Graphite, FEP, and PTFE are three commonly used components which are categorized separately in this module.



  • One of the two crystalline forms of the element carbon (The other is diamond); man-made carbon, graphite, and diamonds also exist
  • One of the most stable and chemically-resistant materials in the world
  • Does not melt, but sublimes; changes from the solid to gas state, bypassing the liquid state, at temperatures over 5400°F (2980°C), or, in the presence of oxygen oxidation, above 850°F (450°C)
  • Excellent conductor of heat and electricity
  • Readily available in various forms; moderately priced to very expensive


Polytetrafluoroethylene (PTFE)

  • Man-made thermoplastic introduced in the late 1940s or early 1950s
  • Extremely good chemical inertness and resistance to a wide range of fluids; only a few, very rare fluids will attack it
  • Withstands a wide temperature range, from -450°F (-268°C) to 500°F (260°C)
  • A very low static coefficient of friction; very slippery
  • Poor heat conductor; good heat insulator
  • High coefficient of thermal expansion; swells significantly under heat
  • Flows (creeps) under relatively low loads, even at room temperature (usually stated as “cold flow”)
  • Can be readily blended with other materials to improve its features and performance characteristics
  • Readily available at moderately high prices



Fluorinated Ethylene Propylene

  • Similar chemical resistance to that of PTFE
  • In terms of Garlock® products, predominately used as the liner material in GUARDIAN® Expansion Joints
  • Temperature limit: 450°F (232°C)