[snookered1ca]

Hi Sandi

Thanks for the response
I haven't found a NA supplier for the same epoxy but there are many others, I'll need to determine what differences there are between them. How did your results turn out. What problems did you encounter ?
We are looking to cast some lathe tailstocks.

Bruce

[ckelloug]

snookered1ca,

Welcome. I can't speak for sandi but I can say that a lot of the epoxies out there that are easy to come by are formulated for toughness and stickiness rather than setting up hard.

My own work with the shopman inc slow hardener and think epoxy (Reichhold 37-127/37-606) is that it doesn't get as hard or stiff as we would like. I've gotten some much better results with Hexion 813 resin and Degussa Isophorone Diamine hardener but this isn't a solution I would recommend for home use due to toxicity and the tricky curing temperature profile required. I'm not sure I've got the curing profile just right but curing the whole thing at 85C makes the hardest most heavily crosslinked material.

Since you're in canada, you might talk to crosslink technologies and ask them what they recommend.

I haven't gotten any work done lately due to having melted my UHMW sample mold in my curing oven. I'm on a crash course right now to build a vacuum and pressure tight mirror finished steel sample mold but I won't be done for a few days.

Crr is expected to report his results with DER 331 and Huntsman amines in the next few weeks. In general, resin isn't the problem so much as finding a hardener that makes the stuff set up like rock as opposed to rubber. Somebody with more expertise in formulation like crosslink might have a good recommendation.

Regards all,

Cameron

[romihs]

Hi Bruce,

My results were a little disappointing. But that is due to the simple, limited, method I used to make the samples.
The samples were small, hence difficult to measure out the correct quantities accurately and I did not manage to compact the samples as well as they could have been.
Also, I did not perform the post cure on the samples.

The samples I had (I've thrown them out since) were "quite solid" though despite not having been compacted.

When I have the space, I will restart my work on this, as I would like to build a CNC lathe with material. I will construct a good vibration table; devise a thorough mixing system and purchase an accurate scale.
Anyway, enough about my dreams...

Attached is a PDF that you may find handy.

Regards

Sandi

[snookered1ca]

Thanks Cameron

I have been in contact with Crosslink and they have a product that they used to produce some epoxy granite Curling stones with a short while ago, which so far looks to be an ideal product that shouldn't be at all rubber like . There is also another resin maker PTM&W that makes a wide range of castings resins and hardeners, they recommended their PT4450 product.

Bruce

[jhudler]

Just a note:
Lest we forget (John Wayne; She Wore a Yellow Ribbon).

Buying the epoxy and aggregate is 1/4 the battle. (Ignoring the 3385 previous posts .

You now have to mix, vibratory compact, and cure that mass you think you're about to pour.

Also, one must not take the attitude of DFU (a rather vulgar acronym), so buy extra.

[ckelloug]

snookered1ca,

What did crosslink recommend?

[snookered1ca]

Cameron,
crosslink recomended their CLH 6520 product and I've attached their product data sheet. However after reading a lot of the previous posts, I'm at # 85 thus far, I don't think this is the correct product. It is described as a semi-flexible end product.
When I was talking to a rep from a supplier of PTM&W products he proposed a novel method of introducing a steel shot filler. That was to pour in a determined quantity of mixed resin and then add the shot until it came to the top of the epoxy and then repeat as necessary. In theory this would enable the maximum amount of filler to epoxy ratio and it would eliminate or reduce the probability of voids.
One concern that does come into play is would a casting with a steel shot filler have the same dampaning properties as one with crushed granite filler.

Bruce

[crr]

Hello all-

Here is a picture of the mold I am going to build so that I can make 5 samples at once.

I also have all of the materials necessary (Resin, hardener, aggregate additives) and hope to have some samples by the end of next week.

The plan with the mold is to put the resin feed lines in the rounded ends of the individual cavities, then add the aggregate. vibrate, vacuum, infuse and cure.

[snookered1ca]

I'm new to this group and would like to get up to speed relatively quickly, is there any compilation of the posts that one could read without going through all 3388 of them. Even a current status overview would be helpful.

Bruce

[snookered1ca]

Sorry to reply to reply to my own thread but I just came across post 3320 - 3324 that has shed a great deal of light on the subject. Any other info would be greatly appreciated.

Bruce

[ckelloug]

snookered,

Check the sticky index thread at the top of the forum that the EG thread is in. That summarizes the contents of the first 1500 or so posts. Indexing is labor intensive and it hasn't been updated in a while. Thanks for the link to crosslink's reccomendation.

crr,

That looks like an impressive mold. I've been out in the shop turning the cranks on my bridgeport to make a block casting mold to cast 8x8 by 1/2 blocks. Your CNC will probably have your mold made before I even get all of the stock square Thanks for your work!

