[JerryFlyGuy]

Has anyone on here ever added aluminum or Stainless powders to an epoxy mix? I'm looking at using this as a potting mixture as I've decided doing the same job w/ 'store bought' industrial epoxy's are just to darn much money for what I want from them. [well they aren't that bad, its just that I need so much of it that it gets expensive] If you have done this, care to share how it went? How much powdered metal was added to how much epoxy? Any advice would be appreciated.

Jerry [not new to composites.. just new to metal powders in composites ]

[lgalla]

Jer try www.shopmaninc.com for epoxy,$40 to$50US/gal
Google search Fine powder america, every type of powders alu stainless Etc.
How much to add?As much as possible:As thick as you need.
Larry

[JerryFlyGuy]

Thanks Larry, my biggest question is, how much should I buy? I'm going to need 1.6 US gallons of epoxy to do the job, how much stainless powder would this take? I have no idea.. Btw, have you ever imported aluminum powder? I understand under the proper circumstances its um... 'pyrotechnic' in nature... knowing our find stuffed shirts down east opinion on pyrotechnic's, I doubt I'd be able to get it into the country.. [hence the lean towards stainless]

Jerry [I'll get to your other question here yet tonight.. I hope..]

[HuFlungDung]

Jerry
Do you have to machine into this stuff after it has set up? I'm just wondering whether the filler has to be metallic? SiC might make a good filler as I suppose the crystal strength is quite high.

[JerryFlyGuy]

No Sir! It is completely just a potting mat'l/process. I was going to use Devcon Liquid Steel 'B' , but at $150 for a 4 lb kit.. I'd need 6-7 kits.. so, t'was a bit rich for me' blood.. I started to look for an alternative.

My understanding [and after reading some epoxy websites] that adding a metallic powder, greatly increases the 'toughness' and hardness/durability of the epoxy. I want something that isn't going to crack to easily so I started diging into this a bit deeper. In the end, if I could buy a epoxy kit for $150 Cdn [ in Regina] for 1 US Gallon [including a 3/4 gallon of hardner] and about $50 usd for the alum/steel powder I'd have the same 'basic' thing as the devcon @ 19.04% of the cost. [still expensive for what it does but.. wadd-ya do eh? ]

I'm open to suggestions of an easier/cheaper way to accomplish this..

Jerry

[JerryFlyGuy]

Opps.. missed the Silicon Carbide comment.. first of all, where would I get it? I'd have to look into seeing if it bonded w/ the epoxy ok.. at a guess I'd say yes.. but who knows.. mind you I don't suppose it needs to be to great of a bond, its completely encased in the epoxy.. and we all know that 99% alum would have oxided completely.. which means it wouldn't proper bond to the epoxy worth #%@#, yet they recommend it.. so.. the bonding this isn't a concern obviously..

Really the best mat'l might be lead powder.. [ like you'd ever find that in this MSDS crazy side of the world] as doesn't Pb have the best vibration dampening properties of any simple element in the world?

Head scratching...

Jerry

[HuFlungDung]

I think you can buy either SiC or aluminum oxide powders for sandblasting. Maybe even a certain grade of blasting sand (minus the dust) would work.

On second thought, maybe a fiber filler would be more what you need, because you might want to avoid cracking when this thing goes under tension. I suppose fiber glass or carbon fiber?

[lgalla]

