PTFE is the 'ultimate' high temperature needlefelt filter medium. Of all the fibres normally encountered it has the best combination of chemical and thermal properties.
PTFE is a very dense polymer and so produces very fine fibres with the potential to provide good filtration performance. Because the density is very high the volume of its fibres is quite low so to achieve the same volume of fibre as is found in a 550 g/m² polyester felt, approximately 850 g/m² would be required. A typical PTFE felt has a specific gravity around 0.65 whereas polyester is typically 0.30.
PTFE is available in 2 forms; white and brown. The brown comes from residual from the fibre production process. Brown tends to have more uniform fibre diameters, again due to the production process:
Brown
White
Typical applications for polypropylene needlefelts are:
| Incineration | Combustion |
| Chemical | Carbon Black |
PTFE is inherently very liquid repellent, (similar chemicals are the normal mechanism used in the textile industry for water proofing textiles) so it is very uncommon for treatments to be applied to the surface, though certain collection enhancing treatments are available such as embedded membranes:
In certain specialised applications, particularly for incineration, PTFE fibres are supplied blended with glass fibres to produce Tefaire™. This resultant felt can be a very efficient filter because friction and contact between the PTFE and the glass builds up electrical charges on the fibres (through triboelectricity) which attract electrically charged dust particles. The PTFE becomes negatively charged and the glass becomes positive, so attracting dust particles of the opposite polarity as shown in this image from DuPont where only the PTFE has collected a dust:
