Sciencemadness Discussion Board

Heatproof sheeting??

ktw_100 - 28-8-2006 at 10:01

I am building some electrical heating elements, and need something to insulate the element from the underlying conductive metal. The heating elements get pretty hot, ie: red, so it needs to be pretty good stuff. It also has to be able to bend.

I use refractory cement for covering the elements, but would prefer not to use this as the main insulator, as it can crack.

Toasters, for example, use mica sheets under/around the elements. Try finding a sheet of mica!

Is there anyone who has done something similar, and knows about a product to fit the bill? (Asbestos seems not to be very popular anymore either).

Thanks
Keith

Magpie - 28-8-2006 at 10:09

How about woven fiberglass cloth. Don't ask me where to get it. ;)

Heatproof sheeting?

ktw_100 - 28-8-2006 at 10:33

Quote:
Originally posted by Magpie
How about woven fiberglass cloth. Don't ask me where to get it. ;)




Fiberglass cloth ..... can be purchased at auto body supply places. I wonder if it can stand the heat? I know that with fiberglass insulation, it WILL burn, even though it is made of glass, due to the small fiber of it. Dunno if fiberglass cloth is the same or not. I will get some and give it a try.

Thanks!

Keith

neutrino - 28-8-2006 at 10:43

Any place that sells fiberglass supplies will sell glass cloth.

One place to look is boating suppliers. Many boats are made of fiberglass composite, so boating places sell repair kits.

For more information, UTFSE.

ktw_100 - 28-8-2006 at 10:58

Quote:
Originally posted by neutrino
Any place that sells fiberglass supplies will sell glass cloth.

One place to look is boating suppliers. Many boats are made of fiberglass composite, so boating places sell repair kits.

For more information, UTFSE.



Thanks - very good idea ....

Magpie - 28-8-2006 at 13:10

Home Depot has "Fiberglass Cloth", 9 ft2 for $6.

While at Home Depot I checked the solvent shelves just for the heck of it. I noticed that there was no acetone, even though there was two large bins alloted to it. :mad:

Twospoons - 28-8-2006 at 13:47

If fibreglass cloth wont do it you could try the ceramic fibre blanket used in kilns.

Or if you want a sheet of mica - buy a cheap toaster !:D

[Edited on 28-8-2006 by Twospoons]

not_important - 28-8-2006 at 14:37

Look into castable ceramic insulation, from pottery supply places. You make a mold with ridges where you want grooves to hold the heating wires, mix and pour the ceramic, let it set, clean it up, place the wires, put into metal shell, dry using very low current to start with, slowly raising it over many hours.

Woven glass fiber is better where you need the flexabilty, or for lining the heater to give a bit softer surface for the flask. Ordinary glass wool/mat softens at a fairly low temperature, borosilicate is better if you are going to really pour on the heat.

As mention above, ceramic blankets for kiln insulation also work; however some of these are designed to installed and not touched again, they harden after first use becoming somewhat brittle, those usually have organic coatigs that burn off in the first firing so good ventilation is needed until burned clean.

halogen - 28-8-2006 at 14:38

Quote:

Fiberglass cloth ..... can be purchased at auto body supply places. I wonder if it can stand the heat? I know that with fiberglass insulation, it WILL burn, even though it is made of glass, due to the small fiber of it. Dunno if fiberglass cloth is the same or not. I will get some and give it a try.


:oWhat? Glass doesnt really burn unless in a fluorine rich environment. Melt, sure, but burn?

franklyn - 28-8-2006 at 16:10

Is this thing going to fly somewhere?
Unless this is a high tech application save yourself the expense
and use plain old bathroom tile or a piece of sheetrock. You don't
even need to buy it , just visit a demolition in progress and help
yourself.

ordenblitz - 28-8-2006 at 19:31

I would like to add a useful little method for making small high temperature blankets that come in handy for general laboratory use. These are made out of woven fiberglass cloth such as the type commonly sold in the auto parts stores for fiberglass repairs, and high temperature RTV silicone sealant also sold in the same stores.

First, I get a large sheet of polyethylene plastic such as a heavy-duty garbage bag to use as a non-stick surface and lay it flat and smooth on a table or work bench. Next unfold and layout a large piece of the woven glass cloth on the PE surface. You might find that taping the bag down to your bench will help keep your surface from sliding about while working. Your nonstick surface should be slightly larger than twice the size of your glass cloth sheet to facilitate turning the sheet over and putting it down on a clean surface. You will be making multiple blankets from this large piece of glass cloth.

The next step is to lay beads of high temp silicone on the large cloth in the general dimensions of your intended blankets and work it into the cloth with gloved fingers. I usually lay a good thick bead and carefully flatten it out while massaging it into the fibers while at the same time not terribly stretching and deforming the fragile weave. Each bead is the edge of two adjoining sheets. That is to say when dry, you will cut right down the middle of the smeared silicone beads to form two edges. Keep this in mind when planning your layout. One could also mask the layout for more ascetically pleasing finished product but I find this extra work unnecessary.

When the layout and first addition of the silicone is finished, carefully turn the glass cloth over and place on the clean portion of your PE sheet. You will notice that the silicone has not penetrated your glass cloth completely. Add more RTV and work in where necessary along your lines. Leave to cure for a few days then finish your blankets by cutting down the center of the beads for a nice clean non fraying edge.

These useful glass blankets are very convenient for protecting surfaces, insulating glassware, handling hot items and many other invaluable tasks. I use them constantly and they are holding up very well.

ktw_100 - 29-8-2006 at 06:49

Some very good ideas - much appreciated.

As for fiberglass insulation burning, I suppose it is true that it doesn't - it melts. However, I've tried 'burning' it, and there is a smoldering red hot spot, which is enough to catch other things around it on fire.

I will give the fiberglass cloth a try. I really like the idea of a heating blanket with the silicone. And the tile thing and castable ceramic is a good idea too, and cheap.

Thanks again.

Keith

IrC - 29-8-2006 at 09:43

I would build them up with a thick coat of ITC-100 or ITC-200.

U2U me if you need the name and number of a man who sells this stuff.

ktw_100 - 29-8-2006 at 11:25

Quote:
Originally posted by IrC
I would build them up with a thick coat of ITC-100 or ITC-200.

U2U me if you need the name and number of a man who sells this stuff.


Thanks, IrC. Will do if I can't track it down here.

Keith

YT2095 - 30-8-2006 at 02:04

there`s also Fire cement/clay, you can get it from the same places that sell open fireplaces, although once it`s in place you`re commited and cannot remove it later if the element breaks.
or there`s "Pyro", it`s a magnox powder used in certain high current applications, it looks like copper pipe, filled with a white powder and a central copper wire in the middle of this (like Coax).
this powder won`t melt either.
you may also be able to get Mica sheeting from the fireplace shop also, it`s used in windows for certain burners and stoves.

IrC - 31-8-2006 at 21:39

"Try finding a sheet of mica!"

You said it yourself, toasters. Find and gut a few old dead toasters, I did so and gained quite a few sheets of the stuff.