In polymer engineering, caprolactam is polymerised to produce nylon-6. At what reactor temperature range (°C) is this condensation/ring-opening polymerisation typically maintained for efficient conversion?

Introduction / Context:
Nylon-6 is produced industrially by the ring-opening polymerisation of caprolactam. The reaction is commonly referred to as a condensation-type step growth with water participation, and it requires elevated temperature to open the lactam ring, achieve adequate molecular weight, and keep melt viscosity manageable for processing.

Given Data / Assumptions:

• The product is nylon-6 from caprolactam.
• We seek a realistic melt-phase reactor temperature window used in practice.
• Higher temperature promotes ring opening and polymer chain growth but must avoid thermal degradation.

Concept / Approach:
Caprolactam undergoes ring opening and polycondensation with added water (or generated in situ). Industrial reactors maintain a high temperature to drive equilibrium toward polymer formation and to reduce viscosity for efficient mixing and devolatilisation. Typical practice keeps temperature well above 200°C, commonly around 250–280°C, balancing conversion and stability.

Step-by-Step Solution:
Identify the reaction: caprolactam → nylon-6 via ring opening.Note industrial melt polymerisation is conducted at high temperature.Select the realistic range: 250 to 280°C.

Verification / Alternative check:
Process descriptions for nylon-6 list polymerisation near 250–280°C followed by finishing/annealing and devolatilisation to achieve target number-average molecular weight for fibers, films, or engineering resins.

Why Other Options Are Wrong:
-20 to 25°C and 50 to 75°C: far too low to open the lactam ring and achieve polymerisation.100 to 150°C: still insufficient; reaction would be extremely slow with poor molecular weight.

Common Pitfalls:
Confusing hot vs. cold emulsion polymerisation (used for SBR) with melt polymerisation of lactams; mechanisms and temperature needs are very different.

Final Answer:
250 to 280