Effects of Dyeing and Finishing on Hygral Expansion and Other Crimp-Dependent Physical Properties of Wool Fabrics

Abstract

Low stress tensile properties as measured by KESF instruments—hygral expansion, relaxation shrinkage, and the crimp of the yarns in a fabric—were determined for a pure wool fabric after each of a number of dyeing and finishing processes. The dyeing recipes and dyes cover the range for wool in industry. Dye-fiber interactions were evaluated by comparing the properties of dyed fabrics with those of blank dyed controls. Dyeing and finishing alter many mechanical and physical properties of a fabric by changing the crimp of its yams, due to stress relaxation of interyarn forces in the unfinished fabrics during processing. The degree to which the initial interyarn stresses are relaxed is also an important parameter. Acid and chrome dyes did not affect the resulting fabric properties, but reactive dyes often had a dramatic effect on changes that took place during piece dyeing. Reactive dye-fiber interactions altered fabric crimp as a result of dyeing. In turn, crimp differences affected the resulting crimp-dependent fabric properties—hygral expansion and low-stress tensile properties. The effect was resistant to decatizing. This result has beneficial implications for controlling hygral expansion.