spandex (part 2)

8/11/2019 Spandex (Part 2)

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Manufacturing

End uses

Riaz-ul-haq

060820-054

Manufacturing steps

Polymer manufacturing (polyurethane).

Spinning.

Finishing & Drawing.

Winding.



Polyurethane manufacturing:

The manufacturing of a polyurethanerequires a pre-polymer.

Pre-polymer production:

In this process a pre-polymer is obtainedthrough high-molecular-weight diol.

In this mixing of highly purified ingredientsat high temperatures takes place.

In this process the softsegments(polyesters or polyethers) areproduced.

Pre-polymer production continue..

mixing of three moles of a polyglycol with

two moles of a diisocyanate so that a low-

molecular-weight polymer having hydroxyl

groups is obtained.

Then one mole of this product is reacted

with two moles of another diisocyanate the

hydroxyl end groups are replaced by

isocyanate end groups which is medium-

weight polymer (second pre-polymer) .

This viscous syrup is called a pre-polymer.



Segmented polyurethane production:

In this process the conversion of pre-

polymer to polyurethane (high-molecular-

weight) take place.

the reaction take place when pre-polymer

is combined with diamine or some other

bi-functional active hydrogen compound

such as a diol

Segmented polyurethane continue..

The polymer produced has the following

structure:

-ABABABA-A-A-A-

ABABABABA-A-A-A-ABABABA-

Where A is diisocyanate and B is diamine.



Spinning:

There are three major types of spinning:

Dry spinning

Wet spinning

Melt spinning

Dry spinning:

In dry spinning the

heated polymer

solution is forced to

pass through the

spinneret into a hot

gaseous region in a

spinning tube andthe solvent is

removed.



Wet spinning:

There are two methods to perform wet -

spinning.

In the first method, The polymer solution

is extruded into the coagulation bath by

means of orifices in the spinneret.

After coagulation the fiber is wound aboutdue to combining and fusion of the

filaments.



Wet spinning continues…

In second method

the pre-polymer is

used.

In this method the

pre-polymer solution

is extruded into a

liquid bath to form

diamine solution andthe chain

enlongation take

place.



Melt spinning:

This technique is not in practice commercially.

In this technique the spandex fiber is produced at hightemperature by simple extrusion of the polymer solutionand polymer is kept for a very short time at hightemperature for cross-linkage.

The excess cross-linking and the formation of gel takeplace if the polymer is Kept for more than a short whileat high temperature. That is why this process is not usedcommercially in the production of spandex fibers.

Finishing & Drawing: To remove the stains different fiber finishes are

used.

Commercially complex mixtures are used theyalso provide proper lubrication charge protectionand make the fiber non-interferer to subsequentdyes.

Most types of spandex fibers are drawn orstretched and heat-set when they are in the

enlongation state to yield a finer yarn size, high-modulus, low stretch and lower set.



Winding:

It is the final process in the manufacturing

of spandex fibers. It is winding onto tubes

,spools or cones. The process is carried

out on

Conventional textile epuipment.Extra care

is required during the process when it is in

the low or uniform tension.

End-Uses:

Generally there are six end-uses of spandex fiber:

Circular knits:

They include active wear, swim wear,casual wear e.t.c

Hosiery:

Socks, briefs e.t.c

Non-woven:

Personal care products like diapers.



End-uses continues…

Narrow fabrics:

Waistbands, straps, belts

e.t.c.

Warp knits:

Body shaping garments.

Stretch woven:

Stretch cloths like skintight jeans, stretch bandages and wraps.

“There are also several uses of

spandex fiber.Radici spandex

type S-17 is used to avoid ultra

violet rays,suntan oil and

perspiration.It is also chlorine

resistant.Elastoester is used for

outerwears and

furnishing.Heavier sizes,like 1120

den and above, are used in the

elastic webbings and straps

End uses continues……

spandex (part 2)

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