Leaving Certificate Technology – Materials Practice Test 2026: The Complete All-In-One Guide for Exam Success!

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.