FEP filament
> Chemical composition and synthesis
Fluorinated ethylene propylene or commonly called FEP is a thermoplastic fluoropolymer created by DuPont. It was specifically designed for high-speed extrusion of thin coatings on small-gauge wires for twisted-pair constructions. [1] The structure of fluorinated ethylene propylene can be seen on Figure 1.
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FEP is a copolymer of HFP (produced by pyrolysis of TFE) and TFE. It is commercially produced by random copolymerization of TFE and HFP in an aqueous media using free-radical initiation. [3] This is done by a water-soluble peroxyde which is typically potassium persulfate. [4]
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> Properties
> Properties
> As printing material
The FEP filament has very similar properties than PTFE except for thermal properties. [3] Indeed, it is has a lower thermal stability than PTFE. However, it is well known for its heat resistance, toughness, low flammability, no moisture absorption, performances at extreme temperatures and chemical inertness. [1] Features which look very attractive for the drone application. Its thermal and mechanical properties can be found in Tables 1 and 2 :
Table 1 : Thermal properties of FEP filament. [1] [5]
Table 2 : Mechanical properties of FEP filament. [1] [5]
FEP filament was especially designed to print at high speed of extrusion compared to the other fluoropolymer resins. [1] The parameters of interest to print with FEP can be found in Table 3.
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Notice that a printing temperature of 320 - 380 °C (as required) is not reachable with the 3D printer Makerbot. Furthermore, FEP filament can liberate toxic fumes when it is overheated and contacts between FEP and metals like aluminium can be explosive or flammable under specific conditions. [1]
Table 3 : Printing properties of FEP filament. [5]
In conclusion, this polymer has very interesting thermal properties for a drone application. Indeed, it can easily withstand temperatures as 180 °C. However, this polymer causes some safety problems and its printing temperature is not reachable. Moreover, it has a density of 2,16 g/cm³ which is too much for a drone and a too low tensile strength. This is why this polymer was not chosen to be the right material for our drone despite its wonderful thermal properties.
> As printing material
> Conclusion
> Bibliography
Figure 1 : Structure of FEP filament. [2]
[1] "Dupont Teflon FEP TE9495 - Fluoropolymer resin - Product information", http://www2.dupont.com/Teflon_Industrial/en_US/assets/downloads/K18308_FEP_TE9495.pdf, accessed on 12/03/2017.
[2] "Brevet - Materials and methods for temporarily obstructing portions of drilled wells", https://www.google.ch/patents/US20110278011, accessed on 06/05/2017.
[3] Bruno Ameduri and Hideo Sawada, Fluorinated polymers : Applications : Volume 2, Royal Society of Chemistry, 2016, pages 87-88.
[4] "Introduction to fluoropolymer", http://www.fluoroconsultants.com/sitebuildercontent/sitebuilderfiles/introductiontofluoropolymers.pdf, accessed on 06/05/2017.
[5] "Plastic2print - FEP natural filament", https://www.plastic2print.com/175mm-fep-filament-0-75kg.html , accessed on 12/03/2017.