Is PET, HDPE, anythig plastic worth scrapping into filament?

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Is PET, HDPE, anythig plastic worth scrapping into filament?

Postby allanonmage » 2013-Jun-Sun-09-Jun

Now that we have plans available for a cheap extruder, I've thought about saving plastic to grind up and then turn into filament. Not sure how the grinding up part will work yet, but I still need to build an extruder first, and I'm not so worried about the particulars at this stage.

However, what types of plastic are worth keeping to grind up and then extrude? I think PET is a viable plastic, and since I drink water our of bottles, I have a pretty good supply.

HDPE from milk jugs and zip ties seems a good idea too, though I drink less milk than water. Turns out motor oil bottles are HDPE too. And gas tanks. And who wants a plastic gas tank with a hole in it? muhahahaha I have a gas tank with a hole in it too. The hole is around the lip, so it's not practical to try to fix IMHO.

Anyways, am I headed in the right direction? Anyone else planning similar things?
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Started with a Printrbot LC Kit; now it's a monster as big as a mid size fridge!
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Is PET, HDPE, anythig plastic worth scrapping into filament?

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Re: Is PET, HDPE, anythig plastic worth scrapping into filam

Postby briankb » 2013-Jun-Sun-10-Jun

I would love to recycle all of the plastic I throw away each week as well as the bad prints.

Can you share a link to the plans for the cheap extruder?

I think if you can find a good cross-cut shredder you could modify it to use to reduce various pieces into a consistent size. It would need to have an adjustable width between the teeth, if possible. Or at least an adjustable set of rollers above the teeth to allow for larger items. The speed of the rollers would also need to be adjustable to allow larger items more time against the teeth for shredding.
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Re: Is PET, HDPE, anythig plastic worth scrapping into filam

Postby allanonmage » 2013-Jun-Sun-10-Jun

Yeah thats another ting.... I save my failed prints for later recycling.

As far as extruder... the #1 ir #2 sticky in this forum has a DIY extruder...

A scrapped paper shredder might for for the pet bottles if u took care of the harder and corner parts I suppose.

Would need a bigger one for abs chunks, but maybe just more gears or rows of gears would do it.
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Started with a Printrbot LC Kit; now it's a monster as big as a mid size fridge!
Single ATX Power supply, 650 watts, relay controlled heat bed
extra Z height (3+ ft) via longer rods, but I don't use it. Yet. To reduce wobble, I'm using thing:46082 under the Printrbot.
Dual heated beds, 1 currently working; space for a 3rd
Purple gluestick on glass seems to be sticky enough to get adhesion
FB album with pics: https://www.facebook.com/media/set/?set ... ec287e8726

This was supposed to be a tool, not a series of projects... grrrrr......
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Re: Is PET, HDPE, anythig plastic worth scrapping into filam

Postby jayceadeangelo12 » 2013-Jun-Mon-06-Jun

Whatever you do, please don't try to flame mely it as that will release dangerous toxic chemicals into the air and that wont eb any good for you who is melting it.
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Re: Is PET, HDPE, anythig plastic worth scrapping into filam

Postby allanonmage » 2013-Jul-Tue-09-Jul

I have quite the collection of PET bottle now. I need to start shredding them lol.

HDPE - milk jugs, oil containers, gas tanks, fuel cans, etc - seems like a really great thermoplastic to recycle. I'ts relatively soft and flexible, but except for milk jugs you have potential petroleum distillates to deal with.
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Started with a Printrbot LC Kit; now it's a monster as big as a mid size fridge!
Single ATX Power supply, 650 watts, relay controlled heat bed
extra Z height (3+ ft) via longer rods, but I don't use it. Yet. To reduce wobble, I'm using thing:46082 under the Printrbot.
Dual heated beds, 1 currently working; space for a 3rd
Purple gluestick on glass seems to be sticky enough to get adhesion
FB album with pics: https://www.facebook.com/media/set/?set ... ec287e8726

This was supposed to be a tool, not a series of projects... grrrrr......
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Re: Is PET, HDPE, anythig plastic worth scrapping into filam

Postby SeeFly » 2013-Aug-Tue-13-Aug

this is from taulmans site about t-glase which is some sort of pet/pett?

Environmental - While t-glase is not biodegradable like PLA, it is a material that’s considered 100% reclaimable. Thus the new “struders” that convert failed prints back to usable line work perfectly with t-glase. If you have a “struder”, you can actually mix in 12% of the total weight in discarded clear water bottles

i was looking at the filastruder website and they have mostly tested it on abs and it seems you need to put in alot of fresh material to prevent thermal cycling degradation.

im not a chemist but i was looking at my material science textbook and it seems to me that pla and nylon should be able to be broken down into their monomers and recycled to their original strength. if there is a chemist around i would love to hear their opinion on recycling of the various polymers and the processes required.
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Re: Is PET, HDPE, anythig plastic worth scrapping into filam

Postby deathbykindnes » 2014-Jan-Wed-08-Jan

Some printers (incl. RepRap) are using HDPE (#2), so that's certainly possible (melts around 125C, and it's almost half the price of ABS and PLA). But HDPE has more issues with shrink/curling due to a higher thermal expansion coef (about two times higher). It is much more ductile, and less geometrically stable at high temperatures-- it's not technically a solid (or glass state) at room temp like ABS/PLA. And it tends to fracture during extrusion since it's melt viscosity is more sensitve to extrusion velocity. LDPE (#4) doesn't behave much better for printer-size extrusion. It actually might be a bit worse-- it tends to have more variable properties.

So, I should say, they (Polyethylenes) have a different machine requirement. At this point, I don't think (printing) machines built for PLA, ABS, etc are correct for printing PEs.

HOWEVER, mixes of PLA and LDPE can extrude better than 100% PLA (usually with low percentages of LDPE-- 5%, 10% or so). LDPE is often used in mixture with HDPE for drawing processes and whatnot, because the smaller molecules act as a lubricant to the more massive HDPE chains. And I imagine some useful mixture exists with HDPE and PLA, for printing, that is. We'd have to keep track of the mixes, though, for further recycling purposes.


About breaking PLA into monomers for ("virgin") repolymerization, yes, that is very possible. With organic polymers, using enough pressure and heat (in a pressure cooker) will give the repeating units (lactide, currently poly-lactide) enough energy to break from each other, then to bond again with water to form lactic acid monomers. This reaction is spontaneous, though not sudden-- not sure on all the specifics for temp and pressure. Then, reducing the temperature will allow small polymers to form again. These are melted, and further cured to recreate long polylactide chains. The reason this isn't done more often is because other polymers require heinous temps and pressures for this to happen, and/or chemical reagents. But this is not the case with PLA-- it's (relatively) very easy with PLA. I'd have to do some more research about nylon.

Otherwise, what other recyclable polymers go through is a more simple chop-remelt-reform, which is a physical recycling process, rather than a chemical one. And this physical process can only be done so many times as the heating and cooling and chopping eventually DOES degrade the polymer at a molecular level. But with no (feasible) way to repair that damage.
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