- 1 Properties Of Spandex Fibres
- 2 Processing Of Spandex Fibres
- 3 Different Properties Of Spandex Fibres
- 4 Applications Of Spandex Fibres
- 5 Comparison Of Spandex Fibre With Rubber
Spandex fibres are synthetic fiber known for its exceptional elasticity.
Properties Of Spandex Fibres
- It is a polyester- polyurethane copolymer.
- Invented by – Joseph Shivers at Duponts Benger Laboratory in Waynesboro, Virginia in 1958.
- Spandex is an anagram of the word “expands”.
- In textiles, the synthetic fiber known generically as spandex is composed of at least 85 percent polyurethane by weight. synthetic fiber
- Such fibers are generally used for their highly elastic properties. Trademarked fibers in this group are Lycra.
Processing Of Spandex Fibres
- Ethylene glycol + propylene glycol+ adipic acid ->to form a macro polyester.
- Macro polyester+ diphenyl methane di-isocyanate ->polyurethane.
- The first step is to produce the prepolymer.
- A typical ratio of glycol to di-isocyanate is 1:2.
- Prepolymer is further reacted with an equal amount of diamine – >chain extension reaction.
- Spinning solution is pumped into the spinning cell ->converted into fibres.
- In the spinning cell, the polymer solution is forced through a spinneret.
- Strands of a liquid polymer obtained.
- Liquid polymer converted to solid strands.
- Solid strands of desired thickness obtained.
- Finishing agent –Magnesium stearate or another polymer.
Process In Detail
- The first step is to produce the prepolymer. This is done by mixing micro polyester with diphenylmethane diisocyanate monomer. The compounds are mixed in a reaction vessel to produce the prepolymer. A typical ratio of glycol to diisocyanate is 1:2.
- The prepolymer is further reacted with an equal amount of di amine. This reaction is known as chain extension reaction. The resulting solution is diluted with a solvent to produce the spinning solution. Solvent helps make the solution thinner and more easily handled, and then it can be pumped into the fibre production cell.
- The Spinning solution is pumped into a cylindrical spinning cell where it is cured and converted into fibres. In this cell, the polymer solution is forced through a metal plate called a spinnerette. This causes the solution to be aligned in strands of liquid polymer. As the strands pass through the cell, they are heated in the presence of nitrogen and solvent gas. This process causes the liquid polymer to react chemically and form solid strands.
- As the fiber exit the cell, an amount of solid strands are bundled together to produce the desired thickness. Each fiber of spandex is made of many smaller individual fibers that adhere to another due to the natural stickiness of their surface.
- The resulting fibers are then treated with the finishing agent which can be magnesium stearate or another polymer. The treatment prevents the fibers sticking together and aids in textile manufacture. The fibers are then transferred through a series of rollers into a spool.
Different Properties Of Spandex Fibres
Microscopic Appearance Of Spandex Fibre
- Longitudinal view: Shows fibers of even diameter.
- Cross section: Shows difference in the shape of filaments.
- Smooth, dog bone shaped structure.
- Serrated structure: Prevents slipping in yarn and good flexibility.
Physical Properties Of Spandex Fibres
- Strength : Tenacity 0.5-1.03 gpd.
- Elongation : 500- 700% .
- Elastic recovery – excellent.
- At 200 % elongation ->98% elastic recovery.
- At 500% elongation -> 90% elastic recovery.
- Specific gravity: 1.2 to 1.25.
- Moisture regains: Is low 0.3 to 1.2%.
- Multifilament fibers absorb slightly more than monofilament fibres.
- Normally white in color: Spandex fiber.
- Dyeing is easy and uniform.
Thermal Properties Of Spandex Fibres
- Spandex fibers will burn and form a gummy residue.
- Can be ironed safely at the temperature below 150-degree celsius.
- Most spandex fibers are not damaged by temperature used in dry cleaning, laundering, low ironing temperature.
Chemical Properties Of Spandex
- Good resistance to most chemicals.
- Concentrated alkalis at elevated temperature cause loss of strength and eventually degradation.
Applications Of Spandex Fibres
Spandex is usually mixed with cotton or polyester. 80% of clothing sold in the US contained spandex in 2010.
Uses Of Spandex Fibre
Types of garments which incorporate spandex include:
- Activewear – athletic, aerobic and exercise apparel.
- Cycling jerseys.
- Dance belts.
- Net balls.
- Skinny jeans.
- Volleyball shorts.
- Mini skirts.
Comparison Of Spandex Fibre With Rubber
|Good resistance to degradation by ultraviolet light.||Poor resistance to degradation by ultraviolet light.|
|Good resistance to weather, smog, oils, perspiration, detergents.||Poor resistance to weather, smog, oils, perspiration, detergents.|
|Low density and high modulus of elasticity.||High density and low modulus of elasticity.|
|Superior flex life dyeability.||Low flex life dyeability.|
|Better resistance to abrasion, damage by dry cleaning solvents, dry cleaning solvents, bleaching compounds and to damage in machine laundering and drying.||Better resistance to abrasion, damage by dry cleaning solvents, dry cleaning solvents, bleaching compounds and to damage in machine laundering and drying|