Oxygen permeability of various chemical storage materials

[WilmarcoImaging]

This information is to help guide in choosing the best containers to store photochemicals, to reduce oxidation as much as possible, for improved storage life. For color chemicals, the main interest is with developers.

Values are for oxygen transmission rate, units are in nmol*m-1*s-1, at 23 deg C and 0% relative humidity, per https://repositorio-aberto.up.pt/bitstream/10216/88820/2/25962.pdf

Low density polyethylene (LDPE): 500-700
High density polyethylene (HDPE): 200-400
Polyethylene terephthalate (PET): 6-8
Ethylene-vinyl alcohol (EVOH): 0.03 - 0.12

PE is used for traditional brown photochemical jugs.

PET is used for beverage bottles.

EVOH is used for food packaging, including some wine storage "bag-in-box" systems.

 

[halfaman]

Or use the good old glass containers. No permeable to gases and last forever... As long they are not hit.

 

[Chris Livsey]

Although interesting work there are other sources that have figures derived much more robustly. Those quoted should be interpreted with care as 0% relative humidity is not a commonly encountered environment for storage of photochemicals and the thickness of the vessel can easily switch the "league" table around, a thin vessel with low permeability is less effective than a much thicker one with higher permeability, ageing of the plastic which can change its properties can be another important factor neglected here. It should also be noted that permeability increases about 5% per degree Celsius rise in temperature and conversely reduces by the same rate but of course cooling may affect the solubility of the ingredients.
The manufacture of the container can also be a factor, in crystalline polymers orientation will reduce permeability, PET in particular requires knowledge of the structure to draw conclusions, that is not disclosed in the container markings. No consideration is given for the type of closure which has a profound effect on the system.
On method you may like to compare the source quoted with these:
https://www.plastictechnologies.com...rmeability-measurements/oxygen-container.aspx

The elegant solution, as noted above, is to use glass. Its main disadvantage, other than physical stability, is weight which is a major consideration for transport but in darkroom work hardly a consideration.

 

[mfagan]

Chris,
If numbers are available for comparison with those above, can you comment on common glass containers — and additionally borosilicate glass. Years ago I invested in some borosilicate glass bottles with plastic caps. Wondering whether that made any difference in keeping properties of chems.
Thanks.

 

[Chris Livsey]

Chris,
If numbers are available for comparison with those above, can you comment on common glass containers — and additionally borosilicate glass. Years ago I invested in some borosilicate glass bottles with plastic caps. Wondering whether that made any difference in keeping properties of chems.
Thanks.

The limiting factor under normal conditions for glass/oxygen permeability is the closure of the vessel mainly in how effective a seal it makes not the container itself. For the purposes of comparison of the container alone permeability of oxygen is essentially zero under normal conditions of temperature and pressure. So in your example the seal of the plastic cap is the limiting factor.
(Normal conditions excludes uses for glass such as in the reprocessing of spent nuclear fuel which is converted into a borosilicate glass at the Sellafield Waste Vitrification Plant and requires the accommodation of helium produced by alpha decay and oxygen generated by radiolysis within the waste escaping the glass below the glass transition temperature)

This is an interesting and probably overlong review of the plastic side with a food bias:
http://www.tappi.org/content/pdf/member_groups/packaging/plc98119.pdf

My interest BTW comes from pharmaceutical packaging technology as a Pharmacist

 

[Wayne]

Everyone can agree that less gass/oxygen transfer is better for developers. But nobody to my knowledge has ever answered the question of how much is too much, or how little permeability is required to achieve Desirable Resulting Shelf Life XYZ. Of course it will vary depending on what is being stored. I always err on what I consider to be the side of caution and use PET, but does anyone really know that the greater permeability of HDPE will result in unacceptably shorter shelf life of most developers over say 6 or 12 months?

 

[Chris Livsey]

The work required for that evaluation is probably beyond what a sane person would contemplate, as a first hurdle define "Desirable Resulting Shelf Life" and how that would be measured with any accuracy and precision. The work involved is out of proportion of the level of information gained as good strategies already exist to mitigate the effect, as outlined glass storage, establishing your own established shelf life, reading and adhering to the makers instructions and probably best of all shooting enough film so developer life is moot

 

[mfagan]

Thanks Chris, for your answer.

 

[AgX]

Values are for oxygen transmission rate, units are in nmol*m-1*s-1, at 23 deg C and 0% relative humidity

Low density polyethylene (LDPE): 500-700
High density polyethylene (HDPE): 200-400
Polyethylene terephthalate (PET): 6-8
Ethylene-vinyl alcohol (EVOH): 0.03 - 0.12

For the negligent reader the table you quoted may be deceiving.

As he likely overlooks that the given values are dependant on barrier thickness and that this thickness may vary substantially.
So, one barrier may the same time form the structure of the container itself, whereas another may only be a rather minuscule layer laminated to the structure.

