Raw material belt is a common auxiliary in liquid pipeline installation. It is used at the pipe joint to enhance the tightness of the pipe joint. Raw material belt is a new ideal sealing material. Because of its non-toxic, tasteless, excellent sealing, insulation, corrosion resistance, is widely used in water treatment, natural gas, chemical, plastic, electronic engineering and other fields. The crystallinity of raw meal is 90 ~ 95% and the melting temperature is 327 ~ 342 °C. The chemical name of the raw material belt is polytetrafluoroethylene. The common white polytetrafluoroethylene belt is commonly used in heating, ventilation and water supply and drainage. There are also special polytetrafluoroethylene belts for natural gas pipelines. In fact, the main raw materials are all polytetrafluoroethylene It's just that some of the processes are different. The relative molecular mass of polytetrafluoroethylene is larger, ranging from one hundred thousand to more than ten million, and is generally one million (degree of polymerization is in the order of 104, while polyethylene is only in the order of 103) . The average crystallinity is 90 ~ 95% and the melting temperature is 327 ~ 342 °C. The CF2 units in the polytetrafluoroethylene molecule are arranged in a zigzag pattern. Because the radius of the fluorine atom is slightly larger than that of hydrogen, the neighboring CF2 units can not be completely trans-oriented, but instead form a helical twisted chain The fluorine atoms almost cover the whole surface of the polymer chain. This molecular structure explains the properties of polytetrafluoroethylene. At temperatures below 19 °C, a 13 / 6 Helix is formed, and at 19 °C, a phase transition occurs in which the molecule is slightly unraveled to form a 15 / 7 Helix.