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fjm9898
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I am not a happy camper today. I spent a bunch of money to have GC50 sent to the US because its the only thing that will work according to Easy Composites. I followed every direction perfectly and soon as i cut the part, it start to chip up immediately. I got the mixing portions right, i bought a spray gun. Laid it on a bit thinker, maybe 0.5mil or 0.6 mill, but should not of been a problem since some people brush it on heavier. i let it stand for about 10 hours, well after the 2-3 cure time and well within the 24hour max out period. i did resin in fusion. i let the resin and the gc50 cure for 3 days. first cut, darn near instantly started to chip up and de-laminate. i used a cutoff wheel and actually moved downt eh part slow and moved fast to see if it was heat or speed, still happened no matter what. i am at a loss guys. this product was supposed to be aon a show car tomorrow and i completely blew it because of this issue. i really dont understand. here are a few pictures.  
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Hanaldo
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What resin did you infuse with?
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fjm9898
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Resin Research 2050
Same stuff i have been using for the last year.
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Hanaldo
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Should be fine. Is there any delamination anywhere on the part other than a cut edge? In the images you posted, is that the line that you cut with the cut-off wheel or did you use a file/sanding block to fettle up to that edge?
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fjm9898
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It happened in both cases.
the picture of the bigger pull up is when i was sanding an edge. the smaller ones is when i was cutting it.
Drilled some holes and same thing, big time delamination.
It didnt bond nearly at all, i can basically peal it off.
not only i am unhappy about not making my deadline, but also i made a 8ft x 4ft sheet, so that is a huge cost in material i have to throw away.
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Hanaldo
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Definitely a strange one, hopefully one of the EC staff will be along soon and has some insight. I had a similar issue once with an epoxy infused carbon/fibreglass part where the fibreglass delaminated from the carbon like it was peel ply. Never really found a definitive explanation, it was a part I had made before and a part I have made since and never had the problem reoccur. Feel your pain about binning so much product, it's really the downside of using an in-mould coating vs post-mould clear coating. I've binned plenty of products that would have been fine if they didn't have a coating. Not that GC50 isn't a good product, but it's far from the only product that would work. Being in the US, you could get Duratec Sunshield very easily I'm sure. Scott Bader Crystic Glosscoat is another one, though not sure on availability in the States. Just for future knowledge.
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Warren (Staff)
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Sorry to hear you are having problems with GC50. In our experience, we have yet to have any reports of compatibility issues of GC50 with other brands of epoxy resin, although that is a remote possibility.
This would lead me initially to think that the issues you have had are process based. There could be a number of factors at play here that could have negatively effected your sheet. I can't tell from your forum details when you ordered the resin and how long you have had it, so it is possible that the resin is quite old. As resins age, the activators in it degrade, which means that the cure can take longer than expected.
Also as you are in the US, you would not be using our MEKP, so again there could be variance in the reactivity of the MEKP effecting the cure time. This combined with perhaps a lowish temperature at some stage in the cure cycle could mean the GC50 simply wasn't ready to be overlaid with epoxy.
The epoxy bond to the polyester is purely a mechanical bond, so anything that degrades the surface of the gelcoat would likely have a negative effect on the bond strength. A part cured or tacky gelcoat would almost certainly cause an issue. Unlike typical polyester gelcoats, the gelcoat should be firm and tack free before it is ready for epoxy application.
You may find with your combination of MEKP, resin age, working temperature etc, that you need to use more catalyst and/or allow longer for the gelcoat to cure than normally might be expected.
Other factors can include moisture contamination due to working in moist conditions, combined potentially with heat cycling during the cure (eg changing temperature of the curing environment) leading to excess moisture absorption on the surface, again resulting in a poor bond. Other forms of surface contamination may all contribute to problems achieving a good bond.
If you can give me some more detailed information on your process then I will do my best to advise further to help you overcome the problem.
Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant
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fjm9898
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Warren The GC50 was purchased last week from your site and arrived on tuesday. So if its old, then you sold me bad batch. I used Bondo brand MEKP. I dont see how any MEKP would be any different really from the next, but i am no expert. The gelcoat was not tacky in the least bit. i even sanded the entire surface to get rid of any high spots to help ensure a perfect weave. the sandpaper and sanding block never ones grabbed the gelcoat and it was a perfect very fine dry powder. So the gel coat not being cured was not an issue. After sanding i didnt use any solvents that may have contaminated the surface, i used a dry cotton rag to clean the sanding dust. My shop was set at 72 degrees minimum during the entire process. When doing infusion i run the shop at 80 degrees to help the resin flow. Curious. If you say that GC50 and Epoxy is working on a mechanical bond, there why is there a max time limit of 24 hours? A mechanical bond wouldnt care if its been 10, 24, 48, 72 hours.
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Hanaldo
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MEKP varies MASSIVELY. I've actually got 5 different brands in stock because each gives me different advantages, eg. longer or shorter pot lives, higher final cures, lower porosity, etc. As for mechanical bond vs chemical bond, youre talking about bonds at a molecular level. Yes, abrading a surface to give a key is referred to as mechanical bonding too, but mechanical bonding can also take place in the molecules of 2 substrates. A chemical bond means that a reaction takes place where 2 or molecules link together to become one molecule. In mechanical bonding, 2 or more molecules stay as separate molecules from a chemistry perspective, but become 'tangled' together and effectively become one. Think of it like a chain structure. The actual metal links are the molecules, and a 'covalent' chemical bond would be what makes up each individual link. A mechanical bond is the intersection between two of the links. As far as the bond between the epoxy and the GC50 goes, I'm not overly familiar with the exact chemistry of the GC50, but I would say that the 'open time' is the length of time the the molecules remain unlinked, and so the epoxy molecules can form a mechanical bond. After that time has passed, (and likely it is due to the evaporation of the styrene molecules) the epoxy molecules can't become entangled with the polyester molecules any more.
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Matt (Staff)
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FJM9898, Warren has been discussing this issue with me so I thought I would respond directly to your post. From the information you've provided it is proving quite difficult to understand what might have happened. No product is invincible to all circumstances but generally GC50 is a robust product that's used widely and performs very well. Possible variables in this case are: - The Processing
You've described this in detail and all looks well but sometimes there remain unidentified issues; example - you're prepping your car for a show and you've been using 'Back to Black' silicone spray in the workshop. An issue like this can often be the cause but is difficult to diagnose because it may not seem to be materially relevant.
- The Other Materials Being Used
- All MEKPs are not equal but the main effect they will have will be to vary the cure speed of the GC50. You've already explained that the GC50 was fully cured (sufficient to abrade without clogging)
- The Resin Research Epoxy - Not a product we have or use in the UK so we don't have direct experience. Certainly I've used epoxies in the past which have very different bond characteristics to other epoxies. This is not mean it's not a good epoxy but there could be an issue with the way it bonds to certain materials (in this case, polyester). Also, although you mention you've been using this resin for one year, unless you've been using it to bond to GC50 then we can't really infer much from that.
- The GC50 Itself
In our experience the answer is very rarely the product itself although it's sensible to rule nothing out. We have an extraordinary level of detail available in relation to your order, for example, without asking I can tell you what the batch number of your resin is (and you can see this on your delivery note) and from my side I can see exactly when it was made, who decanted and packed it and which other customers had product from exact same batch. We've not had any other reports (to date) and around 160kgs of product from that batch are already with customers. For this reason, I think we should focus on areas '1' and '2' until we have exhausted all possibilities there.
Turning our consideration to the resin, it's probably helpful to point out that if you took any cured polyester substrate and keyed the surface with an abrasive then a typical epoxy resin would bond well to it. What you're describing in the above case is that your epoxy is not bonding to a cured and keyed polyester substrate which, whether it was GC50 or any other polyester substrate, is unusual. You also mention that you've done two different infusions and experienced the same delamination issue. Were both of these parts made at the same time or were they made on different occasions or at different times? I hope you can see that my technical staff and I are here to help you solve the problem and we will always ensure you're 100% happy with the outcome. Please get back to me on the above points and we'll continue to assist. Kind regards, Matt
Matt Statham
Easy Composites / Carbon Mods - Technical Sales
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