Which statement best describes thermosetting plastics?

Which statement best describes thermosetting plastics?

• A. They can be remelted and reshaped
• B. They form a permanently rigid material through a chemical change
• C. They are easily recycled by melting
• D. They are always biodegradable

Answer: (B)

Thermosetting plastics set into a rigid form through a chemical cross-linking reaction during curing, creating a permanent network. Once this network forms, heating cannot soften and remold the material because the links are irreversible. This is why they become permanently rigid and highly heat resistant. In contrast, thermoplastics soften and can be melted and reshaped, which is not true of thermosets. They’re not easily recycled by melting, and they aren’t inherently biodegradable. Examples include epoxy and phenolic resins, which cure to a hard, stable structure. This combination of permanent shape from chemical change and resistance to melting is what makes the statement describing a permanently rigid material through a chemical change the best description.

Thermosetting plastics set into a rigid form through a chemical cross-linking reaction during curing, creating a permanent network. Once this network forms, heating cannot soften and remold the material because the links are irreversible. This is why they become permanently rigid and highly heat resistant. In contrast, thermoplastics soften and can be melted and reshaped, which is not true of thermosets. They’re not easily recycled by melting, and they aren’t inherently biodegradable. Examples include epoxy and phenolic resins, which cure to a hard, stable structure. This combination of permanent shape from chemical change and resistance to melting is what makes the statement describing a permanently rigid material through a chemical change the best description.