"Oogoo" rubber compound

Over at instructables somebody came up with a neat hack they called 'oogoo':

[www.instructables.com]

They mixed equal volumes of bath sealant (the type that smells of vinegar, not the newer high tech stuff) and cornstarch (aka cornflour) and found that it goes into a workable putty consistency in 5-10 minutes and sets in about 2 hours (normally that kind of sealant takes weeks, it's something about the humidity in the cornstarch).

You end up with a very usable casting rubber, with reasonable strength, and very inexpensive (about a penny a gram). It stinks of vinegar a bit after you've made it, but that wears off after a couple of weeks.

For reprap I think it should be possible to build a nozzle system to extrude it, it sticks to itself really well and is quite mouldable. It looks very doable for 3D extrusion printing.

For reprap this opens considerable possibilities- for example you could lay down moulds for glass reinforced plastic (dirt cheap and very strong), or epoxy (not cheap but very strong), and then you would get very strong, very rigid parts which last practically forever.

Polycaprolactone is not bad, but it tends to fall apart after a year or so, and while it has a high tensile strength, is not very rigid. It's also relatively expensive per gram. I'm not knocking it, but oogoo casting looks potentially pretty powerful.

Smooth-on has a variety of different casting and mold rubbers and plastics. What they also have are MSDS sheets for every product which tell you the hazards associated with using these things. There are some nasty things in some of these rubbers as cuing agents or catalysts. Might be worth a look.

RTV rubber hardens from the outside-in from the moisture in the air. Mixing in cornstarch accelerates the hardening because the cornstarch contains the needed moisture, and it doesn't have to migrate in from the skin of the blob of oogoo.

While there are some fumes when curing, afterwards it's pretty inert. You can find silicon caulking and cornstarch in most kitchens.

You can usually get a MSDS by searching for "[product name] MSDS"

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My blog's Reprap feed: [blog.markbova.com]
I'm currently working on a stock Mendel build with a Seeeduino Mega and four Pololu A4983 stepper controllers.

this stuff looks pretty slick. I have a few packs of sugru that I havent opened because I couldn't find it anywhere but now I can just make my own. I would love to see some type of extruder for this stuff. Guess the amount of cornstarch you add shortens the cure time. This seems very doable

bryan

Read it and had to try it. Excellent! RTV molds within four hours. It's still sealant so if you add only a little cornflour it still sticks like poo to a blanket, so you've got to experiment with PVA or silicon release agents, but with more cornflour it starts to cure pretty rapidly, so doesn't stick so well to non-porous items, allowing you to be less fussy about release. Lots of potential with this and so cheap and easy that it inspires a lot of experimentation. Best molding hack I've seen.

I tried this with about equal volume of silicone and cornstarch, along with a squirt of (cheap) acrylic paint and it worked great. I squished the 'oogoo' into a 3-part plaster mold and made useable replacement parts for a chain-reaction catapult toy.

i read about that too, i have been wanting to try it has well, i wonder if it would be doable to make a mixing extruder, so that you could get it to cure faster with out having to worry about it too much. something like a spray foam gun.

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[mike-mack.blogspot.com]

I mixed up a batch and made a few different shaped blobs, cones etc. but I’m not sure if I used the correct Silicon (it was not very acid-smelling) as it didn’t dry for 2 days, I guess it was not correct.

I tested it again and added Glycerine to the cornflour to make a paste before adding it to the silicon, this made it much easier to mix, and seemed to give it a much nicer texture for extruding, and it took 3 days to go completely hard.
After 4 days the Glycerine has started to leak out of the ‘models’ so it’s not ideally stable with the silicon I used, but that may also be a good thing mixed in the correct way.

People use Xylene Wiki to thin silicon when making compliant rubber surfaces for IR Multi-touch screens, so that may help get to the correct consistency, no idea what it would do to the cure-time or Cornflour

I’m sure you can add something else to make it take just the correct time to cure and also get the correct texture for extruding.

I’ll try a few other mixes, has anyone else tested this or thought about an extruding solution?

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[richrap.blogspot.com]

Is oogoo toxic if children put it in their mouths?

I would not personally suggest it, but both corn starch and window caulk are both generally non toxic.

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repraplogphase.blogspot.com

The silicone rubber that says its "aquarium safe" should be relatively non-toxic once fully cured -- that stuff doesn't have any metals or other chemicals that are toxic to vertbrates or invertebrates that will leach out, even at small rates and over prolonged times. However, some food-safe silicone sealant would probably be even better.. after all, who cares if a manufacturing flub poisons a bunch of pet fish and snails?

If you acquire your cornstarch from the supermarket, its food, so you can probably consider that to be non toxic too.

Assuming you can make oogoo from these two things, are they safe enough for your children? You'll have to educate yourself and make your own decision. Asking for opinions on a forum isn't really sufficient.
For example, I know aquarium safe silicone is pretty darn inert. I'd think nothing of eating a piece of it compared to a similar quantity of say, food coloring or food preservatives. But even so, I'd be a little squeemish about letting my young child suck on a chunk.

The MSDS is a good place to start informing yourself, but you'll probably need to compare them to other things you eat, like said food colorings and preservatives, to get a perspective. Or just get something that somebody else has already formulated and determined is safe for children.. you'll probably have to wait a while for an oogoo like product to be marketed that way though.

from the freely available patent of sugru which alledgely i have a copy, the following can be deduced:-

component x

hydroxy-terminated polydimethysiloxane -silicone base (also needs

activator) 175 grams


silica (cabot ts610) - sand (fine powdered mineral , glass powder) 875 ml

magsil daimond, 200 mesh (tacum powder) 42 g

water 11.9 grams



component y

polydimethylsiloxane (activator for silicone) 4.77 grams

silicone oil unknown quantity? (trace amount used to separate layers x

and y?)

dibutyltin dilaurate 0.43grams reaction catalyst for silicone?

tetrapropyl orthosilicate silicone cross linking agent 2.4 grams

tetramethoxysilane some sort of catalyst ?(hence the low grams of

this needed) 0.26 grams



phenyltrimethoxysilane
makes inorganic fillers i.e. (wollastonite) more hydrophobic and thus

increases their dispersability in mineral-filled
polymer in this case talc and silica (sand)


aminophenyltrimethoxysilane bonding agent, adhesion promoter, makes stuff more sticker to awkward surfaces




pigment trace amount


Breakdown of above info:

in one layer silicone(not water activated), sand, talc water,
in next layer trace amount of silicone oil(to keep two acive layers separate)
in final layer silicone activator,catalysts,
filling particles (talc and sand) dispersal agent, bonding agent

therefore with some experimentation, adding sand/glass powder and/talc may make the oogoo more plastic, just like the real stuff,
may-be this patent is a red hering so experimentation is needed,
also some extra bonding agent may be needed to make this stickier after sand and talc added to mixture,
any ideas please ?


my idea to make the oogoo transportable is to make a plastic tube out of plastic bag type p.v.c. using a plastic seam welder (brought from car boot sale)

to make a sausage skin tube,

fill tube with clear silicone (no air traped in tube)

tie ends of tube 1/2 inch from ends of tube. seam weld silicone inside tube at both ends.

in another tube, fill with (putty mixture),corn flour,water,sand,talc,pigment mix, with small wooden mixing stick.seam weld this tube to keep in moisture

this way it is possible to use this as a transportable batch to use anywhere in situ, just like the real stuff (sigloo )

of course experimentation to find cheaper fillers than talc, sand/glass powder is needed,
i am going to try plaster of paris,aluminium oxide, cerium oxide,finely ground rust (available freely on my car )

any other ideas please post!,

ITs never safe for children to put caulk in their mouth...


wolfkeeper Wrote:
-------------------------------------------------------
> Over at instructables somebody came up with a neat
> hack they called 'oogoo':
>
> [www.instructables.com]
> wn-Sugru-Substitute/
>
> They mixed equal volumes of bath sealant (the type
> that smells of vinegar, not the newer high tech
> stuff) and cornstarch (aka cornflour) and found
> that it goes into a workable putty consistency in
> 5-10 minutes and sets in about 2 hours (normally
> that kind of sealant takes weeks, it's something
> about the humidity in the cornstarch).
>
> You end up with a very usable casting rubber, with
> reasonable strength, and very inexpensive (about a
> penny a gram). It stinks of vinegar a bit after
> you've made it, but that wears off after a couple
> of weeks.
>
> For reprap I think it should be possible to build
> a nozzle system to extrude it, it sticks to itself
> really well and is quite mouldable. It looks very
> doable for 3D extrusion printing.
>
> For reprap this opens considerable possibilities-
> for example you could lay down moulds for glass
> reinforced plastic (dirt cheap and very strong),
> or epoxy (not cheap but very strong), and then you
> would get very strong, very rigid parts which last
> practically forever.
>
> Polycaprolactone is not bad, but it tends to fall
> apart after a year or so, and while it has a high
> tensile strength, is not very rigid. It's also
> relatively expensive per gram. I'm not knocking
> it, but oogoo casting looks potentially pretty
> powerful.