Abstract: An aromatic polyamide fiber comprising an aromatic polyamide containing a structural repeating unit of the following formula (1), and a structural repeating unit of the following repeating unit (2) in an amount of 30 mol % or more to the whole amount of the aromatic polyamide structural units, the fiber having strength of 20 cN/dtex or more and modulus of elongation of 500 cN/dtex or more: wherein Ar1 and Ar2 each independently represent an unsubstituted or substituted divalent aromatic group.

Abstract: The heterocycle-containing aromatic polyamide fibers of the invention are excellent in balance among mechanical characteristics, particularly balance among tensile strength, initial modulus and strength in the direction perpendicular to the fiber axis, exhibit a high strength holding ratio under heat and humidity, and are excellent in flame retardancy, bulletproofness and cutting resistance, as compared to conventional aromatic polyamide fibers, and therefore can be favorably used in fields with severe mechanical characteristics and have stability to environmental variation. Accordingly, the heterocycle-containing aromatic polyamide fibers of the invention can be favorably used, for example, in fields including protective equipment, such as a helmet, a bulletproof vest and the like, a chassis for an automobile, a ship and the like, an electric insulating material, such as a printed circuit board and the like, and other various fields.

Abstract: An aromatic polyamide fiber comprising an aromatic polyamide containing a structural repeating unit of the following formula (1), and a structural repeating unit of the following repeating unit (2) in an amount of 30 mol % or more to the whole amount of the aromatic polyamide structural units, the fiber having strength of 20 cN/dtex or more and modulus of elongation of 500 cN/dtex or more: wherein Ar1 and Ar2 each independently represent an unsubstituted or substituted divalent aromatic group.