Tribologically Valuable

New friction bearing versions provide the design engineer with a material that combines many properties which were previously available only separately with different friction bearings. In addition, this new development means that the design engineer does not have to accept any compromise in the case of difficult tribological applications. The key to success is called Moldflon.

ElringKlinger Kunststofftechnik has been active in the field of developing fluorinated high-performance plastics for over 50 years and is one of the leading PTFE processors in Europe. For many years the PTFE compounds from which the friction bearing materials Elringplast J, LD and W2 are made have been an integral element of mechanical engineering for special tribological requirements.
By developing the new Moldflon material (PTFE that is suitable for thermoplastic processing), the company has succeeded in extending the key characteristics of PTFE such as low friction coefficient in dry-running operations and extremely high temperature and chemical resistance by properties which are essential for friction bearings like pressure stability and wear resistance.
The so-called cold flow, a property of the compressed-sintered PTFE material that has tended to be a disadvantage so far, has been reduced by a multiple in the case of Moldflon. In the unfilled state, Moldflon exhibits merely half the cold flow rate of PTFE with 60 % bronze which is frequently used as a friction bearing material in hydraulics.  
Due to this development the Moldflon material and its compounds exhibit an ideal combination of properties which no other friction bearing material before has been able to meet:

• Temperature resistance up to +260 °C
• Universal chemical resistance
• Very low friction coefficient enabling
• Very high peripheral speeds (up to 5 m/s in dry-running operations)
• Outstanding wear properties
• Approvals possible as with conventional PTFE (BAM, FDA, 3A etc.)
• Very high p x v values in dry-running operations (above 2.5 N/mm² x m/s)
• Very high static pressure strengths (up to 80 N/mm²)
• No corrosion, no absorption of moisture

Due to the structure of the long-chained carbon fluorine combination all Moldflon friction bearings are very tough materials and possess very good damping properties and resistance to edge compression. These friction bearings relieve all sectors with special requirements including, among others, the chemical and food processing industries, from the need to accept compromises. The automotive industry, as well, benefits from the plastic friction bearings which continue to deliver service beyond temperatures of 250 °C, in the engine compartment for example, with very low friction coefficients.
Moldflon friction bearings have demonstrated their wear resistance in numerous laboratory tests. The wear rate of food-conformant Moldflon friction bearings compared with commonly used full-plastic friction bearings with and without approvals is much lower in some cases. Customer thus not only benefit from the very good basic properties of PTFE but, in addition, can achieve a competitive advantage for their application by benefiting from all the tribological properties which a friction bearing of the future should satisfy such as low wear, low frictional heat and long service life.

Nearly Unlimited Design Options

Moldflon friction bearings offer nearly unlimited design options because they can be produced by injection molding. Special dimensions and customer-specific designs coupled with the selection of suitable materials are just one of the strengths of engineering. The friction bearings are produced according to ISO 3547 and DIN 1850 as standard products. Samples are available at short notice as machined versions or made from a prototype mold.
Another advantage of PTFE is the possibility of using this material as a seal as well. Consequently, two diverging functions – bearing and sealing — can be combined in a single component for the first time. This harbors significant savings potential for engineering design and assembly.
Due to years of experience in the field of fluorinated materials customers can draw on in-depth materials know-how regarding the selection and design of their friction bearings.

Materials for Any Tribological Application

Together with the PTFE friction bearings of the Elringplast J, LD, W2 range and the metallically rolled M-Liner bushings with PTFE anti-friction coating the development of the Moldflon friction bearings offers a very wide range of materials for any tribological application.
In addition to unfilled Moldflon (MF10005) for lower pressures, two other high-performance compounds are available:

• Moldflon MF10005 with the lowest friction coefficient for highest peripheral speed
• with universal chemical resistance and food conformity
• Moldflon MF40003 for highest p x v values and lowest wear
• Moldflon MF40002 for highest surface compression and conformity

Unlike other full-plastic friction bearings in which PTFE is added to reduce the friction coefficient and achieve dry running, Moldflon friction bearings are made of 100 % PTFE. Their suitability for melting processes (fusion) results in a material in which the fillers are completely homogenously embedded. This ensures that the lowest friction coefficient is available at all times and that all properties are preserved at consistent quality across the product's service life.
The new friction bearing versions provide the design engineer with a material that combines many properties which were previously available only separately with different friction bearings. Today it is possible to avoid having to make compromises in difficult tribological applications.
Online info
www.kem.de/0610
Der Autor Name ist Funktion bei der Firma, Ort
Dennis Wager
is a member of the field sales force of
ElringKlinger Kunststofftechnik GmbH
Bietigheim-Bissingen
Bilder:
elring1.jpg: Coldflow [%]
elring2.xls: Wear, rotating application with X90 shaft, load p = 0.75 MPa, v = 0.83 m/s