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chriscnf
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Group: Forum Members
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Hi guys I've decided that I need to move from Qualatex balloons to a silicone bladder.
I've got Smooth On rebound coming just because there isn't much available in NZ at the moment.
Its a three part mold and I've built fiber glass shells to go in the mold parts to correctly size the bladder.
I will mess around with some trials but I'm was a little bit confused about the right time to do second coats and joins last time I did this.
I was using dragon skin then and it seemed to go from runny to tack free without a good tack period to second coats and a complex join.
One thing I did learn last time is that acetic cure tube silicone sticks like s*** to a blanket with smooth on silicone for fixing seam flaws.
The idea is to make a thin patch with the smooth on silicone and then glue it on with the cheap tube silicone.
Any pointers would be massively appreciated...Chris
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Hanaldo
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Silicone will bond pretty well to itself if it is fresh. The fresher it is, the better it will bond. So I generally do the next layer as soon as the previous layer is firm enough to not disturb it when you apply the next layer.
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chriscnf
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Group: Forum Members
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+xSilicone will bond pretty well to itself if it is fresh. The fresher it is, the better it will bond. So I generally do the next layer as soon as the previous layer is firm enough to not disturb it when you apply the next layer. In that case this should a breeze...cheers Hanaldo...
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chriscnf
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Group: Forum Members
Posts: 34,
Visits: 2.7K
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+x+xSilicone will bond pretty well to itself if it is fresh. The fresher it is, the better it will bond. So I generally do the next layer as soon as the previous layer is firm enough to not disturb it when you apply the next layer. In that case this should a breeze...cheers Hanaldo... Not quite a breeze but got a good result. I'm thinking about a release agent to help with getting the bladder out of the close mold and to extend its life. The areas inside the product that I need to adhere epoxy to are protected by peel ply so transfer of the release agent doesn't bother me too much. Cheers...Chris
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Hanaldo
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Group: Forum Members
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I always found pulling a vacuum on the air fitting made pretty short work of removing the bladder afterwards.
Pictures?
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chriscnf
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Group: Forum Members
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+xI always found pulling a vacuum on the air fitting made pretty short work of removing the bladder afterwards. Pictures? I will get some shots up. The bladder is coming out easily but I want to preserve its life. I pour epoxy into silicone molds and just had my first failure as the silicone changed color and lost some of its self release. Spay on release is just another cost in the process but I may have to go that way. I massively appreciate your input to this forum...Chris
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Hanaldo
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Group: Forum Members
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Yeh its unfortunate that epoxy dries silicone out so severely. Ive tried Mann Ease Release 200 as well as Stoner E236, E455, A324, and E497. I wouldn't say I noticed any very real extension of the silicones working life with any of them, perhaps a few extra cycles with E497 and A324 but its difficult to say if this was due to the release agent or because I was using a more forgiving process. Really none of them prevent the interaction between the epoxy and the silicone, so the silicone still dries out. PVA is really what you would need, which of course won't work.
The good news is none of these transferred to the part, so I do still tend to treat all my silicone moulds just in case it does help at all. If you find something that definitely works to extent the life of the silicone then please let us know, I'd love to get indefinite usage from my rubber tools!
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chriscnf
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Group: Forum Members
Posts: 34,
Visits: 2.7K
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+xYeh its unfortunate that epoxy dries silicone out so severely. Ive tried Mann Ease Release 200 as well as Stoner E236, E455, A324, and E497. I wouldn't say I noticed any very real extension of the silicones working life with any of them, perhaps a few extra cycles with E497 and A324 but its difficult to say if this was due to the release agent or because I was using a more forgiving process. Really none of them prevent the interaction between the epoxy and the silicone, so the silicone still dries out. PVA is really what you would need, which of course won't work. The good news is none of these transferred to the part, so I do still tend to treat all my silicone moulds just in case it does help at all. If you find something that definitely works to extent the life of the silicone then please let us know, I'd love to get indefinite usage from my rubber tools! I built my bladder undersized enough that I can use peel ply and thin breather cloth which will reduce the the contact with epoxy. Its a work in progress but I fold back a tail of peel ply from the farthest point and it will pull out of the finished product giving me a lighter piece and a good surface to adhere to. I see that in the bike frame video EC put up that the vacuum bag is separated from the prepreg with a plastic film of some sort to enable the bag to move. I have done that and it pulls out of the work easily but doesn't have the advantage of removing excess epoxy.
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Hanaldo
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Are you using pre-preg or wet-lay? The non-perforated release film you see in that bike video is really for pre-preg only, where the resin content is already controlled. If you're doing wet-lay, you wouldn't use that film because as you say, you can't remove excess resin.
You could use a perforated release film though? Would have the same benefits that they used it for in the bike vid, but would allow some resin bleed.
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chriscnf
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Group: Forum Members
Posts: 34,
Visits: 2.7K
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+xAre you using pre-preg or wet-lay? The non-perforated release film you see in that bike video is really for pre-preg only, where the resin content is already controlled. If you're doing wet-lay, you wouldn't use that film because as you say, you can't remove excess resin. You could use a perforated release film though? Would have the same benefits that they used it for in the bike vid, but would allow some resin bleed. Wet layup and I'm using the red stripe peel ply with a layer of breather cloth tacked to that. Resin bleeds through and absorbs into the breather cloth. So I'm reducing weight and contact with the bladder to some extent. The original reason was to allow the balloons to move freely when. Have to be careful with setup though or the ply is hard to remove. If release agent doesn't protect the silicone I might give a brush on latex a try, latex balloons come out reasonably well without release agent. I do have some weather balloons on the way from China to try out as well.
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