Please help me choose between these epoxies - need high(ish) Tg at RT cure

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#1

Hi!
I’m making this thread because I need some help choosing an epoxy. Based on old threads from the forum, I’ve gathered that you can’t expect to get a Tg of above 200F without doing a post cure - that’s fine though. A Tg approaching 200F will do great for me, especially if it means I don’t need to bake it and I can demold the part within 24 hours at room temperature. I was using a polyester before (S249) but can’t anymore because of the fumes, and more importantly, because I was getting pretty serious print through. So I’d like to switch to an epoxy!

What I’m doing. I’m making a part that will be exposed to the temperature of the interior of a car. So it can get pretty hot in a bad situation, but not much above 150F. I’d like to also be able to do an in mold coating spray of clear, so if you can recommend an epoxy compatible with a urethane clear (or maybe that Sherwin Williams product that so many appear to be a fan of) that’d be great.

Anyways, here is what I’ve come up with. Let me know what you think of them if you’ve used them before. If you have recommendations or favorites that I haven’t listed, PLEASE let me know and it’d also be great to know where you buy them from. I understand that at this premium grade of epoxies large orders are necessary, but that might be alright in my case.

Note that I’m using these with carbon fiber and cosmetics are very important, so I need something that is as close to clear as possible.

  • Huntsman Ardalite 8601 or 8602 - RT cure and a Tg of 164. Not great, but better than the US Composites 635 that I’d currently have to rely on. I understand that their higher 860x products have better Tgs with a cure schedule, I think I saw one that can sustain high temps with just a 150F cure.

  • Freeman 690 - the tech specs said Deflection temperature is 180F - not really sure what a deflection temperature is, can someone clear that up for me?

  • Adtech or Cass? EL-300 - Deflection temp (again, ?) of 232F. They say it’s a “clear light amber” but I guess that’s just their way of saying it’s not polyester clear but still pretty clear, or at least hopefully that’s what they mean. Any recs on their EL350 and EL360 are also welcome

  • Gurit Ampreg 21 - Looks fantastic, but of course it wouldn’t be available in the US -__- , or at least I couldn’t find any after a quick google search. If yall know where to find some please let me know. So really, if there is anything comparable to this available stateside, that’d be great!

Finally, I couldn’t find the tech specs on Miapoxy 100, does that have a good Tg?

Thanks in advance for the help!

Chetan

Edit: forgot to mention, ‘strength’ isn’t a primary requirement. While it’s great to have, the characteristics I listed above are more important to me.

#2

Gurit Ampreg22 is available in the us and is very good resin. Also if you are going to infuse I would suggest Gurit Prime20ULV system

#3

The print through may be caused from maybe demoulding to soon. I know if I demould at RT after 24 hours I get much more print through than if I demould after 48 hours. I use Rhino 1401-21 resin and Rhino 4101-21 hardener.

#4

I use ampreg 21 mainly, but it’s Tg isn’t that high without postcure. Ampreg 22 isn’t very good without postcure either, I wouldn’t use 22 without postcure.

#5

High Tg without postcure? Forget it. For cars in your situation, 150F is the bare minimum, 200F would suit the job better. When using epoxy, learn to live with postcure cycles. Build a simple oven, and you will like it every time you make something. Also speeds up cure time.

#6

:confused: I guess I’ll look into building an oven. I called the Gurit US offices and one of their reps recommended the SP115. TG of 150F after 4 weeks with RT cure, that goes up to 183F with a 50C 16 hour cure. So a low temp oven cure which should be doable with a room size enclosure and simple heating elements. I think I’m going to order about a gallon of it to try it out directly from them. It’s about $130 US for a gallon.

Has anyone ever used this? He recommended it because it has great clarity and built in UV resistance (I’ll of course be clearing it anyways, but some extra UV resistance doesn’t hurt!)

#7

SP115 is a nice resin for cosmetic parts. It’s quite fast, so work fast :slight_smile: Don’t know about the UV resistance, but my experience with those kind of “surf” resins is that they will yellow anyway(on the outside parts of cars).

#8

Yes, the pot life and gel time don’t look too great :confused: tech sheet says, at 77F, 23 minute pot life and 35 minute gel. Quite fast indeed. The gel times of the Ampreg 22 with the standard hardener meant I could wet lay maybe 2 yards of 50" carbon in one go and use it up - doesn’t look like that’ll be possible with the SP115

What is the clarity of the Ampreg 22 like? Is it not suitable for composite parts at all? I only decided to experiment with the SP115 because I was recommended it by the sales rep. I’m not planning on using the epoxy as a gel coat as well, that will be taken care of by an IMC of urethane clear (followed by later out of mold coats as well, of course)

#9

it’s good enough, there is a carbon longboard I made with ampreg 21 on the forum, which is just a little clearer than ampreg 22

#10

Great, that still looks more than clear enough. Thanks for sending me that link. It looks like right now I’m torn between the Ampreg 21 and SP115. Guess I’ll have to try both? I tried ordering direct from Gurit USA on Friday but no one was answering their phone on Friday from midday onwards so I’ll try again on Monday.

Your board looks great!

#11

Bit the bullet and bought some Sp115 directly from Gurit today. 400 for Resin, 160 for hardener, 75 for FedEx freight shipping - that’s for 20 kg resin and 6.6 kg hardener. :0 I’ll let you guys know how it is when I get it

#12

hi you will not regret buying it, i’m currently using it for wet layups and so far so good :slight_smile: do let us know how it goes and share some pics

#13

The SP115 actually came in yesterday! Didn’t ship via fedex, had to come by freight (R+L carriers). I made a part today and I really like its cure time. It is also very thin and wets out very easily. I’m wet laying and then bagging my project, which is not normal for SP115 per their data sheet, but it seems to work reasonably well.

I didn’t degas on this first run and still experienced some pinholes; I was hoping I could get away with degassing in a production scenario so I wanted to try it out. I’ll do a run tomorrow with degassing.

I really like its setting characteristics. Very reasonable pot time for how quickly it cures (or at least how quickly its out of mold time is, per the data sheet). Another reason I didn’t degas is because I wanted to get a good handle on pot life - since I now know that I have a decent amount of time I’m not as nervous about doing it.

Only problem I’ve had with it so far is that the peel ply and breather were REALLY REALLY hard to remove from my part. Not sure if it’s a fluke from this first piece (maybe a fold got trapped within the part), but man was getting those consumables off a work out…

I’ll post pics in about two weeks once my website is ready and the project launches :smiley:

#14

Aaaand it wasn’t a fluke… the part I made yesterday is also very hard (ie I still haven’t been able to get it off) to remove. I guess this stuff wets out easily enough to be over saturated to the point where the breather material becomes incredibly soaked - and impossible to remove :confused: . For 1 sq ft of material I ended up using about 200 ml of mixed resin though, which is about 70 ml more than I was with my other system so maybe I over saturated it. It seems to soak it up though… I guess this is why people don’t like wet layups!

On the bright side, the frekote 770 I bought worked like a charm on ABS plastic

#15

do you use a perforated film?

#16

No I’m using a fabric peel and ply right now and then there is polyester breather behind it. I’m not positive about what type of material it is, but I got it from fiberglass supply and they call it econo-ply J, 1.6oz

#17

pull it apart, there should be a perforated film in there. If not, you’ll suck out too much resin, and the breather is laminated on your peelply, and will be a pain in the ass to remove. And probably in other parts of your body too when you got it all out.