Hypothetically or Theorethically can ancient to medieval periods technology make non biodegradable plastic bag?

Question

To make it clear, I mean the period or timeline, so this include the entirety of the world during up to 1500, not just specifically the technology of ancient/medieval Europe, ancient/medieval Japan, ancient/medieval China, ancient/medieval middle east, ancient/medieval india, ancient/medieval south/north America, etc.

I want to know can the technology of the time make non biodegradable plastic bag or other modern plastic materials, and not due to natural occurrence or coincidence but deliberately produced using human technology in this periods.

Excluding "shellac", since I mean here is the non biodegradable shopping plastic bag that we use everyday in modern period, though correct me if they actually use or has shellac as one of the material components, since I am not knowledgeable with chemistry nor know much how plastic bag specifically is made industrially, if it is, then it is fine to include it, though I am not exactly asking for alternative using shellac to make bag, which is done even during ancient time, so at least that thing is excluded, since I already know of that.

also excluding leather, beeswax, wet clay pot, since @AlexP tell me thats also count as plastic.

• the technology here can be mix or combine from other culture/civilizations in order to make the plastic bag if certain technology in certain region or culture/civilizations is not enough or sufficient to do that.

• assuming the people in this periods know advance chemistry, so I won't accept reasoning that they can't make it because they don't know the chemistry. but I can accept the reasoning if even if they know the chemistry, their technology is insufficient to make it, even if combining the technology from other culture/civilizations.

for future reader, since sooner or latter comment in chat will disappear, i just copy paste @Nosajimiki comment regarding this "assuming they know advance chemistry" remember know and can make is a different thing.

There are plenty of things invented between 1500 and now that have nothing to do with Chemistry. Just because you can refine petrol does not mean you will invent the internal combustion engine. Many pre-industrial civilizations invented modern things but never figured out how to modernize with them. Chemistry, like the steam engine, was a huge game changer in our history. But as we know, the steam engine was invented LONG before we learned to make it useful.

Even with knowledge of chemistry, all of those things had to be discovered. Chemistry only tells us that A + B = C, it does not tell us where to get A or B to begin with, nor does it tell us that C is the end goal. That takes research and lots of it. I'm sure high explosives would happen quickly, but without understanding biology there are no artificial fertilizers, without mechanization, artificial fibers can't be mass produced, etc.

for my personal example (not from @Nosajimiki), historically theres many greek philoshoper that already know atom theory, that doesnt mean they suddenly know how to make atomic bomb or fusion/nuclear reactor etc and not make it less greek.

• reasoning that say they can't make it due to the certain region lack the raw materials component is out of the question, since it can be easily handwaved with the magic of worldbuilding, but again, I accept the reasoning if for example they cant extract certain materials even with the combination of technology from other culture in that periods.

I don't mind the finished product is crude or not perfect like our modern non biodegradable plastic bag as long they can make it, but of course it even better if it strong enough to hold stuff at least. and even better if their technology in that periods actually can make other modern plastic materials if they know the advance chemistry even if the result is crude.

feel free to correct my grammar or fix the tag to the appropriate one for my question, since some of the tag description/intention is not clear to me.

Answer 1

Next to no way.

"Plastic" is not a simple thing at all. In medioeval times they might have, relatively easily, obtained casein plastic from milk and acid (white vinegar or diluted muriatic acid).

With some ingenuity they might have had formaldehyde, getting methanol from pomace distillation and flowing it over a catalyser (hot platinum wire - supposing they had platinum). With a lot of handwaving, a suitable reason to even try could be concocted (after all, hyatrochemists such as Teophrast von Hohenheim for sure had already imagined worse).

Same goes for phenol. You get that from pyrolitic destruction of coal, and they already did that for some alchemical research. All it would have taken is for the alchemist to forget adding mercury and tin in the appropriate working, and do a lot of research on the results.

And that, in turn, with some more work, can get you Bakelite - a hard plastic.

Here is where things get really tough: for plastic bags, you need flexible plastic. So you need softeners (technically, "plasticizers"). Those, I'm really afraid you aren't gonna get. I am not an organic chemistry engineer and could well be missing a lot, but the simplest plasticizers all require processes and intermediates that just weren't on the stage before 1800 (and, at that, they only became really available mid-1900).

