Which statement regarding polymers is not correct?
(1) Thermosetting polymers are reusable
(2) Elast

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Question

Which statement regarding polymers is not correct?
(1) Thermosetting polymers are reusable
(2) Elastomers have polymer chains held together by weak intermolecular forces
(3) Fibers possess high tensile strength
(4) Thermoplastic polymers are capable of repeatedly softening and hardening on heating and cooling respectively

Accepted Answer

Correct Answer: A - Thermosetting polymers are reusableStep-by-step Solution:Thermosetting polymers undergo extensive cross-linking between polymer chains when heated for the first time, forming a rigid, three-dimensional network structure. This cross-linking is irreversible - once set, these polymers cannot be softened or remoulded on reheating. Therefore, they are NOT reusable. Examples include Bakelite, urea-formaldehyde resin, and melamine.Why other options are correct statements: Option B is correct - elastomers (e.g., natural rubber, neoprene) have polymer chains held together by very weak intermolecular forces, allowing chains to be stretched and snapped back. Option C is correct - fibres (e.g., nylon, terylene) have strong hydrogen bonding or dipole-dipole interactions giving them high tensile strength. Option D is correct - thermoplastics (e.g., polyethylene, PVC) can be repeatedly softened on heating and hardened on cooling because they lack cross-links.Key Concepts:Thermosetting polymers: Irreversible cross-linked network on heating; cannot be remoulded. Examples: Bakelite, vulcanised rubber.Thermoplastics: Linear or slightly branched; soften on heating, harden on cooling; reusable. Examples: polyethylene, PVC, polystyrene.Elastomers: Weak intermolecular forces; large elastic deformation. Examples: natural rubber (polyisoprene), neoprene.Fibres: Strong intermolecular forces (H-bonds, dipole-dipole); high tensile strength and high melting points. Examples: nylon-6,6, terylene.

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