Need Help Selecting an Appropriate Material 1

[Scott346]

Hi guys, I am designing a couple of injection molded plastics parts that have to slide across each other and I’m concerned about the coefficient of friction between them. The two parts will be molded from the same material although I have not decided on a material yet. Does anyone know where I might be able to find information about the coefficient of friction between various injection molded plastics?


Thank you,

 

[rickfischer51]

Try the IDES/Prospector database. They have a free version that will search for mechanical properties.

Rick Fischer
Principal Engineer
Argonne National Laboratory

 

[Shylanel]

The IDES database is a good source for base properties. In general a material with a low surface energy (HDPE, PP, PTFE, Delrin etc) will have low frictional coefficients. High surface energy materials like urethane and PPO will have higher coefficients. Truth is the surface 'texture', material hardness and applied force will have more significant impact.

 

[Tibo17]

One of the Golden Rules of Plastics Friction is... I am sorry... do not choose the same material for parts sliding on each other. This said, if you cannot afford to have 2 different materials then you'd may be able to have 1 grade for the 1st part and a slighlty modified grade for the 2nd one. In this case there will one material that will wear first. So you have to choose what parts should wear first.
As a general statement and taking a step back on plastic materials available for Injection Molding Technique I would say you'd probably find the POM or also called Polyacetal to be the best material to reduce friction. PA may also be good, but it should be compounded with additives reducing the friction. Some have small amount of PTFE, others Silicone oils or MoS2 inside.
Beside materials you'd consider part design of course: what is the surface of contact? Can you reduce it (in case you want the lowest friction possible)... And many other things to think about.

Thbaud Deleger
Empowering Polymers S.A.S.
Technical Writer & Polymer Consultant