Epoxy not gone off...

Iain C

Iain C

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I buy my epoxy and associated gubbins from East Coast Fibreglass, and very good they are too. So far this winter I've used 7kg of the stuff on all the structural repairs I've been doing plus the rebuild of my rudder following tang failure.

I opened a brand new can this week, to apply the biaxial reinforcement to the edges of the now complete rudder, and it's not gone off. 36 hours now and it's still tacky, although very, very slowly going in the right direction...and for 24 of those hours the rudder has been in a nice warm house.

I've pretty much ruled out any issues such as cold/damp/mix ratio error/surface contaminants. I mixed two batches from the fresh, sealed tin and they are both duff, and I am rapidly coming to the conclusion that there might be a bad batch of epoxy out there.

Has anyone else had any issues with ECF's own branded general purpose laminating epoxy that's been bought very recently? Unfortunatly they are now closed until the new year so I can't ask them the question...and I really want to get on with the job.

I guess the next plan is to mix up a very small test quantity just to make sure...but any feedback welcome.
 
With epoxy you have to get the proportions pretty much perfect, less than 1% error IIRC. If you get it wrong, it will take a long time to cure. Also, is the epoxy rated at the temperature you applied it at? The lower temperature is critical.

I had the same problem with West Epoxy, for both reasons (their pump system helps with the mixing). Their man said to warm it above 30° C, or 40° C if possible. I did this and it fully cured overnight.

I'm considering making a "hot box" for such projects: an insulated box with a fan heater inside.
 
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I made a mistake once when missing West Epoxy.
I knew the ratio was 5 to 1 so I did 5 squirts of resin to 1 squirt of hardener using their dispensing pumps.
I had forgotten that that the dispensing pumps were already doing the correct ratios. i.e. one squirt of resin needed to one squirt of hardener.
In effect I had done a 25:1 mix.
Took about 48 hours to go off but it did finally go off. Put electric heater next to it.
However, whilst it went off mixing ratios are important and my mix would have been significantly weakened.
 
If the OP's already got through 7kg of the stuff, I think we can assume he knows how to use it and discount user error like mixing proportions. 24 hours at room temperature would definitely set any of the West or SP epoxy I've used too.

Does sound like a manufacturing or labelling error is a possible cause, though I've not come across such a thing.

Pete
 
The only time I've had problems with epoxy was when I allowed the activator (as opposed to the resin itself) to go off - it became brown coloured and stank of urea. Now I always keep the activator in a fridge - it trebles it's shelf life.

If the epoxy is 'good', then cure temperature isn't that critical (despite what many folk say) - I've had mixed epoxy kick-off even after placing it in the freezer, when I'd hoped it would 'keep' for an hour or two.
 
Thanks for the replies chaps. The rudder was in a vacuum bag in a shed heated by a fan heater overnight so it should have been absolutely fine. It really is a mystery to me...I've been playing with epoxy for over 10 years now on various dinghy builds and I've never had this happen before.

TBH in my experience 1% mix accuracy is unlikely...that's a 1ml error in a 100ml mix and that 1ml would be left in the nozzle of the syringe! It really does not have to be quite that exact...measuring cup/pumps/syringes will be just fine.

It's slowly, slowly going, but as this is my rudder I'm bonding (nothing important then!) I am going to scrape it all off and start again after doing a test mix.

If I was doing a really high load/minimal material/light weight dinghy application I would probably use West or SP but the ECF stuff seems fine for what I have been doing. It just seems odd as...

-I'd like to think I know what I'm doing
-The shed temperature was much higher than it was for previous jobs that went fine
-The first time this has happened was on opening a new can
-I mixed two batches for the job, and they've both gone wrong
-After nearly 48 hours it's still tacky...I would have had to have got both batches very wrong...

I have seen bad batches of epoxy...does anyone remember that "science of sailing" programme...IIRC they had to basically junk the first Assa Abloy VO60 hull due to a dodgy batch of epoxy that did not cure...
 
Rather than the epoxy I'd suspect the curing agent as being over the top - it's very susceptible to aging.

It will probably finally cure - give it about 3 weeks.

