sort HDPE and PP
I have a mixture of bottle cap flakes which contain mixture of HDPE and PP plastic. What is the easiest way to separate the two types of plastic? Quantity is 50 metric tonne so difficult to try home based methods.
I have the same question! Hope someone has a good answer 🙂
Let’s have a look:
as you mentioned, home based separation methods are not suitable.
-Separation by density is difficult, because they are very similar.
-Separation by infrared light: Hdpe and Pp reflect infrared light in different strengths. There are machines that separate shredded plastic on a conveyorbelt by analyzing this reflected light and blowing them in the right bucket with compressed air at the end of the belt.
-Separation by static charge.
If you let your particles fall down inbetween two metal plates with a huge difference of voltage (around 100.000 Volts I think) one of the plastic sorts will fall a bit more towards one side than the other. You would have to regulate the voltage (I think) to have the biggest difference of which side the particles fly, so basically you could put your buckets in these two areas then. But be super careful when handling with such high voltages, they can conduct through air up to some metres of distance. Risk of Death!
but yeah, in industry scale its no problem separating them, small scale is more of a problem.
I hope this helps,
all the best from Austria and good luck finding a suitable solution,
yours Flo 🙂
Flo, what a great answer. May I ask if there’s a mid-situation? I mean not ‘home based method’ but not this one of 100k volts.
I’ve heard something related to their floating properties, can anyone please confirm this?
Picture is of pill bottles with caps, mixture of polyethylene and polypropylene. The steps involved were granulation, removal of the paper contamination from the regrind, dewatering and drying of the flake, then introduced into liquid of correct density to separate. The Polyethylene is in the bottom of the glass while the Polypropylene is floating. We are currently building a system to process 1000 kg per hr of the regrinds. https://www.youtube.com/user/dms1230
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