Toray Industries, Inc.

Toray Research Center, Inc.

Yoji Matsuhisa

Masanobu Kobayashi

Kazuharu Shimizu

Akira Okuda

Katsumi Yamasaki

Motoi Itoh

Makoto Kibayashi

Toru Hiramatsu

Kazuo Yoshida

Gen Katagiri

Disclosed are carbon fibers consisting of a plurality of single filaments, wherein the carbon fibers as a resin impregnated strand are characterized by satisfying the following relations: &sgr;&gE;11.1&minus;0.75 d where &sgr; is the tensile strength of said carbon fibers as a resin impregnated strand in GPa, and d is the average diameter of said single filaments in &mgr;m, and RD&lE;0.05 where RD is the difference in crystallinity between the inner and outer layers of each of the single filaments evaluated with RAMAN, and an acrylic fibers for producing the carbon fibers and a process for producing the acrylic fibers.

Carbon fibers, acrylic fibers and process for producing the acrylic fibers

Disclosed are carbon fibers consisting of a plurality of single filaments, wherein the carbon fibers as a resin impregnated strand are characterized by satisfying the following relations: &sgr;&gE;11.1-0.75d where &sgr; is the tensile strength of said carbon fibers as a resin impregnated strand in GPa, and d is the average diameter of said single filaments in &mgr;m, and RD&gE;0.05 where RD is the difference in crystallinity between the inner and outer layers of each of the single filaments evaluated with RAMAN, and an acrylic fibers for producing the carbon fibers and a process for producing the acrylic fibers.

Carbon fibers, acrylic fibers, and production processes thereof

Prepregs and carbon fiber-reinforced composite materials

Carbon fibers with a surface oxygen concentration (O/C ratio) of 0.20 or less as measured by X-ray photoelectron spectroscopy, a surface concentration of hydroxyl groups (C--OH/C ratio) of 0.5% or greater as measured by chemical modification X-ray photoelectron spectroscopy and a surface concentration of carboxylic groups (COOH/C ratio) of 2.0% or less as measured by chemical modification X-ray photoelectron spectroscopy, and an aliphatic compound applied as a sizing agent which has multiple epoxy groups or an aromatic compound which has multiple epoxy groups, the number of atoms between the epoxy groups and an aromatic ring being 6 or greater.

Carbon fibers and process for preparing same

A process for preparing carbon fibers including electrolyzing a carbon fiber in an alkaline aqueous solution, or electrolyzing a carbon fiber in an acidic aqueous solution followed by washing with an alkaline aqueous solution, and then applying a sizing agent of an aliphatic compound with multiple epoxy groups or an aromatic compound with multiple epoxy groups in which the number of atoms between the epoxy groups and an aromatic ring is 6 or greater. Alternatively, the carbon fibers are prepared by electrolyzing a carbon fiber in an aqueous solution of an ammonium salt and then applying a sizing agent of an aliphatic compound with multiple epoxy groups or an aromatic compound with multiple epoxy groups in which the number of atoms between the epoxy groups and an aromatic ring is 6 or greater.

Method for preparing carbon fibers

Carbon fibers with a surface oxygen concentration (O/C ratio) of 0.20 or less as measured by X-ray photoelectron spectroscopy, a surface concentration of hydroxyl groups (C-OH/C ratio) of 0.5% or greater as measured by chemical modification X-ray photoelectron spectroscopy and a surface concentration of carboxylic groups (COOH/C ratio) of 2.0% or less as measured by chemical modification X-ray photoelectron spectroscopy, and an aliphatic compound applied as a sizing agent which has multiple epoxy groups or an aromatic compound which has multiple epoxy groups, the number of atoms between the epoxy groups and an aromatic ring being 6 or greater.

Carbon fibers with a surface oxygen concentration (O/C ratio) of 0.20 or less as measured by X-ray photoelectron spectroscopy, a surface concentration of hydroxyl groups (C--OH/C ratio) of 0.5% or greater as measured by chemical modification X-ray photoelectron spectroscopy and a surface concentration of carboxylic groups (COOH/C ratio) of 2.0% or less as measured by chemical modification X-ray photoelectron spectroscopy, and comprising applied as a sizing agent an aliphatic compound which has multiple epoxy groups or an aromatic compound which has multiple epoxy groups, the number of atoms between the epoxy groups and an aromatic ring being 6 or greater. They are prepared by electrolyzing a carbon fiber in an alkaline aqueous solution, or electrolyzing a carbon fiber in an acidic aqueous solution followed by washing with an alkaline aqueous solution, and then applying a sizing agent of an aliphatic compound with multiple epoxy groups or an aromatic compound with multiple epoxy groups in which the number of atoms between the epoxy groups and an aromatic ring is 6 or greater. Alternatively, they are prepared by electrolyzing a carbon fiber in an aqueous solution of an ammonium salt and then applying a sizing agent of an aliphatic compound with multiple epoxy groups or an aromatic compound with multiple epoxy groups in which the number of atoms between the epoxy groups and an aromatic ring is 6 or greater.

Disclosed is a carbon fiber made from an acrylic fiber, the carbon crystal of which has a crystal size Lc of 15 to 65 .ANG. as determined by the wide angle X-ray diffractometry. This carbon fiber has regions with a lower crystallinity in the surface layer portion thereof than that of the central portion thereof, and the compressive strength .sigma..sub.cf (GPa) of the single filament thereof determined by the loop method satisfies formula (I):

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Ehime, Japan

Yoji Matsuhisa