The principle of thermal insulation is that the heat released by the wearer can be used for storage and conduction, so as to achieve the effect of thermal insulation, and it is not the material itself that can generate heat.
Extended data:
Another principle is to use fibers to absorb water and heat. That is to say, when the fiber absorbs water, the hydrophilic groups in the fiber molecules combine with water molecules, and the kinetic energy of water molecules decreases, which is converted into heat energy and released. The moisture absorption and heating properties are closely related to the moisture regain of fibers. Fiber has high moisture regain, good moisture absorption and heating performance and low moisture regain.
So the principle of this kind of heating underwear is actually to absorb the moisture of the wearer to achieve the function of heating. Not suitable for dry north, sweating less in winter, it is difficult for fibers to absorb moisture and dissipate heat.
People's Network-Underwear Can't "Self-heat"