Microballoons

[KevinL]

Getting ready to bond in the skylight angle to the upper rear carry through tube on the fuselage. The book says to mix the adhesive with microballoons. I've used microballon powder with resin for composite but not sure why it would be used with the adhesive. Also do not know what ratio to use. Could someone educate me please?

[efwd]

I understand the microballoons to be for nothing more than keeping the two dissimilar metals from contacting one another. You only need very little. Just enough that, in your minds eye, there will be a layer of balloons across the surface so that contact of the two parts is not achievable.

[jrevens]

I agree with Eddie. They're also used as filler to make a light-weight, easy to sand mixture with epoxy or other resins. The fact is that they weaken the strength of a bonded joint. FWIW, I can see no reason to use them for bonding that piece to the fuselage tube because the tube is powder-coated and there is no direct contact between the dissimilar metals.

[n85ae]

Probably the microballons are simply to act as a thickener so the adhesive doesn't run. It's
not a very highly stressed bond I wouldn't think.

Jeff

[efwd]

If you are trying to thicken, it's Flox that Kitfox will call for. Having said that, people use balloons to thicken and make workable as John stated.

[Maverick]

My recollection from building a fiberglass plane is that the micro-balloons are good for thickening the slurry for filling voids and making bonds that were not stressed while cotton flox was called for when it was a bond that needed to be strong. I used flox on that bond only because the slurry with micro-balloons tended to flow and run away from the two surfaces. With flox it was more pasty and didn't run away from the two surfaces but either would work on that joint. And, just in case there is a difference between the glue types, I was using 3-M rather than Hysol.

[KevinL]

Thanks much for the replies. Pretty much confirms what I remember from working with composite. The microballoons would thicken the resin which was maple syrup consistency prior to adding. I'm using the Hysol 2-part adhesive which should be thick enough for this application I think.

[n85ae]

Thickening with microballoons creates a better appearance than Flox as well, and that being a
pretty visible location may be why they called for microballoons instead of flox.

Jeff

[efwd]

Maverick, what is the 3M product you mention you used vs. Hysol?

[taff]

Reading this thread, my mind wanders (I hate it when it does that)

Microballoons -V- flox. (added to an adhesive material).

I am thinking
Microballoons: would be better as a surface filler (causing bulk and thickening)
Flox: would be better as a structural filler (causing bulk and thickening) but also has the fiber integrity to better hold together.

I have used both, the balloons where I needed only the surface filling quality that would later be shaped and sanded down.
I have not experimented and no longer have these products to test.