How to study Polymers for JEE Main 2015 by ednexa.com

1. 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.

2. [ 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.
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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.

4. 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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