thermoplastic has 1 distinct synonym spread across 1 of its 2 senses. Each sense below keeps its own list, because a synonym belongs to a meaning and not to a word: swapping one sense's substitute into another sense's sentence is how a thesaurus makes writing worse. Its one recorded opposite is thermosetting.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
a material that softens when heated and hardens again when cooled
having the property of softening or fusing when heated and of hardening and becoming rigid again when cooled
“thermoplastic materials can be remelted and cooled time after time without undergoing any appreciable chemical change”
Synonyms, antonyms and the broader and narrower relations for thermoplastic come from Princeton University’s WordNet. Full sources and licences.