[lgalla]

Wow Cameron you sure have a lot of energy,You must be one of the younger guys.I am a bit slow at my age,so it takes more time to sink in.
Sandi's resin is a bit confusing to me as it has a potlife of 400 minutes.Never heard or such a long potlife and 10hr cure.
I am supprised US Composites use Epotuff 606,as Aliphatic polyamide curing agents are generally premium products,not found in $30/gal epoxy.Bargoon??
Assumptions on resin cannot be made as there is thousands of formulations.
Basically epoxy hardners and resins may be two different manfactures.The formulators put it together in an end user package.Your epoxy resin may be from Dow and your hardner from richold or India.
We should compare specs from the formulators to see which is better.After US Composites at $30,we go to Epoxy.com at $45 to West epoxy,East epoxy,System 3,Mas epoxy etc in the $100/gal range.
Better??because of price?I don't know,but being below having sufficent funds and being El cheapo I will stick with the low cost epoxy.I will not pay 4 times the price as you are paying $70/gal for advertising.I guess I sound like I work for US Comp.No, I just want more bang for the buck.
Caution do not search for custom formulations as the thread will go to 5 million posts.Stick with the formulations from the formulators.
Larry

[lgalla]

This is a private message for Calvin aka Atenman1.
Looks are deciving.These cabinets are actually vibratory compaction units.4 produce 145db at 1600watts/box total 6400watts.These units must be solidly fastened to the floor as they may self levetate.As vibratory compaction units they are up to the challenge to liquify any E/G mix.They also double as extreme nightclub subwoofers.
Larry

[ckelloug]

I talked to U.S. Composites again today and their 635 resin is based on Reichhold Epotuf 37-127 which has reactive dilutents. From yesterday's exercise, the slow hardener is Reichhold 37-606. I believe the resin is similar or equivalent to Dow D.E.R 324. Though the resin contains glicidyl ether, the MSDS doesn't show either the resin or the epoxy as Hazardous. Datasheet is attached.

Cheers,

Cameron

[romihs]

Ckelloug,

Thanks for your answer.

Looking at the data again, I find it weird that that they measured the flexural modulus (page 5) on epoxy that is not annealed according to specification (should be 10h @ 70C) ....
Then take a look at page 4, they specify the 'Modulus of elasticity (flexural modulus)' = 22600 MPa when annealed for 10h at 70C...

Is this the same?
I mean, is modulus of elasticity the same as flexural modulus?

This is confusing!

Regards

Sandi

Sandi,

I looked at your epoxy the other day but until getting the Reichhold formulation, I wasn't really sure what to compare it to. Comparing the fluxral modulus of yours vs. the Reichhold stuff, your R&G epoxy is 2730MPa while the Reichhold stuff has flexural modulus of 4900MPa. Given all things equal, your epoxy will deflect about 30% more that the stuff Walter et. al are using when formed into a beam. The viscosity of your R&G epoxy is 1600 cps while the epoxy from Reichhold is only 600 cps, (I assume the epoxy is similar to the hardener but may be wrong). An cps (centipoise) is equal to an mPas which is a milli-Pascal second. From wikipedia water is 1 centipoise in viscosity while motor oil is 250 cps in viscosity.

I believe your epoxy is about 3 times as viscous as the stuff from Reichhold and it also seems to be much faster curing. They show the R&G stuff being cured overnight at room temperature and 10h at 70C. The Reichhold data sheet shows theirs being cured overnight at room temperature and 2 hours at 120C or 7 days at room temperature.

A 4 inch square beam 48 inches long made from your epoxy cured according to the data sheet with a 100 lb load placed in the middle would deflect .027 inches while the epoxy Walter is using would deflection .022 inches. This does not reflect the addition of aggregate or particles.

In short, your epoxy is more viscous and faster curing with slightly lower strength than the stuff Walter et. al. are using. There is no reason however that you can't make serviceable parts with it, it may just require different processing to avoid air bubbles, slightly larger members to avoid deflection and perhaps slightly different aggregate design. Unless you are engineering your stuff to really tight tolerances all this is to say the difference probably won't matter except in ease of mixing.

I am very very far from expert at this, but I hope this helps.

