Epoxy and Amine Blush

Robber58

Robber58

Joined
Oct 9, 2008
Messages
463
I thought I would share something I just encountered with some epoxy. I had glued up a handle with ironwood scales using G/Flex and let it rest over night as always. It was in my workroom where temperatures range in the high 60's. When I checked it I found the epoxy seemed hard but there was a sticky coating on the surface. I let it set for another day and the sticky surface was still there. I assumed that I had a failure of the epoxy and was mentally preparing myself to destroy some really nice (and expensive) ironwood. I am always very careful in measuring and mix for at least five minutes so I assumed I had a shelf life problem, even though I had only had it for 6 months or so. As I was building the courage to remove the scales, I did a bit of research on line and found that shelf life with the G/Flex is very long but there was a common problem with it and some other epoxies. Under the right conditions, the amine in the hardener will react with moisture and carbon dioxide in the air and form a waxy, sticky coating on the exposed surface called Amine Blush. It does not affect the strength or bonding of areas not exposed. Removing it is as simple as washing in hot water and detergent. I tried it and sure enough it came right off and I had the smooth, hard surface I was expecting.

Based on what I read, this is pretty common with West Systems epoxies (as well as some others) and can be aggravated by high humidity and gas heaters due to the CO[SUB]2[/SUB] they generate. I am a mechanical engineer, not a chemist, so the technical details are over my head but I was more than happy I found this information. I hope this can be of help to others.
Randy
 
I sell alot of epoxy resins in the concrete industry and amine blush is a common problem. I usually tell my customers to wipe with a solvent to remove and then wash with water/soap if needed.
 
As Steve mentioned above, this is a common issue. Boat/canoe builders who build up layers of epoxy and fiber cloth need to deal with blush regularly. Its a bit disconcerting when you first encounter it though, eh?

-Peter
 
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