. . Plastic chemistry. . . . there is indeed some variability in how the plastic is made
* different polymers have different properties. Some are resistant to oils, some are resistant to water (polar molecules), some are resistant to oxygen, some are resistant to oxidizers, some work well with an impulse sealer, some are good substrates for atomized aluminum or silicates, etc etc. Many food containing containers are made up of multiple plastic layers so that different properties can be combined.
you are asking about oxygen permeability coefficient (cc of gas x
mm thickness/square meter of test plastic x
atmosphere pressure at 20C)
HDPE comes with oxygen transmission rating of 44-91, LDPE comes in at 98-138, PET as in plastic carboys is rated at less than 1, aluminuumized films are less than 1 (basically zero except for the pin holes), silicone as in stoppers is rated at 40,700. etc etc different polymers are good at different jobs
* the tank manufacturer should have an oxygen transmission specification on all equipment designs. As with metalized films the defects/ bubbles always cause some variation from tank to tank. Using natural oak wood there is variation in measured transmission from barrel to barrel too.