|
Massimiliano
|
|
|
Group: Forum Members
Posts: 167,
Visits: 1.1K
|
+xThats ok, but it is still only a mechanical bond. Ideally you want a chemical bond for maximum strength, which means getting the bond window timing right. Yes you are totally right. The problem with epoxy tooling gelcoat is a long time before the b-stage and this is still an hobby for me at the moment, so I can't always organize the timing. For this second mold I plan easy lease 6x, wax 6x, pva 3x... it has to release!
|
|
|
|
|
Massimiliano
|
|
|
Group: Forum Members
Posts: 167,
Visits: 1.1K
|
I would like to update this topic about what I think is the cause of the issue: silicone.
I made the plug out of polystyrene foam, and to save time I covered it with a pour of RTV silicone (polycondesation type) so to have a gloss surface without primer coat, gloss coat, sanding & polishing.
I made another mold with the same materials and had identical results: tooling gelcoat delaminated from the reinforcement, and adhered to the part. Chips by chips has been removed again.
I performed a little bit of research and found out that silicone can interfere with resin curing. Some say polyaddition type would be better but is controversial.
Any of you has similar knowledge about silicone and resins?
|
|
|
|
|
Lester Populaire
|
|
|
Group: Forum Members
Posts: 311,
Visits: 13K
|
+xI would like to update this topic about what I think is the cause of the issue: silicone. I made the plug out of polystyrene foam, and to save time I covered it with a pour of RTV silicone (polycondesation type) so to have a gloss surface without primer coat, gloss coat, sanding & polishing. I made another mold with the same materials and had identical results: tooling gelcoat delaminated from the reinforcement, and adhered to the part. Chips by chips has been removed again. I performed a little bit of research and found out that silicone can interfere with resin curing. Some say polyaddition type would be better but is controversial. Any of you has similar knowledge about silicone and resins? silicon has a habit of contaminating everything. at this point i would be worried about the structural integrity of your part. Keep it as far away from any composite (or just adhesive) work as possible. impossible to clean as well. I've heard stories from failing structural bonds after never having any issues with this product for years. turns out they started using a silicon based spray in a coffee machine that was 10m next to the work station, and the overspray was enough to ruin everything.
|
|
|
|
|
oekmont
|
|
|
Group: Forum Members
Posts: 550,
Visits: 27K
|
Silicone or not, if epoxy gelcoat is fully cured, the reinforcement layers will not bond properly. I have made several mould from several different kinds of silicone without ever having a problem. This is not a general problem. At least not for moulds.
|
|
|
|
|
Hanaldo
|
|
|
Group: Forum Members
Posts: 2.5K,
Visits: 28K
|
Yeh 100% agree with Oakmont. I very highly doubt this issue was caused by the use of silicone, its a very typical case of the epoxy gelcoat being outside its overcoat window.
Silicone has a bit of a reputation, which I find somewhat over-hyped. I use a lot of silicone, I've never had any issues. I even use it in my spray booth. In fact I keep two bottles of silicone oil in the same cabinet as my paints and adhesives. I dont have problems with paint fish eyeing or structurally bonded joints failing or moulds delaminating. Thats not to say it couldn't happen, but I always have to wonder when I hear these horror stories how meticulous the prep work was. Were the parts even cleaned properly, or did the apprentice go straight from spraying the coffee machine with silicone to handling the parts about to be bonded? It should not matter if there was silicone overspray nearby, any work you are doing should be properly cleaned and prepped just before you spray/bond/laminate it. I always assume that my parts are contaminated just as a matter of course, and I treat them appropriately. It is far from impossible to clean, your run of the mill Prepsol/wax-and-grease remover will remove silicone residue very efficiently.
|
|
|
|
|
Massimiliano
|
|
|
Group: Forum Members
Posts: 167,
Visits: 1.1K
|
+xYeh 100% agree with Oakmont. I very highly doubt this issue was caused by the use of silicone, its a very typical case of the epoxy gelcoat being outside its overcoat window. Silicone has a bit of a reputation, which I find somewhat over-hyped. I use a lot of silicone, I've never had any issues. I even use it in my spray booth. In fact I keep two bottles of silicone oil in the same cabinet as my paints and adhesives. I dont have problems with paint fish eyeing or structurally bonded joints failing or moulds delaminating. Thats not to say it couldn't happen, but I always have to wonder when I hear these horror stories how meticulous the prep work was. Were the parts even cleaned properly, or did the apprentice go straight from spraying the coffee machine with silicone to handling the parts about to be bonded? It should not matter if there was silicone overspray nearby, any work you are doing should be properly cleaned and prepped just before you spray/bond/laminate it. I always assume that my parts are contaminated just as a matter of course, and I treat them appropriately. It is far from impossible to clean, your run of the mill Prepsol/wax-and-grease remover will remove silicone residue very efficiently. Thank you everyone for contributing to this topic. I have to say that a previous mold, made with the green EC epoxy tooling gelcoat and another brand of silicone has had no issue at all. So I will make two additional tests on small molds: - red epoxy gelcoat with the first silicone - EC green epoxy gelcoat with the second silicone. Maybe the second silicone has some additive in it which interferes with the full curing of the gelcoat, or the red gelcoat is crap. I will on purpose overlook the overcoat window not to introduce another variable. I will update this post as soon as I will have results.
|
|
|
|
|
Lester Populaire
|
|
|
Group: Forum Members
Posts: 311,
Visits: 13K
|
+xYeh 100% agree with Oakmont. I very highly doubt this issue was caused by the use of silicone, its a very typical case of the epoxy gelcoat being outside its overcoat window. Silicone has a bit of a reputation, which I find somewhat over-hyped. I use a lot of silicone, I've never had any issues. I even use it in my spray booth. In fact I keep two bottles of silicone oil in the same cabinet as my paints and adhesives. I dont have problems with paint fish eyeing or structurally bonded joints failing or moulds delaminating. Thats not to say it couldn't happen, but I always have to wonder when I hear these horror stories how meticulous the prep work was. Were the parts even cleaned properly, or did the apprentice go straight from spraying the coffee machine with silicone to handling the parts about to be bonded? It should not matter if there was silicone overspray nearby, any work you are doing should be properly cleaned and prepped just before you spray/bond/laminate it. I always assume that my parts are contaminated just as a matter of course, and I treat them appropriately. It is far from impossible to clean, your run of the mill Prepsol/wax-and-grease remover will remove silicone residue very efficiently. This is actually really useful information for me, thanks. We never had any problems with silicone contamination but i am a bit paranoid whenever someone works with silicone in the workshop. And i was lucky to participate on some seminars where speakers and participants had these kind of horror stories to tell.
|
|
|
|
|
oekmont
|
|
|
Group: Forum Members
Posts: 550,
Visits: 27K
|
I would start with the curing time of the gelcoat, because this is definitely a problem. And it seems like the gelcoat did cure, or were the flakes still tacky? I don't see a reason to believe that this is caused by the silicone.
|
|
|
|
|
Hanaldo
|
|
|
Group: Forum Members
Posts: 2.5K,
Visits: 28K
|
Yeh I feel like testing the silicone is a bit backwards. This is much less likely to be the issue than the overcoat window. Do a test with getting the overcoat window right and then go from there.
|
|
|
|
|
Massimiliano
|
|
|
Group: Forum Members
Posts: 167,
Visits: 1.1K
|
+xYeh I feel like testing the silicone is a bit backwards. This is much less likely to be the issue than the overcoat window. Do a test with getting the overcoat window right and then go from there. Ok, no problem and useful making 4 test samples! I really want to understand
|
|
|
|