Thermally conductive molded article and method of making the same
A thermally conductive molded article is produced by molding a conductive composition into a predetermined shape. The composition includes a polymer matrix and carbon powders. The carbon powders are obtained by graphitizing a polymeric material that has an aromatic ring on its main chain by heating. The carbon powders are aligned in a certain direction in the polymer matrix. Thus, the molded article can be produced easily and effectively that has excellent thermal conductivity in a given direction and that is suitable for use as a heat radiator, heat transfer member, or a component thereof in electronic hardware.
1. A thermally conductive molded article having the shape of a sheet and produced by molding a conductive composition into a predetermined shape, the composition comprising:
a polymer matrix; and
carbon powders, wherein the carbon powders are obtained by (1) pulverizing or cutting a polymeric material and then graphitizing the polymeric material or (2) graphitizing a polymeric material via heating and then pulverizing or cutting the graphitized material, the polymeric material having an aromatic ring on its main chain;
wherein, the carbon powders have a hexagonal graphite crystal structure; and the carbon powders and the graphite planes of the hexagonal graphite crystal structure are aligned in the polymer matrix in the direction perpendicular to the molded article sheet.
2. The molded article as in claim 1 , wherein the polymeric matermal is a polybenzazole fiber, an aromatic polyamnide fiber, an aromatic polyimide fiber, a polyphenylene sulfide fiber, a wholly aromatic polyester fiber, or a mixture thereof.
3. The molded article as in claim 1 , wherein the polymeric material is a polybenzazole film, an aromatic polyamide film, an aromatic polyimide film, a polyphenylene sulfide film, a wholly aromatic polyester film, or a mixture thereof.
4. The molded article as in claim 1 , wherein the carbon powders have an interplanar spacing (d002) of graphite planes of less than 0.3770 nm by x-ray diffractometry.
5. The molded article as in claim 1 , wherein the carbon powders have an average particle size of from 1 to 500 μm.
6. The molded article as in claim 1 , wherein the polymer matrix is thermoplastic resin, thermoplastic elastomer, thermosetting resin, vulcanized rubber, or a mixture thereof.
7. A method of making a thermally conductive molded article having the shape of a sheet, the method comrising:
providing a thermally conductive composition including a polymer matrix and carbon powders, wherein the carbon powders are obtained (1) pulverizing or cutting a polymeric material and then graphitizing the polymeric material or (2) graphitizing a polymerte material via heating and then pulverizing or cutting the graphitized material, the polymeric material having an aromatic ring on its main chain;
applying a magnetic field to the composition so that the carbon powders are aligned in a certain direction in the polymer matrix; and
hardening the composition with the carbon powders aligned in the certain direction;
wherein the carbon powders have a hexagonal graphite crystal structure; and the carbon powders and the graphite planes of the gexagonal graphite crystal structure are alignein the polymer matrix in the direction perpendicular to the molded article sheet.
8. The method as in claim 7 , wherein the carbon powders are graphitized by heating the polymeric material at least 2500 degree C. under vacuum or in an inert gas.
9. The method as in claim 7 , wherein the polymeric material is a polybenzazole fiber, an aromatic polyamide fiber, an aromatic polyimide fiber, a polyphenylene sulfide fiber, a wholly aromatic polyester fiber, or a mixture thereof.
10. The method as in claim 7 , wherein the polymeric material is a ploybenzazole film, an aromatic polyamide film, an, aromatic polyimide film, a polyphenylene sulfide film, a wholly aromatic polyester film, or a mixture thereof.