Thermosetting plastic materials show which post-processing behaviour? Choose the statement that best captures their heat response after they have been formed and cured.

Introduction / Context:Thermosets (e.g., phenolics, epoxies, melamine) cure into crosslinked networks. Recognising their irreversible heat response is essential for processing choices and recycling considerations.

Given Data / Assumptions:

• After cure, the network is covalently crosslinked.
• Heating above the glass transition does not produce melt flow; decomposition may occur on excessive heating.
• Contrast with thermoplastics, which soften and can be remelted.

Concept / Approach:Crosslinking prevents chain slippage required for melting. Therefore, thermosets cannot be remelted or reshaped once set. Any attempt to process them like thermoplastics results in thermal degradation rather than controlled melt flow.

Step-by-Step Solution:Identify network nature after cure.Relate network to irreversible heat response.Select “Cannot be melted after forming.”

Verification / Alternative check:DSC/TGA data typically show no melting endotherm for cured thermosets, only glass transition and decomposition.

Why Other Options Are Wrong:Repeatedly melted / melt casting / spinning: describe thermoplastic behaviour.Reversible softening with reshaping: not applicable to crosslinked networks.

Common Pitfalls:Confusing uncured thermoset resin (processable) with the fully cured article (non-meltable).

Final Answer:Cannot be melted after forming