Would like epoxy advice

The Rocketry Forum

Help Support The Rocketry Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

REK

Well-Known Member
TRF Sponsor
Joined
Feb 21, 2012
Messages
3,090
Reaction score
109
Location
El Paso, Texas
Hey guys, I probably already know the answer to this, but I just want to make sure I am right. My epoxy tends to get really sticky after application to the fabric. I also notice on the surface of the epoxy it forms like a dried layer, much like the ones you find in paint on the top surface.

My assumption is that the weather is still too cold and its making it really thick. If its not the cold weather than hopefully someone can help me on what it is and how to avoid it.

Your advice is appreciated.
 
You mentioned fabric. What fabric are you applying the epoxy to?
And of course what type of epoxy are you using? Are you doing this outside in your
garage or inside your home?
 
You mentioned fabric. What fabric are you applying the epoxy to?
And of course what type of epoxy are you using? Are you doing this outside in your
garage or inside your home?

Any kind of fabric, glass, carbon, etc. I do this inside the house. I am using Aeropoxy.
 
What Aeropoxy hardener are you using?
What temperatures are you applying it under?
Temperatures affect the cure time.


JD

I've been using their new hardener PR3663.

Like I mentioned on my first post its cold, as in 60 degrees at the most.
 
It's not a new hardener but I couldn't find the instructions on their website, but a quick google search yielded this set of instructions.

View attachment AEROPOXY PR2032 Bulletin w-4 Hardeners Ph3663 24Jun08.pdf

The MINIMUM temperature for use is 72 F and you are way below that, so assuming that you properly weighed and mixed the 2 components, the problem is the temperature. About all you can do is to heat soak the part @~100F-150F for a day and hope the cure completes.

Bob
 
PTM&W reference cure time to 77 deg F (25 deg C). They give a rule of thumb of double the cure time for each 10 deg. below 25 deg. C, and half the cure time for each 10 deg. above 25 deg. C. I've never seen anything from them that specifies a minimum cure temperature.

https://www.ptm-w.com/index.asp?pgid=49
 
Okay let me rephrase my situation, because you guys are assuming this is something with the cure.

My issue is the epoxy getting sticky while I am still in the pot life stage. The epoxy gets all sticky while I am laminating, not after cure.

It does not even take long for the epoxy to do this. Shortly after pouring it into an aluminum baking tray the epoxy will get all sticky and thick.
 
Okay let me rephrase my situation, because you guys are assuming this is something with the cure.

My issue is the epoxy getting sticky while I am still in the pot life stage. The epoxy gets all sticky while I am laminating, not after cure.

It does not even take long for the epoxy to do this. Shortly after pouring it into an aluminum baking tray the epoxy will get all sticky and thick.

Not sure what you mean by sticky. Are you talking about viscosity? Your pot life is the point at which viscosity doubles it will not remain at the initial viscosity until pot life. I have noticed the skinning you are talking about with some other PTMW products it doesn't seem to affect anything.
 
Not sure what you mean by sticky. Are you talking about viscosity? Your pot life is the point at which viscosity doubles it will not remain at the initial viscosity until pot life. I have noticed the skinning you are talking about with some other PTMW products it doesn't seem to affect anything.

The only part it effects is the annoying inability to laminate heavier fabrics as easily.

Yes you can say the viscosity gets really thick and does not wet out the fabrics as easily.

By sticky I mean that the epoxy gets really tacky quickly, as if it were hardening instantly.
 
Cure time aside, it might just be too cold to work with epoxy. I remember doing some cold weather builds a while back and I had to heat my epoxy a bit to get it out of the bottles. This was in my garage at sub 50 degrees... very cold for my neck of the woods.

Jerome :)
 
Did you actually measure the temperature in your attic and more importantly the temperature of the epoxy and the fabric? If not, it's really hard to determine how thick the mixed might have been.

Viscosity (thickness or stickiness) increases as the temperature decreases for virtually all materials, and furthermore in mixed epoxies, the viscosity increase with time as the resin reacts with the hardener(aka linker). Thicker resins are harder to mix, and will take longer to mix completely at lower temperatures, and colder resins will take much longer to cure.

The viscosity of your resin PR2032 is listed as 1650 cps @ 77 F (25 C). The viscosity of your hardener PH3663 is listed as 35 cps @ 77 F. The initial mixed viscosity is listed as 440 cps @ 77 F. If the temperature of your materials were actually 59 F (15 C) then your mixed viscosity could be as much as 2.6 times thicker or ~1150 cps which is higher than the viscosities of PR2032 with PH3630, PH3660 or PH3665 when mixed @ 77 F. Using a thicker mixture would make it more difficult to wet out a fabric and the mixed resin would feel sticker than a warmer mixture.

Your experience illustrates why it is so important to follow the manufacturer's instructions when you use professional epoxies. You simply will not get the results you expect to obtain if you don't. You can to try to save your composite by heat curing it. Make or find a box that is longer than the item and several inches wider and taller than your piece and flow warm air through the box. If you have hot air heat, place the box with the composite in front of the hot air register and allow the air to flow through the box for a day or so. If you have hot water heat, place the box on top of the radiator for a day or so. This should cure the resin. If the resin was not completely mixed with the hardener, there isn't anything to do but do it over.

Good luck.

Bob
 
I've been using their new hardener PR3663.

Like I mentioned on my first post its cold, as in 60 degrees at the most.

You need a curing oven. A simple box made from foil backed foam and some lights should get you up to the 90's for cure.
 
How deep is the epoxy in this baking tray?
Are you sure you have the 3663 and not the 3630?


