Polymer:- Polymer are the substances which are formed by combination of a large no. of monomer units through covalent bonds in a regular fashion
Examples:- Buna-s, Buna-N, polyesters-polyethene, Butadiene.
Classification of the Polymers :- Classification on the basis of repeating structural unit:-
- Homopolymers :- polymers whose repeating structural units are derived from only one type of monomer unit are called the Homo polymers.
Example:-ethylene poly propene poly vinyl chloride (PVC), polyisoprene neoprene.
- Copolymers:-Polymers whose repeating structural unit are derived from two or more types of monomer units are called Copolymers.
Example:-Buna-s, Buna-N, polyesters, alkyd resins, Bakelite.
Classification based upon source :-
- Natural Polymers:- polymers which are found in nature, in animals and plants are Called natural polymers.
Example:-Proteins, rubber, cellulose.
- Semi synthetic polymers:-These are mostly derived by naturally occurring polymers by the chemical modifications.
Example:-Cellulose, Vulcanized rubber.
- Synthetic polymers:-A large no. of man made polymers are extensively used in dail life. Which are called synthetic polymers.
Example:-Fibres, plastics rubbers etc.
Classification based on structure:-
- Linear polymers:-in these the monomer units are joined together to form long straight chain of polymer molecules. The various polymer chain than stacked over each other to form well packed well packed structure.
Example:- Polyethane, PVC poly esters etc.
- Branched chain polymer:-in these polymers the monomer units not only combines to produce the linear chain. But also forms braches of different lengths with main chain.
Example:- amylopectin, glycogen etc.
- Cross linked Polymers:-in these polymers the initially formed linear polymers are joined together to from three dimensional network structure and form againt molecule.
Example:- Bakelite, area_ Formaldehyde polymers.
Classification based upon mode of polymerisation:-
- Addition Polymers:-Addition polymers are formed by the repeated addition of a large no. of same or different monomers possessing double or triple bonds.
Example:-polybutadiene, polyvinyl chloride (PVC), polyethene
- Condensation polymers:-Condensation polymers are usually formed by repeated condensation reaction between two bifunctional or trifunctionalmonomer units usually with the elimination of small molecules like water like alcohol, ammania.
Example:- Nylon-6,6,Terylene, Bakelite etc.
Classification based upon Molecular Forces:-
- Elastomer:-the polymers in which the intermolecular forces of attraction between the polymer chains are weakest are called elastomers.
Example: – Natural rubber, Buna-S, Buna-iv etc.
- Fibres:-Polymers in which the intermolecular Forces of attraction are the strongest are called Fibres. These forces are due to H-Bonding and dipole-dipole, interactions.
Example:-(terelyne, daction, polyacrylointrile) etc.
Due to strong molecular forcesof attractions these polymers have high tensile strength and low elasticity.
- Thermoplastics:-Polymers in which the inter-molecular forces of attractions are between those of elastomers and Fibres are called Thermoplastics.
Example:-polyethene, polyvinyl chloride, nylon 6,6 etc.
- They are linear or slightly branched chain polymers which becomes hard at room temperature.
- These can be moulded into toys, buckets, telephones televisions etc.
- Thermosetting Polymers:-The semi-solid substances which on heating undergo permanent change in chemical composition to give hard and infusible solid mass due to extensive cross linking of molecules are called thermosetting polymers.
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