Static Friction of PEEK/PEEK; CFR PEEK/PEEK couples et. al.
Static Friction of PEEK/PEEK; CFR PEEK/PEEK couples et. al.
(OP)
I'm working on a device where two PEEK surfaces are moved relative to each other in discrete fashion under load. In this situation overcoming the static frictional force is a concern as it is manually actuated. This motion is one time only for assembly so wear is not a significant concern.
I've been looking for frictional coefficients for these materials but I'm most interested in these specific pairing and that is not often given.
E.g. I've found one source for PEEK 450G dynamic coefficient as 0.4 and for 30% CFR PEEK dynamic coefficient as 0.19 (both dry vs. steel). What I don't know is the static coefficients which are presumably higher and perhaps not proportional. Additionally, I don't know the interaction between like/dislike polymers as in this case compared to vs. steel.
So if numbers can't be provided I'm still interested to discover what the heirechy of the friction couples might be.
CFR/CFR->CFR/PEEK->PEEK/PEEK?
or perhaps no notable difference?
I've been looking for frictional coefficients for these materials but I'm most interested in these specific pairing and that is not often given.
E.g. I've found one source for PEEK 450G dynamic coefficient as 0.4 and for 30% CFR PEEK dynamic coefficient as 0.19 (both dry vs. steel). What I don't know is the static coefficients which are presumably higher and perhaps not proportional. Additionally, I don't know the interaction between like/dislike polymers as in this case compared to vs. steel.
So if numbers can't be provided I'm still interested to discover what the heirechy of the friction couples might be.
CFR/CFR->CFR/PEEK->PEEK/PEEK?
or perhaps no notable difference?





RE: Static Friction of PEEK/PEEK; CFR PEEK/PEEK couples et. al.
Secondly, I would not worry at all about the COF as adding lubricant will have a far greater effect than changing material will.
If you can't use a lubricant applied topically then you can use solid additives in the PEEK to reduce friction. Hexagonal boron nitride is one, titanium carbide is another. There are others such as PTFE and silicones.
Chris DeArmitt PhD FRSC CChem
www.phantomplastics.com
Consultant to the plastics industry
RE: Static Friction of PEEK/PEEK; CFR PEEK/PEEK couples et. al.
RE: Static Friction of PEEK/PEEK; CFR PEEK/PEEK couples et. al.
Specifically, CFR PEEK and PEEK have a clinical history and master files with the FDA which is why I was so specific.
I tried to do a bench test with a CFR PEEK plate I had by inclining it but it was very unscientific (I don't have uniform shapes of each material to test). Suffice to say that the CFR PEEK chip I had seemed to require a larger angle to break static friction than the PEEK parts though I can't put too much stock in that result as it was not easily repeatable. Regardless, I'm having some identical prototype components made in each material so I'll be able to do a functional test anyhow.
Again, thanks for the help.
RE: Static Friction of PEEK/PEEK; CFR PEEK/PEEK couples et. al.
RE: Static Friction of PEEK/PEEK; CFR PEEK/PEEK couples et. al.
Place the one material on the other and increase the angle until the top one slides. Repeat 5 times and write down the angle needed to make it slide.
Take the tangent of the angle. That is the static COF.
Chris DeArmitt PhD FRSC CChem
www.phantomplastics.com
Consultant to the plastics industry
RE: Static Friction of PEEK/PEEK; CFR PEEK/PEEK couples et. al.
RE: Static Friction of PEEK/PEEK; CFR PEEK/PEEK couples et. al.
Dave: I have contacted Invibio and they may be trying to establish this data for me. They admitted they don't have any data on PEEK-PEEK. I found a white paper associated with the NUBAC device (PEEK-PEEK) from Pioneer but unfortunately not any friction numbers. I'm still somewhat new to CFR PEEK but I have seen some data on Pitch vs. PAN CF--what exactly is the difference? Does Invibio only use pitch fibers?
Side note: Victrex now has a PEEK master file with the FDA but I do not believe any devices using their PEEK have been cleared yet--it's irrelevant to me due to contractual agreements with Invibio in any case.
RE: Static Friction of PEEK/PEEK; CFR PEEK/PEEK couples et. al.
RE: Static Friction of PEEK/PEEK; CFR PEEK/PEEK couples et. al.
Chris DeArmitt PhD FRSC CChem
www.phantomplastics.com
Consultant to the plastics industry