Which of the following is manufactured by addition (not condensation) polymerisation?

Introduction / Context:
Polymerisation mechanisms fall into two broad families: chain-growth addition and step-growth condensation. Identifying which mechanism produces a given commercial polymer is a common exam theme because it governs structure, by-products, and processing.

Given Data / Assumptions:

• Addition polymerisation: monomers add across double bonds; no small-molecule by-product.
• Condensation polymerisation: functional groups react, eliminating small molecules (e.g., water, methanol).
• Candidates include PTFE, PET, Nylon, phenolic, and melamine resins.

Concept / Approach:
PTFE forms by free-radical addition polymerisation of tetrafluoroethylene. In contrast, PET (Terylene) is a polyester from terephthalic acid/EG via condensation, nylons are polyamides from diamine/diacid (or lactam) via condensation, and phenolic/melamine resins are classic step-growth condensation networks.

Step-by-Step Solution:
Match PTFE to chain-growth of CF2=CF2 (no by-product) → addition.Identify PET/nylon/phenolic/melamine as step-growth with by-product formation.Select PTFE as the only addition example.

Verification / Alternative check:
Industrial PTFE is produced via suspension/emulsion polymerisation under free-radical initiators, confirming the addition route.

Why Other Options Are Wrong:
PET: condensation esterification reaction.Nylon: amide formation (condensation).Bakelite and melamine–formaldehyde: step-growth condensations forming thermoset networks.

Common Pitfalls:
Assuming “no by-product” equals thermoplastic only; forgetting that some condensation polymers can still be thermoplastics (e.g., PET, nylon) before crosslinking.

Final Answer:
Teflon (polytetrafluoroethylene, PTFE)