Propylene polymer fibers and yarns

A process for treating a textile product comprising providing a textile product comprising fibers comprising propylene polymer and heating the textile product with the fibers in a substantially relaxed state at at least one heat treating temperature below but within about 20.degree. C. of the melting temperature of the propylene polymer, wherein said fibers comprising propylene polymer are selected from the group consisting of (1) fibers characterized by small angle X-ray diffraction such that an average of ##EQU5## with the fiber positioned such that its longitudinal axis is inclined at angles, .alpha., of 10.degree. and 20.degree. from a perpendicular to the X-ray beam is at least about 200 .ANG., wherein

• I.sub.m (0) is maximum intensity of the small angle X-ray meridional reflection with the fiber positioned such that its longitudinal axis is perpendicular to the X-ray beam,
• I.sub.m (.alpha.) is maximum intensity of the small angle X-ray meridional reflection with the fiber positioned such that its longitudinal axis is inclined at the angle, .alpha., from the perpendicular to the X-ray beam, ##EQU6## .phi..sub.m is an angular position, in radians, of the center of the small angle X-ray meridional reflection at half height relative to the center of the incident X-ray beam with the fiber positioned such that its longitudinal axis is perpendicular to the X-ray beam,
• and wherein the small angle X-ray diffraction is conducted with CuK.alpha. radiation having a wavelength of 1.5418 .ANG. and the X-ray beam is slit collimated to an angular width at half height of 1.81 minutes, and (2) melt spun, oriented fibers heated at at least one temperature lower than the heat treating temperature and about 20 to about 40.degree. C. below the melting temperature of the propylene polymer with the fibers in a substantially relaxed state.