[ckelloug]

Hi all,

I can see I'm not going to get back to this topic for a long time so I'm going to post the last formula I tested.

In general, an optimal recipe is based on characterizing exactly what you have and using as wide a range of sizes as your machine design will allow. In most cases, optimal isn't necessary. For filling bases etc. almost anything will work. For other things, a mix that goes from pea sized gravel #6 sieve to fine dust would probably be best.

My final recipe from the simulator was:
n6SiC.ag n16SiC.ag n36SiC.ag n70SiC.ag n180SiC.ag n320SiC.ag n600SiC.ag g200zeospheres-high.ag
0.242780, 0.168667, 0.112555, 0.100630, 0.110247, 0.087316, 0.022684, 0.155121,
Predicted packing density was 0.876454

Where the above are callouts for silicon carbide abrasive and 3m Zeeosphers and below are the volume percentages which are measured
by computing specific weight using the density and adding the appropriate weights of the components.

The Epoxy Used was a low viscosity epoxy: Hexion 813 and the hardener used was isophorone diamine.

For a 38gm batch of epoxy
30.3g Hexion 813
6.9g IPDA
1.0g BYK A525

Add 25.6g G200 to vessel and mix for 4 min.
Add 37.9g #600 SiC to vessel and mix 2 min
Add 44.9 #320 SiC to vessel and mix 2 min
Add 60g #70 SiC to vessel and mix 2 min
Add 62.5g #36 SiC to vessel and mix for 2min
Add 94.1g #16 SiC to vessel and mix for 2min
Add 143.6g #6 SiC to vessel and mix for 2min

Turn out into mold and vibrate.

This will be very stiff and may be easier to deal with given a little bit more epoxy.

Hope this helps.

Regards,

Cameron

[aveliz123]

By the picture you can say that you didn't use small parts of granite to make the composite more compact. Let say you uses 2 mm grains you have to use a 100 times more smaller grains to fill the space left by the 2 mm grains.

[ckelloug]

The recipe above is exactly what I used. #600 silicon carbide is dust. G200 zeeospheres are measured in microns.

[lgalla]

Wow can't believe this thread is still going with some of the same ole faces! Walter ever show back up?

I see people are using vacuum and vibration; good. Only I think 29.9 is a bit deep, the foaming in from boiling the volatiles in the epoxy.
Did a video on this some thousands of messages ago.

I experimented with gel coating molds before filling with EG, much easier to de-mold without destroying the mold.

Cheers!!!

Speakin of old faces,I lurk around a bit
Larry,,,The epoxy surface plate is flat

[probinson]

I have done a lot of experimentation and testing of vacuum degassing and use it almost daily so I'd like to add my 2 cents to this deep vacuum discussion.

If you are making small parts or parts that need to be optically perfect then deep vacuum definitely helps.

Under moderate vacuum, air bubbles get larger and most of them will float out. When vacuum is removed, any remaining air bubbles will shrink but they don't disappear completely.

Deep vacuum draws moisture out of the materials and any remaining air bubbles are eventually replaced by bubbles of water vapor. These bubbles also just shrink when vacuum is removed but, unlike trapped air, the water vapor is slowly reabsorbed and the bubbles disappear completely given sufficient cure time.


If you are degassing several cubic feet of EG, how practical is deep vacuum?

Utilizing moderate vacuum so the air floats out quicker is a good thing but not many of us have a walk-in vacuum chamber. A vacuum bag with a reservoir to handle the expansion/contraction and keep the epoxy from getting to the pump is not that difficult to implement and is adequate for low to moderate vacuum.

Deep vacuum, however, is probably impractical. Aside from the difficulties in containing the violently boiling epoxy, the heat generated by such a volume of curing epoxy drastically reduces the cure time. You are more likely to make some EG foam than you are to improve the strength of your EG.

[harryn]

Just stopping by to say hello. Also, I am now thinking about molding a timing belt pulley as a father / son project - should be a good learning experience for both of us.

[jhudler]

Checkout this patent application. Can you see how this would make mixing EG a WHOLE lot easier?!?!?
http://www.pat2pdf.org/patents/pat20140364540.pdf

Edit: I'm still going HOLY $&(^ Batman over this one. What concerns me is there is no prior art specified.

Edit: Speaking of vacuum in later posts; this would work very well with a moderate single stage vacuum pump.

