High-performance plastics for demanding applications

Fluoropolymers are long-chain polymers in which a large part or even all of the hydrogens contained are usually replaced by fluorine. Fluorine atoms have the highest electro negativity, which means that the carbon-fluorine compound has a very high binding energy. For this reason, fluoropolymers exhibit extremely high temperature and chemical resistance. They also have good electrical insulating properties, excellent weathering resistance, good notched impact strength, anti-adhesive behavior and they are self-extinguishing.

Typical applications of fluoropolymers are:

     

Thermal properties​

Mechanical properties

Electrical Properties

Fire properties
Abbreviation Chemical name VDE Ref. Continuous operating temperature 3000h [°C]

Continuous operating temperature 20.000h [°C]​

Melting range [°C] Tensile strength [Mpa] Stretch [%] Hardness Volume resistivity at 20°C Dielectric strength Dielectric constant at 1MHz, 20°C LOI Flame retardancy Halogen-free
PTFE Polytetrafluoroethylene 5Y 300 -190 to 260​ 320 - 330 >20 >200 55D - 65D

10^18​

20 2,0 >95 excellent no
PFA Perfluoroalkoxy tetrafluoroethylene copolymer 51Y 260

-190 to 250​

300 - 310 >20 >200

55D - 60D​

10^17​

25 2,1 >95 excellent no
FEP Perfluoroethylene-propylene copolymer 6Y 220

-100 to 200​

255 - 275​

>15 >200

55D - 60D​

10^18​

25 2,1 >95 excellent no
ETFE Ethylene tetrafluoroethylene copolymer 7Y 180

-100 to 135​

250 - 280 >30 >150

70D - 75D​

10^16​

36 2,3-2,6 >30 excellent no

Fluoropolymers are divided into thermoplastically processable (FEP, ETFE, PFA, etc.) and non-thermoplastically processable (PTFE) plastics. This results in different processing methods

While thermoplastic fluoropolymers are melted using extruders and then applied to the conductor and cooled, PTFE cannot be melted due to its high molecular weight. Various pressing and sintering techniques must therefore be used to process the powdered PTFE.

 

Manufacturing Competencies PTFE

PTFE Molded Part Dummy

Paste Extrusion

In paste extrusion, the PTFE is pressed onto the conductor under high pressure in a discontinuous process. Before the PTFE can be used in the paste extruder, a molded part (a so-called dummy) must first be produced. For this purpose, the PTFE powder is pre-mixed together with a lubricant and the pigment and compressed. These cylindrical dolls are filled into the paste extruder and pressed onto the conductor. The conductor is then sintered at very high temperatures. In this sintering process, known from ceramics, the compacted powder particles sinter together to form a homogeneous structure.

PTFE Tape

PTFE Tape Manufacturing

As with paste extrusion, the PTFE powder must first be pre-mixed and a molded part produced for tape production. The difference is that the PTFE is not pressed into a cylinder but into a full round rod. This round rod is then processed into a long thick thread called a "worm". In the next process, the worm is calendered to the desired width and thickness to form a strip.

The tapes can be used to tape various cables and wires in a further process. Before the PTFE is sintered here, too, the cables must first be "degreased" in a vacuum furnace and then sintered at high temperatures.

Expanded films (Hei-Tape)

For the production of expanded films (Hei-Tape), uncolored PTFE powder is also compressed into a full round rod. This is then pressed into a thick and wide tape by using a wide slot die. This tape is stretched to very thin tapes on a special machine. The stretching is realized by roller systems rotating at different speeds. A distinction is made between monoaxial and biaxial stretching. With monoaxial stretching, stretching degrees of up to 1000% can be achieved. These "expanded" films are partially sintered and are used as separation films or insulation films.