PTFE – is an acronym for polytetrafluoroethylene. It is commonly referred to Teflon®, which is a registered trademark of DuPont. It is utilized as a sealing material because it is able to withstand significantly more aggressive chemical environments, (including highly oxidizing environments), than both rubber or graphite based material. However its operating temperature, pressure and mechanical performance can be inferior to standard non-asbestos or graphite gasket materials.
PTFE is principally used as a gasket material because it is essentially inert and has the capability to remain unaffected by the majority of chemicals used in industry. Also, it can be classified, in most cases, as a food grade material, making it acceptable to both medical and food production industries. There are four basic types of PTFE gasket materials. Virgin PTFE , filled PTFE, restructured PTFE and expanded PTFE .
Virgin PTFE – Virgin PTFE is simply pure PTFE resin that is sintered to form a solid material. It is the least expensive of the three varieties, and some of its mechanical properties are inferior to the other two.
Filled PTFE – Filled PTFE is made of virgin PTFE resin and fillers such as glass fiber to increase its mechanical and sealing properties. It is first formed into a billet, and then sheets of are cut or skived from the billet.
Restructured PTFE – Restructured PTFE is a gasket material made with a virgin PTFE resins and specific fillers for additional mechanical properties, and manufactured in a way that ensures the even distribution of those fillers throughout the sheet. The result is a material with much improved sealing characteristics. This material is strong, yet highly compressible with very good chemical resistance.
Expanded PTFE - is virgin PTFE to which a stress resistance has been added by means of molecular rearrangement during manufacturing. This process ensures that the molecular chains from which the PTFE is constructed, do not arrange themselves into set patterns. This means that expanded PTFE possesses no structural weakness (grain) and expands and contracts equally in all directions. Because no additives are required, expanded PTFE also possesses the unique chemical resistance of virgin PTFE .