FLUOROCARBON POLYMERS FLUOROPLASTICS

Fluorocarbon Polymers (Fluoroplastics) These represent a broad family of polymers based on hydrocarbons containing fluorine, and sometimes also chlorine. The most distinguished polymer in this group is polytetrafluoroeth-ylene (PTFE), known more by its commercial name of Teflon (1943). In this case, all four hydrogen atoms in ethylene are replaced by fluorine in a linear chain. The specific mass is 2.15. 

The presence of fluorine contributes extraordinary properties such as superb thermal and chemical stability and low friction coefficient. Replacement of fewer hydrogens or a combination of chlorine and fluorine leads to polymers 

The monomer tetra-fluoroethylene is obtained by reacting HF with chloroform through cracking, whereas the source for HF is fluorspar CaF2, treated with sulfuric acid. 

It can advantageously be injected, extruded, compressed or thermally formed. It also surpasses Teflon in rigidity and resistance to creep, but relatively fails in thermal and chemical endurance, being useful up to 200 C. 

There are more polymers in this family, including copolymers (with ethylene in alternation). Upon replacing atoms of fluorine with chlorine or hydrogen, the chemical inertness and the range of useful temperatures diminish, while workability, strength and rigidity all improve. The price of these polymers is quite high, so they are used only when their imique performance is required. 

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A major development in fluoroplastics is the recent small scale production of Teflon AF, a noncrystalline (amorphous) fluorocarbon polymer with a high glass transition temperature (240 °C) This optically transparent TFE copolymer is soluble m certain fluorocarbons and has the same chemical and oxidative stability as crystalline TFE homopolymers [5]... 

The fluoroplastic materials are divided into two groups fully fluorinated fluorocarbon polymers such as PTFE, FEP, and PPA called perfluoropoly-mers, and the partially fluorinated pol)nners such as ETFE, PVDF, and ECTFE that are called fluoropol)nners. The pol)uneiic characteristics within each group are similar, but there are important differences between the groups as will be seen later. 

Perfluoroalkoxy resin (PFA) n. A class of melt-processable fluoroplastics in which perfluoroalkyl side chains are cormected to the fluorocarbon backbone of the polymer through flexible oxygen linkages. 

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