The Dimensional Properties of Knitted Wool Fabrics

Abstract

The first paper of this series proposed and defined a means of attaining the fully-relaxed state of plain-knit fabric. This paper establishes the validity of this definition, which is shown to essentially discriminate relaxation shrinkage, due only to loop relaxation, from felting fiber migration to a more compact state without loop distortion. This discrimination is achieved by analyzing dimensions of the fabrics through 10 wash and tumble-dry cycles. We find that area shrinkage from any stage in processing to the fully-relaxed state depends on loop length and yarn count and, to a lesser extent, on fiber quality and yarn twist. Analysis of the dimensional changes from the fully-relaxed state through multiple washing and tumble-drying cycles shows: (1) for yarns spun from WURLAN shrink resist-treated top, area shrinkage increases linearly with the number of wash and tumble-dry cycles, but nonlinearly for untreated yarns; (2) for untreated yarns, shrinkages in length, width, and area depend on fiber quality, yarn twist, and loop length, with complex interactions among these variables; (3) at a low treatment level, linear and area shrinkages depend to a smaller extent on all these variables; (4) at a high treatment level, the WURLAN treatment adequately restricts felting to within an acceptable 8% area shrinkage limit; in this case, changes in length, width, and area from the fully-relaxed state are independent of all fiber, yarn, and fabric variables studied. We also find that change in length and width from the dry-relaxed to the fully relaxed state depends greatly on loop length, to a minor extent on fiber quality and yarn twist, and not at all on treatment level. These changes were always isotropic, that is, dimensions always decreased during relaxation.