Howto determine the difference between ABS, PBT and POM

[ripster]

Salty Water test?

Is that like the Muddy Waters test? Let's get my MOJO working!

How much salt do you use? And IIRC many plastics have widely varying specific gravity based on injection of air and additives. Like titanium dioxide for these new low wavelength lasered Filco Camo keys.

I still like my acetone or the hammer test.
http://geekhack.org/showthread.php?2972 ... is-Made-Of

Sorry for borked attachment pics. I'd fix if I could get access.

[Mrinterface]

I just use a longdrink glass with lukewarm water and some salt.

The difference between ABS and PBT is really very clear, the PBT sinks to the bottom almost immediately. The ABS floats on top are hovers somewhere in the middle.

It's a pitty POM behaves the same as PBT. My 'pincer-tests' showed that ABS dents more than shatters. PBT and POM shatter. So now I don't have any test to show the difference between PBT and POM.

EDIT : I made vids of me testing all the different keycap material. I even tried the hammertest, but those tests basically failed since I used too much force and the caps just shattered regardless of material. So I redid the tests with a pincer and then it clearly showed the denty behavior of ABS compared to PBT/POM.
All those vids will be viewable soon on my new and improved mrinterface.com

[ripster]

Boil them.

I'm serious!

The POM I had turned weird on the edges.



So is the salt even necessary?

[Mrinterface]

I redid the test with water straight from the tap ( cold ) and NO salt. Results are the same. PBT rushed towards the bottom and ABS hovers.....

ABS floating, PBT bottom

abs_pbt.jpg (189.78 KiB) Viewed 32116 times

[Mrinterface]

Boil them.
I'm serious!
The POM I had turned weird on the edges.

Gonna try that..

[ripster]

You must have hard water in Nederlands! West Coast U.S.A. We drink the pure mountain reservoir stuff!

I'll take a pic but half of my Signature Plastic Doubleshot keys slooowly floated to the bottom!

[Mrinterface]

You must have hard water in Nederlands!

I'll take a pic but half of my Signature Plastic Doubleshot keys slooowly floated to the bottom!

Yes, that's the thing. ABS can even end up on the bottom. The trick is to measure the speed
. PBT and POM will rush towards the bottom, ABS will not. ABS sometimes reaches the bottom but it will take a while.....

[ripster]

I'll do some salt tests, take some pics, and write this all up here somewhere.

Air bubbles in the stem seem to be the determining variable in my almost distilled tap water.

[Mrinterface]

We might want to move parts of this thread to the workshop area

EDIT : I just did....

[ripster]

Will do!

Hah, the clickclacks and ABS ALPs,drops like a rock in my water.

You get well or reservoir water?

Nvm... Will move to other post...

[ripster]

<moved>

[ripster]

OK, HERE is where things get interesting.

SOME SP Doubleshots sink and some don't.

OK, it's GUESSING TIME!

Anybody know why?

DSC_3818.jpg (776.69 KiB) Viewed 32065 times

In fact some ABS keys sink like a ROCK in my water.

DSC_3820.jpg (732.2 KiB) Viewed 32065 times

[Mrinterface]

Give those top floating ones a little push down.....

Did the bottom ones sink like a brick?

Did you add salt?

[itlnstln]

Your water has impurities like limestone?

The SP doubleshots should float, right?

[ripster]

ALL the SP doubleshots SHOULD float, yes. That's my point. It's an OK test but needs KEYBOARD SCIENCE to be a perfect test.

I think my water is better than Mrinterface's water. Mine is practically distilled water.

I will go shaking some salt now.

[itlnstln]

There could be small gaps between the shots of plastic that might cause the plastic to sink, but I'm just kinda shooting in the dark now.

[ripster]

Sure are.

Actually the GAPS is key to this clue. I got MOST of them to sink to the bottom eventually.

GUESS HOW!

[itlnstln]

Soap.

[ripster]

You know I might try some of that dishwasher stuff but I'll take a pic showing what I did.

