The reason why the insulation cup can keep heat is to draw out the air in the middle of the double-layer stainless steel to reach a certain vacuum. Let the heat of the water inside spread out as slowly as possible.
The reason why the insulation cup is not insulated
First, It may be that the seal is not good. Check whether there is a gap at the bottle cap or other places. If the cup cap is not tightly closed, it will also cause the water in your thermos cup to be not hot soon.
Second, the cup is leaking. There may be a problem with the material of the cup itself. Some insulation cups have defects in the process. There may be pinhole-sized holes on the inner liner, which will accelerate the heat transfer between the two layers of cup walls. Therefore, the heat is quickly lost.
Third, the cup with no buzzing sound in the interlayer is not a thermal cup. Put the thermos cup at the ear, and no buzzing sound can be heard inside the thermos cup, which means that this cup is not thermos cup at all, so this cup must not keep warm.
Finally, if your insulation cup has been broken heavily during use, it will also become uninsulated, because the vacuum layer leaks into the air and forms convection in the interlayer, which will not be able to isolate the inside and outside.
The above reasons are the most common reasons why the insulation cup is not insulated. If you want to test whether the thermos cup you are using has good thermal insulation effect, you can do the following experiment: pour hot water into the thermos cup. If the outer layer of the cup can feel hot, it means that the thermos cup no longer has thermal insulation function.
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