PCTFE / Kel-F® / NEOFLON™ Compression Molding

PCTFE is often still referred to as Kel-F®, even though 3M quit manufacturing Kel-F® PCTFE in 1995 and sold the rights to Daikin, who now produces the resin under the NEOFLON™ PCTFE brand name.

PCTFE (polychlorotrifluoroethylene) is formed by the polymerization of the homopolymer of chlorotrifluoroethylene.

PCTFE is a crystalline polymer whose degree and type of crystallinity can be controlled by its thermal history, especially by how fast it is cooled.  This makes PCTFE a versatile material whose properties can be modified over a wide range depending on manufacturing conditions.  When molded with high crystallinity, PCTFE is dense and has high mechanical strength and low elongation.  However, amorphous molded PCTFE has a lower density, is more elastic and optically clear.

Because PCTFE is not well suited for injection molding certain kinds of parts, compression molding followed by machining is used instead.

PCTFE objects made by compression molding are stronger than those made by injection molding or extrusion.  Because PCTFE isn’t very stable in its molten state, injection molding or extrusion of PCTFE, which require elevated temperatures, can lead to molecular degradation (loss of molecular weight) and reduced properties as revealed by zero-strength-time (ZST) tests (ASTM D1430).  However, expertly performed compression molding doesn’t cause the material to overheat and doesn’t induce a preferential orientation to the material.

PCTFE / Kel-F® / NEOFLON™ Properties

1. •Near-zero moisture absorption
   

2. •Extremely low gas permeability
   

3. •Fantastic barrier material toward air, water, steam and many fluids, including liquid gases
   

4. •Very low outgassing
   

5. •Nonflammable, even in the presence of a high oxygen concentration
   

6. •Exceptional chemical resistance to all mineral reactants and most organic reactants
   

7. •Excellent corrosion resistance
   

8. •High optical transparency
   

9. •Excellent electrical insulator (even with high humidity and thermal cycling)
   

10. •Resistance to strong UV radiation
    

11. •Retains its properties upon exposure to gamma radiation
    

12. •High compressive strength
    

13. •Low deformation under load, superior rigidity
    

14. •Lower cold flow than other fluoropolymers
    

15. •Useful temperature range of -400 °F to +400 °F
    

16. •Superior cryogenic properties
    

17. •Expensive relative to many other materials
    

18. •PCTFE is attacked by many organic solvents
    

19. •Low coefficient of thermal expansion
    

20. •High dimensional stability
    

21. •Can be machined to precise dimensions
    

PCTFE / Kel-F® / NEOFLON™ Applications

Because PCTFE has high dimensional stability and compressive strength, it is a good structural material to use when the high temperature resistance and chemical resistance of fluoropolymers are required.  Although PCTFE has somewhat less heat resistance and chemical resistance than PFA and FEP, its mechanical properties are superior, especially its hardness.

Low outgassing and permeability make PCTFE ideal for laboratory and aerospace applications.

PCTFE is used for cryogenic applications such as liquid oxygen and liquid nitrogen handling.  Because PCTFE retains its mechanical properties over a wide temperature range down to almost absolute zero, it is used in refrigeration engineering.

Because PCTFE absorbs essentially no moisture, direct contact with water or high humidity do not affect its dimensional stability, allowing it to remain an excellent electrical insulator even in adverse climates such as the tropics and marine environments.

PCTFE has good resistance to ionizing radiation.  It is used in nuclear engineering components and uranium enrichment equipment.

Compression-molded PCTFE / Kel-F® / NEOFLON™ Parts

1. •Seals
   

2. •Lip seals
   

3. •Valve seats
   

4. •Valve stems
   

5. •O-rings
   

6. •Back-up rings
   

7. •V-rings
   

8. •Gaskets
   

9. •Washers
   

10. •Sleeve and thrust bearings
    

11. •Pump housings
    

12. •Linings of chemical processing components
    

13. •Containers
    

14. •Vessels
    

15. •Nozzles
    

16. •Balls
    

17. •Semiconductor parts
    

18. •Medical parts
    

19. •Rollers
    

20. •Wear pads
    

21. •Spacers
    

22. •Bushings
    

23. •Rings
    

24. •Plugs
    

25. •Cams
    

26. •Blocks
    

27. •Pads
    

28. •Guides
    

29. •Rods
    

30. •Caps
    

31. •Supports
    

32. •Miniature electrical and electronic components
    

1. 1.Connectors
   

2. 2.Crossbars
   

3. 3.Flanges
   

4. 4.Spigots
   

5. 5.Adapter plugs and pins
   

6. 6.Antennas   
   

PCTFE Compression Molding Resins

NEOFLON™ PCTFE from Daikin America

1. •NEOFLON™ PCTFE M-300H
   

2. •NEOFLON™ PCTFE M-400H
   

PCTFE / Kel-F® / NEOFLON™ Testing

1. •Tensile strength
   

2. •Elongation
   

3. •Specific gravity
   

4. •Durometer hardness
   

5. •Zero strength time (compression molded)
   

6. •Dimensional stability
   

7. •Dielectric strength