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Comparison and Classification

I. Polymers are classified into four main types: homopolymers, copolymers, cross-linked polymers, and organic/inorganic polymers based on their molecular structure and composition. II. Polymerization can occur through two main mechanisms: addition polymerization which involves unsaturated monomers and is initiated, and condensation polymerization which uses functional group-containing monomers and proceeds in a step-wise manner. III. Plastics are categorized as thermosoftening or thermosetting depending on whether their polymer chains can be reshaped upon heating, with thermosoftening plastics having weaker bonds and thermosetting plastics having a cross-linked three-dimensional structure.

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227 views4 pages

Comparison and Classification

I. Polymers are classified into four main types: homopolymers, copolymers, cross-linked polymers, and organic/inorganic polymers based on their molecular structure and composition. II. Polymerization can occur through two main mechanisms: addition polymerization which involves unsaturated monomers and is initiated, and condensation polymerization which uses functional group-containing monomers and proceeds in a step-wise manner. III. Plastics are categorized as thermosoftening or thermosetting depending on whether their polymer chains can be reshaped upon heating, with thermosoftening plastics having weaker bonds and thermosetting plastics having a cross-linked three-dimensional structure.

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© © All Rights Reserved
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POLYMERS

CLASSIFICATION OF POLYMERS

THEORY

CLASSIFICATION OF POLYMERS
I] Homopolymers

II] Copolymers

They are obtained by a large


more
Number of same monomer.

They are obtain by a two or

i) Linear Homopolymer
randomly

i) Linear copolymer with

number of different
monomer.

joined monomer.
-AAAAAA-

ii) Branched Homopolymer


A
A

-A A A A- A A

-AABABB

ii) Linear copolymer with


alternately joined monomer.
- A B A B A B -

iii) Linear copolymer with block


way joined monomer.
- A A A B B A A A B B-

III] Cross-linked polymers


They are obtained by using polyfunctional monomer. It contains a
large molecule. Hence they are hard, strong, brittle & do not
soften on heating.
Trifunctional + Bifunctional --- Cross linked polymer
Eg. Backlite (O,P dimethylolphenol monomer is used)

POLYMERS

CLASSIFICATION OF POLYMERS

IV] Organic polymers


The polymer chain consists of
contain other
mainly carbon atom.
Eg. P.V.C, Polyethelene,
polymer.
Polyesters, DNA-RNA, etc.

THEORY

V] Inorganic polymers
The polymer chain
than carbon atom.
eg. Polysilane, Silicon

TYPES OF POLYMER
On the basis of origin polymers have following types.
i) Natural polymer
It is obtained
naturally.

ii) Synthetic polymer.


It is obtained by
synthetically
(by
chemical reactions)

eg. Cellulose,
acetate,
Proteins,
DNA- RNA.
natural rubber.

eg. Polyesters, nylons,

eg. Cellulose

Phenolformaldehyde.
Urea formaldehyde.

Cellulose nitrate,
Vulcanized

iii) Semi.
It is obtained by
modification of
natural polymer

POLYMERS

CLASSIFICATION OF POLYMERS

TYPES OF POLYMERIZATION
Addition polymerization

Condensation
polymerization
In this type we can used In this type monomer must
unsaturated monomer.
contain functional group.
Eg. Ethylene, propylene, Eg. OH, -COOH, -NH2, vinyl
chloride,
styrene, COOR, --COCl, etc.
butadiene, etc.
For polymerization there is a Catalyst may or may not be
need of initiator ie. Catalyst. used.
Eg. Free radical or Ionic
initiator.
Reactions involve three Reaction is stepwise (one
steps.
step).
ie.
Initiation,
chain i.e. Monomer reacts one by
propagation
&
chain one.
termination.
It is exothermic reaction. This reaction is always
Hence coolant is use as endothermic. Hence there is
temp controller. However to no need to control the temp.
trigger the reaction slight Reaction
requires
high
heating is necessary.
temperature.
Overall reaction is very Overall reaction is very fast.
slow.
There is no formation of There is formation of simple
byproduct.
byproduct like H2O, R-OH,
NaCl, etc.
Eg.
Polyethylene, Eg. Amide linkage (-CO-NHpolypropylene, etc.
),
Ester linkage (-CO-O-)
3

THEORY

POLYMERS

CLASSIFICATION OF POLYMERS

TYPES OF PLASTICS
Thermosoftening plastics
Thermosetting plastics
They are formed by addition They
are
formed
by
polymerization.
condensation
Eg. Polyethylene, PVC, etc. polymerization.
Eg. Nylon 66, nylon 6, etc.
They consist of linear long They
consists
three
chain polymer with limited dimensional
network
cross-links.
structure.
They consists polymer of They consists polymer of
smaller molecular weight.
higher molecular weight.
They are softened on They do not soften on
heating. Hence they can be heating. Hence they cannot
reshaped & reused.
be reshaped & reused.
They can be reclaimed from They cannot be reclaimed.
wastes.
There inter molecular bonds They are joined by strong
are weaker.
covalent bonds.
They are soft, weak & less They are hard, strong &
brittle.
more brittle.
They are soluble in suitable They are insoluble in
organic solvents, as their organic solvent, as their
bonds are weaker.
bonds are stronger.

THEORY

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