[walter]

Good stuff Sven.

The O shaped Koerner CNC frame looks great and should be popularized here on the Zone. Foolproof, easy to build and guaranteed to work - steel or E/G.

[greybeard]

Hi Walter.
Suddenly it's Christmas. The package arrived this morning - many thanks.
By the way, what's s1240, if I read it right ?

I've half completed the particle separator and realized that if I use a vac cleaner as the air mover I'm going to get an anomalous result ie the finest particles will finish up in the cleaner !
The distance each size particle travels will be proportional to its terminal velocity, and the vac idea will impart an acceleration, so it's back to the patentees original idea of a fan blowing the air through.

I planning a series of runs to see first if I can separate a mixture, then actually measure a sample particle size.
There are constraints on the method. It does assume the density is constant, likewise the particle shape, but I think it will allow me to produce the recipe mix as per "de L and C".
After that I want to go back to spinning samples, varying the spin speed.
I am a tad concerned that high speed spinning may be counterproductive. I'm not sure what movement there might be among the aggregate particles, lubricated by the resin and the cabosil etc. While I will go for the 10% recipe for maximum "lock-up", I wonder how different the high G force effect of spinning would be to the reciprocating effects of your vibration method.

Cameron - if I start producing spun cylinder samples, what would be the best set-up to test their tensile strength ?
I'm going to try to go with a constant volume sample to keep the cross-section as standard as possible.
I could go with my earlier posting of a simple test rig, but I'm not sure how to hold the sample, as it's a cylinder.
Any suggestions ?

Regards
John

[walter]

No Go on BYK C-8000.

Thanks, that saves us time and disappointments. For those unable to find coupling agent- just wash your aggregate in Isopropyl wound wash solution. Improves strength by 10% or so.

BYK A525- effect on mechanical strength still unknown, but it does seem to help in de-airing. In heavily stirred epoxy it pushes the air bubbles up and makes it bubbleless. Good stuff.

John, it's IMSIL 1240 microcrystalline silica. Datasheet: http://www.thecarycompany.com/products/Unimin.html

[ckelloug]

John,

The testing questions are hard. I haven't answered any of them satisfactorily yet. Let me think about it.

Walter,

While I'm thinking of it, the BYK A 525 deairing agent should be fine although I did not ask BYK.

--Cameron

[walter]

Real granite test results



It was no contest really. This Brazillian countertop granite is pretty weak, grainy and probably full of internal cracks. I repeated the test 13 times- in all cases granite went down at 5-7.5 ft*lbs. My best E/G samples did 20 ft*lbs for the beam and 20-30 ft*lbs for the bricks. I understand now why Starret charges so much for their granite bases. It's a different type of granite..

Here's what machine builders are using:

Blue Granite (France)—Excellent wear resistance due to presence of high grade quartz. Blue granite is used for very large structures.

Black Granite (South Africa)—Low thermal expansion and low water absorption. Black granite is used for most standard applications such as metrology surface plates.

Fine Black Granite—Excellent elastic modulus due to absence of quartz and good adhesion of grains. Fine black granite is used for small structures requiring high mechanical resistance.

Sample thickness: Granite 1.125", E/G 1.375"
_

[ckelloug]

Walter,

Excellent demonstration on the tests of real granite. Real Granite is quite weak in tension which is why a good sized surface plate is typically more than 6 inches thick. Your test here does prove to detractors however that there is a reason for this E/G madness as it really is tougher than the real thing.

I just checked the info I got from Dow on the Z6040 and the Z6020 and it appears that they are both backordered until tomorrow. If you're interested, PM me, and I'll trade you some bonding agent samples for some quartz samples when I get it.

--Cameron

[Xerxes]

Has anyone tried using vacuum to remove bubbles? It doesn't take very high vacuum to get the job done. However, in high viscosity stuff it might take a while and I think it works only if the stuff is pourable.

[ckelloug]

Xerxes,

There has been a lot of discussion about vacuum deairing of epoxy here. There is disagreement about how much vacuum is necessary but I think it would be fair to say everyone thinks it is a good idea. That being said, it is just expensive enough to try that few if any of the folks here have actually tried it. If the BYK-525 deairing additive proves effective enough for this, it is significantly easier than doing the mixing under vacuum.

If you have any hard data, please feel free to post it.

