Home-brewed plastic made from milk ...

Hi Fernando,

... it's not so hot, only a 'sideway' i'll try when finding time after getting the other tasks working.

Actually i'm busy with paste-soldering for temperatures between 300

Smoking formaldehyde.

Not recommended, apparently Methanol is also toxic due to the way Alcohol Dehydrodgenase breaks it down into formaldehyde. It is apparently the formaldehyde that attacks the optic nerve and is the primary cause of blindness associated with meths drinkers and folk who drink large quantities of home brewed stuff that has a meths content (cider.....).

I remember reading this somewhere, it could be Wikipedia.

cheers

aka47

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Necessity hopefully becomes the absentee parent of successfully invented children.

Is there any mileage do we think in "Post Polymerisation"

So far we are largely looking at depositing polymer etc.

I rememeber going to see Gunther Von Hagen's Body Worlds exhibition (CorpeWelten). The guy who plastinates dead bodies for anatomy demonstrations. Very clever.

Could we deposit an aquous paste (form work). Dry by immersion in acetone (efectively displace all the remaining water from the form work in favour of acetone). then replace the acetone with resin before finaly catalysing it.

Acetone and polyester resin are readily available and reasonably inexpensive.

I seem to remember aerogell being made using an aqueous solution that was then alcohol dried before baking out the alcohol.

Thoughts

aka47

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Necessity hopefully becomes the absentee parent of successfully invented children.

Triffid_Hunter Wrote:
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> can make plastic from starch too.. see
> [www.instructables.com]
> c!/ (step 3 has the recipe)

I tried this one and it turned out nicely, but the result is very rubbery/gummy. It's not at all a hard plastic.

I think the amount of glycerine controls the texture. no glycerin = hard and brittle, lots of glycerin = rubbery and flexible.

And I wondered what to do with all those bio-deisel left overs...

aka47

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Necessity hopefully becomes the absentee parent of successfully invented children.

Please note that the leftover glycerin from biodiesel can be used as a de-watering agent for an alcohol still. After processing your mash and having the system output 160 proof alcohol. You then can bubble the vapor through a vat of glycerin and remove the rest of the water and get about 194 proof alcohol. But don't do this without a permit from the government or you are just like any old moonshiner and they do do jail time. I found an article on the internet from when this was done in the 1930's. I works just fine.

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Bob Teeter
"What Box?"

Instead of making alcohol with glycerin, you could add Sodium Hydroxide to it to make glycerin soap, which could be used as a support medium. Glycerin soap melts like wax, but dissolves in water.

In addition, you can use it as soap.

Gene Hacker sir I think you may have hit on something there....

I did'nt realise Glycerin soap did the melt like wax thing. This has potential as an extrudeable support medium for cold polymer deposition maybe UV Cure.

hmmmmmm

I guess the melt like wax thing though would fail using FDM due to the heat of extruded polymer....

cheers

aka47

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Necessity hopefully becomes the absentee parent of successfully invented children.

So just print out the plastic, cool it with a fan for a bit, then extrude a wax layer. It also might be possible to adjust the melting temperature with additives, like adding animal fat or long fatty acids into the soap. For extruding plastic onto wax, it might be possible to spray an insulating agent to slow down heat transfer to the wax. In addition this also makes it easier to remove support material.

is it possible to extrude a salt based compound rather than a hydrocarbon for a support material... this may have a wider thermal range whie retaining the ability to be water soluble. Just a thought, I haven't really researched the possibilities or problems associated with this at all yet, it just sprang to mind while drunk.

I think the support material question is one that is going to keep on popping up.

I haven't seen any suggested yet hit hit the "YES" what great idea button.

It isn't that folk aren't coming up with great ideas, because they are. The nearest i got to YES factor was the suggestion above of glycerin soap extruded as a wax.

Maybe we should be looking at Salt Compounds I think Icing Sugar has been suggested.

Most things that crystallize (as in water based crystalline) have the great property of dissolving readily (most desirable) but also have the down sides of low shelf lives (or they wouldn't set up or support quick enough) and or being very gritty/abrasive ie prone to jamming.

