Traditionally the denim fabric is made of 100 per cent cotton indigo dyed warp and white weft yarn of coarser counts. The fabrics are woven on projectile, rapier, air-jet and shuttle looms. Initially the denim fabric was developed as work wear. Now the scenario is different. Denim fabrics has gained immense popularity and accepted by all irrespective of gender, age-groups and profession. So, there is tremendous challenge on the part of denim product manufactures to innovate and develop products to suit requirements of different consumers. In this article, it is attempted to put latest developments in the field of denim fabrics.
The major focus areas of innovation and development are comfort, performance and environment friendliness of different processes. Comfort and fit are very important aspects of denim garments. So, a lot of research has being done to make stretch denims. elastane fibers are incorporated into the fabric. Lycra and Spandex are used in weft yarn. Ring and open-end core spun yarns are also used in denim to provide stretch property. Elastic ply yarns produced on TFO are also used to make stretch denim fabrics. Apart from the multi-component, Bi component synthetic filament yarns are also used to provide stretch.
To improve performance, synthetic fibers blended with natural fibers are used. One of such blends is blend of Nylon 6.6 and cotton. This fabric shows the traditional look and feel but performance is better than the 100 per cent cotton denim in terms of better abrasion resistance. So, the durability of the fabric is more than the 100 per cent cotton denim. Other synthetic fibers such as polyester and polypropylene fibers are also used. For making softer denim fabrics especially for women wear, blend of Cupro, Modal, Promodal, Tancel, and Rayon are being used. Bamboo fibers, hemp fibers and their blends are being used to make denim fabrics.
To impart fancy effect, different kinds of fancy yarns are being used. The examples of such yarn are slub yarn and multi-count yarn. The slub can vary in terms of thickness, length and twist. Such yarns can be manufactured at ring spinning and OE spinning machines by attaching special attachment. One of such attachments is Amsler control. Such fabrics give very unique effect after washing treatment.
Two methods of warping are practiced. These are ball warping and direct warping. Dyeing of warp yarns is done either by rope dyeing method or Slaser dyeing method. Rope dyeing is considered better in many aspects such as higher production, long runs, better dry and wet fastness and lot-to- lot shade consistency. Indigo dyes are generally used to dye warp yarns. In some cases sulphur black and blue dye can also be applied before indigo dyeing to achieve darker shades. Sometimes, sulphur dyes are also applied after the yarn is indigo dyed.
A lot of research is taking place to develop dyeing process which produces low impact on environment. Clariant has developed a range of low sulphide dyestuff and process to obtain various indigo shades at low dyeing cycle to reduce the consumption of water. Dyester has patented Indigo Vat 40 per cent solution. It offers various shades of blue and claims 60-70 per cent reduction in consumption of Sodium hydrosulphite
Denim fabrics are mostly woven on high speed air-jet looms. Various loom manufacturers are offering a number of modifications to weave fault free high quality fabric. The modifications are done in the frame structure of loom to minimize vibrations, pre-winder, auxiliary nozzles, stretch nozzles, relay nozzles and weft brake system. Traditionally denim is 3/1 right hand twill fabric. Nowadays 2/1 twill, broken twill, zig-zag twill, reverse twill, Herringbone twill weaves are used in denim fabrics.