[jhudler]

Just stopping by to say hello. Also, I am now thinking about molding a timing belt pulley as a father / son project - should be a good learning experience for both of us.

Be sure to use some sort of fiber material; fiberglass or carbon fiber (chopped or whisker). Though the later is a bit expensive.

BTW: What speed are we talking about? And what's it timing (hope it's not an engine)?

[jhudler]

I have done a lot of experimentation and testing of vacuum degassing and use it almost daily so I'd like to add my 2 cents to this deep vacuum discussion.

Just my two cents on vacuum.
I wasted... err make that spent a lot of effort on this subject years ago.

It's just not worth it; and like you discovered, it's only worth it for making small objects with that must be void free.

The cost in cleanup of your contaminated vacuum equipment will soon turn you off this method; it did me.

If by deep vacuum you mean into 1x10-3+ milli-torr range using diffusion or turbo pumps, then forget it, the outgassing will just overwhelm them and you'll never get them clean again. Also consider the state of your oil in the roughing pump and the ensuing damage that would cause.
All of this assumes you found a way to contain the outgassing from nucleating on the aggregate and foaming all over the place.

Just vibrate it long enough to deair and before any stratification sets in. Vibration doesn't have to be very aggressive.

As I discovered, de-airing agents are cheaper than vacuum oil.

[jhudler]

The recipe above is exactly what I used. #600 silicon carbide is dust. G200 zeeospheres are measured in microns.

How did this test out on your tension machine?

[thehairs]

I've read many, many pages of this topic and haven't found anyone doing what I'm thinking of doing. I'm want to make a granite, EG table for my 12 x 36 lathe over a steel base. I say granite,EG top because I am thin king of embedding long strips of solid granite counter top that I have roughed on all sides. about 80% of the casting would be these solid strips of granite.

Question: am I about to make an expensive mess or does this sound reasonable to give me a rigid base for my lathe.

Thanks
David Hair

[rowbare]

Checkout this patent application. Can you see how this would make mixing EG a WHOLE lot easier?!?!?
PAT2PDF - Free PDF copies of patents: Download and print!

Edit: I'm still going HOLY $&(^ Batman over this one. What concerns me is there is no prior art specified.

Edit: Speaking of vacuum in later posts; this would work very well with a moderate single stage vacuum pump.

Do you have the patent number for the above? The link doesn't seem to work any more.

Thanks
bob

[Low-Alloy]

Hello, ckelloug tried a PM but I am unsure if it got through, so here it is again.

Can you tell me the souces for the Hexion 813 and isophorone diamine hardener?

Did your last "batch" meet your strength expectations?

Sorry to have you bow out of the epoxy granite quest.

Cheers!

Low-Alloy

[mdfuller]

Application # 2014/0364540. POWDER COATING - Patents.com
or go straight to the source at uspto.gov 20140364540

Mark

[RotarySMP]

My first polymer concrete application will be a mount arm for my Deckel G1L engraver frame based mill. I looked at using Silimix 282, but the shipping from germny was prohibitive. I found a reference on this thread to Tomas Zietz spreadsheet for grading aggregate, dropped him a mail, and he sent me a copy. Thanks Thomas. Armed with a copy of GradingCurve.XLS, I had a look at what my local hardware store had which would be useful aggregate. From the garden section I got 4x 25 Kg bags as follows:

5-8mm pebbles - http://www.quarzwerke.at/datenblaett..._5,0_-_8,0.pdf
2-4mm crushed rock - (No data sheet - this stuff is sharp edged crushed rock for spreading on the icy footpath)
0.5-2mm quarz sand for improving your grass - http://www.quarzwerke.at/datenblaett..._0,5_-_2,0.pdf
0.1-0.3mm quarz sand for grout - http://www.quarzwerke.at/datenblaett...schichtung.pdf

Cool that the local quarry which supplies them publishes the datasheets with the screen sizes. Total cost of that 100kg was about €13.

I still have some very fine alumina from making a furnace, so that will be my finest filler. It cost €16,50 for 5kg from a pottery supplier.

Using the grading spreadsheet, it gives me the following recipe to make up a liter of Polymer concrete:

Grain 5 6,35 mm 100,00 26 % 259 ml 399 gr

Grain 4 3,00 mm 74,09 26 % 263 ml 403 gr

Grain 3 1,00 mm 47,74 20 % 203 ml 350 gr

Grain 2 0,25 mm 27,42 16 % 157 ml 243 gr

Grain 1 0,03 mm 11,74 12 % 117 ml 197 gr

100 %1000 ml 1592 gr

The two largest aggregates are wet, so I am drying some in the oven. I read that moisture has a very detrimental effect on E/G strength.

