I have large areas to cover (84 cm x 70 cm, 150 cm x 84 cm, and 150 cm x 70 cm) with stretch film (22 µm thick, 45 cm wide).
The stretch film is not wide enough so I have to overlap several sheets to cover the whole area. Those areas represents the walls of a rectangle parallelepiped which will be filled in with water. I have enough stretch film rolls to wrap the frame with enough layers so that it can hold the water pressure.
The project goal is to create a custom size water tank(the project page hasn't been updated since I haven't found the correct solution so far).
To avoid leaks I need to make the first sheet thoroughly waterproof. That's why I want to kind of weld two overlapping sheets together so that they act together like a larger sheet (like when I weld steel parts).
So far I tried to "weld" two overlapping sheets with a hair-dryer (1900 W - maybe 120°C) but it just seems to stick the sheets (that can then be separated). I also tried with a thermal cleaner (400 - 550°C) and with a heat gun (300 °C) but both seem to be to hot as they tend to burn the external sheet and create small holes that are undesirable.
Consequently I am asking if it is even possible to weld two sheets of stretch films so that they act like a single one (it seems to be possible eg that company), and if so which tool I should use or which temperature I should reach and which one I should not exceed.
Thank you very much for advises !