In that case, I believe that our most common type of wire insulation (THHN) is an insulating PVC layer covered by a nylon protective sheath.
That said, from my work around plastics, I must add that PVC is by far the most added to, treated, blended plastic around. Saying something is made of 'pvc' is a lot like saying it has steel in it - there's an almost infinite variety of products, ranging from the junk to the jewel.
