Question

Polyethylene or pvc which has lowest dielectric losses

Answer 1

First you should know what is Dielectric losses :

Dielectric loss, loss of energy that goes into heating a dielectric material in a varying electric field. ... …production of heat known as dielectric loss,

Then how does it happen or how :In conduction loss, a flow of charge through the material causes energy dissipation. Dielectric loss is the dissipation of energy through the movement of charges in an alternating electromagnetic field as polarisation switches direction. ... Dielectric loss tends to be higher in materials with higher dielectric constants.

And PVC has the lowest dielectric losses..