I knew about recycling plastic bags at home for a while but I've tried this idea just recently and it turned out to be one of my favorite DIY's ever. It's basicly all about ironing layers of plastic bags and melting them into a new pretty stirdy material that you can cut, sew and make cute things with.
The biggest "trick" is finding cute plastic bags or fun designs that you can place on top because that will make the finish look of your material. Once you prepared the plastic bags by cutting the handles off you should place them on a sheet of baking paper and layer at least 4-5 rows (I had some smaller bags so I placed one bag next to another to get the lenght but I still counted it as one row) . The best to use are the thin ones because they'll be the easiest to melt.
You will place the nicest plastic bag on top and optionally some cute design too. If you do, make sure to put another thin layer of see through plastic to protect the letters or design from falling off.
Once you are happy with how it all looks you put another sheet of baking paper and you iron the s*it out of it. First with minimum heat, then I add some more and by the end I'll blast the iron to the max -being super careful not to mess the whole thing up because in the worst case scenario it can go really bad - black or melted unevenly.
Once it cools down you have a nice material you can do a lot with. I have folded mine in two, I've cut the excess off and glued it together. I used super glue to stick the zipper first (make sure it's open while you are doing it and be careful not to mess it with up with glue!) and then the edges just to secure it. I folded the bottom a few times to give my purse some depth and then I sewed it together. And voila! :)