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.

To provide a carbon fiber precursor fiber that can efficiently produce a carbon fiber excellent in mechanical strength without an infusibilization treatment; a carbon fiber; and a method for producing the carbon fiber. The carbon fiber precursor fiber includes a polymer represented by General Formula (1) below: ##STR00001## where in the General Formula (1), Ar.sub.1 represents an aryl group expressed by any one of Structural Formulas (1) to (5) below, and Ar.sub.2 represents an aryl group expressed by Structural Formula (6) or (7) below: ##STR00002##

To provide a carbon fiber precursor fiber that can efficiently produce a carbon fiber excellent in mechanical strength without an infusibilization treatment; a carbon fiber; and a method for producing the carbon fiber. The carbon fiber precursor fiber includes a polymer represented by General Formula (1) below: ##STR00001## where in the General Formula (1), Ar.sub.1 represents an aryl group expressed by any one of Structural Formulas (1) to (5) below, and Ar.sub.2 represents an aryl group expressed by Structural Formula (6) or (7) below: ##STR00002##

Spun ABPBI fibers and a process for the preparing spun ABPBI fibers using a high molecular weight ABPBI dope solution suitable for spinning are provided. A process for preparing the high molecular weight ABPBI dope solution suitable for spinning is also provided. The spun ABPBI fibers can be used in the preparation of high temperature thermally resistant articles.

Spun ABPBI fibers and a process for the preparing spun ABPBI fibers using a high molecular weight ABPBI dope solution suitable for spinning are provided. A process for preparing the high molecular weight ABPBI dope solution suitable for spinning is also provided. The spun ABPBI fibers can be used in the preparation of high temperature thermally resistant articles.

Disclosed in the present invention are 4-(5-amino-6-hydroxybenzoxazol-2-yl)ammonium benzoate shown in formula (I) and the preparation method and use thereof. The preparation method comprises: fully reacting 4-(5-amino-6-hydroxybenzoxazol-2-yl)benzoic acid shown in formula (II) or 4-(5-amino-6-hydroxybenzoxazol-2-yl)carboxamide benzoate, as a raw material, with ammonia in an aqueous solvent, and directly heating the obtained reaction liquid to remove excess ammonia, so as to obtain 4-(5-amino-6-hydroxybenzoxazol-2-yl)ammonium benzoate. The mass of the 4-(5-amino-6-hydroxybenzoxazol-2-yl)ammonium benzoate (ABAA) prepared in the present invention can reach a polymer grade (where the purity is above 99.5%, the content of metal ions is below 200 ppm, and containing no DMF polymerization inhibition impurities), and the 4-(5-amino-6-hydroxybenzoxazol-2-yl)ammonium benzoate can be used as an AB type monomer for preparing PBO and modified PBO fibers, the resulting PBO having an intrinsic viscosity ηof up to 38/dl/g, and the method has such features as ABAA being highly soluble in PPA, a fast polymerization speed, a short time of 2-4 h, a low temperature of 150° C., a high molecular weight of the polymer, fibers of excellent tensile property, being easy to industrialize, etc.

Disclosed in the present invention are 4-(5-amino-6-hydroxybenzoxazol-2-yl)ammonium benzoate shown in formula (I) and the preparation method and use thereof. The preparation method comprises: fully reacting 4-(5-amino-6-hydroxybenzoxazol-2-yl)benzoic acid shown in formula (II) or 4-(5-amino-6-hydroxybenzoxazol-2-yl)carboxamide benzoate, as a raw material, with ammonia in an aqueous solvent, and directly heating the obtained reaction liquid to remove excess ammonia, so as to obtain 4-(5-amino-6-hydroxybenzoxazol-2-yl)ammonium benzoate. The mass of the 4-(5-amino-6-hydroxybenzoxazol-2-yl)ammonium benzoate (ABAA) prepared in the present invention can reach a polymer grade (where the purity is above 99.5%, the content of metal ions is below 200 ppm, and containing no DMF polymerization inhibition impurities), and the 4-(5-amino-6-hydroxybenzoxazol-2-yl)ammonium benzoate can be used as an AB type monomer for preparing PBO and modified PBO fibers, the resulting PBO having an intrinsic viscosity ηof up to 38/dl/g, and the method has such features as ABAA being highly soluble in PPA, a fast polymerization speed, a short time of 2-4 h, a low temperature of 150° C., a high molecular weight of the polymer, fibers of excellent tensile property, being easy to industrialize, etc.

Provided are an amorphous polyetherimide fiber having not only a small single fiber fineness suitable for producing fabrics, and a fabric comprising the amorphous polyetherimide fiber. The fiber comprises an amorphous polyetherimide polymer having a molecular weight distribution (Mw/Mn) of less than 2.5, and having a shrinkage percentage under dry heat at 200° C. of 5% or less, and a single fiber fineness of 3.0 dtex or less. The fiber may have a tenacity at room temperature of 2.0 cN/dtex or greater.

Provided are an amorphous polyetherimide fiber having not only a small single fiber fineness suitable for producing fabrics, and a fabric comprising the amorphous polyetherimide fiber. The fiber comprises an amorphous polyetherimide polymer having a molecular weight distribution (Mw/Mn) of less than 2.5, and having a shrinkage percentage under dry heat at 200° C. of 5% or less, and a single fiber fineness of 3.0 dtex or less. The fiber may have a tenacity at room temperature of 2.0 cN/dtex or greater.

A composite electrode includes two or more types of fibers forming a fiber network, comprising at least a first type of fibers and a second type of fibers. The first type of fibers comprises a first polymer and a first type of particles. The second type of fibers comprises a second polymer and a second type of particles. The second polymer is same as or different from the first polymer. The second type of particles are same as or different from the first type of particles.