Polymer basics — identify the wrong statement:\nChoose the statement that is incorrect regarding polymer classifications and properties.

Introduction / Context:
This conceptual item checks familiarity with polymer terminology (homopolymer vs. copolymer) and the qualitative ranking of intermolecular forces across major polymer classes (elastomers, thermoplastics, fibres). It also probes understanding of vulcanisation effects on rubber elasticity and resilience.

Given Data / Assumptions:

• Elastomers have the weakest cohesive forces and low glass-transition temperatures.
• Thermoplastics exhibit intermediate cohesive forces and softening on heating.
• Fibres (e.g., nylons, aramids) possess highly oriented chains and strong intermolecular forces, often hydrogen bonding.

Concept / Approach:
Correct qualitative ordering: elastomers (weak) < thermoplastics (intermediate) < fibres (strong). Vulcanisation increases rubber’s elastic recovery and reduces plastic flow compared with the raw gum, so “more elastic” is acceptable in the everyday engineering sense of resilience and shape recovery. The only patently incorrect statement supplied is that thermoplastics “always have stronger intermolecular forces than fibres,” which reverses the accepted order.

Step-by-Step Solution:

Verification / Alternative check:
Materials texts place high-performance fibres at the top of the cohesion/modulus scale because of orientation and strong secondary bonding (and, in some cases, crystallinity and hydrogen bonds).

Why Other Options Are Wrong:

• Homopolymer/copolymer definitions are standard.
• Vulcanised rubber’s improved elastic recovery is a well-known outcome.
• Thermoplastics intermediate forces: widely accepted qualitative description.

Common Pitfalls:
Confusing “percent elongation at break” (which may decrease upon curing) with elastic recovery; elasticity here refers to resilience and shape-return capability.

Final Answer:
Thermoplastics always have stronger intermolecular forces than fibres.