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fiberglass for resin forms VS fiberglass for thermal insulation? Answered

I see woven or braided fiberglass (in tube, rope, sheet, band) for use as
1)  a seal where the seal is going to be exposed to high temperature (eg: stove door gasket);
2)  for use as a thermal guard (eg: tubing around electrical wire);
3)  and then used for it's' strength in resin impregnated sheet (egs: roof sheeting; mould making; boat building).
My question is whether there's any difference between the fiberglass fabrics available for thermal and resinous uses? Are they interchangable? Fiberglass is fiberglass no?


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5 years ago

Fiberglas is fibreglass the same way a tyre is a tyre ;)
The fibers will tolerate great heat and if thick and dense enough protect against heat quite good.

But fiberglass as we know it is the stuff with resin and rock hard.

Your problem is the resin.

Not only is the thermal insulation poor but the resin is usually highly flamable - something you don't want to protect from heat.

But I have seen people using fiberglass fabic sheets and clay (or even concrete) to make custom heat shield for their BBQ's.

Basically the same like resin but with clay/concrete as the binder.


Answer 5 years ago

That's promising. Because what i'm thinking of is using the fabric (no resin) as is for a thermal boundary. Fiberglass for resin applications is SO much cheaper. And i think it's just a matter of companies charging more because of a percieved value in a 'specialist' application.
I know that not all fiberglass can work with all resins. Supposedly because it has a coating that helps the resin bind? Wonder if that coating could be noxious or worse when excessively heated.... ?


Answer 5 years ago

For heat shielding you want at least the first layer (facing the heat) to be of the really fine kind.

What is used as the finnishing layer when you make fiberglass casts.

I used my sewing machine once to make a multi layer patch as a heat shield.

Outer layers really fine, between them the coarser sheets.

Was only to keep it all together for fixing it in frame.

Most of the cheap fireglass cloth sheets (or rolls) you see are not coated with anything at all.

The coated stuff is used for repair jobs with building filler and similar binders.

But if you just want it forheat protection you might be better off using insulation rock wool.

The stuff is extreme heat resistant, quite cheap and easy to compress.

Does not look as pretty as white fibreglass though.

Best thing is that you already have quite fine and smooth material to work with.