Why is Teflon (PTFE) white while fluorinated ethylene propylene (FEP), a Teflon Co-Polymer, is Transparent?

Polytetrafluoroethylene or PTFE tubes are more popularly known as non-stick coatings are two-coat systems which include the primer or topcoat systems. These products have the properties which include good abrasion resistance and chemical resistance. Operating temperature of any fluoroplastic (260°C/500°F), which generates an extremely low coefficient of friction. 

What is Teflon FEP?

FEP or fluorinated ethylene propylene copolymer non-stick coatings that can flow and melt easily when baked provide nonporous films. 

Here are some of the differences between fluoropolymers, PTFE and FEP.

PTFE

• Polytetrafluoroethylene, or PTFE, was one of the first of the synthetic fluoropolymers to be produced. It is certainly one of the most widely used Fluoropolymer.
•  The color of the natural PTFE tubing is opaque to practically transparent. It also has the property of having the lowest surface friction of all materials. This ensures that it has high flow rates and very low chances of congestion
• The PTFE has a superior non-stick surface and is perfect for cookware and bakeware. It makes both cooking and cleaning very easy.
• Non-stick coatings are used widely in guns and ammunition as they reduce the amount of wear on the barrel of the gun when fired.
• PTFE coatings are also known as hydrophobic. This means that liquids run straight off material or surface that has been coated with PTFE. This is largely due to its high electronegativity.

FEP

• The Fluorinated ethylene propylene, or FEP as it is better known as is slightly different to PTFE but it has some non-stick properties of Teflon.
• The properties of FEP differs from PTFE is that it is softer than PTFE and melts at a far lower temperature. This is the very reason that the use of FEP for cookware and bakeware.
• Another great benefit of FEP is that it is completely transparent. So whatever you pour in it and whichever surface it covers the color won’t change and it will remain the same.
•  FEP is also resistant to sunlight, so it is terrific for all weather applications. This is particularly useful for outdoor wiring and equipment that undergoes weathering. FEP is usually used in applications where clarity is the number 1 norm like for example soil analysis and/or sight glasses and so on.

PTFE and FEP are similar in their chief material properties. The main difference between PTFE and FEP lies in the maximum operating temperature and the colour. PTFE looks milky/white and FEP is clear transparent.

Fluorocarbons of different types are colorless so they make transparent liquids, as has been explained. They can make transparent solids also because of the sintering processes in manufacture helps trap bits of polymer that possess different indexes of refraction against each other. The light scatters at the interface like when in any homogenous liquid solidifies. It is the light scattering which makes the solids white.

There are transparent Teflon tubes which can prove that Teflon without the defects can make it scatter light and turn white.