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Author Topic: Resin not hardening completely  (Read 842 times)

Nordlys

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Resin not hardening completely
« on: April 09, 2020, 08:53:10 AM »

Is there anything I can do to get this Easy composite resin to harden properly?
It's not wet but remains slightly tacky after 3 days. I wouldn't be able to scrape off the layer, it's not that soft.
I found it rather a difficult mix ratio to achieve at 100 to 30 for a small batch.
N
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Taranis

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Re: Resin not hardening completely
« Reply #1 on: April 09, 2020, 09:46:35 AM »

I would contact their help desk for advice
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Nordlys

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Re: Resin not hardening completely
« Reply #2 on: April 09, 2020, 10:20:45 AM »

Yes, I did contact them.
They said that low temps in workshop is not ideal. So since then it's been in the sun and indoors but doesn't appear to be drying much at all.
I was thinking of covering the whole area again with zpoxy resin,  this does harden very reliably.
This might be my only solution?
N
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mrzippy

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Re: Resin not hardening completely
« Reply #3 on: April 09, 2020, 10:29:02 AM »

Guessing we are talking EC. Epoxy - if so I use the same resin and suffered the same problem in cooler weather, especially with their slow setting catalyst mix.
I called Easy Composites and was told it's Anhydrous (absorbs water) while setting?, which seemed really odd to me !
and to leave my model next to a hot radiator to warm it up.

Tried this with little change after 3-4 days, still tacky, spoke to a pal with knowledge of the moulding industry, here parts are autoclaved to high temperatures, I spent an afternoon blasting the model with a hair dryer to get the surface very hot and this eventually sets it off - it seems to go almost glossy when cooked.

Last week I skinned another model with EC. slow set and used the hair dryer straight away, spent the evening heating up it up eventually it cured to a hard gloss.

Seems a great shame this happens, I like the 90 minutes working time allowing plenty of time to skin a hull in one session,
but clearly something needs addressing by the manufactures, hair dryer to the rescue - it can take hours of on and off heating,
but does eventually go off.  regards Paul
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Tugtower

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Re: Resin not hardening completely
« Reply #4 on: April 09, 2020, 10:57:14 AM »

As a trick get some of the hardener on your finger and rub the surface of the epoxy, it wonít cure it all the way through but it will stop the surface being tacky.


Common problem when mixing any epoxy/resins if you donít get the ratio correct then you have a mix that wonít cure or takes a very long time to finally set.


We have all done this!!


Take this as a lesson and just try to get the ratios better in future... usually when itís resin product (glassing etc) itís usually done by weight, or ML measure, 4:1 etc... either way weight or Volume getting the correct mix isnít usualy difficult even for small batches.


When is epoxy glues, itís generally a 50/50 mix.
When itís p38 or other compounds that are two pac, itís a pea size amount of Hardener to the mix, genrallly thatís the rule even on small quantityís.

DaveM

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Re: Resin not hardening completely
« Reply #5 on: April 09, 2020, 10:58:11 AM »

It's probably nothing like as cheap as EC's epoxy but I've always used Z-Poxy Finishing Resin and I've never had any problems like this. It's a 50/50 mix which is pretty easy to achieve, especially if you use graduated plastic medicine cups or micro-scales. Once mixed I thin it 10-15% with 99% pure Isopropyl Alcohol to make application easier with a brush and increase the working time. It seems to contain some sort of filler medium because it sands beautifully with 320 through to 600 aluminium oxide paper.
Meanwhile good luck with the hair-drier   <:(
Dave M
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Nordlys

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Re: Resin not hardening completely
« Reply #6 on: April 09, 2020, 11:26:18 AM »

I felt a bit relieved that someone else has had the same problem with the Easy Composite brand resin pack! Fast cure.
I did try to get mix correct but 3 1/3 to 1 is a tricky ratio because I don't calibrate by weight just a measurement on a jar.


And as Dave says Zpoxy is 50/50 and very reliable even with approximate measures.
EC was 26 pounds with postage
N.

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mrzippy

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Re: Resin not hardening completely
« Reply #7 on: April 09, 2020, 01:12:19 PM »

Interesting - not had the problem with the fast setting variant !
but has happened 3 times with slow set - concluded working in cold weather etc.

