PTFE has exceptional thermal stability and may be used continuously over the working temperature range.

The thermal behavior of PTFE is complex and the following points should be noted:

• Phase transitions accompanied by significant volume changes at 19ºC. and 30ºC.
• Large and temperature dependent coefficients of thermal expansion
• No easily discernible melting point - the notional melting point is about 328ºC.
• The "liquid" phase has a very high melt viscosity which means that PTFE remains in a rigid gel-like state when "molten"
• Thermal decomposition starts at about 400ºC.
• The degree of crystallinity in the solid is determined by the rate of cooling from the "liquid" phase

NB: The fluoropolymers PFA and FEP are thermoplastics and have normal melting behaviour