Questions regarding the differences in plastic

Hey there, I am new to the world of plastic and was wondering, what kind of plastic the typical foils for packaging were – you know, from tomatos to cigarettes, the thin stuff. Would be great to know! Best regards, Heinrich


Hi Heinrich! it’s LDPE, Low density Polyethylene, mostly

Has anyone tried to mix LDPE with PS, if so what were your results.


be careful of what n°7 you are working with.
n°7 is all other types of plastics. So if you work with PLA (n°7), don’t put it to melt with another type of plastic from category n°7

Hey Nicholas, wow, thank you very much!
Ok, I see, no mixing of categories, but is it possible to mix plastics from category 7? Actually, I would like to use foils and melt them together for new foils – would that be feasable?
Best & thank you again,

they are called the “Big 6”
1. PET
3. PVC
5. PP

6. PS
7. other types of plastic or coextruded plastics (ie:PP/PS)

So PE is a special polymer, as it’s used in many different densities and is communly used in our society (HDPE & LDPE are seperate groups, but there is also LLDPE & LLLDPE) :stuck_out_tongue:
PS has 3 subcategories : PS Choc, PS Cristal, Expanded PS

But the number system is the same for other materials

You really never want to mix different plastics together (but for your info, recycling industries in France shred and melt together PE & PP, they consider it has no impact as long as there isn’t more than 5%PP in the PE flow)

Hey Nicolas & PeiPei,
thank you for your answers!!!
Ok, so basically there are the 7 main groups of plastics (1-7) that should be shown on the plastic itself. And than there are subcategories, as I understand from you, Nicolas?
I am mainly asking out of interest (of course) and than, as I read that the different plastics should not be mixed when shreddering and melting, in order to get a solid result. Or wouldn t you agree?
Best from sunny Munich,

hey @heinrich

concerning films; here is a little trick which might help

film can be PE (HDPE & LDPE) , PP or PS, if your finger can go through it like a vegetable bag from supermarket then it’s LDPE;

PE & PP have very similar properties as they are from the same family : Polyolefine

PS has different properties, the most important one (i guess) to differenciate PS from PE/PP is it’s density. PS (except subcategory PSE) sinks when PE/PP floats in water 😉

Beware of co-extruded products (PE/PS, PP/PS, etc…) and presence of aluminum (which isn’t plastic , duh… :p)