Polymers

Polymers

1. What is?

   • Is any of a class of natural or synthetic substances composed of very large molecules
     • Uses
       • Plastic buckets - Cups and saucers - Children’s toys - Packaging bags - Synthetic clothing materials - Automobile tyres - Gears and seals - Electrical insulating materials and Machine parts
       • The polymers are the backbone of four major industries: plastics, elastomers, fibres and paints and varnishes

2. Classification Based on Source

   • Natural polymers
     • Found in plants and animals. Can be: proteins, cellulose, starch, some resins and rubber.
   • Semi-synthetic polymers
     • Cellulose derivatives as cellulose acetate (rayon) and cellulose nitrate, etc.
   • Synthetic polymers
     • Plastic (polythene), synthetic fibres (nylon 6,6) and synthetic rubbers (Buna - S) are manmade polymers extensively used in daily life and industry

3. Classification Based on Structure of Polymers

   • Linear polymers
     • They consist of long and straight chains, some examples: high density polythene, polyvinyl chloride.
   • Branched chain polymers
     • They contain linear chains having some branches. Example: low density polythene
   • Cross linked or Network polymers
     • They usually formed from bi-functional and tri-functional monomers and contain strong covalent bonds between various linear polymer chains. Example: bakelite, melamine,

4. Classification Based on Mode of Polymerisation

   • Addition polymers
     • They are formed by the repeated addition of monomer molecules possessing double or triple bonds
   • Condensation polymers
     • They are formed by repeated condensation reaction between two different bi-functional or tri-functional monomeric units.

5. Classification Based on Molecular Forces

   • Elastomers
     • These are rubber – like solids with elastic properties. In theseelastomeric polymers, the polymer chains are held together by the weakest intermolecular forces. These weak binding forces permit the polymer to be stretched.
   • Fibres
     • They are thread forming solids which possess high tensile strength and high modulus. These characteristics can be attributed to the strong intermolecular forces like hydrogen bonding.
   • Thermoplastic polymers
     • They are linear or slightly branched long chain molecules capable of repeatedly softening on heating and hardening on cooling.
   • Thermosetting polymers
     • They are cross linked or heavily branched molecules, which on heating undergo extensive cross linking in moulds and again become infusible.

6. Diana Sofia Saavedera Rengifo 10°A

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