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IndustryArena Forum > Mechanical Engineering > Epoxy Granite > Epoxy-Granite machine bases (was Polymer concrete frame?)
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  1. #1561
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    Someone mentioned Harbor Freight earlier. I visitied the store and found $70 paint pressure pot- 2.5gal, 80psi max. I might try (to implode) this thing.

    btw, Did anyone try to inject their bisphenol-A epoxy with acrylonitrile butadiene styrene? Seriously..Is there anything I should know before attempting it?
    Where is the Chemist when you need him...

    Anyway.
    Folks, I think we're pretty close to wrapping it up. I think I've seen the light. Cameron's right about silyating, won't do without it. Viscosity problem will also soon be solved. The rest is simple.


    And this may be the last piece of the puzzle (let me know what you think):

    http://www.mrs.org/s_mrs/sec_subscri...&action=detail

  2. #1562
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    Walter,

    If the ABS datasheet doesn't look too dangerous then about all that could happen is that you get goo or the hardener to resin ratio has to be adjusted. If the folks over at the cary comapny sent you that direction, hopefully they left you a few pointers while they were at it cause that's new territory for us.

    Not so sure about the rubber tougheneing idea for this application. Rubber has a low modulus so the resulting material will be somewhat floppy for some definitions of "floppy". If the impact strength etc. are an issue, switching aggregates from granite/quartz to alumina or zirconia or perhaps garnet will work better as these aggregates are also very stiff in addition to being hard to break. (AS best I can determine, fracture toughness is more important than aggregate shape in making the material tougher). Tank armor is a metal ceramic composite for a reason: Fracture toughness of polycarbonate (Lexan) is 3.6. If you've ever tried to bust a piece, you know what I mean. On the other hand, fracture toughness of zirconia ceramic is 11, aluminum is 30!

    Larry,

    Sorry if I was sounding arrogant or anything about thixotropes. I actually find the thixotrope idea specifically interesting based on greybreard's spin casting idea and I wanted to see if I could apply your advice on previous comments on thixotropes to what I was thinking about spin casting of parts. For me, I might not ever be able to implement the spin casting idea but it's a good academic exercise for me.

    There is nothing wrong with backyard technology. I am just trying to help us all cheat a bit in it's creation by sharing my 4.5 years of being tortured in engineering school to help design the ultimate backyard technology. I also happen to like to study all aspects of problems, even the useless ones so hopefully you can all bear with me when I digress.

    As for silica fume, from what I understand, the percentage needed is relatively low to achieve the hardening effect the literature talks about.

    Kudos to Mazaholic and Larry for making some progress on the vacuum stuff.

    <B>DAK3333 and harryn and any chemists out there with comments about adding ABS monomer to Bisphenol-A epoxy with Alkyl Glicidyl Ether and amine hardeners would be very much appreciated by walter. et al.!!!</B>

    Regards to all,

    Cameron

  3. #1563
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    Quote Originally Posted by ckelloug View Post
    <B>DAK3333 and harryn and any chemists out there with comments about adding ABS monomer to Bisphenol-A epoxy with Alkyl Glicidyl Ether and amine hardeners would be very much appreciated by walter. et al.!!!</B>
    Cameron
    Not specifically, but is this aspect related to the article on Ductal advanced concrete mentioned way back, on the effect of including microfibers like PVA(!).
    Apparently a degree of toughness is acquired by the energy being absorbed by the fibers slipping slightly in the matrix. I was surprised by the inclusion of what I would have thought of as a weak fiber in the matrix should increase the toughness. But there, of course, the problem is brittleness of the cement component, whereas with E/G the function of the epoxy is as an adhesive.
    But am I overlooking the fact that fully cured epoxy might actually be quite brittle, a situation that may not have been achieved yet.
    It's like doing jigsaw puzzles in the dark.
    Enjoy today's problems, for tomorrow's may be worse.

  4. #1564
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    Quote Originally Posted by ckelloug View Post
    Hi all,

    I just put in a sample request at 3M for some Novec 4430 and 4432 fluoro surfactants. These surfactants should cure problems that are related to the ratio of the surface energy of the aggregates to the surface energy of the epoxy. I've decided to "come clean" and get some of RancherBill's hi tech soap
    Cameron

    I was spraying weeds and was impressed by the foam in the tank. I remembered someone had told me a surfactant (soap) was added to break down surface tension so that it would cover better. I remembered you were having "wetting" problems.

