I think that the coating is called kaptan. It's urea based, has the advantage that it is 33%lighter than conventional plastic insulation, but it has horrendous properties. You must strictly adhere to minimum radius turns in the harness. It will crack otherwise, and, nice one this, if you get an arc the insulation turns into carbon which arcs some more and burns, and arcs some more.... I believe that the RAF lost a couple of Harriers through this a bit back, including one that had been rewired. Nice stuff isn't it.