Teflon - PTFE (Polytetrafluoroethylene) | Physical and Chemical Properties of Polytetrafluoroethylene

PTFE (Polytetrafluoroethylene):
This is actually a short form of Polytetrafluoroethylene. In America, where the material was developed, it is used as plastic, and also spun into a fibre under the name Teflon. Actually it was manufactured by du Pont in 1941. In 1954 the fibre was introduced by du Pont. 

Manufacturing of PTFE (Polytetrafluoroethylene):
The basic raw material is fluorspar, CaF2 from which anhydrous hydrofluoric acid is prepared and chloroform. These two are reacted together to give difluoromonochloromethane, a gas which boils -41 degree C.

CHCl3 + 2HF → CHCl2 + 2HCl

This gas is pyrolysed at 600-800 degree Cto give tetrafluoroethylene:

2CHClF2 → C2F4 + 2HCl

The tetrafluoroethylene is washed and fractionated to remove hydrochloric acid and various fluorocarbons which are formed during the pyrolysis. The purified tetrafluoroethylene is then polymerized in stainless-steel autoclaves in the presence of an aqueous solution of ammonium persulphate or other peroxy catalyst; the reaction is rapid and exothermic and conditions have to be carefully controlled. The polt tetrafluoroethylene produced is granular (rough) white solid which is washed and dried hot.

Physical Properties of Polytetrafluoroethylene:
  1. Tenacity is 1.5 gm/d.
  2. Elongation is about 13%
  3. Water absorption is zero, so that wet characteristics are same as dry.
  4. Loop and knot tensile strength are about 75% of the straight strength.
  5. Cross section is round.
  6. Frictional properties are low.
  7. No dyeability.
  8. Heat resistance is best of all fibres (at temp. 310 degree C the fibre still has measurable strength of 0.1 g/d and gels at 327 degree C.
  9. Decomposition temp. is 405 degree C
  10. Fibre can be used at temp. up to about 290 degree C
Chemical Properties of Teflon:
  1. Chemical stability is quite unique.
  2. The fibre can be boiled in aquaregia(Rajomlo) or mineral acids or concentrated caustic soda solution without decomposition.
  3. It is attacked and decomposed by fluorine gas at high temp. and pressure and by chlorine trifluoride.
Uses / Application of PTFE:
  1. Braided packing, which is used for chemical pump shafts.
  2. Filtration fabric (for the liquid filtration of corrosive mixtures).
  3. Laundry for press pad-covers and roll-covers.
  4. Electrical taps.
  5. Wire wraps for corrosive service.
  6. Corrosion resistant cordages.
  7. Anti-static bandages. 
Author of This Article:

Arman Ahmed
Department of Textile Engineering
Ahsanullah University of Science & Technology (AUST)
Email: a120106013@gmail.com

Cell: 01673637772 


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