Tech Talk Blog

The Dixon M-Liners from Saint Gobain have become very difficult to obtain since they come from overseas. Tri Star is now offering a size for size equivalent product in it’s Tri Steel product line called Tri Steel PE. This product is a rolled steel backed polymer lined bearing. The polymer liner is a special PEEK/PTFE combination that has a thicker dimension  than normal steel backed bearings. This allows for post machining of the ID to tighter tolerances without removing the primary bearing source. Learn more from Tri Star’s website www.tstar.com and review the information on Tri Steel Bearings or watch our Tri Steel video on the Video Learning Center.

The growth of plastics in medical devices is growing exponentially around the world.  Plastics are regulated like any other materials that may come in contact with human tissue or fluids and that usually falls under testing procedures issued under USP or ISO10993. There are three time scales for biocompatible devices. “Limited” would be less than 24 hour exposure, “Prolonged” is 24 hours to 30 days and “Permanent” is 30 days and longer. Device’s are categorized as Surface Devices which would be items such as electrodes for monitoring, contact lenses, catheters, endotracheal tubes, sigmoidoscopes and similar devices. Second would be Externally Communicating Devices such as  laprascopes, blood administration devices, pacemakers, oxygenators and the like. Finally are Implant Devices such as orthopedic pins or plates, heart valves, grafts, stents and similar devices.

Testing of these devices includes mechanical, thermal, chemical tests as well as systemic injection, intracutaneous and implantation. All of these must be done before a plastic component can be approved. Typical materials for biocompatible applications include medical grades of PVC and Polyethylene, PEEK, Polycarbonate, Ultem PEI, Polysulfone, Polypropylene and Polyurethane. For more specific information on Biocompatible materials as well as special plasma preparation treatments of all of these materials, contact TriStar Plastics at www.tstar.com and visit our Video Learning Center and our Materials Database.

Ultracomp Composite Bearings are designed for extreme loads where impact and vibration may occur. Because of it’s very high impact strength it can take extreme loads as well as shock loads. Ultracomp requires no lubrication which eliminates maintenance, is much kinder to the environment and reduces overall costs of ownership.  Ultracomp absorbs virtually no moisture, takes static loads up to 55,000 psi and handles dirty, gritty environments. Ultracomp is also an excellent underwater bearing for applications as diverse as bowthrusters, rudder bearings, roller bearings, dockside equipment exposed to salt air and water. Also an excellent bearing material for construction, material handling and ag equipment.

Visit our Video Learning Center to learn more about all we have to offer.

UHMW Polyethylene is an interesting material in the polymer world.  It’s one of the lowest cost plastics on the market yet it offers some properties that few other polymers do. UHMW is best known for it’s abrasive wear resistance and impact strength but even within this small polymer family there are variations. UHMW stands for ultra high molecular weight and under this description UHMW is produced with a molecular weight range of 3.5 to 6 million. The molecular weight has a fairly dramatic impact on several key properties. For instance, a 4 million molecular weight grade has an abrasion resistance of 100 when measured using a sand slurry test. A 6 million molecular weight is 75 which is a further 25% improvement! Compare this with steel which has a resistance of 160 and you can see why UHMW is the material of choice for abrasive wear environments.

There are several other variations on UHMW including cross linked, glass and moly enhanced and even a high temperature grade.

Check out our Materials Resources Guide to see the entire selection.

Torlon PAI from Solvay is one of the outstanding polymers for high temperature applications. Torlon is available in various forms and with different enhancements to meet diverse applications such as bearings, dielectric insulators and structural components. Torlon’s physical properties maintain very high values even at the maximum operating temperatures.

You can learn more in our Video Learning Center, too!

Question: I am using Rulon J on a very small diameter shaft with a light load and medium speed condition. For some reason I am getting more stiction and friction than I expected. Any suggestions?

Answer: One of the issues with Rulon and any PTFE based bearing material is that there is an optimal load range to get the performance you desire. If the bearing is too lightly  loaded you will experience an increase in friction. That is a phenomenom common to PTFE. The thing to remember is the higher the load, the lower the friction. Reducing the surface contact area by either shortening the bearing or machining small reliefs on the ID of the bearing will increase surface loading. That will in turn reduce the friction. It may take some experimenting to get the result you want but it really does work!

High temperature polymers have been around for many years but industry is just now learning the value of these unique materials. Imidized materials like Celazole (PBI), Vespel and Meldin (PI) and Torlon (PAI) are able to maintain high physical strength in the 500-750F operating range. These materials have excellent wear properties and are available in many blends which enhance friction/wear properties, structural strength and thermal stability.

Sit back and learn a little more. Take a peek at our Video Learning Center.