1. POLYMER. .pptx

Polymers

1. Classification of polymers and polymerization process AMEENUL ISLAM KT ROLLNO : 1 MSc FT 2 nd year

2. INTRODUCTION The word polymer is derived from the Greek words (poly), meaning "many"; and (meros), meaning "part“ A polymer is a macromolecule made when hundreds of monomers join together to form long chains and the reaction by which they combine are termed polymerization Polymer is used as a synonym for plastic All plastics are polymers, but not all polymers are plastics 2

3. 3 BASIS OF CLASSIFICATION POLYMER TYPES ORIGIN/SOURCE NATURAL SEMI SYNTHETIC SYNTHETIC MONOMER HOMO POLYMER CO POLYMER STRUCTURE LINEAR BRANCHED CROSS LINKED MOLECULAR FORCES ELASTOMERS FIBER THERMOPLASTIC THERMOSETTING MODE OF FORMATION ADDITION POLYMER CONDENSATION POLYMER CLASSIFICATION OF POLYMERS

4. BASED ON ORIGIN Natural polymers are those isolated from natural materials e.g. Cotton , Silk, Wool, Rubber Synthetic polymer : polymers which derived by complete chemical synthesis e.g. Polyethylene, Nylon, PVC Semisynthetic polymers : These polymers are mostly derived from naturally occurring polymers by chemical modification to improve their physical properties or derived from partial chemical synthesis from natural source e.g.: CMC, MC 4

5. 2. BASED ON MONOMER Homo polymer : They are synthesized from a single type of monomer and consists of chain with identical bonding linkage to each monomer unit e.g. Polyethylene , PVC Co polymer : polymer consists of monomers of different chemical structures and process is called as copolymerization. e.g. Nylon 6,6 5

6. 3. BASED ON STRUCTUE Linear polymers Monomers are linked with each other and form a long straight chain These chains has no side chains Their molecules are closely packed and have high tensile strength and melting point Eg : HDPE, Nylon Branched polymers They have a straight long chain with different side chains Their molecules are irregularly packed hence they have low density, tensile strength and melting point Eg : LDPE 6

7. Cross-linked polymer In these monomeric units are linked together to constitute a 3D network The links involved are called cross links . They are hard, rigid and brittle due to their network structure Eg : Bakelite, Melamine 7

8. 4. BASED ON MOLECULAR FORCE Fibers A Fiber is long thin thread like strand of material that has a length much greater than its diameter They have high tensile strength because of high intermolecular attractive forces like hydrogen bonding and are highly crystalline Can be natural or synthetic e.g. Nylon 8

9. Elastomers They are solids with rubber like elastic properties Here polymeric chains are held together by weakest intermolecular forces (Van der Waals) so they are highly amorphous in nature e.g. Natural rubber, BUNA-S Thermoplastic These polymers are those which softens on heating and hardens on cooling (reversible) without any change in chemical composition and are recyclable Have Intermediate Van der Waals force broken by heating May be linear or branched e.g. Polyethylene, PVC, Teflon 9

10. Thermosetting Those polymers which become irreversibly hard on heating or by addition off chemicals These are not soft on heating under pressure and they are not remoulded Are cross linked polymers and are not reused e.g. Bakelite 10

11. 5. BASED ON MODE OF FORMATION Polymerisation is the process in which very smack molecules called monomers combine chemically with each other to produce a very large chain like molecule called polymer There are mainly two type of polymerisation reactions Addition polymerization Condensation polymerization 11

12. Addition polymerization 12 A carbon – carbon double bond is needed in the monomer A monomer is the small molecule that makes up the polymer. C C H H H H n e t h e n e h i g h p r e s s u r e / t r a c e O 2 c a t a l y s t C C H H H H n p o l y ( e t h e n e )

13. The polymer is the only product. Involves the opening out of a double bond. The conditions of the reaction can alter the properties of the polymer. Reaction proceeds by a free radical mechanism. Conditions are high pressure and an oxygen initiator. Oxygen often used to provide the initial free radical 13

14. Condensation polymerization Involves 2 monomers that have different functional groups.
They also involve the elimination of water or another small molecule.
Hence the term condensation polymer.
Monomer A + Monomer B = Polymer + small molecule (normally water).
Common condensation polymers include polyesters (the ester linkage) and polyamides (the amide linkage as in proteins). The example here is terylene , a polymer of benzene-1,4-dicarboxylic acid and ethane-1,2-diol. 14

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