A library book called Ecocraft had a project with laminating plastic shopping bags together to make a stronger and more durable material. My apprentices and I tried it out, and were able to make an improvement or two beyond the procedure in the book.
The basic idea is to place four to eight pieces of shopping bag between two pieces of kitchen parchment paper, and then iron them with a medium-hot iron, first on one side, let cool, then flip over and iron the other side.
The author recommended using clothespins to keep the layers from shifting, but we found that the plastic shrinks a lot as it is heated. So if the edges can't pull in as it shrinks, then the center will pull outward, and make holes in the middle.
One child also found that the loose edges could be folded over and ironed down, making the perimeter both neater and stronger.
If you let it cool down for a minute after ironing, the parchment paper and plastic will pop apart on their own.
The process gives off a few fumes, but not bad, at least not for humans. Just crack open a couple windows. I've been told that birds are very susceptible to this kind of household air pollution, though.
Shopping bags from mall stores seem to work best (#4 LDPE), followed by the better big-box stores, and then the super-thin discount and grocery store bags (#2 HDPE).
The resulting laminates are flexible and seem tough. The children called them "plastic leather", and the laminates made from tan grocery bags do look a lot like leather. Pinching and pulling on one, it stretches only very slightly until I pull very hard. I don't know about their abrasion resistance yet. A needle goes through it very easily.
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