POLYMERS CLASSIFICATION :
Polymers are classifed by different ways
I) Based on source :
By this way polymers are classified into three types
1) Natural polymers :
These polymers are obtained from natural sources.They are of two types
a) Vegetable polymers (plant polymers) These polymers are obtained from plants e.g. cotton, jute, hemp, sisal, flex, linen, rubber
b) Animal polymers (protein polymers.) These are obtained from animals. These are polyamide polymers. e.g. wool, silk
2) Semisynthetic polymers :
These are chemically treated natural polymers. Generally these are modified cellulose fibres. Due to chemical treatment its properties like tensile strength, lustre and appearence are modified. 6. g. acetate rayon, viscose rayon, cupra-ammonium silk.
3) Synthetic polymers:
These polymers are obtained from chemical substances by polymerisation process. e g. nylon, terylene, polythene, PVC, teflon etc.
I) Based on the structure of polymers:
By this way paymers are classitied into three types
i) Linear polymers: These polymers are made up of long continuous chains without branching. e.g. polytlrene,PVC, tetlon, nylon, terylene.
2) Branched polymers : These polymers consist of long chain with small chain as a branch. e.g. poly propylene, glycogen, starch .
3) Network or cross linked polymers : These polymers consist linking of chain polymers by strong covalent bonds leads to network structure e.g. melamine, bakelite, vulcanized rubber etc.
III) Based on polymerisation process :
By this way polymers are classified into two types
1) Addition Polymers : These polymers are formed by addition of repeated one type monomer units without elimination 01 Dy product. In this type monomers are unsaturated compounds. e.g. orlon, teflon, polythene, PVC, buna-S.
2) Condensation polymers : These polymers are formed by condensation reaction between two different monomers. e.g. nylons, polysters, polyurethanes. Here small molecules like water, alcohol, HX are eliminated.
IV) Based on molecular forces :
The properties of polymers depend upon molecular forces. Molecular forces bind polymer chains either by hydrogen bonds or by vander Waal ’s forces. These forces are called intermolecular forces. By this way polymers are classified into four types
1) Elastomers : These polymers have elastic character like rubber. In these polymers, chains are held together by weak
intermolecular forces. e.g. neoprene, vulcanized rubber.
2) Fibres : In these polymers, the intermolecular forces of attraction between the polymer chains are strongest. Here chains are closely packed having high tensile strength and less elasticity. Here the forces are hydrogen
bonding.
e.g. nylon, terylene, silk. 3) Thermoplastic polymers :
These are linear or slightly branched chain polymers. Their properties are in between elastomers and fibres. On heating they becomes soft and on cooling becomes hard. e.g. polythene, polystyrene, PVC, teflon.
4) Thermosetting polymers :
Thesetare cross linked or heavily branched polymers and undergoes permanent change on heating. They cannot be remoulded or recycled. e.g. bakelite, urea -formaldehyde resin, melamine-fonnaldehyde resin.
V) Based on growth polymerisation :
By this method polymers are classified into two types.
1) Chain growth polymers (addition polymers) :
It involves the addition of monomer unit at the reactive end of growing chain across the double bond. e.g. polythene. Aikenes undergo growth chain polymerization when treated with small quantity of suitable initiator. Other examples PVC, orlon.
2) Step growth polymers (condensation polymers) :
Any pair of monomer molecules having functional group, they undergo series of condensation with elimination of water or alcohol or H-X molecule in step wise manner. e.g. Nylon-66, dacron, bakelite.
