Abstract: This invention provides a sizing agent for carbon fiber which contains an isocyanate regenerating compound which is an isocyanate compound, the --NCO group of which is stabilized with a blocking agent. Further provided are carbon fiber improved in adhesion to resins and carbon fiber reinforced composite materials improved in various properties such as tensile strength, flexural strength and Izod impact strength.

Abstract: The present invention relates to a carbon fiber having a novel structure in which the outer circumferential part of fiber section is constituted of an optically isotropic component and its central part is constituted of an optically anisotropic component or an optically anisotropic component partially containing optically isotropic component, which the carbon fiber shows no cracks at all, as well as to a process for producing said carbon fiber.

Abstract: The present invention relates to a process for producing a carbon fiber chopped strand which comprises preparing a pitch fiber from petroleum pitch or coal pitch, cutting the pitch fiber to a predetermined desired length, heating the cut pitch fiber at a high density accumulation in the atmosphere of an oxidative gas to infusibilize the cut pitch fiber, and then carbonizing and graphitizing the infusibilized fiber in an inert atmosphere. According to the process of the invention, no fuzz are formed on the fiber and no uneven infusibilization takes place. Further, the pitch fiber chopped strand accumulation has a high bulk density and relieve exothermic excursion naturally, and therefore neither combustion nor sticking takes place even in an oxidative atmosphere. Accordingly, the production speed can be enhanced and the cost can be lowered to a great extent.

Abstract: Disclosed is a method for producing carbon fiber chopped strands excellent in bundling of fibers, high in bulk density, uniform in fiber length and superior in molding operability which includes application of an inorganic and/or organic binder in an amount of 0.1-3% by weight in terms of solid to carbon fiber or graphite fiber strands or chopped strands made from a petroleum or coal pitch.

Abstract: This invention provides a process for coating chopped strand of glass fiber with a thermosetting resin in an individually separated state which comprises dispersing chopped strand of glass fiber impregnated with a solution of thermosetting resin into an aqueous medium and then carrying out a removal of solvent. By this process, a pellet-formed glass fiber base material thickly coated with said thermosetting resin and free from filamentation and fuzzy of glass fiber can be obtained by a simple procedure.