Mar 31 2008
As ever-greater durability and reliability is demanded of pumps, valves and seals, engineers are turning to high performance plastics to deliver the extreme versatility required.
Dotmar EPP's Tetron family of Polytetrafluoroethylene (PTFE) plastic products is one solution ready, willing and able to be offered as an exceptional alternative to expensive imports of exotic valves and seals, says the company's General Manager Mr Scott Foster.
Tetron PTFE products are broadly applicable to uses as seals, seats, packings, chevrons, piston rings, glide rings, lantern rings, back up rings, slide bearings and electrical and thermal insulators.
“Virgin PTFE is capable in its own right. But when fillers are added, as they are with the entire Tetron range, it enhances the material wear and deformation characteristics to more fully exploit their unique combination of chemical, physical and electrical properties,” says Foster.
Applications that demand outstanding wear properties against soft counter faces, for example, are now being met by specially modified Fluoropolymer (PTFE) Ticomp S instead of traditional metals.
Custom engineered at Dotmar EPP, Ticomp S is a crystalline polymer filled fluorocarbon to provide the performance required in these situations. This material is a reliable handler of acid and caustic soda transfer in the food and chemicals industries when used in shaft sleeves of stainless steel pumps to reduce excessive wear of shafts and housings.
FDA-compliant Ticomp S performs in pumps and valves with a chemical resistance spectrum almost the same as virgin PTFE. High crystalline polymer provides a yield stress of 29 MPa, elongation of 305% and a Hardness Shore 64D.
Other applications where Ticomp S is commonly used include back up rings, lantern rings in slurry pumps, ball valve seats, as V-rings, as seals, washers and bushes, and as scrapers or slides. In these types of applications, it is the crystalline polymer in the PTFE that provides the appropriate performance characteristics.
Dotmar EPP also has other modified and virgin PTFE plastics within its Tetron range that cover countless applications in many heavy industries.
“As a virgin material, Tetron is affected by only a few chemicals and solvents, has outstanding dielectric properties, can operate continuously at 260ºC, has low-temperature toughness, slippery non-stick surface, and excellent UV-resistance,” said Mr Foster.
“But when filler is added they gain improved resistance to cold flow, reduced wear and friction, increased stiffness and surface hardness, improved thermal conductivity and dimensional stability.”
Special filled formulations often incorporate glass, carbon fibres, graphite, bronze or stainless steel and a specialty area of polymer fillers including Polyamides and Ekonol.
For example, hard and soft carbon alloys permit close tolerance machining, bronze fillers offer the best creep resistance; and graphite has good wear properties against soft metals – characteristics sought in hydraulic, pneumatic and fluid handling applications.
The Tetron range includes Tetron S as the chemically inert virgin material; Tetron G is glass filled, Tetron C is carbon filled; Tetron B is bronze filled; Tetron GR is filled with glass graphite, and Tetron T and Ticomp S Series are modified for special applications.
“The characteristics of Tetron surpass those of conventional insulating materials, even at elevated temperatures and frequencies. This is a characteristic which is seeing Tetron pin insulators increasingly used in high frequency cable plugs for coaxial cables,” said Mr Foster.
“As they absorb no moisture, parts customised from Tetron maintain integrity throughout an entire service life.
Tetron is available ex local manufacture as a stock shape in rod, sheet and thin section sheet or rolls together with a range of custom-moulded cylinders up to 600mm diameter. Typically, these materials are machined into seals, gaskets, seats, rings, expansion bellows, insulators and other components where the special characteristics of virgin and modified Tetron are used to bring advantage to mechanical solutions.