I think I'll whip up a long thin mould to make a 500mm long test bar, and once it is cured load it up and measure deflection to work out its youngs modulus.

[Well_Armed]

Hello, ckelloug tried a PM but I am unsure if it got through, so here it is again.

Can you tell me the souces for the Hexion 813 and isophorone diamine hardener?


Low-Alloy

Hi, All. I just read this entire mega thread. What an adventure it has been. I feel that most of my entire last week spent reading this was beneficial.

Low-Alloy, if you or anyone else has been given links to the sources for the materials he used for his experiments, would you please post them here? Or if you or he feels that would be inappropriate for some reason, PM me if that is acceptable? I feel a public posting in one link here at the end would really benefit the greatest number of people who would like to further continue his work and do some more mixing and pouring and start making some actual pieces that could be used and evaluated and documented. So much work went into his scientific approach to this material, it would be a shame to see it end so abruptly.

I know the aggregate materials are not too difficult to source, but the epoxy and hardeners and additives are quite obscure and very technical and whatever leads there are for sourcing this stuff would be greatly appreciated.

Kevin

[RotarySMP]

Yesterday I cast up a test piece. The plan was to make a bar 40x40mm. I am not sure where I screwed up as 40x40x430mm is 688ml volume. I made a 700ml batch of polymer concrete and it only filled the mould to 40x30mm.

The epoxy is a slow curing casting resin I got off ebay.de.

I put about 5g of carbon (laser toner) into the fine alumina. The total weight of aggregate was over a kg. The result is nice and black.

For this little batch I didnt use a swirl stirring attachment on a drill, but just mixed it by hand with a stick. The fine alumina needs to be sifted through a seive, as it takes lots of stirring to get the lumps out. mechanical stirring will be used for the next job. The alumina takes a lot of stirring to wet out. After that the next three aggregates mix in quite quickly, with just the last (the largest, again taking a lot longer to stir in and wet out.

I filled and rammed the mould with a stick. Ramming is not the right term, as hitting it hard is pointless. tapping at it sets up sum vibration which gets it moving though. Once it was full and sort of level, i spend a few minutes tapping the whole mould on the concrete, which was enough vibration to have the polymer conrete sag down and level out. Over a few minutes of tapping it a few bubbles surfaced and popped, but I can see how you need a lot more vibration to get good de-aerating.

To anyone trying this, putting a layer of packing tape on all surfaces of the mould, then dripping wax into the seams, which was then blended and smoothed with a soldering iron (only turned on intermittantly otherwise it gets too hot) worked really well. Demoulding only required the mould to be disassembled (screws) and then a sharp rap on the floor and the sides popped off.

There are a few small voids in the surface. The white you see on it is wax. Came out pretty good for a first attempt.

Now I will leave it on the heater for a week to post cure, and then clamp it with a DTI, load it up and measure deflection.
.

[NeoTech]

Did you use a casting epoxy or a laminating epoxy ?? =)

[rocketflier]

Hello, ckelloug tried a PM but I am unsure if it got through, so here it is again.

Can you tell me the souces for the Hexion 813 and isophorone diamine hardener?
Low-Alloy

but the epoxy and hardeners and additives are quite obscure and very technical and whatever leads there are for sourcing this stuff would be greatly appreciated.

Kevin

Hexion distributor list:

Hexion.com - Epoxy Distributor List

[gt40]

Recent academic studys on adding iron powder to epoxy granite and vibrating different epoxy granite mixes:

https://www.academia.edu/8322378/Inf...oxy_Composites

EXPERIMENTAL STUDIES ON COMPRESSION AND VIBRATION CHARACTERISTICS OF GRANITE EPOXY- AN ALTERNATIVE MATERIAL FOR PRECISION MACHINE TOOL BEDS | Chandan K M - Academia.edu

From the first study, I found the conclusion to be interesting:

"From the tests, it was observed that Granite Epoxy specimen with 12.5% resin content has excellent damping compared to other specimens containing different resin percentages. It has a damping ratio which is around 5 times more than cast iron. Also, it can be concluded from the vibration tests on Granite Epoxy with CI powder, that addition of CI powder to Gr-Ep composites increases the damping properties by a considerable amount. "