Why does high temperature ironing make clothes smooth?

Because clothes and other fibers have overall plasticity at high temperature, they will be flat when pressed with an iron.

Deformation is the nature of materials, and clothes are deformed as soon as they are wrinkled. Elastic deformation refers to the ability of a material to recover to its original state, also known as the elasticity of the material, which is the ability of the material itself. Although the material can't recover itself, it can recover itself under the action of external force. The composition of clothing material is fiber. When these fibers are dried, they will wrinkle due to evaporation in the process of natural drying, because the process of fiber dehydration will produce some forces such as stretching and shrinking. Wrinkled fiber will straighten under the pressure of water when it meets water, so when using iron, add water, strengthen heat and apply external pressure to make it flat.

When ironing clothes, you should spray some water on them first, or even line them with a wet cloth before ironing. If you bring dry clothes to iron, not only can you not iron the wrinkles, but it is also easy to scorch the clothes. When clothes are sprayed with some water, their fibers will get wet quickly. At this time, when an iron with the right temperature is placed on it, the water infiltrated into the fiber will be heated and evaporated. When a substance changes from a liquid to a gas, it absorbs a lot of heat from the surrounding environment, and its volume increases many times in an instant. Because the iron is pressed on it, the water vapor with expanded volume can't escape, so we can only drill hard into the gap of the fiber and squeeze the fiber straight and flat.