coefficient of friction for plastics

[njlee]

hi all,

where can I find info about coefficient of friction for plastics? any good websites or books? i'm designing a ball joint and thinking about using pp on pc Or pp on pp. I also need to know the compatibility and wear issues. I can find info regarding individual plastics but i need to know wether two materials will work well together.

thanks!!

Lee

 

[patprimmer]

LNP, RTP and DSM will all have good information. I have it in the form of pamphlets, but it is probably now avaliable on their websites.

LNP is now a part of GE engineering Plastics.

I can probably help if you can't find it, but I am a bit stuck for time right now

Regards
pat pprimmer@acay.com.au
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[Pud]

Hi njlee,

Quite by chance, in PP and PC you have probably got the worst combination you could get. PC (unfilled) is pretty poor as a bearing as is PP.

For a ball joint (especially if a "snap" fit), it would be common to use POM (Acetal) as the socket and PBT as the ball. These two together are a good bearing and also quiet in operation (two materials the same often squeak!)

The Ticona website has snap fit calculator to use, or you could call them and get their publication on the subject. Very good info from these, and maybe Dupont also (Delrin) (log in/register is pretty tedious if I recall)

Rgds


Harry

 

[njlee]

hi,

Thanks for the response! I will check out the GE site. I'm not doing any snap fit ball joint, the load will be very small (0.5 lb to 1 lb, 1 inch diameter ball), the contact will be close to line contacts (top and bottom of the ball). Acetal on PC is my first choice but I need to explore the possibility of using PP on PC or PP on PP. Since PP is a soft material, I'm just worried about the wear issue.

thanks!
lee

 

[patprimmer]

Acetal on nylon also works very well as a bearing.

PTFE and silicon oil in the acetal, and molly and graphite in the nylon also helps.

Regards
pat pprimmer@acay.com.au
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.