chapter 15. INTRODUCTION TO POLYMER CHEMISTRY Class 12 Chemistry Textbook Solution

3. Answer the following.

i. Write the names of classes of polymers formed according to intermolecular forces and describe briefly their structural characteristics.


Polymers are categorized into distinct groups based on their intermolecular forces, including Elastomers, Fibres, Thermoplastic polymers, and Thermosetting polymers.

  1. Elastomers:

    • Elastomers exhibit a unique elasticity property, allowing them to stretch under external force and return to their original shape upon force removal.
    • These elastic polymers are held together by relatively weak van der Waals intermolecular forces.
    • A limited number of crosslinks between polymer chains enable the stretched elastomer to retract to its original form when the applied force is removed.
    • Examples of elastomers include Vulcanized rubber, Buna-S, Buna-N, and neoprene.
  2. Fibres:

    • Fibres are polymeric solids that can be drawn into threads and possess exceptional tensile strength, making them resistant to breaking under tension.
    • Their high tensile strength arises from strong intermolecular forces such as hydrogen bonding and dipole-dipole interactions.
    • These intermolecular forces result in a crystalline structure in fibres.
    • Common examples of fibres include Polyamides (nylon 6,6) and polyesters (terylene).
  3. Thermoplastic Polymers:

    • Thermoplastic polymers exhibit plasticity, allowing them to be easily shaped or molded.
    • They can repeatedly soften when heated and harden when cooled.
    • These polymers possess moderately strong intermolecular forces, which fall between the forces found in elastomers and fibres.
    • Examples of thermoplastic polymers include Polyethylene, Polystyrene, and Polyvinyls.
  4. Thermosetting Polymers:

    • Thermosetting polymers are rigid materials that can be shaped when heated but become permanently hardened once cooled.
    • Their hardening results from extensive cross-linking via covalent bonds formed during the hot molding or setting process.
    • Unlike thermoplastic polymers, thermosetting polymers cannot be softened or remolded by subsequent heating.
    • Notable examples of thermosetting polymers include Bakelite and urea-formaldehyde resin.

chapter 15. INTRODUCTION TO POLYMER CHEMISTRY Class 12 Chemistry Textbook Solution page 338