Hydrothermal Setting of Wool-Polyester Blend Fabrics

Abstract

Hydrothermal setting techniques (setting in the presence of water) were used to stabilize wool-polyester blends to piece dyeing. The resultant dyed and finished fabrics differed in several respects from those that were heat set prior to dyeing. Hydrothermal setting generally produced fabrics that were thinner and smoother than those that were heat set, giving the fabrics a smoother and "cooler" feel. The method used to achieve hydrothermal setting also had a considerable influence on the subsequent properties of the fabrics, particularly the tensile properties. Under the conditions used, the tailoring performance of heat set fabrics was marginally superior to that of the hydrothermally set fabrics, but again the extent of the difference depended on the conditions of setting.Wool-polyester fabrics are set at several stages during finishing from loom state to the final form ready for sale to the garment manufacturer. Loom state fabrics are set to relieve strains remaining in the fibers and yams after weaving, which may result in fabric distortion in later processing. Fabrics are also set after scouring and, where applicable, after dyeing to give the fabric additional flat stability.The procedures used to set fabrics have important implications not only for the flat stability of the fabric, but also for the dyeing properties [ 12] and subsequent handle and tailoring characteristics of the finished fabric. Consequently, the effectiveness of any change in the conditions used to set fabrics prior to dyeing must be assessed on not only the propensity of fabric to form rig marks or crows feet, but also the effect on dye uptake by the various component fibers, the subsequent processing performance of the fabric, and the mechanical properties of the fabric affecting handle and tailorability.The chemistry of setting wool and polyester fibers is well understood, and a number of techniques are available to exploit the more recent advances in setting technology. Setting of wool involves rearrangement of both hydrogen and disulphide bonds in the fiber [13]. Such rearrangements occur rapidly in the presence of heat, moisture, and reagents that break disulphide bonds (e.g., reducing agents). Setting of polyester, on the other hand, requires rearrangement of nonpolar bonds and dipolar interactions associated with the ester groups in the macromolecules [ 12]. Polyester may be set by the action of heat alone, although a variety of reagents will plasticize the fiber and facilitate the various rearrangements. These reagents include water, generally in the form of steam, and some phenols.Most piece dyed wool-polyester blend fabrics are heat set (set using hot air at 150-190°C) prior to dyeing to stabilize the polyester component. This operation does not set the wool component of the blend; however, because both the wool and polyester fibers are set in the presence of steam [ I I ] (called hydrothermal setting), pressure decatizing and crabbing [9] offer alternative approaches to the setting of wool-polyester blend fabrics before dyeing...

Thermal behaviour of heat treated polyester knitted fabrics

“…Polyester fabrics are set at various stages from machine state to final finished fabric and sometimes during garment processing (De Boos et al, 1986). The setting temperature varies with the fibre and end usage of the fabric.…”

“…The setting temperature varies with the fibre and end usage of the fabric. Heat setting machines available in the finishing industry may also be classified depending on the type of reagent used to stabilize polyester (De Boos et al, 1986;Marvin, 1954;Mecklenburgh, 1950;Preston et al, 1951). During heat setting, the tensions are highly variable, from being very high when the sample is constrained from shrinking to being very low when it is free to relax (Gupta, 1995).…”