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Polytetrafluorethylene Thermoplastic |
| Polytetrafluorethylene (PTFE) is a high crystalline thermoplastic with excellent sliding properties, anti-adhesive surfaces, excellent insulation properties, an almost universal chemical resistance and an exceptionally broad temperature deployment spectrum. However, this is offset by low mechanical strength and a high specific weight compared to other plastics. The polytetrafluorethylene semifinished products that we offer – from which we also manufacture all finished parts – are produced in pressure sintering and ram extrusion processes, films are produced in a skiving process. Why use PTFE Fillers? 1. Significant increase of wear-resistance 2. Substantially enhanced resistance against creeping or deformation under load 3. Significant increase of thermal conductivity depending on type of filler used 4. Reduced thermal expansion 5. Possibility of changing electrical properties of PTFE, if needed, by using appropriate fillers 6. Selection of appropriate filler will also impact upon the wear behavior of the contra-rotating surface. Main properties
Sliding properties PTFE has excellent sliding properties, and because of its very close static and dynamic abrasion values, it prevents the stick-slip effect. However, due to its low mechanical strength, PTFE has high sliding abrasion and a tendency to creep (cold flow). Hence, unfilled PTFE is only suitable for sliding applications with low mechanical load. Its load bearing capacity can be mechanically improved by embedding the sliding element in a chamber. It must be ensured that the chamber is fully enclosed so that the part cannot escape (“flow out”). Chemical resistance Unfilled PTFE is resistant to almost all media apart from elementary fluorine, chlortrifluoride and molten or dissolved alkaline metals. Hologenated carbohydrates cause a slight, reversible swelling. In the case of filled PTFE a lowering of chemical resistance can be encountered, whereby it is not the PTFE but rather the filling material that forms the reaction partner to the medium. Machining PTFE is difficult to weld and then only by using an involved, special process. It can be machined. The semi-finished products can be drilled, milled, sawed, planed and turned on a lathe. It is also possible to cut a thread into the material or insert a threaded element. PTFE can also be bonded when the surface has been suitably treated by etching with special etching fluid. Up to approx. 19 °C, PTFE is subject to a phase transition which is normally accompanied by an increase in volume of at 1.2 %. This means that finished parts that are dimensionally stable at 23 °C can show considerable dimensional deviations at temperatures below 19 °C. This must be taken into consideration in the design and dimensioning of PTFE components. When the material is being machined, attention must be paid so that good heat dissipation is guaranteed for parts with minimum tolerances, otherwise the good insulation properties can lead to dimensional deviations in finished parts after cooling because of the heat build-up and thermal expansion. Fluoropolymers decompose above approx. 360 °C forming highly aggressive and toxic hydrofluoric acid. As polymer dust can form when the material is being machined, smoking should not be permitted at the workplace. |
Mr. Girish Dhawan
(Proprietor)
No. 170, Gali Bandook Wali, Ajmeri Gate
New Delhi,
Delhi -
110 006,
India
Telephone:+(91)-(11)-23215389/ 32972567
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