Jer Aluminum powder is mixed with magnesium and is called "flash powder"Aluminium powder is very flamable if it has a "catyalist"or high temperature to set it off.Fine powder America shows shipping to canada.there is probably no problem.Having said all that ,If using for rail potting I would go with stainless also as a powdered metal in epoxy will exhibit properties of the metal.You don't want aluminium responding to temperature changes.
Ratio?Depends and depends and depends.Depends#1Usual filler ratios are 1:1 by weight.Depends#2Viscosity,u can put a ton of filler in laminating epoxy but it will settle or run out.Thicker epoxy is usually considered glue it may be a better choice.Depends#3Ar U A cheap{thrifty} guy?Put as much filler as you can and still have the viscosity you can work with.Buy a small test amount and try it.
EPOXY RULES always scrape the sides of the measuring vessels after pouring into mix container.After 1 to 2 min.add filler to taste.
Mixing epoxy generates lots of air entrapment[TONS]I use a vacuum pump to remove the air by putting the mix in a vacuum chamber,in my case a binks 10 gal pressure pot.To remove air in small batches you can "lick the surface" with a blow torch.You will see the bubbles popping.Needless to sayyou must have pure epoxy with no solvents.Also the viscosity will go way down and curing sped up.
CLEANUP Epoxy thinners are deadly smelling.I found methyl hydrate cleans your tools and hands very well.I am not a chemical engineer or anything but I would like to share my experiences,Larry in epoxy land!I am more of a cook,I make good soup.
10 or 20 years ago I used epoxy aluminum for molds casting 5"thick parts.The
exotherm would pass through the mould and prevent cracking.
Because I can go on &on&on&on one last epoxy story not related to the question.
One night I am leaving work and the exhaust on my truck gave up.I crawled under and the exhaust pipe was broken at the converter on the hot side.What to do???Take buss?Noway.Epoxy to rescue.I reconded fiberglass and alu epoxy would get me home.Theory heat pass through epoxy aluminum,get me home.Saturate fiberglass cloth with epoxy wrap around pipe& converter.Turn on motor for cure and bake cycle,get home no taxi.
Drove like this for 2years,Thought I am worried may be I should get new exhaust.Midas said "what the hell you had on this"Anyhoo another chapter in The adventures of epoxy.
Larry

[lgalla]

In reply to fiber type filler fromHuFlungDung.Fiberous type filler will tend to be like "JELLO"I think Jerry needs something that will flow and self level as I beleive he is injecting epoxy under the rails.
Larry

[pstockley]

Where in Canada are you located? I have some epoxy I would sell you cheap. I bought some for a laminating job I was doing which has been sidelined.

[XYZADave]

Just a note,

re:heavy metal powders
I've used premixed,tungsten filled, high hard, polyurethane epoxy as an
abrasion resistant cast insert in a plastic tooling mold, and found the
powder was so dense it would sink! ( as would the steel balls from a
shot peen blaster As to the overall strength of the resulting mixture
I could only guess, but would suggest you wouldn't gain much over the
inherent charastics of the base casting epoxy.
One the other extreme, if your looking for a filler, make sure whatever
you use doesn't float! Just my two sense worth.
Good luck,
Dave

[Haydn]

I used Unibond and Devcon on my machine. I used steel powder mixed in on a couple of joints at about 50/50 by volume but this makes it quite a lot thicker and wont pour. If you use a standard epoxy adhesive (Araldite in UK) you can mix powder in with it and blow the epoxy in with a hair drier, this makes it flow as it goes runny with the heat. I did the bed for my rails on a surface table, I guess I was lucky but a local engineer had an 8'x4' surface table that I covered in cling film, sprayed with mould release, coated my rail beam surface with steel epoxy and then pressed them down onto the table. I did this for Y as well and the whole of my bed in the end. It gave me accuracy of 0.02mm over 1.6m length, was quick and no machining for someone with limited machining capabilities. I also cast a reference edge using a grade A straight edge with cling wrapped around it. This was all done on cold days as the epoxy I used was nearly cured in about 10mins, the cold extended this to nearly half an hour. You can see it in the picture.

[JerryFlyGuy]

Wow.. lots of replies come morning I'll start at the top.

Hu, I'm not to worried about tension, more just a compression/filler between my subplates and the weldment structure. Now that I've got it all level and bolted down in place, I want to take as much load off the bolts and have the entire structure surface taking the bearing load.