[ckelloug]

Sandi

I've looked again at your datasheet. The flexural modulus cited on page 4 is cited for epoxy reinforced glass fiber specimens. The data specified on pg 5 is for cured epoxy not reinforced: just the parameters of the epoxy. The data from pg 5 was stated to have been cured for 2 hours at 60C and 2hours at 70C. I assume both samples are completely cured but I am sure lgalla could shed more light on the curing parameters here as, unlike me, he is an epoxy expert.

Flexural modulus is like tensile modulus but is measured on a small beam instead of just pulling on the ends a cylinder. From what I've googled for on the internet, since it wasn't in my engineering mechanics class, flexural modulus is used for calculating deflections of beams made from materials that behave significantly differently under tension, compression and shear. Composites often behave in such a way that the tensile and compression moduli do not accurately predict the properties of the material when loaded as a beam and thus are really appropriate to only for the pure tension or compression loads for which they were intended.

It appears that R&G figure that both the flexural modulus and the tensile modulus are moduli of elasticity and then go on to state which one they mean. This violates what I would consider the normal engineering way of specific words meaning specific things but perhaps they are using an epoxy industry convention in their language that I am not aware of.

Good Luck, Sandi. I hope this has been of help. Keep us informed.

[lgalla]

Hay Cameron I posted this pdf quite a while ago and it may deserve review.The addition of low % glass fiber dramadically increases all properties of polymer concrete.I learned a small % of milled glassfiber provides extra re inforcement.If you get even one fiber between the aggregates strength goes up.The boys won't like the 20% epoxy ratio.
I am no expert at epoxy and fillers other than hands on experience.I was doing this stuff 20 years ago with out the web.I had to contact suppliers and get data in the mail.The info in my head maybe outdated,but some of the guesses I made were good.
E/G or example formula:Mold backup.Mix epoxy with sand until very thick.Would like higher strength, add milled fiber.Too thick,place mix container in hot water to lower viscosity,coat mold with mix.Resin pooling would occur in 10 minutes,soak up with glass cloth or sprinkle in more sand.Not very scietific,but worked for me.I like the thread as some of my guesses 20 years past were good.The problem I find with the web is too much info.
Sandi's resin and hardner specs are confusing,It appears the resin/hardner must have post cure.Sandi should use a room temperature curing system???

[walter]

Taking Larry's advice on fiberglass:
(for test purposes)




I also did another pipe test:




Took Geof's advice and left the sample on warm surface (7 days).

1. I did have a massive under cure.
2. Still think that the overuse of pigment weakened (gummed) the sample.(chair)

I'm heading to the lab to do some more destruction.
_

[walter]

Ok, done testing.

Conclusion: I'm going back to buying tools at Sears...
_

[ckelloug]

Larry,

I looked at your study and it's interesting but they left out the important parameter of how long the fibers they used were. Fibers are another mechanism besides aggregate and nano-particles. Fibers about an inch to an inch and a half long will be almost as good as cloth for most glass and carbon fibers and easier to mix.

I did not look at attachments in the first 800 posts as I was only a lurker then and not a member then so thanks for reposting. You did notice my comments about the US. composites 635 having reactive dilutents?

Walter,

Looking at your test pic , the clamp failed in brittle failure making me think it is cast iron or some such thing with lousy tensile strength. Also, the size of the sample as opposed to the clamp makes me thing the clamp is way to small. An earlier back of the envelope calculation indicated pressure to fail a sample will be near 5 tons for compression of a 1/2 inch square sample. Don't know for the flexural setup you have but it will also probably be large. Finally, my readings show that the epoxy cure can be massively affected by additives like carbon black. I would advise two hours in an oven at 320F to ensure that the sample is cured if you suspect gumminess as the paper I read on nanosilica had them doing that when they discovered their epoxy had not cured.

Gotta go move a pile of lumber today so might not be fast on the replies.

[lgalla]

Cameron the fibers were 6mm.
Glicidyl ether is a reactive dilutant containing epoxy groups which crosslink with the epoxy.If US Composites is shipping Non Hazmat, their epoxy is not flamable.Any epoxy with solvents would ship Hazmat.

