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ASSIGNMENT ON POLYMER SCIENCEAssignment topic: Polymer classification

Course name: Polymer ScienceCourse code: TE-133

SUBMITED BY:ID: 131-23-3298

131-23-3340131-23-3341131-23-3347131-23-3505131-23-3508

Department: TESection: B

SUBMITED TO:Khondoker Samaher Salam

LecturerDepartment of natural sciences

Daffodil International University.Date of Submission: 27.11.2013.

Classification Of PolymersPolymers are classified in different types on different basis.

Classification based on source:-• On the basis of sources of polymers they are classified in three types.a) Natural polymers -

• Polymers either obtained from plants or animal are called natural polymers. They are called plant and animal polymers.Ex. Cellulose, Jute, Lichen, Silk, Wool, Leather, RNA, DNA, Natural rubber.

Natural rubber

b) Semisynthetic polymers -

• The polymers obtained by simple chemical treatment of natural fibers to improve

their physical properties like lustrous nature, tensile strength are called semisynthetic fibers.

• Ex. Acetate rayon, cup ammonium silk, viscous rayon.

c) Synthetic fibers-

• The fibers obtained by polymerization of simple chemical molecules in laboratory are

synthetic fibers. ‘- Ex. Nylon, terylene, polyethene, polystyrene, synthetic rubber, nylon,

pvc, bakelite, teflon etc.

Classification based on the structure of polymers :-

• On the basis of structure they are classified in three types -

a) Linear polymers -

• In these polymers monomers are linked with each other and form a long straight chain.

• These chains has no any side chains.

Ex. Polyethene, PVC, Nylons, polyesters etc.

• Their molecules are closely packed and have high density, tensile strength, and melting point.

b) Branched polymers -

• They have a straigh long chain with different side chains.

•Their molecules are irregularly packed hence they have low density,

Tensile strength and melting point.

Ex. polypropylene (sidechain —CH3), amylopectin and glycogen.

c) Network or cross linked polymers -

• In these monomeric units are linked together to constitute a three dimensional network.

•The links involved are called cross links.

They are hard, rigid .and brittle due to their network structure.

Ex. Bakelite, melamine, formaldehyde resins, vulcanised rubber etc.

•Classification based on polymerization process :-

On this basis they are classified in two types -

A) Addition polymers -

The polymers formed by the addition of monomers repeatedly without removal of by

products are called addition polymers. These polymers contains all the atoms of monomers

hence they are integral multiple of

monomer unit.

Ex. Orion, teflon, polyethene, polypropylene, PVC.

- The monomeric units are generally alkenes and its derivatives.

B) Condensation polymers -

They are formed by the combination of two monomers by removal of small molecules like

water, alcohol or NH3. They have ester and amide linkage in their molecules. Their

molecular mass is not the integral multiple of monomer units.

Ex. Polyamides (Nylons), polyesters, polyurethans.

Classification based on molecular forces :-• Mechanical properties of polymers like tensile strength, toughness, elasticity depends upon intermolecular forces like van-der waals forces and hydrogen bonding.• On the basis of these forces they are classified as.

A) Elastomers -• These are the polymers in which polymer chains are held up by weakest attractive forces.• They contains randomoly coiled molecular chains having few cross links.• As the stain is applied polymer get stretched and as the force is released polymer regain its original position.• These polymers are elastic and called elastomers.Ex. Neoprene, vulcanised rubber, Buna-S, Buna -N.

B) Fibers-• They have high intermolecular attractive force like H-bonding.• They have high tensile strength and used in textile industries.Ex. Nylon-6, Nylon-66, Terylene.

C) Thermoplastic polymers -• These are the polymers having intermolecular forces between elastomers and fibers.• They are easily moulded in desired shapes by heating and subsequent cooling at room temperature.• They my be linear or branched chain polymers.• They are soft in hot and hard on coding.Ex. Polythene, polyesterne, PVC.

D) Thermosetting polymers -

• This polymer is hard and infusible on heating.

• These are not soft on heating under pressure and they are not remolded.

• These are cross linked polymers and are not reused.

Ex. bakelite.

Bakelite

•Classification based on Mesomer involved in the polymer:-

On the basis of,polymers are called homopolymers or heteropolymers.•Homopolymer- These are composed of any one type of mesomer.

Ex. Polyethene

•Heteropolymer- These are composed of more than one type of mesomer. These are

called co-polymers.A co-polymer may be of several kinds, depending upon the way the mesomers exist in the polymer chain.(i) A random co-polymer has the different mesomers in random sequence:

(ii)An alternating co-polymer has the following sequence mesomers:

(iii)A block co-polymer has the different mesomers in blocks of individual species:

(i)A graft co-polymer has blocks of one species of mesomer attached to the chain of another species in a way which makes it appear as if blocks of one type of mesomerhave been grafted on to the chain of another type:

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