    You guys are all GIANTS in DIY "New Tech" machine building. I am just happy I could contribute a small idea to this thread.

    :wave:

  5. #1565
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    Rancher Bill,

    Slightly OT, but foam is another problem that can be controlled.

    I have three bottles of Dow Corning Silicone defoaming agent that I acquired for another of my projects a few years back. I haven't used it yet but it's amazing what a single drop of these additives will do according the the books. They're often added in vanishingly small quantities to ordinary soap so it doesn't foam but still cleans. Technically, they're anti-soap and work on the opposite principle of soap but they raise surface tension more than they lower wetting ability.

    Thanks for posting your suggestion on surfactants. It was excellent advice on trying to actually try to get somewhere.

    As for everyone else, if you think of anything, post it. It's not as if I knew anything about E/G specifically when I started. It's through running the ideas in the first 800 posts to ground and using my training in engineering that I learned what I know about E/G and started posting. I'm not an expert on any of the aspects but by training, I am an expert in piecing together knowledge from many sources. While I post a lot of stuff here, the majority of it is just following different poster's suggestions to their logical (or illogical according to some) conclusion.

    Cheers, RancherBill and everyone. This is too much fun to not finish into a product.

    --Cameron

    P.S. A forklift just finished delivering my 9x36 Bridgeport mill and a 14x40 Birmingham lathe. Also put the rollup door up. No electricity in the building yet but it's a start!

  6. #1566
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    Quote Originally Posted by lgalla View Post
    Where is Andrew,He seems to understand my backyard technology.
    Larry
    Hi Larry, been busy... This thread has developed an interesting character.

    Language and technology; Maybe engineering is taught differently over here but my schooling emphasised keeping things simple and in plain english where ever possible. Arguement was there's often too much jargon, language misused, pseudo engineering and other abuses of the english language to complicate life as it is. Then again we'd fail a term paper if there where any grammer or spelling mistakes too.

    Your comments seem plain and informed to me.

    Drop me a pm if you have a question.

    Andrew

  7. #1567
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    Toughness

    Quick comment on 'toughness' as it was applied to the idea of increasing epoxy's toughness by adding resilient rubber or similar compounds.

    I get a completely different read on the issue; the resiliant (rubber or whatever) materials are added to make the epoxy adhesive less likely to fail and not to make it stronger.

    Epoxy is (usually) brittle in its strongest and fully hardened state when used as an adhesive. Brittle hard epoxy will break or fracture under loads or impacts where a softer more resilient epoxy would not. The epoxy is softer and so tougher in a given circumstance.

    Toughness is this context is the ability to work better in a given situation and not a measure of hardness or strength, tensile or flexural.

    To add 'tougheners' to the e/g mix as suggested is actually the reverse of what's being sought in this thread.

  8. #1568
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    Andrew,

    I think I understand that rubber is being added to the mix to increase the resiliency and decrease the likelihood of failure. My best understanding is the mechanism of action for that is that the fracture toughness parameter K_IC is enormous for rubber although the modulus is not very high.

    My comment on the matter in polite disagreement with John was that rubber will be good for the toughness of the material but that the modulus will be lowered. My suggestion was that rather than add something that lowers modulus and has a high fracture toughness K_IC, why not use an aggregate that has a much higher value for K_IC than was being used initially and thus boost the toughness by using materials which also have a very high modulus.

    If you disagree with my idea here, please post why as those are the kinds of things that are more valuable than ideas themsleves.

    For the record, I have considered this a complicated problem because I am not an expert and have read materials science textbooks and journals to get near up to speed. I have used fracture toughness as opposed to Izod or Charpy data because it is a material parameter pertaining to the energy in crack growth rather than an empirical measure. K_IC is not a popular measure in concrete engineering as they had usable concrete since the romans and mathematical formulas for aggregates since the turn of the twentieth century but it is never-the-less an intrinsic material parameter. For some of the aggregates like garnet, the only published paper on K_IC for them I could find was published in the journal American Minerologist less than three months ago. There is a schism between concrete engineers who need to build bridges today using traditional empirical measures and materials scientists who want to build stronger bridges tomorrow using more fundamental but different measures. The most interesting work in bridging this gap to pardon the pun is being done by the Aggregates Research Institute at the University of Texas and a French scientist named de Larrard.

