PTFE

The first coating material applied by Caw was PTFE, which stands for poly-tetra-fluoro-ethylene. In South Africa this is often referred to by the Du Pont trade name of TEFLON 8. In the early stages it was mainly applied for use in the textile industry. Today it is applied to a wide variety of articles in the manufacturing industry where its non-stick, heat resistant properties are of use. For the best results with regard to these two properties, the article has to be baked at 400 C. Although the PTFE is present as a continuous film it is not often useful as a corrosion resistant coating as it is micro-porous. Other systems where the PTFE is present as a pigment in the resin, can be applied at a lower temperature. These may have better abrasion and corrosion resistance than the high-bake type.

Special Coating

Some plastics not available in paint systems can be applied using powder coating techniques. E.g. Gun Coat, Nylons, polyethylene and PVDF These have good corrosion resistance and can be more than half a millimeter thick provided the substance has sufficient heat capacity. PCDF coatings have exceptional abrasion resistance.

 

Outstanding Properties

 

Non-stick

 

Very few solid substances will permanently adhere to a "Teflon" finish. And while tacky materials may show some adhesion, almost all substances release easily.

 

Low coefficient of friction

 

The coefficient of friction of "Teflon"is generally in the range of 0.05 to 0.20, depending on the load, sliding speed and particular "Teflon" finish used.

 

Non-wetting

 

Since "Teflon" surfaces are both oleophobic and hydrophobic, they are not readily wet. Clean-up is easier, more thorough and in many cases self-cleaning.

 

Heat-resistance

 

There is no decomposition of PTFE below 205 C (400 R;

insignificant decomposition between 205 C and 290 C (400 F and 550 F) which requires no special precautions. Between 290 C and 315 C (550 F and 600 F) intermittent service is possible with adequate ventilation.

Unique electrical properties

 

Over a wide range of frequencies, "Teflon" has high dielectric strength, low dissipation factor, and very high surface resistivity. By special techniques, it can even be made conductive enough to be used as an anti-static coating.

 

 

Cryogenic stability

 

Many "Teflon" finishes will withstand severe temperature extremes without loss of physical properties. "Teflon" may be considered for use at temperatures as low as 270 C (-450 F).

 

 

 

 

 
 

Chemical resistance

 

"Teflon" is normally unaffected by chemical environments. However, certain "Teflon" finishes are permeable or have a lower resistance to attack. The only chemicals known to affect all "Teflon" finishes are the alkali metals and highly reactive fluorinating agents.