Condensation polymers in building materials and plastics: Which of the following resins are formed by condensation polymerisation reactions?

Introduction / Context:
Condensation polymerisation involves step-growth reactions where small molecules (often water or methanol) are eliminated as monomers react. Many resins in wood products and laminates are condensation polymers, important for adhesives and decorative laminates in construction and furniture.

Given Data / Assumptions:

• Phenol–formaldehyde (PF), urea–formaldehyde (UF), and melamine–formaldehyde (MF) systems are listed.
• We must identify which are condensation polymers.

Concept / Approach:
PF, UF, and MF resins form through step-growth reactions between monomers (phenol/urea/melamine with formaldehyde), eliminating small molecules during curing. These resins are widely used as binders in plywood, particleboard, MDF, and high-pressure laminates due to good bonding and heat resistance (especially PF and MF).

Step-by-Step Solution:

Verification / Alternative check:
Polymer chemistry references classify PF, UF, MF as thermosetting condensation polymers, in contrast to addition polymers like polyethylene and polystyrene formed by chain-growth without by-product elimination.

Why Other Options Are Wrong:
Each individual resin listed is indeed a condensation polymer; hence the only comprehensive correct option is “All of these.”

Common Pitfalls:

• Confusing “condensation” with “addition” polymerisation; note the elimination of small molecules in condensation systems.
• Assuming all thermosets are condensation polymers; epoxies cure differently.

Final Answer:
All of these