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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.

This is what I want to achieve : Frame covered with stretch film

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 !

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  • $\begingroup$ Probably, try designing a heat sealer to suit your application like they do for sealing food stuff bags. $\endgroup$
    – Solar Mike
    Apr 10, 2023 at 20:56
  • $\begingroup$ Is there any advantage to this approach when you could buy a fully sealed bag that you could put into a frame? $\endgroup$ Apr 11, 2023 at 20:20
  • $\begingroup$ @TomášLétal it's a diy experiment. If this happens to be feasible then anybody can do it with simple, light and very affordable material. Can you imagine a water tank that can have many shapes made out of bamboos and wrap film ! Of course if you already have eg an old pool liner laying around then you could use it and it may be easier. One advantage of wrap film is also that it is wrapped AROUND the frame (so there is no effort on the frame). Do you have examples of web sites selling custom size sealed bags (just to check if it is expensive) ? $\endgroup$
    – Cara Duf
    Apr 12, 2023 at 2:53
  • $\begingroup$ @CaraDuf I think much better solution for variety of sizes would be simple garbage bags. You can use multiple layers if needed, it is cheap and can be made from recycled plastic. My guess is that you will have a hard time trying to beat this with stretch film. You will need more of it and sealing it will take some effort. $\endgroup$ Apr 12, 2023 at 15:52
  • $\begingroup$ @TomášLétal How would you assemble them together to meet the dimensions of the frame ? And which type of garbage bags do you envision for that, the ones that are thin and stretchable or the ones that are a bit thicker, more solid and not stretchable (maybe made of PVC) ? $\endgroup$
    – Cara Duf
    Apr 12, 2023 at 18:21

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It's not yet an answer but that's useful hints! So consider it as an interim solution.

I have just made some experiments and I can tell when holes appear in stretch film while heating it with heat gun and when they don't : actually it depends on whether the film is already stretched (even slightly) or not.

So one solution would be to make the walls aside from the walls (apart, eg on the floor) and then gently put it on the frame. That's not easy but as soon as the film is stretched it's very hard to avoid holes when "welding" two sheets together. Whereas without tension the sheets can melt and merge together before holes appear.

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