Thanks to the regular arrangement of the polymer chains, the surface of the high-quality FEP insulation is as smooth and uniform as a mirror, showing a soft luster similar to that of acrylic. Inferior imitations, such as PVC or recycled plastics, tend to have a dull gloss due to their rough production process and high content of impurities in the raw materials.
The insulation layer made from pure FEP raw materials is mostly translucent, similar to pale amber, or has a uniform milky white color. If the color of the wire is yellow, it may be due to improper temperature control during the production process, which causes the material to deteriorate; Grey or speckled may be adulterated with recyclate. However, some special processes may produce FEP insulation with slight color (e.g., adding a small amount of masterbatch for shading), but the overall color should be uniform and consistent, with no light and dark layering.
Or with a gentle pinch of the insulation with your fingers, true FEP delivers a "soft and firm" feel – neither soft nor stiff like hard plastic, but elastic like a baby bottle straw that quickly returns to its original shape when pressed. Fake materials may present two extremes: one is the hard "plastic" feeling, which makes a crisp "click" sound when bent; The other is too soft and sticky, like a melted candle, which is usually a sign of an excessive amount of plasticizer.
If it still can't be identified, a combustion test is performed. In the molecular structure of fluoropolymers, fluorine and carbon form extremely strong chemical bonds (bond energy of about 485 kJ/mol), making FEP naturally flame retardant. So if it is a real FPE insulated wire, when the flame touches the insulation, there will only be a slight sign of melting, and it will be extinguished instantly after leaving the fire source, and during the combustion process, there is almost no obvious flame, and only a small amount of white smoke is produced at the contact point. This is also the reason why FPE insulated wire is called high temperature heating cable, in addition, resistant to oil, non aging, etc. are its advantages.