I was looking at silly putty. Yes the stuff runs away if left. but that could be fine in smaller pieces where the rate of deposition is much greater that the rate it runs away at.

Still scratching head and waiting for a "YES" moment.

aka47

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Necessity hopefully becomes the absentee parent of successfully invented children.

Yes, I too haven't seen a support suggestion that I think will work yet. Not only does it have to provide support against gravity but it must also stick to the thermoplastic in the same way that the base board must, otherwise the filament curls up and gets dragged around by the nozzle. It also has to be strong enough to resist any warping forces.

The problem with HDPE is that it sticks to virtually nothing. It would appear that CAPA can be extruded onto a wider range of materials though.

The support material needs to be:

Paste like, so can be extruded itself without slumping.
Preferable fast setting.
Able to stand the temperature of the molten build material.
Able to bind to the build material.
Strong enough to hold the build material in place.
Soluble with a solvent that is not too nasty, preferably water.

Binding to the build material seems to be a difficult thing to achieve, certaily with HDPE. HDPE does not seem to bind to much chemically. To make a mechanical bond it would need a porous material with a low specific heat capacity and a low conductivity so the molten plastic had time to penetrate the porosity before it set. This is difficult because of the high viscosity.

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[www.hydraraptor.blogspot.com]

For an ideal but as yet unspecified support material what propertied do we really need and what do we want.

Lets split the problem down into two parts..........

Support

The extruded/deposited support material must have sufficient viscosity/strength to support a specified mass/weight/quantity of component plastic extruded over the top. It may not actually have to be fully solid at all, it just needs enough viscosity.

It must not be Plastic-phobic to the plastic we are extruding onto it, ie it must adhere to the extruded filament to keep it in place. (Nice one nophead)


I can't help but think that we need a thermo-set that can be persuaded to initiate setting under a moderate temperature increase.

Extruding it through a heated barrel initiates the set, which completes soon after deposition just prior to cooling.

Further heat applied just set's it up firmer, ie when something is extruded over the top.

This should give longer shelf/tool life and a usable support material.

The thermo-set compound could be paste, resin, crystalline or whatever. It just has to have the properties above.


Support Removal

Once the piece is finished, the support material must be removable through what ever orifices were put into the workpiece for the purpose.

The cleanup holes (better than orifices) under worst case conditions may actually be a lot smaller than the potential cavities the support material filled.

It will be a given that completely enclosed cavities filled with support cannot be made in one go as there must remain a method to get the support material out.

From this it follows that the support material (what ever it is) must be able to be removed as if it were a fluid. (Note, a sufficiently fine enough powder may be considered as a fluid for this discussion)

Following on then I come to the conclusions that the support material must have one of the following classes of properties (but could actually have more than one)

1. It can be dissolved by a solvent that doesn't upset the plastic of the component. (May therefore be different for each plastic feedstock used, but would be great if it was the same for all)

2. It is composed of a filler and support matrix where the support matrix can be dissolved by a solvent that doesn't upset the plastic of the component.

3. Whether as a support matrix or as a whole the material when exposed to a destructive force (Heat, ultrasonics, wavelength of light) must easily (ie within a sensible time frame) decompose to a fluid form. the destructive force must not be such that it weakens or destroys the integrity of the component.

A lot to consider...

What do you guys think ??

aka47

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Necessity hopefully becomes the absentee parent of successfully invented children.

Andy,
I disagree with "It may not actually have to be fully solid at all, it just needs enough viscosity.". Certainly in my experience with HDPE it would have to be a strong solid.

If you wanted to make a bridge then, yes, you could get away with something that simply supported the filament until it set because it would be welded to the build material at each end of the span. In fact it may be possible to build some shapes like that without any support. The filament can be stretched over a gap and will pull itself tight when it cools due to shrinkage.

When making something with overhangs though, I think you need a rigid support to resist the curling forces without moving for long enough for many layers to be built on top.

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[www.hydraraptor.blogspot.com]

Yup fair point, solid it is then.

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Necessity hopefully becomes the absentee parent of successfully invented children.

Concretions seem like an obvious way to go for a support material as they don't need a particularly strong cement to retain compressive strength.

