Does polyester resin have a use-by date?

[Greenheart]

I bought a Blue Gee GRP repair kit four years ago. Used it several times, with its terrible unforgettable toxic smell.

I've mostly used epoxy resin since, so I've forgotten what the other type looks like.

I'd forgotten that the Blue Gee variety is coloured blue. At least, I'm assuming it always was, and it makes sense...

...but it's also exceedingly thick - almost too thick to stir. Lumpy, too. I doubt I'd be able to saturate the cloth supplied with it - it'd be like trying to slather dense jelly over a bristly doormat.

Does polyester resin last indefinitely, or is mine past it?

 

[KevinT1]

Yep - given time it will go rock solid.

You mix the catalyst in to speed up the chemical reaction, otherwise boat building would take years

 

[Foolish Muse]

I'm not sure about the resin, but the hardener certainly has an expiry. About 1 year. I confirmed this with some manufacturers just a few weeks ago.

 

[pagoda]

Yep - given time it will go rock solid.

You mix the catalyst in to speed up the chemical reaction, otherwise boat building would take years

Prior to sock solid it is jelly like and does not pour well. If still liquid and the hardener is of similar vintage, for somewhere non-critical it may well still work, but is likely to take an unpredictably long time to cure. And you might well leave it a long while to lose any surface tackiness.....

 

[Greenheart]

Prior to sock solid it is jelly-like...

For a moment I thought we were off down Innuendo Avenue, but I think sock solid is even better.

Thank you gentlemen, I'll shop for new stuff.

 

[C08]

I bought 2x two US gallon tins of polyester resin at a boat jumble 12 years ago. So probably at least 15 years oldThe tins were a little rusty then and clearly a few years old then. I bought new hardener and have made a few non-critical things with it since. It cures in the appropriate time and the pieces I have smashed up in a vice with a lump hammer (offcuts from 10mm glass fibre backing pads) seem no better or worse than my previous breaking up of GRP.

 

[Topcat47]

Storeage conditions are critical. We used to keep our resins in a chest freezer, when I had a GRP workshop. We worked with "exotic" materials for the time, Kevlar Carbon and Dynema for example, as well as glass. We also had a wide variety of resins and polymers. we had a fairly high throughput of polyester resins as we made filament-wound Submarine Radomes. The other resins and hardeners, however were kept for months without deterioration. I noticed at the time that typical bodyfiller resins and hardeners (like plastic pudding) didn't last in my garage in the same way and SWMBO wouldn't let me keep chemicals in the home freezer. More recently I have kept West Resins in my "beer fridge" for some 5 years beyond their "use by" date and still been able to mix and set them. I only used them as fillers though, not for structural pieces.

 

[jwilson]

Almost all retail polyester resin already has accelerator mixed in, so it starts to cure very slowly as soon as it is manufactured. Adding catalyst then completes the curing process. As others have said, if still pourable probably usable for non-critical jobs - I wouldn't use it for hull repairs. They don't generally sell non-pre-accelerated resin retail as neat accelerator plus neat catalyst can = BANG.