Weft knitted structures are aff ected by various forms of dimensional distortion. Inclination and distortion of loops within knitted structures are commonly known as skewness and spirality, respectfuly. Causes of skewness and spirality have been thoroughly investigated, analyzed and classifi ed. They can basically be divided into two groups: material causes and process causes. One of the material causes is yarn related and is caused by residual torque in the yarn shown by its twist-liveliness. One of the more important process causes is machine related and is connected to knitting with multiple feeders on the circular knitting machine. Skewness and spirality have been subjects of research for almost a century. Models have been developed for understanding and predicting the loop distortion phenomena. Procedures for reduction or even elimination of the skewness/spirality have continuously been developed and improved. Some of them include changes in raw material, the others in mechanical processes and/or equipment while the other again concentrate on after-treatments. Many standards and other testing methods for measuring the skewness and spirality have been used in research and industrial practice. The uses of many terms describing this phenomenon have shown the continuous importance of the skewness/spirality problem on the one hand and the inconsistency of the terminology on the other.

For decades, scientists have been trying to define relationships among yarn parameters, knitted fabric parameters, and knitting parameters with loop models. Recently, the geometrical loop models have returned to focus as they assist finding the effective parameters which cause dimensional changes during relaxation. Furthermore, they help designing knitted structures for technical applications and obtaining computer simulations of knitted structures. In the past, geometrical loop models considered more or less porous structures and the yarns used were mostly conventional, without elastane. The behavior and characteristics of compact knitted fabrics made from elasticized yarns have been investigated only recently. In general, mostly the structures with plated elastane threads have been analyzed. The aim of the research was to study the geometrical parameters (yarn thickness, loop width, loop height, fabric thickness, loop length) of plain single weft knitted structures made from various elasticized yarns, in comparison to equivalent structures made from conventional yarns. In the study, the most frequently applied loop models for the loop length calculations were evaluated with the emphasis on their adequacy for elasticized knitted structures. A new loop model for an elasticized weft knitted structure based on the multiple linear regressions was defined.

Contemporary multifunctional textiles are based on hi-tech functionalization. Knitted structures can be relatively rapidly designed and produced in a variety of textures due to their composition of many interlacing loop elements and their combinations. Foldable weft-knitted structures exist in a wide range of forms from simple rolls, ribs, and pleats to more complex three-dimensional structures. They exhibit new kind of geometry and deformation mechanisms. Some of them exhibit auxetic potential. Foldable knitted structures are multifunctional and widely usable. They can be produced in a variety of structures, qualities, and dimensions: in panels, fully-fashioned, or seamless. Their possible application lies in different fields, such as fashionable and functional clothing, sportswear, medical care, packaging, interior design, sound and shock absorption, etc.

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