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microballoons filler cure times

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Old 10-28-2006, 10:03 PM
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parrthd
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Default microballoons filler cure times

ok just wondering what others have experienced from using microballoons.

i've been modelling for a couple years now and into kit building as well. just started using microballoons and i've found that the filler makes the epoxy cure a lot slower than normal. with just 30 minute epoxy, i've found that i can start working it (sanding, shaping, etc) in 60 minutes or less. however, with the microballoons mixed in (usually as much as the epoxy will hold- to a thick toothpaste consistency) it takes several hours to fully cure to a workable state. i've also noticed that it doesn't heat up like epoxy alone does.

my question is how long does your mixture take to set up? does it heat up? and does the balloons cause the reaction between the resin and hardener to take longer?
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Old 10-29-2006, 02:12 AM
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Default RE: microballoons filler cure times

In general, the larger the amount of epoxy you have, the quicker it will set. If you have an ounce in a 1 oz container, it will set up faster than if you take that same 1 oz and spread it thin. I'm not a chemist, but suspect that the heat generated accelerates the cure, and when spread thin or in smaller amounts, it retains less heat. If you add microballoons it's like spreading the epoxy out, hence the slower curing. As for being able to tell how much longer a given batch will take to cure when adding a given amount of microballoons, that's beyond me.

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Old 10-29-2006, 03:36 AM
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Default RE: microballoons filler cure times

Not to dispute your experience, but a different angle on the question: I have on occasion wanted to squeeze out a fillet bead of epoxy/microballoon paste, by mixing it up in thick consistency, then slopping it into the corner of a plastic bag, from which I have cut off a bit of the corner so I can squeeze the epoxy out like a cake decorator. The trick works, but you have to be fast, because after just a short couple minutes the mass in the bag reacts and goes hard like bam!, and the heat of the reaction will burn your fingers. And this is with West epoxy and their slow-cure hardener.
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Old 10-29-2006, 08:42 AM
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Default RE: microballoons filler cure times

I've found that epoxy seems to cure faster with microballoons or milled fiberglass mixed in. I routinely use milled fiberglass to both thicken and strengthen the epoxy, and have to work fast because of the shorter working time. I use "bubble pack" plastic trays I get from work to mix my epoxy in, and like majortom says, the epoxy gets hot enough to actually melt the plastic if allowed to puddle in the container. It may affect the set time dependent on the amount of microballoons or milled 'glass in the epoxy. I don't use balloons very much, but my ratio of milled 'glass is about 1:3 with epoxy. When using 5 min epoxy, I only get about 2 min. working time before it starts heating and sets; with 30 min. epoxy I get about 15-20 minutes working time. I usually use either Z-Poxy or DHP epoxy (sold at Lowe's Builder Supply).
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Old 10-29-2006, 09:45 AM
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Default RE: microballoons filler cure times

Not to dispute your experience
that's not a problem, this isn't a right or wrong thread. i just wanted to hear what everone else has experienced. i will agree with you on initial setting of the mixture, it does start to get hard quicker than the epoxy alone. as far as the final hardness and completely "dry" i've had to wait as long as overnight to finally get rid of that "tacky" feeling.

has anyone tried microballoons and say........fiberglass resin or finishing resin??? that SHOULD give you a lot longer working time but would also increase the cure time dramatically.
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Old 10-29-2006, 10:51 AM
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Default RE: microballoons filler cure times

One thing I have learned to do, ALWAYS thouroughly mix the epoxy two parts together befor adding the filler material whether it be balloons, fiberglass or ?. And yes, I find the mix cures faster than just the epoxy alone. What many do not realize is that all epoxies take about 24 hours to fully cure--even the 5 minute type-- depending on temperature. Higher temperatures accellerate the cure rate.
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Old 10-29-2006, 10:56 AM
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Default RE: microballoons filler cure times

Higher temperatures accellerate the cure rate.
another trick i've learned is to take the mixed epoxy and stick it in the microwave for 3 or 4 seconds, this will allow it to be spread as if it's been thinned with alcohol but the added heat speeds the cure time as well so you HAVE to make sure everythings ready.
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Old 10-29-2006, 12:29 PM
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Default RE: microballoons filler cure times

I recently started using "finishing" resin, instead of 30 min, for my microballon/epoxy mix. Much easier to sand, and sets up harder. Does not gum up when sanding. You can finish sand a a small fillet, such as on a tail surface, in about an hour or less.
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Old 10-29-2006, 08:37 PM
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Default RE: microballoons filler cure times

in about an hour or less.
an hour??? that's amazing considering most resins i've used is 20-24 hour cure time. i've got to try that the next time i use the microballoons
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Old 10-30-2006, 08:51 AM
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Default RE: microballoons filler cure times

Terry,
I use finish reson too. Been doing it for several years now. I find that it sands like hard balsa, much easier than epoxy. Makes small fillets pretty quick and is pretty durable. I only use glass fibers in epoxy when its concealed.
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Old 10-30-2006, 09:41 AM
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Default RE: microballoons filler cure times

I use polyester resin with micro balloons and also with fiberglass cloth on the fuselage, etc. It is easer to use because you can control the set up time and seems to bond cloth to balsa better than epoxy. About the only place I use epoxy for finishing is mounting plastic canopies with fiberglass cloth and micro balloons.
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Old 10-30-2006, 11:31 AM
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Default RE: microballoons filler cure times

I ofter have to use my hot air gun to warm epoxy that has been left to set over night. It will still have a tacky feel the next morning but the warm (not hot) air will make the stuff set pretty quickly and then you can sand quicker. Mixing the expoxy more will also cause it to go off quicker.
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Old 10-30-2006, 02:18 PM
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Default RE: microballoons filler cure times

buzzingb

i noticed that you're from bruce....where do you fly at?

we fly at a private field between nettleton and aberdeen. maybe we can get together to fly a bit?
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