Concept check: identify the single WRONG statement about polymer fibres, rubber tackiness, melting behavior, and UV resistance (assume standard unstabilised materials).

Introduction / Context:
Polymer exam questions often mix true and false facts about processing and properties. Here we must find the single incorrect statement by checking each claim against typical materials and conditions.

Given Data / Assumptions:

• “Polymeric fibres” include commodity and technical fibres (e.g., PP, PAN, PET, nylon).
• “Uncured rubber” refers to raw, unvulcanised elastomer exhibiting tack.
• Thermoplastics may be amorphous or semicrystalline.
• Polyethylene (polythene) is considered without stabilisers or carbon black.

Concept / Approach:
(a) is wrong: many fibres are made by addition polymerisation (polypropylene fibres, polyacrylonitrile precursor fibres). (b) is correct: uncured rubber is tacky due to chain mobility and surface adhesion. (c) is broadly correct: many thermoplastics soften over a range; amorphous polymers lack a sharp melting point and exhibit glass transition; even semicrystalline grades show melting over a range. (d) is correct as worded: unstabilised PE degrades under UV, hence stabilisers or carbon black are commonly used.

Step-by-Step Solution:
Evaluate (a): demonstrably false → choose as the wrong statement.Confirm (b), (c), (d) as accurate under the given assumptions.

Verification / Alternative check:
Textile and fibre technology references list PP (addition polymer) as a staple fibre; UV resistance charts show PE needs stabilisation.

Why Other Options Are Wrong (i.e., not the wrong statement):
(b) Correct property of uncured rubber.(c) Consistent with thermal transitions in polymers.(d) Correctly notes poor UV resistance without additives.

Common Pitfalls:
Assuming “sharp melting” like small molecules; ignoring the role of crystallinity and molecular weight distribution.

Final Answer:
Polymeric fibres are never produced by addition polymerisation.