THE SPANDEX STORY
In the USA, Spandex is the generic name for a fibre that is often better known by consumers under a variety of brand names.
Research in polyurethane began in Europe in 1937, led by Otto Bayer in the labs of the Bayer company. In 1939 Paul Schlack created a high molecular weight polymer that enable the production of fibres with outstanding elongation and stretch properties. In 1951 W.Brenschede produced Vulkollan fibre by using a process called “Wet Spinning”. In 1958 the DuPont labs in Wilmington developed the “Dry Spinning” process.
The first elastomer fibre was patented in 1959 under the name Lycra, and commercialisation began in 1962. At first Lycra fibre was used in medical stockings, because the manufacturing process was initially limited to high count fabrics. But it was clear from the very start that elastomers offered incredible potential. In 1964 a famous Italian stylist presented a Spandex swimwear fabric.
In the 1970s research in this field concentrated on obtaining higher thread counts, but it wasn't until the early 1980s that elastomers made their appearance in the legwear market, giving tights and stockings unprecedented comfort and fit.
Spandex can be used bare, with no processing before inclusion in the hosiery and Spandex fabrics. A simple Spandex thread is added (woven into) to the structure created by the main flat or textured thread. Another production technique is knitting bare or covered Spandex yarn within the garment. This is the vanisé or plated technique, where one yarn appears on the front and the other on the back of the back of the fabric.
It is generally used in alternate rows of knit yarn. Finally, the covered yarn can be used in every row - in every thread of the knit - for three dimensional stretch.
Covered Spandex is also used. The covering involves wrapping the Spandex in the main yarn in the nylon hosiery, so that the Spandex becomes the yarn core.
Four processes can be used for covering:
Single covered: the nylon or other fibre is wrapped in a spiral around the Spandex once only with an average of 1,200-2,200 turns/metre. The more turns, the higher the quality.
Double covered: the Spandex yarn is wrapped in two layers of nylon or other fabric, one clockwise and the other anticlockwise. The average number of turns is 2,400 turns/metre, but this number can reach 3,000 per metre in ultra-high quality yarns. It is used in yarn intended for the production of high quality sheer tights.
Air covered: Spandex in tension and texturised nylon are passed together through a jet of air, interlacing the nylon at intervals to Spandex core.
Core-spun: during the yarning process the Spandex is covered with a coating of discontiunuous fibres.
CHARACTERISTICS OF SPANDEX
The bare Spandex thread is used in standard products. Bare Spandex knitted with a vanisé method is used in standard products and sheer and summer tights. Stretch performance is reduced but enables the production of super-sheer tights. Covered Spandex is intended for the high and medium market segments - in fact, the more the Spandex is protected, the more long-lasting and expensive the tights are. The garment is also very soft to the touch.
There are no 100% Spandex tights, as low percentages of another fibre are always added – nylon, cotton, wool and silk, blends – forming the basis of the tights. Its essential characteristic is high elasticity and elastic recovery, which remained unchanged over time.
In other words, Spandex thread can stretch to over eight times its original length and return instantaneously to its initial configuration as soon as the tension is released. Fit and comfort are the primary and most generally-appreciated results of this property. Tights with Spandex cling to the legs while allowing total freedom of movement. Spandex gives tights a longer life, because it creates an enhanced fit - the fabric is never too tight or too loose, the two major causes of splits. No special washing care is needed.
Manufacturers have added other qualities to these basic features, like resistance to chlorine, fumes, pollution, chemical and oxidising agents, mould and bacteria.