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View Full Version : Delrin - Does the color mean anything?



JimH
03-07-2005, 02:00 PM
I have been looking at getting some DELRIN. I find white and black mostly, and occassionally find green or blue. I have done a search, but cannot find any mention of color differences and if any effect on properties.

Can someone provide an Internet pointer (or an answer)?
Thanks,
Jim

Bruce Griffing
03-07-2005, 02:14 PM
No difference in my experience - but I have not pushed the material very hard either.

bernie l
03-07-2005, 02:15 PM
Jim-
You can check out McMaster-Carr, search for acetal, (Delrin is the trade name for Duponts acetal). They have a little explanation about different types and what colors they might be. I've personally not seen anything other than white or black but apparently they exist. Acetal is like most other plastics, it could be any color the manufacturer wanted to make it.

take care
Bernie

ERBenoit
03-07-2005, 02:23 PM
Delrin is Dupont's trade name for acetal. I use a bit of it at work, mostly black. I have seen blue but never green. There is brown which is PTFE impregnated for reduced friction.

May find some help here:

http://www.matweb.com/reference/acetal-polymer.asp

[This message has been edited by ERBenoit (edited 03-07-2005).]

precisionworks
03-07-2005, 02:29 PM
DuPont makes two or three dozen grades of Delrin for specific applications:
http://plastics.dupont.com/NASApp/myplastics/Mediator?id=30&locale=en_US

madman
03-07-2005, 02:30 PM
I call the black nylatron the black can be a graphite impregnation to give lubricating properties to the material. Thats what I was told by the sales dude at the plastics shop.

cliff69
03-07-2005, 02:32 PM
My plastic supplier says the black is "high lubricity" and the white is "natural" YMMV

Evan
03-07-2005, 03:25 PM
Wait a minute madman. Don't confuse Delrin with Nylatron. They aren't related. Nylatron is often called black nylon even though it isn't black at all but is grey. It is nylon with molybdenum disulphide filler to increase lubricity. There is also available graphite filled nylon which is slightly darker than nylatron but still not black. It has a bit of a swirl pattern to it as well.

You can also get Delrin filled with 20% Teflon fibers for increase lubricity and wear resistance. Delrin is also available in 20% glass filled which gives it high stiffness, low warpage, and low creep.

nheng
03-07-2005, 04:06 PM
Colored Delrin, such as blue, can be very difficult to get and you might need to buy a boatload to have it extruded if you have to repeat parts in that color. Den

DR
03-07-2005, 05:25 PM
Over the years I've CNC machined thousands of pounds of customer supplied acetal.

In my experience the natural is not as good a machining type as the black, black seems to chip break easier. My amateur analysis is the black pigment must be a lubricant (graphite?). The local distributor disagrees with my theory about black being better to machine, he says there's absolutely no difference.

Another issue is the hardness/brittleness of the material. Some bars with have marking indicating the material is annealed, others have no such markings. I have seen some that's very brittle (not annealed??). IMO, this brittleness that shows up once in a while makes Delrin a bad choice for impact devices like hammer heads, etc.

JimH
03-07-2005, 06:18 PM
First, thanks for all the responses.

I have looked at the supplied URLs (including McMaster-Carr) and still don't find anything other than white (normal DELRIN), black (enhanced UV resistance DELRIN), and brown (PFTE added DELRIN). The blue and green are offerings on eBay, with no proof of it being DELRIN. I have requested a product spec sheet, but received no response. I'll just pass on these as the intended use is for a distributor cap or two for some small engines I'm building.

Again, thanks,
Jim

Paul Alciatore
03-07-2005, 06:51 PM
Color can mean a lot. Got some terminal boards once that gave fits with audio cross talk. They were black and partially conductive. Probably graphite. The manufacturer forgot to specify the electrical conductance - or lack thereof. Someone in purchasing thought they would get ahead by finding a cheaper grade. Yea... Saved a lot of money...... He probably made VP. They promote for stuff like that, you know.

Paul A.

roninB4
03-07-2005, 08:21 PM
I don't mean to hijack this thread but I have a question regarding acetal. At another board it was flatly stated that acetal is unsuitable for exterior automotive suspension bushings as acetal absorbs water. I'm assuming that this would lead to aggravated oxydation of steel components in contact with the plastic. I looked around the website at DuPont, although not thoroughly, and found no mention of this. Any of you care to comment on this as this is news to me. I use acetal in automotive/motorcycle applications sometimes and wondered if I've been introducing a potential problem. The source that flatly stated the absorbtion did have a "solution" in the form of an unamed plastic they sell so this may have been the case of "selling the problem". Thought I would ask some more knowledgeable folks here about this. Many thanks for your replies.

