West system epoxy curing times

[steveeasy]

Just mixed up some west system epoxy 100mil &20 mil fast hardener. It’s about 12 degrees and I expected it to start curing within an hour.

Any top tips on curing times.

Steveeasy

 

[Boathook]

@steveeasy
It will start to thicken after about 20 minutes but will require a good 24 hours to cure. Dampness is a big problem for curing and will slow the process right down. A tubular heater makes a big difference or a fan heater, but no direct heat.

If the hardener smelt a bit or slightly brown in colour, it is past its best and will take longer to cure. It also starts to loose structural strength, but how much, etc I'm not sure.

 

[B27]

A bit of attention from a hairdryer will encourage it to cure quicker and better, and also make it run into joints and stick better.
Using the hot air on the work before applying the epoxy helps drive out moisture.

 

[steveeasy]

Thanks for the replies. It’s gone off nicely now. Bit inpatient I expect!!.
Steveeasy

 

[rogerthebodger]

I have put small items in an oven to speed up curing of epoxy or polyester resin.

 

[MisterBaxter]

It sets faster if you're applying it in big chunks - the reaction is exothermic but also accelerated by heat, so a bigger blob goes into a chain reaction, getting hotter and hotter, setting faster and therefore giving off heat faster. Thinly applied layers are slower to set.

 

[steveeasy]

I have put small items in an oven to speed up curing of epoxy or polyester resin.

ill chop the bit of my skeg off then, Have you a big big oven by any chance?

Steveeasy

 

[Poignard]

@steveeasy
(...)
If the hardener smelt a bit or slightly brown in colour, it is past its best and will take longer to cure. It also starts to loose structural strength, but how much, etc I'm not sure.

That's interesting. I didn't know that.
And a bit worrying as I have some WEST hardener that is more than 20 years old that I was planning to use this summer!

What about the resin, does that have a shelf life?

 

[Ian_Edwards]

It helps to warm the resin hardener and the work piece if you can.
Higher curing temperatures, within reason, produce stronger products by increasing the crosslinking. The higher temperature can be used during normal curing and post curing. That's one reason why critical carbon epoxy structures are often autoclave.
Higher curing temperatures can also increase the tg, the glass transition temperatures. The point at which the epoxy starts to loose its mechanical strength.

 

[Boathook]

That's interesting. I didn't know that.
And a bit worrying as I have some WEST hardener that is more than 20 years old that I was planning to use this summer!

What about the resin, does that have a shelf life?

I would only use it as a filler, assuming it sets. Might be worth trying a small mix to see whether it cures. Any thing vaguely structural I would use new epoxy resin and hardener.