Plastic with Impressive Qualities
PTFE is a plastic that brings together an unparalleled combination of outstanding properties, making it the ideal material for application areas not open to other plastics.
PTFE is suitable for use over an exceptionally wide temperature range. Components made from this material retain their properties at temperatures between -260°C and +260°C (and even up to +300°C for short periods).
The strong fluorine-carbon bonding and the almost complete shielding of the C-atoms by fluorine give PTFE virtually universal chemical resistance.
- Neither solvents, such as alcohols, esters, and ketones nor aggressive acids change the properties of PTFE. A reversible 4–10% increase in weight has only been measured when used in refrigerants (e.g., Frigen).
- At higher temperatures and pressures, PTFE reacts with elemental fluorine and chlorine trifluoride.
- Monomers, such as styrene, butadiene, or acrylonitrile can penetrate PTFE or modified PTFE in small amounts and, in the event of conditions triggering a spontaneous polymerization, this may lead to swelling of the material.
Light and Weather Resistance
PTFE has outstanding light and weather resistance and is therefore suitable for outdoor use even in extreme weather conditions without limitation and without any noticeable changes to its mechanical or electrical properties.
Fluoropolymers are the least flammable of all plastics. The gaseous decomposition products will only ignite in the immediate vicinity of an external flame. After the flame is removed, the combustion process stops immediately. The ignition temperatures according to ASTM D 1929 are within the range of 500 to 560°C and the LOI index (oxygen index) is 95%. According to Underwriters Laboratories (UL), the various PTFE types are listed in fire class V-0. The electrical and mechanical relative temperature index (RTI) for PTFE is generally at 180°C.
PTFE absorbs practically no water. Even after storage in water for long periods according to DIN 53472/8.2, no absorption of water has been noted.
Unfilled PTFE is physiologically inert. Consequently, the use of this material is permissible in both medical and food applications. A highly positive characteristic in this respect is the material’s resistance to hot vapor, which means that PTFE components used in the medical, pharmaceutical, and food industries are well suited to sterilization.
Adhesivity of pure PTFE is very low, which is attributable to the shielding of the carbon chain by the fluorine atoms and their low polarizability. The advantage of this is that process media cannot adhere to PTFE components.
Adhesive Bonding Capability
Weak intermolecular forces and the low polarizability of the fluorine atoms are the reasons why PTFE offers poor adhesive bonding capabilities. Adhesive bonding therefore requires a chemical pretreatment of the surface, e.g., with sodium dissolved in ammonia or by means of plasma etching.
Tetra-Etch® is a perfect solution for pre-treating of PTFE. Please contact
Polytetra GmbH. Phone +49 (0) 2166 9590 0 or Email to
Tetra-Etch® is a trademark of W.L. Gore & Associates
PTFE can be welded under certain conditions. In this case, a PFA hot melt adhesive is used as the coating connecting the two PTFE surfaces. Modified PTFE may be welded without any welding aids. For thin films, hot bar welding equipment capable of applying the required temperatures of approx. 350°C is suitable. Thicker profiles require a special welding process: the surfaces do not need to be etched but it requires very high temperatures of 325–335°C.