Prduction Technology of Man-Made fibers

Presentation
ON
The Production Technology Of Man-Made Fibers
Md. Yousuf Hossain, Green University Of Bangladesh, yousuf_te@yahoo.com

Md. Yousuf Hossain.
ID No. : 120103063
Department Of Textile Engineering
Green University Of Bangladesh

e.g. : 1. Rayon (Wood/ Bamboo)
2. Polyester (Petrochemicals)


Classification flowchart of man-made fibers
Man-Made Fibres
Inorganic
By transformation of natural polymer
From synthetic polymer
Acrylic = PAN
Aramid = AR
Chlorofiber =CLF
Elastane = EL
Elastolefin = EOL
Elastodiene = ED
Elastomultiester = EME
Polyamide = PA
Polyester = PES
Polyethylene =PE
Polyimide = PI
Polylactide = PLA
Polypropylene = PP
Vinylal = PVAL
Fluorofiber = PTFE
Modacrylic = MAC
Carbon = CF
Ceramic = CEF
Glass = GF
Metal = MTF
Aliginate =ALG
Acetate = CA
Cupro = CUP
Lyocell = CLY
Modal = CMD
Viscose = CV
Triacetate =CTA
Elastodiene =ED


How can we get man-made fibers?
Man-made fibers are produced from polymers.
These substances are solids at normal temperatures in the form of chips or small particles.
The polymers in solid form must be converted to fluid form as the polymer needs to be forced through the spinneret holes to form filaments.
Solidify fibers by cooling or evaporation or coagulation.


The polymer processing from the solid to the fluid state can take place with two methods-
I.By Melting. (This method is used for 70% of the fibers)
II.By Solution. (This method is used for 30% of the fibers)
i.Dry Spinning
ii.Wet Spinning
iii.Gel Spinning
The method is used for each fiber depends upon the easy conversion process of the polymer from solid to fluid state.


Melt Spinning:
The polymer is melted and pumped through a spinneret with numerous holes (one to thousands). The molten fibers are cooled, solidified, and collected on a take-up wheel.
Polymer converted to fluid just by heating.
Simplest process used for Polyester, Polyamide, Polyethylene, Polypropylene and Glass fibers.
High Speed ( up to 10000 m/min)


Required characteristics of fiber for Melt Spinning:
Fibers must melt without decomposition and be stable to at least 30 degree higher than its melting temperature.
Mobility in the molten polymer is necessary to be extruded.

Stages in Melt Spinning Process
At first, Heat the polymer.
Then, Extrusion through the spinneret (50mm in diameter) having fine holes of 0.5mm diameter.
Cool and solidify the filament.
Then, the solidified filaments are passed around a rotating roller and forwarded to a collecting roller.


Features Of Melt Spinning:
Melt-spun fibers can be forced through the spinneret in different cross-sectional shapes such as round, tribal etc. Which give different qualities to the fabric.
Do not have toxic hazard.
No solvent and purification problem.


Dry Spinning
If Polymer is getting chemically damaged by heating but it can be dissolved in a suitable volatile solvent which later on evaporates.
Speed = 1000 m/min.
Used for production of Acrylic, Modacrylic, Acetate, Triacetate, Spandex/Elastane.


Merits Of Dry Spinning:
Yarn does not required purification. Demerits Of Dry Spinning:
The obvious limitation for this method is that it depends on the existence of volatile solvent for the polymer.
Solvents are expensive, flammable and explosive in reaction with air.
3-6 kg solvent is needed for 1kg filament.


Wet Spinning
If the polymers cannot be melted by heating or dissolved in volatile solvent then wet spinning is used.
The spinneret is submerged in a chemical bath that leads the fiber to precipitate and solidify as it comes out of the spinneret hole.
Polymer is dissolved in a non-volatile solvent.
This is a slow process (speed=200 m/min)
Used for production of Viscose, Modal, Lyocell, Aramid fibers.

Figure 3 : Wet Spinning Process


Merits Of Wet Spinning:
Suitable for tow production.
Demerits Of Wet Spinning:
Cumbersome technology.
Purification of the filaments is needed.
Environment pollution hazards.


Gel Spinning:
In gel spinning the filaments first pass through air and then are cooled further in a liquid bath. Here polymer is partially liquid or in a gel state, which keeps the polymer chains somewhat bound together leading to greater tensile strength.
Used for production of high strength PE and aramid fibers.


Figure 4 : Gel spinning process.


Advantages of Gel spinning:
Medium speed (up to 1500 m/min).
Suitable for liquid crystalline polymers.
Disadvantages of Gel Spinning:
Environmental pollution hazards.
Purification of the filament is needed.
Cumbersome technology.


Comparative features of Melt, Dry and Wet Spinning
Features
Melt
Dry
Wet
Investment Cost
Low
High
Low
Toxic Hazard
Non-toxic
Toxic &
Risk of explosion
Toxic
Heat of Spinning
High
High
Low
Spinneret Hole
Two to thousand
300 - 900
20,000 - 75,000
Spinning Speed
1500 - 6000 m/min
1000 - 1500 m/min
200 - 300 m/min


Manmade fibers can be modified at any stage-
During production- e.g. Additives (Delustrant, heat & light stabilizers)
Immediately after production. e.g. Spin Finish (Lubricants, plasticizers)


Any Question?
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Prduction Technology of Man-Made fibers

Prduction Technology of Man-Made fibers

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