The cement could be a water soluble substance such as sugar, with the aggregate being a mixture of different grades of sand. This mixture should need only a little heating to drive out the moisture as there won't be very much moisture in it.

Much of the heat driving the setting of the concrete could be stored in the aggregate, so if the heating, mixing and deposition are carefully arranged, then it should be possible to extrude a rapidly hardening slurry that can easily be washed away.

Perhaps it could be done by heating the sand first as it enters the extruder and then have it mixed with cold sugar-water in the actual extruder body, just before reaching the nozzle. Alternatively, this degree of sophistication may not be required and a premixed paste of sand and sugar-water might work if delivered directly to a heated nozzle.

If the mixture is premixed, then flow control could be achieved from higher up the chain with air/fluid pressure and gravity, so allowing the extruder to have no moving parts and therefore hopefully eliminating the problems of components failing due to sand getting where it shouldn't. There might also be a really clever way of doing a mixing extruder with no moving parts, but I haven't thought of one yet.

Also a mixture of sand and sugar should provide a nice key for hot plastic to stick to, though some sands may be better at this than others and there may be things that could be used as sand analogues that would do even better, such as granulated plastic with a high melting point, granulated metals or crushed glass.

Other considerations are whether there are other alternatives to sugar for the cement, I suggested salt further up the page as something to look into, and I am sure there are other possible substances out there, although maybe none so readily available as either salts or sugars.

also, just found these links - [www.personal.psu.edu] - [www.personal.psu.edu] - [www.physorg.com] - perhaps a day at the beach making sandcastles is called for...

---------------

*edit* epsom salts... hmmmm... might be onto something...
(I will now stop playing on net while drinking beer and instead go to bed and dream of sandcastes and seagulls)

Edited 1 time(s). Last edit at 02/17/2008 08:33PM by deadgenome.

Interesting links,

I can't help but think that concretion is something of a double edged sword. I that you have abrasives, setup time and shelf/tool life to consider. Taking all of the previous gives you a very limited window of opportunity for repeatable success. Having said that I can certainly see the appeal and experimentation may indeed yield a mix that works and can be delivered by a relatively low tech tool head.

My thoughts re above are based upon experiments years ago at finding ways to make pointing brickwork with standard mortar easier, I tried Caulk Gun style tools, Icing bags etc but had the recurant problem that compressing the stuff seemed to make it jam up in the nozzle just about every time. Basically the pressure seemed to preferentially displace the water and bring on an earlier set in conjunction with jamming the aggregate together. (Sand is'nt great at flowing unless very wet or very dry, The observation about the sandcastle thing). I found this out by cutting open the nozzles etc to see why.

I also have spent some time looking at the design of concrete pumps to find out why given my lack of success (which could well have been ignorance and youthful enthusiasm) they work.

Nearest I could figure out is that the concrete pumps don't actually Nozzle or restrict the flow and the drive is both intermittent (piston or ram) helping the concrete to behave more like a liquid (Pat wet sand and watch it flow).

For these reasons and these reasons only (please someone find something I have missed here) I personally struggle with the aggregate in paste methods or concretion.

What was interesting for me looking at the links was the abstract on the micro tomography research into why sandcastles stick together.

If you go for a fine sand non concreting method for support based on the sticky sandcastle approach and enhance it a little by adding a non concreting (non crystalyzing) binder do we have a viable method with a big enough window of opportunity for success ???

I can't but help thinking about the green sand used in sand box casting. Sand Water & Binder. Gut feel says it has some potential but not enough...... (It's suffers from having a rough agregate in the mix. Maybe something made of micro spheres may work better ??)

What do you guys think ??

aka47

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Necessity hopefully becomes the absentee parent of successfully invented children.

... i think for building big objects with sand/concrete the best way should be to reprap the outer surface of the object with normal plastic in slices of some millimetres or centimetres height, fill the structure completelly with the sand-mixture, let it harden and then process the next slice ontop ...

'Normal' sand-particles are to sharp-edged and rough to go through a dispenser and when mixing with to much glue it won't be hard and rigid enough.

When using glass-spheres instead of sand, then it 'flush' much better, but the internal adhesion isn't so good, so you have to apply more fibres, what tends to stick in the dispenser too.

