Which outcome results when a polymer's cross-linking density rises above a critical threshold under sustained load?

💡 Explanation

Increased cross-linking hinders chain mobility in the polymer, triggering **covalent bonding saturation**, because chains can no longer easily slide past each other. Therefore, the material's elasticity drops and it becomes prone to brittle fracture, rather than deforming elastically due to chain disentanglement.

• Which consequence results when thermal vibration overcomes **van der Waals forces** in polymer films?
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• Which outcome occurs when a nuclear power plant's cooling system fails, during radioactive decay?
• Which outcome occurs when imperfections in optical fiber cause modal dispersion?