Making a silicone bladder

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Making a silicone bladder

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chriscnf	c chriscnf posted 4 Years Ago HOT Topic Details
c Group: Forum Members Posts: 34, Visits: 2.7K	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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chriscnf	c chriscnf posted 4 Years Ago HOT Post Details
c Group: Forum Members Posts: 34, Visits: 2.7K	+x Hanaldo - 1/30/2021 12:29:46 AM 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! 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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