron oxide), treated with an ultrasonic wave of 120 W for about 1 hour, and then washed and dried to produce a composite filler. FIG. 1 is a photograph of the composite filler produced above.

Example 1

[0049] As a curable precursor of a polymer matrix, a thermosetting silicone composition (Dow Corning, Sylgard 184) was used. The curable precursor, the composite filler (first filler) produced in Production Example 1 and boron nitride in the form of fibers having an aspect ratio of about 40 or so and an average diameter of the cross section in the direction perpendicular to the longitudinal direction of about 10 m or so as an anisotropic heat-conductive filler (second filler) were mixed to prepare a mixture. The volume ratio calculated by the density and the applied weights of the curable precursor, first and second fillers applied to the mixture was about 50:10:40 (=curable precursor:first filler:second filler) or so. The prepared mixture was poured into a film-shaped Teflon mold (thickness: about 1 mm) and cured at a temperature of 120 C. for 30 minutes or so, while applying a magnetic field in the upper and lower directions of the film form at an intensity of about 700 to 800 Gauss by a neodymium magnet, to form a film-shaped composite material. FIG. 2 is a cross-sectional photograph of the composite material formed as described above. As shown in the drawing, while the composite filler is oriented in the vertical direction (magnetic field direction, thickness direction) to form heat transfer paths, the boron nitride filler oriented in the substantially horizontal direction connects the heat transfer paths to form a network. The thermal conductivity of such a composite material in the Z-axis direction (thickness direction) was about 5.8 W/mK.

[0050] The thermal conductivity was determined by obtaining the thermal diffusivity (A), specific heat (B) and density (C) of the composite material and substituting them into an equation of thermal conductivity=ABC, where the thermal diffusivity was measured with a laser flash method (LFA equipment, model name: LFA467), the specific heat was measured by way of DSC (differential scanning calorimeter) equipment and the density was measured with Archimedes method.

[0051] On the other hand, FIG. 3 is a photograph of the surface of the produced composite material, and it can be confirmed that defects on the surface hardly appear as compared with the case of Comparative Example 2.

Comparative Example 1

[0052] A composite material was produced in the same manner as in Example 1, except that the mixture was prepared so that the volume ratio of the curable precursor to the first filler of Production Example 1 was 1:1 without applying the second filler, that is, the filler not combined with the magnetic body. The thermal conductivity of the composite thus produced in the Z-axis direction (thickness direction) was about 2.5 W/mK.

Comparative Example 2

[0053] A composite material was produced in the same manner as in Example 1, except that the mixture was prepared so that the volume ratio calculated by the density and the applied weights of the curable precursor, the first and second fillers was about 50:40:10 (=curable precursor:first filler:second filler). FIG. 4 is a photograph of the surface of the produced composite material, and a large defect was confirmed as shown in the drawing.

Comparative Example 3

[0054] A composite material was prepared in the same manner as in Example 1, except that the mixture was prepared so that the volume ratio of the curable precursor and the second filler was about 3:7 or so without applying the first filler, that is, the filler combined with the magnetic body. The thermal conductivity of the composite thus produced in the Z-axis direction (thickness direction) was about 2.4 W/mK.