Which statement about thermosetting plastics is true?

Which statement about thermosetting plastics is true?

• A. They can be melted and reshaped repeatedly
• B. They harden permanently after curing and do not melt with reheating
• C. They are flexible and do not set
• D. They are identical to thermoplastics

Answer: (B)

Thermosetting plastics form a crosslinked network during curing, which locks the material into a rigid structure. Once cured, this network prevents flow, so heating doesn’t melt and reshape the material—instead, it may decompose or burn. This is why they harden permanently after curing and do not melt with reheating. This behavior differentiates them from thermoplastics, which can be melted and reshaped repeatedly because they lack that permanent crosslinked network.

Thermosetting plastics form a crosslinked network during curing, which locks the material into a rigid structure. Once cured, this network prevents flow, so heating doesn’t melt and reshape the material—instead, it may decompose or burn. This is why they harden permanently after curing and do not melt with reheating. This behavior differentiates them from thermoplastics, which can be melted and reshaped repeatedly because they lack that permanent crosslinked network.