hi for education.

1. A polymer is a molecular compound distinguished by a high molar mass, ranging
into thousands and millions of grams, and made up of many repeating units.
Very Large molecules structures chain-like in nature.
Poly mer
many units
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2. •The process by which the monomer molecules are linked to form a big
polymer molecule is called ‘polymerization’.
•Polymerization is a process of bonding monomer, or “single units”
together through a variety of reaction mechanisms to form longer chains
named Polymer
Polymerization
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3. CLASSIFICATION OF POLYMER
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4. BASED ON ORIGIN OF SOURCE
 Natural Polymer :- Polymers which are isolated from
natural materials are called as Natural Polymers .
E.g. : Cotton , silk , wool , rubber .
 Synthetic Polymer :- Polymers which are synthesized
from low molecular weight compounds are called as
Synthetic Polymers .
E.g. : Polyethylene , nylon , terylene.
 Semisynthetic Polymers :- These polymers are mostly
derived from naturally occurring polymers by
chemical modification .
E.g. : Rayon
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5. BASED ON STRUCTURE
Linear Polymer :
Molecules form long
chains without
branches.
They can be place one
above the other and are
closely packed in space.
Results in high density,
tensile strength and high
M.P .
Eg: HDP, PVC
Branched polymers
Their molecules are
irregularly packed hence
they have low density,
Tensile strength and
melting point.
E.g. LDPE.
They have straight long
chain with different side
chain.
Cross-Linked Polymer :
The links involved are
called cross links. They are
hard, rigid .and brittle due
to their
network structure.
E.g. Bakelite, Melamine,
Formaldehyde resins,
Vulcanized rubber
It includes
interconnections between
chains .
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6. BASED ON MODE OF POLYMERISATION
Addition Polymerization Condensation Polymerization
Monomers must have either a double
bond or triple bond
Monomers must have two similar or
different functional groups
Produces no by-products By-products such as ammonia, water
and HCl are produced
Addition of monomers results in
polymers. Initiator are needed
Condensation of monomers result in
polymers. No initiators.
The molecular weight of the resultant
polymers is a multiple of monomer’s
molecular weight
The molecular weight of the resultant
polymer is not a multiple of monomer’s
molecular weight
Lewis acids or bases, radical initiators
are catalysts in addition
polymerization
Catalyst used in condensation are acids,
base, metal compounds etc.
Common eg of addition polymerization
are PVC, polyethene, Teflon etc.
Common examples of condensation
polymerization are nylon, bakelite, etc.
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8. Addition polymersiation
Initiation
Propagation
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9. Condensation (Step) Polymerization
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10. Based on molecular forces
Thermoplastics: The relatively weak intermolecular forces hold the molecules
in a thermoplastic together, so that the material softens when exposed to heat
and then returns when cooled to its original condition. Thermoplastics are the
bulk of linear and slightly branched polymers. Chain polymerization produces
all the major thermoplastics. Food packaging, insulation, vehicle bumpers and
credit cards are some examples.
Thermosets: Heating cannot reshape the thermosets. Thermosets are usually
three-dimensional networked polymers in which polymer chains have a high
degree of cross-linking. The cross linking limits the chains ' movement and
contributes to a solid material that makes thermosets strong and robust. They
are predominantly used in the automotive and construction industries. They
are also used for making toys, varnishes, hulls of boats and glues
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11. Elastomers: Elastomers are rubbery polymers that can be extended easily
to their unstretched length many times and that quickly return to their
original dimensions when the pressure is released. Elastomers are cross-
linked but have a low density of cross-link. Elastomers are composed from
rubber bands and other elastics.
If polymer is drawn into long filament like materiel whose length is at least
100 times it’s diameter, are said to be converted into fiber.
They have high tensile strength because of high intermolecular attractive
force like Hydrogen bonding.
Highly crystalline. E.g. Nylon, Terylene.
Fibre
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12. Low density polythene (LDPE)
•Low density polythene is prepared by
a number of methods. The common
method for the preparation of LDPE is
polymerization of ethylene monomer
at high pressure (1000 - 2000 atm)
and temperature (2500C) in presence
of oxygen peroxide hydro peroxide(
free radical generator). In this process
huge branched chains are formed
through out every long back bone
chain. The presence of branches repel
each other and the long chains are
not well fitted to each other having
some gap produce low density (0.91 to
0.925 gm/cc) polymer.
Preparation of some important addition polymers
Characteristics of low density polythene:
a) Low density polyethylene have density is low
(0.91 to 0.925 gm/cc).
b) It is branched chain addition polymer.
c) Semi crystalline polymer having crystallinity
45-50 percent.
d) Chemically inert, nonpolar and having
dielectric property zero.
e) Tough but flexible. Uses of low density polythene:
a) As LDPE is a good insulator they normally used for the preparation of electrical
wires and cables. b) Pouch pack, squeeze bottles, delivery pipes are prepared from
LDPE.c) Toys, refill for ball pen and ball pen also prepared from LDPE.
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13. High density polythene can be prepared by the polymerization of ethylene
monomer at low pressure (5 - 7 atm.) and temperature (60−700C) in presence
of Zieglar Natta catalyst like triethyl aluminium and titanium tetrachloride. In
this process of polymerization as there is absence of branch through out the
long chain back bone, the chains are well fitted to each other which makes the
polymer a high density (0.95 to 0.97 gm/cc) polymer.
