Ideas on the best pinhole/void filler?

General Composites Discussions Composites Talk
#1

I want to expand on this (http://www.compositescentral.com/showthread.php?t=7152) thread since it’s getting kind of bloated

Some of my infusion parts come out with random pinholes or mini voids just between the carbon weave. I cannot get rid of these for whatever reason. I suspect they’re coming from not having a full vacuum (analog gauge is only pulling down to 28.5") and from air mixing with left over atm air in the resin feed line hose after I unclamp it to start infusion (a problem that’s proven fairly hard to solve…)

Anyways, I’m looking into filling these things and then sanding flat instead of discarding the parts. Here are some of the methods I’ve gathered so far:

super glue
black shoe polish
a black wood filler

I’ve tried super glue and I’m not thrilled with the results. I haven’t tried black shoe polish; can the people who’ve used that method give me more insight? The black wood filler seems fairly promising.

I decided to buy a can of Adtech p-17 PE filler in black (http://www.adtechplastics.com/pc-15-643-p-17-high-heat-resistant-filler.aspx) . I’m hoping that I can mix this and pack it into a syringe, and then inject it into the voids to cover them up. The only downside to this stuff is that it has an incredibly short working life (4-6 minutes; can I increase working life by using less of the promoter?). Adtech says it sands well so hopefully I can just knock off all of the excess.

#2

If you fill only pinholes with resin it will be hard to sand such small areas and most probably you will sand through carbon on neighbor surface. Better idea is to sand softly whole part then recoat with resin

#3

Flow coating is out of the question. the reason I didn’t like the superglue fill method is because died cyanos are indeed harder than my epoxy system, so I was burning through neighboring carbon pieces. I’m hoping the PE filler is a bit easier to sand off, I haven’t been able to try it yet though. Will probably pick up some injecting syringes from a pharmacy tomorrow.

#4

P17 is probably too think for a syringe. Its good stuff though.

#5

My personal go is Proset 175/273 black and duratec 1904-045 clear. Not a cheap solution but works good. I do a lot of one of parts for race boats where the economics of tooling female often don’t work and you end up cleaning up vacuum bagged wet layups. Also nice because the Proset can be used for high quality secondary bonding also (it’s intended purpose).

#6

Hmmmm as luck would have it I’m about to pick up another 5 gallon kit directly from Proset tomorrow. Hopefully they’ll be cool with throwing in a sample of the 175. I didn’t get a chance to try the Adtech p17, I’ll get back to you guys with my results when I do get around to it.

Hojo, I was afraid of that. I’ll still give it a shot and see what happens with a wide tip needle. Is there any way to thin that stuff? Like, styrene???

#7

P-17 is vinylester based and the fillers are pretty fine so it fills pinholes pretty well. Since it’s VE based, you can probably thin it with styrene but I don’t think you’ll be able to shoot it out of a syringe. You can slow it down with low cat level but, as stated, it is pretty fast regardless. If you do end up using it, sand it as soon as you can after it cures. It gets harder the longer it sits.