NCIS

I have been using West Systems 404 adhesive filler added to my thinned down 30 minute epoxy. It seems to take longer to cure. I like to use the filler when I have any voids to fill so there aren't any air pockets. Does anyone know why it takes longer to cure? Plus even though it's cured it still remains slightly flexible beyond the 24 hour time. In a week or so then it is hard as a rock.

Barry
www.canopyrailsforwarbirds.com

Chip_Mull

My Feedback: (1)

It could be because you are thinning it with Acetone. Always use Alcohol for epoxy, 91% if you can find it as it has less water in it. The 91% is available at all drug stores but you might have to ask the pharmacist for it.

Buckmeister

You can also get denatured alcohol at Home Depot, Lowes or probably any hardware store. It's 100%

arobatx

I've seen the same temporary rubbery result from using denatured alcohol to thin epoxy. I use it along with milled glass fiber as a filler. Admittedly, 20-some years into the hobby...I don't measure my thinner, and I know sometimes I get it perfect, and sometimes I don't, which is obvious by the wait time for full cure.

da Rock

The last can of acetone purchased happened to have printed on the label that a primary purpose of acetone is as epoxy thinner.

When rubbing alcohol is used as thinner, a large amount of the water that is included as an ingredient is trapped when the epoxy cures. Epoxy is thick enough that it takes the water considerable time to migrate to the surface, and the epoxy cures way before that is possible for all the water. The result is a somewhat porous surface and degraded epoxy structure. Not a perfect result. Good enough for gummit work however, if you're not too particular.

Acetone is produced and sold to thin epoxy.

Why are you seeing longer cure times? Most two-part catalytically cured products are affected by thinning. Heat is one of the things that affects the cure time, and anything that modifies the heat would affect the speed of cure. The cure is also a coming together of the molecules and having to bring another molecule into the combination would also affect it.

I noticed the West Systems epoxy I've got takes longer than 30 minutes without thinning. Also, the LHS 30 minute takes less. My guess is just different stuff does differently.

Epoxy is used in boating often because it is more flexible than fibreglass and lives longer under the pounding. I'd guess lots of epoxies don't ever wind up being completely rigid.

Tmoth4

My Feedback: (1)

It's most likely the 30 minute epoxy.

If you use West's own epoxy, that won't be a problem. I get their resin in the pump cans, and use fast hardener for most things. (For casting parts in molds I use the slow hardener.) I've thinned West epoxy with acetone, laquer thinner, and denatured alcohol and it always hardens. Their resin is thin enough, though, that you shouldn't have to thin it any more.

Jim

spaceworm

Quote in part:
"Epoxy is used in boating often because it is more flexible than fibreglass and lives longer under the pounding. I'd guess lots of epoxies don't ever wind up being completely rigid."


FYI:
Fibreglass is the spun glass that is woven or made into matt form to act as a reinforcement for the Epoxy OR Polyester Resin used in the laminate. The resulting laminate is fiberglass-epoxy or fibreglass-polyester laminate. Other fibers and resins are also used.

Epoxy is stronger than polyester, but is typically NOT used except in high strength demand (read expensive) boat applications.

Epoxy to hardner ratio is typically one to one or close. Polyester resin hardner is typically 1 drop per ounce or so.

Denatured alcohol is ethanol "denatured" with methanol (poisonous) or benzene (caregenic) so it is not drinkable.

Rubbing alcohol is isopropol alcohol and is avaiable in 51 percent (or so) and also 91 percent strength. The 91 percent has the least water and preferable for thinning epoxy resins.

No alcohol is 100 percent, there is always some water or other contaminant.

da Rock

Sorry, but I used the terminology the boat dealers in the area use. When the white water community saw the first epoxy kayaks (another term that's often misused but understood) they basically started calling the earlier ones "fiberglass". The epoxy kayaks were more flexible, and that was said to be a result of using epoxy. A guy my wife worked for raced offshore powerboats and described them as using epoxy instead of polyester resin (he called it "glass") so they'd last more than a year due to the slightly greater flexibility.

