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hi, can anyone help with a laminating steel or brass with a thin film of silicon? Answered

im buildng a mould for casing pcl (polymorf) there are issuse with using petroleum jelly as a release agent due to it clogging the pores, im building a highly porus biological scaffold for tissue engineering


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lemonie

Best Answer 8 years ago

It sounds interesting, but why use a mould like this? Couldn't you cast it in PP(?) then slice it or something?
I have some experience with polymer research - could you give us some details?

L

im designing a repeatable process, to create uniform scaffolds, im not sure a disposable mould will be cost effective.

The PP need not be disposable, I've worked with people produce macroporous PS in PP, cut it or plulverise, it plasma-surface treat it. What are you aiming for here?

L

ive done ps, its just not biodegradeable. ive only realy got the option of aliphatic polymers. pcl pga pla and combinations of the three. pcl has the best shelf life.

im using an emulsion to create the pores.

nice and easy. should get 90% porosity.

Yes I know the emulsions, can't remember the acronym though. Could you not just cast a block and cut it? (still don't know what you're doing here)

L

well it looks like im going to try a block approach, and use perspex, officialy the first biopolymer discovered. they found shards of it in bomber piolets eyes years after ww2, with out any irritation effects and he cell growth had encompased it  aposed to reject it.
anyway
the central spindle(removable screwed into the base) will be steel and petroleum jelly for release. this is due to the other agents dubious bio-compatability.

Why steel or brass ? 

Silicon even in thin films is extremely brittle, I doubt you can coat brass or steel with it,  because if the thermal expansion issues.
Did you mean Siliconerubber  ? Or are there particular reasons to use silicon.

Steve

+1
I don't know for sure, but I'd be willing to bet that siliCON and brass have wildly incompatible coefficients of expansion. Must be siliCONE, especially since the intended purpose seems to be use as a mold release.
What I don't get is why the silicone would need to be laminated to the metal, unless the whole mold has to be really thin. Seems like it would be easier to pour a silicone negative mold surrounded by a box to keep it from flexing overmuch.

Well sometimes you can back a thin silicone mould up with metal to support very fine, highly rentrant detail - but would you use polymorph for a copy ???

I wonder how viscous Polymorph actually is at moulding temperature ? 

Steve

I don't know Polymorph, but I gather it's similar to Friendly Plastic. If that's true, it'll take a surprising level of detail. Not nearly as much as something like a quality pourable urethane would, but still pretty impressive. Since I am unfamiliar with the specs for a biological scaffold for tissue engineering, I will assume that Polymorph is a suitable material for such a thing, and issues of temperature and hygene will not be a problem. Does one autoclave a tissue scaffold?

its a 3d structure hollow cylinder, i wasnt going to cast it im going to  use a solvent.

pcl, is bio degradeable, its an absorbant scafold.

also the size is very small and wih the porosity being above 85% the strength will be greatly reduced. the release mechanism has to be rigid as any bending will damage the scaffold

I think seandogue is on the right track with the mold release spray. You probably won't need much, since PCL doesn't chemically bond with brass or steel, so you'd just need to prevent a mechanical bond. Honestly, if you make your metal piece without undercuts, you shouldn't need a release agent at all, but better safe than sorry, right? You can just Google "silicone mold release" to see what's out there. There are some food-grade versions available, which may be suitable for your application.

ah but none of them have any biocompatablity data, i cant use it if it will kill or eve inibit the cells

occasionaly but with pcl it would destroy the micro structure. (with regards to autoclave)

the mould is creating a hollow cylinder with diametre 4mm, and a innner dia'  1mm
length 50mm

Since we think the plastic won't stick to metals, try it on a prototype piece first. Can the mould not be a two piece one , and the core slightly tapered ?

ill definatly put up the project as an instructable, but that might not be for some time.

Spray it with a silicone release agent, then use a shaker to make the coating uniform.

do you know any brands or names of the release agents?

No I'm afraid not. I know they exist from reading in various trade magazines and via other sources, but I haven't done any molding for years and years. I'd suggest that you do a net search for "release agent"

here's one for "silicone release agent"

excuse my manners, thank you all for answering.

Does it have to be porous? And why Petrolatum? How about something water soluble? Or carnuba wax with a spray of water-soluble laquer? The water-soluble laquer in question is hairspray.

it cannot have any carcenogenic or any residue that may be harmfull to cell growth, when in culture they are very suseptable to impurities.
petroleum jelly is often used medicaly with wound repair and in close contact with fluid systems and so im making an assumption that will not effect the biology too much.