In RC applications the wire is made of copper, the insulation is often PVC or Silicone.
Silicon (a type of rubber not a semiconductor ) is more flexible than PVC, it has very good thermal and electrical properties.
I have found PVC insulation crack after some use in various weather conditions and vibration exposure.
There are claims that silicone insulated wires are lighter but I’m not sure at the moment, looking at wires used in lipo batteries it seems that they are thinner than you would expect looking at an AWG table.
Silicone insulated wires are easier to solder.
