Epoxy not gone hard

N

nmeyrick

Well-Known Member
Joined
26 Sep 2007
Messages
259
Visit site
I mixed up a batch of SP106 epoxy the day before yesterday using their slow hardener and microbaloons to make a fairing compound to create a waterproof barrier over an exposed section of hull to deck joint behind the bow roller fitting.

I have used the same hardener before and it had set hard after the amount of time that the current batch has had. The latest batch however is still tacky and pliable, but is much firmer than it was originally. I had mixed it to the consistency of mayonnaise and it now has the consistency of a firm putty. It is difficult to scrape a stick through it, and will hold the shape it is left in without flowing.

I had mixed it by measuring out with a spoon using the correct ratio, i would have to admit it may not have been 100% accurate but I have used the same approach in the past without success.

I don't have a problem it if takes a while to set as it is not load bearing, but obviously if it won't ever cure completely I will need to clean it off and start again. So the question is does anyone know how likely it is that this epoxy will eventually set fully?

My understanding from the reading I have done is that if the proportions were wrong it would not have set as much as it has and so it should go on to set properly given time but can anyone advise on this, or at what point I should assume it is dud and cut my losses?

Thanks
Neil
 
It is important that epoxy is mixed accurately in the correct proportions, and that the two parts are thoroughly mixed together.

Epoxy "cures" by chemical reaction between the two components unlike polyester which is a catalysed reaction.
 
Epoxy is very temperature dependant and I have found it quite fickle at times... After this time, i would chisel it out and start again.

It's possible that the temperature wasn't high enough for long enough, especially for the slow hardener. If you did the mixing in the late afternoon then it could be that the evening cool air brought the temperature too low and the chemical reaction stopped. No amount of heating will get it to go off after it has cooled, this has all heen in my experience... ymmv
 
Using a spoon is acceptable but you'll have to mix a relatively large batch.In small amounts the margin for error is just too large.I'd guess you didn't mix enough to minimize the loss of accuracy.I suggest that next time you use syringes.
Try and warm up the area for a while.That'll work if the epoxy is not curing due to low tmperature but not if it's been mixed in the wrong proportions.
 
Think of Epoxy as a 3 pin plug and the hardener as a socket.

There needs to be the right amount of pins for sockets otherwise it won't set. Too much of one or the other and you end up with a gooey mess. (or have ended up in your case)

This is why the measurements of epoxy is more critical than polyester.

It's also worth checking the use by date as well.

Now then, are you really, really sure you mixed it up as per the instructions? not just how you remember them ;)

Out with a knife and acetone and start all over again...Sorry
 
I had a similar problem recently and got excellent tech support from the manufacturer, Gurit. I e-mailed the contact on their website and somebody phoned me back within two hours and spent 15 minutes discussing posible causes. In my case it was a mix of temperature and using meths as a cleaning agent on the ply.

I was most impressed by their keenness to help me get it right.

The generic e-mail is marine@gurit.com and they sent me these contact details for any future problem ( I have deleted the guy's name and personal e-mail just in case printing them here would cause him to be bombarded with spam - I can PM them if you need them):

________________________

Subject: Fw: Tech query - varnishing plywood coated with SP 106 epoxy


Good afternoon David

We spoke with regard to the SP 106 on your boat following your e-mail below

If you would like to contact me in the future for any reason my details are below

With regards


#######
Composite Technologist
Gurit (UK)
St.Cross Business Park
Newport
Isle of Wight
PO30 5WU
England


################
website www.gurit.com
 
Last edited:
It's more likely to be a ratio problem (or perhaps hardener gone off ? - best to check with a test sample before repeating the exercise) than temperature.
In the past when I've mixed a tad too much, I've quickly put the excess in the fridge, in the hope of using it a few hours later - but in all cases it hardened .... even in the fridge !
 
I've used SP 106 and microballoons quite a bit now. First of all, was the hardener straw coloured or dark red and stinking of amonia? The latter means it has gone off somewhat. I find the hardener goes off pretty quickly once it has been opened for the first time.

Secondly, the temperature could have dropped. The slow hardener can be pretty slow below about 20 degrees. If you can get some gentle heat on it, you MIGHT get a more complete cure even now, but as others have said, I doubt it. You've nothing to loose by trying anyway!

Also, (as has been said), mixture ratios are absolutely critical with epoxy. Mix by mass or by syringe, but spoons (or anything with a big top surface area compared to its volume) are likely to be innacurate.
 
Thanks for all the input guys. Sadly even after today's heatwave here it still hadn't set, so had to come off. Fortunately it wasn't hard enough to be too difficult and scraped off without much agro.

On closer inspection both the resin and hardener were out of date so i suspect this was the cause of the problem. The only alternative available was a two tube epoxy glue which I mixed some microbaloons into to make a paste, and that did th job admirably in about 5 mins. One to chalk down to experience I guess

Cheers
 
nmeyrick said:
On closer inspection both the resin and hardener were out of date [...]
Click to expand...
Thought I'd pass on this tip, for those who buy epoxy in bulk, but then use it sparingly over a long period ....

Epoxy glue consists of two components - Resin and Hardener. The Resin is chemically inert, but the Hardener has somewhat similar properties to a catalyst (but is NOT a catalyst in the true sense) in that it has active chemical properties which 'go off' in time - hence the expiry date.
This expiry date can be considerably extended by slowing down the chemical ageing process by simply storing the hardener in a fridge (I find the salad compartment is best), having removed as much air as possible from it's container to exclude oxygen. It is then only necessary to bring to room temperature before using.

I buy 2:1 mix epoxy in 3Kg amounts at a time, and on receipt immediately decant the 1Kg of Hardener into 100ml containers, then store these as above. The result is that epoxy with a guaranteed shelf-life of 12 months is still useable after 3 years.

I used to store my 35mm films like this, and still store non-rechargeable batteries in the same way.

But the idea is not mine - I used to work in Kodak's Quality Control Labs., and samples of silver halide product were routinely stored under refrigerated conditions to act as reference material for any subsequent 'post mortems', should any problems occur later with the film or paper. I don't remember any 'post mortems' ever taking place but, by storing like this, the products were still useable a decade or more after their expiry date - which I can confirm, as samples of these samples were subjected to routine testing from time to time.
 
You must log in or register to reply here.

Share this page

Top