Abstract: A method for a fiber bundle, including a heating process of Joule-heating the fiber bundle by energization between at least a pair of electrodes. The fiber bundle is carried in contact with the electrodes and has electrical conductivity at least between the electrodes. At least one of the electrodes has an aggregating structure that aggregates the fiber bundle while being in contact with the outer surface of fiber bundle. The aggregating structure has a trench or cylindrical shape with a structural surface that narrows in the depth direction. When the electrodes are each composed of a rotating body, the aggregating structure is a trench provided on the outer surface of the rotating body. The trench has a bottom surface that narrows toward a rotation center side. The trench may have a widened portion on the outer peripheral edge side. The widened portion guides the fiber bundle to the bottom surface.

Abstract: Addressed is the object of improving an unwinding performance of a glass direct roving at an end surface. A method of manufacturing a glass direct roving includes winding a glass strand into a cylindrical shape while traversing the glass strand. In the winding, the glass strand is wound traversing the glass strand under the conditions that a wind order of the crosswindng is or greater, and an interval parameter, which is the smaller value among “b” and “A?b”, is from “(A/2)*?(A/4)*” to “(A/2)*?1”, where “A” is the wind order, “(A/2)*” is a maximum integer no greater than ½ the wind order, “(A/4)*” is a maximum integer no greater than ¼ the wind order, and a mixed fraction “a+(b/A)” is used to express a cyclewind of the crosswindng.

Abstract: The carbon fiber precursor fiber of the disclosure includes an acrylamide-based polymer fiber; and a self-crosslinked product of a self-crosslinking silicone oil on a surface of the acrylamide-based polymer fiber.

Abstract: The carbon fiber precursor contains a crosslinked acrylamide-based polymer and has a gel fraction of 5% or more.

Abstract: One aspect of the present disclosure relates to a method for manufacturing a spun yarn made of carbon nanotubes. The method includes: a spun yarn precursor ? production step of producing a spun yarn precursor ? by pulling a plurality of carbon nanotubes from a carbon nanotube forest and spinning the carbon nanotubes while applying a tension of 6 mN or less per centimeter of a width of the carbon nanotube forest to the carbon nanotubes; a spun yarn precursor ? production step of producing a spun yarn precursor ? by applying a higher tension than in the spun yarn precursor ? production step to the spun yarn precursor ? to densify the spun yarn precursor ?; and a spun yarn production step of producing the spun yarn by electrically heating the spun yarn precursor ? while applying a tension to the spun yarn precursor ?.

Abstract: Provided is a method for producing a glass direct roving that has excellent workability and can effectively increase the mechanical strength of a composite material obtained by combination with resin. A method for producing a glass direct roving 10 formed by directly winding up a bundle of glass filaments includes the steps of: applying a sizing agent containing an epoxy resin having an epoxy equivalent of 180 to 240 to surfaces of a plurality of glass filaments to bundle the plurality of glass filaments; winding up a bundle obtained by bundling the plurality of glass filaments, thus making a wound package; and thermally drying the sizing agent at a temperature of 135° C. to 155° C. to form a coating on the surfaces of the glass filaments.

Abstract: A carbon fiber wherein an average fiber diameter of a single fiber is in a range of 3 to 10 ?m, and an average value of an intensity ratio (D/G) of a D peak to a G peak in a Raman spectrum in a cross section perpendicular to a fiber axis direction of the single fiber is 0.90 or less in a region inside a circle having a diameter of 1 ?m and centered at a center of gravity of the cross section of the single fiber, and is 0.90 or less in a region up to 1 ?m inside from an outer periphery of the cross section of the single fiber, wherein the D peak is observed at around 1360 cm?1 and derived from a defect in a graphite structure and the G peak is observed at around 1590 cm?1 and derived from the graphite structure.