Epoxy compatibility???

[lobsta1]

Removed a couple of old xducers. Ground down inside & outside out to about 5" on a 1" hole. Temp was in lo 50's. Was at the end of a gal. of West epoxy. Epoxy & hardener are about 5 years old. Using pumps mixed up a batch of the goo. Had my small to large pieces of woven roving all precut. Precoated the holes & waited about 40 minutes for it to tack up. Then the fun started. Dipped my 1st piece of roving in the tray to saturate it. Almost as soon as the roving hit the epoxy, it started to kick off & get stringy. Tried using it anyway on the outside but the glass ended up falling off. Mixed a smaller batch for the inside ( with the lo temp I thought the larger batch would be OK). The smaller batch did the same thing.

So, is my epoxy/fast hardener to old? Could I have roving that is treated with styrene? Don't think so as I have used it before. With all the gallons of epoxy I've used through the years, I've never had anything like this happen before.
Thanks
Al

[Buju]

If you waited long enough for the thin film you applied to the hull to tack up, then its a sure thing the larger volume in your tray/cup had already began to polymerize.
The fast hardener should (IMO) only really be used for very small batches (1 or 2 pumps) in which you're going to be applying it within a few minutes.

[Peter]

FWIW:

I had occasion to use some 6 or 7 year old left over West epoxy and fast hardener on a project. Not boat related so it wasn't critical if it didn't work. I was skeptical if it had exceeded its shelf life, but everything I could find said that shouldn't be so. I had no problem with it. My old stuff worked just fine!

Peter

[lobsta1]

I gave misleading info. I mixed a small batch, precoated & waited forty minutes on that. Then I mixed up the bigger batch & IMMEDIATELY started with dipping the woven roving & getting the problem. The first precoat batch without the roving was fine. That says to me the epoxy/hardener was OK.
Al

[Peter]

I do not know of any chemical accelerators for epoxy. So I do not know of any contaminate that might cause a faster cure. But I am no chemist.

However,..... of course you already know that the cure time for epoxy is very temperature dependant. What may not be obvious is that this time of year, particularly in New England, the outside "free air" temp can be 60-ish, but where the sun beats on the work surface temps can be much higher... especially if the color is dark, not white.

I learned about this doing a polyester resin fiberglass project a few years ago. The outside air temp showing on my thermometer was only 58. I started out concerned that things would cure properly, 58 being a bit cool for this sort of work, and since it was poly I added an extra dose of catalyst.

It turns out the work piece was actually closer to 90 degrees because it had been sitting in the sun. As soon as the resin hit that heat it kicked!

Minor disaster... Lesson learned.

Peter