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.

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

Warren