Thermosets vs thermoplastics: which listed material is a thermosetting plastic (i.e., crosslinks irreversibly on curing)?

Introduction / Context:
Thermosetting plastics form crosslinked networks during cure and cannot be remelted. Thermoplastics soften repeatedly on heating. Differentiating these classes is essential for specifying molding methods, recycling routes, and end-use temperature limits.

Given Data / Assumptions:

• PVC, polythene (PE), and polystyrene are common thermoplastics.
• Bakelite is a classic phenolic thermoset.
• We assume standard, unmodified grades.

Concept / Approach:
Phenol–formaldehyde (Bakelite) cures irreversibly into a crosslinked network, exhibiting high heat resistance, good dimensional stability, and solvent resistance. PVC, PE, and PS are linear or lightly branched thermoplastics; they can be softened and reshaped by heat.

Step-by-Step Solution:
Map each polymer to its class (thermoplastic vs thermoset).Identify Bakelite as a thermoset.Eliminate PVC, PE, PS as thermoplastics.

Verification / Alternative check:
Processing methods: Bakelite is compression/transfer molded and cured; the others are extruded or injection molded without irreversible chemical crosslinking.

Why Other Options Are Wrong:
PVC/PE/PS are melt-processable repeatedly; they do not undergo thermoset curing by default.

Common Pitfalls:
Assuming additives or crosslinking agents turn all plastics into thermosets; base resins remain thermoplastic unless intentionally crosslinked (e.g., XLPE).

Final Answer:
Bakelite