Introduction with man made fibres and protein fibres

• Wool

Wool is a epidermal in origin. Wool fibers grows from the small follicle of the skin of sheep. The sheep are primarily raised where the climate permits them to winter in the open.

Wool may be sheared from the living animal or pulled from the hide after the animal has been slaughtered for its meat. Traditionally felts have been made from wool and from other animal hair fibers, all of which have an lubricated scale structure so that the frictional coefficient root to tip is much lower than in the tip to root direction the difference between the two being described as the directional frictional effect.

Chemical composition

Keratin-33%

Dust-26%

Suit-28%

Fat-12%
Mineral matter-1%

Classification by fleece

Lambs wool: The first fleece sheared from a lamb about six to eight. months old is known as lambs wool and some time referred to as fleece wool.
Hogget wool : comes from sheep twelve to fourteen months old that not been previously shorn.
Wether wool: Any fleece clipped after the first shearing is called wether wool.
Pulled wool: When sheeps are slaughtered for meat, their wool is pulled from the pelt by the use of chemical.

• Silk

The silk polymer is folded linear fibrin polymer. It has no crystalline linkage like wool polymer and has high degree of orientation. It contains anion acid.
Functional group -COHO, -CONH-

The techniques used to process these fibers in yarn are essentially the same as with natural fibers, modification have to be made as these fibers are of great length and have no texture such as the scales in cotton and wool that aid meshing.

Chemical composition
Fibrin-62.2-67%
Sericin-30%
Mineral matter-1%
Wax-0.5%

Silk scouring is know as degumming. The main impurities of silk is one kind of gum and this is soluble by hot soap solution. Alkali is made during soap washing. This alkali react with the carboxyl group of cericine and convert it into soluble form. This is the basic principle of silk scouring.

• Nylon

The term nylon was derived from 'no-run', the name originally considered by its inventors to emphasize the durability of ladies hosiery manufactured from it. The most important polyamide fiber is nylon 6.6, that is polyhexamethylene adipamide. Nylon 6 is the second most important polyamide fiber. It is extruded from polycaprolactam.  The notation 6 denotes that only one monomer containing six carbon atoms is required to polymerize this type of nylon.

Chemical effect: 

Effect of acids: Nylon is less resistant to acids than it is to alkalies. The  amide groups in the nylon polymers are readily hydrolyzed under acidic conditions.


Effect of alkalies: Prolonged and frequent exposure to alkalies will cause significant alkali hydrolysis of nylon polymers.This is noticed as a weakening of the nylon textile material. 

• Polyester

The word ester is the name given to salts formed from the reaction between an alcohol and an acid. Esters are organic salts and polyester means many organic salts. Polyester is a man made, synthetic polymer, polyester filament or staple fiber. The most common polyester apparel or staple fiber is usually composed of ployetylene terephthalate polymers.

Chemical properties:

Effect of acids: The ester groups of the polyester polymers resistant to acid hydrolysis, as are the other chemical groups of the fiber polymer. This resistance is further enhanced by the extreme crystallinity of the polyester polymer system which prevents the entry of any acid and water molecules into the filament of staple fiber. 

Effect of alkalis: Alkaline conditions as encountered during laundering may hydrolyse the polyester polymers at their ester groups. The extreme crystallinity of the polyester polymer restricts the hydrolysis to the surface of the polyester filament or staple fiber.

Effect of bleaches: Normally polyester textile materials do not need to be bleached. If  bleaching is required this is effected using sodium chlorite.    

• Acrylic

    The term acrylic is derived from the Latin word acryl, which means bitter, irritating or pungent and descriptive of the compound, acrylic acid. Acrylonitrile is chemically related to acrylic acid and the term acrylic is short  for polyacrylonitrile.    
The acrylic fibers are man made, synthetic polymer based, polyacrylonitrile filaments or staple fibres. They are divided into two types:
1) Polyacrylonitrile fibers are generally referred to as the acrylic fibers.
2) Modified polyacrylonitrile fibers generally referred to as the modacrylic fibers.

Chemical composition: 


Effect of acids: The acrylic fibers are resistant to acids because their polymers do not contain any chemical groups which will attract or react with acid radicals.

Effect of alkalis: The very crystalline nature of the acrylic polymer system prevents the ready entry of alkaline substances. However, surface alkaline hydrolysis or surface saponification will occur.


Effect of bleaches: Acrylic fibers are not usually bleached in practice. As a result, little is known about the effect of bleaches on acrylic polymers.