Unprecedented Problem in Epoxy Casting

It evaporated. 100% solids epoxy will not sublime. Any solvents and low molecular weight components may flash off, but the solids won't go poof.

I agree with lyn.

Also, if you are sure you mixed properly, I suspect that you may have received a batch of hardener with a much higher ratio of thinner added, than should have been.

Can you order your epoxy, hardener (undiluted), and thinner, as separate components, and do all of the mixing yourself?

Did you do your mixing by weight, or by volume? There's a big difference. Hit the full screen button on this link and you'll see in the first two columns.

Hello lyn and kramarat

Thank you for your observations

The said Epoxy system was supplied by the manufacturer as a Two-part liquid epoxy system for room temperature cure. We had ordered the same for our Boat construction works. The mixing proportions are in the ratio 100 : 50 (Resin : Hardener). They have stated that the system DOES not contain any volatiles.

We did the following Tests, as soon as we received the initial samples":

(i) One 60 gm (40 gm Resin and 20 gm Hardener) CASTING ... as per original photo presented in my first statement

(ii) A 300 gsm Glass-mat Epoxy as per photo below:

There was no problem seen with the Same Resin + Hardener in the case of the Glass-mat Epoxy Composite. The problem was seen in the Original Casting.

It is to be noted that the casting was seen to be perfect for a whole week after the date of casting. It was then placed inside a cupboard and observed again ONLY after another 40 days. The casting had (at that time) virtually vanished... weird and unbelievable!!! No convincing explanation from any one has come forward so far except a suggestion of the possibility of some Phenols/ cresols having been incorporated as diluent in the original resin. But, will un reacted phenols "eat up" epoxy? If not what could be the real cause for such weird behavior?

Thank you kramarat

Your observations seem sound and logical

I shall do as per your suggestion and see how the materials behave

Thanks again

I've used low viscosity epoxies, high viscosity epoxies, thinned epoxies, and have never had anything remotely like this happen, in several thousand batches. The thinner in thinned epoxies flashes off mainly before, and soon after the cure, but most low-viscosity epoxies used in laminating are 100% solids -- no thinners at all.

The residue looks like the foam that comes from an exothermed batch of epoxy. The container shown is large enough to promote exotherm. So, perhaps the original casting was done in cool temperatures, and the mix never fully cured. Then it goes into a cabinet, and things warm up, causing an exotherm. Often, when this happens the cup containing the epoxy partially melts, and then there is also a very large volume of epoxy foam: 3-10 times as much as you started with. Typically the mass remains the same. So who got rid of the evidence?

Sabotage? Joke? This is not something that happens to epoxy, and even thinned epoxies have very small volumes of thinner (around 10% not 96%.) If there has been no sabotage, then the "epoxy" was not really epoxy.

The differences between casting epoxy (which cannot shrink for obvious customer satisfaction reasons) and laminating epoxy (which also does not shrink in any measurable sense -- unlike polyester resin which can shrink to 98% of its original volume (99.3% each, length, width, thickness) are very very slight, and have nothing to do with cured volume over time.

Sabotage? It wasn't epoxy? Somebody mixed something else together, etc. Nothing like this ever happens to real epoxy.

Order a small amount for further tests from another reputable company, see what happens with their products.......

By the way, an accurate scale could be used to measure the weight of a test object and see if its getting lighter, only a few days after the test starts, or not.

Naturally the test should run over the same length of time of course as before for accuracy.

Hi,

Kramarat may be right, but there is another possibility. The epoxy may have been eaten by a mouse or bugs while in the cupboard. Do you have either?

There is something I don't understand. Why would you mix the epoxy and hardener and not use it for anything? Once it hardens it can't be used. Am I right?

Why do you have photographs of before and after against the same background? It is as if you were running a "test." But what would the test be for?

One could have months of spare time, and not come up with such a test. Cured epoxy is about as unlikely to change as a rock of quarts. It is as if you are saying that you put a sheet of Lexan in a cabinet, and it disappeared. Mice, insects, bacteria, mold? All possibilities, but all incredibly unlikely.

Did you personally perform the test?

Hi friends

Thank you for the different comments, explanations and remarks

The matter enunciated below would explain the real intentions and sequences of the Tests:

(i). It is a practice to Cast any material and see how it cures, as soon as any new material batch of Epoxy is received

(ii) The said casting is done using a PP container that has less than 100 ml volume

(iii) In this case the Resin + Hardener batch was received on April 15th and the Test piece casting was made on April 17

(iv) Two test samples were made ... One to test Casting quality; and the other to test Glass Fiber Composite quality

(v) While the casting was "observed" for cure and hardness, the Fiberglass material was also tested for some mechanical properties

(vi) Having made these observations we had ordered for a certain quanta of Resin + Hardener for our Production work

(vii) During the time the Production works were under way,the "samples" were kept inside a cupboard that is normally kept closed and locked. The Cast sample was inside the original Plastic container itself

(viii) The cup board was not opened for about 45 days from the original date of casting. But, when the same was opened for observation again, the "problem" as noted in the Original presentation was noted .. with disbelief and awe!!!

