Introduction of polymer

1. INTRODUCTION OF POLYMER
Prepared by- Mr. Vishal B. Thakare
Assistant Professor, PARUL UNIVERSITY
(M.Tech Chemical, SVNIT Surat)
vishalbt88@gmail.com

2. Polymer- It is type of molecule made up by the repetition of some
simpler unit monomer.
Polymerization- The process of formation of polymer from
respective monomers is called as polymerization.
Degree of polymerization(DP)- The number of repeating units(n) in
the chain is called degree of polymerization.
 Polymers with high degree of polymerization are called high
polymers.
 Polymers with low degree of polymerization are called
oligopolymers or short chain polymers
 Polymers do not exhibit strength for n<30. Optimum strength of
most of polymers is obtained at ‘n’ around 600. The useful range
of ‘n’ is from 200 to 2000.

3. Classification of polymer
Based on response
technology
Thermosetting Thermoplastic
Based on
polymerization
Addition Condensation
Based on
chemical
constituents
Homo polymer Co polymer Composite
Alternating Random Block Graft
Polyblend Plastic
alloy
Based on
structure
Physical Chemical

4. Physical Chemical
Crystalline Amorphous
Linear Branched Cross linked Stero Polymer
Isotactic Atactic
Syndiotactic

5. Thermosetting Polymers- Polymers which undergo some chemical
change on heating and convert into infusible mass is called thermoset
polymers. These polymers are crossed linked or heavily branched
molecules and can not be reused.
Ex.- Urea formaldehyde resin, Bakelite
Addition polymer- The addition polymers are formed by the repeated
addition of monomer molecules possessing double or tripple bond.
Ex.- Formation of polyethene from ethene
Formation of polypropylene from propene.
Condensation polymer- The condensation polymer are formed by
repeated reaction between two different bi-funcational or tri-
funcational monomeric unit with the elimination of small molecules
such as water, alchol, hydrogen chloride etc.
Ex.- Nylon 66,Nylon 6, Terylene (dacron)

6. Homopolymer- A Polymer resulting from the polymerization of a
single monomer called as homopolymer.
Ex.- Polyvinyl chloride
Copolymer- When two different types of monomer are joined in the
same polymer chain, polymer is called copolymer.
Ex.- Nitrile Rubber, Styrene butadiene rubber (SBR)
Alternating copolymer - In alternating copolymer two monomer are
arranged in alternating fashion.
Ex- -A-B-A-B-A-B-

7. Random copolymer- In random copolymers two monomers follow
the random order.
Ex.- -A-B-B-B-A-A-B-A-A-
Block polymer - In block copolymers one type of monomer group
joined to monomer of another group.
Ex.- -A-A-A-B-B-B-A-A-A-B-B-B-

8. Graft copolymer - In graft copolymers back bone of one monomer
joined to another monomer in their side chain.
Composite polymer - Composite polymers refer to those type of
polymer that result from the bonding two or more homogenous
material with different material properties to derive final product with
certain desired material and mechanical properties.
Polyblend polymer- It is mixture of two or more polymer.
Ex- mixture of vinyl resin with nitrile rubber.
Plastic alloy- Plastic alloy is the physical blending or chemical
grafting method.

9. Amorphous polymer- It is completely random, irregular and
dissymmetrical arrangement of polymeric chains.
Ex.- Rubber, Thermosetting plastic
Crystalline polymer- It is completely regular, symmetrical and
ordered arrangement of polymeric chains with uniaxial orientation.
Ex.- Fiber
Linear Polymer- If polymer units are joined in a linear fashion
polymers is said to be linear polymer.
Ex. -A-A-A-A-A-A-A-

10. Branched Polymer- When monomer units are joined in branched
manner is called branched polymer.
Ex.-
Cross polymer- A polymer is said to be a cross linked polymer if the
monomer units are joined together in a chain fashion.
Ex.-

11. Isotactic polymer- It is the type of polymer in which the
characteristic group are arranged on the same side of the main chain.
Ex.-
Syndiotactic polymer- It is the type of polymer in which the
characteristic group are arranged in an alternate fashion.
Ex.

12. Atactic polymer- It is the type of polymer in which the
characteristic group are arranged in an Irregular fashion around the
main chain.
Ex.