[This message has been edited by roninB4 (edited 03-07-2005).]

wierdscience
03-07-2005, 08:27 PM
The difference is lamp black,that's what the Cadillac plastics sales rep told me.

The blue/green could be to indicate origin.We used to get nyloc nuts for a Navy contract.Only the American made nuts had colored nylon,all the rest where off white/ivory colored.Made it easy to tell when somebody was cheating.

Evan
03-07-2005, 08:31 PM
One of the advantages of acetal is that it DOESN'T absorb water much.

spope14
03-07-2005, 08:43 PM
Black Delrin does chip better, and hold size and such better.

precisionworks
03-07-2005, 08:51 PM
Here's a list of the OEM approved grades of Delrin (only pages 4 - 10 are for Delrin). Looks like every major automotive manufacturer uses it.

http://plastics.dupont.com/plastics/pdflit/americas/general/americascertspec.pdf

[This message has been edited by precisionworks (edited 03-07-2005).]

JimH
03-08-2005, 09:28 AM
Finally got a reply on the blue DELRIN. It was a special order color from Dupont and is DELRIN, nothing else was added or changed. Same with the green.
Jim

psomero
03-08-2005, 10:20 AM
ummmm, rit dye anyone?

i've seen plenty of delrin dyed with RIT...

nheng
03-08-2005, 04:40 PM
I've dyed lots of nylon with food coloring and vinegar but didn't know acetal could be. What's your recipe? Den

bernie l
03-08-2005, 06:35 PM
Jim-
Most thermoplastics are easy to color during compounding. In some cases the color is strictly cosmetic, in other cases it may indicate a particular property. Uncolored acetal is sort of translucent white, you can't see through it, but light will transmit through. Most of what I've seen used for machining is colored white, light will not transmit through it unless extremely bright. Plastics that colored black are usually done so to provide a degree of protection against UV rays. (Black plastics can also be cheaper to make if recycling, you can color any junk black). Brown acetal is likely acetal combined with a little PTFE (Teflon) to improve wear resistance and decrease friction. Acetal copolymer is available in white or black, useful for applications that require meeting FDA or USDA requirements. This copolymer is available non-conductive like most plastics or conductive for applications where you might want to dissipate static. Acetal with glass fill is also available for improved resistance to temperature extremes.

With regards to using acetal for applications that get wet, this is something that is pretty common, and acetal will probably absorb some moisture, but it is far superior to most grades of nylon, I would not recommend nylon for a outdoor or wet environment. In fact nylon absorbs moisture out of the air (I think the term is hydroscopic) and has to be dried before in can be injection molded. Keep in mind that vehicle manufacturers that purchase hundreds of thousands of plastic components specify the exact grade of plastic that is to be used. For a resin like acetal there are hundreds of different grades for different applications.

Regarding the brittleness of black acetal, acetal is a thermoplastic, that means you can remelt it and form it or mold it into something else. Companies that do injection molding take defective molded parts, grind them up and feed them back into the molding process. This is commonly accepted practice and works okay as long as the percentage of recycle resin stays pretty low. Too much regrind and acetal tends to get brittle.

Acetal is pretty easy to machine, sometimes I'll even use router bits, the sharper the better. However it will burn and when it does it stinks and burns your eyes, also the gas it gives off is toxic, so it's best not to burn it. (that is a pretty easy way to identify acetal though, take shaving and burn it, once you've smelled it you'll remember.)

Hope this helps, (sorry I was so long winded)

Take care
Bernie

[This message has been edited by bernie l (edited 03-08-2005).]

quasi
03-08-2005, 08:15 PM
Lee Valley sells some small siZes of uhmw plastic, I can't remember for sure but I think they have small pieces of Delron also.

psomero
03-08-2005, 09:53 PM
<font face="Verdana, Arial" size="2">Originally posted by nheng:
I've dyed lots of nylon with food coloring and vinegar but didn't know acetal could be. What's your recipe? Den</font>

never done it myself, but it runs along the lines of boil a pot of RIT big enough to fit your parts and dump 'em in i think...


not much more help, but here's a pic:

http://www.icdownersgroup.com/images-upgrades/upgrades-wetworxbolts.jpg

they're delrin paintball bolts...

[This message has been edited by psomero (edited 03-08-2005).]

roninB4
03-09-2005, 07:41 PM
Evan
Precisionworks

Thanks for the replies, thought the "absorbtion" was BS and it has now been confirmed.