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Separation by density
- This topic has 4 replies, 5 voices, and was last updated 4 years ago by
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Hi everyone,
In a quest to find the best sorting methods I made multiple post on different ways of separating plastics.
In this post I will explain separation by density.
A different approach to separation is to separate based on specific gravity, in this instance you have a range of containers each with a different density. You put the material in the different containers and by comparing the results you can determine what type of plastic it is.
@Ani0555 already did a lot of research in this.
The theory of separation by density
Material Density range
PP 0,90-0,91
PE 0,91-0,97
PS 0,96-1,04
ABS 1,06-1,08
PC 1,2-1,22
PET 1,37-1,45
PVC 1,35
However I found that this separation method is only useful for new material that do not include any additives. Additives can be added for the following reasons: Price, strength, fire resistance or as lubricants and can effect the density of the plastic.
+ easy to set up
– Problems if additives are used in the plastic
More pictures and info will follow
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Per density seems to be a nice way, but only in pure plastics, also, we have to add the “sinking time”, because people can get frustrated by waiting several minutes, for another amount of mixed plastic shredded to be separated. Also, this plastic needs to be clean firts and dry, in order to past by the different “density tanks”. Also, is better using destileted water in the mixes?
Other mineral i might influence in the result giving no so accurated results. Still just giving a feed back of the idea, iĺl like to give a try sometime soon
Hi guys,
This is the most affordable way to sort plastic. You can shred them and sort them afterward.
This is what I’ve been able to figure out for density sorting.
I still don’t know how to sort PET and PVC.
I also assume that using alcohol is quite tough because of its high volatility.
What do you think?
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Hi folks,
@mdem: Thanks for your chart, I had exactly the same idea, much of the plastic I collect does not bear any recycling information either because it is in many parts/broken or the manufacturer could not be bothered.
There is a similar topic on this at http://onearmy.world/community/forums/topic/how-to-seperate-pet-and-pvc-plastics-in-5-min/
I don’t know if it makes sense to bother to sort PET and PVC. According to @mathijsstroober in the topic http://onearmy.world/community/forums/topic/toxic/, PVC is harmful (releases toxins) and PET must be handled with care.
I am attaching my version, I did not test it myself and it is based on Dave’s sheet ”Floating properties” ie. 2_Floating properties plastic.pdf.
Can someone please let me know if it makes sense? Are there mistakes? Please feel free to contact me if you want to edit it/improve it/have the text file. It would be great to be able to recycle PET at some point!
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