The Dimensional Properties of Knitted Wool Fabrics

Abstract

Dimensionally stable, machine-washalle, all-wool interlock and Swiss double-piqué fabrics may be guaranteed if the yarns have been adequately treated against felting and the fabrics fully-relaxed. The practical fully-relaxed state of the Swiss double-piqué structure is attained when the fabrics have been thoroughly wetted, hydroextracted, and tumble-dried for at least 1 hr at 70°C. From this fabric state, dimensional changes in machine-washing and tumble-drying for high shrink-resist-treated yarns over a period of 10 cycles lie within the allowable limits of ±8% area and ±5% linear shrinkage limits. This relaxation process is, however, insufficient to contain relaxation shrinkage of the interlock structure. In washing from this state, linear shrinkages greater than ±5% are often found. Because in machine-washing the majority of residual relaxation occurs in the initial wash, at least two tumble-drying relaxation processes may be required to practi cally inhibit relaxation shrinkage of the interlock structure. But an effect of yarn twist on the geometry of the inter lock structure is listed.

Fabric dimensions in a relaxed state are dependent upon yarn, fabric, and machine variables. Dimensions in the fully- relaxed state are, however, for both structures, essentially independent of these variables and predictable by constants whose values are different for each structure.

The dimensional behavior of the interlock structure in washing is anisotropic,³ i.e., a length shrinkage is usually asso ciated with a width expansion, whereas the Swiss double-piqué structure behaves isotropically, ³ i.e., length and width shrinkages are usually found. It is proposed that the difference in dimensional behavior between these structures is due to the dissimilar nonrelaxed geometrical shapes of the individual structural units forming these two double-knit structures.