Polymers Fiber :- The long thin polymeric filaments of natural or synthetic material which can be

woven or spun into fabric is known as fiber.

Polymer : A macromolecule formed by joining large number of repeating units is known as polymer. The repeating unit is known as monomer. (The word ‘polymer’ is coined from two Greek words: poly means many and meros means unit or part. ) Monomer : - The repeating structural units are derived from some simple and reactive molecules known as monomers and are linked to each other by covalent bonds. Polymerization : - This process of formation of polymers from respective monomers is called polymerization.

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Classification Of polymers based on source :- Based on sources polymers are classified as [ 1 ] Natural [ 2 ] Artificial 1 ] Natural Fibres :- Natural fibers are obtained naturally from plants or animal sources. Natural fibres are divided into two types [ A ] Vegetable fibres [ B ] Animal Fibres [ A ] Vegetable polymers:- Vegetable polymers are obtained from naturally occuring vegetable sources. These are carbohydrate ( polysaccharide ) fibres. Examples :- cotton, linen, jute, hemp, sisal, flex etc. [ B ] Animal polymers:- Animal polymers are obtained from animal sources. These are mainly protein fibres. Eg :- wool, silk etc. 2 ] Artificial Fibres :- Artificial polymers are man made fibres obtained by synthetic or semi – synthetic processes. These are divided in to two types [ A ] Regenerated Fibres [ B ] Artificial Fibres [ A ] Regenerated polymers:- These polymers are obtained from cellulose by chemical treatment. These are nothing but pretreated cellulose. After chemical treatment cellulose material regenerates with silky appearance, superior quality, luster and greater strength. Examples :- acetate rayon, cupprammonium silk, viscose rayon.

[ B ] Artificial polymers:- These are man – made polymers obtained by chemical process known as polymerization. The process by which monomers are converted into polymers is known as polymerization. It involves joining of large number of fundamental units ( monomers ), with the help of covalent bond, to give fibrous chain. All polymers have very high molecular weight. Examples :- Nylon – 66, Nylon – 6, Terylene, polyvinyl chloride ( PVC ), Teflon, Bakelite etc. ---------------------------------------------------------------------------------------------------------------------

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Classification Of polymers based on structure :-

11.. Linear polymers : The polymers made up of long continuous chain without any branches are called linear polymers. They have high melting points, high densities and high tensile strength. Example : Polyethene, PVC. These are represented as:

22.. Branched chain polymers : The polymers made up of main chain (linear chain)

with smaller chains as branches of main chain are called branched chain polymers. They have lower melting points, densities and tensile strength as compared to linear polymers. Example : Polypropylene. These are represented as:

33.. Cross – linked polymers : These

polymers consists of inking of chain polymers by strong covalent bonds leads to a three dimensional network structure are called cross – linked polymers. These polymers are hard rigid and brittle. Examples : Bakelite, melamine formaldehyde. These are usually formed from bi-functional and tri – functional monomers and contain strong covalent bonds between various linear polymer chains. These are represented as:

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Classification of polymers based on polymerization process. 11.. Addition polymers : The addition of a large number of monomers like alkenes or

alkynes and the polymers are formed by chain growth polymerization, e.g., orlon, teflon.

22.. Condensation polymers : The two monomers combine to form a polymer by

elimination of a small molecule like water or alcohol, e.g., nylons, polyesters. ---------------------------------------------------------------------------------------------------------------------

------------------------------------------------------------ Classification of polymers based on molecular forces : - Molecular forces bind the polymer chains either by hydrogen bonds or Vander Waal's forces. These forces are called intermolecular forces. On the basis of magnitude of intermolecular forces, polymers are further classified as elastomers, fibres, thermoplastic polymers, thermosetting polymers.

11.. Elastomers : These are rubber – like solids with elastic properties. In these elastomeric polymers, the polymer chains are held together by the weakest intermolecular forces. These weak binding forces permit the polymer to be stretched. When polymer is stressed, the polymer chain stretches and when the strain is relieved the chain returns to its original position. Elastomers are soft and stretchy and used in making rubber bands, e.g., neoprene, vulcanized rubber.

22.. Fibers : Fibers are the thread forming solids which possess high tensile strength

and high modulus. These characteristics can be attributed to the strong intermolecular forces like hydrogen bonding. These strong forces also lead to close packing of chains and thus impart crystalline nature. They are used in textile industries, strong ropes, tyres, etc. e.g., nylon – 6, terylene.

33.. Thermoplastic polymers : These are the linear or slightly branched long chain molecules capable of repeatedly softening on heating and hardening on cooling. These polymers possess intermolecular forces of attraction intermediate between elastomers and fibers. Some common thermoplastics are polythene, polystyrene, polyvinyl, etc.

44.. Thermosetting polymers : These polymers are cross linked or branched molecules which do not become soft on heating under pressure, hence cannot be remolded and recycled. These cannot be reused, e.g., bakelite.

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