Regards all,
Cameron

[jhudler]

Cameron,
Have we run across an epoxy combination that won't outgas at 25 microns?

Might not be a problem for infusion (still have my doubts) however, deairing is another story. The bubbles just get bigger and spill out of the mold.

That's why I've focused on a vibratory compaction table.

Has anyone tried infusion yet? What's the limiting aggregate size?

Jack

[crr]

Hi Jack!

I am planning on doing infusion sometime next week.

I am going to document everything, and I'll post it when I get done.

[ckelloug]

Jack,

Tony thinks that the DER331 shouldn't have too much outgassing problem. I don't know anything about the outgassing characteristics of the Jeffamine hardeners but anything ought to be better than the witch's brew that is Reichhold 37-606.

Regards all,

Cameron

[snookered1ca]

When I was talking to a rep from a supplier of PTM&W products he proposed a novel method of introducing a steel shot as a filler. That was to pour in a determined quantity of mixed resin and then add the steel shot until it came to the top of the epoxy and then repeat as necessary. In theory this would enable the maximum amount of filler to epoxy ratio and it would eliminate or reduce the probability of voids and mixing problems.
This also presents some interesting options

1. cured unfilled epoxy, is it machinable ?
2. Steel shot should be machinable when encased in epoxy if the epoxy itself is machinable.

One concern that does come into play is would a casting with a steel shot filler have the same dampening properties as one with crushed granite filler.

Bruce

[lgalla]

Jack,
Just thought I would chime in.
Out gassing refers to vaporising components of the epoxy blend.You are seeing just air expanding from the mix.If you mix the A&B and vacuum the mix it will expand and foam 2 or 3 times the origional volume.De-airing a neet epoxy mix would require a 5 gallon bucket with only one gallon in the chamber to ensure it will not foam over the top.De-airing should be done before pouring into the mold and then mold vibration.There will be millions of bubbles expanding from the heat of exotherm and you will have to accept the top will not be perfect.
Larry

[Mcgyver]

hadn't been around this thread in awhile and was just checking out the index/summary sticky - what a huge effort! My hat is off to you guys, that may be the most complete source EG info on the planet, way to go

[Preston E]

Cameron, the Jeffamine hardners should not out gas at all as there are no diluents in the curatives...

Regards,

Preston

[probinson]

I'm sure that it is due to absorbed atmospheric moisture and dissolved gases but I can tell you that those epoxies definitely do outgas under vacuum.

I suppose, for any such discussion, we need to qualify to what level of vacuum we are referring.

Low to medium vacuum:
I would consider this anything below about 27 inches of mercury. I place the cutoff at 27 inches because that's about where you start to see gases come out of solution even if you have degassed your components once and just left them sit overnight. Below that your bubbles are mostly trapped air that is simply expanding as the pressure drops.

High vacuum:
I put this at anything over 27 inches of mercury (for the reasons above) up to the level that can be obtained by a standard compressor.

Ultra High vacuum:
This level of vacuum requires special equipment like diffusion or ion pumps or ultra fast turbines.

Now, given those definitions (all be it at my own personally assigned levels), all of your epoxies will outgas at high vacuum. For drawing epoxy into your mold, however, you will likely be using low vacuum, in which case, you should not have any outgassing and Preston's statement would be correct.

Pete

P.S. At ultra high vacuum even fully cured epoxy outgasses as do most plastics. A single fingerprint can outgas enough to prevent the required level of vacuum for some experiments performed here.

[bloefeld]

[QUOTE=probinson;521014]I'm sure that it is due to absorbed atmospheric moisture and dissolved gases but I can tell you that those epoxies definitely do outgas under vacuum.

Hi Pete,

You are all on the money here. If one has access to a decent pump you can draw nearly 1 torr at whatever elevation you are. To get a full torr you need to really bear down on it with very high end equipment.

Out gassing the two components before mixing is necessary. Then outgas the mix. Then suck it all into the mold under vacuum and keep the vacuum on. At this you will have a thin film of foam on top of the casting that will have to machine off.

When cleaning with acetone or MEK make sure that there is no residue left.

If possible keep the epoxy under nitrogen while stored.

I have recently used a similar technique to make a high performance bond between two composite components. To perform correctly the bond-line had to be .030" and as completely void free as possible. The bond is a c-channel that is 14 feet long. We shot it and then sawed it every 1/8th inch and inspected each section under 50 power magnification; the result showed no visible voids.

Cheers,

Bloefeld