Which thermosetting cross-linked polymer is produced by the condensation reaction of phenol with formaldehyde in the presence of an acid or base catalyst?
Answer and explanation
Correct answer: D. Bakelite
- Step 1: Phenol reacts with formaldehyde in the presence of an acid or base catalyst via electrophilic aromatic substitution to form ortho- and para-hydroxymethylphenol derivatives.
- Step 2: Linear condensation of these intermediates yields Novolac, a fusible thermoplastic used in paints and varnishes.
- Step 3: When Novolac is heated with additional formaldehyde (hexamethylenetetramine), extensive cross-linking occurs across all three dimensions, forming a hard, infusible, cross-linked thermosetting polymer called Bakelite.
- Step 4: Bakelite is widely used for electrical switches, plugs, handles of utensils, and phonograph records.
Answer
Bakelite
Why not the others: 'Teflon' is an addition homopolymer of tetrafluoroethene (); 'Polystyrene' is an addition polymer of styrene (); 'Nylon-6' is a polyamide prepared from caprolactam.
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