Truth is, a lot of the flexibility comes from the other fabrics used. However, the polyester resin available to me in the past for this hobby has shown itself to be less flexible than the epoxies encountered. Cracking being the most preceived symptom.

spaceworm

Totally agree. There are a lot more engineering options available in epoxy resin systems. Some boats are layed up using vinylester resin and glass or Kevlar fabric or matt.

NCIS

I don't have that problem with my 77' Hatteras Motor Yacht. It goes to slow to pound waves!!! Thanks for the comments but the Acetone I'm using says it's specifically for thinning Fiberglass Resin and Epoxy. So I will continue to use it! This time I added a slight bit more hardner and when I checked it this morning it was as hard as a rock in epoxy terms anyway.

Barry

Foxman

You cannot say epoxies are 1 to 1 mix ratio.
They are all different and you must adhere exactly to the manufacturers mixing ratio. Most will have a ratio like 38 parts hardener to 100 parts resin. This does not apply to all resins.
Check as to whether it is by weight or volume.
I have never seen 1 to 1 except with 5 minute epoxy. Maybe someone makes one like this but I have never seen it.
You must also mix it very well as it will not harden properly if you do not.
Do not mix acetone with epoxy. Acetone is for polyester.
Use a thin resin instead of attempting to thin it. If you must thin it then I have used methanol before and this worked ok.
Mix small quantiities and use a large dish as it can heat up very quickly if it is used in a tall cup.
Jim

Scotsman

Acetone is not only for polyester, it will thin epoxy just fine, is made for thinig epoxy as well as polyester resins and evaporates out better than acohol without leaving any water behind. Warming the resins will also help thin them, but there wil be a shortened working time. Thinning finishing resins can help when working with the very light weight finishing cloths.

spaceworm

[quote]ORIGINAL: Foxman

"You cannot say epoxies are 1 to 1 mix ratio.
They are all different and you must adhere exactly to the manufacturers mixing ratio. Most will have a ratio like 38 parts hardener to 100 parts resin. This does not apply to all resins. Check as to whether it is by weight or volume.
I have never seen 1 to 1 except with 5 minute epoxy. Maybe someone makes one like this but I have never seen it."

ALL of the epoxies I have used over the past 40 years have been 1:1 ratio, with the recent (to me) exception of some of the West System epoxies. However, note that I said: Epoxy to hardner ratio is typically one to one or close.

"You must also mix it very well as it will not harden properly if you do not."

I think that is a given. You also have to have the ambient temperature above the cure temp range of the particular epoxy.

"Do not mix acetone with epoxy. Acetone is for polyester."

Actually, isopropol alchohol has been in my experience the thinner of choice, NOT acetone and NOT methanol. Acetone is an aromatic hydrocarbon and there is a difference between isopropol and methy alcohol (methanol). Alcohols are not aromatic hydrocarbons. However, as you have read in this thread, many have mixed almost anything and eventually gotten a cure.

"Use a thin resin instead of attempting to thin it. If you must thin it then I have used methanol before and this worked ok"

In other words, don't thin it unless you need to thin it? You can also heat up the resin before adding the hardner to thin it, but then it will cure faster (see below)

"Mix small quantiities and use a large dish as it can heat up very quickly if it is used in a tall cup."

Yes, it is an exothermic reaction, you can if you wish speed up the cure by heating the unmixed resin and/or the "glued" assembly. Some resins will not cure at room temperature, by design, and must be autoclaved to cure them.

Sincerely,

Richard

da Rock

Local hobby shops all over the United States have many, many, many different brands and cure-times that come in equal volume bottles. Most epoxies here are equal mix in the non-commercial packaging.

