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Saving Planet from the PET bottles

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This topic contains 2 replies, has 3 voices, and was last updated by  Brad Sheffield 5 days ago.

Vladimir vivlont

Saving Planet from the PET bottles

12/07/2018 at 00:29

Hi guys!Looking through the topics of the forum, I did not find a single discussion, where there would be specific information on the processing of pet bottles using an extruder (temperature, time, cooling method). And this is very strange! Because in most countries plastic bottles are the most “heavy” household rubbish. And it must be recycled!

Let’s take a look at this topic together!

From what I already know:

1) Prior to extrusion, the pet must be carefully dried so that the water does not boil inside the extruder.
2) The melting point should be approximately 270 degrees, but it must be selected exactly in each workshop separately.
3) Before extruding it is desirable to make plastic lumps (in a special machine that rotates hot knives and glues plastic into lumps).

We tried to extrude pet flex in our workshop, but we did not succeed.

We also tried to pass the plastic through a 3 mm hole, but it got stuck.We would like to make a filament for a 3D printer or some useful things. But for this, we need to develop (or find and publish) a technology for processing pet using Dave machines.


Let’s make it together!
Please, share your experiance on extrusion or compression PET!


P.S. I am not interested on this – https://davehakkens.nl/community/forums/topic/research-in-pet-plastic/

I am interested on something like this – https://davehakkens.nl/community/forums/topic/extruding-petg/

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12/07/2018 at 08:36

Hey there @vivlont

From my experiences & research, indeed PET is one of the hardest from the big 6 to recycle.


Extruding it is even a harder process as you want to dehydrate it before melting it in order to prevent hydrodegradation which completely destroys the polymers;
it is interesting to see you link a topic you do not want, in fact if you give it a try in an oven, you will see it will shrink and harden a lot (rise of density) and have a “minimal state” before the melting phase

The colour of your output tends me to think you didn’t get rid of the glue (used to stick the product information) which gives the opaque render.

So in my opinion you have to :
– really be careful your plastic is very clean (glue and remaining soda mainly); try avoiding PET which would have contained oil because it will modify the molecular structure of PET too and is very hard to get rid of
– have a dehydration phase (maybe a MUCH slower rpm and have a preheat section, but then i don’t know how the system could evacuate remaining H2O… so maybe a dehydration chamber very close to the extrusion hopper)
– no need to go such high temperature imho; 200°C+ is more than enough

hope that little info input helps out !

14/07/2018 at 06:07

With over 20 years working with polymers of thousands of different types, PET is by far the hardest to work with. Everyone will want to read this link about PET
“Why (and What) You Need to Dry”
You need to desiccate dry PET before extruding!

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