Thermoplastic, also known as a thermosoftening plastic, is a polymer that turns to a liquid when heated and freezes to a very glassy state when cooled sufficiently.

Most thermoplastics are high-molecular-weight polymers whose chains associate through weak Van der Waals forces (polyethylene); stronger dipole-dipole interactions and hydrogen bonding (nylon); or even stacking of aromatic rings (polystyrene).

Thermoplastic polymers differ from thermosetting polymers (Bakelite) in that they can be remelted and remoulded.

Many thermoplastic materials are addition polymers; e.g., vinyl chain-growth polymers such as polyethylene and polypropylene.

Special purpose plastics

Polytetrafluoroethylene (PTFE) (Teflon)
heat resistant, low-friction coatings, used in things like frying pans and water slides
Plastarch Material
biodegradable and heat resistant, thermoplastic composed of modified corn starch.
Polyurethane
insulation foam, upholstery foam
Bakelite
insulating parts in electrical fixtures (it is a thermosetting plastic, a.k.a. phenol formaldehyde or phenolic resin, that can be moulded by heat and pressure when mixed with a filler-like wood flour or can be cast in its unfilled liquid form.)
Polylactic acid
a biodegradable, thermoplastic, aliphatic polyester derived from lactic acid which in turn can be made by fermentation of various agricultural products such as corn starch