Polymers Class 12 Notes - Chapter 15

Polymers are derived from monomers which consist of repeating structural units of high molecular mass macromolecules. They may occur in natural or synthetic form and are classified in many ways such as based on origin, structure, etc.

Classification of polymers

Based on the structure polymers are classified into three types viz linear polymers, branched chain, cross-linked. Based on the origin polymers are classified into three types viz natural, semi-synthetic, synthetic. Some examples of synthetic polymers include nylon, polypropylene, polyvinyl chloride.

Classification of polymers based on mode of polymerization

Based on the mode of polymerization, polymers are classified as addition polymers and condensation polymers.

  • Addition polymers -These polymers are formed by the repeated addition of monomer molecules possessing either double or triple bonds. Example, the formation of polypropene from propene. Homopolymers are defined as the polymers formed by the polymerization of a single monomeric species. One best example is polythene.
  • Condensation polymers – When polymers are formed by a repeated condensation reaction between two different tri-functional or bi-functional monomeric units they are called condensation polymers. Example, nylon 6, terylene, etc.

Few Important Questions

  1. Distinguish between condensation polymerization and addition polymerization.
  2. Write the monomeric repeating units for Nylon-6,6.
  3. Define and give two examples of synthetic polymers and natural polymers.
  4. Explain the process of obtaining dacron from ethylene glycol.
  5. What is copolymerization? Give an example
  6. Write the difference between thermosetting polymers and thermoplastics with examples.

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Practise This Question

The number of turns in the coil of an ac­ generator is 5000 and the area of the coil is
0.25m2. The coil is rotated at the rate of 100 cycles/sec in a magnetic field of 0.2 W/m2. The peak value of the emf generated is nearly