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.

Wear Attributes of Cashmere Single Jersey Knitted Fabrics Blended with High and Low Crimp Superfine Merino Wool

“…Hygral expansion is caused by a change in fabric regain, and is reversible. Since the fashion for lightweight allseasons fabrics began, the study of hygral expansion has assumed much greater importance [30].…”

“…Hygral expansion is affected by finishing procedures, including the types of dyes used. Finishing procedures affect yarn crimp by moderating stress relaxation [30].…”

Changes in the Chemical Composition of Wool During Dyeing and Finishing and Their Effects on Fabric Properties

“…The method is based on the selective reaction of wool thiol with mercuric chloride ( HgCl2 ) , and is more laborious than some of its alternatives, but there were several practical reasons for its choice in our particular situation [4]. We also determined the extent of reaction by analysis of Hg using AAS.…”

“…Our previous work reported the dramatic effect of reactive dye-fiber interactions on crimp dependent mechanical properties of wool fabrics [ 5 ] . Only reactive dyes affected wool fabric mechanical properties.…”

“…Thermosetting refers to kier decatizing using the Sellers Thermoset kier decatizer, while superfinishing refers to decatizing using the Menschner Superfinish-2 continuous decatizing machinery. These machines have been described in detail elsewhere [4]. Superfinished or thermoset fabrics are ready for piece dyeing.…”