Dear Student
If the plastic is a thermosetting plastic then it is not able to melted.
However, a thermoplastic plastic can be melted and remoulded as much as you want.
So if plastic is thermoplastic then it can be easily melted and melted or not melted depends on melting point and chemical composition of plastic not on how it conduct heat.
Plastics are used in utensils in making handles as it is bad conductor of heat.
Regards