Читать книгу Concise Handbook of Fluorocarbon Gases - Sina Ebnesajjad - Страница 27

In this book the term fluoropolymer describes fluorinated polymers and copolymers of a few olefinic monomers that are consumed in significant commercial scale. These monomers include tetrafluoroethylene (CF₂=CF₂), vinylidene fluoride (CF₂=CH₂) and chlorotrifluoroethylene (CFCl=CF₂) and vinyl fluoride (CHF=CH₂). The polymers of the last two are produced at significantly lower volumes than the first two monomers but have been included because of the importance of their applications. Generally, an increase in fluorine content of polymer enhances the desirable properties for which fluorinated polymers are known (Table 2.7).

Fluoroelastomers consist of a number of high performance synthetic rubbers that are partially or fully fluorinated. Fluoroelastomers are made by copolymerizing various combinations of vinylidene fluoride (CH₂=CF₂), hexafluoropropylene (CF₂=CFCF₃), chlorotrifluoroethylene (CF₂=CFCl), and tetrafluoroethylene (CF₂=CF₂). These fluorinated elastomers have outstanding resistance to oxygen, ozone, and heat and to swelling by oils, chlorinated solvent, and fuels.

Table 2.7 Effect of increasing fluorine content in polymers.

Property	Impact
Chemical resistance	Up
Melting point	Up
Coefficient of friction	Down
Thermal stability	Up
Dielectric constant	Down
Dissipation factor	Down
Volume and surface resistivity	Up
Mechanical properties	Down
Flame resistance	Up
Resistance to weathering	Up