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Polymers, Additives and Recycling

This topic contains 4 replies, has 2 voices, and was last updated by  Nicolas 9 months ago.

Nicolas imuh

Polymers, Additives and Recycling

13/09/2018 at 07:56

Hello Everyone !
So i have been doing researches on plastics these past months, and through differents experiments i realized that 2 different plastic products (from the same type) didn’t react the same when put to melt..

That’s when additives comes in as a parameter… here is a link to a pdf which enumerates the main ones (sorry the document is in french.. : www.inrs.fr/dms/plastiques/DocumentCompagnonPlastiques/PLASTIQUES_DocCompagnon_11-1/Les%20additifs%20.pdf )

Mainly, there are :
– Stabilizers
– Fillers
– Plasticizers
– Colorants
– Catalysts, Initiators & Accelerators
– Hardners
– Flame retardants

Knowing that the additives are NEVER mentionned on the plastic products and that some additives like the flame retardants can be VERY harmful, that leads me to think that different plastic products should not be put together (to melt) even if they are from the same plastic family (HDPE for example). Otherwise, we would just create frankenstein-like materials (cuz of all the additives we would have blended together). Furthermore, it can become VERY dangerous if some additives create bad chemical reactions while melted together…

What are your opinions on the subject ?

Thanks !

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18/09/2018 at 19:56

bingo nick!
there are now more than 5000 plastic recipes and growing…
eg. a purpose developed PP can have more than 80% talc filling (which, for its specific application could be a good thing – contrary to common logic, although sometimes its just to save money on polymer)

in my opinion a common rule of thumb is to start with known knowns;
1. if you know its food contact plastic put it on the left.
2. if you aint sure put it on the right
3. then proceed sorting as accurately as possible
4. if you want to make a food utensil…try to make sure its food contact quality plastic to start with (especially for greasy food)

ps. if you dont know right from left dont worry – get creative … you’ll think of something 😉

19/09/2018 at 09:43

Hey Terry !

Thanks for your input !
Are you sure you could just blindly put “food contact” plastics all together (obviously sorting by type of plastic). If i take the example of milk bottles here in france : they are made out of 2 layers of HDPE sandwiching a layer of carbon black.

In my opinion, this type of additive is totally screwing the recycling process (cf photo)
Would there be any other additives to look out after concerning food contact plastics ?

ps : i’m curious about your example of a PP product with 80% talc filling; what product would that “plastic recipe” be for ?

Peace !

24/09/2018 at 13:15

ok imuh …..lets clear up some (mutual?) assumptions
– i didnt direct you (or anyone else for that matter) to “blindly” put food contact plastics all together, besides it being an insult to all the blind fans supporting precious plastics, i perhaps mistakingly  assumed  that the well informed precious plastics community already sorts plastics into colour and known 1 – 6 polymers. No?
– the multilayer stuff you refer to would then be a no.7 No?
– read my rule of thumb no. 3 once more…and let it sink in using what you already know 😉
– PP with talc? ; – the 80% figure came from a polymer specialist & mineral supplier at a recent expo/conference.(i have no reason to doubt his info)
talc also appears to be an excellent filler to increase liquid barrier properties.
one use of high talc PP appears to be  washing machine parts – there was a dutch circular economy recycling initiative focussed on this recently.
-carbon black; – i thought it was a powder so dont quite understand how 2 layers of hdpe with a separate layer of CB can qualify as a hdpe monomaterial.
the milkbottle (uht milk?) sounds pretty dumb…but luckily some well informed  folks are beavering away at solving the multilayer phenomenon – https://www.seariousbusiness.com/innovation-projects/packaging/
…and just by chance Imuh, the folks in your own home country have just decided to ban plastics in school canteens.
– and just to balance the “black plastic is evil”sentiment, – yes it does suck when sorting machines cant see it and it contaminates the recyclate, but if used pragmatically black plastic can be a very useful asset (think of solar absorbers)
the answer is being well informed & then…

in case you’re wondering I’m not an expert Imuh – just an amiable transient with a busy schedule 😉
good luck with your research.

ps. from an asthetic perspective that dumb milkbottle looks kinda psychadelic – a famous dutch footballer once said “every disadvantage can have its advantage”…
like art creating awareness?

24/09/2018 at 14:17

hey terryball;

– thanks for anwsering. Maybe read my sentences a bit better as i did emphasize that the different types of “food-contact plastics” would be sorted.

– the photo i linked is #2 HDPE and not a #7 as you thought

– carbon black; as ALL additives/fillers/etc., are NEVER mentionned on the product and are used in every different types of plastics. In europe, just concerning the “food safe” plastics, there are 1068 different additives/fillers/etc which are allowed to be used

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