What is the difference between soluble polytetrafluoroethylene (PFA) and polytetrafluoroethylene (PTFE)
1. Differences in chemical structure:
PFA adds a perfluoroalkoxy group, which is equivalent to replacing one fluorine atom in PTFE with a perfluoroalkoxy group. A carbon is directly attached to an oxygen, and then the oxygen is attached to a group like perfluoromethyl or perfluoroethyl. Compared to PTFE, the reduced melt viscosity facilitates processing. The rest of the properties are not too different from PTFE.
2. Differences in application:
PFA – has the same excellent properties as polytetrafluoroethylene, and has good thermoplasticity, which can be processed by the processing method of ordinary thermoplastic resin. It is obtained by copolymerization of tetrafluoroethylene and perfluoropropyl vinyl ether in a certain proportion in an aqueous medium containing perfluorocarboxylate dispersant and persulfate initiator. It is a white translucent particle.
Not only has the same use temperature as PTFE, but also has better mechanical strength (about 2 to 3 times) at 250 ° C, and has excellent stress crack resistance. It has a wide processing range and good molding performance, and is suitable for compression molding, extrusion molding, injection molding, transfer molding and other molding processes. It can be used to make wire and cable insulation sheaths, high-frequency and ultra-high-frequency insulation parts, corrosion-resistant linings for chemical pipelines, valves and pumps; special parts for machinery industry, various anti-corrosion materials for light textile industry, and PTFE anti-corrosion linings Wait for welding rod.
It is prepared by extruding fusible polytetrafluoroethylene pellets, and the appearance is translucent milky white, the surface is smooth, and the section is dense and uniform. It is specially used for the welding of PTFE plates and pipes, so that PTFE products with simple shapes can be welded into products with complex shapes and larger sizes.
The aqueous PTFE emulsion price is obtained by adding an emulsifier to the copolymer obtained by the copolymerization of tetrafluoroethylene and perfluoropropyl vinyl ether, and concentrating at a certain temperature. The solid content is 30%±1%. Appearance is milky white or light yellow translucent. It has various excellent properties of fusible polytetrafluoroethylene resin. It can be used for a long time at 260 ℃, and it has been developed into an advanced coating with its excellent anti-sticking, anti-corrosion and easy processing properties, which can be sprayed and dipped.
PTFE–polytetrafluoroethylene is obtained by the polymerization of tetrafluoroethylene monomer by suspension method or dispersion method. Molecular weight=5.2×105-4.5×107. White powder, 400 mesh accounts for 75%, tasteless, non-beautiful, non-toxic. The relative density is 2.1-2.3, the refractive index is 1.37, the glass transition temperature is 327°C, and the thermal decomposition temperature is 415°C. When the temperature is above 400℃, there will be slight weight loss and decompose toxic gas.
Use temperature -250～260 ℃, use up to 10000h at 210 ℃. Excellent chemical resistance, resistance to any strong acid (including aqua regia), strong alkali, grease, insoluble in any solvent, extremely low friction coefficient, good wear resistance, and self-lubricating. Excellent aging resistance. Excellent electrical properties, good arc resistance. It is not sticky, almost all sticky substances cannot adhere to its surface, and it is completely non-flammable. It is known as the “Plastic King”. Tensile strength (MPa)>23 Elongation (%)>250.
3. Differences in processing methods:
The main difference in processing methods is that PFA can be hot melt injection molded, while PTFE cannot be hot melt injection molded.
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