Polymers are classified into different categories based on their physical properties and their response to heat. Bakelite occupies a unique position in this classification.
1. Nature of Bakelite:
Bakelite is one of the oldest synthetic polymers, chemically known as polyoxybenzylmethylenglycolanhydride. It is formed by the condensation reaction of phenol with formaldehyde.
2. Classification as Thermosetting:
A thermosetting polymer is a material that undergoes a chemical change during molding under heat and pressure, becoming permanently hard and infusible.
3. Structural Reason:
The key characteristic of Bakelite is its
extensive cross-linking. During the heating process in the mold, covalent bonds form between polymer chains, creating a rigid three-dimensional network.
4. Properties:
• Once set, Bakelite cannot be remelted or reshaped.
• It possesses excellent insulating properties and high heat resistance.
• It is brittle but maintains its shape under high temperatures.
Because of this irreversible hardening due to cross-linking, Bakelite is a classic example of a thermosetting polymer.