Anyone who has used wax+PVA with prepregs before?

General Composites Discussions Composites Talk
#1

when did you find out it was a stupid idea? :smiley:

I don’t know who came up with the idea, but after some problems with our semi-perm and polyurethane, someone called our vacuum-bag supplyer(the only composites distributor close, everything is rushed at the moment) who told to use wax and PVA.
I think PVA is for bad moulds and dirty fixes, so I try to keep far from it anyway, especially for visual carbon fibre applications.
Long story short: PVA opens up on wax like water does, so no even layer, and wax not properly applied anyway, because it isn’t needed for release…
Prepreg layup: sticky prepreg touching PVA “kind of” layer,is a PVA mess.

So, I know for sure the surface needs a lot of work(in the best case)
But: do I need to worry about the release, or just forget it and trash the lot? I don’t feel to confident about this whole idea…

#2

I really thought you were smarter…

it is time to get a decent can of sealer and release, and yes, these cost money.

#3

1: pva just sucks.
2: your supplier is a supplier, not a composites shop. They don’t know the correct answer all the time
3: pva might melt when curing the prepreg too, which might infuse itself into the prepreg part!

#4

It came out today, in one piece… looked like, well, like something build with pva. The wax did it’s job, and on the places where we destroyed the pva the part looked fine. Too bad the moulds are still intact.

I really thought you were smarter…

If they tell me to xxxx it up, I’ll give them 1 warning. Then I’ll do it, no problem ;). I laminated some aluminium strips in this mould, because it isn’t stable. I told them it would print trough. It did, a lot. So, moulds to a painter, came back better. used the wax and pva, cured at a very low temperature, demoulded it, and it is postcuring now at it’s normal curecycle. Hope that’s working, unsupported…
anyway, I pulled my hands from it, not my problem, warned them…

2: your supplier is a supplier, not a composites shop. They don’t know the correct answer all the time

That’s why I personally like the supplier where Herman works, I know he made mistakes, his customers make mistakes, and I make mistakes. There all shared :wink:

it is time to get a decent can of sealer and release, and yes, these cost money.

I normally use marbocote 227CEE, no sealer. No problems at all. Money is no problem for a release system you can trust, and it’s faster in applying, and doesn’t need a new coat every product.

#5

As I knew and expected, you can’t use a post cure with a ramp of 2 degrees celcius a minute, unsupported…
And I should have replaced the PVA in the can with thinner. They got the idea to try it again. with out me :wink: