Furfuryl Alcohol and blocked catalyzers (formerly delivery woes...)

Hello all!

I've been a little distant these last couple of months. As someone has said in another post, having a private life sometimes seems to slow your research down to a standstill. I have been helping my girlfriend with her apartment down the coast, and I must admit that spending my weekends over there has been a constant temptation that i am not strong enough to resist

But this is not the only issue that has kept me away from reprapping tasks! I have been batteling for the last 2 months to get my purchase order delivered!! Spain is just a bitch to get deliveries to... Today I finally got the base materials that will allow me to research into 3D serigraphy and heat activated hardening.

Nevertheless, I'm a little concerned about the difficulties of people getting these very basic products at home. Someday we will have to think about basic products acquisition. This will lower the purchase prices drastically and improve reliability and accessibility.

Anyway, I missed you people and I'm happy to be busy with reprap again!

Edited 1 time(s). Last edit at 11/01/2007 01:29PM by Fernando.

I'm glad to see you. I was worried you'd suffered terminal burnout, and the very promising avenues you were exploring would go unmapped.

Harrumph....

Sean, you may be a bit of a prophet, even though you were over-eager with the "terminal" part
Yesterday I made an exploratory test with 10g of Forfuryl Alcohol and an acidic catalyzer, just to see how fast that thing polimerzes... Darn!!! That thing is fast and exothermic! It littelrally popped the lid of the plastic dish i was using. Most of it went to my hand and the wall. Nothing terminal, just very gooey and sticky. I had a scare, and cleaning up was not to fun.

Right now i'm doing it again but with some safety measures that will slow down the reaction (basicaly, I added mineral dust and reduced catalyzer amount). It's going on pretty well, safe and steady.

I'll be posting fast comments and ideas on the forum for your feedback and will post more accurate results in the builders blog and hope to put up some definitive mixes and results on the wiki. I have allready gotten myself a halogen lamp with a magnifying glass to make a simple focussing device. This will serve as a simplified lightpen to heat the resin on certain spots.

Keep posted y'all, it's going to be fun!

After reading Victors thread on selective sintering I finally understood what you are trying to do, approximately. Very interesting work!

So is it the UV light that triggers the exothermic reaction? How fast do you expect a "layer" to be finished? How thick will the layers be?

For this type of resin we won't even need UV light.
A regular 30W halogen bulb with a magnifying glas or a tweaked laser diode will do the trick.

The important thing here is to get the surface of the resin to heat up at about 60-70

Hi Fernando,

... can you give me the formula and tech-specs of your polymers please?

I'm playing around with a 1Watt-Diodelaser with 60micron-fiber at home and in my job i today finished the drivers and optics of a 9-Watts-Diodelaser with 100micron-fiber, so i can make a focus down to 50 microns and tests with sintering or heat-curing of different material.

Some years ago i had 3Watt- and 5Watt-CO2-lasers, which i used to cut thin slices of plastics for marking and signs.

Now i try different approaches of 3D-fabbing:
- cutting stacked slices as in LOM-fabbing (Laminated-Object-Modelling)
- heat-curing of ready mixed pastes and 2K-epoxies
- mixing pastes with dexpanthenol and glycerine as solvent and soldering glass or gold-powder as body
- direct laser-sintering of surfaces of sand or micro-glass-spheres
- and some other ideas ...

Maybe your polymerising agents are good candidates for laser-curing too ...

Viktor

Hi all,

I have a general question about this process. Does the working area stay filled with the fluid or is the level of the fluid raised as we progress from layer to layer?

In the first case, the beam does not affect the polymer until it is focused as it lacks the heat capacity until that point to trigger the reaction. In the second case, won't there be a problem with surface tension keeping the fluid from coming over the top of the layer you just made? I don't know if I'm being clear. If it is the first scenario then this isn't even a problem but it doesn't sound like this is the case.

Demented

Hi Demented,

... my approach is a low-viscose paste, which i can dispense in diametres under 100 microns or single droplets down to 10 microns, which i heat-cure with the laser to harden directly after releasing ...

A second setup is to output a complete layer and bake the layer completely - then a big IR-heater, which activates the complete surface is better and faster, then a laser-spot ...

Heat-curing of fluid-surfaces, as in SLA-printers isn't so good, as heating makes a much bigger spot, then 'cold' UV-curing, so th eaccuracy isn't good.

Viktor

Viktor,

I get it. I was thinking in terms of pools of fluid when the reality was much more refined. I understand the accuracy issue between thermal and UV curring. It doesn't seem like that much more trouble to UV cure than to heat cure.

Demented

Hello all!

The mix i'm testing now is made of Furfuryl Alcohol (FA, the actual resin [www.acros.com]) and p-Toluenesulfonate (pTS: [www.acros.com]), wich is a solid organic acid that you can solve in Isopropanol.

On the dissolved pTS you need to block the acid functional group. You do this by adding wether Vinyl-ether or N-Methydiethanolamine (http://www.acros.com/DesktopModules/Acros_Search_Results/Acros_Search_Results.aspx?search_type=CAS&SearchString=105-59-9)

The FA has to be mixed with some filler material. I'm trying Kaolin dust and TiO2 pigment, but a good solution would also be Cellulose or wood dust. Appart from stabilising the whole resin, wich otherwise can polimerise very fast and resleasing heat (caution!) I think the mineral dust will give the whole mix a greater thermic inertia, allowing the heat of the beam to be concentrated on smaller scales.

I have not thought yet what the best solution would be: a vat to be filled up one levelafter each hardening step or lowering the piece after each step... that remains to be seen.
Also, there is no definitive mix I have decided yet. There is still a lot of experimenting to be done as I have just started with this line of research.

Hope this helped a bit

Hi Fernando,

... thanks!

Sounds to be a very interesting material, when dispensed and tracted with the laser

With a heating spot of 50 microns i think the activation-zone should be around 80 microns, if the reaction doesn't expand on self?

If you find a mixture, which will stay stable and fluid at room-temp and harden in seconds when lasercured, then there should be some testing with partial hardening and use the fluid paste as a sort of support for the 'fine-structure' too ...

I'm actually testing baking and sintering/melting of different powders solved with dexpanthenol.

The mixed paste is stable for weeks and doesn't settle even with gold-powder, but when heated, the dexpanthenol vanish completely, so the powder can sinter to solid and with the right heating it melts to pure material.

I tried with soldering glass, which melts at 430

Viktor

It sounds really amazing what you are doing.
One question: why are you concentratinmg on gold? Is that your trade? Are you a jeweler?

I would have guessed that using bronze or messing (brass) would be a cheaper and more obvious choice. Also, correct me if I'm wrong but gold melts around 800

Hi fernando,

... the gold is for a special problem: - we assemble a sensor, which is made from ceramic with gold-pads, on which we fix thin platinum-wires (10 microns and 1 micron diameter) as temp-sensing elements.

Until now the wires were fixed with a conducting silver-filled polyimid paste, which will be heat-cured at 175

Fascinating stuff!

To bad i don't have such powerfull laser sources, it seems that a whole world of sintering possibilities lies there to be experimented...

Anyway, I will keep you indformed with the progresses I make with heat/light/UV activated polymer resins. Let's see if we can get some neat application working at low temperatures!

I'll inform you with mixture proportions soon. I'll also try to post more detailed exprerience procedures in the builders blog. I'm sure we will make several advances soon, as we seem to have a lot of knowledge to share.

OK, i'm signing out for tonight. I'll be back posting tomorrow!
Cheers!

WOW!

I'm VERY, VERY glad you were only working with 10g at the time. Explosive polymerization is a very accurate term for what happens, isnt it. That you were working with a sealed jar is quite scary.

Whats the pot life like for the blocked catayst/resin mixture. Is the resin advancing due to the presence of small amounts of unblocked catayst? If you are using inorganic fillers you might consider added some silanes since they are mildly basic and in sufficient amounts they stablize the resin giving longer potlife, while also improving humidity resisance of the finished product. Ideally you want to be able to add the catayst to a large tub of the material and leave it there, without having to worry about resin advancement.

The other thing is, why Furfural Alcohol? Why not Furfural Aldehyde?

Even as I ask the question I suspect the answer, Furfural aldehyde is TOO stable the heat and acidity necessary to crosslink it are too high for high productivity. That is the reason that furfural alcohol became popular desite its dangers.

Please be safe and be careful.

Mike

Hello Mike, nice to hear back from you!

Actually i started with Furfuryl Alcohol and not Furfur Aldehyde because it seemed to be less volatile as in less vapors. But I do have both and I want to complete the same tests on FAld as I'm doing on FAlc.

Yeah, the sealed pot was a stupid idea, I know
Afterwards I remembered you saying something about this in one of your previous posts. I think I will be very specific about safety measures on this one.

The pot life of the resin with the blocked mix, as long as you keep it safe from air and light is over 4 days (and running, i have it here next to me and it's still unchanged).
I will need to be very precise about the blocker additive, as it has a huge importance on the reactivity of the catalyzer. I have seen that a 0,5 to 0,5 mol mix of pTSA to MDEA is not enough reactive, so that I will go to th eroute of neutralyzing the pTSA with MDEA little by little untill I reach a pH of 6 or 7. This should happen at a ratio of 0,5 mol pTSA to 0,46 mol MDEA.

As a filler, I have noticed that Titanium Oxide is a LOT better than Kaolin. It's also more expensive but it really does the trick. it gives the resin a better stiffness, the end result is less brittle and more homogeneous. It also reduces the reactivity of the FAlc quite a bit, just the same as you described with silanes, making the whole thing mixed with catalyzer a lot more manageable.

For now, I make my tests of reactivity with waterbaths, as I can test a complete layer of resin mix in one go and can control the temperature very easely in steps of 10

Hi Fernando,

... you can make tests with stark instead of cellulose, should work similar ...

My tests with laser-melting gold-dexpanthenol-paste went fine, the heavier part is now to adjust the output-power of the diode-laser, to liquidize the gold-powder, but stop melting, before the gold-pad under the paste is melted completely too ...

Tomorrow i'll try sintering or melt the iron-paste, which i mixed for the 'Artificial Muscles'-Thread.

Glass-powder-paste was fused/melted very good to solid glass, so i could make lines of solid glass on a surface - if the tension between stacked slices shouldn't be so strong that it brakes, this would be the proof-of-concept for 3D-printing with solidified glass.

The next step will be sintering/melting paste from ceramic-dust, when our supporter for the ceramic-sensor will give me some probes of their different print-pastes ...

Viktor

Hey Viktor!

Good idea! I will try starch as it's pretty easy to get and it's also a standard product.
I don't know how much fiber it contains, but it's worth a try.

Its always great to hear about your sintering efforts. They really seem to be going well!
It seems that glass, having a big thermal inertia is easier to sinter than metal, is that correct?
This would be an interesting result and would aim you to wards ceramics as you say.
Did you consider ceramic glazing powders? They are standard and easily available, although I am not aware of the prices they come in. I do know you can buy them by the kilo and they come in different mixtures that seem to melt at lower temperatures than clay grains.
Dunno, just an idea.

Hi Fernando,

... glass and ceramic melts much better then metall, but they have a higher thermal contraction, so i must mix materials with different TK-values for better stability, or it would brake apart, when cooling down ...

Another point: - i have to dry the paste with lower energy completely, befor i can melt the powder to solid, or the evaporating solvant would blast the powder away ...

For simple 3D-fabbing it's maybe better, only 'bake the paste a bit' to make it stiff enough to support the next slices - then put the object in an oven and heat it to end-temperature, for solidifying the body without melting it ...

I think, the 200mW-IR-diodelasers (and maybe the red ones too) from newer DVD-RW-drives should have enough energy, to heat plastic-powder-pastes and dry them, so a 3D-laser-fabber for plastics could be made 'cheap and dirty'

With the UV-diodelasers from BluRay-drives there could be UV-laser-curing too!

But it's essential, to protect your eyes and the surrounding, so you have to find (or make with IR-blocking filters or Blue+UV for the BluRay-diode) laser-goggles for testing and make a light-tight housing for the reprap.

Viktor

(from builders blog entry)

Hi all!

