|Polytetrafluoroethylene (PTFE)||Tetrafluoroethylene (TFE)|
- Polymerization of TFE——Granular Resins
When little or no dispersant is used and the reaction mixture is stirred vigorously, a precipitated polymer is produced, commonly referred to as granular resin.
- Polymerization of TFE——Fine Powder Resins
Using appropriate type and sufficient amount of dispersant and maintaining gentle stirring, a product composed of small negatively charged oval colloidal particles (less than 0.5 μm in length) can be obtained.
|Polychlorotrifluoroethylene (PCTFE)||Chlorotrifluoroethylene (CTFE)|
- The commercial process used to produce PCTFE is basically a polymerization reaction initiated by free radicals at moderate temperature and pressure in an aqueous system at low temperature and medium pressure.
|Fluorinated ethylene propylene (FEP)||TFEthexafluoropropene (HFP)|
- Aqueous and non-aqueous dispersion polymerization is the most convenient commercial route. The conditions of this type of process are similar to the dispersion and homopolymerization of TFE. HFP units are added to the growing chain at random intervals, so the FEP obtained is a random copolymer. The optimal composition of the copolymer is that the mechanical properties are kept within the usable range and the melt viscosity is low enough to facilitate melt processing.
|Polyvinylfluoride (PVF)||Vinyl fluoride (VF)|
- Vinyl fluoride is the most common commercial fluoropolymer polymerized by a free radical process, but polymerization is more difficult than TFE or VDF and requires higher pressure.
|Polyvinyldifluoride (PVDF)||Vinylidene fluoride (VDF)|
- Emulsion polymerizationrequires the use of free radical initiators, fluorinated surfactants and chain transfer agents. The polymer separated from the reaction vessel consists of agglomerated spherical particles with a diameter of 0.2 to 0.5 μm. It is then dried according to the intended use and provided as a free-flowing powder or granules.
- Aqueous suspension polymerization requires commonly used additives such as free radical initiators, colloidal dispersants and chain transfer agents to control molecular weight. After the process is complete, the suspension contains spherical particles with a diameter of approximately 100 μm. Suspended polymers can be used in extrusion or injection molding as a free-flowing powder or pellet form.
|Ethylene (E) copolymer of CTFE (ECTFE)||CTFE|
- The copolymerization of ethylene and chlorotrifluoroethylene is carried out as a free radical suspension process in an aqueous medium at low temperature. Lowering the temperature will reduce the number of ethylene blocks in the polymer backbone that are susceptible to thermal degradation.
|Perfluoroalkoxy- (PFA)||TFE + perfluoroalkylvinylether (PVE)|
- Perfluoroalkoxy resins are prepared by copolymerization TFE and perfluoroalkyl monomers in aqueous or non-aqueous media. The conditions of the aqueous copolymerization reaction are similar to those of polytetrafluoroethylene emulsion polymerization, using inorganic peroxygen compounds (such as ammonium persulfate) as initiators and adding perfluoroemulsifiers (such as ammonium perfluorooctanoate).
|E copolymer of TFE (ETFE)||E +TFE|
- Commercial products based on copolymers of ethylene and TFE are prepared by free radical-initiated addition copolymerization. Add a small amount (1 to 10 mol%) of modified comonomer to eliminate the rapid embrittlement of the product at high temperature. Examples of modified comonomers are perfluorobutylethylene, hexafluoropropylene, perfluorovinyl ether and hexafluoroisobutylene.