    So, Andrew, despite the disagreements we've had in the past, I'm glad to see you back and hope that you will post here if you think anybody here has said something that wasn't right. I agree with you and Larry that simple is ultimately better, I've just been going through all of the parameters I can identify on this problem and posting thoughts as a lot of interesting people respond so that ultimately home E/G can be something easy like: put 2 lbs of sieved aggreagte in a bucket; add 1/2 a pound of epoxy, half a pound of hardener, and an ampule of "make it work additive(TBD)"; stir and pour.

    Best Regards,
    Cameron

  9. #1569
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    My local boat shop supplies Epiglass 9000 as low viscosity resin.
    It has no solvents, zero VOC, and from the manufacturer(?) International Coatings Ltd, I've received a useful .pdf file aimed at the pro builder.
    It gives the viscosity as 800cps for the resin and 100cps for the hardener, which are mixed in the ratio of 4 : 1 by volume.

    Is there a way of approximating the viscosity of that mix immediately after mixing, and before it starts to cure ?
    This would help in deciding how useful a starting point this epoxy would be, or should I be looking for something with a much lower figure for the resin ?

    John
    It's like doing jigsaw puzzles in the dark.
    Enjoy today's problems, for tomorrow's may be worse.

  10. #1570
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    Thinning Epoxy

    OK - this is going back a long way since I seriously worked with this stuff but Thinning Epoxy is a hugely controversial subject that needs to be understood if anyone wants a strong result.

    Any solvent dilution will make the hardened base material more rubbery and reduces its compressive strength.

    Basically the raw epoxy material is nasty, toxic and thick stuff. Usually >3000 cps. To get it thinner than that with hardener various dilutants are used. When you use dilutants the base material strength is usually reduced, sometime significantly. When you use solvent dilutants it gets much worse.

    Manufacturers info; I've recently used about 10 gallons of West System 105 with 205 hardener. The datasheets from Gougeon Brothers includes info about viscosity and thinning the stuff. A 5% laquer thinner dilution will take the viscosity from 750cps (800cps base, 100cps hardener) to under 250cps at 70f or around a 60% reduction in viscosity. Great? No It's Not because once hardened the compressive strength is also reduced by 35% to around 5500 psi.

    In boat building where most of the layup is in tension the compressive strength is irrelivant and the greater flexibility is desireable. In a machine base where you want stiffness in compression that would be a problem.

    Thinning Epoxy with Heat: The viscosity of epoxy is very sensitive to changes in temperature, and warming the components (resin and hardener) and/or the substrate substantially lowers its viscosity. Commercially this used to be done by heating resin and hardener seperately and mixing at temp. Again 105/205 mix info shows 2500cps at 55f, 1000cps at 70f and 250cps at 95f. Once hardened the material retains full strength.

    Problem here is epoxy is a thermosetting polymer. Warm epoxy cures much more quickly than cold, excessive heat will cause the epoxy to harden too fast, especially in thick applications. Very rapid cure will overheat the epoxy and damage it. I've had 105/205 at 90f go off in 3 minutes.

    Of more concern is that, unlike polyester with a catalyst hardener, epoxy forms the chains from both the base and hardener. BTW The commercially available components already have sufficient 'nano' strength enhancements from the formulator of the epoxy since the chains wouldn't start reliably otherwise. With heat the polymerisation reaction runs faster than without, the bonds are made when the material is liquid with its viscosity increasing until it gels, after that the reaction slows. The gel stage duration often determines the material strength. If it's too hot during gel setting the material will have a variable consistancy of bond and hence material properties. Autoclaving the material is as much to obtain a consistant strength as it is to complete the gel stage and convert all remaining amines into bonded sites.

    Getting full solids high viscosity epoxy to work in a large mass needing a low viscosity isn't currently practical. That's why prepreg carbon was developed. The epoxy and hardener are in particle form impregnated in the cloth at full solid undiluted form. keeping it frozen delays the cure. Heating it releases the mix and the whole thing cures in place.

  11. #1571
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    John,

    Shooting from the hip with no supporting data other than intuition, I'd suggest that the weighted average would probably be the viscosity you need which would work out to 660cps.

