Delrin vs. PEEK Datasheet

[rsterne]

Here is a comparison between the two materials....

http://www.makeitfrom.com/compare-materials/?A=Acetal-Homopolymer-POM-H-Delrin&B=Polyetheretherketone-PEEK

I don't know which of those are the most important for our purposes, but certainly the Tensile Strength would be a major consideration....

Delrin: 65 MPa = 9400 psi
PEEK: 100-230 MPa = 14,500-33,300 psi

Bob

[PakProtector]

Young's Modulus is another important one, this determines how far it gets squished and thus, opening energy to get it off its seat.
cheers,
Douglas

[SeanMP]

Also the Delrin that is commonly in use is copolymer which has even lower values

[rsterne]

Ask and ye shall receive.... Delrin Copolymer vs PEEK

http://www.makeitfrom.com/compare-materials/?A=Acetal-Copolymer-POM-C&B=polyetheretherketone-peek

Bob

[lloyd-ss]

Bob,
Thanks for posting this info.  I have been using glass filled Delrin with good results for a lot of things.  Could you do the compare for that one too?
Thanks,
Lloyd

[rsterne]

I had no idea that website had so many choices, but I tried and this is what I got....

http://www.makeitfrom.com/compare-materials/?A=30-Percent-Glass-Fiber-30-GF-Acetal-Copolymer-POM-C&B=polyetheretherketone-peek

Certainly a huge improvement over the pure co-polymer.... however, you can also get glass filled PEEK....

http://www.makeitfrom.com/compare-materials/?A=30-Percent-Glass-Fiber-30-GF-Acetal-Copolymer-POM-C&B=30-percent-glass-fiber-30-gf-peek

Bob

[rsterne]

Apparently the darker green areas on the bar charts are for the glass-filled Delrin.... Here is a comparison....

http://www.makeitfrom.com/compare-materials/?A=30-percent-glass-fiber-30-gf-acetal-copolymer-pom-c&B=Acetal-Copolymer-POM-C

and the same for PEEK and glass-filled PEEK....

http://www.makeitfrom.com/compare-materials/?A=30-Percent-Glass-Fiber-30-GF-PEEK&B=polyetheretherketone-peek

It looks like there is even a better filler available for PEEK, but I can't imagine the cost.... *LOL*....

Bob

[rsterne]

Found it.... Carbon Fiber filled PEEK.... *LOL*....

http://www.makeitfrom.com/compare-materials/?A=30-Percent-Carbon-Fiber-30-CF-PEEK&B=polyetheretherketone-peek

and then to put it into perpesctive, CF filled PEEK vs. 6061-T6 aluminum....

http://www.makeitfrom.com/compare-materials/?A=30-percent-carbon-fiber-30-cf-peek&B=6061-T6-Aluminum

Bob

[lloyd-ss]

Havin' fun are we Bob? LOL
You get into something like this and its hard to stop.  The dark green areas in the bars seem to show where the value of a particular property covers a range, rather than a single specific value. (Which would be much easier to compare  )

The glass in the PEEK and Delrin seems to be a pretty good equalizer for some of the properties, almost like the glass is more important than the parent material.

Thanks for adding the aluminum comparison.  Most folks are using the PEEK for valve heads only, is that correct?  Then as Doug said, Youngs Modulus is an important consideration in how much compression the head takes against the seat, and also how much force is needed to conform to irregularities in the seat.
Aluminum is 69 GPa, Glass filled Delrin is 9.7, Peek is 4 to 24, but glass filled Peek is 10, and 6/6 nylon is less than 3.5,UHMW is less than 1
Aluminum is too hard/stiff, and UHMW is too soft, and what is inbetween covers a very broad range. And the actual material hardnesses, which must be important  too, I would think, are all given in different scales so they are almost impossible to compare.  Darn this is really confusing     .  Where is a materials science expert when you need one?

I am just glad folks are giving feedback about what they have used that worked or didn't work.
Thanks,
Lloyd

[rsterne]

All I know is that I love that PEEK we got.... Interestingly, the efficiency seems to be increasing with it as well.... but then I've never used glass-filled Delrin.... I think possibly the harder materials, being easier to knock off the seat, open faster because the hammer has lost less velocity in cracking the valve.... Faster opening means a "squarer" lift/dwell curve with a faster rise time.... Something to think about....

Bob

[lloyd-ss]

OK, you talked me into it with the efficiency teaser.  I will order some PEEK for the next project, but should I go all the way for the glass filled?
  It looks awfully expensive from McMaster.  Maybe there is a less expensive source?

[SeanMP]

Lloyd

I got ours from Plastics International.
http://www.plasticsintl.com

Bob is not talking about tiny efficiency improvements either....I almost fell on my face this morning while I was testing my new valve.

I certainly need to do more testing before I start frothing online

[sixshootertexan]

Would the PEEK be to hard for a 1400psi regged gun or should I use delrin?

[SeanMP]

My initial feeling is that 1400 would be too low to guarantee a seal. I used it at 1500psi and it worked but the seal was quirky. And that was a monster valve so even at that pressure the force was fairly high. PEEK seems to be excelling in applications where the material strength of Delrin is marginal or below.

[lloyd-ss]

My initial feeling is that 1400 would be too low to guarantee a seal. I used it at 1500psi and it worked but the seal was quirky. And that was a monster valve so even at that pressure the force was fairly high. PEEK seems to be excelling in applications where the material strength of Delrin is marginal or below.

Sean,
OK, this is starting to make more sense now, and I have an application where the Delrin might be getting overloaded, and I haven't even done testing at full pressure. I will order the PEEK.
Thanks,
Lloyd

[lloyd-ss]

Just to confuse the issue, I am switching over to Sean's thread about testing the PEEK (in this same gate) , because of the pictures it has, and how this might be headed with big cal valves.
Lloyd

[Motorhead]

Tad late ... but to this question ... using a PEEK poppet in my regulated .177 m-rod and it is sealing fine at 1800#
Listening to it leak as a slow fill was done ... it stopped @ 800# give or take.
I had electric drill spun the poppet onto the seat both directions for a few moments in hoping a semi-lap in would happen.

 

Would the PEEK be to hard for a 1400psi regged gun or should I use delrin?

[PakProtector]

I have PEEK heads, 0.340" on 0.281 throats and I think that seat is a bit on the wide side. Am going to try a .290 throat at some point...this on modified, .2263 marauder valves. I have had slight leakage up to 2k psi, and found it to stop with a single firing cycle that allows the dead to sit where it wants to. No deformation noted when used on higher power tunes either( I run 2k1-1k6 psi for pellets, and 3k-2k3 for the heavier boolits )....and with different hammer springs too.
cheers,
Douglas

[SeanMP]

Douglas
Those seats are really really big. You may be losing some efficiency there. And most certainly losing flow at low lift.
 
I'm providing for a maximum possible seat of about .012" and after use I find that that contact area is half that at 3500psi

A little means a lot as you can see in this image of your valve to scale, at 0.025 lift, with flow vectors applied.

[Motorhead]

Great drawing Sean ...

Not knowing if I could get away with less sealing margin ?
Set up my guns PEEK seat up as follows, .250" throat, full diameter .125" stem and a poppet diameter of .320"
which give a sealing margin of @ .035" tho likely closer to .025" once taken into account the small bevel on edge of throat to ease flow around the corner.