Production and Classification of Man Made Fiber

Man made fiber:
Man made fibers are those that are made by drawing and orientation of suitable semi - synthetic and synthetic polymers that are commonly called fiber - forming polymers. Semi- synthetic polymers are infact, chemically modified natural polymers where only the side groups are partly, significantly or fully modified by a chemical process. Synthetic polymers are completely man - made and nature is unable to synthesize them. The synthetic polymers are prepared from the respective monomers by a process called polymerization. Polymerization can be accomplished by intermolecular reaction. We have discussed on polymerization in this post.
Man made fiber
Fig: Man made fiber
The term man-made or manufactured fiber means any fiber derived by a process of human generated manufacturing system. Man made fiber is mainly four types, is given below:

   A. Regenerated fiber: Viscose rayon, Alginate and rubber.
   B. Semi-synthetic fiber: Acetate, Tri-acetate.
   C. Synthetic fiber: Polyester, Nylon, Acrylic, Polypropylene, Polyvinyl chloride, polyvinyl alcohol etc.
   D. Inorganic fiber: Glass, Carbon and Metal fiber.

Classification of man made fiber:
Man-made fibers are classified into three classes. They are:
  1. Fibres from Natural Polymers
  2. Fibres from Synthetic Polymers
  3. Fibres from Inorganic Materials
We will get clear concept about classification of man made fiber from the following image file:
Man-made fiber classification
Fig: Man-made fiber classification
Principle of man-made fiber production:
The principles of man-made fiber production are grounded on three basic steps:
  1. Conversion of the fiber forming substance into a fluid by solution or melting.
  2. Extrusion of the fluid through spinnerets.
  3. Solidification of the extruded filaments.
Manufacturing of fiber forming polymer:
Synthetic fiber-forming polymers are made in two steps:

1. Synthetic of reactive precursors: These are small molecules, which are called monomers. Petroleum is the main raw material for their production.

2. Coupling: It is a process to form macromolecules from of thousands of monomers. The macromolecules are called linear polymers, because they are built from many monomers into long chains. This process is named as polymerization.

Polymers are very large molecules made up of smaller units called monomers or repeating units, covalently bonded together.

Two different types of polymerization reaction are utilized to synthesize fiber-forming polymers. Namely:

1. Addition: Addition polymers are made by direct coupling of two, usually identical. Reactive monomers to form long chains, without by-product. Typical addition polymers are polyacrylics, polyvinyl chloride and polypropylene.

2. Condensation: Condensation polymers are made by coupling two. Usually different, reactive monomers, with the elimination of a small by-product molecule. Typical textile condensation polymers are polyesters and polyamides.

For knowing polymer we should know the following definitions:

Homopolymer: Homopolymer are made from single species of monomer.

Copolymer: Copolymer are made from two or more different species. In copolymers, the two monomers may be pre-formed into blocks which, when polymerized, form a block copolymer.

Block copolymer: The starting reactive monomers are pre-formed into blocks, which are then polymerized, usually by condensation. Elastomeric fibers are made from block copolymers.

Man-made fiber manufacturing process:
There are three major types of process for manufacturing manmde fibers.
  1. Melt spinning
  2. Wet spinning
  3. Dry spinning
1. Melt spinning:
The molten polymer is extruded through spinneret then passed into cold air stream which cools the soft melted fiber and solidifies the filaments. Later solidified filament is drawn at 3 to 8 times for specific fineness.

Examples: Nylon, Polyester

2. Wet spinning:
The polymer solution is extruded into a bath containing chemicals which neutralize the solvent and coagulate the filaments. According to fineness of filaments, solid filament is drawn certain times.

Examples: Viscose, Acrylics.

3. Dry spinning:
The polymer solution is extruded through spinneret into a stream of warm air which evaporates the volatile solvent and solidifies the filaments. According to fineness of filament, solid filament is drawn a certain times.

Examples: Acrylics, Acetate.

They have several basic elements in common: a reservoir and a metering pump for the fiber-forming material, a spinning jet, a fluid by which the filaments are formed and a take-up mechanism which draws the filaments and winds them onto a package.

After the filaments have been extruded and solidified, they are drawn out between rollers having different speeds. Drawing can also be a separate process. Spinneret size, plus spinning and drawing conditions, determine the final filament diameter.

The shape of spinneret hole and fiber cross-section:
The hole of the spinneret may be circular, oval, tri-angle or star etc. this enables the production of filaments having different cross-sections, which influences on the properties of fiber e.g strength, lusture and handle.
Shape of spinneret hole
Fig: Shape of spinneret hole
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