    If the epoxy they sell is a good deal, it's likely good. If your having source trouble, you might want to talk to the apps engineer at Huntsman advanced products in the UK as they might be able to give you a deal on 5 gallons of exactly what you want via their samples department. Numerous research papers I've seen used their off the shelf resins. I've had a nice chat with one apps engineer despite my asking a question so stupid I'm not even going to post it here.:withstupi

  12. #1572
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    Andrew,

    Do you have any comments on reactive dilutants? The Reichhold epoxy that walter and others are getting here in the states from us composites (and I shall soon get) is diluted with glycidyl ether with a chain length of 12 to 14 carbons. A quick data sheet ( I posted it a few posts back) check suggests has one epoxy group on it. Reichhold suggests in their data sheet that this material participates in the chemistry enough to bond but since there is only one epoxy group per molecule instead of more it doesn't crosslink contributing to poor strength at high temperatures. They also publish formulations which indicate that more glycidyl ether than is in the epoxy we have is used for materials like iron oxide filled self leveling floor compounds and they show making epoxy that goes down to about 200cps.

    The few drips of epoxy manufacturer guidance I've read are in total agreement with you that non-reactive dilutants like lacquer thinner are bad for compressive strength and modulus.

    As for nano-reinforcement, can you expound a bit more on what is in there already from the start? I've seen a few papers on adding silica fume and epoxy-dispersed sol-gel silica from www.nanoresins.com all with particles less than .1um in academic papers. The stuff from Nanoresins gives enormous results according to the published papers from just a few percent and the effect goes up until about 13 percent and then levels off.

    Regards,

    Cameron

  13. #1573
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    Cameron. So called reactive dilutants are after my time really so I can't decently comment from first hand.

    So, this is probably totally wrong but I'm confused. If they are really using glycidyl ether as a dilutant there's a lot more than simple dilution going on. Hence the 'reactive' I expect. I thought it was the glycidyl groups open on the base that reacted with the hardener amines to form the links and so cure the resin?

    Amine blush is an excess of amines in the proportion of hardner. Non blushing epoxy carefully provides exactly the quantity of amines in th ehardener necessary to fully cure - which is why it's so vital the mix ratios are observed. Excess hardner - too many amines, you get blush, too fast a cure and possible encapsulated unconverted base and a sticky surface and weak product. Too little hardner you get unconverted base and insufficient cross linking and a rubbery product.

    If they're adding G ethers then I'd have thought amine could bond there as readily as the base string and the ethers evaporate off. Isn't that a VOC these days? What's the base/hardener ratio? Does the thinner stuff need more hardener? What's the mixing criteria? If the hardener has to bond with both base and a reactive dilutant it's going to be even more important to have a homogeneous mix and exact ratios.

    Nano mixes; I think you're wasting time on so called nano particles since the benefit in strength is limited in value until you 1/ get the base material to perform as per datasheet, 2/ have a need beyond what's simply feasible with the material properties as is and finally 3/ can be assured the 'additives' will not have a detrimental effect.

    Epoxy is a fairly complex material, or rather the hadener is. The base resin is pretty much unchanged from one brand to another. The formulation chemistry happens mostly in the hardener and tailors the materials properties including things like strength improvers. Its complex and to get beyond the base physical properties is not trivial. Formulators can make fast or slow, clear, non blushing or brittle or soft epoxies. Where you see 100% solids usually implies the mix isn't diluted, or rather I'd guess that means its not using VOC's these days. To get the stuff to fully cure in chains and extensive cross linking usually requires particulate solids in the base and particulates in the hardener. This is analogeous to the proposed Nano particles I suspect and the papers on the benefits are simply a refinement of whats already in there. particles are already in there that in part is what the '100% solids' refers to (or at least it used to!).

    It gets tricky where circumstances require a formulator to provide a property that requires addition of a material that material is itself a particulate in larger quantities, not liquid and the formulator then has to counter excess small ( or nano to use the jargon here) particulate that cause cure problems, similar to the Carbon black goo effect for example. If there already a lot or particulate in there, adding more material will weaken the product.

    Again my experience here is over ten years old so take it for what its worth, and it relates to resin infusion and prepreg mixes in mixed fibre laminates, mostly tension stuff as structural composites usually are. The exact opposite of E/G property wise unfortunately. The basic rules to the base materials still apply though.

    Also to be honest, dilutants, nano this, filler that are all irrelevant in the bigger picture for Epoxy as an engineering material. If you can get a low cps epoxy formulation then the first challenge is still to get the stuff to perform as per datasheet first. Once that's there it's almost trivial to work out the sections required.

    As an end user with a non bleeding edge application I'd be hesitant to expect to be able to modify the mix without a lot of tangible effort and moreover simply don't see the need.

  14. #1574
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    Epoxy sticking to Epoxy?

