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A letter to the editor about the geometry of relaxed wool double-jersey structures is presented.

The dimensional behaviour of five non-jacquard wool double-jersey structures is investigated, both in relaxation (involving tumble-drying from the wet state) and in extensive laundering (Cubex washing followed by tumble-drying). Tumble-drying for 1 hr from the wet-fabric condition only approximates to the completely relaxed state. Some felting of untreated fabrics occurs, but the effect of tumble-drying on felting is very small. Adequately shrink-resist-treated fabrics cannot be considered completely relaxed even after two consecutive tumble-drying cycles of 1-hr duration. However, in general, this technique allows sufficient fabric relaxation for subsequent dimensional changes over extensive laundering cycles of treated fabrics to be compatible with domestic machine-washable tolerances. The felting rates of knitted wool fabrics in laundering from the "fully relaxed' condition of untreated fabrics are dependent on the cover factor and independent of fabric structure. Under no circumstances, however, can untreated double-jersey fabric be practically manufactured to such tight constructions that felting can be eliminated entirely. The linear dimensions of shrink-resist-treated fabrics in the fully laundered state are primarily dependent on the length of yarn in the structural knitted cell. In a semi-relaxed state, linear dimensions depend to a large extent on cover factor and the degree of distortion of the fabric [ABSTRACT FROM AUTHOR]

A geometrical model of the smallest repeating unit or structural knitted cell (SKC) of the fully relaxed 1 x 1 rib structure is proposed. This model, based on an elastica configuration, suggests that the dimensions of the SKC are independent of the yam flexural rigidity and yarn-deformative forces but are dependent on the ratio of structural-cell stitch length (lu) to yam diameter. Over the practical knitting range, however, this dependence is small. A series of four non-dimensional parameters, or u-values, is introduced to specify the dimensional properties of this structure. The average numerical values of these parameters are calculated. A comprehensive experimental analysis of fully relaxed 1 x 1 rib fabrics shows that the experimental w-values are close to those established theoretically. Full relaxation is obtained by tumble-drying the structures from a wet state for 1 hr at 70°C, this being followed by conditioning in a standard atmosphere. No felting is observed during this relaxation procedure. Empirical u-values of the fully relaxed state are found to be independent of most yam and machine variables. A small dependence on the machine-tightness factor (K) is noted, however. [ABSTRACT FROM AUTHOR]