There are various types of fluoropolymers used for Lining:
Flouorpolymer or Flouroplastic is defined as a polymer consisting of carbon (C) and Fluorine (F). They are also referred as Perflouropolymers to distinguish from partially fluorinated polymers, flouoroelastomers, and other polymers that contain fluorine in their chemical structure. An Example of linear Flouropolymer is tetrafluoroethylene (PTFE).
The Basic Properties of fluoropolymers arise from the atomic structure of fluorine, carbon and their covalent bonding in specific chemical structures. These properties are weakened as the chemical structure become less perfluorinated as in polyvinylidene fluoride. PTFE Backbone is formed by carbon-carbon bonds and carbon-fluorine bonds.
The Size of the fluorine atom allows the formation of uniform and continuous sheath around the carbon-carbon bonds and protects them from attack, thus imparting chemical resistance and stability to molecule. The Fluorine sheath is also responsible for low surface energy and low coefficient of friction. Another attribute of the uniform fluorine sheath is the electrical inertness of the PTFE Molecule.
Fluoropolymers are used in the chemical processing industry principally for outstanding resistance to almost all chemicals their ability to withstand high temperatures also plays an important part in their functional role. The low mechanical Properties and high permeation rates of fluoropolymers at high temperature limit their use of linings to about 175 Degree Celsius, although they remain chemical inert up to 260 Degree Celsius.
Selection of polymers is an integral part of the overall material selection process. This implies that all the available material such as metals, ceramics and plastics are considered candidates for an application. The end user then considers these materials against established criteria such as required life, mean time between inspection, ease of fabrication, frequency of inspection, extent of maintenance and capital cost.
More often than not it is the initial capital cost rather than life cycle cost of the equipment that affects the decision made during the material selection step. However the most important piece of data in the medium under consideration over the life of the equipment.
PTFE is marketed under the trade name of Teflon by DuPont It is a fully fluorinated thermoplastic having the following formula:
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