Complex geometries as customized solution
Based on your samples, drawings, and blueprints, we can manufacture molded blanks as well as finished parts to your specifications. And we can do this not only with PTFE and its compounds, but with all the most common fluoroplastic materials.
We are masters of nearly every mechanical processing technique, including the most up-to-date CNC equipment such as lathes, mills, drills, saws, grinders, and automated lathes.
PTFE - the specialized fluoroplastic
Polytetrafluoroethylene (PTFE) is a linear polymer with the following formula:
-[CF2-CF2]n- and a molecular weight between 105 and 107 .
PTFE is by far the most important fluoroplastic. PTFE is sold under the trademark names: Teflon ® , Dyneon TM , Fluon ®.
The exceptional properties exhibited by PTFE are the result of its chemical structure.
- PTFE is temperature resistant between -200° and +250°C under conditions of continuous use.
- PTFE is completely resistant to chemicals and can therefore be employed almost universally.
- PTFE has an extremely low coefficient of friction, thus eliminating any stick/slip effect.
- PTFE has the lowest relative permittivity and the lowest dielectric loss factor of any plastic, together with high specific transient resistance and surface resistance.
- PTFE is extremely anti-adhesive.
PTFE can be mixed with inorganic materials such as fiberglass, bronze, graphite, carbon, or molybdenum sulfide (compounds). This can significantly alter the properties, particularly with regard to pressure resistance, thermal expansion, electrical values, and abrasion.
When processing PTFE, the following process steps are performed: compression, sintering, and cooling. Processing exerts a major influence on the molecular weight, crystalline structure and pore content of the molded parts and, therefore, on their quality.
TFM™PTFE is a branched chain polymer, with the following formula:
The perfluorated side group is identical to that of PFA, but is present in distinctly fewer numbers. The molecular weight is only approx. 1/5 that of PTFE, while PFA has only 1/100 of the molecular weight of PTFE. It therefore fills in the "properties gap" between PTFE and PFA without having to be processed in an injection molding procedure, as is the case with PFA.
- TFM™PTFE is temperature resistant between -200° and +250°C under conditions of continuous use.
- TFM™PTFE is completely resistant to chemicals and can therefore be employed almost universally.
- The rate at which gases permeate TFM™PTFE is distinctly lower than that through conventional PTFE and only a bit higher than that through PFA.
- Compared with PTFE, TFM™PTFE has distinctly improved surface characteristics.
- As a result of a "shift in the direction of a thermoplastic", TFM™PTFE can be bonded using a special process.
- TFM™PTFE exhibits better cold-flow properties, pore content and stretch-void index.
TFM™PTFE can be mixed with organic materials such as fiberglass, graphite, or carbon (compounds). This can significantly alter the properties, particularly with regard to pressure resistance, thermal expansion, electrical values and abrasion.
When processing TFM™PTFE, the following process steps are performed: compression, sintering, and cooling. Processing exerts a major influence on the molecular weight, crystalline structure and pore content of the molded parts and, therefore, on their quality.
A number of mixtures of PTFE or TFM and inorganic fillers is offered under this heading. Of the many available options, the following fillers have shown themselves to be particularly useful:
- Glass (generally in the form of short fibers);
- Metal powders (bronze, chrome nickel steel);
- Molybdenum sulfide;
as well as mixtures of these.
Depending on the type of filler material involved and the mixture's proposed application, PTFE or TFM compounds can contain from 5 to 40 parts filler material, by volume.
Fillers can be used to achieve improvements in the following properties:
- Increased pressure resistance;
- Improved thermal conductivity;
- Increased wear resistance;
- Decreased thermal expansion.
PTFE or TFM compounds are available in free flowing and not free flowing versions. Processing is similar to that for fluoropolymers without fillers, however, higher molding pressures are required. Depending on the filler content, these pressures lie between 300 and 700 bar and, in the case of automated molding, may even rise as high as 1500 bar.
PTFE/TFM without fillers
In mechanical engineering, in electrical engineering, as insulation, in chemical equipment construction for seals and chemically resistant components, for bellows and laboratory equipment.
PTFE/TFM with carbon
For hydraulic seal elements, for parts requiring good thermal conductivity, for pressure and wear resistant parts, for bearing bushes and seals, for valve seats.
PTFE/TFM with graphite
Good thermal conductivity with adequate elasticity and good storage characteristics, for seal elements, especially lip seals.
PTFE/TFM with fiberglass
Pressure resistant, even at higher temperatures, minimum cold flow, for chemical pumps, bearing bushes, and seals.
PTFE with bronze
High pressure and wear resistance, especially well suited for bearings and guides.
The isostatic molding method in PTFE processing
Isostatic molding offers the possibility of manufacturing complex molded shapes as well as hollow bodies and liners while, at the same time, offering significant reductions in both the amount of material employed as well as the mechanical rework required.
The isostatic molding method is based on the physical law that pressure propagates uniformly in all directions in gases and liquids and produces forces on the surfaces under pressure that are directly proportional to these surfaces. In actual PTFE processing, a rubber mold is filled with PTFE powder and then sealed against liquids. This mold is then placed in the pressure vessel of a molding unit.
Advantages of the Isostatic Molding Method
- Quality advantages thanks to isostatic compression
The advantages of isostatic compression molding can be illustrated by means of appropriately enlarged REM images.
When magnified 100 times the granulate particles of the original material can still be identified in PTFE if it has been subjected to single-axis compression molding.
By contrast, isostatically compression-molded PTFE shows a significantly more consistent surface structure. It is roughly equivalent to single-axis compression-molded TFM™PTFE. However isostatically compression-molded TFM™PTFE achieves a much finer and smoother structure.
Furthermore, when magnified 2,500 times, in single-axis compression-molded material flaws become visible, which no longer occur in isostaticaly compression-molded TFM™PTFE.