Special Formula Plastic Film

You can probably make it yourself, it's probably low density polyethylene...

https://en.wikipedia.org/wiki/Polyethylene

https://www.youtube.com/watch?v=dXmPQEEI5ig&ab_channel=StuartWinikoff

For 20 years I worked for a company that made many different plastic formulations, and use "PE" many many times but none was even close to the strength of this stuff.

The methods of treatment to the pe that produces the desired characteristics varies from manufacturer to manufacturer and the methods are likely to be proprietary...the methods are many...

https://www.researchgate.net/profile/Shashank-Mhaske-2/publication/267405888_Crosslinked_polyethylene/links/547d3ece0cf2cfe203c20265/Crosslinked-polyethylene.pdf

https://www.sciencedirect.com/topics/chemistry/crosslinking

https://omnexus.specialchem.com/selection-guide/polyethylene-plastic

My guess is that these bags are some grade of LLDPE...

"What is linear low-density polyethylene (LLDPE)?

The structure of linear low-density polyethylene (LLDPE) has a linear backbone with short and uniform branches (unlike longer branches of LDPE). These short branches are able slide against each other upon elongation without becoming entangled like LPDE. It is structurally similar to LDPE.

How is LLDPE manufactured?

LLDPE is produced by the polymerization of ethylene (or ethane monomer) with:

• 1-butene, and
• smaller amounts of 1-hexene and 1-octene.

This process occurs using Ziegler-Natta or metallocene catalysts. In the present-day scenario, LLDPE has been quite successful in replacing LDPE thanks to the below-mentioned properties."...

I know what you're talking about as I have noticed the same thing...I think the yield /break curve is something like this...

I guess if you know the characteristics you want, you could have a plastics engineer design the formula for you...

Need to be aware that the newer ‘green’ plastic is material from polymers derived from corn. Very short shelf life and UV sensitive.

‘PLA (Polylactide) is a bio-based, 100% biodegradable material made from renewable plant material (corn starch). Field corn is used to create the bags and is not suitable for consumption but is great to use as an end use for packaging materials like our bags.’

Europe has been using this for grocery bags for years. They would store stuff in the bags and store them in the attic and a few years later, the bags would decomposed into pieces,

Some manufacturers use potato starch.

https://www.carrierbags.co.uk/potato-starch-carrier-bags/

And wood pulp is also an option.

https://www.transpack.co.uk/brands/natureflex/

I prefer the thermal insulated expandable canvas bags....keeps your ice cream from melting and your lettuce from wilting...last forever and carry all your cold groceries in one easy to manage bag...

And canvass bags for the rest...

As far as I know, the plastic bags used around here do NOT decompose. I've seen a lot about plastics that are a danger to wildlife because they do not decompose.

Your photo looks a lot like what we call "T-shirt" bags.

I am not sure about the bags,but some plastic kitchen wrap is made from UHMW polyethylene.Very tough,and shrinks when hot.

I have used UHMW to form low friction skid plates when moving heavy equipment when no other method was available.

UHMW is more wear resistant than stainless or even tungsten,and a friction just slightly less than Teflon.

I think this link will answer most of your questions about plastic bag types and plastics in general.

https://www.webstaurantstore.com/guide/513/types-of-plastic-food-bags.html