Thermoplastics are poor conductors of electricity. To prove this creates a circuit.
To create the circuit we require bulb, copper wires, a battery, a piece of metal, and a plastic pipe. Set up the circuit with the metal switch on the current, the bulb glows. Next set up the circuit with pipe switch on the current the bulb does not glow.
From the experiment we conclude that plastic pipe (thermoplastic) cannot allow the current through pass it hence it is a poor conductor of electricity.