3. “Polymers are macromolecules formed by the
combination of large numbers of smaller repeating
units, called monomers”.
Polymers
4. Polymerization
“The process of combination of monomer molecules
together to form polymer chains is known as Polymerization”
5. Classification of Polymers
I. Classification based on Origin
II. Classification based on Structure
III. Classification based on Synthesis
IV. Classification based on Molecular forces
6. I. Classification based on Origin
(a) Natural Polymers
Polymers obtained from nature
Example: Cellulose, natural rubber, Starch, Proteins
(b) Synthetic Polymers.
Polymers prepared in laboratory
Example: PVC, Teflon, Nylon etc
7. II. Classification based on Structure
(a) Linear Polymers
Monomers linked together to form linear chains.
Example: Polyester, Nylon etc
(b) Branched chain Polymers.
Monomers linked together to form
main chain and many different branches.
Example: Low density Polyethylene (LDPE).
(c) Cross-linked Polymers
Monomers are cross linked together to
form three-dimensional net work.
Example: Bakelite, Melamine formaldehyde resin.
8. Questions
(1) The repeating units in polymer is called _____________________
(2) The process of combination of monomer molecules together to form
polymer chains is known as _________________.
(3) Give an example for natural polymer.
(4) ______________ is a synthetic polymers
(5) An example of Cross linked polymer is__________________
9. III. Classification based on Synthesis
(a) Addition Polymers
Polymers formed by repeated addition of monomers
without elimination of any by-products.
Example: Polyethene, Polyvinylchloirde (PVC)
Ethene Polyethene
Vinylchloride Polyvinylchloride
(b) Condensation Polymers.
Polymers formed by condensation of monomers with elimination of sample
molecules like water, ammonia etc. Example: Nylon 66.
(c) Chain Growth and Step Growth Polymers
Chain Growth: Polymers formed by chain reaction, chain grows by repeated
addition of monomers initiated by a radical initiator.
Example: Polyethene, PVC
Step Growth: Polymerization due to condensation process in several steps.
Example: Nylon 66, Bakelite
10. III. Classification based on Molecular Forces
(a) Elastomers
Polymers in which polymer chain is held together by weakest intermolecular
forces. Due to this weak force it can stretch easily. Example: Rubber
(b) Fibers
Polymers in which polymer chain is held together by strong intermolecular
forces like hydrogen bonding. Due to this strong force they have high tensile
strength. Example: Nylon 66, Cotton, Silk, Wool
(c) Thermoplastics
Polymers in which intermolecular force are intermediate between elastomers
and fibers. These become soft on heating and hard on cooling. No cross
linking on heating –cooling process. So can moulded again and again.
Example: Polytehylene, Polypropyelne etc
(d) Thermosetting plastics
The polymers hard on heating and once they set into a shape do not change
shape on heating again. On heating extensive cross linking between chains
occurs forming three dimensional net work.
Example: Bakelite
11. Questions
(1) Give an example for addition polymers_____________________
(2) ______________is an example of condensation polymer
(3) Monomers of Nylon 66
(4) An example of Chain growth polymer_____________
(5) An example of Step growth polymer is__________________
(6) Polymers in which polymer chain is held together by weakest
intermolecular forces is known as _________________
(7) In fibers polymer chain is held together by _____________
(8) -------------------- is a thermoplastics
(9) An example for thermosetting polymers________________
(10) The polymer in which heating leads to extensive three dimensional
net work____________________
