Thermos made of a pair of plastic bottles. Works!

There was no particular reason to invent a homemade thermos, but interest in the idea had long been in the air and sooner or later it had to materialize. I have already seen several options for thermos made from PET bottles, but they did not like the angularity, incomplete thermal insulation and other points. I had to think a little about how to effectively introduce a smaller bottle into a larger one, and even so that it was completely or almost imperceptible.

For the experiment, I selected containers for 1L, 1.5L and 2L. After all, he postponed one and a half, since the difference in diameters between it and a two-liter bottle is too small, and this can create difficulties in the manufacture of a layer of thermal insulation. But if a thermos comes out of a liter bottle, then I will definitely try sometime from a poltoraska.

Preparation

It was necessary to make sure that the inner bottle did not protrude outward and was hidden as much as possible inside the large one. To do this, I cut off the neck from a two-liter bottle with a grinder (you can use a sheet for metal), with such a calculation, so that through the hole from the inside it would be possible to insert tightly, or even better - to screw the neck of the smaller bottles.

The bottom of the large bottle also had to be completely cut off at about the level where the smaller container inserted inside ends.

So: I cut off the top and bottom, screwed in an open liter bottle from the inside and in this position I placed both containers in the freezer for a couple of minutes so that it would cool in the liter bottle air. I screwed the lid on it right in the freezer and proceeded to the next steps. The air in the 1 liter bottle then warmed up and created pressure.

Thermal insulation

Now the gap between the prepared bottles remained to be carefully filled with polyurethane foam. Just at home there was a little Ceresit foam under the gun, which does not greatly increase in volume when solidified.

I think any foam would fit here, not even under a pistol, only it would have to work more slowly and even more accurately. He filled the entire volume between the bottles, realizing that some of the foam would squeeze out. I just didn't take into account right away that it was necessary to spray water inside for a normal reaction.

I did it later, when the foam dried up a little and partially crawled out. In the cavity, we had to add some more foam locally. As soon as the water was added, the reaction went much more fun, the foam was well compacted and a very resilient insulating casing was obtained.

At first I also filled the lower cut-off part of a two-liter bottle with foam, but then I thought that this was not the right move and picked it out.

Final assembly

During the entire operation, the inner bottle remained twisted to maintain pressure and prevent the foam from crushing the bottle. The foam hardened for a couple of hours, after which I cut off the excess and proceeded to join the cut bottom with the main part of the large bottle. And even before the connection, I cut a hole in the bottom, through which later it would be possible to add foam to the resulting cavity and moisten the surfaces with water.

Having somehow coped with the bottom nozzle, filled the formed empty volume with foam and put it back to dry, after which all that remained was to clean the freshly baked thermos of adhered foam and check if the volume of the inner bottles. The check showed that it still decreased, but not much, by about 30 grams, which can be called a trifle.

IMPORTANT! As an experiment, I poured water at a temperature of 60-70 degrees into a thermos and placed it in the freezer. Two hours later, the water in the new thermos remained almost the same, except that it cooled down a little. So, the device works and, possibly, will soon be tested in combat conditions with chilled juice, mineral water, beer or something else.

In all likelihood, I will try to make a thermos from a one and a half liter bottle, but a little later. Here's a story. What do you think?

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