--Cameron

[Xerxes]

No need to do mixing in vacuum. Just put mixed stuff in vacuum for some time and bubbles come on the surface of liquid if it's not too thick. I have done some casting from PDMS material that way and it came out totally free of bubbles. The setup was really inexpenive, just a plastic container and a aspirator vacuump pump producing about 0.1-0.2 bar vacuum in the chamber.

[walter]

The mix is pretty thick.

This picture shows 16% epoxy mix -by weight. Pretty wet mix by E/G standards.

This comes to 20% by volume, and to get the max performance we need 8-10% by volume (we may not need it, but that's where the commercial performance is).

It will be almost powder dry.
_

[Xerxes]

I think it would be way too thick for bubble extraction by vacuum. :/

[ckelloug]

The mix is pretty thick.

This picture shows 16% epoxy mix -by weight. Pretty wet mix by E/G standards.

This comes to 20% by volume, and to get the max performance we need 8-10% by volume (we may not need it, but that's where the commercial performance is).

It will be almost powder dry.
_

I'm predicting that the 8% power dry mixture will behave rather poorly until vibrocompacted. What I can't figure out is whether it might actually have to be constructed in the mold by alternating epoxy and aggregate layers. As long as the material compacts to the proper density, it won't matter if there is a pool of epoxy on top, as long as it isn't distributed throughout the material.

Two cents worth of hypothesis for your perusal.

--Cameron

[lgalla]

Walter the commercial mixes of 8to10% are by weight.
Me Tripoly on additives.
Are wetting agents surfactants?Surfactants reduce surface tension.
May also be named:
orange peel eliminator
crater eliminator
fisheye eliminator
ZZ Top Eliminator.
Coupling agents are adhesion promoters or wetting agents??
Silane treatment seems to be available on the cheaper fillers such as clays ATH and wollastanites.
Epoxy appears to be its own surfactant as just before gell it wets or flows like crazy.
Aunty foaming agents claim bubbles burst by themselves.Why?
Adding every additive in the book may be counter productive.Best to ask the experts at BYK or DOW.
Larry

[walter]

Walter the commercial mixes of 8to10% are by weight.

How do you know that?

[lgalla]

Walter this is what I read in the last 2 days on the engineered stone.It stated all brands are 93% quartz and 7% resin and additives,but don't be fooled it is by weight.Did not bookmark the page as I thought everyone knew this.(chair) Sorry can't find the page.
Found other info searching.Engineered stone is heavier than granite as granite only contains only 40to60% quartz.
Larry(chair)

[walter]

Thanks.

I did the calculations and 7% epoxy by weight equals 8.75% by volume. Still awesomely low, as I'm currently working with 20-25% mixes (by volume).

[lgalla]

CaesarStone® (made in Israel) [see their website]

CaesarStone® it is made of approximately 93% quartz by weight. The other 7% is epoxy resin which is required to hold the quartz together. Quartz is one of the hardest minerals and is calculated at a hardness level of 7 on the Mohs Scale of Hardness.

C

[lgalla]

another copy:

• Engineered Stone (ES) is comprised of ground up granite dust mixed with coloring and epoxy to hold it together. These companies will tell you that ES is 93% stone, 7% epoxy. What they won’t tell you is that these percentages are by weight, not volume. As granite is much heavier by volume than epoxy, the actual stone to epoxy ratio is closer to 75%-25%.:

I think,Walter you have been in the ballpark all along.The 93% is marketing all brands are 93%,no bacteria,safe for children and pets and other marketing BS.
Info is hard to find.Engineered stone is 48.2kg/m2,20mmthick.The metric part of my brain is not working.Is this useful?

[ckelloug]

Walter the commercial mixes of 8to10% are by weight.
Me Tripoly on additives.
Are wetting agents surfactants?Surfactants reduce surface tension.
May also be named:
orange peel eliminator
crater eliminator
fisheye eliminator
ZZ Top Eliminator.
Coupling agents are adhesion promoters or wetting agents??
Silane treatment seems to be available on the cheaper fillers such as clays ATH and wollastanites.
Epoxy appears to be its own surfactant as just before gell it wets or flows like crazy.
Aunty foaming agents claim bubbles burst by themselves.Why?
Adding every additive in the book may be counter productive.Best to ask the experts at BYK or DOW.
Larry

Wetting agents = surfactants. Surfactants modify surface tension which is a component of a more general concept called surface energy. A solid will be wet by a liquid if the solid has a higher surface energy than the liquid. Epoxy has a somewhat lower surface energy than quartz but the surface energy goes up as the epoxy sets. The greater the difference between the surface energies, the faster and more effectively the solid is wet by the liquid.