13. Physical & Chemical Properties of polymer-
1) Strength
 It depends upon the magnitude of force of attraction between
polymeric chains.
 In a cross-linked polymers, all chains are interconnected by
strong chemical covalent bond, resulting in a giant solid molecule,
extending in three dimensions. So they are strong and tough
materials, since the movement of intermolecular chains are totally
restricted.
 Strength of the polymer can be increased by increasing the
intermolecular force by the introduction of groups like carboxyl,
hydroxyl, chlorine, fluorine, nitrile along the chain. Polymers of
lower chain length are soft and gummy, while higher chain
polymers are hard and strong. By controlling the chain length, the
strength of the polymer can be varied from soft and flexible to
hard.

14. 2) Deformation (Plasticity)
 It is the slipping of one chain over the other on the application of
heat or pressure or both.
 This type of material, in heated state, readily takes the shape of the
mould and on cooling, the polymer becomes rigid in the moulded
shape, because plasticity decreases with fall of temperature.
 The linear or branched polymers show the greatest degree of
plastic deformation.
Elasticity
 It is the stretching and recoverance of original shape of the
polymeric chains after the removal of stress.

15. 3) Chemical Resistance and Solubility
 The chemical nature of monomeric units and their molecular
arrangement determines the chemical resistance of the polymer.
 Polymers having polar groups (-OH, –COOH, or Cl) swollen or
dissolved in polar solvents whereas polymers having nonpolar
groups (-CH3 or -C6H5) swollen or dissolved in non polar
solvents.
 polymers of more aliphatic character are more soluble in aliphatic
solvents whereas polymers of more aromatic character are more
soluble in aromatic solvents.
 The tendency to swell or solubility of polymers decreases with
the increase in chain length or molecular weight of polymer.
 In crystalline polymers, denser close packing of polymeric chains
makes the penetration of solvents or chemical reagents in the
polymeric material more difficult, so crystalline polymers exhibit
more chemical resistance or lesser solubility.

16.  Greater the degree cross-linking in the polymer, lesser is its
solubility and greater is its chemical resistance.

17. 4) Physical state of Polymers
 Relative arrangement of polymeric chains with respect to each
other may result in an amorphous or crystalline state of polymer.
 A crystalline state is characterized by a completely regular,
symmetrical and ordered arrangement of polymeric chains with
uniaxial orientation.
 In such polymers, the crystallites provide required hardness,
rigidity and heat resistance.
 In the crystallization process it has been observed that relatively
short chains organize themselves into crystalline structure more
than longer molecules.
 Linear and branched polymers do not form crystalline solids
because their long chains prevent efficient packing in a crystal
lattice.
 Crystalline polymer possess clear melting point.

18.  An amorphous state is characterized by a completely random,
irregular, and dissymmetrical arrangement of polymeric chains.
 Amorphous polymer do not possess clear melting point.
5) The glass transition temperature (Tg)-
 It is the temperature at which the internal energy of the chains of
the polymer increases such that the chains just starts leaving their
lattice sites. During this temperature transformation of a polymer
from a rigid material to one that has rubber like characteristics
occur.
 Below glass transition temperature (Tg), polymers are usually
hard, brittle and glass-like in mechanical behavior.
 Above glass transition (Tg), polymers are usually more soft,
flexible and rubbery (elastic)-like in mechanical behavior.
 It depends upon chain length , extent of cross linking barrier
which hinders the internal rotation around the chain links and rate
of heating or cooling.

19.  A cross linked polymer does not possess any Tg because such
polymer does not soften and is destroyed at a high temperature.
 Tg of a linear polymer is lower than that of a partially cross linked
polymer because the chains in a linear polymer are held together
by weak vanderwaal forces which can be overcome by providing
even small amount of energy.
 Crystalline polymers have no glass transition temperature as it
lead to dense close packing of polymeric chains.

21. Mechanical Properties
Stress-Strain Curve-

22. Stress- Strain curve-

23. Mechanical Properties
1) Hardness
 The ability of a polymer to resist scratching, abrasion, cutting, or
penetration.
 It is measured by its ability to absorb energy under impact loads.
 Hardness is associated with strength
 It is closely associated with material structure, composition.
2) Toughness
 It is the amount of energy a polymer can absorb before actual
fracture or failure takes place.
 It is the ability of a polymer to withstand both plastic and elastic
deformation.

24. 3) Stiffness
 It is the measure of the ability of material to resist deformation.
4) Strength-
 Strength represent the capacity of the material to with stand
external force or internal force resistance per unit area .Depending
upon nature of force strength can be classified as tensile,
compressive, shear and impact.
5) Resilience
 It is the elastic energy released by the material as result of stress
removal. It is measured by finding out area under stress- strain
curve within elastic limit.
 It gives capacity of the polymer to bear shocks and vibrations.

25. Polymer Based Industries-
1) Plastics-
2) Rubber-
3) Fiber-
4) Coating-