Formaldehyde-based resins: which polymer family belongs to the class of formaldehyde resins used for hard, cross-linked thermosets?

Introduction:
Formaldehyde resins cover urea–formaldehyde, phenol–formaldehyde, and melamine–formaldehyde systems. They are classic thermosets used in laminates, molded parts, and surface finishes due to hardness, heat resistance, and dimensional stability.

Given Data / Assumptions:

• We seek a resin whose chemistry explicitly reacts with formaldehyde to form a cross-linked network.
• Other options list common thermoplastics unrelated to formaldehyde chemistry.

Concept / Approach:
Melamine–formaldehyde resins result from condensation of melamine with formaldehyde and cure into hard, glossy thermosets. Teflon, PET, and polycarbonate are thermoplastics prepared by entirely different monomers and mechanisms.

Step-by-Step Solution:
Identify formaldehyde resin family member: melamine–formaldehyde → correct.Eliminate non-formaldehyde thermoplastics (PTFE, PET, PC).Select option (a).

Verification / Alternative check:
Materials references list MF resins as decorative laminates (e.g., table tops), dishes, and coatings with high hardness.

Why Other Options Are Wrong:

• PTFE: fluoropolymer from tetrafluoroethylene; no formaldehyde.
• PET (Dacron): polyester from ethylene glycol + terephthalic acid.
• Polycarbonate: from bisphenol-A + phosgene or transesterification; not a formaldehyde resin.

Common Pitfalls:
Confusing “resin” as a generic term with formaldehyde-based thermoset chemistry; formaldehyde resins are a specific class.

Final Answer:
Melamine–formaldehyde resins