Wool fabrics shrinking

To produce easy care wool—polyester blend garments, heat setting of the polyester component will impart set stability to repeated machine washing. A minimum of 20—30% polyester is needed for adequate stability. A fabric shrink-resist treatment such with Synthappret BAP may be necessary to give the required shrink-resistance for easy cate performance. If the polyester content is increased, particularly above 50%, and a suitable fabric constmction is used, heat setting alone will give easy care performance. 

It is more difficult to produce pure wool easy care garments. The problem is to obtain adequate durability of the setting rather than obtaining shrink-resistance, because some wool setting processes are not stable to machine washing. As of ca 1997, the best approach is to combine the Synthappret BAP fabric shrink-resist process with Siroset garment setting. 

The particular requirements of shrink-resist processes in relation to wool fabric printing have been described [312]. In addition to dimensional stability, there is a need for ease of... 

Wool is a natural protein fiber characterized by the scaly structure of its external surface-cuticle (Fig. 1). This structure, i.e. the stiffness of cuticle and smoothness of the epicuticle as well as the ability of wool to contract, causes the shrinking of wool fabric during mechanical washing processes. 

Finishing Wool Fabrics. The fundamental chemical structure of the wool fiber, together with its fiber morphology, impose an entirely different procedure in finishing wool fabrics than that outlined for the cellulosic fiber fabrics. Wool is sensitive to strong alkali, the fiber shrinks markedly with wetting, and the fiber felts under a suitable combination of mechanical work, chemical action, moisture, and heat. 

J. (2007) Improvement of shrink-resistance and tensile strength of wool fabric treated with a novel microbial transglutaminase from Streptomyces hygroscopicus. Enzyme Microb. Technol, 40 (7), 1753-1757. 

Mechanical action during scouring or washing causes fabrics made from untreated wool to shrink or felt. The application [13,258,264] of one of a number of polymers to wool fabrics... 

It is possible to treat wool fibers with polymer before they are spun into yarn in a way that will ensure that the resulting fabric is shrink-proof. In such cases, it is necessary to cover a significant portion of the fiber surface with polymer. It is thought that this masks the cuticular cells, or scales, on the fibers and prevents the ratchet elTect of the scales, all of which point in the same direction along a fiber and are thought to be responsible for the felting of wool fabrics. 

Additive Shrink-Resist Treatments. The principal additive shrink-resist treatment for wool fabrics uses the polymer Synthappret BAP (Bayer AG). This is a poly(propylene oxide) polyurethane, containing reactive carbamoyl sulfonate (bisulfite adducts of isocyanate) groups, ie —NHCOSOa" Na" ". An aqueous solution of this polsrmer is padded onto woven fabrics. The polymer cross-links on drying to form flexible linkages between fibers and yams (101). Other polymers may be applied at the same time to modify the handle. 

Textile Finishing. Polyethyleneimine-A/-methylolurea derivatives improve the crease and wear resistance of cotton (429,430). The adhesion between individual wool fibers is improved by pretreatment with amines, which leads to improved shrink resistance (431). An antimicrobial finish can be appHed to cotton by using a combination of PEI and ureas to bind zinc pyrithione to the fabric (432). After wool has been provided with a flameproof finish using fluorozirconate or fluorotitanate, the wool can be neutralized with PEI (433). Conventional neutralizing agents caimot be used for this purpose since they impair the flameproof characteristics of the impregnated fabric. 

Fig. 8. Electron micrograph of Merino wool fibers in a fabric that have been treated with a typical shrink-resistance polymer, showing fiber—fiber bond...

Enzymes can be used to modify the surface of wool fibres in order to improve lustre, softness, smoothness or warmth of the fabric. Since such processes involve attack on the cuticular scales of the fibre, there is clearly a resemblance to shrink-resist treatments and similar methods are used [116] ... 

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