Another approach could be the method of SLS-fabbing but with wet glue instead of molten material in the laserspot: -- inkjet a droplet of glue on the surface, blow some air with sand-particles over the droplet, so it accumulate the sand, blow away with clean air the not wetted sandparticles, and process your object-volume until it's ready ...

Viktor

I know this is slightly at a tangent to the current but I have just been looking at some electrical gear (putting more lights in the loft) and couldn't help but notice the knock-out portions.

This might help with some of the things we need to do (certainly not all or even possibly the majority).

Basically add in thin easily cut sections into the master drawings as supports. I am thinking predominantly of things like holes here in the Rep Rap corner pieces etc. I fully understand that what is the current state of the art is great it's just that being a touch anal retentive (Sorry guys) those teardrop shaped round holes drive me wild....

cheers

aka47

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Necessity hopefully becomes the absentee parent of successfully invented children.

Just had another quick set of thoughts.

What about making a paste up from a salt (ie water soluble) in its crystal form whetted with a volatile that the crystals don't dissolve or react with. Effectively using dissolvable crystals as aggregate.

If we could find such a salt and the basic crystal shape was closer to a sphere than say a cube then we should have the basis for a paste that is easier to dispense, we warm it on the way out to encourage the whetting agent (Maybe Ethanol, reasonably safe and fun if using in enclosed spaces) to evaporate more rapidly. (Maybe blow air over the workpiece as we deposit as well).

Later removal of the support is a case of dipping the piece in water or suitable solvent. Recovery of the salt is by evaporation before processing again into the preferred crystal size for reuse.

regeneration of crystal feedstock could be either by milling from dry or milling after the crystals have been encouraged to form small during the latter stages of evaporation. (ie perpetual stirring like making sorbet or ice cream)

Thoughts for what they are worth.

aka47

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Necessity hopefully becomes the absentee parent of successfully invented children.

By George I may have it, but it's not catching......

The Vodka Method....

Epsom Salt or Magnesium Sulphate, available from most mosts chemists even in the UK.

Great as a desiccant, barely dissolves in ethanol, can be made anhydrous by heating to 200 Deg Centigrade (Within the range of the average oven)

I think I might try this later. just for fun.

The cleanest Ethanol based spirit I know of that is commonly available is Vodka, Absolute Vodka generally clocks in at 57 percent by volume (ish). I don't recommend anything with Methanol in it.

Take Magnesium Sulphate, bake at 200 Deg Centigrade in oven until reduced to white powder. Cool in something you can seal to stop the Magnesium Sulphate from reabsorbing too much water vapor from the atmosphere.

Slowly add cooled anhydrous magnesium sulphate (you want to make sure you know when the solution has saturated) stirring constantly until you get something useful. (Don't know yet whether this will actually be paste or a rapidly crystallizing solution.

This is of course all theoretical cause I haven't tried it yet.

The aim is to dessicate the vodka using the Anhydrous solid (creating a supersaturated solution of Ethanol Whetted Hydrous Magnesium Sulphate paste or fluid) until you get something usable that crystallizes/sets quickly enough to be useful.

Heating to 40 or 50 Deg Centigrade or so immediately prior to dispensing should encourage the ethanol to rapidly evaporate leaving something that desperately wants to crystallize and can draw the extra water it needs to do so (Water of crystallization) from the surrounding air (hygroscopic) so forming a supporting solid.

Heat from FDM should accelerate the process, recovery/removal of the support is by dissolving the Hydrous Magnesium Sulphate using warm water.

My understanding which is severely limited when it comes to chemistry is that providing you make sure that their is little or no evaporation or ability for hygroscopic intake it should be possible to store the stuff with a reasonable shelf/tool life.

OK guys what have I got wrong...... It looks too easy.

aka47

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Necessity hopefully becomes the absentee parent of successfully invented children.

Only problem I can see immediately is expense as it would presumably take quite a lot of vodka per model.. you can always distill your own ethanol of course, though you need a convincing way to demonstrate to the excise man that you are not drinking it.. very good in Russia though Also, if you want anhydrous ethanol (very useful if you wish to make biodeisel without using methanol) get some molecular sieves - [deltaadsorbents.thomasnet.com] - they can be reused time and time again by heating them to dry the water off that they have absorbed. Not sure if this helps.. perhaps I need to drink some vodka to completely get the plan.

