PTFE (Polytetrafluoroethylene) is suitable for sealing duties with most chemical media across the whole PH range; the exceptions being molten alkali metals, fluorine gas and any substances that may generate these at the operating temperatures and pressures involved. It has an operating temperature range of -200OC to 250OC.
In addition to chemical resistance pure or virgin PTFE is well suited in FDA applications where process contact with foodstuffs is required. Having a very low co-efficient of friction, PTFE can also be used for slide bearings, non-stick applications and can be bonded to various substrates if the bonded surface is chemically etched.
Pure PTFE under certain process conditions is not always dimensionally stable and can creep or cold flow under load, loosing gasket stress applied. PTFE Envelopes and Modified or Expanded PTFE materials have been developed to suitably reduce these effects.
PTFE Envelopes can be manufactured to fit most soft cut gasket materials in all thicknesses and diameters, where the recovery of the protected gasket/composite gasket compensates for the minimal creep associated with the thin wall section of the envelope.
Whilst a multitude of fillers can be used, glass has evolved as the most common, improving both dimensional stability and wear resistance; it is readily available in either 15% or 25% filled options. Care must be taken in selection as the use of fillers can impair chemical resistance and in commercial, non-proprietary grades can often remove FDA compliance.
Modified (being reinforced or expanded) PTFE available from SEP, represents the latest generation of multi-directional grade materials from leading brand manufacturers such as KLINGER (TopChem), NOVUS (Uniflon), FLEXITALLIC (Sigma), WL Gore (Gore-Tex), GARLOCK (Gylon).
Benefits and Features of modified
• Outstanding chemical resistance
• Improved creep resistance properties
• Extremely low gas permeability
• Wide service temperature range
• Excellent sealing performance, even at low seating stress
• Conforms well to glass lined, ceramic, plastic coated and irregular/uneven flanges • Conforms to FDA regulations
• Environmentally friendly
• Easy to cut, handle and remove from flanges after service
• Up to 2000mm diameter one piece gaskets
• ’Fire-safe’ grade
No single material will have
all the desired properties, indeed some properties may only
exist in one grade, therefore please contact our technical
sales team for selection assistance of sheet materials, cut
gaskets and available
tape types and sizes.