PTFE Filled Plastic
PTFE Filled Plastic
(OP)
I am looking to use a PTFE filled plastic in a gear application and I am trying to decide on what type of PTFE to use. What is the difference between a recycled PTFE and PTFE from Dupont?
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RE: PTFE Filled Plastic
You need to decide what your base polymer requirement is and then decide why you need PTFE as a filler. Most plastic gears are made from either acetal (POM) or some sort of polyester (usually PBT) without PTFE.
Ticona have a good technical background in POM for gears. You might try your local office. There may be others.
I have no idea what recycled PTFE is - for a guess it's "Greenwash".
Cheers
Harry (Yes, call me a cynic...)
www.tynevalleyplastics.co.uk
RE: PTFE Filled Plastic
http://www.shamrocktechnologies.com/home.html
Chris DeArmitt PhD FRSC CChem
www.phantomplastics.com
Consultant to the plastics industry
RE: PTFE Filled Plastic
Chris DeArmitt PhD FRSC CChem
www.phantomplastics.com
Consultant to the plastics industry
RE: PTFE Filled Plastic
Demon - note the "filled". Gears (unless hypoid) should not "slide" - stresses are cyclic compressive, so PTFE rather irrelevant. Gears usually use PBT/POM combinations for low noise.
Perhaps the OP could elucidate us on the application?
Cheers
Harry
www.tynevalleyplastics.co.uk
RE: PTFE Filled Plastic
OP, please listen to Harry over me on the stuff about what to use for gears. He's great at application experience.
Chris
Chris DeArmitt PhD FRSC CChem
www.phantomplastics.com
Consultant to the plastics industry
RE: PTFE Filled Plastic
Thinking about it, some your old place's stuff could potentially have been good for gears..
Oh well, that's history I guess.
Cheers
Harry
(Apologies to op for the hijack, only this IS my troll account! [joking])
www.tynevalleyplastics.co.uk
RE: PTFE Filled Plastic
Chris DeArmitt PhD FRSC CChem
www.phantomplastics.com
Consultant to the plastics industry
RE: PTFE Filled Plastic
Chris DeArmitt PhD FRSC CChem
www.phantomplastics.com
Consultant to the plastics industry
RE: PTFE Filled Plastic
The only grade number I remember is Fluon L169 I think. It's been 20 years or so now. DuPont, Asahi and Hoechst and some Italian company all made grades. The biggest market used to be useless after market engine oil additive.
Unless recycled was pure enough then ground to appropriate particle size and shape then made friable by the gamma rays, the PTFE will not be adequately dispersed and will not have the best particle size and surface area.
PTFE does reduce the co-efficent of friction of POM and a silicone oil additive that is available as a master batch has a synergistic effect.
POM also has very good compatibility with nylon as a gear or bearing. Compared to polyester, nylon changes dimensions with water uptake, but is also tougher, so it all depends on the exact requirements and environment.
Regards
Pat
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RE: PTFE Filled Plastic
Does anyone have any experience using it in acetal?
RE: PTFE Filled Plastic
Chris DeArmitt PhD FRSC CChem
www.phantomplastics.com
Consultant to the plastics industry
RE: PTFE Filled Plastic
I now contract to a company that custom compounds PTFE filled POM.
Regards
Pat
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RE: PTFE Filled Plastic
Well, there IS a difference between "Virgin PTFE" and "Recycled PTFE" molded/sheet/rod products in the US market. More specifically, there are differences between grades as defined in the old MIL-P-2241, and the current ASTM D3294. Recycled grades, grade "C" per the specs, is (supposedly) re-ground, re-pelletized and re-calendared or compression molded into sheet/rod products. Or maybe it's just filled with random crap on purpose, dunno. Also sometimes called/sold as "mechanical grade", see McMaster-Carr for an example. The lower grade material has lower tensile strength and lower electrical resistivity test limits.
All of which has absolutely no bearing (pun intended) on what Pat has described regarding the teflon used as an anti-friction additive to acetal (POM). Never question a republican.
RE: PTFE Filled Plastic
There is sliding contact that occurs in almost all gear geometries, including standard spur gears.
RE: PTFE Filled Plastic
Available already compounded in polymer from www.multibase.com (Dow Corning)
or
as pellets with silica in them from Wacker under the name Genioplast.
They should work well and be cheaper than PTFE.
Chris DeArmitt PhD FRSC CChem
www.phantomplastics.com
Consultant to the plastics industry
RE: PTFE Filled Plastic
RE: PTFE Filled Plastic
The various grades are based on variation of particle size and fillers or on being a dispersion suitable for impregnating ropes for seals or for non stick coatings or for extrusion then compression for cheap thread seal tape.
PTFE is used in acetal as a non migrating lubricant and silicone oil was added as a migrating lubricant. I have no experience with UHMW silicone.
I agree that all gears have some sliding action and friction modifiers are sometimes used to improve their performance. The normal combination is Acetal with PTFE and silicone oil matched to nylon 6.6 with graphite and molybdenum disulphide. PET with silicone and or PTFE or moly can be used also matched against either of the above.
Regards
Pat
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RE: PTFE Filled Plastic
Chris DeArmitt PhD FRSC CChem
www.phantomplastics.com
Consultant to the plastics industry
RE: PTFE Filled Plastic
Yes... I've seen this before... many times as I have spent soem time in the custom compounding industry.
Cheers
RE: PTFE Filled Plastic
Bryan Gebhart
Phoenix Recycling Inc.
www.plasticscrap.us