Fibre formation methods: melt spinning forces a polymer melt through spinnerettes into a cooler atmosphere to form filaments. Melt spinning is NOT suitable for which fibre class among the following?

Introduction / Context:
Spinning method selection depends on a polymer’s thermal stability and melt behavior. Melt spinning requires that the polymer be melted without significant degradation. Acrylic fibres (polyacrylonitrile-based) typically cannot be melt-spun because PAN decomposes before it melts; hence solution (wet or dry) spinning is used. In contrast, polyesters, nylons, polypropylene, and polyethylene are melt-spinnable.

Given Data / Assumptions:

• Melt spinning demands a stable molten state below decomposition temperature.
• We compare common fibre families and their standard spinning routes.

Concept / Approach:
Polyacrylonitrile exhibits cyclisation and degradation upon heating rather than forming a stable melt; therefore, it is solution-spun. Polyesters (PET), nylons (polyamides), polypropylene (PP), and polyethylene (PE) melt cleanly (within processing windows) and are conventionally melt-spun into filaments, then drawn and heat-set to develop properties.

Step-by-Step Solution:

Verification / Alternative check:
Fibre manufacturing texts consistently state that acrylics are solution-spun (e.g., from DMF/NaSCN systems) due to PAN’s thermal behavior.

Why Other Options Are Wrong:

• Polyester/nylon/PP/PE: standard melt-spun fibres in commercial practice.

Common Pitfalls:
Assuming all commodity fibres are melt-spun; acrylics are a key exception.

Final Answer:
Acrylic fibres