There are other bearing materials. Knowledge of the application would help us in making any recommendation. And the problems that you have in using PTFE. Delrin UHMW-PE both can be used as bearings. Their use will depend on the application.
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If you have a balanced load, the best you can get (for low friction) is an AIR BEARING. They are a bit complex though!
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Please tell us a little more about your application. You can't just say "which bearing has the lowest friction?". The real answer depends on the shaft material, surface roughness, lubrication, speed, load (how much and whether perpendicular or parallel), temperature, whether we can run this thing in a vacuum or dry nitrogen, etc.
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"Well, I've wrestled with reality for 35 years, Doctor, and I'm happy to state I finally won out over it." Elwood P. Dowd
Depending if you need roller or a linear bearing, ceramic bearings are low friction. Boca bearing and VXB offer hobby and industrial applications. If is going to be in a dusty or more harsh environment you can try the ball-less bearings that are oil impregnated bronze.There is no slides or balls to gum up the lube or product in. I would recommend checking out Global Spec to search for some bearing manufactures.
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Rulon bearings are available in a variety of grades for a wide range of applications. Contact Joe Cativo at Saint Gobain Performance Plastics in Bristol, Rhode Island with your specific application and he should be able to recommend a solution.
Actually, it would be best to describe the application requirements and the reason why PTFE would not be acceptable. Important questions are: 1) bearing pressure, 2) linear/rotary speed, 3) mating surface and finish, 4)chemical exposure, 5) other foreign materials and concerns?
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