[ricklin]

I work in the PET bottle business. Oxygen permeation through PET to the product inside is a big issue with customers. I understand that O2 permeation takes place due to partial pressure difference  between the inside of the container and the outside, but, what I don't quite get is what happens inside the bottle to make physical room for O2 molecules to come through the container. Does something leave or does it compress? Thanks.

Rick

[constant thinker]

What does PET stand for?

Personal Envisioning Thesis
Positron Emission Topography
Pets Envisioning Theories

Those are what I can think of PET standing for.

[Borek]

Google PET bottle - it is absolutely unambiguous.

[ricklin]

Sorry about that, PET is Polyethylene Terephthalate or the clear bottles they use for bottled water, soda, ect.

Rick

[constant thinker]

I never thought of googling it, sorry about that.

[billnotgatez]

I think this is a good question. I wish someone could answer it. I suspect it has something to do with what gasses leak out and the reactivity of oxygen to what is inside.

By the way a good disambiguation page can be found here.
http://en.wikipedia.org/wiki/PET
I am not sure I would have selected the order given, though.
When I Googled, I got a lot of stuff about animals.

[Dude]

http://www.msu.edu/~aurasraf/IAPRI2003.pdf

Permeability is related to partial pressure, not total pressure.  Since the partial pressure of oxygen in air is reasonably high, there is still a driving force for oxygen to get into the bottle.

[Dude]

Now that you've had a chance to read the article, here's my take.  It might initially be intuitive to invoke the concept of osmotic pressure and a semi-permeable membrane, however, I think it is likely simple solubility.  PET ( a plastic) is capable of dissolving gases to some extent (CO2, N2, O2).  Inside the bottle is a high CO2 content which will basically form a saturated CO2 gas solution in the free volume of the PET.  Outside the bottle is air which will form a saturated solution of O2 and N2 in PET.  Over time, the O2 will diffuse through the PET to the other side containing the CO2 at high pressure.  The concentration gradient will allow the O2 to seep into the high pressure environment.  However, going from high pressure to higher pressure is improbable, so it is likely an active state will form where the O2 will displace the CO2 inside the bottle to the PET layer and form a transient super-saturated solution of CO2 in PET.  The supersaturated solution will then release a molecule of CO2 to the outside to restore "equilibrium".