Polymers

Polymers

1. Polymers or macromolecules are high molecular mass substances consisting of large numbers of repeating units.

2. Sub categories of polymers

   • Natural polymers: are found in plants and animals (proteins, cellulose, starch,etc.)
   • Semi-synthetic polymers: cellulose derivates as cellulose acetate
   • Synthetic polymers: plastic, synthetic fibres and synthetic rubbers

3. Types based of the structure of the polymers

   • Linear polymers: consists of long and straight chains (polyvinyl chloride)
   • Branched chain polymers: contain linear chains with some branches (low density polythene)
   • Cross linked polymers: contain strong covalent bonds between various linear polymer chains (bakelite)

4. Addition polymers: are formed by the repeated addition of monomer molecules possessing double or triple bonds. (Polythene, teflon, orlon, etc.)

5. Condensation polymers: are formed by repeated condensation reaction between two different bi-functional or tri-functional monomeric units. (Bakelite and dacron)

6. Types based on molecular forces

   • Elastomers: Solids with elastic properties, such as rubber.
   • Fibres: Thread forming solids that possess high tensile strength and high modulus. Such as polyesters.
   • Thermoplastic: Linear or slightly branched long chain molecules capable of repeatedly softening on heating and hardening on cooling. Such as polythene.
   • Thermosetting: Cross linked or heavily branched molecules, which on heating undergo extensive cross linking in moulds and again become infusible. Such as bakelite.

7. By: Sofia Tamayo 10ºA

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