Spandex is a term used as an anagram for the word expands. The synthetic fiber is also known as lycra or elastane and is popular for its exceptional elasticity. The classic AC air covering machine can produce the spandex fibers through any of the following means:
- Melt extrusion
- Reaction spinning
- Solution dry spinning
- Solution wet spinning
All the above methods feature an initial step that involves the reaction of monomers to produce a pre-polymer. In order to give fibers various reactions are performed on the pre-polymer in various ways.
Dry spinning is the most popular method among all the ones mentioned above. Of the entire world’s spandex fibers approximately 94.5 percent is produced by this method.
The process…
The process has 5 main steps:
- The first step produces the pre-polymer by mixing diphenylmethane diisocyanate monomer with micro polyester in a reaction vessel.
- Next, the prepolymer is reacted with a diamine of equal amount. The product is then mixed with a solvent to dilute it and give it a spinning solution. After dilution into a thinner solution, it’s then pumped into the fiber production cell.
- After that the spinning solution is then sent to the cylindrical spinning cell. After that the spinning solution is then forced on to spinnerette. The process of curing and turning them into fiber is done over here. Then in the presence of solvent gas and nitrogen, the strands are heated. In this process the conversion of liquid polymer to solid strands is carried out by performing chemical reactions.
- The strands are bundled to form fibers of the desired thickness as they exit the cell. A single fiber is made up of multiple smaller individual fibers.
- The resulting fibers are treated with a polymer such as magnesium stearate to prevent the fibers from sticking together.
The Properties of Spandex
Microscopic Appearance
- Has a smooth structure
- Has a serrated structure that holds it in place and prevents it from slipping. This also enhances the flexibility
- Longitudinally, it shows fibers of similar diameters
- Cross-sectional: it shows the different shapes of filaments
Physical properties
- Can elongate anywhere from 500 to 700%
- Has an excellent elastic recovery
- Tenacity (strength): 0.5 to 1.03
- Its moisture regains is 0.3 to 1.2%
- The specific gravity is 1.2 to 1.25
- Easy, quick, and uniform dye application
- Often white in color
- The multifilament fibers are more absorbent than the monofilament fibers.
Chemical Properties
- Resistant to almost all chemicals
- Can be degraded by concentrated alkalis at high temperatures. This results in loss of strength
Thermal Properties
- After being burnt, the fibers will form a gummy residue
- Spandex can be ironed safely at the temperatures of 150°C or below
- Most spandex fibers are not ruined during dry cleaning, laundering
Major uses for spandex fiber
Spandex is used in a wide range of garments due to its high elasticity and significant strength. Spandex can be often mixed with polyester or cotton. Most of these garments are skin-tight and often dry faster than ordinary fabrics. Some applications of spandex are:
- Swimsuits
- Activewear
- Tights and leggings
- Bras
- Belts and gloves
- Cycling shorts and jerseys
- Superhero outfits
- Wrestling Singlets
- Ski pants
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