The relative molecular mass of Teflon PFA products is relatively large. Generally, the crystallinity is 90-95%, and the melting temperature is 327-342 °C. The CF2 units in the Teflon PFA molecule are arranged in a zigzag shape. Since the radius of the fluorine atom is slightly larger than that of the hydrogen, the adjacent CF2 units cannot be completely oriented in trans, but form a helical twisted chain, and the fluorine atom almost covers the entire surface of polymer chains. This molecular structure explains the various properties of Teflon PFA products. When the temperature is lower than 19°C, a 13/6 helix is formed; at 19°C, a phase transition occurs, and the molecules are slightly unwound, forming a 15/7 helix.
Main applications of Teflon PFA products:
Teflon PFA products have high melting point and high melt viscosity, and are sensitive to shearing in an amorphous state, which is prone to melt fracture. Therefore, conventional thermoplastic molding processes such as melt extrusion and injection molding cannot be used. Sintering is carried out in a method similar to powder metallurgy.
The manufacture of filled PTFE is the same as the molding of PTFE. It can be processed by pre-forming, free sintering, or by plunger extrusion. The above processing technology is generally suitable for products with a certain wall thickness, not suitable for the processing of PTFE films. In recent years, a lot of research has been carried out in China. The more mature processing technologies are: calendering for disperse PTFE resin; metal turning processing using the characteristics of low hardness and good toughness of PTFE sintered products; in addition, there is a conventional extrusion method and In the extrusion processing of the calendering method, the resin is directly processed with raw materials without being melted and plasticized.
Processing of Teflon PFA products In addition to the primary processing technology introduced above, there are also some newly developed secondary processing technologies worthy of attention, such as PTFE vacuum forming technology, hot press forming and hot blow molding technology, isobaric forming processing technology, etc. PTFE is the preferred material for corrosion-resistant lining of corrosion-resistant pipes, fittings, bellows, pump bodies, valves, kettles, tanks, towers and various standard equipment; as a sealing material, it is widely used in machinery, petrochemical, transportation, textile and construction industries. Wide range; Teflon PFA products can also be used as valves, bearings, piston rings, guide rails and other parts requiring corrosion resistance and low friction;
According to Teflon PFA products, the film has selective air permeability after treatment, and can be used as a separation material, selectively permeating gas or liquid, especially filtering corrosive liquids; due to the excellent biocompatibility of Teflon PFA, many people in recent years will It has been intensively studied as a biological material.