The Easy Comp. mix applied last week to the inside of a hull, was an attempt to test what I have in stock (unfortunately too many quids worth),
and measured out deliberately in specified the 100-30 quantities (my illness provides a free supply of used hypodermics),
true to form wasn't setting, hence wading in with the dryer.
Next week I hope to be glassing the outside and will keep you posted,
looking like shopping trips Stoke, calling in at Easy Comps enroute days are numbered !

Thanks Dave will give Z an airing, liking the sound of the filler medium properties -
I added Microballoons to SP113 resin in the good old glider glass wing skinning days - to aid sanding on soft balsa,
sounds like a similar brew, any thoughts of how long working time is extended with Isoprop?
the Easy Comp 90 minutes has been a godsend for my nerves, but repetitive failures are becoming annoying.


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SailorGreg

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Re: Resin not hardening completely
« Reply #8 on: April 09, 2020, 02:04:20 PM »

I would recommend buying some cheap kitchen scales.  Measuring ratios for small quantities of epoxy is always fraught, but scales that can meaaure to the nearest gram will help a lot.  They only cost 10 or 15 quid, and will minimise the grumpy factor when the bloomin' stuff just won't go off!  My initial problem with scales was that I kept overshooting on the hardener, so then had to add more resin, oops, need a drop more hardener.....  >:-o .  But practice makes perfect!

Have you tried wiping the surface with acetone?  That might work, it did for me once.  Just a thought.

Greg

Nordlys

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Re: Resin not hardening completely
« Reply #9 on: April 09, 2020, 02:20:36 PM »

I started out this morning warming the hull on radiator and blowing with fan heater. When cold it is very sticky.
Once it was well warmed up I tried sanding the hull, removing what I could of the resin. It did become powdery and appears to be drying now.
Been in the sun all day curing ( I hope).
I should have used the Zpoxy from the off like I always have done but having bought the EC stuff I thought I would try it.
Mistake.
Keep me posted Mr z I'm interested in how you progress.
Thanks to all, they have been very helpful replies.
I thought I was on the brink of disaster.
N.
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RST

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Re: Resin not hardening completely
« Reply #10 on: April 09, 2020, 03:21:33 PM »

There folk frquently talking about resins on rcgroups forum.  If it's an epoxy there will be an amine / wax that floats to the surface (same for just about any epoxy coating).  Sometimes if you don't get rid of that there's problems with curing. Need to use a solvent then sand back. Sometimes just sanding grinds the wax in.  I've not had experience myself. I've stuck with z poxy these days.
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Tug Fanatic

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Re: Resin not hardening completely
« Reply #11 on: April 09, 2020, 03:40:56 PM »


.................... If it's an epoxy there will be an amine / wax that floats to the surface (same for just about any epoxy coating).  Sometimes if you don't get rid of that there's problems with curing. Need to use a solvent then sand back. .....................


Amine blush is water soluble. If you have allowed your epoxy - any epoxy - to fully cure you are likely to have amine blush which I remove with soap/ water and either a nail brush or one of those green abrasive plastic pads that my wife has around the sink. Rinse thoroughly. I always do this before I paint and if I am going to bond something to an already cured surface.
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coch y bonddu

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Re: Resin not hardening completely
« Reply #12 on: April 09, 2020, 10:20:51 PM »

not only is it a case of the right ratio mix it is a case of getting the right ambient temperature in the workshop for the catalyst to have enough heat to start off the catalyst reaction, and then for resin to do its part and react to the catalystÖÖÖ...a case of exotherms and endotherms reacting at the right times...ÖÖ.and if you don't have that heat to start the process the resin will stay sticky for months...

Dave
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mrzippy

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Re: Resin not hardening completely
« Reply #13 on: April 15, 2020, 02:16:15 PM »

Hi Again,
Applied a layer of Easy Coat (slow hardener) lightweight glass skinning over a new hull last night,
taking around the hours working time to complete the job, then as predicted, spent the following 2 hours hair drying to start the cooking process.

