ShamrockPAPM
Materials
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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PTFE Filled Plastic 4
- Thread starter ShamrockPAPM
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There is only one type of PTFE. It is used as a adjunct in many base polymers.
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...)
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...)
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- #3
The PTFE could vary in particle size but to be honest, PTFE is so non-reactive (inert) that my guess is you'll be fine with the recycled stuff and put the saved pennies in the piggy bank. There are places for PTFE cheaper than DuPont. I just saw an Irish company at the NPE / Antec in Chicago specializing in cost-effective PTFE particles. They're called Shamrock:
Chris DeArmitt PhD FRSC CChem
Consultant to the plastics industry
Chris DeArmitt PhD FRSC CChem
Consultant to the plastics industry
BTW, I didn't miss the irony that your handle here is Shamrock too. This company should suit you well!
Chris DeArmitt PhD FRSC CChem
Consultant to the plastics industry
Chris DeArmitt PhD FRSC CChem
Consultant to the plastics industry
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
Hi Harry,
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
Consultant to the plastics industry
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
Consultant to the plastics industry
Hi Chris,
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])
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])
Lol, their stuff is too expensive to compete for virtually any application although I did make one new grade that is great as a lubricant.
Chris DeArmitt PhD FRSC CChem
Consultant to the plastics industry
Chris DeArmitt PhD FRSC CChem
Consultant to the plastics industry
By the way Harry. I am thinking of adding some links to my website. They would be to people and companies that I can wholeheartedly endorse. That would include you. Do you mind?
Chris DeArmitt PhD FRSC CChem
Consultant to the plastics industry
Chris DeArmitt PhD FRSC CChem
Consultant to the plastics industry
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patprimmer
New member
The PTFE used to fill POM is usually a friable particle. That is normally achieved by bombarding with gamma rays at the production facility for the PTFE.
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
See FAQ731-376 for tips on use of eng-tips by professional engineers &
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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
See FAQ731-376 for tips on use of eng-tips by professional engineers &
for site rules
- Thread starter
- #11
ShamrockPAPM
Materials
Chris you nailed it right on the head. This is a formulation I am looking to change from Dupont to Shamrock, the whole purpose I opened the account was to get feedback as this is quite a large project. I am going to be saving about $1/lb using the Shamrock product.
Does anyone have any experience using it in acetal?
Does anyone have any experience using it in acetal?
The Publican, font of all knowledge and beer has spoken.
Chris DeArmitt PhD FRSC CChem
Consultant to the plastics industry
Chris DeArmitt PhD FRSC CChem
Consultant to the plastics industry
patprimmer
New member
I have sold it to a number of people over the years. Grades were Duracon YF10 and YF20 from memory.
I now contract to a company that custom compounds PTFE filled POM.
Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers &
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I now contract to a company that custom compounds PTFE filled POM.
Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers &
for site rules
btrueblood
Mechanical
"What is the difference between a recycled PTFE and PTFE from Dupont? "
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.
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.
Compositepro
Chemical
Obviously there is a large variety of grades of PTFE available. High molecular weights have the higher mechanical properties. Recycling results in a reduction in molecular weights. The lubricating grades are lower in molecular weight I think DuPont's lubricating grades are called Zonyl. Irradiation is one method used to break down polymers to reduce molecular weight.
There is sliding contact that occurs in almost all gear geometries, including standard spur gears.
There is sliding contact that occurs in almost all gear geometries, including standard spur gears.
If you are looking for lubricants that don't migrate then also consider ultra high molecular weight silicone.
Available already compounded in polymer from (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
Consultant to the plastics industry
Available already compounded in polymer from (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
Consultant to the plastics industry
- Thread starter
- #17
ShamrockPAPM
Materials
I am looking at just below $4/lb for the PTFE what do the UHMW Silicone powders usually go for?
patprimmer
New member
MW is generally not a consideration with PTFE. It only comes with a MW so high that it has an MFI of virtually zero and for that reason it is compression moulded then sintered and not injection moulded in the normal way.
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
See FAQ731-376 for tips on use of eng-tips by professional engineers &
for site rules
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
See FAQ731-376 for tips on use of eng-tips by professional engineers &
for site rules
A ball park price for UHMW silicone from Wacker is $5-6/lb and that's not 100% active. It's mixed with silica.
Chris DeArmitt PhD FRSC CChem
Consultant to the plastics industry
Chris DeArmitt PhD FRSC CChem
Consultant to the plastics industry
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- #20
My may concern would be the by products that come from the recycling of PTFE (HF which can degrade the polymer), consistancy of particle size (critical for wear and friction), and aglomeration that can occur during compounding... all of which impact the final part performance in strength, impact, fatigue and wear/friction.
Yes... I've seen this before... many times as I have spent soem time in the custom compounding industry.
Cheers
Yes... I've seen this before... many times as I have spent soem time in the custom compounding industry.
Cheers
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