That's not actually true of the acetone sold around here. I was just in Lowe's Home Improvement and they've got more than 3 brands of acetone. I mention 3 brands, because I looked at 3 not an hour ago (to see if they listed any real info in the small print) and looked at them because they had the most prominent wording on the can stating they were for use with epoxy and polyester. I'd say the thing they had in common that caught my eye was the "for thinning epoxy" idea.

BTW, none of them mentioned that acetone is a great "one wipe" cleaner for removing CA drips and runs off Monokote, but then they used up a lot of space on the labels advertising the use to thin epoxy.

Foxman

Ok I used to live in England and I never saw industrial resin which mixed at 1 to 1 but it must be different in the United States.
I don't buy resin for my work from Hobby shops but maybe the manufacturers make special resin for the hobby people so it's easier for them to mix.
I live in Thailand now where it is always hot and the resin is naturally quite thin due to the heat. We have to use very slow hardener.
Here in Thailand we have 2 types that I use and one mixes at 27 to 100 and the other at 38 to 100 by weight.
Regarding using Acetone, again I must be wrong about the USA. If I buy Acetone here and try to clean the brushes they go instantly stiff and will not clean. Cellulose thinners cleans them ok.
Mixing acetone in with the resin (in Thailand) stops it going hard and it stays rubbery forever. There must be different types of acetone so I can't comment because I don't know what you guys have over there. Are you saying you have 3 types?
Methanol worked as a thinner for me when I was in the UK but I can't buy it here. Don't need to thin here anyway, you just need to make small quantities and get a move on.
Again I would tell anyone who is using resin to do it to the manufacturers mixing instructions and don't vary it whatever the ratio.
I went to a full size aircraft factory in the UK and they told me they cannot use resin more than 3 months old and they must mix it exactly as varying the mix ratio leaves it weaker.
Ok you guys now you can shoot me down and tell me I am wrong about everything, that usually happens on RCU.
,

da Rock

We're actually talking about any glue you can buy anywhere, not just industrial resin. In our LHSs, home improvement, and just about everywhere you can buy epoxy, you will find packaging for 1:1 mixes in the US. The packaging was created for the "average customer" who wanted epoxy glue to fix stuff around the house.

We've got epoxy and lots of other glues. Our acetone usually says straight up that it's for thinning epoxy/polyester right on the can. It's my understanding that there are a number of different types of epoxy, but it would be a surprise to see any one of them describe the type they are on the labels. The labels do not mention "type". We most certainly have polyester resin and epoxy resin, but don't know of a third type. And no different types of each of those mentioned.[/quote]

There is a good probability that a/c manufacturing in the UK has to follow rules/laws that insure safe construction, just as mfg'ing in the US must follow the FAA rules. Problem we have with home or hobby glue use is the same "fresh glue" rules don't apply and a lot of problems we have/discuss can come from using over-aged products.

Hey, shooting people down usually isn't the goal. Getting correct information out (that works no matter where you live) is the hope. So far, we've combined to provide a LOT more good info that covers more of the world than usual. Now, we need someone from Scandinavia to chime in and tell us how they deal with epoxy during their winters, and what they can buy in their stores. We'll pretty much have it all stuck down then.

NCIS

I just buy extra strength ACE Hardware brand Acetone and it has always worked great for thinning epoxy and Z-poxy finishing resin for glassing. I have worked with fiberglass since I was 10 yrs. old and 47 years of it I have always thinned my West Systems resin and hardner with acetone. It helps to penetrate the balsa for wood models and it makes rough sanded fiberglass boat repairs much stronger. I rough up the boats surface after Ive gone through the gelcoat and then add new glass. I blend it in and then shoot it with matching gelcoat. Buff it to blend the surface color and shine and it's done.

Barry

I think I opened a can of worms with this thread because it seems everyone does it different!