Larry.. I'll have to email them and confirm. The alum powder is cheaper, however maybe for my application the stainless is better.. I really don't know.. Btw, Larry I would recommend latex gloves over using Methal hydrate to clean your hands. Unfortunatly, you'll only learn this after its too late. Another fella I've met mentioned he used it all the time when building his plane and now his hands have no natural oils, they are forever cracking and he's always using lotion to keep them from doing so.. they are getting better [ this is 10+ yrs later] but they are now super sensative to any type of chemical on them [from gas to the harder stuff]. I know using gloves is a pain [ I've been building the same plane and things sure can get sticky... I know.. ] but it's worth it in the end.

It's pretty amazing how long that muffler lasted.. I'm not sure I'd recommend it as a prefered way of fixing them..
Also, I think your thinking of Silca powder giving the epoxy the jello like texture [isn't that called thixotropic?]. The most common 'brand name' of silica powder in epoxy circles is "Cabosil". I'm sure Silicon carbide would work fine, it would be a non-homogeneous mixture [ wouldn't mix in like silica, just be suspended in the mixture like the metal powders] however I haven't found a supplier of it.
Pstockley.. I'm in South Sask.. where are you and what kind of epoxy do you have? It might be more hassel than its worth shipping it out as most people consider it a "Hazardous" good.

Dave, thats one point I'd wondered about, in my application it's going to be about 1/8" thick at its thickest point, however sinking may still be an issue. Maybe thats why aluminum is so popular? [it doesn't sink as easily?]

Hayden, you were lucky! Don't happen to know anyone over here in Canada who has a 20ft long surface plate do ya? I could really use one . Thanks for the 50% note, thats definitely not how thick I want it! I'd like it to be about like a heavier motor oil.. not molasses. I'd like to be able to pour it down a 1/8" wide slot and have it flow out for about 12-14". If I don't have to apply heat it would be best as I don't want to impart any heat 'movement' in the substructure. Its only a welded structure, not a huge chunk of iron.

In conclusion, I'd say that the stainless or alum powder is the proper mat'l [primarily because of its easy access] The one website says to add alum powder at 3-10% by volume so I'll have to get some and experiment w/ it. My supplier of epoxy might be able to get me the powder as well so I'll just have to wait and see what turns up.

Thanks guys!!

Jerry [getting educated! ]

[lgalla]

Jerry I looked back to some of your drawings on rail mounting.If you are injecting the epoxy to fill a gap you maybe don't filler.It will just impeade the flow.Low% aluminum is just for colour.I guess you are concerned of compressive stregnth.I don't know offhand.Late for work now.I will check on the psi of epoxy unfilled.Hopefully the simple way is the best way.
Larry

[JerryFlyGuy]

Larry, you could be right. I was just going under the premiss that if the devcon had it, maybe I should also.

Jerry

[pstockley]

I am located in Ontario so it probably isn't worth the hassle of shipping it like you say. I wonder if using aluminum would be a problem due to the increase in expansion compared to steel? If you could get finely ground ganite that would be ideal.

[JerryFlyGuy]

Oh well, I've got a decent source pretty close to home here. As far as the powder thing, granite might work very well, I did some quick searchs on the net but didn't find a supplier per-say.. lots of links to possible uses etc. Oh well, if I can get the aluminum, thats most likely what I'll do..

Jerry

[Haydn]

Jerry, you could ask this guy he's in the US and poured quite a lot of epoxy for his machine and did use metal powders as well.

http://www.oneoceankayaks.com/madvac/machine_frame.htm

[JerryFlyGuy]

Thanks Haydn, It's been a while since I've talked to him, I may have to send an email his way again. Reading that over again, its good to know that my though process isn't completely off

Jerry

[lgalla]

Hey Jer,
From Dow website Epoxy can be as high as 15000psi compressive stregnth.
From Devon website.
epoxy aluminum 9840psi
epoxy stainless steel 8400
epoxy steel10200
These mixes are putty.Not to much flow.
Never imagined filling would reduce the compressive strength.
If you need flow,you must go with the flow,unfilled.
Larry