A thermoplast is a
polymer (plastic)
material that softens and melts upon heating. On
molecular level a thermoplast looks much like a plate of
spaghetti: the spaghetti strands represent the molecule chains. Because there are no connections between the molecule chains, the material can easily be deformed, especially when heated. (You can observe this when you pour a too hot liquid into a
plastic cup, the kind that comes out of
coffee machines: it will turn back into the flat piece of plastic that it was made out of).
Most plastics that you come across in daily life are thermoplasts: PE (polyethylene), PP (polypropylene), PVC (polyvinylchloride)..