Chemistry Industrial Chemistry PMDC Conceptual Practice
PMDC Verified Question 22 of 41
Which physical characteristic accounts for the widespread structural use of thermosetting condensation polymers?
A
Low glass transition temperatures that provide rubbery elasticity
B
High solubility in common polar organic solvents
C
High thermal stability and dimensional rigidity from dense covalent cross-linking
D
Facile remelting and infinite thermal recyclability
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option C: High thermal stability and dimensional rigidity from dense covalent cross-linking
Concept:

Thermosetting condensation polymers (e.g., Bakelite, melamine-formaldehyde) form dense three-dimensional networks of covalent bonds that prevent plastic deformation and thermal degradation.

Formula / Reaction:

Qualitative concept / No formula required.

Solution:

  • Covalent cross-links prevent chain slipping under mechanical loads and maintain structural integrity at high temperatures.


Why other options are incorrect:

  • Option A: Thermosets have high \(T_g\) values and are rigid solids at ambient conditions.


  • Option B: Highly cross-linked polymers are insoluble in organic solvents due to their covalent network.


  • Option D: Thermosets decompose rather than melt upon reheating and cannot be re-melted or recycled like thermoplastics.

Quality & Fidelity Assurance: Every question on BeambePrep is rigorously curated against the official PMDC syllabus with zero filler, zero out-of-syllabus content, and zero typos. When an authentic past paper originally contained a historical mistake or ambiguity from the examining board (such as UHS or NUMS), BeambePrep faithfully reflects the original paper while detailing the nuance and scientific consensus in the autopsy above.

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