There is generally no metal foil paper in KFC's cartons. Moreover, when paper items are heated by microwave oven, there is no danger, but the heated KFC carton has a high temperature and needs to be taken out with gloves. The principle of microwave heating. When microwave is radiated to food, food always contains a certain amount of water, and water is composed of polar molecules (the positive and negative charge centers of molecules do not coincide even when the external electric field does not exist), and the orientation of such polar molecules will change with the microwave field. Due to this movement of polar molecules of water in food. As well as the interaction between adjacent molecules, it produces a phenomenon similar to friction, which makes the water temperature rise and the temperature of food rise.