Making feedstock for the extruder

Some while ago there was discussion of the use of kitchen blenders as the means of reducing things like plastic milk cartons (and I notice that of the ones we get the goats milk ones are HPDE) to chips which can be fed into the extruder. Has anyone done this, and if so what experience is there as to the best kind of blender and blender blade to use to achieve the best results?

David

davidgoodenough Wrote:
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> Has
> anyone done this, and if so what experience is
> there as to the best kind of blender and blender
> blade to use to achieve the best results?
>
Didn't manage it with a blender. That didn't work for me. I used an old hand-crank meat grinder with indifferent results on HDPE milk cartons. Problem with HDPE, however, is that we haven't really solved the warping problem with it yet.

I've thought about using a standard crosscut paper shredder to cut consistent chips of HDPE. Some of them will take CDs and several sheets of paper. OK, it will only work on relatively flat sections, and you'll need to cut it up a bit first.

I've not tried it, only thought about it. I reckon it should work OK on the flatter sections, if you remove the corners.

DaveR Wrote:
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> I've thought about using a standard crosscut paper
> shredder to cut consistent chips of HDPE. Some of
> them will take CDs and several sheets of paper.
> OK, it will only work on relatively flat sections,
> and you'll need to cut it up a bit first.
>
> I've not tried it, only thought about it. I reckon
> it should work OK on the flatter sections, if you
> remove the corners.


Hmm, what about a 2-stage process, in which first you passively melt down your waste plastic onto cookie-sheet-like moulds that let you form thin sheets that could be fed to the shredder?

Or even a funnel that is passively heated and lets melted plastic flow out of the bottom, forming a thin stream of molten plastic that falls through the cooler ambient air, and lands on the ground already solid? Even if the diameter of the stream isn't consistent enough to be used in an extruder, perhaps a 2nd-stage recycler could be designed to remelt the coil into something more consistent.

I have put HDPE milk bottles through a crosscut paper shredder and took photos intending to blog it but I never got round to it. I cut them with scissors first so that they were approximately flat.

After one pass they are in strips stuck together by thin webs: -

[lh6.ggpht.com]

HDPE is one of those plastics that is very hard to tear, it just stretches very thin and gets very strong. There are some small chips as well though. Sieving it and putting it through repeatedly does yield lots of small chips.

[lh6.ggpht.com]

I don't know how long the shredder will last doing it.

Attacking it with a milling cutter produces a fine dust: -

[lh6.ggpht.com]

Using a hot funnel to melt it to a thin stream fed to a small milling cutter is appealing, but I think it is too viscous to flow under gravity unless you get it very hot and then you risk denaturing it.

Edited 1 time(s). Last edit at 07/13/2008 06:15PM by nophead.

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[www.hydraraptor.blogspot.com]

nophead Wrote:
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> Using a hot funnel to melt it to a thin stream fed
> to a small milling cutter is appealing, but I
> think it is too viscous to flow under gravity
> unless you get it very hot and then you risk
> denaturing it.

Oh, it will flow. It just takes a long, long time, probably a lot longer than anybody has patience for.