Today, the knitting industry heavily uses spandex combined with cotton, especially for sportswear, foundation garments, intimate apparels, etc., due to outstanding features of spandex such as higher elastic recovery, good shape retention properties, soft and smooth handle, abrasion resistance, resistance to pilling, resistance to most chemicals, resistance to normal apparel exposure to sunlight and lower moisture regain (< 1 %) [1].Behavior of a knitted fabric under relaxation from yarn internal stresses imposed during knitting depends on the knit structure, fiber type, stitch length, fabric tightness factor, knitting tension, relaxation type, drying method, etc. However, under full relaxation condition, effects of yarn and fabric parameters on a knitted fabric become a minimum energy condition and the stitches give a predictable geometrical configuration [1-7]. 1 Thus, resiliency force and yarn frictional force acting on interlacing points are major forces which affect the relaxation behavior of knitted fabrics [1]. Regarding this, spandex with higher elastic recovAbstract In this study, dimensional stability of core spun cotton/spandex single jersey structures with high, medium and low tightness factors were experimented under dry, wet and full relaxation conditions. Results were compared with those for similar fabrics knitted from 100 % cotton. Course and wale spacing decreased and course, wale and stitch density increased with progression of relaxation and higher values reported with cotton/spandex structures. Course, wale and stitch density were linearly and positively correlated with loop length -1 or loop length -2 . Their correlation equations showed minimal intercepts under full relaxation and cotton/spandex exhibited lower intercepts. Dimensional constants (K-values) were predicted under 95 % significance level. Higher dimensional constants were reported with cotton/spandex single jersey structures than 100 % cotton and under full relaxation, cotton/spandex indicated better stable structures under full relaxation. From these experiments, it was confirmed that yarns with elastomeric components increase tightness factors, which have a significant effect on dimensional behaviors, giving better dimensional stability to single jersey fabrics. Yarn linear density was insignificantly changed during treatments.

Purpose -This paper aims to study the dimensional characteristics such as fabric density variations, dimensional constant parameters, linear and area dimensional changes and spirality angle variations of 1 £ 1 rib knitted structures made from cotton-spandex core spun yarns, under laundering regimes till 10th washing cycle. Design/methodology/approach -Samples of the above fabrics underwent dry, wet and full relaxation treatments and were subjected to standard atmospheric conditions prior to take the measurements. Washing was done in a front loading machine under normal agitation with machine 56 RPM. Each washing regime includes wash, rinse, spin, tumble dry steps. Washing temperature was set at 408C and water intake for washing was 30 l and rinsed with cold water. 0.1 g/l standard wetting agent was used. The mass of the load was maintained constant to 3 kg to keep the material ratio as 1:10. Washing regimes were continued till 10th cycle. Findings -Cotton-spandex rib structures came to a more stable state (minimum energy state) after 10th laundering cycle under the experimental conditions. Cotton did not come to such a state, even after 10th cycle proceeded. ANOVA analysis done under 95 percent confidential level has shown that fabric tightness and relaxation procedures give significant effect on dimensional characteristics of cotton-spandex and cotton rib structures. However, area shrinkage variations of cotton rib fabrics have shown an exception to this. Research limitations/implications -According to the dimensional constant values, evenafter 10th washing cycle, cotton rib structures did not come to a stable position. This should be further investigated to achieve a better stable rib knitted structure. Practical implications -The number of washing cycles can be increased or tumble dry duration can be increased to 120 min. to get a more stable state of cotton rib structures. Originality/value -The results are important for the knitting industry to predict the dimensional behavior of designed knitted fabric under relaxation. These data can be used to set the circular machine parameters to achieve a more stable fabric after laundering.

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