Today I made some progress on the blocked catalyzer.
As a reminder, the catalyzer is para-Toluene Sulfonic Acid (pTSA), wich is a strong organic acid, in solid form. I have dissolved it in Isopropanol alcohol (a solventquite similar to Ethanol).

This catalyzer, if added in this solved form to Furfuryl Alcohol (FAlc, the actual polymer resin) will cause it to polymerize extremely fast and under the release of heat. This should not be done, take my word!

The trick here is to reversibly block the catalyzer just enough, so that you can mix it with the FAlc and the mix stays stable, for at least a day. The reversible word here means that with the application of heat, the catalyzer gets released again and the resin starts polymerizing on demand.

So this is what I have been testing today: I have tried different degrees of blocking and the temperatures necessary for unblocking the catalyzer.

The blocker I used is a strong organic amine base (N-Methyldiethanolamine, short MDEA).
This amine will react with the organic acid and form an organic salt, but that is reversibly bound. The fact that it's a base makes it possible to use the pH level (acidity level) to measure on how much it has been blocked.

I have tried pH 7 (neutralized), 6, 5, 4, 2 and 1 (strong acid).
What I have discovered is that MDEA blocks pTSA quite a lot and that the pH 7 down to pH4 samples were only marginally active catalyzers, even at heats up to 100

Edited 1 time(s). Last edit at 11/01/2007 02:03PM by Fernando.

Hi Fernando,

... sounds really good!

Actually i'm bound with other tasks, but that's a way, i want to go - keep us informed and be carefull, not to rocket your house in the sky

To the diode-lasers: you should salvage lasers only from newer Drives, so 40x or faster - in older drives the diodes haven't enough power, in pointers it's the same - with a 5mW-Diode there isn't a sensable heat in the focus ...

The 54x-CD-Drives and 12x-DVD-writers have 150 to 220 milliwatts, when supplied with 80% max. current and good cooling, they didn't wear out, so with a 220mW-Diode you can have a stable power-output of 180 mW or so without much worry.

The focussing is another part - if it's possible, use the lenses of the drive in the same setup.

The diodes have a very poor output-quality, so the focussing to a small spot isn't so easy without to much power-loss.

I use fiber-coupled laserdiodes with 1,2 Watt at home or 8 Watts in the job - the 1,2-Watt-diode runs with max. 0,8W, the 8-Watt-diode runs actually at 5 Watts max, so i didn't bother with lifetime or so ...

The fibers have a diameter of 100 microns, so with two lenses i can focus the beam down to nearly 60 microns.

If you manage to fit the diode with a thinner fiber (i'm playing with the idea to taper the fiber gently with heating and pulling it, so it should expand and shrink down to 30 microns or so), so you can reduce the focus and rise the energy-density too ...

Viktor

Hey all!

After 2 weeks spent with a broken ellbow, i'm back on the workbench.
Nothing, i say NOTHING will hold me back

I have had some interesting results while mixing copper powder with this resin.
I mixed around 70 weight% of copper vs the resin mix. The resin polimerzed slow enough so that the copper powder subsided towards the bottom of the polimer.
When braking off the sample, which is 2mm thick, i can clearly see the layering: on top the black polymerized plastic and below a dark brown mix of resin with a copper fraction far above the 70%.

When measuring the resistance of the lower layer, i get values below 1 Ohm. The top layer is completely insulating.
I think these are very promising results!

WOW!!!

that is awesome fernando. if that is the case, it should be very simple to lay down tracks of this mixture to create traces.

bravo sir, bravo.

Hi Fernando,

... yes! that seems to be the ideal basis for electric circuits - touch-safe, but conducting

Can you try to apply a higher current to the trays and look, if they change in resistance?

Copper isn't so stable in some polymers, so after a while or with higher currents it oxidize and the conducting went poor or vanish completely ...

We use a heat-curing polyimid-silver-paste, which is very good conducting, stable in normal ambient conditions (break down with hot NOX or acids!) but didn't sedimentate ...

In the silver-paste the silver-particles are thin flakes, so the interconnecting is very good - if your copper-particles are more spheric, then you have to compact them for proper conducting (with the sedimentation, for example)

For some experiments with polymer-muscles i mixed a resin with graphite, it's a tricky play between conducting and shape-morphing, but works for lower currents and higher voltages too ...

