Dacron (polyethylene terephthalate, PET) is best described as which of the following?

Introduction / Context:
Dacron is the trade name for PET fibre. PET is a condensation (step-growth) polyester used in fibres and bottle resins. Identifying its monomer pair distinguishes it from nylons and elastomers and explains ester linkages central to its properties and processing (melt spinning, blow molding).

Given Data / Assumptions:

• PET is made from terephthalic acid (or its dimethyl ester) and ethylene glycol.
• Small molecules (water or methanol) are eliminated during polymer formation.

Concept / Approach:
Using the DMT route, PET forms by transesterification with ethylene glycol producing methanol and oligomers, followed by polycondensation to high molecular weight. The adipic acid + hexamethylene diamine pair forms nylon-66 (a polyamide), not PET. PET is a thermoplastic, not a thermoset, and it is not an addition copolymer like SBR.

Step-by-Step Solution:

Verification / Alternative check:
Industrial PET processes commonly reference either PTA/EG or DMT/EG routes leading to the same polyester backbone.

Why Other Options Are Wrong:

• Adipic acid + HMD: nylon-66 (polyamide).
• Thermosetting: PET is thermoplastic.
• Styrene–butadiene addition: SBR, unrelated to PET.

Common Pitfalls:
Mixing up polyester and polyamide monomer pairs due to similar naming conventions.

Final Answer:
Condensation polymerisation product of dimethyl terephthalate (DMT) and ethylene glycol