The Photos were taken inside my Office and this is a usual procedure (for record purposes)

What reasonable explanation can there be other than sabotage, a joke, etc? Nothing else comes remotely close to "making sense". Perhaps someone with access to the cabinet popped the epoxy out, (which can usually be easily done, because it does not bond well to PP or PE) giving the cup it current clean appearance. Then the cup was used to hold whatever is in it now.

Have the residue analyzed.

Sabotage and "jokes" are ruled out due to the following reasons:

(i). This is a College project and the students involved are selected on strict selection process

(ii) The "leader" student holds the keys and control of all Tools, Materials. And, in the case of the "cupboard" in which the Epoxy samples were kept, no body else has access to the same (except the "leader" and self)

(iii) It is very clear from the "cleanliness" of the PP container that the same had not been handled much

(iv) The original casting was solidified within 24 hrs and it was easily removed from the container for further close observations such as smell, nail scratch hardness and also water immersion. All these tests were continued for about a couple of days and after noting satisfactory condition (except smell), the material was placed in the cupboard ... the casting having been placed inside the PP container again... [There was a mild smell of some form of Phenol/ Cresol, which was there in the main Resin too. But this was not considered as having any long term impact]

The final "residue" has a very distinct Cresol smell (something like the Branded Lotion "DETTOL"

http://www.silhouettes1979.com/Other%20T&T%20%20-%20Dettol.jpg.. and incidentally, careful smell test of the original resin also gives off such an odor or very close to that

The Manufacturer stands by the statement that they have not added any volatiles; and that the problem might have been due to"improper mixing"

Th question again is: Granting that the mixing was improper, would "free phenol/ cresol" dissolve the cured part of epoxy material?

It is noted from literature that Cresols and Phenols do attack epoxy

I think you must stop production until you are certain that your resin is OK. In very bad mixes of epoxy, the cured part is too soft (generally from excess hardener in most systems) or too hard (brittle). It does not disappear, and typically the mass remains precisely the same.

Your points for ruling out sabotage seem to support rather than dismiss the possibility.

(i). This is a College project and the students involved are selected on strict selection process

Many college students are mischievous (and the brightest are often most mischievous). The portion of the brain which deals with evaluating risk is not fully developed until age 25. I can remember many engineering school pranks.

(ii) The "leader" student holds the keys and control of all Tools, Materials. And, in the case of the "cupboard" in which the Epoxy samples were kept, no body else has access to the same (except the "leader" and self)

Unless you have very unusual security precautions in place for such a project, it would be relatively easy for another team member to gain access to the cupboard keys. Bill Clinton and John F Kennedy were both excellent students and natural leaders, but neither had a particularly good moral compass regarding their relationships with women. Kennedy entertained prostitutes in the White House, and Clinton is famous for many dalliances. There is no correlation between being "smart" or a "leader" and being honest, etc. The traits are completely independent. By the way: Is the cupboard steel and rodent proof?

(iii) It is very clear from the "cleanliness" of the PP container that the same had not been handled much

I'm not sure what your point is here. To sabotage or play a joke or prank, the container would not need to be handled in any way that could be detected even by a good crime lab: the latex or nitrile gloves that you wear when using epoxy (and which I sure you have in abundance around your shop, and which detectives wear to avoid contaminating the evidence) will leave no detectable trace on the PP pot. As you know, the epoxy can be removed from the pot without leaving a trace -- it "pops" right out, unless the pot been used many time and is scratched. Open the cabinet, remove the real test casting, put in some foam from an exotherm, close the cabinet: not trace.

Problems:
1. A natural exotherm (which is almost impossibly unlikely, given that you tested the casting, and it appeared well-cured) would leave a very large volume of foam. Where did it go? Can rodents gain access to the cabinet?

2. What is the mass of the remnants in the cup? My guess is less than 20% of the original. There is no amount of off gassing of anything likely to be in even poor-quality -controlled epoxy to reduce mass by 80%. 3% reduction would be stunning.

Support for Sabotage, prank etc:

Simple to do. Easily produces the observed condition. Students are prone to such behavior. There is a motive: its fun, and it some circles gains the prankster some respect. Requires no long chain of improbable/magic events to explain.
What might be a chemically plausible alternative other scenario that would explain the material working exactly as expected in your lamination test, but strangely in your casting test.

I can't think of anything that comes remotely close being plausible.

Hi K Fry,

I'd really like to know what caused this. I have no experience with the newer, zero VOC epoxies..................all old school stuff.

My GA, wasn't really mine. I called, and talked to the tech dept. at a manufacturer of zero VOC epoxy. My answer was based on his best guess.

I hope we can get to the bottom of it. I agree that that is an excessive amount of shrinkage.................for any epoxy.

G'day pvhramani

If you still have both samples try the following:

1. heat the samples until the give off an odor, they should smell the same.

2. heat the samples until flame and observe the color thereof, they should be same.

3. If not the same, the culprit is what makes the difference.

K_Fry Has concluded correctly IMO that this can only be the result of an exothermic reaction. What you see is the ash of what was original the matter which makes the difference in the flame or smell test, if any is recorded.

