We have earlier looked at Turcite B* and explained how it is a result of a very successful branding exercise that has stood the test of time. In truth, as we now know, Turcite* is a PTFE based composition and has been successfully substituted in many applications with equivalent PTFE formulations.
Another very successful branding venture has been that of Rulon*. Although we do not see the demand for Rulon* being as high as that of Turcite*, there has been a very conscious and well thought out strategy which has kept the compositions of this brand ambiguous, to the point that clients find it very tough to accept any alternatives.
In addition to this, the unique pigmenting of each Rulon* grade offers further ambiguity. Visually, a client is unable to reconcile with a substitute when the colors do not match. It should be mentioned here that in many cases, we have seen that pigments help alter the properties of PTFE in a very measurable and positive way. For example, the green-blue pigment of Turcite* has been proven to offer better PV values than the same composition in, say brown color. Therefore, while the pigmenting of Rulon* does help the branding considerably, we would assume the pigments themselves were not chosen randomly, but by testing different variants and choosing the one that had maximum impact on the properties required.
We have done some research to try and lay out the compositions of the most popular Rulon* grades, in the hope that it will make the choice a little easier for an OEM or manufacturer. In most cases, these appear to be regular PTFE grades that have been made unique using pigments. In some cases, such as Rulon J*, the grade is not regular, but can be easily blended as long as one knows the composition. The table below shows the various compositions and attributes of the most common grades of Rulon*.
|Product Description||Filler Details||Max Load (Mpa)||Max. PV ((psi-fpm); Mpa-m/s)||Properties||Colour|
|Rulon LR||PTFE+15% Glass||6.9||10,000; 0.35||High creep and abrasion resistance||Maroon|
|Rulon AR||PTFE+25% Glass||6.9||10,000; 0.35||Wear resistant, improved hardness, lower thermal expansion, lower deformation under load||Maroon|
|Rulon 142||PTFE+Bronze (40-60%)||6.9||10,000; 0.35||High thermal conductivity; better creep resistance; linear bearing material||Turquoise|
|Rulon 641||PTFE+15% Mineral||6.9||10,000; 0.35||Used mainly in food processing, FDA approved||White|
|Rulon J||PTFE+15% Polyimide||5.2||7500; 0.26||Good friction against soft metals||Gold|
We would like to point out a few things pertaining to the values of this table:
- The Load values of Rulon* across grades seem to be considerably lower than those of comparable regular grades of PTFE. For example, PTFE+15% Glass has a tensile strength of >20 Mpa when tested in-house – which is almost 3 times what Rulon* offers. The reason for this lowering of load metrics is not quite known. Most likely the addition of pigments causes some sacrificing of load values
- The PV values are comparable with regular grades of PTFE, however not so vastly different that it makes Rulon* superior in any obvious way. For example, Rulon LR* offers a PV of 10000, whereas PTFE+15% Glass offers only 7500. However, Rulon AR* also offers a PV of 10,000, whereas PTFE+25% Glass offers 12,000.
In a nutshell, we do not believe that the uniqueness of Rulon* pertains to any significant improvement in properties, but to a branding push given when PTFE was still an ambiguous material for many buyers. In recent times, many clients have adopted substitutes as they rightly feel the premium attached to Rulon* material is unjustified. Although rigorous testing is first done to prove that the substitute matches up with Rulon*, we have found that regular materials are more than equal to the task.
* Rulon is a brand name of Saint-Gobain Plastics; Turcite is a brand name of Trelleborg Sealing Solutions