Polymers are large molecules formed from repeated linking of smaller molecules called monomers. There are two main types of polymers: thermoplastics and thermosetting plastics. Thermoplastics can be softened on heating and hardened on cooling, allowing for reshaping. Thermosetting plastics form cross-linked bonds that prevent reshaping after the initial heating and molding. Common thermoplastics used in engineering include nylon, polycarbonate, polyethylene terephthalate, and polypropylene. Elastomers are polymers that can stretch over 100% and regain their original shape, such as natural and synthetic rubbers used in grips, shoe soles, and adhesives. Polymer properties can be modified by

1. POLYMERS

2. INTRODUCTION
 A word polymer is a combination of two greek words, “poly”
means “many”and “meros” meaning “parts or units”.
 A polymer is
1.a large molecule
2. formed from repeated linking of the smaller molecules called
“monomers”.
 More monomer molecules joined in units of long polymer.

3. THERMOPLASTIC POLYMERS
 They are
1. linear or slightly branched long chain polymers,
2. softened on heating,
3.reversibly hardened on cooling repeatedly.
 Example: Polyvinyle chloride

4. THERMOSETTING PLASTICS
Once heated and moulded, these
plastics cannot bereheated and
remoulded.
 molecules are cross-linked in three
dimensions and this is why they cannot
be reshape and recycled.
 the bond between themolecules is very
strong.

6. THERMOPLASTICS
Most commonly used engineering
thermoplastics as matrices.
 nylon.
Poly carbonate (PC).
Polyethelene terephthalate(PET).
Polypropelene (PP).
Stronger and stiffer but lower toughness.
Have engineering as well as advanced
applications.

9. POLYETHYLENE TETRAPHALATE(PET)

10. POLYPROPELENE(PP)

12. ELASTOMERS
a natural or synthetic polymer having
elastic properties, e.g. rubber.
a polymeric material.
elongation greater than 100% and a
significant amount of resilience.
Cross linkings in many elastomer carried
out in a process called
vulcanization(heating with sulphur about
140˚C).

13. CLASSIFICATION OF
ELASTOMERS
Natural Rubber
Synthetic rubber
 Polyisoprene
 Styrene butadiene rubber(SBR)
 Chloroprene, Polybutadiene
 Nitrile rubber, butylerubber,Silicones,
 Ethylene propylene diene monomer(EPDM),
etc
 Thermoplastic elastomers.

14. APPLICATIONS OF
ELASTOMERS
Grips or cameras,
Razor handles,
Medical devices,
Shoe soles,
Adhesives ,etc.

15. TWO MAIN SYNTHETIC APPROACHES
Addition polymerization
Simply adding monomers together –
synthetic plastics
Condensation polymerization
Combination by exclusion of a small
molecule (usually water) – extensively
used by nature

16. POLYMER PROPERTIES TUNED BY
MODIFYING ADDED GROUPS
Density
Polarity
Chain branching
Cross linking
Chain length

19. POLYMERS HAVE REVOLUTIONIZED
CONTAINERS AND OTHER HOUSEHOLD ITEMS