Described herein are polyphenylene fibers. The polyphenylene fibers have one or more polyphenylene polymers. The polyphenylene fibers can further include one or more poly(aryl ether sulfone) polymers. In some embodiments, the polyphenylene fibers can have an average diameter that is less than about 1 micron. The polyphenylene fibers can have desirable mechanical properties. Also described herein are methods for forming polyphenylene fibers. In some embodiments, the fibers can be fabricated using specifically engineered polymer solutions in conjunctions with adapted force spinning techniques.

A manufacturing method for a transparent fiber is provided. The method includes forming a spinning solution containing a polyimide polymer in an organic solvent. The polydispersity index (PDI) of the polyimide polymer is 1.3˜2.6. The spinning solution is used to perform a dry-jet wet spinning step to form a plurality of fibers. Furthermore, the plurality of fibers are subjected to a thermal drawing step to form a plurality of transparent fibers, wherein the temperature of the thermal drawing step is controlled from 215° C. to 350° C. The manufacturing method for a transparent fiber provided in the present invention makes use of a polyimide polymer material and utilizes a dry-jet wet spinning step and a thermal drawing step, which allows the formation of a transparent and high strength polyimide fiber.

A manufacturing method for a transparent fiber is provided. The method includes forming a spinning solution containing a polyimide polymer in an organic solvent. The polydispersity index (PDI) of the polyimide polymer is 1.3˜2.6. The spinning solution is used to perform a dry-jet wet spinning step to form a plurality of fibers. Furthermore, the plurality of fibers are subjected to a thermal drawing step to form a plurality of transparent fibers, wherein the temperature of the thermal drawing step is controlled from 215° C. to 350° C. The manufacturing method for a transparent fiber provided in the present invention makes use of a polyimide polymer material and utilizes a dry-jet wet spinning step and a thermal drawing step, which allows the formation of a transparent and high strength polyimide fiber.

The present invention provides a polyimide solution which does not require a ring-closing process at a high temperature for obtaining a heat-resistant polyimide non-woven fabric and which is hardly affected by atmosphere humidity in fiber production by electrospinning, so that a fiber with a stable diameter can be obtained in any circumstance.

A polyimide solution including: (a) a resin containing 50 mol % or more, based on the total amount of the resin, of a structural unit represented by the general formula (1); and (b) a solvent.

##STR00001##

The present invention provides a polyimide solution which does not require a ring-closing process at a high temperature for obtaining a heat-resistant polyimide non-woven fabric and which is hardly affected by atmosphere humidity in fiber production by electrospinning, so that a fiber with a stable diameter can be obtained in any circumstance.

A polyimide solution including: (a) a resin containing 50 mol % or more, based on the total amount of the resin, of a structural unit represented by the general formula (1); and (b) a solvent.

##STR00001##

[Problem] To provide: a carbon fiber precursor fiber that can efficiently produce a carbon fiber at a low cost which is excellent in mechanical strengths even without an infusibilization treatment; a carbon fiber; and a method for producing the carbon fiber.

[Solution] A carbon fiber precursor fiber of the present invention includes a polymer containing a constituent unit represented by General Formula (1) below:

##STR00001## where in the General Formula (1), X and Y each independently represent a divalent substituent, a single bond, or a structure forming a fused ring by sharing one side of two adjacent rings, and the divalent substituent is selected from the group consisting of —O—, —S—, —OSO—, —NH—, —CO—, —CH.sub.2—, and —CH(CH.sub.3).sub.2—.

[Problem] To provide: a carbon fiber precursor fiber that can efficiently produce a carbon fiber at a low cost which is excellent in mechanical strengths even without an infusibilization treatment; a carbon fiber; and a method for producing the carbon fiber.

[Solution] A carbon fiber precursor fiber of the present invention includes a polymer containing a constituent unit represented by General Formula (1) below:

##STR00001## where in the General Formula (1), X and Y each independently represent a divalent substituent, a single bond, or a structure forming a fused ring by sharing one side of two adjacent rings, and the divalent substituent is selected from the group consisting of —O—, —S—, —OSO—, —NH—, —CO—, —CH.sub.2—, and —CH(CH.sub.3).sub.2—.

The present invention relates to a method for manufacturing carbon composite fibers and carbon nanofibers, and more particularly, to a method for manufacturing carbon composite fiber with greatly improved specific tensile strength, specific modulus, electrical conductivity, and thermal conductivity.

The present invention relates to a method for manufacturing carbon composite fibers and carbon nanofibers, and more particularly, to a method for manufacturing carbon composite fiber with greatly improved specific tensile strength, specific modulus, electrical conductivity, and thermal conductivity.

The method for producing a polyimide fiber includes a coagulation step of forming a polyimide precursor fiber by extruding a polyimide precursor solution containing a polyimide precursor and a compound having an acid dissociation constant (pKa) of a conjugate acid in water at 25° C. of 6.0 to 10 inclusive and an octanol-water partition coefficient (Log P) at 25° C. of −0.75 to 0.75 inclusive into a poor solvent or nonsolvent for the polyimide precursor; and a heat drawing step of forming the polyimide fiber by drawing the polyimide precursor fiber while heating same. The polyimide fiber of the present disclosure has a physical property such that the coefficient of thermal expansion thereof is in the range of −15 ppm/K to 0 ppm/K inclusive.