PTFE (Polytetrafluoroethylene) Membrane Filters

SKC offers two types of polytetrafluoroethylene (PTFE) filters:

a) 60.0, 10.0, or 5.0 µm pore size PTFE filters are pure PTFE microfibres fused together at intersection points. These hydrophobic membranes provide ultimate chemical resistance and are temperature stable to 260°C.

b) 2.0, 1.0, or 0.5 µm pore size PTFE filters are comprised of a tighter PTFE membrane laminated onto a PTFE support. These filters have two distinct sides — the tight, smooth PTFE membrane and the rough PTFE support. The application determines the side used. The smooth side is easier to read under a microscope; expose the smooth membrane side to the air when collecting samples for microscopic analysis. The rough side holds dust more effectively; expose the rough laminate support side for gravimetric sampling.

PTFE Filters - Large Pore Size
PTFE Filters - Small Pore Size

The PTFE filters are:

  • Strong and resistant to acids, bases, and solvents
  • Hydrophobic
  • Low background, interference-free chemical determinations
  • Low tare mass for accurate gravimetric analysis
  • Temperature resistant to 260°C (500°F) — autoclavable
  • Ideal for aerosol sampling, especially in environments also containing water vapour
  • 13 mm filter meets NIOSH Method 5517 specifications

PTFE filters are the versatile choice for size-selective samplers. The material’s unique properties make it ideal for gravimetric, chemical, and/or microscopic analysis of sample particulate. PTFE filters are used for aerosol sampling, air venting and gas filtration. Note that the back pressure on PTFE filters can vary within the same lot.

Specific applications include:

Sampling for Particulate Matter:

PTFE filters with a PMP support ring are the recommended filters for particulate matter samplers such as the SKC Personal Modular Impactor (PMI), the Sioutas Impactor, the IMPACT Sampler, the Personal Environmental Monitor (PEM), and the Button Sampler. These filters feature low back pressure which allows longer sampling periods at higher flow rates to enhance sensitivity. See PTFE filters Part No. 225-1709, 225-1747, and 225-1711.

Sampling for Lactic Acid:

The US pharmaceutical industry has designated lactic acid powder as the surrogate particulate to detect fugitive emissions from drug compounding and pill manufacturing. SKC developed a 25 mm conductive polypropylene cassette with 1.0 µm PTFE filter and polypropylene support pad to minimize wall losses and permit in-situ extraction for enhanced recovery of lactic acid at nanogram levels. See PTFE Filter 225-1725.

Sampling for Metalworking Fluids (NIOSH 5524):

PTFE filter Part No. 225-27-07 with a 2.0 µm pore size and laminated PTFE support may be used with the thoracic Personal Parallel Impactor (PPI) to sample thoracic particulate according to NIOSH Method 5524 for metalworking fluids.

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