| 摘要 |
To provide a polyamide fiber such as polyhexamethylene adipamide fiber having high tenacity and excellent tenacity retention after vulcanization and GY fatigue life. This fiber is a high tenacity polyamide fiber, preferably a polyhexamethylene adipamide fiber comprising at least 95% by mole of hexamethylene adipamide units and having a sulfuric acid relative viscosity of at least 3.0, said polyamide fiber satisfying the requirements: (a) differential birefringence .delta..DELTA.n ? -5 x 10-3 to 0 x 10-3, (b) long period (Dm) in the direction of fiber axis: Dm ? 105 A, and long period (De) in the radical direction of fiber: De = 90 to 130 A, (c) main dispersion peak temperature (T.alpha.) in mechanical loss tangent (tan.delta.) curve as obtained by viscoelastic measurement: T.alpha. ? 125.degree.C, and preferably further satisfying the requirements: (d) birefringence .DELTA.n ? 60 x 10-3, (e) crystal orientation function fc ? 0.88, and (f) amorphous orientation function fa = 0.70 to 0.85. |
