How many letters does the top answer for “a lightweight thermoplastic; used especially in packaging and insulation” have?

The most common answer is polyethylene (12 letters).

Crossword clue: a lightweight thermoplastic; used especially in packaging and insulation

2 answers found in Letterora's clue database (Wikidata facts, Open Trivia DB, WordNet and Webster definitions — all licensed sources).

polyethylene 12 letters wn-def

a lightweight thermoplastic; used especially in packaging and insulation

polythene 9 letters wn-def

a lightweight thermoplastic; used especially in packaging and insulation