    Seems Epoxy doesn't stick to Epoxy? Have to disagree. It works fine, as long as the material is used to its strengths. If you disagree you might want to worry next time you get on a 777.

    As people have read ad nauseum epoxy cures with polymers bonding in all directions. The bonds are from 'plugs' and 'sockets' in the hardener and the base materials. An ideally cured epoxy will be fully bonded with few external bonds available. In part thats why epoxy cures to a smooth surface.

    Surface energy was mentioned, cured epoxy has low surface energy sure, that is not much sticks to it, but surface energy ignores that epoxy is unusual as a material in that it's formulation has a very small and chemically specific subset of available bonds specific to the hardener anyways.

    So what? Well Epoxy is a mechanical adhesive not a chemical (etching) adhesive. It works on the monkey with its hand stuck in the jar, or climbers camming piton principle. Most materials have a surface with sufficient surface voids for epoxy to enter and cure bonds within so locking to the surface.

    Epoxy can have a smooth finish that has fewer mechanical voids, worse when cured has a surface amine layer which works like a release agent, and even without those has low surface energy so direct bonds are few.

    Epoxy to Epoxy adhesion works fine if you provide a high energy non amine surface by applying the second batch to the first before its fully cured. It also works fine if you provide mechanical key either by molding or more commonly by sanding to expose a less smooth surface or the layup.

  15. #1575
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    Quote Originally Posted by fyffe555 View Post
    Cameron. So called reactive dilutants are after my time really so I can't decently comment from first hand.

    So, this is probably totally wrong but I'm confused. If they are really using glycidyl ether as a dilutant there's a lot more than simple dilution going on. Hence the 'reactive' I expect. I thought it was the glycidyl groups open on the base that reacted with the hardener amines to form the links and so cure the resin?
    I'm not sure about the glycidyl groups. I'm still skimming the surface on epoxy chemistry and haven't dived into the deep end yet. Some assume I'm off the deep end however.

    Now that I've finally trained my fingers to type Glycidyl ether accurately, I was finally able to google for it and get something on the first try rather than trying to figure out where the I's and Y's were for five minutes. They are definitely using Glycidyl Ether which is verified form the Reichhold datasheet for material <A href="http://www.cnczone.com/forums/attachment.php?attachmentid=38269&d=1180623213">37-127</A>

    Here's a sheet describing the Glycidyl Ether <A href="http://www.chemicalland21.com/industrialchem/functional%20Monomer/n-BUTYL%20GLYCIDYL%20ETHER.htm"> Glycidyl Ether Structural Diagram and Properties</A>

    The proper International Union of Pure and Applied Chemistry (IUPAC) name for Glycidyl ether is
    Butyl 2,3-epoxypropyl ether
    <BLOCKQUOTE>
    Diluent is an organic liquid added to resin formulations, , with no solvent power, to reduce viscosity and to ease flow movement or to improve the consistency and applicability. Typical applications would be for the manufacture of paints, lacquer, varnishes, adhesives, and coatings. Thinner's function is to make the application simple only and must evaporate after application. The term of diluent is also used in solvent system as an inert substance added to some other substance or solution so that the concentration volume is decreased.

    n-Butyl Glycidyl Ether, monofunctional glycidyl ether of butyl alcohol; containing epoxide group ( three-membered ring cyclic ethers that are also known as oxiranes or alkylene oxides). It is used as a general purpose diluent to reduce viscosity of epoxy resins, favoring improved filler loading and substrate wetting and resulting in faster curing time. End applications include coating, adhesive, casting, laminating, encapsulation or foam. It is also used as a stabilizer for chlorinated vinyl resins and rubber. It is used as a chemical intermediate to make other compounds.
    </BLOCKQUOTE>

    So, the hardener actually cracks an epoxy bond on this stuff and at least part of it becomes part of the material.

    Quote Originally Posted by fyffe555 View Post

    Amine blush is an excess of amines in the proportion of hardner. Non blushing epoxy carefully provides exactly the quantity of amines in the hardener necessary to fully cure - which is why it's so vital the mix ratios are observed. Excess hardner - too many amines, you get blush, too fast a cure and possible encapsulated unconverted base and a sticky surface and weak product. Too little hardner you get unconverted base and insufficient cross linking and a rubbery product.
    That's good info, Andrew. Larry touched on this back in <A href=http://www.cnczone.com/forums/showthread.php?p=283185?postnum=855> Post 855</A> but he more mentioned that it was a bad thing.

