Abstract: A fiber including olefin-based resin, wherein temperatures of the olefin-based resin losing five percent by weight and the fiber losing five percent by weight have a difference of 20 degrees Celsius or below according to thermogravimetric measurements.

Abstract: A fiber including olefin-based resin, wherein temperatures of the olefin-based resin losing five percent by weight and the fiber losing five percent by weight have a difference of 20 degrees Celsius or below according to thermogravimetric measurements. The fiber can reduce the leaching of impurities with low molecular weight by controlling the deterioration of olefin-based resin when heated during its spinning process.

Abstract: The present invention provides a semi-aromatic polyamide fiber having acid resistance and further having excellent long-term heat resistance and good spinning properties. The semi-aromatic polyamide fiber contains a semi-aromatic polyamide resin having a melting point of 280° C. or less and satisfies all of the following conditions (1) to (3): (1) in the semi-aromatic polyamide, a dicarboxylic acid component is an aromatic dicarboxylic acid, and 40 mol % to 80 mol % of a diamine component is 2-methyl-1,8-octanediamine; (2) the semi-aromatic polyamide comprises 50 ppm to 500 ppm of a copper compound in terms of copper; and (3) the semi-aromatic polyamide fiber has a peak temperature of a glass transition point from 120° C. to 140° C.