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question re PVC/Polyethelene

Hi all,

Could some of you knowledgable folks please help me out?

I am not a poymer chemist, or even a chemist at all, but I have a need to find out if a plastic is PVC or PE. Is there a simple test? Also, I have heard that THF is the only real solvent for PVC, but if that is the case, how do the plumbing glues work? It says on the package that they are predominantly MEK, and they seem to glue the PVC pipes pretty well. I am wanting to make an adhesive for PVC that has a high loading of PVC in it. I added some MEK to some PVC powder that I have ( raw matl. for pipe extrusion) and the MEK did not seem to dissolve it, only soften it?? Do I need to go to the expense of THF to get the PVC to actually disslove?

And last of all.... does anyone know what the plastic is that the 4 litre containers that are used for Hyrochloric acid?? I have a lot of them from pool acid, and I want to fabricate something with some of the plastic. I was hoping that they are PVC and that I would be able to use a glue. IF they are PE is it true that there is no adhesive for PE?

Thanks in advance for any assistance.

Regards

Tim

Reply to
Tim
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Yes, the Beilstein test. But beware of dioxine.

Using the right solvent to discriminate between the two polymers is probably the better solution. Can't give you any advise on the best solvent, but PE should be left unaffected by most.

In our lab none of the containers for chemicals is made out of PVC. Mostly PE (and PP) are used. Look at the bottom of the container for HD-PE recycle symbols.

No, that's not true. Loctite and 3M are offering such products (quite expensive, I think).

Oliver

Reply to
Oliver 'Ojo' Bedford

I echo your disclaimer, I am not a chemist nor a polymer engineer ( I just play one on TV), but in the past couple of years, I have sold several million pounds of various types of regrind for recycling, and often the origin of the material was in question. We use the burn test to determine what type of polymer we were dealing with. When we burned PE (HDPE,LDPE, LLDPE) the smell of the burning sample was like the smell of a burning birthday candle. When burn testing PVC, the smell was an acrid chlorine like smell. The flame also self extinguished and the resulting "ash" was hard, black and crunchy (fragile, easily crushed). The flames and smoke were also different based on the type of polymer tested. See

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pictures of burn testing.

You can also test for the molecular weight by putting some small pieces of the sample in a bowl of water that has a few drops of liquid dish soap in it( the soap acts as a wetting agent) If the samples float, the density is less than 1, if the samples sink, the density is greater than

  1. PE has a density of roughly .92 to .96 (as long as the material is not highly loaded with very dense additives), the density of PVC is
1.35 so it will sink. (PET also has a density of 1.35 which make comingling of PET and PVC scrape a real problem). Also See
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will help you identify 4 types of plastics by the water test and burning (by observing the flame and also smell.) DISCLAIMER Although I have often personally tested plastic by burning it, there is an inherent danger in doing so. Hot plastic can burn you and the fumes from the burning plastic may be harmful to your health. Proceed at your own risk.

Hope this help Greg

Reply to
Gjpostma

Reply to
Tim

The best and simplest way to test for PVC is to use a small piece of copper wire. Heat the wire in a Bunsen flame until the flame is a pale orange colour - just touch the clean wire to your sample - place the wire back into the flame - if it burns green, the sample is PVC.

Cut a small sample of your polymer and place it directly into the Bunsen flame - polyethylene burns with a pale blue flame.

Peter P

Reply to
Peter P

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