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As any other matter, textile fibres are also having chemical structure. The chemical structure of fibres is different from one another. For example: Cotton fibre is made up of cellulose which consists of hydrogen, carbon & oxygen. The way in which the chemical elements are arranged is what makes cotton different from polyester which has the same chemical constituents. The chemical structure affects fibre properties such as strength, elongation, resiliency, density, moisture content, sunlight and ageing resistance, dye absorption and electrical behaviour.
The fibre morphology refers to the molecular arrangement of fibre. The molecules in fibres are in the form of chains. These are known as polymers. Polymerization is the process of joining together small molecules known as monomers. The longer the chains, the higher the degree of polymerization.
The arrangement of molecules in these fibres can be described in terms of molecular orientation and amorphous regions. When the molecules of fibres are parallel to each other and also parallel to the longitudinal axis of the fibres, the arrangement is said to be highly oriented structure. If the molecules are arranged in haphazard way or at random, it is termed as amorphous or low oriented structure. A crystalline structure occurs when the fibre molecules are parallel to each other but not necessarily parallel to the fibre axis.
In a single fibre, it is common to find both amorphous & crystalline regions and fibres vary in the proportion of oriented, crystalline and amorphous regions.
The molecular arrangement of natural fibres is difficult to change except in cotton where the molecules tend to decrystallise by mercerization finish.
The man-made & synthetic fibres when extruded through the spinnerette consist of only random arrangement but when they are stretched they become thin and tend to take oriented structure. It improves the strength, elongation, moisture absorption, abrasion resistance & dyeability of fibres.
The properties like elasticity, strength etc are also dependent on the strength of the bonds between molecules. These molecular chains are held together by cross links or inter chain attractions or bonds such as Hydrogen bonds & Vander walls forces. Hydrogen bonds are stronger than vanderwalls forces even though both are found in crystalline arrangements. Hydrogen bonding occurs when the positive hydrogen atoms show attraction towards negative oxygen or carbon present in another chain. Thus the molecular structure of fibres is an important factor that effects the properties of fibres.
The molecules are held together in a chain like formation within a macromolecule by strong electronic force known as valency bonds. For example cellulose which is the base of cotton is formed by the polymerization of small, simple molecules in to a larger complicated macromolecule.
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