Is cryomilling something easily available as a service?

[Alex Eisenhut]

Here's one of these ideas that pop into my head from time to time.

To repair approx 0.5" dia. holes in old plastic computer cases, simply take unusable parts of the same color and material from the same model and turn it into a powder as a feedstock for a patch compound. Removing any yellowed parts first, sanding it down if needed.

I'm guessing you need a very small particle size for this to work well, since the toluene plastic cement works best in such ratios.

The only way I can see turning ABS into a fine enough powder is cryomilling since anything else would melt it instead of pulverizing it.

I understand this technology is more used for testing materials or assaying and is not really a common industrial process?

Unless I buy some liquid nitrogen and a spice grinder...

Should I get back to playing Mahjong tonight or start buying Dewar flasks?

[JohnnyMalaria]

It's used in the pharmaceutical industry and comes with the corresponding price tag!

Liquid N2 and ceramic mortar/pestle would probably suffice. It depends how small you need the particles and how narrow the distribution. Commercial cryomills are designed to micronize materials and, with micronized powders, you really need to be careful about inhalation.

[Alex Eisenhut]

Death by inhaling a Commodore 64. Some eevbloggers might think it serves me right.... Looks like cryomilling is too arcane for my simple needs. When I find a crap case, I'll try to pulverize it with a beltsander with a drywall belt.

[ChristofferB]

Another alternative I've done (on accident!) a few times (with acrylic). I'm unsure of particle size and recoverability though.

If your plastic is soluble in acetone, dissolve it in a minimum of acetone in a test tube or similar. adding water to this should crash out your plastic as a suspension of tiny particles, as most plastics are insoluble in water, and water/acetone are miscible.

The finely powdered pastic precipitate could concievably be recovered by centrifugation, followed by washing with perhaps ethanol and then drying.

This requires a fair bit of tools and R+D. I would perhaps rather look into making a glue-gun style plastic extruder that took coarse plastic scraps as feed.

also, I agree, watch the inhalation!

[Gregg]

You could try putting plastic pieces and dry ice in a blender and see what happens; the cost is minimal.  If the particle sizes are too large, you could use a mortar and pestle after the blending.  The dry ice gassing off may keep the room air with its moisture away if you transfer to a narrow necked flask or bottle. 
The question remains, "will it blend?"

[Alex Eisenhut]

You could try putting plastic pieces and dry ice in a blender and see what happens;

Dry ice is used for the covid vaccines, guess I can wait a bit.

[jbeng]

Dry ice is used for the covid vaccines, guess I can wait a bit.

I wouldn't worry about using up all the dry ice so they don't have any left for the vaccines.  We have a Continental Carbonic plant here in my hometown that measures their manufacturing output in tons per day.  They're "right across the tracks" from another plant which manufactures ethanol for fuel and CO2 is their byproduct.  They pipe it straight over, cool it, compress it and there you have it.  Blocks, pellets, crystals - whatever you want.