all about polymers

1. Introduction To
Polymer

2. Introduction to
Polymers
Poly = many, mer = unit, many units
Polymer science is relatively a new
branch of science . It deals with
chemistry physics and mechanical
properties of macromolecule .

3. It consist of large no. of repeating units
known as monomers
The no. of repeating units in a chain of
polymer is known as degree of
polymerization

4. Classification schemes
Classification by Origin
Synthetic organic polymers
 Biopolymers (proteins, polypeptides,
polynucleotide, polysaccharides, natural
rubber)
 Semi-synthetic polymers (chemically
modified synthetic polymers)
 Inorganic polymers (siloxanes, silanes,
phosphazenes)

5. Classification by Monomer Composition
Homopolymer Copolymer
Block Graft Alternating Statistical
Homopolymer
Consist of only one type of constitutional repeating unit (A)
AAAAAAAAAAAAAAA
Copolymer
Consists of two or more constitutional repeating units (A.B )

6.  Statistical copolymer (Random)
ABAABABBBAABAABB
two or more different repeating unit
are distributed randomly
 Alternating copolymer
ABABABABABABABAB
are made of alternating sequences
of the different monomers
 Block copolymer
AAAAAAAAABBBBBBBBB
long sequences of a monomer are
followed by long sequences of another
monomer
 Graft copolymer
AAAAAAAAAAAAAAAAAA
B B B
B B B
(d)
Several classes of copolymer are possible

7. Classification by Chain structure (molecular architecture)
Linear chains :a polymer consisting of a single continuous chain of
repeat units
Branched chains :a polymer that includes side chains of repeat
units connecting onto the main chain of repeat units
Hyper branched polymer :consist of a constitutional repeating unit
including a branching groups
Cross linked polymer :a polymer that includes interconnections
between chains
Net work polymer :a cross linked polymer that includes numerous
interconnections between chains
Linear Branched Cross-linked Network
Direction of increasing strength

8. Classification by Thermal Behavior
Thermoplastics - materials become fluid and processible upon
heating, allowing them to be transformed into desired shapes that
are stabilized by cooling.
Thermosets - initial mixture of reactive, low molar mass compounds
reacts upon heating in the mold to form an insoluble, infusible
network
Classification by Application
 Plastics
 Fibers
 Elastomers
 Coatings
 Adhesives
Classification Based on Kinetics or Mechanism
Step-growth
Chain-growth

9. Polymerization mechanisms
- Step-growth polymerization

10. Stage 1
Consumption
of monomer
n n
Stage 2
Combination
of small fragments
Stage 3
Reaction of
oligomers to give
high molecular
weight polymer
Step-Growth Polymerization

11. Polymerization mechanisms
- Chain-growth polymerization

12. Chain polymerization
Radical polym.
The C=C is prefer
the Polym. by R.P.
and also can be
used in the steric
hindrance of the
substituent
Ionic polym.
Anionic polym. Cationic polym.
X X X
radical cationic anionic
Electron with drawing
substituent decreasing
the electron density on
the double bond and
facilitate the attack of
anionic species
such as cyano and
carbonyl
δ+ δ-
CH2=CH Y
Electron donating
substituent increasing
the electron density on
the double bond and
facilitate the attack of
cationic species
such as alkoxy, alkyl,
alkenyl, and phenyl
δ- δ+
CH2 =CH Y

13. Polymer Degradation
 Polymer degradation is a change in the properties – tensile
strength, colour, shape, etc of a polymer or polymer based
product under the influence of one or more environmental
factors such as heat, light or chemicals.
 The term 'biodegradation' is limited to the description of
chemical processes (chemical changes that alter either the
molecular weight or solubility of the polymer)

14. Degradation:
 CHEMICAL DEGRADATION
 BIOLOGICAL DEGRADATION
 MECHANICAL DEGRADATION
 CHLORINE INDUCED CRACKING
 THERMAL DEGRADATION
 PHOTO DEGRADATION

15. Biological Degradation
 Biodegradable plastics can be biologically degraded by
microorganisms to give lower molecular weight
molecules.

16. Chlorine induced cracking
 Another highly reactive gas is chlorine, which will
attack susceptible polymers such as acetal resin and
polybutylene pipe work.
 There have been many examples of such pipes and
acetal fittings failing in properties in the US as a result
of chlorine-induced cracking.

17. Chemical Degradation:
Polymers can be degraded by solvolysis and mainly
hydrolysis to give lower molecular weight molecules.
The hydrolysis takes place in the presence of water
containing an acid or base.
Polymers are susceptible to attack by atmospheric
oxygen, especially at elevated temperatures
encountered during processing to shape.

18. Thermal degradation
 Thermal degradation of polymers is molecular
deterioration as a result of overheating. At high
temperatures the components of the long chain
backbone of the polymer can begin to separate
(molecular scission) and react with one another to
change the properties of the polymer. The chemical
reactions involved in thermal degradation lead to
physical and optical property changes relative to the
initially specified properties.

19. Photo degradation
 One of the disadvantages of using polymers in high
temperature conditions or in outdoor applications –
degradation
 environment negatively influences the service life.
 This process is called weathering - ageing an
irreversible chemical process,
 undesired changes of properties of the polymers,
 discoloration and loss of mechanical properties

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