POLYTETRAFLUOROETHENE (PTFE) POLYMER

POLYTETRAFLUOROETHENE, PTFE, is a unique most useful product in the plastic industry. It's chemically inert and thermally stable over a wide temperature range is (- 196 to 260⁰ C) is an excellent insulator and has a low co-efficient of friction. It's a white solid that's manufactured by the polymerization of tetrafluoroethene.

nCF₂ = CF₂ → ( CF₂CF₂)n

PPFE is a most expensive polymer, because of the cost synthesizing and purifying the monomer by a multistage process :

CH₄ (ɡ) + 3 CI₂ (ɡ) →CHCl₃ (ɡ) + 3 HCl (ɡ)

CHCl₃(ɡ) + 2HF(ɡ) → CHClF₂ +2 HCl(ɡ)

2CHClF₂(ɡ) → heat CF₂ = CF₂ (ɡ)+ 2 HCl(ɡ)

The Hydrogen fluoride is generating by the action of sulfuric acid on fluorite :

CaF₂(s) + H₂SO₄ (l) → CaSO₄(s) + 2HF (l)

As thie process employs HCl and HF, the reactors have to be line with platinum. Many byproducts are producing , which leads to complex purification of the final product.

The tetrafluoroethene is polymerized in two ways, the solution polymerization with vigorous agitation produces a resin known as granular PTFE : emulsion polymerization with dispersing agents and gentle agitation produces small particle known as dispersed PTFE. The molten polymer doesn't flow, so the usual methods of processing can't be used. But instead processes similar used to metals are applied. For example, the dispersed from can be cold extruded which is method used for processing lead.

                                     The remarkably properties of PTFE arises from the protective that the F atoms form arrounding the carbon polymer backbone. The fluorine atoms are just the right size to form a smooth sheath. This smooth sheath is reducing the disruption of intermolecular forces at the surface, leading to a low co-efficient of friction and the familiar nonstick properties. Especially this polymer is used in a wide range of applications. It's low electrical conductivity leads to it's use in electrical tapes, wires, and coaxial cable. It's mechanical properties make it ideal material for seals, piston, rings, and bearings. It's used as a packaging material, in hose lines and thread- sealant tape. The most familiar applications are as the nonstick coating or cookware, and as the porous fabric core -Tex.