CHE 101 Chapter Notes - Chapter 18: Nylon 6, Copolymer, Chloroprene

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3 Feb 2021
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Revision Notes on Polymers
Some Important Terms
Polymer
Large molecules having high molecular mass formed by combination of
number of small units called monomers.
Polymerisation
The process of formation of polymers from respective monomers.
Natural polymers
Found in plants and animals.
Examples: proteins, cellulose, starch.
Synthetic
polymers:
Synthesised in laboratory from natural material.
Example, nylon 6, 6 , Buna-S
Addition
Polymers
Formed by repeated addition of monomers having multiple bonds.
Homopolymers.
Addition polymers polymers formed from single monomeric species
Copolymers
Addition polymers formed from two different monomeric species
Condensation
polymers
Formed by repeated condensation of
different bi or tri-functional monomer units.
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Polymers are formed in two general ways.
a) In chain-reaction polymerization
Rad. + CH2 = CH2 → RadCH2CH2→ RadCH2CH2CH2CH → etc.
b) In step reaction polymerization,
Fibres
Long thin, threadlike bits of material that are characterized by great tensile
(pulling) strength in the direction of the fiber. The natural fibres – cotton, wool,
silk – are typical.
The lining-up is brought about by drawing – stretching — the return to random
looping and coiling is overcome by strong intermolecular attractions.
Elastomers
Possesses the high degree of elasticity that is characteristic of rubber: it can
be greatly deformed — stretched to eight times its original length e.g., buna N
and buna S,
When the stretching force is removed, the molecular chains of an elastomer
do not remain extended and aligned but return to their original random
conformations
Thermoplastic
polymers
Soften on heating and stiffen on
Cooling. e.g polythene, polystyrene, PVC
Thermosetting
polymers
Do not soften on heating and cannot be remoulded. Example, bakelite
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