polyester resin shelf life

[Ssor]

I am bewildered. I have a gallon can of Evercoat finishing resin, maybe 2-3 years old, still pours from can, no lumps in it, but catalysed @ 3% it still will not harden. Does MEKP go bad? I have had polyester resin start to harden in the can but has anyone found that it wouldn't harden? I have used this same can in the past with good results.

[Ssor]

I believe that I have answered my own question. The MEKP that I used initially was about three years old in one of those little 40cc clear plastic tubes that had been exposed to sunlight in my garage. I mixed another batch and used some MEKP that I had in a half gallon jug in a cardboard box in my basement. The batch mixed with the MEKP from the basement gelled and hardened in the proper length of time. So I think that the answer to my question is, Yes, MEKP can deteriorate with time. The MEKP from the tube didn't smell right, not that sharp acrid odor that is characteristic. I guess the conclusion is; if you have any doubt about your catalyst, buy fresh.

[Herman]

Indeed, Mekp goes bad under influence of sunlight. Try and store it in a closed container, in the dark.

If the polyester resin is still what it should look like, it usually is still OK, but do some testing beforehand. (geltime could have drifted somewhat).

[Ssor]

Herman,
Thanks for the confirmation. I always test, if I haven't used the resin recently.
Ross in BelAir