Mechanical properties, moisture absorption, and dyeability of polyamide 5,6 fibers

Polyamide 5,6 (PA56) and polyamide 6 (PA6) fibers were spun by melt spinning process and drawn by a thermal drawing in order to improve their mechanical properties. The effects of drawing conditions on mechanical properties, moisture absorption, and dyeing behavior were investigated by means of tensile testing measurements, moisture absorption test, as well as color strength measurements. It was found that the tenacity and Young's modulus were significantly increased, while the elongation at break decreased as the draw ratio (DR) and temperature increased due to the increase in molecular orientation along the fiber axis and the crystallinity. PA56 fibers showed a little lower mechanical properties and much higher moisture regain than PA6 fibers at different DRs. This can be attributed to the amide group content in the polymer backbone, which yields higher moisture regain in PA56 fibers than PA6 fibers. The dyeing behaviors of PA56 fiber, in terms of dyebath exhaustion, color strength, and wash fastness are similar as those of PA6. Those results indicated that PA56 is a competitive novel fiber for textile material.