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Lecture # 04
Classification of Polymers
Polymer Science and Engineering
(TM-2052)
By: Muhammad Haseeb Iqbal
National Textile University
Concepts to be covered
 General classification of polymers on the basis of
Origin
• Structure
• Chemistry
• Thermal behavior
• Properties
• Morphological behavior
• Usage
•
On the basis of origin
Natural : Polymers that occur in nature in plants and animals and are very essential for life.

•
Starch, cellulose, protein, nucleic acid, natural rubber etc.
Semi synthetic: Polymers are derived from naturally occurring polymers by chemical modifications.

•
Viscose rayon, acetate rayon
Synthetic: Synthetic polymers are man-made polymers

•
Polyethylene, polypropylene, polystyrene, polyvinyl chloride (PVC), nylon, Bakelite etc.
On the basis of structure

Linear: Monomeric units are joined in the form of long straight chains, such polymers have high densities, high
tensile strength and high melting point.
•

Branched: Chain are mainly linear in nature but also possess some branches along the main chain. They have
less densities, lower tensile strength and low melting point
•

Polyethylene, nylons and polyesters
Low density Polyethylene (LDPE)
Crossed Linked: Monomeric units are linked together to constitute a three dimensional network. They are hard,
rigid, and brittle.
•
Bakelite, Melamine formaldehyde resin
Classification on the basis of structure
(a) Linear, (b) Branched, (c) polymer with crossed bonds and (d) network
On the basis of chemistry
Organic polymers: They have chains consisting of C-C linkages and have hydrogen, oxygen, nitrogen,
sulfur and halogen atoms in the side chains apart from carbon atoms.
Elementoorganic polymers: Macromolecules whose chains are composed of (i) carbon as well as
hetroatoms (except N, S, O, and halogen atoms) and (ii) inorganic chains


•

Polydimethylsiloxane
Inorganic polymers: Polymers containing no carbon atoms but have Si-Si, Si-O, N-PX, P-O, and B-O
linkages e.g. polysilanes, polysiloxanes, polyphosphazenes, polyphosporic acid, polyphosphates and
polyboron oxides
On the basis of thermal behaviour
Thermoplastics: These polymers consists of large number of independent and intertwined molecular
chains. When heated, these chains can slip past each other and cause plastic flow.

•


Polyethylene, polypropylene, PVC, nylon etc.
Thermosetting polymers: These are prepared from low molecular mass semifluid substances. When
heated in a mould, they get highly cross-linked to form hard infusible and insoluble products. The
common example is Bakelite.
Activity: Comparison between thermoplastics and thermosetting polymers
THERMOPLASTIC VS THERMOSETTING
THERMOPLASTIC
THERMOSETTING
(1) These soften and melt on
heating.
(2) These can be remolded recast
and reshaped.
(1) These do not soften on heating
but rather become hard in case
prolonged heating is done these
start burning.
(3) These are less brittle and
soluble in some organic solvents.
(2)These can not be remolded or
reshaped.
(4) These are formed by addition
polymerization.
(3) These are more brittle and
insoluble in organic solvents.
(5) These have usually linear
structures.
(4)These are formed by
condensation polymerization.
(5) These have three dimensional
cross linked structures.
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Polymers
(Based on Properties)
Thermoplastics
Elastomers
e.g. polystyrene (amorphous),
Polyethylene (crystalline), etc.
Thermoplastic
Elastomers (TPE)
e.g. polystyrene-b-poly
butadiene-b-polystyrene
(Kraton®)
Thermosets
e.g. phenol resin,
epoxy resin, etc.
Vulcanized
Elastomers
e.g. styrene-butadiene
rubber (SBR)
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Elastomers
• Cross linked (networked) rubbery polymers that can be
stretched easily
(3-10x original size)
• Rapidly recover original dimensions when applied stress is
released.
• Low degree of cross linking
Elastomers
• Uses – examination gloves, rubber bands, bouncing
balls, automobile parts
• Not recyclable
• Degrades (burns) when heat is added
• Natural elastomers – natural rubber, latex
On the basis of morphological behaviour

Polymer morphology is the arrangement of the polymer molecules. There are two type of possible
arrangements
On the basis of Usage
Form
Fiber
Plastics
Rubber
Type
Polymeric materials
Natural
Cotton, wool, silk, asbestos
Semisynthetic
Viscose rayon, acetate rayon
Synthetic
Polyolefins, polyamides, polyesters
Cellulosic plastics
Celluloid(First thermoplastic), cellophane
Vinyl plastics
Polyolefins, polystyrene, polyvinyl chloride,
polyvinyl acetate
Polyacryloids
Polyacrylic acid, polymethylmethacrylate
Natural
Polyisoprene
Synthetic
NBR, SBR, butyl rubber, polysulfides,
polysiloxanes
Water soluable
Modified starches, cellulose derivatives,
PVA,
Water insoluable
Phenol plasts, amino plasts, polyurethane
resins, epoxy and unsaturated polyester
resins
Resins
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Summary