 

[Rudeofus]

There are other effects at play which limit developer shelf life, such as hydrolysis or slow thermal decomposition of components.

Therefore it is quite easy to state an optimum permeability for Oxygen: low enough to make oxidation less prominent than the other deterioration processes, while keeping packaging cost low enough to create a viable product.

 

[Rudeofus]

So, one barrier may the same time form the structure of the container itself, whereas another may only be a rather minuscule layer laminated to the structure.

Even if EVOH is coated as an ultra thin 1 µm layer, it still blocks Oxygen better than a whole centimeter of PET. So yes, these numbers are very relevant IMHO.

 

[AgX]

1µm against 1cm is a 1/10,000.
The difference in permeabillity though is only about 1/100. So in your example the thinner layer would be 100-times worse...

 

[WilmarcoImaging]

Agree with Chris that for high performance plastics like PET and EVOH, and glass, the closure (cap) is the weak link in the oxidation discussion. So I would propose the conclusion is, that glass, EVOH or PET containers are far better than PE containers, from a prevention of oxidation point of view.

Also agree that shooting and processing film faster than developers oxidize, is the best way to assure chemical freshness!

 

[Wayne]

People store paper developers too. If storage life wasn't a concern for many this topic would never come up.

 

[mshchem]

This is great information. Actual data.

I used amber glass 1 qt. and 1 gallon bottles with Poly Seal lids for years. I then gradually switched to PET bottles. Now I use PET and HDPE bottles. I've found that far and away, in my experience, that the air left in the ullage (the unfilled air space at the top of a bottle) was the biggest factor. (I learned about ullage from watching space race as a kid ).

Everything photographic seems to be shipped in some version of PE. PET will fall to pieces around color developer concentrate, I made the dumb mistake of splitting an E-6 kit and one component of the CD into PET, it cracked the PET. I split stock solutions into 1 L, 500ml, 250 ml and 125ml bottles full to the very top of the bottle. I still use PET for dilute solutions, but going forward I will be buying HDPE.

When splitting kits I use butane to displace any air.

I still have some of the beautiful Boston Round amber glass bottles, but for me too heavy and I hate cleaning up broken glass.

Good discussion, Mike

P.S. I found an 11 year old bottle of XTOL in a "squeezed out" PET soda bottle. Looked like a nice wheat colored Pilsner beer. Worked fine on a roll of HP-5, I was amazed!

 

[Wayne]

The work required for that evaluation is probably beyond what a sane person would contemplate, as a first hurdle define "Desirable Resulting Shelf Life" and how that would be measured with any accuracy and precision. The work involved is out of proportion of the level of information gained as good strategies already exist to mitigate the effect, as outlined glass storage, establishing your own established shelf life, reading and adhering to the makers instructions and probably best of all shooting enough film so developer life is moot

But without that knowledge, or at least something resembling it (like an abundance of carefully accrued anecdotal information), the numbers on permeability are rather meanigless. It doesn't matter if the permeability is X/Y if the amount needed to adversely affect the solution is unreachable under normal conditions. If one material is adequate and another is adequate times 10, is it really better?

I'm just playing devil's advocate here, not trying to argue that more permeable materials are adequate. I'm arguing we don't seem to have enough information to know one way or the other. Therefore using the less permeable material seems prudent, but that doesn't mean its necessary.

 

[AgX]

I too wondered long time about lab glass manufacturers not being concerned about permeability issues of their plastic caps.

Concerning beverage plastic bottles:
at its best we know of their base material, but we remain ignorant about any enhancement, thus such tables are only of academic value.

 

[Rudeofus]

1µm against 1cm is a 1/10,000.
The difference in permeabillity though is only about 1/100. So in your example the thinner layer would be 100-times worse...

I incorrectly wrote PET instead of PE, and for PE the factor is even bigger than 10000. While my original statement is incorrect, the overall issue raised by it exists.

 

[WilmarcoImaging]

Wayne, whatever conclusion arises from the data applies also to paper developers.

Chris, I looked at the TAPPI link and saw a measurement method, but no data. Maybe I missed something. Here is a TAPPI article comparing plastics. Page 3 has a table of values at room temperature and 65% relative humidity. The relative order of oxygen barrier performance is generally the same as the repositorio article: http://www.tappi.org/content/enewsletters/eplace/2004/27-1Armstrong.pdf

 

[mshchem]

I worked for General Mills for a couple of years while attending University. There was a TAPPI lab, didn't see much activity, had equipment to measure how much force was required to bend a flap on a Cherrios box, how slippery the cartons were etc. I never really knew what the TAPPI acronym was. Technical Association of the Pulp and Paper Industry, there you go. All I know was we took Cherrios very seriously, fresh out of the expansion guns, very yummy. Perfectly pristine place.

 

[Wayne]

Wayne, whatever conclusion arises from the data applies also to paper developers.

I know, that's why I mentioned it in response to you saying"processing film faster than developers oxidize, is the best way to assure chemical freshness!"