    Quote Originally Posted by fyffe555 View Post
    If they're adding G ethers then I'd have thought amine could bond there as readily as the base string and the ethers evaporate off. Isn't that a VOC these days? What's the base/hardener ratio? Does the thinner stuff need more hardener? What's the mixing criteria? If the hardener has to bond with both base and a reactive dilutant it's going to be even more important to have a homogeneous mix and exact ratios.
    It makes a lot of sense that it might require very good mix ratios. It could be a VOC, but it doesn't ship hazmat. Those using it are purchasing this stuff as Epoxy 635 from www.uscomposites.com. The mix ratio is 2:1 with their slow hardener which is Reichhold <A href="http://www.cnczone.com/forums/attachment.php?attachmentid=36170&d=1177623183">37-606</A> amine hardener. They were kind enough at U.S. composites to give us the Reichhold part numbers. Other than mixing accurately, they give no specific guidance on why this is harder to use than other epoxy. I'm sure however that the mix ratio is effected as the amount of dilutant changes. The 37-127 epoxy comes from Reichhold with the G. Ether already added.

    Quote Originally Posted by fyffe555 View Post
    Nano mixes; I think you're wasting time on so called nano particles since the benefit in strength is limited in value until you 1/ get the base material to perform as per datasheet, 2/ have a need beyond what's simply feasible with the material properties as is and finally 3/ can be assured the 'additives' will not have a detrimental effect.
    I'll be investigating this shortly as my main reason for not doing so what that my shop lacked a door until this morning and made me not want to put anything in it. I agree with point 1 in this paragraph that until we get our epoxy to behave to datasheet specs that nothing else is worthwhile. I've got mixed feelings on point 2 because the effect cited in one case by the paper that was testing the heavily engineered nano particles (particles literally on the order of nanometers) from Nanoresins actually found 2 orders of magnitude as the improvement in modulus.

    Two orders of magnitude: that's not an improvment, it's effectively a different material. If some less pronounced but significant effect is available with some silyated silica fume or carbon black, the materials are so cheap that for personal use, it's worth doing it in the same way that building your computer with blue LED's and acrylic sides is worth doing. (I have seen papers about similar less pronounced effects to the Nanoresins material from the silica fume institute about regular Portland Cement concrete as well as recently published engineering handbooks and the paper by de Larrard). Since it's only in the last few years that epoxy aggregate composites have regained commerical interest (they were last interesting when I was born), I'd go out on a limb and say that at least some of the theories that I/we have been trying to apply here, while validated on other problems, haven't been applied to epoxy aggregate composites yet since I've not found papers. It's also possible that they are trade secrets of some of the companies doing epoxy granite machine parts.

    Finally on point 3, anything can go wrong but I've seen enough data to believe the theory of nanoparticle (less than .1 micrometer) reinforcement is airtight albeit, it is theory that has occurred since the 1980's and has in some cases been applied more by scientists than engineers. I came to this point from reading the polymer composite chapter of my materials science book from when I took the class in about 1995. As for silane based bonding agents, silane based deairing agents, and recently invented fluoropolymer surfactants, it's anybody's guess except that the manufactuer data sheets all cite reasonable and specific property improvements to be had with examples in commercially available raw materials.

    Quote Originally Posted by fyffe555 View Post
    Epoxy is a fairly complex material, or rather the hadener is. The base resin is pretty much unchanged from one brand to another. The formulation chemistry happens mostly in the hardener and tailors the materials properties including things like strength improvers. Its complex and to get beyond the base physical properties is not trivial. Formulators can make fast or slow, clear, non blushing or brittle or soft epoxies. Where you see 100% solids usually implies the mix isn't diluted, or rather I'd guess that means its not using VOC's these days. To get the stuff to fully cure in chains and extensive cross linking usually requires particulate solids in the base and particulates in the hardener. This is analogeous to the proposed Nano particles I suspect and the papers on the benefits are simply a refinement of whats already in there. particles are already in there that in part is what the '100% solids' refers to (or at least it used to!).
    This is an interesting description of how epoxies work but it isn't the reaction mechanism in play with the nano-particles I'm talking about; (less than .1 um) it's another mechanism. The technique on nano-particles I've been describing are tiny particles on the order of the size of the crystal lattice of the matrix.