Based on my understanding of the physics, that viscosity drop right before the epoxy becomes rigid makes the epoxy flow but the material has a high surface energy at that point and isn't very inclined to entrap more particles, it just wants to escape where it is. If a surfactant is added, the epoxy has a much lower surface energy than the quartz for the whole setting period and is more likely to continue to flow around the particles during the whole setting process. This paragraph is a hypothesis based on the data I've seen and a weak statement in the 3M novec 4432 fluorosurfactant data sheet that corroborates it.

Coupling agents effect epoxy wetting some by binding chemically to sites on the aggregate and presenting more favorable functional groups for the adhesives to bond to. Coupling agents also do things like reducing the affinity for water possessed by the aggregates. The generic silanes used on silica fume and other fine particles are designed to lower the water affinity of the particles and to improve dispersion as opposed to coupling them to an adhesive.

Like was pointed out by DAK3333 or harryn, one big problem is that aggregate have a layer of water molecules on their surface because they are slightly hydrophilic. This plays havoc on epoxy sticking well. The solution of Washing in Anhydrous alcohol gets rid of the water molecules which act as an anti-coupling agent. The remark about washing in alcohol being as good as silanes was made on the assumptions of silanes with only hydrophobic properties, not for the additional chemistry of the dow corning silanes selected with epoxy groups to bond directly to aggregate.

I assume aggregate also tend to have a layer of adsorbed air which leads me to believe that treating the aggregate under high vacuum to get rid of adsorbed air and water would probably be optimal before silane treatment if cost were no object.

Coupling agents like the Dow Corning Z6040 and the Dow Corning Z6020 work like soap reacting with grease. To complete the analogy, soap works by having one end of the molecule that is highly non-polar and dissolves in grease while the other end is highly polar and forms hydrogen bonds with water. The difference between the dow corning products and soap is that the dow corning products have a silane end that sticks to the aggregate while Z6040 has an epoxy group on the other end. (Z6020 contains an amine group instead) The silane chemically bonds itself to the aggregate while the epoxy or amine group rigidly and chemically links into the epoxy matrix forming a chemical bond directly between the epoxy and the aggregate. The Dow corning products are essentially copolymers and can either be directly added to the epoxy as copolymers or preferably used to pretreat surfaces with which a good bond is desired.

Deairing agents are similar to defoaming agents. They work kind of like adding extra grease to a sink full of dish soap until the molecules are so busy dealing with the grease that they don't form bubbles any more. The magic of a good deairing/defoaming agent AFAIK is that it doesn't greatly effect the surface energy/surface tension of the liquid, it just makes bubbles less favorable. They also sometimes act as non-reactive dilutants that evaporate out of the system without harming the chemistry.

There is probably some number of additives that's too many but I am currently planning to use 3m Novec 4432 surfactant, BYK A525 Deairing Agent and Dow Z6040 coupling agent to pretreat aggregates. Each of these chemicals has a different role to play and different mechanism of action so I don't think there should be a problem. The data I got from reichhold and BYK suggest that some commercial applications use cocktails of several different deairing agents so this seems natural to me.

So in answer to Larry's question, I suppose their is a remote chance of novec 4432 interfering with BYK A525 but neither will interfere with Dow Z6040 or Z6020 coupling agent.

I am curious about Larry's number for epoxy content in commercial products. From the fact that all of the physics of the mixture is based on volume fractions, not weight fractions, I'd assume that the 8% number must be by volume rather than weight. I can't prove that it's by weight but it seems like the rule of mixtures graph I posted shows that the 8% by weight mixture wouldn't be near as strong as desired.

:cheers:

Cheers to Walter for being close to building something!!!

--Cameron

[lgalla]

QUOTE:Steel would have been a better choice - cast aluminum sustains like a $3k Gibson Les Paul (For the uninitiated- it's 14 seconds ).:
LesPauls are for sissys.Anyone sounds good on an LP.Strats are for the real players.You gotta fight a strat to be good.my;62 strat could sustain 20 minutes with 2AMPEG v-4'S AND 2-4 TWELVES ,BTW I got 20KUS on E-Bay for my Strat,much more than a 3K les Paul.
Larry