Epoxy

See no n.g. for adhesives & epoxies, so if there's a better forum for this,
just point me to it.
I need an epoxy that is strong to the point of brittle. I want no flex; it
has to transmit vibration as close to 100% as possible.
Am I looking for a high Shore Hardness value? That's what Devcon uses in its
data sheets to specify hardness.
Is this something that I can achieve by changing the mix of the 2 parts? If
so, what do I lose if I use more hardener?
Any personal experiences with epoxies that you found to be harder than
others?
Thanks.
FBt
Reply to
Esther & Fester Bestertester
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For spacecraft vibration testing we use Dental cement. It's extremely non-compliant so it is good for transmitting vibration from a structure to an accelerometer. It is brittle so we remove them by just taping them with a hammer and breaking them off the surface. We first put a layer of thin tape on the surface to protect the surface. the tape does not affect the vibration response. bob
Reply to
bpederso
try searching for sci.engr.chem or sci.engr.*
martin
Reply to
Martin Griffith
Sounds to me as if you're actually looking for stiffness, not necessarily strength?
I think you'd want to look for (or make) a filled epoxy. A high-strength epoxy which is loaded up with (e.g.) chopped or milled fiberglass would be very stiff.
Reply to
Dave Platt
Filled epoxies (loaded with various mineral and glass bits) are much more rigid than plain epoxy. But if you start with a slow cure epoxy (30 minute versus 5 minute) the epoxy, itself will also be a lot harder. Glass micro spheres are a good filler if you want to lower the density, and glass micro beads or aluminum oxide if you want to raise it. Even adding talcum powder adds to the rigidity, but the gas bubbles it entrains lowers it (foams are less rigid than solids of the same material), so vacuum degassing increases the rigidity.
A very rigid mineral filled epoxy is Hysol 1C:
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A slighter harder aluminum filled formula is Hysol 9434:
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But they make lots of variations:
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Reply to
John Popelish
I cannot suggest a harder epoxy but you pressed a sensitive button on me so here I go.
Many years ago (1991, to be precise) I opted to epoxy-fill my first 5kV coils I did for my then employer in Cologne, Germany. I used no multiplier, straight flyback @ 5kV; about 1000 windings on an RM8 core, winding and insulation layers being an art of their own. I located some very liquid epoxy meant for that purpose, then the whole module went filled, using vacuum to make sure there were no cavities. Everything worked fine, the filling was perfect - I got asked how come the space between the *windinds* was not filled (0.05 wire, mylar foil between each layer) by my then employer... Some years later I had founded TGI in Bulgaria and did the first HV source making the coil more or less the same. However, I used off-the-shelf epoxy; it did not get as hard (although it was by far not as liquid before hardening), and after some warmup it began to conduct just enough to make the thing noisy... I wasted more than one coil (wound with a lot of work) until I got what was going on, I spent days if not weeks on that nightmare... Eventually I learned I needed no filling at all, just a few drops of melted silicon at the right spots did the job (still does) quite well.
And on another occasion I had a guy from a detector repairshop in Sofia use the same effect trying to cheat on me... The HPGe gamma detectors are very sensitive things, the front FET is cooled to -90C or so for lowest noise. The bias is a few kV (3.5 in that case), and the HV input is filtered through a 1Gohm/0.47uF group. Well, he had had the detector in his hands to "check it" for me and had put a stripe of such epoxid along the resistor between its pins... (The resistor is a rectangle, say 20x5mm, 1mm thick). After some warmup - the preamp consumes not so little, they have not changed its design for >20 years - the detector begins to behave like when it needs repair. Well he did not get it for repair because I looked and discovered what he had done and cleaned the mess up -and the detector worked fine. A few years later he got the same detector in his hands directly from customers and did the same, this time he had added a stripe across the capacitor, though, and had scratched the paint of the resistor between the pins. Mind you, I had told him I knew what he had done the first time and he had done it again. I guess the epoxy must have had braindamaging effect as well.... (and I had refused to believe other people telling me he was sabotaging detectors before I got burned, the epoxy must have worked on my brain as well - perhaps while dealing with my coils... :-).
Dimiter
------------------------------------------------------ Dimiter Popoff Transgalactic Instruments
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Esther & Fester Bestertester wrote:
Reply to
Didi
If you can afford it, Araldite 2014. 4-6 hrs grab, 24hr set.It's a grey paste two part.-
Reply to
TT_Man
With the way you worded this, it would seem that a technical response would go right over your head.
Epoxy mix ratios are NEVER meant to be altered. You need to find an epoxy that matches your needs. The only time I ever saw mix ratio ranges to alter behavior, it was with an epoxy branded as "stycast". Which, would oddly meat your needs.
It will not likely be cheap, however.
Reply to
The Last Mimsy
sci.materials is good.
Al
Reply to
Al
If you have been letting it cure at room temperature, try about 15 minutes at 160 F or so. It will get a lot harder.
Tam
Reply to
Tam
Dunno if it's tough enough but I use GR epoxy glue from Industrial Formulations. 24 hour cure. (Sometimes a pita.) Here in BC.
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"We have an epoxy system for almost any project". Really?? :P
All I know is that GR epoxy has less flex than Lepage 2 page epoxy (dual syringe) I got from the hardware store.
D from BC British Columbia Canada
Reply to
myrealaddress
Nothing to add.. Just checking my usenet client settings. Ignore this part..
D from BC British Columbia Canada
Reply to
myrealaddress
Don't let your meat loaf ;-)
Tim
-- Deep Fryer: A very philosophical monk. Website @
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Reply to
Tim Williams
Does it matter when the heat is applied? Right away? Or after it seems to have cured as much as it is going to at room temp?
Reply to
Esther & Fester Bestertester
To those who offer help even to the misguided, thank you for the benefit of your knowledge.
To those who offer directions to the appropriate forum, thanks for the (index) finger. :-)
FBtf
Reply to
Esther & Fester Bestertester
sci.polymers or sci.materials might be a better bet. There are two general ways you can make a given epoxy harder: bake it (an hour at 100C does wonders) or put filler in it.
If you're bonding hard materials, you might want to use a glass bead filler. When you squeeze the bondline down, the spheres contact the surface, and as the epoxy shrinks (1% or so), it applies a preload to the glass/substrate interfaces. That's a pretty stiff joint.
If you're trying to do something in shear, e.g. attach a strain gauge, glue is not your friend at all. You might be better off using solder or indium bonding or something like that.
Cheers,
Phil Hobbs
Reply to
Phil Hobbs
I have been waiting a few minutes until the epoxy is no longer runny. I turn the oven on to 200, but turn it off before it reaches temperature. Have also used a heat gun on something that was part of a large stationary object (toilet). I haven't bothered, but this information should be available from the manufacturer.
Tam
Reply to
Tam
Rubinno cement made by Singer Kearfott in the 70's was used on guidance systems for the Sram missile, PC3, and A7 navey fighter jets. It is the best there is.
Reply to
Gerald Newton
Google turns up zero hits. Is the correct spelling? Any web references you can give?
Thanks, FBt
Reply to
Esther & Fester Bestertester
It is probably $50 a quart. Minimum.
Reply to
ChairmanOfTheBored

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