The main reasons why polytetrafluoroethylene can be used for steel lining plastic anti-corrosion are as follows:

1. Non adhesive: Almost all substances do not adhere to polytetrafluoroethylene coatings. The very thin film also exhibits good non adhesive properties.

2. Heat resistance: Polytetrafluoroethylene coating has excellent heat and low temperature resistance characteristics. It can withstand high temperatures up to 300 ℃ in a short period of time and can be continuously used between 240 ℃ and 260 ℃. It has significant thermal stability and can work at freezing temperatures without becoming brittle or melting at high temperatures.

3. Sliding property: Polytetrafluoroethylene coating has a low coefficient of friction. The friction coefficient changes when the load slides, but the value is only between 0.05-0.15.

4. Moisture resistance: The surface of the PTFE coating is not wet or oily, and it is not easily stained with solutions during production operations. If there is a small amount of dirt, it can be easily removed by wiping. Short downtime, saving time and improving work efficiency.

5. Wear resistance: It has excellent wear resistance under high load. Under a certain load, it has the dual advantages of wear resistance and non adhesion.

6. Corrosion resistance: Polytetrafluoroethylene is almost not corroded by drugs and can protect parts from any type of chemical corrosion.

PTFE (polytetrafluoroethylene) is a polymer of tetrafluoroethylene. The English abbreviation is PTFE, and the trademark name is "Teflon", which is known as the "king of plastics". The basic structure of polytetrafluoroethylene is- CF2-CF2-CF2-CF2-CF2-CF2-CF2-CF2-CF2-CF2-。 PTFE (polytetrafluoroethylene) is one of the best corrosion-resistant materials in the world today, hence it is known as the "plastic king". It can be used for a long time in any type of chemical medium, and its production has solved many problems in China's chemical, petroleum, pharmaceutical and other fields. PTFE seals, gaskets, and washers PTFE seals, gaskets, and sealing washers are made by molding suspended polymer PTFE resin. Compared with other plastics, polytetrafluoroethylene has excellent chemical corrosion resistance and temperature resistance, and it has been widely used as a sealing material and filling material.

Polytetrafluoroethylene has a relatively large molecular weight, ranging from tens of thousands to over 10 million, and generally in the millions (with a degree of polymerization on the order of 104, while polyethylene is only 103). The general crystallinity is 90-95%, and the melting temperature is 327-342 ℃. The CF2 units in polytetrafluoroethylene molecules are arranged in a zigzag shape. Due to the slightly larger radius of fluorine atoms compared to hydrogen, adjacent CF2 units cannot be completely trans oriented, but instead form a helical twisted chain, with fluorine atoms covering almost the entire surface of the polymer chain. This molecular structure explains the various properties of polytetrafluoroethylene. When the temperature is below 19 ℃, a 13/6 helix is formed; At 19 ℃, a phase transition occurs, causing the molecules to slightly unravel and form a 15/7 helix.

Although the breaking of carbon carbon bonds and carbon fluorine bonds in perfluorocarbons requires energy absorption of 346.94 and 484.88 kJ/mol, respectively, the depolymerization of polytetrafluoroethylene to produce 1 mol of tetrafluoroethylene requires only 171.38 kJ of energy. So during high-temperature cracking, polytetrafluoroethylene mainly depolymerizes into tetrafluoroethylene. The weight loss rates (%) of polytetrafluoroethylene at 260, 370, and 420 ℃ are 1 × 10-4, 4 × 10-3, and 9 × 10-2 per hour, respectively. It can be seen that polytetrafluoroethylene can be used for a long time at 260 ℃. Due to the production of highly toxic byproducts such as fluorophosgene and perfluoroisobutylene during high-temperature cracking, special attention should be paid to safety protection and preventing polytetrafluoroethylene from coming into contact with open flames.

Its mechanical properties have an extremely low coefficient of friction, only 1/5 of that of polyethylene, which is an important feature of perfluorocarbon surfaces. Due to the extremely low intermolecular forces between fluorine carbon chains, polytetrafluoroethylene has non adhesiveness.

It does not melt at a temperature of 250 ℃ and does not become brittle at ultra-low temperatures of -260 ℃. Polytetrafluoroethylene is exceptionally smooth, even ice cannot compare to it; It has particularly good insulation performance, with a thin film thick enough to withstand a high voltage of 1500V.

Polytetrafluoroethylene maintains excellent mechanical properties over a wide temperature range of -196 to 260 ℃, and one of the characteristics of perfluorocarbon polymers is that they remain brittle at low temperatures.

Chemical corrosion resistance and weather resistance: except for molten alkali metals, polytetrafluoroethylene is almost not corroded by any chemical reagents. For example, when boiled in nitric acid, hydrochloric acid, or even aqua regia, their weight and properties remain unchanged, and they are almost insoluble in all solvents, only slightly soluble in alkanes above 300 ℃ (about 0.1g/100g). Polytetrafluoroethylene is non hygroscopic, non flammable, and extremely stable to oxygen and ultraviolet radiation, thus possessing excellent weather resistance.

Polytetrafluoroethylene has low dielectric constant and dielectric loss over a wide frequency range, and high breakdown voltage, volume resistivity, and arc resistance.

The radiation resistance of polytetrafluoroethylene is poor (104 rad), and it degrades after being exposed to high-energy radiation, resulting in a significant decrease in the electrical and mechanical properties of the polymer.

Polytetrafluoroethylene is produced by free radical polymerization of tetrafluoroethylene. The polymerization reaction in industry is carried out by stirring in the presence of a large amount of water to disperse the reaction heat and facilitate temperature control. Aggregation is generally carried out at 40-80 ℃ and 3-26 kgf/cm2 pressure. Inorganic persulfates and organic peroxides can be used as initiators, or redox initiation systems can be employed. Each mole of tetrafluoroethylene releases 171.38 kJ of heat during polymerization. Dispersion polymerization requires the addition of perfluorinated surfactants, such as perfluorooctanoic acid or its salts.

The application of polytetrafluoroethylene can be formed by compression or extrusion processing; It can also be made into aqueous dispersions for coating, impregnation, or fiber production. Polytetrafluoroethylene is widely used in industries such as atomic energy, aerospace, electronics, electrical engineering, chemical engineering, machinery, instruments, meters, construction, textiles, and food as high and low temperature resistant, corrosion-resistant materials, insulation materials, and anti stick coatings.