As already said, unlike polyester, temperature is not particularly significant with epoxy.

Interestingly, most professionals I know prefer polyester to epoxy because it's far more reliable.
 
My West 'B' pack pump puts out 28ml not 25 as it should and it still goes off with 5ml of hardener. I only use the pumps to dispense and use an electronic scale to measure because of the problem with the pump.
 
I use electronic scales for measuring epoxy resin. I kept finding that the pumps gummed up after while and gave the wrong mix ratio. I Also use hardener that has 'gone off' for non structal work such bonding a pad in place to spread loads on through bolted fittings.
 
electrosys said:
If the epoxy is 'good', then cure temperature isn't that critical (despite what many folk say) - I've had mixed epoxy kick-off even after placing it in the freezer, when I'd hoped it would 'keep' for an hour or two.
Click to expand...

That probably because it generates quite a bit of it's own heat. If it was in a tub or pot rather than a thin film it would go off in a freezer.
 
Some epoxy which applied in a dinghy build failed to go off. It was too cold for the first 12 hours or so. After that it seemed that no amount of heat would make it go off. Kind of uncontrolled experiment whose details I can't remember. However I came away with the prejudice that if you don't have a sensible temperature at the start you can't resolve the problem by applying heat later. (When I say cold, I mean below 7 Celsius - I have found that Epoxy will cure down to about 7 - slowly - but not below.)
 
Any silicone nearby?

You might think it a strange question, but I did quite a lot of critical epoxy stuff that turned into the sort of sugary gunk that you'd find around the neck of a Grand Marnier or Courvoisier bottle.

Sort of crystals, but of no use.

Further experiments showed that mixing (admittedly very small quantities) on anything but plain paper/cardboard did the same. Anything colour printed/photographic (Cornflake box) would not cure.

Using Mr Sheen as a release agent was a complete negative. I used to treat my bench with the stuff to keep it cleanable, but found that if I used epoxy near it, no cure. Glued up an electric violin frame on said bench around a jig coated with Mr Sheen. No dice. Heat didn't help.

Removed all the polish with evil stuff, no problems since.
 
charles_reed said:
Rather than the epoxy I'd suspect the curing agent as being over the top - it's very susceptible to aging.

It will probably finally cure - give it about 3 weeks.

As already said, unlike polyester, temperature is not particularly significant with epoxy.

Interestingly, most professionals I know prefer polyester to epoxy because it's far more reliable.
Click to expand...

Epoxy as I understand it is a mixing of 2 parts which together make the final resin. The "hardener" is just another component. Unlike polyester where the hardener and catalyst are in small quantities that simply make hardening happen. ie Calling the hardener a "Curing agent" is misleading.

Epoxy is used in most critical applications. Ask Mr Boeing or Airbus. Polyester is perhaps more forgiving to amateurs but I would not think professionals would consider it more reliable than epoxy. On the other hand perhaps the retail handyman type epoxy is unreliable as OP seems to have found. Professionals use polyester for making molded components because it resists UV and is cheaper. good luck olewill
 
me too

west has always worked beautifully for me

across a wide range of abuse scenarios

I had a 5kg batch of epoxy from

http://www.epoxy-resins.co.uk/

and failed mto make it go off

tried every combination of mix and heat and time

still no luck

when I contacted UK resins Rob told me there was nothing wrong with his resin and it was obviously my fault

not being much of a fighter I put it down to experience and went back to west systems

the uk stuff is still in the garage and over this last project I thought I would try again with it

still no luck

still a bit sad

but the old west stuff still worked a treat

so west has been great for me

Dylan

incidentally duck punt now has undercoat on it and is on schedule for jan 1 launch

http://www.keepturningleft.co.uk/kt...e-wash/ktl-255-duck-punt-first-coat-of-paint/
 
incidentally duck punt now has undercoat on it and is on schedule for jan 1 launch
Click to expand...
Too late to bag a couple of ducks for Xmas lunch then :)

Thanks for all the insights into using epoxy. I have a job coming up as soon as the weather is warm enough for which I will I think prefer to use epoxy rather than polyester.
 
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