Fibres

Fibers are pliable hair like substance that are very small in diameter in relation to their length. They are fundamental units in the making of textile yarns and fabrics. "Fiber" of "Textile fiber" means a unit of matter, which is capable of being spun into a yarn or made into a fabric of any nature or character.

According to Textile Institute "Fibers are defined as the units of matter characterized by fineness, flexibility and high ratio of length to thickness."

Classification of textile fibers
(a) According to their generation process-
         1) Natural fibers
                  i) Vegetable fibers
                       ==> Bast fibers ( Jute, Hemp, Kenaf, Flax)
                               All the fibers which are extracted from the stems of plants are classified as bast fibers.
                       ==> Leaf fibers ( Sisal)
                       ==> Seed fibers ( Cotton, coir)
                  ii) Animal fibers (Wool, silk)

                  iii) Mineral fibers (Asbestos)
          2) Man made fibers
                  i) Natural polymer based
                      ==> Cellulose
                      ==> Cellulose (Esters)
                      ==> Protein
                      ==> Miscellaneous
                  ii) Synthetic fibers
                      ==> Polyamides (Nylon)
                      ==> Polyester
                      ==> Polyvinyl-derivatives
                      ==> Polyolefins
                      ==> Polyurethanes
                      ==> Miscellaneous

b) According to their forms--
Depending on their form fibers are subdivided into following groups
            1) Fibril : A fibril is a very small cell or fiber, a long cell or a component of a cell wall.
            2) Staple fibers : They are also called staple short lengths of fibers which have been chopped from continuous filament in lengths of approximately 15-500 mm.
            3) Continuous filament : A manufacturer fiber of indefinite length extracted from the spinneret during the fiber production process
            4) Flocks fibers: Flock fibers are very short in length (>15mm) and therefore are not spinnable.

Requirements of fiber- forming polymer
Fiber forming polymers of apparel should be0
1) Hydrophilic
2) Chemically resistant
3) Linear
4) Long
5) Orientation
6) Able to form high melting point polymer systems
An explanation of these requirements is now given,

Hydrophilic properties

Fiber polymers should be hydrophilic. This means that the polymers should be polar, enabling them to attract water molecules. A fiber is comfortable to wear if its polymer system consists of hydrophilic polymers.

There are, fibers whose polymers are not hydrophilic and yet these fibers are used for the manufacture of apparel. In order to make the textile materials of these fibers more absorbent and, hence, more or less comfortable, hydrophilic polymer fibers need to be blended with the hydrophobic polymer fibers. Nylon and polyester, for example, are hydrophobic polymer fibers and are often blended with cotton, viscose or wool.

Chemical resistance

Fiber polymers should be chemically resistant for a reasonable length of time against the common degrading agents such as sunlight and weather, common types of soiling, body exudation, laundry liquors and dry cleaning solvents. Chemically resistant polymers should also not be toxic or hazardous wear against human skin; this is a most important requirement which is usually taken for granted.

Linearity

Fiber polymers should be linear, only linear polymers allow adequate polymer alignment to bring into effect sufficient inter-polymer forces of attraction to give a cohesive polymer system and, hence, useful textile fiber.

The atactic polymer: This is a stereo- irregular polymer. It has its side groups arranged at random, above and below the plain of the polymer backbone.
The syndyotactic polymer: This is a stereo-regular polymer. It has its side groups arranged in a regular alternating fashion above and below the plane of the polymer backbone.
The isotactic polymer: This is also a stereo- regular polymer. It has, however, all its side groups arranged on the same side or plane of the polymer backbone.

Length

Fiber polymers should be long. It has been found that the length of the polymers constituting the commonly used apparel fibers is an excess of one hundred nanometers.

Having the polymers oriented can give rise to sufficiently effective inter-polymer forces of attraction to form a cohesive polymer system and hence, a useful fiber.

Orientation 

Fiber polymers should be capable of being oriented. T his means that the polymers are or can be arranged or aligned into more or less parallel order in the direction of the longitudinal axis of the fiber or filament.

Perfect orientation of polymers is usually not oriented, nor is it desirable. The orientation of polymers in the polymer system of any fiber consists of two distinct, yet integrated forms. The two forms of polymer orientation are called the amorphous and the crystalline regions.

Formation of high-melting point polymer systems

A fiber consisting of a high melting point polymer system tends to have adequate heat resistance to enable it to withstand the various heat treatments of textile finishing, apparel manufacture and the heat subsequently applied to it during laundering and pressing or ironing during its useful life as a garment.

It appears that a fiber's melting point needs to be above 225 degree celcious if it is to be useful for textile manufacture and apparel use.