[ckelloug]

Larry, The fibers were 6mm long. They didn't give the diameter. From vendor spec sheets I assume they're something like zoltek pan33: See http://www.zoltek.com/panex_products/pan33_chopped.pdf

There is a parameter called the critical length for fiber reinforcement that if exceeded by a factor of 15 yields a formula that is almost as good as infinitely long fibers. For 7 micrometer fibers like the pan33 it's about 1 mm and thus 15 times that is 15mm or about 3/4 of an inch. 6 mm fibers are useful and probably easier to mix but do not provide the absolute maximum strength.

Thanks for the comments on glicydyl ether. I've strictly got book knowledge on these subjects and don't know the chemistry portion yet.

I'm thinking that my uber formula for parts made from the 635 epoxy is probably going to be something like 87%/ quartz sand like the foundry sand in your article, 2 %carbon black 4% 1 inch long 7um diameter carbon fibers and about 7% nano particle filled epoxy resin plus the correct amount of hardener. From what I've been reading, it may also help to add a pinch of cobalt acetyl acetonate to improve hardness and modulus and possibly some fluoro-surfactant to make the mixture better at self-de-airing. Only some experimentation will tell if this is close to right and it is not rationally thought out yet.

What I'd like is a long wearing high modulus mixture which doesn't shatter and is good enough at self-de-airing to not need serious vacuum.

Finally FWIW, I just realized that the factory and main office of Toray Carbon fiber US is about 15 minutes from where I live. Therefore wholesale shipping= station wagon load.

What I need to figure out is what the advantages of fiber reinforcement vs. large particle reinforcement are.

Thanks for the comment on the glicidyl ether.

[walter]

Moving on to the next samples:





From the toughest (top) to the weakest (bottom):




Epoxy/3 micron Quartz sample was mighty tough and went with a very loud pop.

Epoxy/Zeeospheres sample was also pretty tough (for a hollow structures!).

Epoxy/400-700 micron Quartz sample was the crappiest one (as expected).


* * *

You've got to remember that Quartz is the one with Mahs 7 hardness, not the Epoxy. The sample contained a lot of epoxy (filling large space between grains) which weakened the structure dramatically. And no, vibrating/vacuuming wont change a thing- epoxy does not compact, does it...
Epoxy was also causing some major air entrapment so... It was time to get rid of the epoxy.


* * *

The solution to all my problems was found in post #660.
New system is in place and working very well.


* * *

Some more scientific sampling will be done in the coming weeks. Still waiting for my precision scale, heat lamps, working on normalizing the size, testing methods, etc.


(Not that I really need any of that... )


:cheers:
(Oh yes it is!)



* * *

Ok, that's it for today. I would encourage everyone to post their comments, projects, results, pics, whatever, let's make this a community thread where we can all share our views and experiences.
Have a project? Don't want to start your own thread? Slap it in here!


* * *

BTW, There's some amazing info on these 90 pages and you should definitely sift through the old posts. Just look at the list of contributors!

[Mcgyver, Igalla, Episs, RotarySMP, pminmo, Geof, greybeard, schrupphobel72, dansutula, turmite, JWOOD, the4thseal, Aramon, nMotion, atenman1, BobWarfield, Xerxes, RICHARD ZASTROW, Chris-Jennings, digits, Oldmanandhistoy, JerryFlyGuy, fyffe555, stlc1, ger21, myinisjap, vger, wizard, brunog, CNCAddict, oldpoopie, skippy, Eson, WilliamD, vacpress, sposl, martinw, lerman, Big S, jsage, Zumba, WYLD, svenkala, mhasting2004, Armstrong, davo727, RogerH, djshop, merl, ahlbebuck, yugami, ericdwilso, Mike Mattera, pupa, Stepper Monkey, wjfiles, LeeWay, speed33317, gt3073b, Switcher, max_imum2000, hansa, victorf, ckelloug, eloid, HBFixedGear, jkeyser14, VoxLimbo, garfieldsimons] <--- big thanks to everyone!


* * *

And once again:

The Whole Shebang on E/G: post #541 (page 46)
E/G Tips & Tricks: post #364 (page 31)
Useful links: post #241 (page21)


* * *

Have a great weekend!
:cheers:

[lgalla]

Walter, you are beaming??

[walter]

Hey where did you get that picture??

That was top secret!

