Question

Phenol and formaldehyde undergo condensation to give a polymer (A) which on heating with formaldehyde gives a thermosetting polymer (B). Name the polymers. Write the reactions involved in the formation of (A). What is the structural difference between two polymers?

Answer 1

Reaction of phenol with formaldehyde to give polymer (A)

Phenol and formaldehyde undergo condensation to give polymer (A), which is Novolac.

The formation of Novolac is as follow:

Heating polymer (A) with formaldehyde to give polymer (B)

Novalac (polymer A) on heating with formaldehyde undergoes cross-linkage to form an infusible solid called Bakelite (polymer B).

The structural difference between Novolac and Bakelite

• Novalac is a linear-chain polymer, while Bakelite is a cross-linked polymer.
• Novolac is lighter than Bakelite.