Heat Resistance

Fluoropolymers, a class of synthetic materials renowned for their exceptional heat resistance properties, have revolutionized various industrial applications. These polymers, consisting of carbon and fluorine atoms, possess unique characteristics that make them suitable for high-temperature environments.

The Role of Fluorine Atoms

The heat resistance of fluoropolymers can be attributed to the presence of strong carbon-fluorine (C-F) bonds in their molecular structure. The C-F bond imparts remarkable stability by providing a highly inert barrier against oxidative and thermal degradation.

Factors Influencing Heat Resistance

There are several factors that can influence the heat resistance of fluoropolymers:

• Polymer Structure
  The molecular structure of the fluoropolymer plays a significant role in determining its heat resistance. For example, polymers with longer polymer chains tend to have higher heat resistance due to increased intermolecular forces. Furthermore, polytetrafluoroethylene (PTFE), for example, has a twisted helical conformation consisting of 13 CF₂ groups per 180° rotation. The helix forms an almost perfect cylinder, including an outer sheath of fluorine atoms surrounding a carbon-based core. This morphology favors the packing of PTFE molecules like parallel rods.

The skeleton structure of PTFE [1]

• Chemical Composition
  The type and amount of fluorinated monomers used in the polymerization process can affect the heat resistance of fluoropolymers. The presence of highly fluorinated monomers, such as perfluorinated or partially fluorinated monomers, can enhance the heat resistance of the polymer.
• Purity
  The presence of impurities or additives can lower the heat resistance of fluoropolymers. Impurities can act as nucleation sites for thermal degradation, leading to a reduction in heat resistance.
• Crystallinity
  The degree of crystallinity in fluoropolymers can impact their heat resistance. Higher levels of crystallinity generally result in higher melting points and improved heat resistance.
• Crosslinking
  Crosslinking refers to the formation of covalent bonds between polymer chains, which can improve the heat resistance of fluoropolymers. Crosslinked fluoropolymers have higher thermal stability and can resist thermal degradation to a greater extent.
• Fillers
  The addition of inorganic fillers, such as glass fibers or mineral fillers, can improve the heat resistance of fluoropolymers. These fillers distribute heat and reinforce the polymer matrix, enhancing its ability to withstand high temperatures.
• Processing Conditions
  The processing conditions during the manufacturing of fluoropolymers can affect their heat resistance. Parameters such as temperature, pressure, and cooling rate can impact the molecular structure and overall heat resistance of the polymer.

Comparison of Heat Resistance of Common Fluoropolymers

Several common fluoropolymers used in industrial applications have varying heat resistance properties.

Fluoropolymer	Heat Resistance	Maximum Temperature
Polytetrafluoroethylene (PTFE)	Excellent	260°C continuously
Ethylene tetrafluoroethylene (ETFE)	Good	150°C continuously
Perfluoroalkoxy (PFA)	Excellent	260°C continuously
Polyvinylidene fluoride (PVDF)	Good	150°C continuously
Fluorinated ethylene propylene (FEP)	Excellent	260°C continuously
Perfluoroelastomers (FFKM)	Excellent	330°C

Reference

1. Jiri George Drobny. Technology of Fluoropolymers, Second Edition.