Polyester resin problems.

[zoso]

HI, I have made a good start on fixing my little sailboat but today I went out and got myself some polyester resin to coat the repaired sections where I had sanded back to timber. I made up a small batch and the instructions said add 1ml catalyst to 100g of poly on a warm day, 3ml catalyst on a cold day.

So I added 2ml to 100g because it was warm(ish) thinking I would put a bit extra in to be safe but now its something like 6 hours later and it hasnt set yet!! How long should I have to wait before it sets?? what do I do if it doesn't set?? can I make up another batch of poly with like double the catalyst and paint that over the top to try and make it all set?? do I have to clean it off and start again?? help!!

[hansp77]

no no no,
don't coat over it.
same mistakes have been talked about here somewhere very recently...

I am not sure of the setting time with poly resin,
but if it hasn't set in that time, you gotta clean it off and start again.
If it is still recent, you migh be able to try to heat through the whole area..
but I use epoxy- not poly- so I don't know..

[hansp77]

Hey Zoso,
here is that link,
http://boatdesign.net/forums/showthread.php?t=12713
good luck

[zoso]

Cheers for the reply, I had feared that might be the only solution

Oh well its night time now so I'll wait till the morning and have a look. I get the feeling this will be a messy job tommorow

[lewisboats]

Hit it with a hair dryer, if it doesn't jell in a few minutes, break out the gloves and acetone and clean it off. Suggestion: go online and browse for epoxy "tester" kits, get one of those.

[marshmat]

If it doesn't gel after a few minutes of heat as the others have suggested, it's shot. You gotta get it off, all of it. This is pretty common- even if you think you've mixed enough, remember you're mixing at a ratio of only 1-2% and that ratio must be perfectly uniform through the entire mixing cup. If it's not, it won't set right. As usual, epoxy is a helluva lot easier. But poly does work, if you're patient and take the time to mix, mix, mix for ever. (Tip- add 1 drop, mix, add 1 more drop, mix, etc- this makes it mix more evenly than adding all the MEKP at once).

[zoso]

Ok, I woke up this morning and it has set in places, gone tacky in others but at least it has begun to set! I think it was colder than I thought yesterday and last night was freezing so probably not much happening. Today is much warmer and it appears to be setting ok. I might try the hair dryer trick though just to finish it off. I think perhaps the catalyst wasnt mixed well enough, I mixed and mixed for ages... oh well I'll just let what sets set and try to clean anything that doesnt set off.

Thanks for all the help guys!!

[lewisboats]

Next time, try warming up the resin before adding the catalyst, it will thin down a bit and mix better.

Steve

[ernie]

I mixed some poly once to do some repairs outside, hoping I could get it to kick before it got too cold that night. I didn’t, and the cold snap lasted for a couple of weeks. I also happened to work a lot of OT during that time and didn’t get back to cleanup and redo the work. On the first day of warm weather the gel kicked, it had only sagged a little, so I was lucky.

[roy marine]

The original question is almost a year old, however I read many questionable responses.

The writer may complete the curing process by simply mixing a "hot" batch and painting over it. I write this without knowing all the details but I have used old hardener and/or old resin and corrected a slow cure with this technique.

If the uncured batch had contact with water or moisture from working late in the day or above 75% humidity the resin may not cure.

Also when polyester resin is used as a "paint process" the layer may be too thin to produce enough heat to cure. Here a second 'hot' batch may save things.

Remember polyester resin never completely cures. It is always reactive and hence great for secondary bonding, typical of repairs.

Epoxy has advantages in the presence of moisture and as a barrier below the waterline. Epoxy will cure anywhere but polyester will not cure if anything 'attacks' it during the cure period when it is highly reactive and vulnerable.