JD

Okay let me rephrase my situation, because you guys are assuming this is something with the cure.

My issue is the epoxy getting sticky while I am still in the pot life stage. The epoxy gets all sticky while I am laminating, not after cure.

It does not even take long for the epoxy to do this. Shortly after pouring it into an aluminum baking tray the epoxy will get all sticky and thick.
 
Did you actually measure the temperature in your attic and more importantly the temperature of the epoxy and the fabric? If not, it's really hard to determine how thick the mixed might have been.

Viscosity (thickness or stickiness) increases as the temperature decreases for virtually all materials, and furthermore in mixed epoxies, the viscosity increase with time as the resin reacts with the hardener(aka linker). Thicker resins are harder to mix, and will take longer to mix completely at lower temperatures, and colder resins will take much longer to cure.

The viscosity of your resin PR2032 is listed as 1650 cps @ 77 F (25 C). The viscosity of your hardener PH3663 is listed as 35 cps @ 77 F. The initial mixed viscosity is listed as 440 cps @ 77 F. If the temperature of your materials were actually 59 F (15 C) then your mixed viscosity could be as much as 2.6 times thicker or ~1150 cps which is higher than the viscosities of PR2032 with PH3630, PH3660 or PH3665 when mixed @ 77 F. Using a thicker mixture would make it more difficult to wet out a fabric and the mixed resin would feel sticker than a warmer mixture.

Your experience illustrates why it is so important to follow the manufacturer's instructions when you use professional epoxies. You simply will not get the results you expect to obtain if you don't. You can to try to save your composite by heat curing it. Make or find a box that is longer than the item and several inches wider and taller than your piece and flow warm air through the box. If you have hot air heat, place the box with the composite in front of the hot air register and allow the air to flow through the box for a day or so. If you have hot water heat, place the box on top of the radiator for a day or so. This should cure the resin. If the resin was not completely mixed with the hardener, there isn't anything to do but do it over.

Good luck.

Bob

I will have to wait for a warm week around the upper 70's to see if it does have to do with the cold temperatures. Right now this whole week is around the upper 60's.

Thank you Bob
 
Really, I've had the opposite experience with the 3660 60 minute hardener. I think almost every Aeropoxy job I've done has been in cold months in the garage or basement , with ambient temps. in the 50s or low 60s. It gives me 2-3 times the normal pot life, and I've never had any problems with the mixture being too thick. I move the layup to a warmer spot to cure. I have tried the 3660 with ambient temps in the 70s and it just is not enough working time for me and the two hour 3665 requires over 100 deg. temperatures to gel hard, so I've never tried it.

Are you sure your mix ratios are accurate? The PH3663 is 100:25, or 4:1 by weight, so a 25 gram batch would be 20 grams resin, 5 grams hardener. Not questioning your math, but it sounds like too much hardener, or maybe you have the 30 minute hardener by mistake.
 
I had the same problem with my aeropoxy, I thought that the harder went bad, it was so thick I had to use a dowel to get some out of the can, since I have read threw this thread it make sense that the temp. would affect the viscosity of the epoxy, I'll have to wait for warmer weather to continue building rockets, or find a way to warm up the cans of epoxy.
 
I had the same problem with my aeropoxy, I thought that the harder went bad, it was so thick I had to use a dowel to get some out of the can, since I have read threw this thread it make sense that the temp. would affect the viscosity of the epoxy, I'll have to wait for warmer weather to continue building rockets, or find a way to warm up the cans of epoxy.

Warming epoxy is pretty easy. Bucket of warm water, insert cans into bucket, wait 10-15 minutes.

Ultimately though you want the room to be warmer for the epoxy to cure properly. Also, a simple oven will help.
 
Really, I've had the opposite experience with the 3660 60 minute hardener. I think almost every Aeropoxy job I've done has been in cold months in the garage or basement , with ambient temps. in the 50s or low 60s. It gives me 2-3 times the normal pot life, and I've never had any problems with the mixture being too thick. I move the layup to a warmer spot to cure. I have tried the 3660 with ambient temps in the 70s and it just is not enough working time for me and the two hour 3665 requires over 100 deg. temperatures to gel hard, so I've never tried it.

Are you sure your mix ratios are accurate? The PH3663 is 100:25, or 4:1 by weight, so a 25 gram batch would be 20 grams resin, 5 grams hardener. Not questioning your math, but it sounds like too much hardener, or maybe you have the 30 minute hardener by mistake.

No I have the 3663. I used to experience what you said, but all of a sudden it just started doing that skinning thing. Perhaps it may have to do with the humidity.

There are times where it wont do it and times where it will
 
Howdy guys, yet another epoxy question. Was giving a tube a coat of epoxy and epoxy was frozen. In the long run I heated up the epoxy until it turned crystal clear. I thought whats the worse that can happen if I add the hardener? I added the hardener and shortly after like 45 minutes or so this happened.

ImageUploadedByRocketry Forum1426906289.443287.jpg

The epoxy melted the cup, gelled hard, and of course was smoking away. What is the maxium temperature that I can heat the resin up to so this doesnt happen to me again?
 
If I was having this many problems with a brand of Epoxy, I'de try a different brand.
 
If I was having this many problems with a brand of Epoxy, I'de try a different brand.

This is actually a first time this happens. The epoxy already came frozen since the source is still under cold weather. I got a bucket of hot water and the epoxy was I guess pretty hot that 45 minutes later after applying hardener made the epoxy go super speed in the cure process.

I actually like this brand. Its wet out characteristics and especially the odor are awesome.
 
Back
Top