Polyamide offers exceptional value and performance as the textile fiber of choice. Polyamide has wide range of textile applications, such as apparel, sportswear, swimwear, casual wear, fashion wear, and hosiery. In the market, polyamide is preferred over polyester as:
· Fabrics can be dyed easily at atmospheric pressure in multiple designs and colours
· Higher strength
· Softer touch
· Lighter weight and more elegant texture
Elastane/Lycra/Spandex is a modern synthetic fibre known for its exceptional elasticity, hence its prevalence in athletic attire as well as in apparel designed for comfort. The material is extremely comfortable, lightweight and supple. It imparts stretchiness for underwear, lingerie, sportswear and outerwear garments and in other stylish attire, such as dancewear and club wear.
Relatively small percentages of elastane fibre is added to knit fabrics of polyamide type to provide stretch and recovery to the fabrics and the garments made from them. For fabrics that are knit on circular, or weft, knitting machines the elastane is normally added as a bare yarn. Subsequent to knitting, the fabric is preset, scoured, dyed, and then heat set.
There is a strong market trend towards the use of elastane fibres. Polyamide in combination with elastane needs a lower heat-setting temperature, which favours the retention of elastane properties. Combined with elastane, polyamide offers good stretch-fit properties.
Different types of dye such as acid dyes and metal complex acid dyes can be used for dyeing of polyamide fibres. Generally acid dyes which are anionic do not dye elastane fibres properly under mild dyeing conditions, and elastane fibres are slightly tinted. The wet fastness achieved on Polyamide/elastane blends is usually lower than on 100% polyamide because the dyes used for polyamide stain the elastane, and this stain subsequently washes out during test. To overcome this problem, Sarex has developed innovative product “Flexdye-ELA” which increases the affinity of acid dye molecules towards elastane fibres thereby providing higher colour build up especially black shades with good wet fastness on Polyamide/elastane blends.
§ Solves the problem of “Grin through” of undyed elastane fibre.
§ Develops solid shade in Polyamide/elastane fabrics. No adverse effect on light and wet fastness.
§ Ensures stable and reproducible shades.
MATERIALS AND METHODS
Substrate: Polyamide/Lycra blended Ready for Dye garment (innerwear)
Step-1: Prior to dyeing
Treat Polyamide/Lycra blended Ready for Dye garment (innerwear) with 2% Flexdye-ELA + 1% Acetic Acid for pH 4.5 at 50°C for 20 min prior to dyeing.
Dyeing is performed in the same bath of Step-1 by adding 4% Levaset Black B (Black acid dye) + 1% Supergen-MX (Leveling agent) at 98°C for 30 min. Drain the bath followed by cold and warm rinse.
RESULTS AND DISCUSSION
Fabric — Dyed without Flexdye-ELA
% Colourant strength — 100
h — 262.776
L — 20.385
Fabric — Dyed with 2% Flexdye-ELA
% Colourant strength — 121
dE — 2.184
h — 262.776
L — 18.210
Flexdye-ELA treated fabric dyed with Black dye shows even dyeing with an improvement in colourant strength and solid black shade while fabric dyed without Flexdye-ELA shows grey shade.