[lgalla]

Cameron I am not a chemist,but was taught to respect cobalt accelarators.They are in polyester resins and react with the cataylst,MEK peroxide to generate heat for cure.The supplier was reluctant to sell this product as if memory serves me if the cobalt and mek were mixed together by mistake a violent reaction takes place.I found a pdf on cobalt111acetylactonate.Don't know if this is the same product you mentioned.
BTW finding MSDS was difficult as the manfactures required loging in to access MSDS.Makes me wonder.

[ckelloug]

Larry,

Thank you for this warning on CAA (pronouced Cobalt 3 Acetyl Acetonate denoting the +3 oxidation state of the cobalt). I am by no means a chemist either. I had no idea that it might be baaaad as the MSDS didn't look terribly hazardous. The book I found on nanoparticle reinforcement by Frederich Klaus suggested the use of 1.5% of the hardener portion as CAA and said it demonstrated a 5% strength improvement in the epoxy system. They also suggested .1% of the harderner as N,N dimethyl benzamine if you have any comments about that one.

Sachem Chemicals was their source for CAA and here is the data sheet:
http://www.sacheminc.com/download.php?id=185

Most of the vendors are secretive about data sheets mainly because they are secretive and don't realize that there is more to gain by letting us potential customers see them than worrying about competitors who make _identical_ products see them.

P.S. I was able to use my title and dayjob corporate affiliation to get a chemidex account which will let me pull datasheets on most any resin without the level of BS and telephone work it took me to get the first hardener data sheet from reichhold.

[lgalla]

FED/EX will take Hazmat materials at a premium cost.I thought epoxyies with VOC's were the only Hazmat materials.Some hardners are Hazmat.Granite city tool has pigment paste which is Hazmat and they will not sell online.If any epoxy can be shipped non hazmat,I assume it is safe.Requesting MSDS from the formulator is good insurance.
Cobalt in polyesters is below 1% but the raw material is possibly not too safe for an end user.
I suggest anyone handling chemicals check the MSDS for themselves.Agreed?
Larry

[ckelloug]

Checking the MSDS on anything you want to handle is a good idea. My opinion is that I'd prefer not to personally recommend something to our compadres on the thread that is more hazardous than the resins and hardeners already in play if it is avoidable. CAA was only claimed to be a 5% improvement on the properties of the nanoparticle reinforced resin so for Home Shop purposes we may be better off without it.

[lgalla]

I am on a Hazmat roll.
Carbon fiber,which has been mentioned in some posts.Is it safe,I don't know.Being of age and seeing the introduction of carbon fiber,by possibly outdated information,I question its safety.I have books and pamphlets on lightweight aircraft.They state carbon fiber spars must be encaspulated in glass fiber to contain shrapnel in case of failure.Also EV or electrovice had woofers with carbon fiber and they recalled them and paid air freight for new drivers.Google search does not find any serious problems.Perhaps 20 years ago we were too cautious.I see tennis rackets.ski poles.race cars.Military aircraft etc made of carbon fiber.I guess upon fracture or failure micro sharp fibers with epoxy could give slivers and lodge in your lungs as an inert material for your lifetime.These are guesses,anybody know answers for sure?
I will add copy from what I could find.

I am actually shocked at how little safety has been paid attention to online for carbon fiber. A Google search for carbon fiber safety tips yielded zero useful results for me. I am no expert on carbon fiber safety, so I will just go through the common sense stuff. So first, lets talk about the dangers of carbon fiber. Carbon fiber is exactly what the name suggests, extremely thin strong fibers. Basically light weight needles capable of jabbing into your skin or worse - capable of becoming airborne and jabbing into your lungs and eyes, etc. Coughed up blood, anyone? You get the idea. Apparently some people are even allergic to some degree and get skin reactions from it. "It's a skin reaction that looks like a really bad sun burn and itches like a mother." If you plan to saw or drill carbon fiber, expect copious amounts of fine particles to become airborne.

Carbon Fiber Safety
Kevlar anyone?My old spec sheets say it has good vibration loss.

[lgalla]

MSDS roll,
While on the MSDS roll,I thought a search on beer would be interesting: Copy:
"For example, if you look up the MSDS for ethanol, the active ingredient of alcoholic beverages, you will learn that it is highly flamable and severely toxic and may cause death if ingested. Something to keep in mind next time someone offers you a beer. "
After all these years of a smoke and a few beers before bedtime,I have had no fires.Guess I have been lucky.Think I will pass on the last beer and smoke.
Larry