Fluoropolymers

High-Performance Plastics for Demanding Applications

Fluoropolymers are long-chain polymers in which a large proportion 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 excellent electrical insulation properties, superior weathering resistance, good notched impact strength, anti-adhesive behavior and they are self-extinguishing.

Typical areas of application for fluoropolymers are:

Automotive cables (sensor cable / NOX / Lambda)
High temperature cables
High frequency cables
Chemical resistant cables
Miniature cables
Flat ribbon cables
Heating cables
Control cables
Connecting cables

			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 the thermoplastic fluoropolymers are melted by means of 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

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 color 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 Production

As with paste extrusion, the PTFE powder must first be premixed for tape production, and a molded part produced. 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 bands can be used to bond various cables and lines in a further process. Before the PTFE is sintered, 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 using a wide slot die. This tape is stretched to very thin tapes on a special machine. The stretching is achieved 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 reached. These "expanded" films are partially sintered and are used as release films or insulation films.