Plastic selection

[Ken Heg]

Need to spin a brass pin in plastic as a bearing. Pin is brass. Which plastic is better for wear resistance, PC or POM? Pin dia is .093 inch Very low radial load. Speed is 4,000 RPM

 

[TugboatEng]

Does PC refer to polycarbonate? I don't think that is suitable as a bearing material.

 

[Ken Heg]

Yes, polycarbonate. I have been producing the part successfully for many years using Delrin (POM). Need to switch material because now it must be a clear material. Just wondering if PC will do the job knowing that delrin was successful.

 

[TugboatEng]

A transparent bearing? Perhaps polyurethane could meet that requirement.

 

[Ken Heg]

Sorry, more details. It is an injection-molded box that now needs to be clear. It has a hole into which a rotating pin is inserted. I can be grease lubed. Polyurethane makes injection molding difficult. So I am back to wondering if PC can stand up as well as Delrin has for this component.

 

[TugboatEng]

I can't find any examples of applications using polycarbonate as a bearing but this article seems to say that it is suitable.

Of the large range of polymers available, only a few are selected specifically for friction and wear. Acetal and nylon may be used for low PV applications. Likewise, PPS and PEEK may handle high temperature and high PV applications. And PC is an option when dimensional stability is needed.

https://www.machinedesign.com/archive/article/21816534/plastics-that-dont-wear-out-their-welcome

 

[Ken Heg]

Thank you tugboat.

 

[Pope5000]

Polycarbonate is amorphous while POM (Acetal) is highly crystalline. Amorphous materials have a significant higher wear rate, that means the self-lubrication properties of Polycarbonate unfilled and unmodified is up to 30 times worse then high crystalline polymers.

To overcome the issue you could use a PC up to 20% PTFE or other lubricant additives in it. But then it would not be transparent anymore. If you can use grease on the part, less to worry about this topic anyway...