GC50 Epoxy Compatible Polyester Gelcoat

Talk Composites - The Forum for Advanced Composites

Back

GC50 Epoxy Compatible Polyester Gelcoat

Author	Message
Robert72	R Robert72 posted 5 Years Ago HOT Topic Details
R Group: Forum Members Posts: 57, Visits: 151	Not really a resin question, more of a Gelcoat question. Would the above Gelcoat be suitable for taccing my outer layer into my female mould? The mould is a tube, 300mm dia 1500mm long, and I am wondering how to secure the cloth into the roof of the mould without it collapsing. Subsequent layers, peel ply infusion mesh etc. can be secured with spray adhesive I think? Is there a better way?
	Reply Like 3
MarkMK	MarkMK posted 5 Years Ago HOT Post Details
Group: Forum Members Posts: 338, Visits: 2K	It sounds like spraying the GC50 into such a mould might prove tricky in terms of getting a reasonably even coat but, if you can judge the tacky stage perfectly, it might help. Brusihing it on can be a bit hit and miss in terms of fish-eyeing and can affect the visual look of the part if there's unevenness in the coating. It does sound like using a good spray tack to secure the surface layer to the whole tube would work best, though and it should hold things okay, even if inverted. The GC50 can be useful here as it might just help ensure that there's little to no visible trace of the spray on the part surface. I tend to use Cytec's Aerofix 3 and there is very little trace of anything when combined with GC50 and EC's resins, although this is no guarantee that there won't be some reaction with other products. As a component part of the spray is acetone, applying too much could be problematic to the surface quality, although it's quite strong even when misted lightly Even with a thorough de-gassing beforehand, there will likely be some air in the resin that will be evident during infusion (Is this the intended process?). I imagine that, there could be some evidence of air entrapment on the inverted section of the cured part afterwards, as the natural direction of travel for any air still in the resin will be upwards and towards the parts' inverted surface during cure. This might not be an issue for you, however.
	Reply Like 3
Robert72	R Robert72 posted 5 Years Ago HOT Post Details
R Group: Forum Members Posts: 57, Visits: 151	Mark, thanks for your reply, plenty to think about. I was thinking about rollering the GC50 on, not sure how this would affect the release agent. Forgot to mention it is a split mould I am making. In the car bonnet video Matt sprays GC50 to the mould, then sprays the top surface of cloth with acetone to aid adhesion. Using spray adhesive, acetone etc. inside a 1.5m mould is probably a complete faff so I am exploring all options. At the moment I am considering binding the layers with thread to hold them in place. Prior to bag sealing I will cut and extract the threads. Good point about mould orientation and bubble flow. I will infuse vertically with vacuum at the top. Edited 5 Years Ago by Robert72
	Reply Like 3
MarkMK	MarkMK posted 5 Years Ago HOT Post Details
Group: Forum Members Posts: 338, Visits: 2K	Don't go down the sprayed acetone route, as the formula of the GC50 has changed since the bonnet video was made, in order to extend the time that the hardened coating can be laminated onto and still adhere well, so acetone will now cause cosmetic problems If applied by hand over a mould prepared with a chemical release agent, GC50 also tends to fish-eye a bit, so spraying is usually the best option. Not certain how it'd behave when rollered, but it doesn't get overly tacky when nearing it's hardened state. I don't honestly think that it'll work very well in terms of holding onto the surface layer fabric, even if you can accurately determine its optimum state of cure. Your idea sounds quite tricky to pull off and I can't quite picture how things will be held in place inbetween removing the bindings and getting the bag sealed and pulled down, but perhaps I'm not imagining things correctly? However, a spray tack like Aerofix 3 would work really well, I'm sure, even over quite a large surface area. I briefly tried Aerofix 2 some time ago and that seemed more powerful still, but I don't think that it would be quite so good in terms of not showing itself on the surface of the finished part, as it felt a little more 'heavy duty' and less refined. I get through a lot of the Aerofix 3 and, combined with using GC50 sprayed into moulds beforehand, there's never any visible traces. If things don't quite go well, it does allow you to remove the fabric again quite cleanly, as the tackiness of the spray wears off after while. Edited 5 Years Ago by MarkMK
	Reply Like 3
Robert72	R Robert72 posted 5 Years Ago HOT Post Details
R Group: Forum Members Posts: 57, Visits: 151	Mark, thanks for your reply, and apologies for the belated response. The fact that you asked that very pertinent question about the support between removing the bindings and getting the bad sealed and consolidated in fact shows that you understand the process exactly. So I would put in the final layer of bag with sealing tape applied along its length, but not on the ends, inside the mould. And in to that I would apply some form of stuffing to hold it all together. Then extract the bindings. Then apply the end sealing tape. Then consolidate. How does that sound? I suppose in the commercial world they would use some kind of bladder arrangement, but for me its not worth all the time/expense. Even with a bladder I would imagine it would be tricky, so how would a corporate moul;d of this type be done? Is there actually an answer or is my method as good as any other? I know that in the bicycle frame world they essentially fudge it by laminating in two halves and consolidating together, or by bonding etc.
	Reply Like 3