Hamza Sameen Assigment of textile

SPANDEX FIBER DEFINATION

Spandex is synthetic polymer.Chemicaly is made up of a long chain polyglycol combined with a short diisocyanates and contains at least 85% polyurethane. These fibers are superior to rubber because they are stronger, lighter and more versatile. Infect spandex fibers can be stretched to almost 500% of there length. Spandex melts at 250 C.

MANUFACTURING OF SPANDEX FIBER

Spandex, Lycra or elastane is a synthetic fiber known for its exceptional elasticity. It is stronger and more durable than natural rubber. It is a polyester-polyurethane copolymer that was invented in 1958 by chemist Joseph Shivers at DuPont's Benger Laboratory in Waynesboro, Virginia.

Spandex fibers are produced in four different ways. Melt extrusion Reaction spinning Dry spinning Wet spinning

All of these methods include the initial step of reacting monomers to produce a prepolymer. Once the prepolymer is formed, it is reacted further in various ways and drawn out to make the fibers. 

The solution dry spinning method is used to produce over 94.5% of the world's spandex fibers

Solution dry spinning

There are five step of solution dry spinning.

STEP 2.

 THE PREPOLYMER IS FURTHER REACTED WITH AN EQUAL AMOUNT

OF DIAMINE. THIS REACTION IS KNOWN AS CHAIN EXTENSION

REACTION. THE RESULTING SOLUTION IS DILUTED WITH A SOLVENT (

DMAC) TO PRODUCE THE SPINNING SOLUTION

Step 1.The first step is to produce the prepolymer. This is done by mixing a macroglycol with a diisocyanate monomer. The two compounds are mixed in a reaction vessel to produce a prepolymer. A typical ratio of glycol to diisocyanate is 1:2

Step 3.

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 spinneret. This causes the solution to be

aligned in strands of liquid polymer. 

Step 4.

 As the fibers exit the cell, an amount of solid strands are bundled

together to produce the desired thickness. Each fiber of spandex is

made up of many smaller individual fibres that adhere to one another

due to the natural stickiness of their surface.

Step 5.

The resulting fibers are then treated with a finishing agent which can

be magnesium stearate or another polymer. This treatment prevents

the fibers' sticking together and aids in textile manufacture. The

fibers are then transferred through a series of rollers onto a spool.

PICTURE OF SPANDEX FIBER

There are many picture of spandex fiber.Such as

Physical Properties of Spandex Fiber:

1. Cross section- Spandex filaments are extruded usually from circular orifices, but the evaporation of solvent or the effects of drying may produce non-circular cross-sectional shapes. This may take various forms. In the multi-filament yarns, individual filaments are often fused together in places. The number of filaments in a yarn may be as few as 12 or as many as 50;the linear density of filaments ranges from 0.1 to 3 tex (g/km).

2. Density: The density of spandex filaments ranges from 1.15 to 1.32 g/cc, the fibers lower density being based on polyesters.

3. Moisture regain: The moisture of fibers from which the surface finish has been removed lies between 0.8 & 1.2%

4. Length: It can be of any length. May be used as filament or staple fiber

5. Color: It has white or nearly white color.

6. Luster : It has usually dull luster.

7. Strength: Low strength compared to most other synthetic fiber.

8. Elasticity: Elastic properties are excellent. This is the outstanding characteristic of the fiber.

9. Heat: The heat resistance varies considerably amongst the different degrades over 300 F.

Chemical Properties of Spandex Fiber:1. Acid: Good resistance to most of acids

unless exposure is over 24 hours.

2. Alkalies: Good resistance to most of the alkalis, but some types of alkalis may damage the fiber.

3. Organic solvents: Offer resistance to dry cleaning solvents.

4. Bleaches: Can be degraded by sodium hypo chloride. chlorine bleach should not be used.

5. Dyeing: A full range of colures is available. Some types are more difficult to dye than others.

USES* Apparel and clothing articles where stretch is desired, generally for comfort and fit, such as:o Athletic, aerobic, and exercise apparelo Wetsuitso Swimsuits/bathing suitso Competitive swimwearo Netball bodysuitso Bra straps and side panelso Ski pantso Disco jeanso Slackso Hosieryo Leggingso Sockso Diaperso Skinny jeanso Beltso Underwear