High density Polythene(HDPE)
Characteristics of high density polythene:
a) High density polyethylene have high density (0.95 to
0.97 gm/cc). b) It is less branched.
c) Highly crystalline polymer having crystallinity 80-90
percent.
d) Chemically inert, nonpolar and having dielectric
property zero.
e) Highly tough but flexible.
Uses of high density polythene:
a) As HDPE is a good insulator they normally used for the preparation of high performance
electrical cables.
b) Due to inertness it is used for the storage of H2SO4, pipes for LPG gas and water reserver
also.
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14. Polytetrafluoroethene (Teflon/PTFE)
Teflon is manufactured by heating tetrafluoroethene with a free radical or
persulphate catalyst at high pressures. It is chemically inert and resistant to attack
by corrosive reagents. It is used in making oil seals and gaskets and also used for
non – stick surface coated utensils.
Polyacrylonitrile/PAN
The addition polymerisation of acrylonitrile in presence of a peroxide
catalyst leads to the formation of polyacrylonitrile.
Polyacrylonitrile is used as a substitute for wool in making commercial fibres
as Orlon. It is used for making synthetic carpets.
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15. TERYLENE OR DACRON
Polyamides
Nylon 6,6: It is prepared by the condensation polymerisation of
hexamethylenediamine with adipic acid under high pressure and at
high temperature.
Polyesters are used in fibers, films, and plastic bottles.
Nylon 6, 6 is used in making sheets, bristles for brushes and in
textile industry.
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16. Nylon 6: It is obtained by heating caprolactum with water at a high
temperature.
Nylon 6 (also called Perlon) is used for making strong, flexible fibers for
ropes and tire cord.
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17. Phenol - formaldehyde polymer Bakelite and related polymers)
Bakelite is a polymer made up of the monomers phenol and
formaldehyde. This phenol-formaldehyde resin is a thermosetting
polymer
These are obtained by the condensation reaction of phenol with
formaldehyde in the presence of either an acid or a base catalyst. The
reaction starts with the initial formation of o-and/or p-
hydroxymethylphenol derivatives, which further react with phenol to
form compounds having rings joined to each other through –CH2
groups. The initial product could be a linear product – Novolac used in
paints
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18. Novolac on heating with
formaldehyde undergoes cross
linking to form an infusible
solid mass called bakelite.
It is used for making
combs, phonograph
records, electrical
switches and handles of
various utensils.
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19. Melamine – formaldehyde polymer
Melamine formaldehyde polymer is formed by the condensation
polymerisation of melamine and formaldehyde.
It is used in the manufacture of unbreakable crockery.
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20. Copolymerisation
A copolymer is a polymer that is made up of two or more monomer species.
Copolymers have properties quite different
from homopolymers. For example, butadiene -
styrene copolymer is quite tough and is a good
substitute for natural rubber. It is used for the
manufacture of autotyres, floortiles, footwear
components, cable insulation, etc.
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21. Natural rubber
Rubber is probably the best known organic polymer and the only true
hydrocar- bon polymer found in nature.
Natural rubber is poly-cis-isoprene,
which is extracted from the tree
which is a colloidal dispersion of
rubber in water.
It is formed by the radical addition of
the monomer isoprene. Actually,
polymerization can result in either
poly-cis-isoprene or poly-trans-
isoprene—or a mixture of both,
depending on reaction conditions:
The cis-polyisoprene molecule consists of various chains held together by
weak van der Waals interactions and has a coiled structure. Thus, it can
be stretched like a spring and exhibits elastic properties.
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22. Vulcanisation of rubber:
Vulcanized rubber has much greater toughness and elasticity than
natural rubber. It withstands relatively high temperatures without
softening, and it remains elastic and flexible when cold.
Natural rubber becomes soft at high temperature (>335 K) and brittle at
low temperatures (<283 K) and shows high water absorption capacity. It is
soluble in non-polar solvents and is non-resistant to attack by oxidising
agents.
On a molecular level, vulcanization causes cross-linking of the cis-1,4-
polyisoprene chains through disulfide - S - S - bonds, similar to the cystine
bridges that link peptides . In vulcanized rubber, the polymer chains are linked
together so they can no longer slip past each other. When the material is
stressed, the chains stretch, but cross-linking prevents tearing.
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23. In the manufacture of tyre rubber, 5% of sulphur is used as a
crosslinking agent. The probable structures of vulcanised
rubber molecules are depicted below
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24. Preparation of Synthetic Rubbers
Neoprene or polychloroprene is formed by the free radical
polymerisation of chloroprene.
It has superior resistance to vegetable and mineral oils. It is used
for manufacturing conveyor belts, gaskets and hoses.
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25. Buna – N
Buna –N is obtained by the copolymerisation of 1, 3 – butadiene and
acrylonitrile in the presence of a peroxide catalyst.
It is resistant to the action of petrol, lubricating oil and organic solvents.
It is used in making oil seals, tank lining, etc.
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26. Biodegradable Polymers
Poly β-hydroxybutyrate – co-β-hydroxy valerate (PHBV)
PHBV is used in speciality packaging, orthopaedic devices and in
controlled release of drugs. PHBV undergoes bacterial degradation in
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27. Nylon 2–nylon 6
It is an alternating polyamide copolymer of glycine (H N–CH –COOH) 22
and amino caproic acid [H2N (CH2)5 COOH] and is biodegradable.
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28. Some Other Commercially Important Polymers
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29. THANK YOU
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