Clue: It's in the Sundries Aisle next to Straws usually. Might be a GAP.

Another Clue: Notice how WELL the Lego Man floats.

100% Unadulterated ABS.

http://messageboards.lego.com/en-US/sho ... ID=1822888

Also, you might be interested to know that, because safety is of utmost importance to The LEGO Group, most LEGO elements are made of ABS (Acrylonitrile Butadiene Styrene), the highest quality plastic available that meets and often exceeds an extensive list of safety and quality specifications. Our continuing commitment and efforts to make our products safe and fun for children is inside every toy we produce. Working together with caring parents like yourself, our shared reward is the unlimited hours of safe and happy playtime children enjoy.

[ripster]

Isn't this guessing thing annoying.

It's like one of HaaTa's vintage keyboards.

[Maarten]

Wanna know what kind of plastic it is? Burn em and feel like a real MAN!!

http://www.boedeker.com/burntest.htm

[ripster]

Are you saying Julia Child is not a real man!

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Boscom-On-Fire.gif (879.13 KiB) Viewed 32021 times

ABS IS sooty.

Didn't try PBT.

[kint]

The Lego man has nothing but air in head and chest that's why he floats.
POM vs PBT: POM is slick. Cherry POM tends to show the Stem mount on the top of the cap and almost all of the cherry POMs I had have slightly deformed sides (both due to shrinking when cooling?). If a noob like me has no problem distiguishing POM from PBT....

[ripster]

Air IS the issue here.

But where?

Now that POM vs PBT stuff I gotta check out. PBT deforms pretty badly too.

[kint]

my point was: You can't count the LEGO man as a determinant for ABS floating, if you want to do that use a LEGO brick not a figurine that encloses air afair at least in chest and head.
The slippery feel of POM -I think I even got that from your wikis, and as soon as I laid my hands on POM for the first time I knew what was meant, the difference is obvious and its also different from worn ABS and such.
As for the Stems and shrinking, this isn't meant to be a final indicator, but maybe its's a hint, and these are crappy cellphone pics:
Cherry OEM caps here - Raptor K1 on the left vs G80-1502 on the right, both are POM.



Cherry also seems to not mark POM caps on the inside (OEM caps) - this is a PBT only featrure (as for my experience).

[ripster]

PBT keys have those too. I call them PBT dimples.

No guesses why some ABS keys float some don't?

The ones that do and don't are identical.

[itlnstln]

Borax?

[7bit]

PBT keys have those too. I call them PBT dimples.

No guesses why some ABS keys float some don't?

The ones that do and don't are identical.

Maybe the material is sometimes more dense. PBT/ABS or POM does not mean that it is always exactly the same. black keys might be heavier than whites and so on.

You should do excessive research on that for the next months and then report back when you've got a result.

[ripster]

Borax?

Lol.

You Mormon? No, it's toothpicks. I ALSO USED a bottle of the stuff that I SHOULD have used instead of the blue Dawn I put into my dishwasher causing a $79' repair bill solved by pouring 10 buckets of water through it!

I'm saying in the pic one Awesome key floats and the other identical one does not. At least I think they are identical. One may have a fat lip.


Why?



Watch out 7bit, I'm hitting your post count soon!

[7bit]

Borax?

Lol.

You Mormon? No, it's toothpicks. I ALSO USED a bottle of the stuff that I SHOULD have used instead of the blue Dawn I put into my dishwasher causing a $79' repair bill solved by pouring 10 buckets of water through it!

I'm saying in the pic one Awesome key floats and the other identical one does not. At least I think they are identical. One may have a fat lip.


Why?



Watch out 7bit, I'm hitting your post count soon!

You already did!

Maybe I should collect some money to bribe i**v to let you in again, so I can be number 2 of Deskthority, after leaving Sixty behind.

I think the sink/not sing thing is because there are some little air bubbles on some keys, so they don't sink. When cleaning key caps I have this all the time. This should really be researched one day. When you come back, we might call you Dr. Ripster.