What substance can I use to suspend nichrome wire in custom cartidge heater?

Thread Starter

strantor

Joined Oct 3, 2010
6,812
I'm designing a widget and it needs a cartridge heater of unique dimensions and construction. I know you can special order cartridge heaters to your spec but I don't know what my spec is yet, and it might go through several iterations before I arrive at something I would feel comfortable placing an order and waiting for. Until then I would just like to roll my own cartridge heaters. I can't find much information about this. The thing i need mostly to know, is what kind of substance should be used to suspend the heating in wire in, inside the cartridge. If you take the guts out of a commercially made one, they will be suspended in some white chalky stuff, but I don't know what it is.

I think the substance needs these attributes:
-Good thermal conductivity
-Bad electrical conductivity
-little or no shrinkage or expansion at high temperatures
-Does not ignite/burn, melt, or release toxic fumes below 1000C/1800F
-preferably a paste that will harden on its own or upon first heating.
-can withstand many many heat cycles before cracking or otherwise failing.


I have made a couple already using furnace cement (this stuff) and it worked but I think this is a thermal insulator rather than a thermal conductor, so it probably could work a whole lot better if I used something more appropriate. Something like Boron Nitride I think is probably ideal and can be had in a paste, but when I tried to use it, after the paste dried it was much to fragile, almost like the excrement of the "pooping dog" firework or the "magic black snake" firework.
 
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Thread Starter

strantor

Joined Oct 3, 2010
6,812
It could also be some kind of wrap/tape, cloth, or string. That might even be better, as then I could fill the gaps with boron nitride. The idea is just to keep the nichrome wire from contacting the metallic interior of the cartridge.
 
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