I have this electrical heater that runs on AC power (which is part of a bigger robotic device). The leads are exposed, and so I need to cover them for safety reasons. I've measured the heater at 492F / 255C.
Plastics will all melt, and metals are conductive. I haven't looked into ceramics yet.
There's always the old cermic beads found in eg. old toasters and room heaters, etc. but This
should do and won't shatter or chip like the ceramics might.
I have a reel of another type named Siligaine with a SiO2
braidi and while I'm not sure about the max. thermal limits of the stuff I have, it should be at least as good as the Thermasleeve - Eg. Siligaine 33SI boasts the following data:
● Continuous working temperatures: + 1050 °C, Peaks at + 1200 °C.
● Highly flexible.
● Excellent resistance to radiation.
● Frays slightly when cut.
● Low heat expansion coefficient.
● Excellent thermal insulation properties.
● Low density.
● Very high chemical resistance, especially to acids.
I have no idea of the price, but I have a feeling that you're not picking up the bill anyway