What is the principle that the warm baby sold now makes it hot? It's like a plaster, but it will get hot if you stick it through clothes. It's disposable.

The reaction principle of warm baby is to use primary battery to accelerate oxidation reaction and convert chemical energy into heat energy. In order to make the temperature last longer, the product uses mineral material vermiculite to keep warm. Because the product can't react before use, the bag material should be very special, consisting of raw material layer, gelatin layer and non-woven bag. The non-woven bag is made of microporous breathable film. It must also have a traditional sealed outer bag gelatin layer. When in use, the outer bag is removed, so that the inner bag (non-woven bag) is exposed to the air, and oxygen in the air enters the interior through the breathable film. The time and temperature of heat release are controlled by the oxygen permeability of the gas permeable membrane. If oxygen permeates too quickly, heat will be released at once, which may burn the skin. If oxygen permeates too slowly, there will be no temperature. It is a dark brown solid after use, containing carbon powder, NaCl solid, Fe2O3 solid and magnesium aluminum salt.