Mixing LDPE & HDPE

Can LDPE & HDPE be mixed?

I can’t find clear research. But in my experiments it has been working fine… however I am highly interested in the long term stability of the mixture.

I understand that their polymer structure is different (linear vs. non linear) and I want to know how a composite will hold up (i.e. UV resistance, durability, flex, etc).

Anyone have any insight on this??


@yustina. Mixing these polymers should be just fine. Basically you are making a new type of MDPE. medium density. There are quite a few other polymers mixed together that we don’t even know about. The challenge you will have is that you probably will not get a good mixture unless you grind them up then run them thru the extruder and then grind it again and then mold your product. This should produce a good mixture.
The final properties will depend on the start properties and the only way to really know that will be to build test samples and do the tensile, flexural and impact testing to understand. UV resistance will only be there if the original polymers has it or you add the UV additive.
Please be careful when using the terminology “composite”. That refers to any resin with glass, carbon or other fiber added. Two polymers together are “alloys” or co-polymers.
Also, polypropylene can be a homopolymer or a copolymer. Homo means only polypropylene, Co- means polypropylene alloyed typically with polyethylene.

I hope this helps!

can we please talk about the additives on the concern of mixing plastics together?

please keep in mind that the word “plastic” means : polymer + additives.

Please do more research on that subject because (from my point of vew) i consider that it’s more the different types of additives which (once melted together) create potential problems
LDPE is low density PolyEthylene; HDPE is high density; when you talk about linear vs non linear; linear is another type of PE, LLDPE (linear low density PE)

I am actually working on a video in order to understand easier what a plastic is, and what are the biggest concerns in order to minimize the risks (for recycler & consumer of recycled product)

hope it helped !

ps : also, i mainly use LLDPE and HDPE/PP.

LLDPE is used as main mass of treated plastic; the PE &/or PP added (bottle caps) are added in order to “steal” the colour pigments from them and spread it into the molten LLDPE

Better to keep them separate, otherwise the product cannot easily be recycled again in the future.
Also they do not blend well together to make a uniform substance

Actually it’s not a good idea to mix them together , here in India people do it to save the cost . But in long run it doesn’t work out well  .the properties of both the plastic are different. Ldpe is more like soft and has elasticity, where as HDPE is soft but you can’t stretch it. You can mix HM plastic grade with LDPE it works fine with it . This both are mostly use in liner grades like making groceries bags ,  Medical glucose bottles. HDPE is less recative to most of the chemicals , where as LDPE is reactive to few chemicals , when in contact it can Melt and mix with the chemicals. Here in India HDPE is use to make packing containers for lot of stuffs .
. Let me know if I can help you in any way.
I am a Recycler by profession.