Polymers and its Classifications

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Polymers and
classification of
polymers
By,
Joan.Alvares
198212

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Introduction
 Polymers are large molecules which are formed by repeatative monomeric
units
 The word POLYMER comes from a greek word where POLY means many
and MER means parts
 Polymer is used as a synonym for plastic
 All plastics are polymers but all polymers are not plastics.

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Types of polymers
 Natural polymer
 Homopolymer
 Copolymer
 Thermoplastic
 Thermosets
 Long chain polymers

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NATURAL POLYMERS
 Polymers which are formed by raw materials found in nature are
called natural polmers
 Some of the natural polymers include DNA and RNA
 Cotton , DNA , wool , wood are some naturally occuring
polymers

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HOMOPOLYMER
 Homopolymers are synthesised by single type of monomer.
 They consists of a long chain with bonding linkages between
each monomeric units
 This implies that the polymer has an identical monomericunitss
 Eg :polythene

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COPOLYMERS
 These are polymers formed by two or more different monomers
 This is called copolymerisation
 Eg :Buna S

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THERMOPLASTIC
 A type of plastic that can be softened by heating and
hardened cooling and then capable of softening by
heating.
 These posses intermolecular forces of attraction .
 Eg. PVC, Polyethylene,Nylon ,polystyrene

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THERMOSETS
 They are polymers which are cross linked or heavily branched
molecules
 They become hard and rigid on heating
 They do not soften on heating and cannot be reused
 Eg: Bakelite used in making combs , elctrical swtiches ,and
handles of various utensils

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Classification of polymers

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Based on source
1.Natural polymer
These are found in plants and animals eg: proteins , Cellulose, starch , rubber and resins
2. Semi –synthetic
These are modifications of the natural polymers eg:cellulose acetate( rayon)and cellulose nitrate.
3.Synthetic polymers
Polymers whuch are synthesised by the action of heat or low molecular weight compounds ( used in
daily life and industry) eg:plastic, synthetic fibres,and synthetic rubber.
RAYON

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BASED ON THE STRUCTURE
 Linear polymers : These are polymers have long and straight
linear chains eg: high density polythene, PVC
 Branched chain polymers: These are polymers having some
branches in their linear structure eg: low density polythene
 Cross-linked : These are formed strong intermolecular forces
which leads to linear and branched chain in their structure eg:
Bakelite , melamine etc

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BASED ON INTERMOLECULAR
FORCES
 Elastomers : These are elastic in nature but their polymeric chains are held together
by weakest intermolecular forces. Their weaker binding forces allow the polymer to
be stretched eg: BunaS , BunaN , Neoprene
 Fibres : They have high tensile strength and high modulus .they have strong
intermolecular forces like hydrogen bonding These strong forces lead to close
packing eg:nylon 6,6 , polyesters
 Thermoplastics :These are polymers which soften on heating and harden on cooling
. They posses intermolecular forces of attraction between elastomers and fibres eg:
polythene ,PVC
 Thermosetting plastics :They have strongest intermolecular forces of attraction.
They are cross linked or heavily branched molecules whuch on heating undergo
extensive cross linking and cannot be reused eg : bakelite

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BASED ON MODE OF
POLYMERISATION
1. Additional polymers
 Same kinds of Monomeric unuts are added
 Rapid chain which helps in activating the chain reaction
chemically
 Each step consists of a condition for another to proceed
 The 3 main steps are:
1. intiation 2. propagation 3. Elongation

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.
2. Condensation polymers
 It involves polymerisation of two different monomeric units by the
elimination of some simple product.
 It involves chemical reaction between reactive monomeric units
 They are slower than additional polymerisation and they need reactive
fuctional groups fr polymerisation .

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CHARACTERISTICS OF POLYMERS
 Low density
 Low coefficient of friction
 Good corrosion resistance
 Good mould ability
 Poor tensile strength
 Low mechanical properties
 Low temperature resistance
 Can be produced transparent and in different colours

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APPLICATIONS
 Medicine: many biomaterials especially heart valve replacements and blood
vessels are made up of polymers like dacron and Teflon .
 Consumer science : plastic containers of various size, shape and light weight
and economically less expensive than traditional containers.
 Industry : Automobile parts, pipes, tanks , packing materials are all used in
industrial markets
 Sports : play ground equipments , golf clubs , swimming pool ,protective
helmets are all produced by polymers.

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References
 Robin J.R and Lee VH : controlled drung delivery and
fundamental applications
 Jain N K : Controlled and novel drug delivery : CBS publication.

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THANK YOU