I can imagine some mixture of oils (castor oil was used to plasticize cellulose nitrate) and simple protein polymers that might be doable in the 1600's or even earlier, but they wouldn't be non-biodegradable (actually I'm afraid they'd start degrading even too soon) and I wouldn't rely on their structural properties.

Perhaps, just perhaps, casein plastic could be molded in threads and this could be woven into a flexible enough cloth. Rough, and still not completely non-biodegradable though. Nylon is a long, long way off.

update: difficulty of "modern" plasticizers

(As I said, not a chemistry engineer, so this is very approximate): to produce a modern plasticizer (not too modern actually) such as a phtalate, we need the base phtalic acid. This can be distilled out of coal tar, but the problem is that we need a very precise distillation to get reasonably pure product; and to have that, we need a reliable heat source and means of measuring pressures and temperatures. Neither was available in the Middle Ages. Daniel Fahrenheit will develop the first mercury thermometer in 1714, while pressure gauges begin maybe with Evangelista Torricelli and, but only with noticeable handwaving, with his teacher Galileo Galilei. So, I do not see an easy way of getting the require benzene derivatives in any reliable quantity or quality before, say, 1610.

Let's do it anyway.

We start with spirit of wine (this requires distillation, but not too much precision - it was done by Taddeo Alderotti in the thirteenth century but described by al-Kindi four centuries earlier).

Heat it to the fusion temperature of pure tin, with the appropriate addition of spiritus vitrioli. The resulting vapours are filtered through a cooler filled with finely powdered nigrum spiriti argenti (which was unknown in the Middle Ages, but can be handwaved as a byproduct of silver refining - first you get "Devil's copper", or kupfernickel, and from large quantities of that you can maybe get platinum. You don't need much, fortunately). We also need to assume that the process has been improved enough to avoid the significant chance of it going "kaboom" here.

The resulting waxy slush requires little plasticization, and can be perhaps be melted and become a thin layer over some suitable substance (not tin, not most oils. Maybe some rarish metal or alloy such as gallium or Rose's metal? Or something as simple as beeswax?) at a reasonable temperature above fusion, say 150 °C. Then the layer can be lifted and crafted into bags.

Answer 2

Exactly modern grocery bags, no

Exactly the same, no. Modern grocery bags are made from very precisely refined polymers which require thermometers to get to the exact properties you would be looking for. Thermometers are a post medieval tech; so, even with a perfect understanding of chemistry, you can not refine elements to exact temperatures without one. If you can't control temperatures exactly, then you can't manipulate your base materials to get pure and precise chemical reactions to get plastics with exactly the properties you want. Because grocery bags are so thin, even minor impurities would cause them to fall apart.

Something similar to modern grocery bags, yes.

Latex rubber was invented around 1600BCE by the Aztecs and is forgiving enough to work with without a thermometer, and various kinds plants that could be refined for the stuff exist all over the world. The issue with natural latex is that it was no stronger than an eraser until people figured out how to vulcanize it by heating it with sulfur. Natural sources of relatively pure sulfur were known to many ancient civilizations such as the Greeks and Chinese as early as ~600-500BCE, and the Chinese learned to refine it around 300BCE.

With access to relatively common resources and a little bit of experimentation, it would have been as simple as boiling the resin of the right kind of plant with the right kind of rock and you'd have vulcanized rubber. Your bag's properties would more closely resemble a ballon than a modern grocery bag, but it would be a biodegradable polymer based sac that could serve the same function as a grocery bag.

That said, these ballon bags would be possible, but not the most probably application of the technology. In the pre-industrialized world, almost nothing was disposable. Everything was so much effort to make you would not just throw it away when you are done unless it was actually ruined by its intended purpose (like wine skins); so, your people would probably use such as bag more as a satchel or tote bag than something they hand out for free at the marketplace. So, a more realistic application of flexible plastics in the ancient-to-medieval world would be to use whatever plastic or rubber you have and use it to waterproof a linen or leather satchel so that the base material can give it structure and the polymer can make it waterproof. This way, even if it is technically biodegradable, it will still give you a simi-permanent useful item for your effort of making it.