Foxman

Ok I just looked on the West Systems web site.
The mixing ratios are 3 to 1 and 5 to 1 for different resins. No mention of 1 to 1.
There is also no mention of thinning with anything. I have emailed them and asked them about acetone. I will get back when I have an answer.
I would doubt any resin manufacturer would want customers thinning their products.
The thinner would maybe come out of a thin lay up but could be trapped in a thicker one. This would weaken the structure.
I know full size aircraft manufacturers would NEVER thin their resin and they would NEVER "add a bit more hardener".
I can't see Burt Rutan throwing a bit of acetone in with his mix, can you?
I would think full size aircraft manufacturers all over the world have to follow the strictest rules, not just UK based ones?
NCIS why have you asked us this question? You have been doing it for 47 years so you are probably the most experienced guy here.
If you get a soft product it is because you mixed it wrong. This includes wrong mixing ratios, lack of stirring and adding thinners.
Slow setting is usually determined by the resin temperature.
Jim Fox

Foxman

Just to answer your question about slow setting time when you mix in filler.
1 you must mix the resin first and then add the filler. Never put all 3 together and then mix.
2 It will take a little longer to set because it will not warm up so much due to the added bulk of the filler. So a warmer room would do it.
3 Never mix the resin with a screwdriver or similar, you should always use a paddle type stirrer or similar. Round bars are useless.
Jim Fox

tony-howard

My Feedback: (224)

Here's the link to what West Systems says about thinning their epoxy:

http://www.epoxyworks.com/14/ThinningEpoxy.html

HTH

da Rock

Now there is a good bit of information.

It is interesting that they do not provide a line on most of their charts to show the un-thinned epoxy's characteristics, only the 3 samples that they thinned. All that good work and information and it leaves out the most important detail. Interesting.

One concept they repeat that seems worth repeating is that thinning is not a good idea for structural use. Never having wanted to thin epoxy that was going to be used as a glue, it occurred to me that issue might be the basis of this continuing argument. After reading their thinning info, it comes to mind that it would be nice if every epoxy supplier would provide better, more complete information.

BTW, I was in the best LHS in the area yesterday. They didn't sell West Systems any more, but sell many, many other brands. I quit counting after 10 brands. And every one of them were 1:1 mix. Every "type/cure time" came in equal size bottles or tubes. And none mention thinning on their paltry instructions.

NCIS

I wanted your opinions and also my eperience has mostly been with boats and fiberglass resins not Great Planes 30 minute epoxy. I thought this was where to ask a question if you wanted answers. I'm sorry if I broke your rules.

Barry

frets24

My Feedback: (15)

classic example of how ineffective the written word is compared to the spoken word.
When I first read this, I read it as a compliment to Barry's years of expertise and a reference to the idea that alot of folks have good faith in posts after the NCIS header.
Don't feel bad Barry, I've been building for a long time too, and I still learn new trick, tips, and techniques here all the time. I'm just really grateful that we have this forum and we can share the wealth of info amongst the collective group.

by the way, I'm a 1/1 epoxy user user and staunch nothing but acetone thinner type...never had a problem with it hardening (well, sometimes it does take a day....... or two......... on the 30 minute stuff.....)

Foxman

Hi Tony, that West system article is very good, thanks for putting me onto it.
It says adding 5% thinner reduces strength by 35 %, and there is more shrinkage, so thinning is not recommended.
Everyone should read it and it appears I was wrong about using acetone, but read my next bit.
We tried a test here 2 days ago. I added acetone to a normal layup and it seemed to go off ok if a bit more slowly and it was more flexible but that may go with time. I didn't do a strength test though.
What was interesting though was that we put some into a sealed plastic bag and put a vacuum on it to remove the air, it didn't go hard at all even after 2 days.
NCIS, sorry if I said something wrong to you, not sure what you mean by "broke your rules". I have no rules, I'm English.
Jim Fox

da Rock

Good thing about this discussion going on and on..............

It's been brought out that thinning epoxy that is used for structural is not recommended. But then, how many modelers thin epoxy when they're using it to glue stuff together.

Most thinning is done when fuelproofing a tank area or a firewall and are going to paint it on/in, and that's not really a structural job.

Seems like the discussion has been thorough and worthwhile.