If the trials work out you could always go for lab grade and add water.

Don't know if this is any cheaper though and you have difficulty getting it supplied in the UK as a member of the public. Just about anything chemical and lab grade is subject to an excessive amount of paranoia in the UK these days.

You could use cheap vodka you just have to put more epsom salts in it.

I guess if it works we should call it "White Russian" snigger guffaw chortle.

aka47

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Necessity hopefully becomes the absentee parent of successfully invented children.

It looks like Stratasys uses a water-soluble plastic called poly(2-ethyl-2-oxazoline), or PETOX, mixed with an "inert filler":

[www.google.com]

Possibilities for the filler are listed in the patent: "calcium carbonate, glass spheres, graphite, carbon black, carbon fiber, glass fiber, talc, wollastonite, mica, alumina, silica, and silicon carbide".

I found PETOX from a supplier called PolySciences for nearly $1 per gram! I don't know what ratio it would be mixed at, but that sounds pretty expensive. And it's patented. But I thought I'd post this info in case it gives any ideas to those more knowledgeable than myself.

well we don't have to sell filler to people, just provide instructions on how to make it... ( idly wonders how long it will be before there is an attempt to extend patent law to things you make yourself.. And if it will be as near impossible to do as I think it will.. I.P. law on physical possessions, come on and say a big *hello* to the mp3 generation )

Yes that's true. But who knows, maybe Stratasys could just as well do some cheap way to make support material, aside from it's a lot nicer to make your margin on fancy polymers than a $10 bucket of glop. (Since they get a kind of monopoly from the other patents and, of course, you can't modify their product!) Anyway, it is that $10 glop we need... Still, I guess I could try getting some of that PETOX stuff once I get to that point with my machine. I found a much better deal, 22.60 for 100g, at sigmaaldrich.com. Considering the price of CAPA, that's starting to sound like the same ballpark.

Or I'll try the Vodka and magnesium sulphate - I like that idea a lot! Could be just the substitute we need.

Anybody experimenting post your results & methods back here, at the moment it's just ideas and will need a bunch of folk to verify/modify or discard before were done.

Re patents from my reading of the links above they all pretty much seem to be down the aggregate, binder and plasticizer route.

Rather than the Plasticizer & Crystalizer suggested as a possible theory here.

Further my understanding of Copyright, IP and Patent etc is that where there is provable prior documentation (Particularly published, like here) the later Patent/IP claim is impaired or N&V. I could be well wrong on that one and am happy to be corrected.

I feel a road trip to Liddle for cheap no name vodka coming on......



aka47

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Necessity hopefully becomes the absentee parent of successfully invented children.

That is true.... anything that is posted on here that is not already covered by a patent, adds to 'The Current State of The Art', automatically becomes 'Prior Art' and is also considered 'Public Disclosure' so it is unpatentable by anyone, including whoever came up with the idea. If a patent is granted that covers something previously posted on this forum, then that patent can be contested, so it would be a good idea to have this forum mirrored by a few independent people, as well as regularly backed up and copys of the backups held by a trusted third party. That's if we want to get paranoid.... one way of achieving this end would be to subscribe to the Waybackmachine's [www.archive.org] sister project Archive-IT [www.archive-it.org] as this should have the required status of reputation for any court in Europe or America.

Epsom salt actually forms a nice paste when ground up and mixed with just the right amount of water. It also tends to hold its shape too, especially as it dries out. It behaves very much like sand. It also has a nice rough texture which might be a good surface to extrude on. I also don't think ammonium sulfate undergoes truly rapid crystallization.

Sodium acetate is another potential salt that definately crystallizes very rapidly. However, I have found it hard not getting it to crystallize.(this could of course be due to the fact I am using impure sodium acetate) But, this is not a problem as long as you have a heated extruder, I have found that hydrous sodium acetate will melt given heat.

Could you explain to me why the ethanol is needed for magnesium sulfate? Is it to help the HDPE stick to it? Is to make it flow better?