    The effect is called dispersion hardening. Current applications of this are metal-ceramic particle composite machine tools, carbon black in vulcanized rubber, and pozzolans/silica fume in portland cement. The effect has nothing to do with epoxy other than the fact that it is a crystalline solid at room temperature and that deformation by dislocation slippage is a fundamental deformation mechanism in crystalline solids.
    [/QUOTE]

    Quote Originally Posted by fyffe555 View Post
    It gets tricky where circumstances require a formulator to provide a property that requires addition of a material that material is itself a particulate in larger quantities, not liquid and the formulator then has to counter excess small ( or nano to use the jargon here) particulate that cause cure problems, similar to the Carbon black goo effect for example. If there already a lot or particulate in there, adding more material will weaken the product.
    I'll be working on the carbon black goo effect first in my almost completed lab as my trip to the library checking a composites materials handbook indicated that the main problem should be a cure time increase due to adsorption (yes, the second letter is a d) where the hardener molecule is held loosely in chemical terms by the particle by not bound permanently. Absorption (with a b) of the hardener on the other hand would cause a permanent and fatal cure problem requiring a mix ratio change. I need to identify which is which mechanism it is and if it's the second, move to a less reactive nanoparticle.

    Again my experience here is over ten years old so take it for what its worth, and it relates to resin infusion and prepreg mixes in mixed fibre laminates, mostly tension stuff as structural composites usually are. The exact opposite of E/G property wise unfortunately. The basic rules to the base materials still apply though.

    Also to be honest, dilutants, nano this, filler that are all irrelevant in the bigger picture for Epoxy as an engineering material. If you can get a low cps epoxy formulation then the first challenge is still to get the stuff to perform as per datasheet first. Once that's there it's almost trivial to work out the sections required.

    As an end user with a non bleeding edge application I'd be hesitant to expect to be able to modify the mix without a lot of tangible effort and moreover simply don't see the need.
    I disagree with your theory on nanoparticles but defend to the death your right to say it. I don't mind the effort or the expense in in figuring out how to optimize this, I've already got about $200 in books relating to my work on this topic and haven't even started buy resin. My goal here is to learn as much as I can about this topic and disseminate it as it increases the knowledge I have available to apply to other problems and hopefully will help the abstract goal of making more machine tools available to the masses.

    All that being said, you have a lot of good info.

    Regards,

    Cameron

  16. #1576
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    Quote Originally Posted by fyffe555 View Post
    Seems Epoxy doesn't stick to Epoxy? Have to disagree. It works fine, as long as the material is used to its strengths. If you disagree you might want to worry next time you get on a 777.
    I'm not afraid of the 777 but I did misspeak unintentionally and you called me on it. Others on the thread including Larry have said that after a certain time period after epoxy is cured, the surface is still somewhat chemically active and will crosslink to some extent with the next pour. There is some point in time where this doesn't happen and this is the point I failed to articulate while your post did a masterful job of explaining it.

    Thanks for your explanations here,
    I think our Socratic Dialog here may actually clear some confusion.

    --Cameron

  17. #1577
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    Quote Originally Posted by ckelloug View Post
    I think our Socratic Dialog here may actually clear some confusion.

    --Cameron
    Not so sure, The earlier posts pretty much covered most aspects of whats needed.

    Socrates was a troubled soul so maybe not a good aim for the thread. Besides, the 'Dialog' has no value unless 'examining the implications of the students answer' actually occurs fairly, objectively and openly.

    Then you have to decide who's Student and who's Teacher which th eman himself couldn't answer...

    </Socrates>

  18. #1578
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    http://www.northerncoatings.com/newpage14.htm
    100CPS epoxy walter soluble.Check it out.
    Larry
    L GALILEO THE EPOXY SURFACE PLATE IS FLAT

  19. #1579
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    Ive been looking at the Loctite site.
    We do bussiness with them, and their products are easy for me to get.
    Maybe someone that knows more about this stuff can look at it and advise.
    http://www.loctite.us/int_henkel/loc...tics_32-45.pdf
    They also have their Hysol epoxy.
    It may be that none of it will work for our purpose but i'm not sure.

  20. #1580
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    ckelloug

    Hi,

    Re the surface energy problem.

    In order to decorate plastic blow molded bottles, the maunfacturers change the surface energy so the inks will adhere. They do this by passing the bottles in front of a torch at a fast rate of speed, so the surface is "flashed" by the flame.
    I don't know if the same technique applied to the aggreagte would work but it might be worth a try.

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