That's what I would do and then I would go and see my university and have spectrum analysis done. You seem to be manufacturing something so finding a way to avoid failure in your parts could be costly. Not getting to the bottom of this could harmful to others and cost you an arm and a leg. What are you making if I may ask?

Just my half Rupee worth, Ky.

Good day ky

Thank you for your observations and remarks

It is my intention to first analyze the "problem" and arrive at a logical conclusion before trying anything on the "eaten up" material. In the meanwhile, a few additional Sample tests are being done for further observations and study

It is true that "Not getting to the bottom of this could be harmful to others and cost you an arm and a leg." The materials were ordered for developing a New Composite system to be used in Fishing Boat construction. That being so, we NEED to make sure that the said materials are capable of delivering safe and appropriate results ... and the unprecedented "casting phenomenon" gives "shivers" to us! Incidentally, the Test piece of the Glass-mat Composite did not show any sch weird result!

I didn't find the answer, but what a great explanation of epoxy.

http://epoxy.nilsmalmgren.com/kemi.html

That is a good explanation. The description of reaction time vs temperature is not correct, however, but the graphs are pretty good. A ten degree C increase in temperature roughly doubles the reaction rate. (The article says: "...Arrhenius' law, which states that the reaction speed doubles for each tenth of a degree the temperature is increased.")

This is also in response to your other recent post:

Boat building resins are all low molecular weight, and as a result are not thinned. Whether a good casting of a 100 gram sample can be made in practice depends upon temperature and the nature of the hardener (fast, slow, etc.). With a slow hardener, a casting like the one pictured in the original post can be made without a runaway exotherm occurring. (The reaction is always exothermic, but the term "exotherm" is used by epoxy users to mean an uncontrolled or undesirable reaction rate: the epoxy boils up into a foam, which then hardens, and the container often gets so hot that it warps severely. Even short of that point, is is not uncommon for a batch in a cake decorating bag -- used for making fillets at joints in wooden boats -- to become uncomfortably hot before you have time to squeeze it all out.) After a runaway reaction, if the original sample was 100 grams, the cured mass will be very close to that, and the volume will be many times greater than a normal, clear, hard casting.

Once the cure has progressed to the point that it is pretty hard and cannot be dented easily by fingernail, the likelihood of foaming is essentially 0: the reaction has already occurred. The OP's casting was at that stage, apparently, when placed in the cabinet.

The OP indicates that the epoxy performed as expected with the mat, and performed as expected with the casting, initially. Seriously incorrect mixing ratios do not produce normal properties -- you see problems in both the casting and in the mat. (I have a cup that collects resin and hardener drips from my dispenser pumps. The resulting mix is random, and it stays in there for as much as a year at a time. Nothing bizarre happens, typically it just remains sticky if it does not cure.

It is hard to imagine something that got into the epoxy at the vendor's location that would produce such a result: if there were a large volatile component, then the cure would not have resulted in a good casting and mat.

Virtually any all-solids epoxy can be "post cured" in which you bring the temperature up to 130 - 220 degrees F and cook the laminate for a while. Various properties improve. Even under these elevated temperatures, the epoxy does not do anything visible, like loosing measurable mass.

If the vendor is claiming that incorrect mixing was the cause, it would be interesting to have them mix up a bunch of test batches to see if they can reproduce the symptoms. I can't think of anything that would permit a good initial cure, but then cause any disappearance of mass, let alone such a huge change. If rodents, insects, sabotage, etc have been ruled out, then

I've used epoxy from about 4-5 main vendors, and they all work about the same, with small variations in viscosity, cure time, odor, and final properties -- but not one has appeared to function by magic.

I'd love to see an explanation.

Me too. I wonder if the OP can reproduce the exact same mix and conditions, and retain first hand knowledge that it hasn't been tampered with.

It was fine for an entire week!! Gassing off does sound impossible.

If it actually turns out to be the material, I sure wouldn't want a boat made from it.

I've done some internet searching, and can't find anything remotely similar.

Check this out. Scroll down to the microchip at the bottom. I wonder if there was any nitric acid in the cabinet?

http://azhar-paperpresentation.blogspot.com/2010/04/attacks-on-security-control-system.html

Effect of fuming nitric acid on epoxy:

It is true though, that if this is a college class/university, I could be onto something. We've been concentrating on a possible problem with the epoxy itself. Now I want to know if anything else was stored in that cabinet. If so, what was it, and could it react with cured epoxy?

Seems like a valid avenue to explore.

Now that you mention the cabinet.

I have an old disconnected fridge were I keep my fuels, oils and other chemicals. Just at the entrance of my workshop come studio. In case of fire it would be the first thing out. Although all are in suitable containers some caps, labels show signs of disintegrating. For sure the fumes or some other unknown catalytic reactions.

One culprit I noticed is the break fluid and the transmission fluid don't like standing too close together. I now keep them further apart but don't know why this happens. Chemical osmosis (?) through containers, even when closed?

I bet there was a third chemical involved in OP's case but was maybe discounted as too trivial to make a difference. I better go and check my fridge, haven't looked inside for a while.

I Wonder what this will turn out to be.