Which statement best describes a key difference between thermosets and thermoplastics?

Which statement best describes a key difference between thermosets and thermoplastics?

• A. Thermosets can be remoulded by heating; thermoplastics cannot.
• B. Thermosets have inter-linked networks and do not melt; thermoplastics melt when heated.
• C. Thermoplastics are always stronger than thermosets.
• D. Thermosets are more recyclable than thermoplastics.

Answer: (B)

The main idea is how the polymer structure reacts to heat, which comes from cross-linking. Thermosets form a permanent, three-dimensional network during curing. Those cross-links lock the chains in place, so when you heat them they don’t flow or melt; they just deform or burn. Thermoplastics don’t have those permanent cross-links, so their chains can move when heated, causing the material to soften and melt, which means they can be remolded or recycled. That’s why the statement describing thermosets as having inter-linked networks and not melting, while thermoplastics melt when heated, is the best description. The other options don’t fit: remoulding a thermoset by heating isn’t possible in the same way as a thermoplastic; strength isn’t determined as “thermoplastics are always stronger”; and thermoplastics are generally more recyclable due to their ability to melt and reform, unlike thermosets.

The main idea is how the polymer structure reacts to heat, which comes from cross-linking. Thermosets form a permanent, three-dimensional network during curing. Those cross-links lock the chains in place, so when you heat them they don’t flow or melt; they just deform or burn. Thermoplastics don’t have those permanent cross-links, so their chains can move when heated, causing the material to soften and melt, which means they can be remolded or recycled.

That’s why the statement describing thermosets as having inter-linked networks and not melting, while thermoplastics melt when heated, is the best description. The other options don’t fit: remoulding a thermoset by heating isn’t possible in the same way as a thermoplastic; strength isn’t determined as “thermoplastics are always stronger”; and thermoplastics are generally more recyclable due to their ability to melt and reform, unlike thermosets.