Viktor

Personally, I'd rather have it stay mixed, then top-coat it to insulate it.
As it is, you can lay traces in the X-Y plane, but it doesn't sound like you can build risers.

The conductivity of the bottom layer sounds good, though.

Hi Sean,

... for risers or vias you can insert metall-pins or silvercoated copper-vias (as used in manually assembled double-layer-pcb's) in the wet paste.

Viktor

... here i have some images of laser-sintered gold-paste on pads.

The pads are 150 microns wide and nearly 300 microns long, the droplet of gold-paste was something between 100 and 200 microns in diameter, when wet.

With 'low-energy-curing' (diode-laser at 1 Watt, 100-micron-laserspot) i dried the dexpanthenol-solvent away and then melted the gold-powder with some 3 Watts laser-power to solid.

Some tests with melting gold- and glass-pastes on pure surfaces (without predefined pads) showed, that you often need a fixing-basis, or the gold (or metall in general) didn't connect to the surface.

With mixing of gold AND glass in a paste i hope to get better connecting on ceramic-surfaces without metallic coating, so i can 'paint' very stable and rigid conducting trays of pure metall and embed electronic components and wires in solidified glass or ceramic ...

Viktor

Hey all!

Thanx Zach! I also think this could be usefull. I will try and put together a recipy that people could easely work with.
I guess that building a simple circuit board would be th enext step... but I'm not very much of an electronics guy, so maybe somebody has a simple diagram that I can build. Nothing crazy. Just stuff to test resistors, transistors, condensators etc with this type of tracks.

Hey Vik!
It's very interesting to see pictures of your researches.
I prefer to go with cheaper materials than gold or silver as I'm trying to make it as available as possible to everybody. I'm trying to think big scale and affordable, and silver, gold or exotic alloys are better suited for specialty and super-accurate applications as yours.
I haven't come accross a DVD laser yet as I'm a little impaired with my broken arm, but that's very much on my list. I just want it!

When you speak of copper reacting inside the polymer at higher voltages, what voltages are you talking about? My multimeter does the usual 9V at the higest ohm-meter scale. I guess we don't need it to be stable much further of the 15V for the circuit-board application.
For higher power applications, I would have to test it further, but I guess 1 Ohm resistance is high enough to produce heat enough to cause trouble...

(I think I should create a separated thread with this conductive polymer issue)

Hi Fernando,

... for the polymer-muscles i used voltages until 2kV, much safer is the range until 60Volts, of course

I think it's the balancing between current and voltage to support power-consumpting devices - with higher resistance you have to rise the voltage to get the same amount of energy through the lines without heating them ...

Maybe the idea of high-frequency-AC (>50kHz) with shielded line-pairs is a way too?

I have multilayer-PZT-actuators, which need a voltage of 48 Volts, but this can be adressed with a cascade, so 12 Volts and 100 mA current should work too.

For the material: in this special work we use so small droplets of the precious materials, that a bottle with 5 gramms ultrafine gold-powder (1 micron sized particles, nearly 300 Euros) is a one-year-dosis ...

For printing electronics it's much to expensive, so i would prefer to use copper or another common metall too.

Maybe it's interesting to try graphite or better a reducing receip, where the metall is chemically solved and with an added component will fallout and reduce to solid, so i can paint fluid lines, which converts to thin metallized films?

Viktor

... this is maybe usefull for other pastes too:

I found that dexpanthenol is reacting with my soldering glass-powder, so it can't stay longer time or it changes chemically, in consistency and in end-colour.

For this i searched for another solvent and found waterglass (water-soluble Alkali-Silicate).

It seems to be a perfect solvent for ceramic and some powders, it's used in paper-industry as glue/solvent, in mineral-paints for better fixing and in soap-powders as antioxidant shielding for the metallic machine-parts ...

As the fumes are weak toxic and korrosive, they should be ventilated and/or filtered away.

For me it's the next experiment-basis for glass- and ceramic-pastes (some tests with metall-powders too) for the SLS-fabbing ...

Viktor