We are trying to repair an Ultimaker Original+. One problem is a missing resistor isolation. The Ultimaker Original+ prints with up to 260 Degree Celcius.
Which kind of isolation products are suitable to resist the heat and are fitting on the thin wires of the thermistor?
The most common choice for insulating thermistors is glass fiber sleeving. It tolerates very high temperatures, and is commonly rated for up to 600 °C.
Teflon is also used but has a rather low upper limit on its working temperature; it shouldn't be used at temperatures exceeding 260 °C - which rules it out for your purpose.
I'm not sure if it fits the use you're describing, but Kapton (polyimide) tape is stable to about 400 degrees C. It can also be used as a build surface, so generally useful to have some.
Kapton tape is used all the time for electronic work, both to secure fine wires (for example patch wires on a PCB) and for insulation. It's not so great for thermal insulation since it is thin, but I have my hot-end wrapped in it, and that has saved some burnt fingers.
I used Kapton tape to insulate mine.
There are many materials you can use one that came to my mind is this High Temperature & Pressure Sealant and also the best way to apply it so it can be removed easy is this . take a kitchen food very thing nylon cover you know the very thin elastic one or cover the parts with some type of release agent (dont use something that inhibit silicone like sulfur or sulfur containing staff) and apply it over it then when is solid cut it and release it it would be like a glove i hope ;)There are silicone that are really high temp 1000 f to 2000 f good luck :)
