Originally Posted by cyccommute

There is a difference between “resin” and ”plastic”. While both are polymeric organic compounds, their properties are generally different. Thermoplastics...which is what most people refer to as “plastic”...are polymers that can be reheated and reformed endlessly. Thermosetting plastics...resins...are polymers that are heated to form them but once formed they can’t be remelted and reformed. Heating them usually causes them to become more densely crosslinked. They also tend to decompose when heated.

Thermoplastics are things like polyethylene, polypropylene, PET, PTFE, etc. Thermosets are things like phenol/formaldehyde resins (Bakelite), many elastomers like rubber, epoxy resins.