Polycaprolactam (produced via ring-opening of caprolactam) corresponds to which nylon designation in commercial polyamide nomenclature?

Introduction / Context:
Nylon naming conventions can be confusing. Polycaprolactam is obtained by ring-opening polymerisation of caprolactam and is marketed as nylon-6. This contrasts with nylon-66, which is made from two monomers (hexamethylene diamine and adipic acid).

Given Data / Assumptions:

• Caprolactam contains six carbons.
• Nylon-6 uses a single monomer; nylon-66 uses a diamine + diacid pair.
• Trade names like Dacron and materials like rayon refer to different polymer families.

Concept / Approach:
For “nylon-X,” X indicates the number of carbons in the lactam (or amino acid) monomer for homopolyamides. Hence caprolactam (6 carbons) gives nylon-6.

Step-by-Step Solution:
Identify polycaprolactam as ring-opened caprolactam.Map “6 carbons” to nylon-6 designation.Eliminate unrelated options (polyester, cellulose).

Verification / Alternative check:
Data sheets list PA6 (nylon-6) as polycaprolactam with repeat unit –NH–(CH2)5–CO–.

Why Other Options Are Wrong:
Nylon-66: two monomers (6,6), not a lactam.Dacron: PET.Rayon: regenerated cellulose.Nylon-11: made from 11-carbon amino-undecanoic acid.

Common Pitfalls:
Assuming all nylons come from two monomers; some are single-monomer lactam systems.

Final Answer:
Nylon-6