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PTFE Fluoro-Polymer : Solid Lubricant in OIls and Greases


PTFE fluoropolymer or also known as polytetrafluoroethylene is one of the most versatile synthetic plastic materials with numerous unique properties : 1. Excellent chemical resistance, 2. Inert to virtually all chemicals and solvents, 3. Very low coefficient of friction, 4. Extremely abrasion resistant, 5. Broad operating temperature, 6. High dielectric strength, etc.

PTFE is formed by polymerisation of tetrafluoroethylene. It is a saturated aliphatic fluorocarbon. It was invented  accidentally by Roy J. Plunkett in 1938; while attempting to make a new CFC refrigerant,  a
white waxy solid  with exceptional slipperiness  was discovered. This substance was later registered  the  trademark as Teflon by DuPont in 1944.


Mechanical Properties of  Teflon PTFE (High molecular weight), Reference: DuPont

This special plastic material has been utilised in diverse applications since then :  from  sophisticated aerospace technologies, harshest chemical manufacturing facilities,   to as common as the coating of  non-stick cookware in households. Besides, the distinct feature of PTFE, being virtually the most slippery solid in existence favours the use in lubrication between two rubbing surfaces, especially under severe operating conditions where other mineral and synthetic based oils fail. In this context, PTFE ( some with low molecular weight grades ) are incorporated into  lubricant products as solid lubricant.

Why PTFE as solid lubricant?
Ideally, a fluid film lubricant is adequate to eliminate the friction/contact by separating two interacting surfaces under hydrodynamic lubrication regime. Oiliness improvers are used to enhance  lubricity  and  film strength of  liquid lubricants. They are organic compounds that having long hydrocarbon chains in molecules, terminated with strong acidic groups. These high polarity groups are capable of adsorbing onto metal surfaces to form stronger lubricating film compared to that of mineral based lubricants. Having said that, oiliness improvers are found to be effective for lubrication in  low to medium load operations.

Under severe load , high temperature conditions,   the micro asperities of interacting surfaces penetrate the lubricating fluid film   and cause metallic contacts and highly frictional boundary lubrication condition. Undesirable  and excessive  heat is thus generated,  and efficiency of  power transmission system  is further reduced.  

By introducing solid lubricants into fluid lubricant systems, the performance  is  extended  for  higher operational load conditions and temperature ranges. Molybdenum disulphide and graphite are the two substances that being extensively used to formulate heavy duty lubricants and greases. These crystalline lattice structured materials exhibit low Van der Waals  forces between the  lattice layers thus  resulting  low shear forces; with slight tangential loading,  tend to slip out of place from each other  -- in short,   overall surface friction is reduced.  The detailed lubrication mechanisms would be shared in coming post.                  

As for PTFE long chain fluoropolymer, the micro particles of this solid lubricant trap in the pits and crevices of the lubricated surface, forming a thin layer of lubricating film that providing low friction resistance between interacting surfaces. This is especially useful for boundary lubrication whereby two surfaces are mostly in contact with each other. The pressure created during two peaks of the rubbing surface forces the fluid film lubricant being squeezed out.  PTFE polymers in micro sphere form lubricate the contact surface like miniature ball bearing rolling in between thus providing a very smooth lubricating film.

Solid particles of  fluoropolymer  dispersed in fluid film lubricant  aid  to  reduce  friction between  two interacting surfaces


Illustration:  Stribeck Curve  --An effective solid lubricant system  reduces coefficient of  friction  ( green curve ), and yields higher  efficiency  of  energy conversion.


PTFE solid lubricant  enhances  load carrying and anti wear  properties of  a particular  formulated product,  it offers protection that exceeding many normal mineral oil-based and synthetic fluid lubricants, significantly  diminishes  galling, seizing and fretting of metal surfaces.






Interflon FIN Grease MP  2/3, Specialty grease fortified with Teflon polymer & additives

 Interflon Fin Grease MP 2/3 Multi Purpose Grease --  For a multitude of applications.  Highly acclaimed, multipurpose heavy duty grease with Teflon. Provides for extremely long lasting protection against wear and corrosion. Engineered for a multitude of general machine lubrication applications over a wide range environmental conditions. For industrial applications when several different high performance lubricants are
needed.


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