Seems to take an age of blasting on full heat before anything happens - the heated resin goes through a runny stage with the occasional drips onto the bench, eventually becoming tacky and starts curing, took 11/2 to 2 hours before the surface changes to a semi-matt sheen.
Placed in front of a radiator over night and it cooks to a hard glossy finish.
I'll be using up my remaining stocks of Easy Comp on household diy jobs and jumping ship to another brand for modelling, enough is enough ! Paul
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Baldrick

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Re: Resin not hardening completely
« Reply #14 on: April 15, 2020, 02:47:20 PM »

reminds me of when the supplier sent me a bottle of resin and a bottle of hardener , trouble was the bottle of resin was mis labelled and I had been sent two bottles of hardener . what a mess trying to clean it all off.
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SailorGreg

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Re: Resin not hardening completely
« Reply #15 on: April 15, 2020, 06:35:38 PM »

Just to redress the balance a bit, I have used Easy Composites resin (and other stuff) a fair bit and never had trouble with it.  I have never had to heat it to make it cure, although if you are in a hurry that is fine.  The times I have had trouble with epoxy are due to a contaminated surface or thinning it.  (Or I got the proportions wrong!  %) )  Thinned epoxy doesn't seem to cure hard, but can stay a bit rubbery.  Guess which of these two remnants from the mixing pot I had thinned?






mrzippy

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Re: Resin not hardening completely
« Reply #16 on: April 17, 2020, 10:59:46 AM »

My problem finally solved with Easy Composites slow setting resin - I've had no problems with their fast setting version,
to put the record straight here's whats happened over the past 2 days -

Before attempting glassing the other side of my hull I called Easy Comp. Stoke HQ, not expecting to get a reply and their technical guy answered the phone -
the one person I've not been able to reach on previous occasions !
I explained the problem of slow set epoxy not curing, remaining tacky etc. he knew exactly what was wrong and explained -
EL2 slow set has a pot-life of 95-115 minutes, but also a long 'de-mouldable time' of at least 30 hours at importantly 20 degrees C.
This explains nicely why my previous attempts in cold weather (winter) failed, nowhere near the magic 20 degrees and taking an age to cure.

Also very interesting - providing you keep to EC's 100 - 30 ratio, you can mix their fast and slow setting hardeners to vary the pot life !
again this affects overall curing time, another factor not brought to light during previous chats with EC staff.

I'm now pleased to report I've skinned the other side of my hull and baked it throughout yesterday in a very hot south facing conservatory,
kept the heating on overnight and this morning 30+ hours later its cured all ok, finally cracked it - the long pot life requires a very long curing time with lots of heat,
and with that gentlemen I'll get my coat, I'm off to eat a large slice of humble pie.  Paul

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Tug Fanatic

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Re: Resin not hardening completely
« Reply #17 on: April 17, 2020, 11:37:16 AM »

I am pleased that you have solved your problem even if, with what seems to me, a difficult method to achieve success.

Why did you choose the slow hardener in the first place?

The slow hardener with a pot life of over 100mins, a gelation time of 8.5-10.5hrs and a demould time of 20-30hrs at 25 Centigrade would make it of little interest to me.

The slow hardener has a pot life of 12-17mins,  a gelation time of 2-3hrs and a demould time of 4-6hrs at 25 Centigrade. This is much more typical of what I think of as normal and much more useful to me.
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mrzippy

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Re: Resin not hardening completely
« Reply #18 on: April 17, 2020, 01:21:04 PM »

I use fast hardener myself on quick simple jobs no probs, the slow I use for glass skinning hulls or large fuselages and wings,
using tricky delicate lighweight glass cloth and usually cover the entire hull/fuz. in one hit !
taking around an hour to complete the job, hence the slow hardener - no panic stations.
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Tug Fanatic

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Re: Resin not hardening completely
« Reply #19 on: April 17, 2020, 02:35:48 PM »

Sounds like a mix of the 2 hardeners would probably suit us both. I wonder if the times are linear between the 2 sets of individual numbers depending on relative quantities and at what proportions the high temperature requirement of the slow hardener effectively ceases to be an issue.
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mrzippy

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Re: Resin not hardening completely
« Reply #20 on: April 17, 2020, 07:21:25 PM »

Hi Tug Fanatic,
Try contacting the same the technical guy I managed to corner yesterday, he seemed more than willing to chat in great depth about their products, and certainly knew them inside out, stressing how their epoxies are technically more advanced than the likes of West Systems, and the need for absolute accuracy when measuring out the smaller quantities modelers are likely to use etc. Paul
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