Heat patches produced by reputable manufacturers can still be used if they develop a bulge during use—this is a normal phenomenon. The bulging occurs because abundant oxygen around the patch accelerates oxidation reactions within its components. The gas produced during this reaction cannot escape the packaging layer promptly, causing the patch to swell.
Additionally, when a heating pad bulges, its temperature may rise significantly. If it feels excessively hot, remove the pad and let it rest for a while until the gas inside dissipates slightly before reapplying it to clothing.
What is the black powder inside heating pads?
Primarily iron powder, vermiculite, activated carbon, and other materials.
The black powder inside heating pads consists primarily of a mixture of iron powder, activated carbon, vermiculite, inorganic salts, and water. These are the key components that facilitate the heating process. When unopened, the iron powder is sealed within the transparent adhesive film, isolated from air.When the transparent adhesive film on the back of the heating pad is peeled off, oxygen from the air comes into contact with the iron powder through the non-woven fabric pouch. Catalyzed by inorganic salts and moisture, an oxidation reaction occurs, releasing heat to provide warmth.
The iron powder, activated carbon, vermiculite, and other components in heat patches are non-toxic and harmless. Therefore, normal use poses no risk to human health. Even if a heat patch accidentally breaks and the iron powder leaks out, it will not cause skin damage. However, if iron powder does leak, it must be cleaned up promptly to prevent accidental ingestion or inhalation into the respiratory tract.
What is the function of vermiculite in heat patches?
Insulation.
Vermiculite is an iron-magnesium aluminosilicate mineral named for its ability to rapidly expand and curl into leech-like shapes when heated. As a super insulator, adding vermiculite to heat patches extends their heating duration and maintains warmth, enhancing overall thermal efficiency.