I just found the "Black Box" wine site, and learned that the bag inside their boxes is made of polycarbonate (7). This seems to have a certain lack of specificity; while polycarbonates can be used to make bulletproof "glass" etc. there is no way to tell just which polycarbonate it is. Also, the manufacturer cautions that a small amount of oxygen actually does pass through the plastic, so wine (or developers) will eventually deteriorate. They suggest a max 3 month shelf life. I suspect that this would be ok for the photo chemicals, also, and so I'm going to date the boxes if I choose to use them. Also, I found that certain chemicals are known to attack these plastics; among them are strong bases, including NaOH.
So, according to your suggestion, Paul, I'm looking for a kind of box wine container that contains PETE. The old ones I have used with such spectacular success had the silver mylar material; those don't seem ever to deteriorate. Odd, but the absolute WORST wine seems to come in those. The kind that they put under the display racks that have the bottled wine, or on the lowest shelf. I was using 5 liter containers from "Franzia"; I do know someone who drinks that stuff so maybe I can get more. 5 liters can be quite a lot for some chemicals, however. I think it would be worthwhile to try to find some other bottle sizes.
Anyway, I'm looking.